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Critical role of glutathione in melatonin enhancement of tumor necrosis factor and ionizing radiation-induced apoptosis in prostate cancer cells in vitro
Abstract
The role of antioxidants in reducing cancer initiation and progression has been highlighted in recent years. Not only antioxidants limit cancer cell growth but also, in some situations, they promote the effectiveness of conventional treatments. Melatonin, an endogenously synthesized antioxidant, reduces cell growth of several tumor types both in vivo and in vitro. Additionally, the indole limits the collateral damage induced by many chemotherapeutic agents. By using a cellular model of human prostate cancer, we studied the ability of melatonin to enhance apoptosis induced by tumor necrosis factor or gamma radiation. It has been reported that melatonin reduces prostate cancer cell growth and, more recently, it promotes cell differentiation. In this work, we also show that melatonin elevates p21 protein levels and increases antioxidant capacity of prostate cancer cells. In addition, melatonin significantly enhances hrTNFalpha induced cell death by decreasing NFkappaB activation. Bcl-2 and survivin down-regulation appears to be associated to apoptosis stimulation under NFkappaB inhibition. On the contrary, melatonin does not promote irradiation-induced cell death due to an increment in intracellular glutathione content. In conclusion, prevention of NFkappaB activation by melatonin enhances the effectiveness of cytokine treatment in prostate cancer cells but it is not sufficient to enhance cell death triggered by other therapies which generate free radicals. A crucial role of glutathione in survival mechanisms of prostate cancer cells should be carefully considered.
... In LNCaP cells, Sainz et al. demonstrated that melatonin induced cell cycle arrest via marked upregulation of p21, a powerful CDK inhibitor [54]. Similarly, Tam et al. demonstrated in 22Rv1 prostate cancer cells that via the MT1, melatonin reduced proliferation through co-activation of parallel PKC and protein kinase A (PKA) cascades that resulted in the upregulation of p27Kip1 [55], another CDK inhibitor with targets such as G1 cyclin E-CDK2 and cyclin D-CDK4/6 [56]. ...
... Further investigations were conducted to evaluate the effect of melatonin on the levels of antioxidant enzymes, and upregulation of CuZnSOD and catalase was noted in western blots [114]. Another study done by Sainz et al. further highlighted the antioxidant property of melatonin by showing reduced levels of DHE fluorescence in LNCap cells after the addition of AAPH to the culture [54]. This effect was less significant with PC-3 cells. ...
... This was not true for PC3 cells, which demonstrated resistance to hrTNFα therapy, both in isolation and in conjunction with adjuvant melatonin. Mechanistically, they demonstrated melatonin inhibited hrTNFα-induced activation of NFκB [54], a transcription factor that may promote prostate cancer viability via upregulation of c-myc, cyclin D1, and IL-6, and more relevantly, activation of anti-apoptotic genes, such as B-cell lymphoma 2 apoptosis regulator (Bcl-2) [119]. This melatonin-induced inhibition was exemplified following a 48-hour LNCaP co-culture with hrTNF-α and melatonin, which demonstrated that melatonin promoted prostate cancer cell apoptosis through reduction of Bcl-2 as well as Survivin levels, two important carcinogenic survival factors. ...
Melatonin is an endogenous indoleamine that has been shown to inhibit tumor growth in laboratory models of prostate cancer. Prostate cancer risk has additionally been associated with exogenous factors that interfere with normal pineal secretory activity, including aging, poor sleep, and artificial light at night. Therefore, we aim to expand on the important epidemiological evidence, and to review how melatonin can impede prostate cancer. More specifically, we describe the currently known mechanisms of melatonin-mediated oncostasis in prostate cancer, including those that relate to the indolamine's ability to modulate metabolic activity, cell cycle progression and proliferation, androgen signaling, angiogenesis, metastasis, immunity and oxidative cell status, apoptosis, genomic stability, neuroendocrine differentiation, and the circadian rhythm. The outlined evidence underscores the need for clinical trials to determine the efficacy of supplemental, adjunct, and adjuvant melatonin therapy for the prevention and treatment of prostate cancer.
... The fact that melatonin presents a potent ant the understanding of melatonin actions in PC. In several studies have been conducted, indicating different concentrations can suppress tumor grow in the G0-G1 phase [287,288] or (ii) the activation by an inhibition of NF-κB and the transcriptional in an MT1-dependent manner [290,291]. ...
... The fact that melatonin presents a potent antigonadotropic effect could shed light on understanding of melatonin actions in PC. In order to gain knowledge of this process, eral studies have been conducted, indicating that the administration of melatonin at ferent concentrations can suppress tumor growth [286] by: (i) inducing cell cycle arrest he G0-G1 phase [287,288] or (ii) the activation of intracellular PKA and PKC followed an inhibition of NF-κB and the transcriptional activation of p21 and p27 [289], partially n MT1-dependent manner [290,291]. Although the aforementioned are the most studied mechanisms, other pathways by ich melatonin may exert a protective effect in prostate cancer have been described. ...
... The fact that melatonin presents a potent antigonadotropic effect could shed light on the understanding of melatonin actions in PC. In order to gain knowledge of this process, several studies have been conducted, indicating that the administration of melatonin at different concentrations can suppress tumor growth [286] by: (i) inducing cell cycle arrest in the G0-G1 phase [287,288] or (ii) the activation of intracellular PKA and PKC followed by an inhibition of NF-κB and the transcriptional activation of p21 and p27 [289], partially in an MT1-dependent manner [290,291]. ...
Melatonin is one of the most phylogenetically conserved signals in biology. Although its original function was probably related to its antioxidant capacity, this indoleamine has been “adopted” by multicellular organisms as the “darkness signal” when secreted in a circadian manner and is acutely suppressed by light at night by the pineal gland. However, melatonin is also produced by other tissues, which constitute its extrapineal sources. Apart from its undisputed chronobiotic function, melatonin exerts antioxidant, immunomodulatory, pro-apoptotic, antiproliferative, and anti-angiogenic effects, with all these properties making it a powerful antitumor agent. Indeed, this activity has been demonstrated to be mediated by interfering with various cancer hallmarks, and different epidemiological studies have also linked light at night (melatonin suppression) with a higher incidence of different types of cancer. In 2007, the World Health Organization classified night shift work as a probable carcinogen due to circadian disruption, where melatonin plays a central role. Our aim is to review, from a global perspective, the role of melatonin both from pineal and extrapineal origin, as well as their possible interplay, as an intrinsic factor in the incidence, development, and progression of cancer. Particular emphasis will be placed not only on those mechanisms related to melatonin’s antioxidant nature but also on the recently described novel roles of melatonin in microbiota and epigenetic regulation.
... The existence of putative nuclear melatonin receptors from the ROR/RZR family has been repeatedly proposed (Becker-Andre et al., 1994;Steinhilber et al., 1997;Smirnov, 2001), but their role in melatonin's biological activity is still poorly characterized. At higher concentrations (micro-and millimolar), melatonin inhibits the Ca2þ-Calmodulin complex (Benitez-King et al., 1996;Ouyang and Vogel, 1998), inhibits NFkB (Gilad et al., 1998;Martin et al., 2006), scavenges free radicals (Herrera et al., 2001Rodriguez et al., 2004;Tan et al., 2002), and increases glutathione levels and the activity or expression of several antioxidant enzymes Mayo et al., 2002;Rodriguez et al., 2004;Sainz et al., 2008), among other possible mediators. Antioxidant, oncostatic, oncolytic and cytoprotective effects of melatonin are most often observed at micro-and millimolar concentrations of the indole (Cabrera et al., 2010;Herrera et al., 2001Herrera et al., , 2007Liu et al., 2013;Martin et al., 2014;Ordonez et al., 2015;Sainz et al., 2005;Sanchez-Sanchez et al., 2015;Tan et al., 2003). ...
... Fig. 4). Melatonin and parthenolide, but not W7, increased GSH levels (Fig. 5E) and decreased the production of reactive oxygen species in HT22 cells (Fig. 5F), which have been repeatedly associated to the neuroprotective and antiproliferative properties of the indole Martin et al., 2006;Sainz et al., 2008). These results were confirmed with a second NFkB inhibitor, caffeic acid, in HT22 and sw-1353 cells (Fig. 6). ...
... In the present work we explored the grounds for a putative common antioxidant mechanism underlying both neuroprotective and antiproliferative properties of melatonin. We and others have observed that micro-to millimolar concentrations melatonin induce an increase in GSH levels and a decrease in ROS in several cells and models Martin et al., 2002Martin et al., , 2006Sainz et al., 2008). This antioxidant effect is usually concomitant to both neuroprotection and inhibition of cell proliferation. ...
Melatonin (N-acetyl-5-methoxytryptamine) is a highly pleiotropic hormone with antioxidant, antiproliferative, oncolytic and neuroprotective properties. Here, we present evidence that the N-acetyl side chain plays a key role in melatonin's antiproliferative effect in HT22 and sw-1353 cells, but it does so at the expense of antioxidant and neuroprotective properties. Removal of the N-acetyl group enhances the antioxidant and neuroprotective properties of the indole, but it can lead to toxic methamphetamine-like effects in several cell lines. Inhibition of NFkB mimicked melatonin's antiproliferative and antioxidant effects, but not neuroprotection. Our results strongly suggest that neuroprotective and antiproliferative effects of melatonin rely on different parts of the molecule and are likely mediated by different mechanisms. We also predict that melatonin metabolism by target cells could determine whether melatonin inhibits cell proliferation, prevents toxicity or induces cell death (e.g. apoptosis or autophagy). These observations could have important implications for the rational use of melatonin in personalized medicine.
... Sainz et al. revealed that co-treatment of androgen-insensitive PrCa cell line (i.e. PC3) with Melatonin and IR has no signi cant effect on the induction of radiation-induced apoptosis [20]. Also, in our study, we showed that co-treatment of androgen-sensitive PrCa cell line (i.e., LNCaP) by Melatonin and IR has no signi cant effect on the enhancement of radiation-induced apoptosis, and this study, similar to other previous studies, did not show any antagonist effect on the enhancement of radiation-induced apoptosis on PrCa cells' viability after RT. ...
... Therefore, the strategy of targeting the Bcl-2 molecular pathway, which correlates to PrCa radiation resistance, may translate into higher e cacy of RT. Whereas Bcl-2 has a critical role in radiationresistance of LNCaP cells, and numerous studies have shown that Apigenin and Melatonin distinctly can inhibit Bcl-2 expression and increase Bax expression [13,18,20,25,26]. We aimed to investigate the effect of co-treatment of PrCa with Apigenin and Melatonin before irradiation of Bcl-2, and Bax gene expression. ...
Background: Radiotherapy is a common modality in prostate cancer (PrCa), with a dose of 80Gy. A higher dose of ionizing radiation is often needed to achieve an appropriate response; however, clinical evidence indicates that increasing the dose may lead to side effects. Therefore, finding a substance that sensitizes PrCa to ionizing radiation improves radiotherapy’s therapeutic efficacy. Thus, we aimed to assess the radiosensitization effect of Apigenin-Melatonin on Lymph Node Carcinoma of the Prostate (LNCaP).
Method: The effect of Apigenin, Melatonin, and ionizing radiation, alone and together, on the cells' viability plus the apoptosis induction, were tested by MTT assay, Annexin V, and PI. In addition, Bax and Bcl-2 genes expression was assessed by real-time PCR.
Results: LNCaP co-treatment by Apigenin and Melatonin inhibited PrCa cells' viability synergically. Also, LNCaP co-treatment with Apigenin and Melatonin, 2h before radiotherapy, significantly reduced the LNCaP cells' viability compared to the cells co-treated by Apigenin and Melatonin. Also, LNCaP co-treatment with Apigenin, Melatonin, and ionizing radiation significantly increased early apoptosis by decreasing Bcl-2 gene expression and increasing Bax gene expression.
Discussion: Our results revealed that Apigenin-Melatonin reduces LNCaP cells' viability. Plus, Apigenin-Melatonin could overcome the radioresistance of the LNCaP cells, enhancing radiation-induced apoptosis.
... [66][67][68][69] Intriguingly, certain nutraceuticals that have shown potential for prostate cancer control in cell cultures or xenograft models-such as polyphenols derived from pomegranate, grape seed, or green tea, the crucifera-derived compound diindolylmethane, and the hormone melatoninhave been found to blunt NF-κB activation in prostate cancer cell lines, either in vitro or in vivo. [70][71][72][73][74][75][76][77][78][79][80][81][82] It would be of interest to define the mechanisms responsible for such inhibition. In addition, feasible clinical concentrations of the drug salicylate are known to suppress NF-κB activation, reflecting a direct inhibitory interaction with IKK-β. ...
... In addition, feasible clinical concentrations of the drug salicylate are known to suppress NF-κB activation, reflecting a direct inhibitory interaction with IKK-β. [82][83][84][85][86] The phycocyanobilin in spirulina has the potential to blunt oxidative stress-mediated upregulation of NF-κB activity via inhibition of NADPH oxidase complexes. 87,88 Correction of poor selenium status with supplemental selenium, by optimizing glutathione peroxide activity and hence aiding control of hydrogen peroxide, could be expected to provide a similar benefit. ...
... The changing melatonin rhythm controls seasonal reproduction in photoperiodic animals through activation of receptors within the hypothalamic-pituitary reproductive axis [6,7]. Melatonin exerts anticancer effects on different kinds of tumors [3,8,9], and it also is a broad spectrum antioxidant [10] and free radical scavenger [11][12][13]. Melatonin interacts with estrogen-signaling pathways through indirect neuroendocrine mechanisms, direct actions at the tumor cell level, and regulation of enzymes involved in the biosynthesis of estrogens [3,14]. ...
... In this study, we found that melatonin-induced CaBP-9k expression partially protects against H 2 O 2 -induced cell death by in rat pituitary GH3 cells. Functionally, CaBP-9k is involved in intestinal calcium absorption and is regulated at the transcriptional and post-transcriptional levels by 1,25dihydroxyvitamin D3, the hormonal form of vitamin D [9]. CaBP-9k mRNA and protein levels induced by environmental disruptors are considered to be very useful tools for screening environmental estrogenic compounds in the immature rat model [16,19,20]. ...
Estrogen receptor (ER) is a group of receptors and is activated by the hormone 17β-estradiol (estrogen). There are two different forms of the ER, called as α and β. Both ERs are widely expressed in different tissue types. The ERα is found in endometrium, breast cancer cells, ovarian stroma cells, and in the hypothalamus. The expression of the ER β protein has been studied in kidney, brain, bone, heart, lungs, intestinal mucosa, prostate, and endothelial cells. Calbindin-D9k (CaBP-9k) is a 9 kDa polypeptide with two calcium-binding sites in mammalian intestine, placenta, uterus, kidney, pituitary gland and growth cartilage. However, ER and CaBP-9k regulation by endocrine factors, i.e., melatonin, in pituitary gland is not known yet. In this study, we investigated whether ER and CaBP-9k expression are regulated by melatonin in H2O2-induced cell death in rat pituitary GH3 cells. Cell survival increased about 15% in 0.25 mM H2O2 + 1 mM melatonin compared to only H2O2 (0.25, 0.5 mM) and CaBP-9k expressions were augmented by this treatment with H2O2 (0.25 mM) plus melatonin (1 mM). This suggests that the mechanism between the increase of cell survival and melatonin-induced CaBP-9k expression may be involved in cell death by hydrogen peroxide. This result is in agreement with increase of CaBP-9k expression level together with increment of p-ERK and p-Bad (serine 112). Overexpression of CaBP-9k gene caused to increase p-ERK. ERα expression was increased in H2O2 (0.25, 0.5 mM) + 1 mM melatonin compared to only H2O2 (0.25, 0.5 mM), while ERβ expression was not. Also, ERα of nuclear fraction was increased in 0.5 or 1 mM melatonin. These results indicate that melatonin may increase CaBP-9k expression through ERα. Especially, 14-3-3β protein interacts with p53 protein or CaBP-9k, and may correlate with cell proliferation and cell cycle.
(poster)
... As melatonin is a well-known antioxidant and it has been reported that the increment of glutathione (GSH) induced by melatonin is critical in the prevention of LNCaP cells death induced by several stimuli, 31 we assessed whether GSH plays any role in NE-differentiation induced by the indole. As shown in Figure 3, melatonin, as well as androgen withdrawal (csFBS) and db-cAMP, caused an increase in GSH in LNCaP cells ( Figure 3A), and the effect was greatly dose-dependent ( Figure 3B). ...
... 49,50 Here, we provide further insights into the antioxidant-related mechanisms concluding that GSH appears as an essential mediator for acquiring the NE-like phenotype and demonstrating that redox signaling is implicated in the differentiation pathway. The pool of GSH, the major intracellular antioxidant, is usually preserved by melatonin in multiple cells and tissues including prostate, 31 which in turn can modulate multiple cysteine-containing signaling proteins (ie, redox proteins). It is well known that neuronal differentiation of rat PC12 cells is highly dependent on redox regulation by GSH and reactive oxygen species. ...
Epigenetic modifications, including methylation or acetylation as well as posttranscriptional modifications are mechanisms used by eukaryotic cells to increase the genome diversity in terms of differential gene expression and protein diversity. Among these modifying enzymes, sirtuins, a class III histone deacetylase (HDAC) enzymes are of particular importance. Sirtuins regulate the cell cycle, DNA repair, cell survival and apoptosis, thus having important roles in normal and cancer cells. Sirtuins can also regulate metabolic pathways by changing preference for glycolysis under aerobic conditions as well as glutaminolysis. These actions make sirtuins a major target in numerous physiological processes as well as in other contexts such as calorie restriction-induced antiaging, cancer or neurodegenerative disease. Interestingly melatonin, a nighttime-produced indole synthesized by pineal gland and many other organs, have important cytoprotective effects in many tissues including aging, neurodegerative diseases, immunomodulation and cancer. The pleiotropic actions of melatonin in different physiological and pathological conditions indicate that may be basic cellular targetd for the indole. Thus, much research has focused attention on the potential mechanisms of the indole in modulating expression and/or activity of sirtuins. Numerous findings report a rise in activity, especially on SIRT1, in a diversity of cells and animal models after melatonin treatment. This contrasts, however, with data reporting an inhibitory effect of melatonin on this sirtuin in some tumor cells. This review tabulates and discusses the recent findings relating melatonin with sirtuins, particularly SIRT1 and mitochondrial SIRT3, showing the apparent dichotomy with the differential actions documented in normal and in cancer cells. This article is protected by copyright. All rights reserved.
... As melatonin is a well-known antioxidant and it has been reported that the increment of glutathione (GSH) induced by melatonin is critical in the prevention of LNCaP cells death induced by several stimuli, 31 we assessed whether GSH plays any role in NE-differentiation induced by the indole. As shown in Figure 3, melatonin, as well as androgen withdrawal (csFBS) and db-cAMP, caused an increase in GSH in LNCaP cells ( Figure 3A), and the effect was greatly dose-dependent ( Figure 3B). ...
... 49,50 Here, we provide further insights into the antioxidant-related mechanisms concluding that GSH appears as an essential mediator for acquiring the NE-like phenotype and demonstrating that redox signaling is implicated in the differentiation pathway. The pool of GSH, the major intracellular antioxidant, is usually preserved by melatonin in multiple cells and tissues including prostate, 31 which in turn can modulate multiple cysteine-containing signaling proteins (ie, redox proteins). It is well known that neuronal differentiation of rat PC12 cells is highly dependent on redox regulation by GSH and reactive oxygen species. ...
Treatment of prostate cancer (PCa), a leading cause of cancer among males lacks successful strategies especially in advanced, hormone-refractory stages. Some clinical studies have shown an increase in neuroendocrine like cells parallel to the tumor progression but their exact role is a matter of debate. The prostate is a well-known target for melatonin, which reduces PCa cells proliferation and induces neuroendocrine differentiation. To evaluate the mechanisms underlying the indole effects on neuroendocrine differentiation and its impact on PCa progression, we used a cell culture model (LNCaP) and a murine model (TRAMP). Persistent ERK1/2 activation was found in both, melatonin and androgen-deprived cells. Melatonin blocked nuclear translocation of androgen receptor (AR), thus confirming anti-androgenic actions of the indole. However, by using a comparative genome microarray to check the differentially expressed genes in control, melatonin or androgen-deprived cells, some differences were found, suggesting a more complex role of the indole. By comparing control cells with those treated with melatonin or depleted of androgen, a cluster of 26 differentially expressed genes (± 2.5-fold) was found. Kallikreins (KLK)2 and KLK3 (PSA) were dramatically downregulated by both treatments whereas IGFBP3 and IGF1R were up- and downregulated, respectively, in both experimental groups, thus showing a role for IGF in both scenarios. Finally, melatonin prolonged the survival of TRAMP mice by 33% when given at the beginning or at advances stages of the tumor. Serum IGFBP3 was significantly elevated by the indole in early stages of the tumor, confirming in vivo the role of the IGF signaling in the oncostatic action of the indole. This article is protected by copyright. All rights reserved.
... The risk factors are associated with aging, ethnical factors, hormone disturbances, dietary components, and family history [86]. There are several molecular targets that have been implicated as survival booster for prostate cancer, such as Bcl-2 and COX-2 overexpression, increased ROS formation, altered androgen receptor signaling, mutation of p53, elevation in expression of inhibitor apoptosis protein (IAP), NFκB, and AP-1 [87,88]. ...
... Generally, patients with prostate cancer exhibit a lower level of melatonin than those agematched controls, and furthermore, melatonin reduces the cell growth of hormone-dependent and -refractory human prostate cancer [89]. A recent study showed that melatonin treatment almost doubles the total GSH content in LNCaP and PC3 in vitro cells [88]. Also, preincubation with melatonin prevented significantly the toxicity by chemotherapeutic agents. ...
Melatonin, an indolamine produced by pineal gland at night, has been implicated in the treatment of many dysfunctions including oxidative disorders, apoptosis, and cancer. It is indisputable that melatonin represents an important molecule used for antioxidant therapies at cellular levels, preventing subsequent changes that results in cell damage. Melatonin is a very potent free radical scavenger, reactive species which can be extremely deleterious to macromolecules into the cells. Direct antioxidant properties of melatonin have been shown both in vitro and in vivo. Alternatively, melatonin also stimulates several antioxidant activities, protecting the cells from oxidative stress. Thus, to focus on the antioxidant effects of melatonin, several experimental and clinical studies have been carried in an attempt to assess the activity of melatonin towards radical-induced damage. The cell oxidation is one of the main causes leading to tumorigenic process. Recently, a wide range of studies has focused attention on the positive correlation between major cell signaling-induced cancer, such as the MAP kinase and PI3K/Akt pathways, and the increasing oxygen/nitrogen species formation. Particularly, melatonin has a dual effect on intracellular redox state regarding its antiproliferative action and its cytotoxic effect directly to cancer cells. As far as we could investigate, there is no compiled data regarding melatonin, oxidative stress and cancer studies which we believe to be extremely important for the hormone divulgation and to encourage further researches. This chapter briefly presents a review of the melatonin metabolism (biosynthesis, distribution, cellular responsiveness, and degradation), followed by an L. G. de Almeida Chuffa, B. A. Fioruci and F. R. Ferreira Seiva 2 introductory topic to the free radicals world, broaching the main mechanisms in which they participate, and their consequences. The next topics include the extensively studied relations between free radicals and cancer development (addressing some specific and aggressive cancer types), focusing on standard and alternative treatment methodologies.
... [66][67][68][69] Intriguingly, certain nutraceuticals that have shown potential for prostate cancer control in cell cultures or xenograft models-such as polyphenols derived from pomegranate, grape seed, or green tea, the crucifera-derived compound diindolylmethane, and the hormone melatoninhave been found to blunt NF-κB activation in prostate cancer cell lines, either in vitro or in vivo. [70][71][72][73][74][75][76][77][78][79][80][81][82] It would be of interest to define the mechanisms responsible for such inhibition. In addition, feasible clinical concentrations of the drug salicylate are known to suppress NF-κB activation, reflecting a direct inhibitory interaction with IKK-β. ...
... In addition, feasible clinical concentrations of the drug salicylate are known to suppress NF-κB activation, reflecting a direct inhibitory interaction with IKK-β. [82][83][84][85][86] The phycocyanobilin in spirulina has the potential to blunt oxidative stress-mediated upregulation of NF-κB activity via inhibition of NADPH oxidase complexes. 87,88 Correction of poor selenium status with supplemental selenium, by optimizing glutathione peroxide activity and hence aiding control of hydrogen peroxide, could be expected to provide a similar benefit. ...
The large majority of clinical prostate cancers remain dependent on androgen receptor (AR) activity for proliferation even as they lose their responsiveness to androgen deprivation or antagonism. AR activity can be maintained in these circumstances by increased AR synthesis-often reflecting increased NF-κB activation; upregulation of signaling pathways that promote AR activity in the absence of androgens; and by emergence of AR mutations or splice variants lacking the ligand-binding domain, which render the AR constitutively active. Drugs targeting the N-terminal transactivating domain of the AR, some of which are now in preclinical development, can be expected to inhibit the activity not only of unmutated ARs but also of the mutant forms and splice variants selected for by androgen deprivation. Concurrent measures that suppress AR synthesis or boost AR turnover could be expected to complement the efficacy of such drugs. A number of nutraceuticals that show efficacy in prostate cancer xenograft models-including polyphenols from pomegranate, grape seed, and green tea, the crucifera metabolite diindolylmethane, and the hormone melatonin-have the potential to suppress AR synthesis via downregulation of NF-κB activity; clinical doses of salicylate may have analogous efficacy. The proteasomal turnover of the AR is abetted by diets with a high ratio of long-chain omega-3 to omega-6 fatty acids, which are beneficial in prostate cancer xenograft models; berberine and sulforaphane, by inhibiting AR's interaction with its chaperone Hsp90, likewise promote AR proteasomal degradation and retard growth of human prostate cancer in nude mice. Hinge region acetylation of the AR is required for optimal transactivational activity, and low micromolar concentrations of the catechin epigallocatechin-3-gallate (EGCG) can inhibit such acetylation-possibly explaining the ability of EGCG administration to suppress androgenic activity and cell proliferation in prostate cancer xenografts. Hence, it is proposed that regimens featuring an N-terminal domain-targeting drug, various nutraceuticals/drugs that downregulate NF-κB activity, and/or supplemental intakes of fish oil, berberine, sulforaphane, and EGCG have potential for blocking proliferation of prostate cancer by targeting its characteristic addiction to androgen receptor activity.
... That targeting antioxidant defense may be a promising approach to the selective killing of cancer cells. Mechanism based on combinations of cancer inhibitors with free-radical-producing agents may have clinical application [114,125]. ...
... Melatonin had been shown previously to reduce proliferation through its antioxidant activity [129], but its role in inducing apoptosis in cancer cells had not been explored at that time. Surprisingly, we found that this molecule was able to reduce proliferation, to inhibit radiation or TNFα-induced NFκB activation, but it was unable to promote apoptosis [125,130]. Moreover, cells treated with melatonin showed a neuroendocrine phenotype similar to other treatments described previously in the literature. ...
Free radicals play a key role in many physiological decisions in cells. Since free radicals are toxic to cellular components, it is known that they cause DNA damage, contribute to DNA instability and mutation and thus favor carcinogenesis. However, nowadays it is assumed that free radicals play a further complex role in cancer. Low levels of free radicals and steady state levels of antioxidant enzymes are responsible for the fine tuning of redox status inside cells. A change in redox state is a way to modify the physiological status of the cell, in fact, a more reduced status is found in resting cells while a more oxidative status is associated with proliferative cells. The mechanisms by which redox status can change the proliferative activity of cancer cells are related to transcriptional and posttranscriptional modifications of proteins that play a critical role in cell cycle control. Since cancer cells show higher levels of free radicals compared with their normal counterparts, it is believed that the anti-oxidative stress mechanism is also increased in cancer cells. In fact, the levels of some of the most important antioxidant enzymes are elevated in advanced status of some types of tumors. Anti-cancer treatment is compromised by survival mechanisms in cancer cells and collateral damage in normal non-pathological tissues. Though some resistance mechanisms have been described, they do not yet explain why treatment of cancer fails in several tumors. Given that some antitumoral treatments are based on the generation of free radicals, we will discuss in this review the possible role of antioxidant enzymes in the survival mechanism in cancer cells and then, its participation in the failure of cancer treatments.
... Radiation therapy, with or without concomitant hormonal therapy, is a mainstay of prostate cancer therapy, with more than 750,000 patients treated per year. Of newly diagnosed prostate cancer patients, approximately 30% have high-risk disease (stage T3-T4, initial prostate-specific antigen level greater than 20 mg/L, or Gleason score of [8][9][10] and are at risk for biochemical and clinical failure after therapy (2). Even with modern conformal radiation therapy, treatment failure occurs in approximately 45% of patients with locally defined disease (3). ...
... A recent study demonstrated that reduced nicotinamide adenine dinucleotide phosphate oxidase enzymes are upregulated in response to androgens, stimulating the production of stress molecules and antioxidative enzymes; inhibition of these enzymes sensitizes human prostate cancer cells in vitro to radiation (6). Additional studies have found a critical role for glutathione in mediating radiation resistance in prostate cancer (8,9). Intracellular redox status is often characterized by the ratio of reduced to oxidized glutathione (glutathione-to-GSSG ratio), and decreasing this ratio in vitro (by addition of selenite) was found to radiosensitize prostate cancer cells (10). ...
Unlabelled:
Reduction and oxidation (redox) chemistry is increasingly implicated in cancer pathogenesis. To interrogate the redox status of prostate tumors noninvasively, we developed hyperpolarized [1-(13)C]dehydroascorbate ((13)C-DHA), the oxidized form of vitamin C, as an MR probe. In a model of transgenic adenocarcinoma of the mouse prostate (TRAMP), increased reduction of hyperpolarized (13)C-DHA to vitamin C was observed in tumor, as compared with normal prostate and surrounding benign tissue. We hypothesized that this difference was due to higher concentrations of glutathione and increased transport of hyperpolarized (13)C-DHA via the glucose transporters (GLUT1, GLUT3, and GLUT4) in TRAMP tumor. To test these hypotheses, hyperpolarized (13)C-DHA MR spectroscopy (MRS) and (18)F-FDG PET were applied as complementary technologies in the TRAMP model.
Methods:
Late-stage TRAMP tumors (>4 cm(3)) were studied at similar time points (MR studies conducted < 24 h after PET) in fasting mice by (18)F-FDG PET and hyperpolarized (13)C-DHA MR imaging on a small-animal PET/CT scanner and a (1)H/(3)C 3-T MR scanner. PET data were processed using open-source AMIDE software to compare the standardized uptake values of tumor with those of surrounding muscle, and (13)C-DHA MRS data were processed using custom software to compare the metabolite ratios (vitamin C/[vitamin C + (13)C-DHA]). After in vivo studies, the tumor glutathione concentrations were determined using a spectrophotometric assay, and thiol staining was performed using mercury orange. Real-time polymerase chain reaction was used to evaluate the relevant transporters GLUT1, GLUT3, and GLUT4 and vitamin C transporters SVCT1 and SVCT2. GLUT1 was also evaluated by immunohistochemistry.
Results:
The average metabolite ratio was 0.28 ± 0.02 in TRAMP tumor, versus 0.11 ± 0.02 in surrounding benign tissue (n = 4), representing a 2.5-fold difference. The corresponding tumor-to-nontumor (18)F-FDG uptake ratio was 3.0. The total glutathione was 5.1 ± 0.4 mM in tumor and 1.0 ± 0.2 mM in normal prostate, whereas reduced glutathione was 2.0 ± 0.3 mM and 0.8 ± 0.3 mM, respectively, corresponding to a 2.5-fold difference. In TRAMP tumor, mercury orange staining demonstrated increased thiols. Real-time polymerase chain reaction showed no significant difference in GLUT1 messenger RNA between TRAMP tumor and normal prostate, with immunohistochemistry (anti-GLUT1) also showing comparable staining.
Conclusion:
Both hyperpolarized (13)C-DHA and (18)F-FDG provide similar tumor contrast in the TRAMP model. Our findings suggest that the mechanism of in vivo hyperpolarized (13)C-DHA reduction and the resulting tumor contrast correlates most strongly with glutathione concentration. In the TRAMP model, GLUT1 is not significantly upregulated and is unlikely to account for the contrast obtained using hyperpolarized (13)C-DHA or (18)F-FDG.
... Sainz et al. showed that melatonin may protect LNCaP prostate cancer cells against ionizing radiation through stimulation of GSH. The results showed that although melatonin suppresses anti-apoptosis mediators like NF-κB, a dramatic increase in the level of GSH protects LNCaP cells upon ionizing radiation-induced apoptosis [41]. ...
Resistance to therapy and the toxicity of normal tissue are the major problems for efficacy associated with chemotherapy and radiotherapy. Drug resistance is responsible for most cases of mortality associated with cancer. Furthermore, their side effects can decrease the quality of life for surviving patients. An enhancement in the tumor response to therapy and alleviation of toxic effects remain unsolved challenges. One of the interesting topics is the administration of agents with low toxicity to protect normal tissues and/or sensitize cancers to chemo/radiotherapy. Melatonin is a natural body hormone that is known as a multitasking molecule. Although it has antioxidant properties, a large number of experiments have uncovered interesting effects of melatonin that can increase the therapeutic efficacy of chemo/radiation therapy. Melatonin can enhance anticancer therapy efficacy through various mechanisms, cells such as the immune system, and modulation of cell cycle and death pathways, tumor suppressor genes, and also through suppression of some drug resistance mediators. However, melatonin may protect normal tissues through the suppression of inflammation, fibrosis, and massive oxidative stress in normal cells and tissues. In this review, we will discuss the distinct effects of melatonin on both tumors and normal tissues. We review how melatonin may enhance radio/chemosensitivity of tumors while protecting normal tissues such as the lung, heart, gastrointestinal system, reproductive system, brain, liver, and kidney.
... Melatonin, an ROS scavenger [25], exhibits beneficial effects on various pathophysiological conditions characterized by ROS overproduction [26]. However, melatonin also presents prooxidant ability and induces high ROS at high levels [27][28][29]. In the present study, we demonstrated that low concentration (μM levels) of melatonin could downregulate ROS while high concentrations (mM levels) of melatonin had the opposite effect. ...
Background
Oral squamous cell carcinomas are one of the most common cancers worldwide with aggressive behavior and poor prognosis. Reactive oxygen species (ROS) are associated with cancer and cause various types of regulated cell death (RCD). Inducing the RCD pathway by modulating ROS levels is imperative to conquer cancers. The aim of this study is to investigate the synergistic anticancer effects of melatonin and erastin on ROS modulation and subsequent RCD induction.
Methods
Human tongue squamous cell carcinoma cell lines (SCC-15 cells) were treated with melatonin, erastin, or their combination. Cell viability, ROS levels, autophagy, apoptosis, and ferroptosis levels were tested according to the results of the PCR array, which were verified with/without the induction and inhibition of ROS by H 2 O 2 and N-acetyl-L-cysteine, respectively. In addition, a mouse-based subcutaneous oral cancer xenograft model was constructed to identify the effects of melatonin, erastin, and their combination on the autophagy, apoptosis, and ferroptosis levels in isolated tumor tissues.
Results
ROS levels were increased by the administration of melatonin at high concentrations (mM), and the combination of melatonin with erastin enhanced the levels of malonic dialdehyde, ROS, and lipid ROS, and reduced the levels of glutamate and glutathione. SQSTM1/p62, LC3A/B, cleaved caspase-3, and PARP1 protein levels in SCC-15 cells were also increased by melatonin plus erastin treatment, which further increased as ROS accumulated, and decreased as ROS levels were suppressed. Combined treatment of melatonin and erastin markedly reduced the tumor size in vivo, demonstrated no obvious systemic side effects, and significantly enhanced the apoptosis and ferroptosis levels in the tumor tissues, in parallel with decreased autophagy levels.
Conclusions
Melatonin combined with erastin exhibits synergistic anticancer effects without adverse reactions. Herein, this combination might become a promising alternative strategy for oral cancer treatment.
Graphical Abstract
... To con rm the effects of androgen signalling on glucose transporters, we employed hormone-sensitive and castration-resistant LNCaP cells (LNCaP-R). LNCaP-R were previously established by permanent growth without androgens [33]. First, we noticed that GLUT1 was signi cantly lower in the castrationresistant LNCaP-R corroborating its dependence of androgens but GLUT3, GLUT4 and GLUT12 were higher in LNCaP-R than in the LNCaP parental cells (Fig. 1h). ...
Background: Diabetic men are less likely to suffer prostate cancer, and insulin signalling through insulin receptors has been long considered. However, the role of insulin-dependent glucose transporters has yet to be elucidated. The unique metabolic properties of prostate cancer are attributed to the central role of androgens. Androgen-sensitive tumour cells have higher mitochondrial activity, while castration-resistant cells exhibit aerobic glycolysis. In addition, to glycolysis, one of the hallmarks of cancer metabolism is increased glucose uptake. However, the prostate's oncogenic value of glucose transporters (GLUTs) needs to be better characterized. This research aims to discover the relevance of insulin-dependent glucose transporters to cancer progression and their importance in the protective role of diabetes in prostate cancer.
Methods: Androgen-sensitive LNCaP and androgen-insensitive PC-3 cells were used in vitro. Castration-resistant LNCaP-R cells and cells overexpressing GLUT1 or GLUT4 were established from LNCaP cell line. In addition, TRAMP (Transgenic Adenocarcinoma of Mouse Prostate) mice and prostatic samples from patients were employed.
Results: We found that androgens stimulate insulin-independent glucose transporters, while androgen independence is associated with GLUT4 overexpression. The ectopic overexpression of GLUT4 promotes the characteristics of a castration-resistant phenotype. Metabolomics confirmed that hormone-resistant prostate cancer cells show an oxidative metabolism with a clear enrichment in amino acid metabolism. Diabetic TRAMP mice showed total tumour regression, while insulin administration restored proliferation and recovered GLUT4 levels. The levels of GLUT4 increase along with tumour progression in TRAMP mice, and it is reduced by castration and streptozotocin-induced diabetes. Finally, the levels of GLUT4 accumulation in tumour tissues compared to normal epithelial in patients' samples showed a clear co-location with nuclear AR.
Conclusion: Here it is confirmed the relevance of insulin-mediated glucose uptake through GLUT4 with prostate cancer progression and its relation to the reduced occurrence of prostate cancer in diabetic men.
... Melatonin has anti-in ammatory and antioxidant properties. NF-κB, an important in ammatory pathway factor, can be inhibited by melatonin, reducing pro-in ammatory cytokines [34]. Melatonin levels in C57BL/6 mice showed a peak at 1:00 AM and a trough at 10:00 PM [35]. ...
Background
Psoriasis is an immune-mediated inflammatory skin disease. The circadian clock influence immune cells and control the skin’s inflammatory response. In this study, we observed the effect of LiangxueJiedu Formula (LXJDF) on imiquimod-induced per2-knockout mice to explore the mechanism of Chinese medicinal herbs in improving skin inflammation via the circadian clock.
Methods
The per2−/− mice were randomly divided into the model group, the LXJDF group, and the positive drug group (dexamethasone). The dorsal skin of mice was smeared with imiquimod at 9:00 AM (ZT1), and the corresponding drugs were given at 10:00AM (ZT2) and 10:00 PM (ZT14), respectively. The wild-type (WT) mice were smeared vaseline as the control group. The skin lesions were observed and PASI was performed for six consecutive days. The pathological morphology of the skin was determined by HE and immunofluorescence (Ki67, loricrin, and IL-17A) staining, and the epidermis thickness was measured. The spleen weight and index were calculated, and the splenocyte subtypes and serum cytokine levels were detected by flow cytometry. The serum melatonin levels were detected by ELISA. The gene expressions of inflammatory cytokines in the skin were determined by qPCR. The gene and protein expressions of circadian clock-related genes (CLOCK, BMAL1, REV-ERBα, NFIL3, and RORγt) in the skin were determined by qPCR and western blot.
Results
LXJDF could significantly improve the psoriasiform skin lesions, including the reduction of PASI, thinning of epidermal thickness, inhibition of keratinocytes proliferation, and parakeratosis at two-time points (ZT2 and ZT14). LXJDF could reduce the spleen weight and index and inhibit the number of Th17 cells, γδT cells, and the serum inflammatory factors levels of IL-17A, IL-17F, TNF-α, IL-22, IL-6. In addition, LXJDF could significantly down-regulate the mRNA expressions of IL-17A, IL-17F, IL-23, and IL-6 in the skin. LXJDF significantly increased the expressions of BMAL1 and REV-ERBα, and decreased NFIL3 and RORγt.
Conclusions
LXJDF ameliorates psoriatic dermatitis by regulating the circadian clock to inhibit IL-17-producing Th17 and γδT cells.
... Epigallocatechin-3-gallate (EGCG), present in green tea, can inhibit the methylation of DNA, which induces anticancer effects with full anti-PCa potential, leading to treatment of CRPC patients [181]. In the case of CRPC, curcumin enhanced TNF and radiation-induced apoptosis by suppressing IkB phosphorylation, downregulating the anti-apoptotic gene products and activating the caspases in human PCa cells [182]. Embelin is an-other natural phytoestrogen that can suppress several signaling mechanisms, including cancer formation, via blocking XIAP and caspase-9 interaction [183]. ...
Prostate cancer remains one of the most frequent and deadliest malignancies in males, where the rate of disease progression is closely associated with the type of dietary intake, specifically Western-style diet. Indeed intake of the Asian diet, which contains abundant phytoestrogens, is inversely correlated with a higher risk of prostate cancer, suggesting a chemoprotective effect of phytoestrogen against cancer progression. Although the role of phytoestrogens in cancer treatment was well documented, their impact on prostate cancer is not well understood. Therefore, the present review discusses the possible chemopreventive effect of phytoestrogens, emphasizing their efficacy at the different stages of carcinogenesis. Furthermore, phytoestrogens provide a cytoprotective effect in conventional chemotherapy and enhance chemosensitivity to tumor cells, which have also been discussed. This compilation provides a solid basis for future research on phytoestrogens as a promising avenue for anticancer drug development and also recommends these beneficiary compounds in the daily diet to manage and prevent prostate cancer.
... It has been shown to enhance TNF and radiation-induced apoptosis in human PCa cells. It inhibits NF k B by the suppression of I k B phosphorylation, which downregulates the anti-apoptotic gene products and activates the caspases (Sainz et al., 2008). Like curcumin, pieces of evidence showed that polyphenols such as epicatechin-3-gallate (ECG) and epigallocatechin-3-gallate (EGCG) present in green tea can inhibit the methylation of DNA, which induces anticancer effects with potent anti-PCa potential (Kallifatidis et al., 2016;Wang et al., 2020). ...
Prostate cancer is the most common type of cancer among men and the second most frequent cause of cancer-related mortality around the world. The progression of advanced prostate cancer to castration-resistant prostate cancer (CRPC) plays a major role in disease-associated morbidity and mortality, posing a significant therapeutic challenge. Resistance has been associated with the activation of androgen receptors via several mechanisms, including alternative dehydroepiandrosterone biosynthetic pathways, other androgen receptor activator molecules, oncogenes, and carcinogenic signaling pathways. Tumor microenvironment plays a critical role not only in the cancer progression but also in the drug resistance. Numerous natural products have shown major potential against particular or multiple resistance pathways as shown by in vitro and in vivo studies. However, their efficacy in clinical trials has been undermined by their unfavorable pharmacological properties (hydrophobic molecules, instability, low pharmacokinetic profile, poor water solubility, and high excretion rate). Nanoparticle formulations can provide a way out of the stalemate, employing targeted drug delivery, improved pharmacokinetic drug profile, and transportation of diagnostic and therapeutic agents via otherwise impermeable biological barriers. This review compiles the available evidence regarding the use of natural products for the management of CRPC with a focus on nanoparticle formulations. PubMed and Google Scholar search engines were used for preclinical studies, while ClinicalTrials.gov and PubMed were searched for clinical studies. The results of our study suggest the efficacy of natural compounds such as curcumin, resveratrol, apigenin, quercetin, fisetin, luteolin, kaempferol, genistein, berberine, ursolic acid, eugenol, gingerol, and ellagic acid against several mechanisms leading to castration resistance in preclinical studies, but fail to set the disease under control in clinical studies. Nanoparticle formulations of curcumin and quercetin seem to increase their potential in clinical settings. Using nanoparticles based on betulinic acid, capsaicin, sintokamide A, niphatenones A and B, as well as atraric acid seems promising but needs to be verified with preclinical and clinical studies.
... It has been shown to enhance TNF and radiation-induced apoptosis in human PCa cells. It inhibits NF k B by the suppression of I k B phosphorylation, which downregulates the anti-apoptotic gene products and activates the caspases (Sainz et al., 2008). Like curcumin, pieces of evidence showed that polyphenols such as epicatechin-3-gallate (ECG) and epigallocatechin-3-gallate (EGCG) present in green tea can inhibit the methylation of DNA, which induces anticancer effects with potent anti-PCa potential (Kallifatidis et al., 2016;Wang et al., 2020). ...
Prostate cancer is the most common type of cancer among men and the second most frequent cause of cancer-related mortality around the world. The progression of advanced prostate cancer to castration-resistant prostate cancer (CRPC) plays a major role in disease-associated morbidity and mortality, posing a significant therapeutic challenge. Resistance has been associated with the activation of androgen receptors via several mechanisms, including alternative dehydroepiandrosterone biosynthetic pathways, other androgen receptor activator molecules, oncogenes, and carcinogenic signaling pathways. Tumor microenvironment plays a critical role not only in the cancer progression but also in the drug resistance. Numerous natural products have shown major potential against particular or multiple resistance pathways as shown by in vitro and in vivo studies. However, their efficacy in clinical trials has been undermined by their unfavorable pharmacological properties (hydrophobic molecules, instability, low pharmacokinetic profile, poor water solubility, and high excretion rate). Nanoparticle formulations can provide a way out of the stalemate, employing targeted drug delivery, improved pharmacokinetic drug profile, and transportation of diagnostic and therapeutic agents via otherwise impermeable biological barriers. This review compiles the available evidence regarding the use of natural products for the management of CRPC with a focus on nanoparticle formulations. PubMed and Google Scholar search engines were used for preclinical studies, while ClinicalTrials.gov and PubMed were searched for clinical studies. The results of our study suggest the efficacy of natural compounds such as curcumin, resveratrol, apigenin, quercetin, fisetin, luteolin, kaempferol, genistein, berberine, ursolic acid, eugenol, gingerol, and ellagic acid against several mechanisms leading to castration resistance in preclinical studies, but fail to set the disease under Frontiers in Cell and Developmental Biology | www.frontiersin.org 1 November 2021 | Volume 9 | Article 745177 Singla et al. Natural Products Against CRPC control in clinical studies. Nanoparticle formulations of curcumin and quercetin seem to increase their potential in clinical settings. Using nanoparticles based on betulinic acid, capsaicin, sintokamide A, niphatenones A and B, as well as atraric acid seems promising but needs to be verified with preclinical and clinical studies.
... Moreover, it downregulates the expression of the antiapoptotic factor Bcl-2 and the cell survival factor survivin. 64 Apoptosis clears undesirable malformed cells and cancer cells. Several factors and enzymes are involved in this process. ...
Melatonin is an endogenous indolamine, synthesized and secreted from the pineal gland. The environmental light-dark cycle is the primary regulator of melatonin synthesis. Darkness during the subjective night induces noradrenaline secretion, which stimulates pinealocytes for melatonin production. Melatonin exhibits anticancer effects and different physiological functions through the membrane-bound G-protein-coupled MT1 and MT2 receptors. Impaired circadian activity, indoor or outdoor light pollution, shift work, night work, and jet lag suppress normal melatonin synthesis. Decreased melatonin concentration causes impaired anticancer effects that adversely affect the progression of different cancers, including prostate. Melatonin differentially regulates the cell cycle, cell survival, and metabolism in malignant cells in contrast to normal prostate epithelial cells. Melatonin promotes the nuclear exclusion of androgen receptors without suppressing the expression of this receptor. This indirect effect blocks the androgenic response in prostate cancer cells. It acts as a cytostatic and cytotoxic agent, prevents cell proliferation, and activates an apoptotic response. Melatonin also inhibits HIF-1α activity and the expression of vascular endothelial growth factors to suppress angiogenesis. This indolamine restricts alteration of metabolic activity, invasion, and metastasis. Melatonin has therapeutic importance. It decreases the side effects of anticancer treatment and mitigates adverse effects after prostatectomy and radiotherapy. Melatonin blocks the recurrence of prostate cancer as well as hormone-refractory effects during androgen deprivation therapy. The present review discusses the multifaceted effects of melatonin against prostate cancer.
... Joo et al. [200] showed that treating the androgensensitive LNCaP cells with melatonin clearly increased the number of apoptotic cells with a significant up-regulation of apoptosis-related proteins Bax and Cyt c and a decrease of survival protein Bcl-2, via activating the JNK and p38 cascade. Sainz et al. [201] examined the effect of melatonin when given in combination with TNFα or γ-radiation. Results showed that melatonin obviously arrests PCa cells in the G0/G1 phase with an increase of p21 protein and significantly elevates the efficiency of TNFα treatment via inactivating NF-κB. ...
Prostate cancer (PCa) is one of the most commonly diagnosed human cancers in males. Nearly 191,930 new cases and 33,330 new deaths of PCa are estimated in 2020. Androgen and androgen receptor pathways played essential roles in the pathogenesis of PCa. Androgen depletion therapy is the most used therapies for primary PCa patients. However, due to the high relapse and mortality of PCa, developing novel noninvasive therapies have become the focus of research. Melatonin is an indole-like neurohormone mainly produced in the human pineal gland with a prominent anti-oxidant property. The anti-tumor ability of melatonin has been substantially confirmed and several related articles have also reported the inhibitory effect of melatonin on PCa, while reviews of this inhibitory effect of melatonin on PCa in recent 10 years are absent. Therefore, we systematically discuss the relationship between melatonin disruption and the risk of PCa, the mechanism of how melatonin inhibited PCa, and the synergistic benefits of melatonin and other drugs to summarize current understandings about the function of melatonin in suppressing human prostate cancer. We also raise several unsolved issues that need to be resolved to translate currently non-clinical trials of melatonin for clinic use. We hope this literature review could provide a solid theoretical basis for the future utilization of melatonin in preventing, diagnosing and treating human prostate cancer.
... Sainz et al reported that 1-mM melatonin does not promote IR-induced cell death due to increased GSH content. 19 Similarly, we found that 1-mM melatonin prevented IR-induced cell death. The protective effect is due to enhanced antioxidant capacity by the presence of a high concentration of melatonin. ...
The purpose of this study is to investigate the effects of melatonin on the radiosensitivity of HeLa cells. Concentration from 10 to 1000 µM of melatonin was used on HeLa cells before X-rays irradiation (IR). The cellular inactivation effect was analyzed by clonogenic assay, and cell growth was measured by MTT assay at various concentrations. Ten micrometer melatonin promoted the cell-killing effects of IR, while 1000-µM melatonin prevented IR-induced cellular inactivation. Further analysis revealed that 1000-µM melatonin protected the cells from IR-induced reactive oxygen species damage, as the oxidative stress measured by fluorescent microscopy and fluorescence-activated cell sorting using 2,7-dichlorofluorescein diacetate staining. This is further confirmed by melatonin receptor agonist, which has no antioxidant capacity. A 10-µM melatonin, on the contrary, enhanced the cell-killing effects of IR by activating c-Jun NH2-terminal kinase (JNK) signaling. c-Jun NH2-terminal kinase signaling activation was indicated by Western blot of phosphorylated JNK. We used JNK inhibitor to further confirm the involvement of JNK signaling in the cell-killing enhancement of 10-µM melatonin administration. Our results suggest the importance of dose-dependent effects in melatonin application for radiotherapy.
... This finding did not receive much attention nor interest although the observation was later confirmed by Winiarska et al (25). Recently, however, Sainz and co-workers reported that the incubation of either LNCap or PC3 prostate cells with melatonin almost doubled the already high concentrations of GSH and protected the cells from ionizing radiation, a treatment associated with excessive free radical generation (26). In the same study, depletion of GSH levels by inhibition of its synthesis greatly increased the vulnerability of these cells to radiation-mediated damage and apoptosis. ...
... For example, in LNCaP prostate cancer cells, melatonin can protect against ionizing radiation due to increasing level of glutathione. Therefore, for sensitization of LNCaP cancer cells to apoptosis, melatonin should be combined with an inhibitor of glutathione [126] . In this section, the mechanisms of apoptosis stimulation by melatonin and its possible radio/chemosensitization effect on tumor cells are described. ...
Radio- and chemotherapy are the most common cancer treatment modalities. They cause acute and late side effects on normal tissues, which is a burden for delivery of a high dose of radiation or drugs on tumor cells. In addition, tumor cells achieve adaptive responses to subsequent doses of radiation and chemotherapy, leading to tumor resistance and accelerated repopulation. Resistance to radiotherapy and chemotherapy can occur following adaptive responses, which itself is due to the release of large numbers of inter- and intracellular mediators by immune cells as well as other tumor microenvironment (TME) cells. Melatonin is a potent natural antioxidant and anti-inflammatory agent that protects against toxic side effects of radiation and chemotherapy. Furthermore, in some cancer cells, melatonin aids sensitizing cancer cells to therapy. Apoptosis is one of the main mechanisms of cell death following exposure to radiation and chemotherapy. Evidences have shown a direct relation between apoptosis induction in tumor cells with increased tumor delay regression and survival. Melatonin through modulation of several apoptosis mediators such as mitochondria, Bax, Bcl-2, endogenous ROS, and apoptosis receptors facilitate apoptosis. The current review aims to explain mechanisms of apoptosis induction following exposure to radiation and chemotherapy drugs. We also reviewed the modulatory effect of melatonin on apoptosis signaling pathways.
... The effect of melatonin was not mediated by PKA although a transitory rise in cAMP levels was observed [81]. In androgen-dependent prostate cancer cells, it has been demonstrated that pharmacological doses of melatonin (ranging from 50 nM to 1 mM) increased p21 levels, decreased NF-κB activation, and Bcl-2 and survivin were downregulated [82]. The inhibition of NF-κB signaling via melatonin-dependent activation (melatonin dose: 10 nM) of PKA and PKC resulted in transcriptional upregulation of p27 (Kip1), a MT1-dependent antiproliferative signaling mechanism [83]. ...
Melatonin (N-acetyl-5-methoxytryptamine) is a hormone synthesized and secreted by the pineal gland mainly during the night, since light exposure suppresses its production. Initially, an implication of this indoleamine in malignant disease was described in endocrine-responsive breast cancer. Data from several clinical trials and multiple experimental studies performed both in vivo and in vitro have documented that the pineal hormone inhibits endocrine-dependent mammary tumors by interfering with the estrogen signaling-mediated transcription, therefore behaving as a selective estrogen receptor modulator (SERM). Additionally, melatonin regulates the production of estradiol through the control of the enzymes involved in its synthesis, acting as a selective estrogen enzyme modulator (SEEM). Many more mechanisms have been proposed during the past few years, including signaling triggered after activation of the membrane melatonin receptors MT-1 and MT-2, or else intracellular actions targeting molecules such as calmodulin, or binding intranuclear receptors. Similar results have been obtained in prostate (regulation of enzymes involved in androgen synthesis and modulation of androgen receptor levels and activity) and ovary cancer. Thus, tumor metabolism, gene expression, or epigenetic modifications are modulated, cell growth is impaired and angiogenesis and metastasis are inhibited. In the last decade, many more reports have demonstrated that melatonin is a promising adjuvant molecule with many potential beneficial consequences when included in chemotherapy or radiotherapy protocols designed to treat endocrine-responsive tumors. Therefore, in this state-of-the-art review, we aim to compile the knowledge about the oncostatic actions of the indoleamine in hormone-dependent tumors, and the latest findings concerning melatonin actions when administered in combination with radio- or chemotherapy in breast, prostate, and ovary cancers. As melatonin has no toxicity, it may be well deserve to be considered as an endogenously generated agent helpful in cancer prevention and treatment.
... Glutathione peroxidase 1 polymorphism is involved in prostate carcinogenesis [57]. Glutathione exhibits an important role in survival mechanisms of PC cells [58] and this pathway is linked to the antineoplastic function and recrudescence in PC [59,60]. The p53 gene is the most common mutant gene in human tumors, and the primary function of the p53 protein is to prevent the cells into the DNA synthesis period and make it stagnation in the G1 phase to repair damaged DNA [61,62]. ...
The present study aimed to investigate the gene expression changes in prostate cancer (PC) and screen the hub genes and associated pathways of PC progression. The authors employed integrated analysis of GSE46602 downloaded from the Gene Expression Omnibus and The Cancer Genome Atlas databases to identify 484 consensual differentially expressed genes (DEGs) in PC, when compared with adjacent normal tissue samples. Functional annotation and pathway analysis were performed. The protein-protein interaction (PPI) networks and module were constructed. RT-qPCR was used to validate the results in clinical PC samples. Survival analysis of hub genes was performed to explore their clinical value. GO analysis results revealed that DEGs were significantly enriched in negative regulation of nitrobenzene metabolic process, extracellular space and protein homodimerization activity. KEGG pathway analysis results revealed that DEGs were most significantly enriched in focal adhesion. The top 10 hub genes were identified to be hub genes from the PPI network, and the model revealed that these genes were enriched in various pathways, including neuroactive ligand-receptor interaction, p53 and glutathione metabolism signaling pathways. RT-qPCR results validated that expression levels of eight genes (PIK3R1, BIRC5, ITGB4, RRM2, TOP2A, ANXA1, LPAR1 and ITGB8) were consistent with the bioinformatics analysis. ITGB4 and RRM2 with genetic alterations exhibited association with a poorer survival rate, compared with those without alterations. These results revealed that PC-related genes and pathways have an important role in tumor expansion, metastasis and prognosis. In summary, these hub genes and related pathways may act as biomarkers or therapeutic targets for PC.
... This factor has proliferative effects by its direct action on cyclin D1 (Li et al. 2015). Also, melatonin induces apoptosis by activating the caspase-dependent apoptotic pathway, enhancing tumor necrosis factor, downregulating Bcl-2, and survival, by inhibiting the nuclear translocation of NF-κB p65 (Sainz et al. 2008;Joo and Yoo 2009). For example, Ramos cells (human Burkitt's lymphoma B cells) are very sensitive to melatonin caused by a dose-dependent G1-phase cell cycle arrest and apoptosis. ...
... These observations suggest that melatonin interferes with the processes of angiogenesis in prostate tumors, which is a major factor driving cancer progression [288]. Melatonin also controls the generation of reactive oxygen species (ROS) and significantly increases the total content of glutathione in prostate cancer cells [289,290]. Due to its actions in redox regulation, melatonin modulates intracellular oxidant stress and thereby determines malignant progression of the disease. Additionally, the indoleamine influences the production of cytokines and chemokines by human prostate cancer cells [291] and in patients with advanced prostate tumors [292]. ...
There is highly credible evidence that melatonin mitigates cancer at the initiation, progression and metastasis phases. In many cases, the molecular mechanisms underpinning these inhibitory actions have been proposed. What is rather perplexing, however, is the large number of processes by which melatonin reportedly restrains cancer development and growth. These diverse actions suggest that what is being observed are merely epiphenomena of an underlying more fundamental action of melatonin that remains to be disclosed. Some of the arresting actions of melatonin on cancer are clearly membrane receptor-mediated while others are membrane receptor-independent and involve direct intracellular actions of this ubiquitously-distributed molecule. While the emphasis of melatonin/cancer research has been on the role of the indoleamine in restraining breast cancer, this is changing quickly with many cancer types having been shown to be susceptible to inhibition by melatonin. There are several facets of this research which could have immediate applications at the clinical level. Many studies have shown that melatonin’s co-administration improves the sensitivity of cancers to inhibition by conventional drugs. Even more important are the findings that melatonin renders cancers previously totally resistant to treatment sensitive to these same therapies. Melatonin also inhibits molecular processes associated with metastasis by limiting the entrance of cancer cells into the vascular system and preventing them from establishing secondary growths at distant sites. This is of particular importance since cancer metastasis often significantly contributes to death of the patient. Another area that deserves additional consideration is related to the capacity of melatonin in reducing the toxic consequences of anti-cancer drugs while increasing their efficacy. Although this information has been available for more than a decade, it has not been adequately exploited at the clinical level. Even if the only beneficial actions of melatonin in cancer patients are its ability to attenuate acute and long-term drug toxicity, melatonin should be used to improve the physical wellbeing of the patients. The experimental findings, however, suggest that the advantages of using melatonin as a co-treatment with conventional cancer therapies would far exceed improvements in the wellbeing of the patients.
... Then, preclinical studies using cells or animal models supported the role of some bioactive compounds as chemo-preventive agents. Their relatively low toxicity, low cost, easy availability and their possible role as adjuvants that potentiate the effect of different chemotherapeutic drugs has been investigated for the last years [14][15][16][17]. In the current study, the effect of four natural compounds, i.e.: curcumin, a natural dye extracted from Curcuma longa L.; resveratrol, a polyphenolic stilbene found in grapes; silibinin, a naturally-occurring flavonoid produced by milk thistle and melatonin, an indole that is mainly produced by the pineal gland in vertebrates but also found in edible plants [18], was investigated. ...
Accumulating evidence suggests that natural bioactive compounds, alone or in combination with traditional chemotherapeutic agents, could be used as potential therapies to fight cancer. In this study, we employed four natural bioactive compounds (curcumin, resveratrol, melatonin, and silibinin) and studied their role in redox control and ability to promote apoptosis in androgen sensitive and insensitive prostate cancer cells. Here is shown that curcumin and resveratrol promote ROS production and induce apoptosis in LNCaP and PC-3. An increase in reactive species is a trigger event in curcumin-induced apoptosis and a consequence of resveratrol effects on other pathways within these cells. Moreover, here we demonstrated that these four compounds affect differently one of the main intracellular redox regulator, the thioredoxin system. Exposure to curcumin and resveratrol promoted TRX1 oxidation and altered its subcellular location. Furthermore, resveratrol diminished TRX1 levels in PC-3 cells and increased the expression of its inhibitor TXNIP. Conversly, melatonin and silibinin only worked as cytostatic agents, reducing ROS levels and showing preventive effects against TRX oxidation. All together, this work explores the effect of compounds currently tested as chemo-preventive agents in prostate cancer therapy, on the TRX1 redox state and function. Our work shows the importance that the TRX system might have within the differences found in their mechanisms of action. These bioactive compounds trigger different responses and affect ROS production and redox systems in prostate cancer cells, suggesting the key role that redox-related pathways might play in processes like differentiation or survival in prostate cancer.
... This factor has proliferative effects by its direct action on cyclin D1 (Li et al. 2015). Also, melatonin induces apoptosis by activating the caspase-dependent apoptotic pathway, enhancing tumor necrosis factor, downregulating Bcl-2, and survival, by inhibiting the nuclear translocation of NF-κB p65 (Sainz et al. 2008;Joo and Yoo 2009). For example, Ramos cells (human Burkitt's lymphoma B cells) are very sensitive to melatonin caused by a dose-dependent G1-phase cell cycle arrest and apoptosis. ...
Radiotherapy has a key role in cancer treatment in
more than half of patients with cancer. The management of
severe side effects of this treatment modality is a limiting
factor to appropriate treatment. Immune system responses
play a pivotal role in many of the early and late side effects
of radiation. Moreover, immune cells have a significant role in
tumor response to radiotherapy, such as angiogenesis and tumor
growth. Melatonin as a potent antioxidant has shown
appropriate immune regulatory properties that may ameliorate
toxicity induced by radiation in various organs. These effects
are mediated through various modulatory effects of melatonin
in different levels of tissue reaction to ionizing radiation. The
effects on the DNA repair system, antioxidant enzymes, immune
cells, cytokines secretion, transcription factors, and protein
kinases are most important. Moreover, anti-cancer properties
of melatonin may increase the therapeutic ratio of radiotherapy.
Clinical applications of this agent for the management
of malignancies such as breast cancer have shown promising
results. It seems anti-proliferative, anti-angiogenesis, and
stimulation or suppression of some immune cell responses
are the main anti-tumor effects of melatonin that may help to
improve response of the tumor to radiotherapy. In this review,
the effects of melatonin on the modulation of immune responses
in both normal and tumor tissues will be discussed.
... Promotes TRAIL-induced apoptosis in human colon cancer cells [360] Enhances the chemotherapeutic effects of adriamycin on human prostate carcinoma cells [394] Enhances apoptotic effects of lovastatin in human colorectal carcinoma cells [395] Melatonin: Inhibits the growth of non-small cell lung cancer, breast cancer, ovarian cancer, and rhabdomyosarcoma [396][397][398] Sensitizes non-small cell lung cancer cells to the tyrosine kinase inhibitor gefitinib [399] Enhances H 2 O 2 -induced apoptosis in human promyelocytic leukemia [400] Sensitizes human malignant glioma cells to TRAIL-induced cell death [401] Enhances TNF-and ionizing radiation-induced apoptosis in prostate cancer cells [402] Potentiates flavone-induced apoptosis in human colon cancer cells [403] Enhances arsenic trioxide-induced cell death in breast cancer cells [404] Synergizes the effects of doxorubicin in breast cancer cells [405] N-acetyl cysteine: Inhibits the growth of oral, prostate, and gastrointestinal cancer cells [406][407][408] Inhibit tumor cell invasion in vitro and metastasis in vivo [409] Enhances the lung cancer cells inhibitory effect of EGCG [410] Enhances fisetin-induced cytotoxicity in human colon cancer cells [411] Antioxidant enzymes: Expression of SOD2 suppresses HER2/neu-induced breast cancer cell growth [412] SOD1 and SOD2 overexpression significantly decreases growth and survival of breast cancer cells [413] (continued on next page) niche of cancer and (2) poor bioavailability, as many of them have poor absorption and rapid metabolic transformation [207][208][209]. Therefore, it is imperative to clinically test the efficacy of antioxidants with enhanced bioavailability that can target the specific niche of cancer, as such studies have the potential to provide a better-tailored anticancer treatment. ...
Reactive oxygen species (ROS), a group of highly reactive ions and molecules, are increasingly being appreciated as powerful signaling molecules involved in the regulation of a variety of biological processes. Indeed, their role is continuously being delineated in a variety of pathophysiological conditions. For instance, cancer cells are shown to have increased ROS levels in comparison to their normal counterparts. This is partly due to an enhanced metabolism and mitochondrial dysfunction in cancer cells. The escalated ROS generation in cancer cells contributes to the biochemical and molecular changes necessary for the tumor initiation, promotion and progression, as well as, tumor resistance to chemotherapy. Therefore, increased ROS in cancer cells may provide a unique opportunity to eliminate cancer cells via elevating ROS to highly toxic levels intracellularly, thereby, activating various ROS-induced cell death pathways, or inhibiting cancer cell resistance to chemotherapy. Such results can be achieved by using agents that either increase ROS generation, or inhibit antioxidant defense, or even a combination of both. In fact, a large variety of anticancer drugs, and some of those currently under clinical trials, effectively kill cancer cells and overcome drug resistance via enhancing ROS generation and/or impeding the antioxidant defense mechanism. This review focuses on our current understanding of the tumor promoting (tumorigenesis, angiogenesis, invasion and metastasis, and chemoresistance) and the tumor suppressive (apoptosis, autophagy, and necroptosis) functions of ROS, and highlights the potential mechanism(s) involved. It also sheds light on a very novel and an actively growing field of ROS-dependent cell death mechanism referred to as ferroptosis.
... Some reports suggest that ERK pathway activation influences a survival signal that weakens pro-apoptotic effects via activating JNK (24,25). Cisplatin through ERK pathway activation, slows down cell growth and causes apoptotic cell death (26). ...
Melatonin is synthesized by the pineal gland and is released into the blood. In the last several years, some studies have shown that melatonin has anticancer properties; however, the mechanisms behind the antitumour traits are unclear, especially in pancreatic cancer. Therefore, in the present study, we investigated the antitumour effects of melatonin on the human pancreatic carcinoma cell line MIA PaCa-2 and explored its biological mechanisms. MIA PaCa-2 cells were treated with melatonin, and we used a CCK-8 assay to evaluate the cell viability. We also used flow cytometry to observe cell apoptosis and western blot analysis to assess the protein expression. Our study found that melatonin inhibited cell viability, suppressed colony formation and reduced cell migration and invasion and induced cell apoptosis in MIA PaCa-2 cells. Our results showed that melatonin treatment inhibited NF-κB p65 activation. Moreover, melatonin treatment activated the mitogen-activated protein kinase pathways (c-jun N-terminal kinase and extracellular-regulated kinase 1/2), which increased Bax protein expression and caspase-3 cleavage and decreased Bcl-2 protein expression. These new developments demonstrate that melatonin plays a potential role in anticancer treatment and may act as an effective therapeutic agent in the future.
... There are several other nutraceuticals such as the Cruciferae-derived compound diindolylmethane, or polyphenols derived from green tea, grape seed and pomegranate, that target NF-κB activation and have been shown to control growth in PCa cells in vitro and in vivo [66,67]. Moreover, selenium, which is found in fish, meat, eggs and grains was shown to modulate genes involved in androgen regulation and could also reduce AR expression [68,69]. ...
Prostate cancer (PCa), a hormonally-driven cancer, ranks first in incidence and second in cancer related mortality in men in most Western industrialized countries. Androgen and androgen receptor (AR) are the dominant modulators of PCa growth. Over the last two decades multiple advancements in screening, treatment, surveillance and palliative care of PCa have significantly increased quality of life and survival following diagnosis. However, over 20% of patients initially diagnosed with PCa still develop an aggressive and treatment-refractory disease. Prevention or treatment for hormone-refractory PCa using bioactive compounds from marine sponges, mushrooms, and edible plants either as single agents or as adjuvants to existing therapy, has not been clinically successful. Major advancements have been made in the identification, testing and modification of the existing molecular structures of natural products. Additionally, conjugation of these compounds to novel matrices has enhanced their bio-availability; a big step towards bringing natural products to clinical trials. Natural products derived from edible plants (nutraceuticals), and common folk-medicines might offer advantages over synthetic compounds due to their broader range of targets, as compared to mostly single target synthetic anticancer compounds; e.g. kinase inhibitors. The use of synthetic inhibitors or antibodies that target a single aberrant molecule in cancer cells might be in part responsible for emergence of treatment refractory cancers. Nutraceuticals that target AR signaling (epigallocatechin gallate [EGCG], curcumin, and 5α-reductase inhibitors), AR synthesis (ericifolin, capsaicin and others) or AR degradation (betulinic acid, di-indolyl diamine, sulphoraphane, silibinin and others) are prime candidates for use as adjuvant or mono-therapies. Nutraceuticals target multiple pathophysiological mechanisms involved during cancer development and progression and thus have potential to simultaneously inhibit both prostate cancer growth and metastatic progression (e.g., inhibition of angiogenesis, epithelial-mesenchymal transition (EMT) and proliferation). Given their multi-targeting properties along with relatively lower systemic toxicity, these compounds offer significant therapeutic advantages for prevention and treatment of PCa. This review emphasizes the potential application of some of the well-researched natural compounds that target AR for prevention and therapy of PCa.
... Many previous studies have demonstrated that ERK pathway stimulation affects a survival signal that suppresses pro-apoptotic effects by activating p38 and JNK [33,34]. Cisplatin induces apoptotic death and arrests cell growth through ERK activation [35], and paclitaxel, a potent inducer of G2/M cell cycle arrest and apoptosis, requires the activation of MAPK pathways (ERK and p38) [36]. ...
Background/aims:
Melatonin, synthesized by the pineal gland and released into the blood, appears to have antitumour properties; however, the mechanisms of its anti-cancer effects are largely unknown, especially in stomach cancer. Here, we explore the antitumour activity of melatonin in a gastric cancer cell line (AGS) and analyse its molecular mechanisms.
Methods:
AGS cells were treated with melatonin, and cell viability was assessed using a CCK-8 assay. Flow cytometry was performed to evaluate apoptosis, and protein expression was examined by Western blotting.
Results:
Melatonin significantly inhibited cell viability, clone formation, and cell migration and invasion and induced apoptosis in AGS cells. Moreover, MAPK pathways (p38, JNK and ERK) were activated by melatonin treatment, which also significantly increased caspase-3 cleavage and Bax protein expression and decreased Bcl-2 protein expression in a time-dependent manner. Our results demonstrate that p38 and JNK inhibitors (SB203580 and SP600125, respectively) prevented melatonin-induced apoptosis; thus, the propensity of p38 MAPK and JNK to promote apoptosis could be at least partly due to the inhibition of NF-x03BA;B p65 activation by p38 and JNK. Finally, melatonin was able to strengthen cisplatin-mediated antitumour effects in human gastric carcinoma cells by up-regulating the expression of Bax, down-regulating the expression of Bcl-2 and activating the caspase-dependent apoptotic pathway.
Conclusion:
Melatonin induced apoptosis in AGS cells by activating the caspase-dependent apoptotic pathway and by inhibiting the nuclear translocation of NF-x03BA;B p65, two processes that are regulated by p38 and JNK. Furthermore, melatonin significantly enhanced the anti-tumour effects of cisplatin, with low systemic toxicity. These new findings suggest that melatonin may act as a potent anti-tumour agent and may have great potential as an adjuvant therapy in the future.
... Recently, it has been demonstrated that reduced nicotinamide adenine dinucleotide phosphate oxidase enzymes are upregulated in response to androgens, stimulating the production of stress molecules and antioxidative enzymes; inhibition of these enzymes sensitizes human prostatic carcinoma (PC) cells in vitro to radiation (19). Additional studies have found a critical role for glutathione in mediating radiation resistance in prostate cancer (20,21). Intracellular redox status is often characterized by the ratio of reduced to oxidized glutathione, and decreasing this ratio in vitro (by addition of selenite) was found to radiosensitize prostate cancer cells. ...
Hyperpolarization using dissolution dynamic nuclear polarization has emerged as a versatile method to dramatically improve the MR signal of low-sensitivity nuclei. This technique facilitates the study of real-time metabolism in vitro and in vivo using (13)C-enriched substrates and has been applied to numerous models of human disease. In particular, several mechanisms underlying prostate cancer have been interrogated using hyperpolarized (13)C MR spectroscopy. This review highlights key metabolic shifts seen in prostate cancer, their study by hyperpolarized (13)C MR spectroscopy, and the development of new platforms for metabolic study.
... The changing melatonin rhythm controls seasonal reproduction in photoperiodic animals through activation of receptors within the hypothalamic-pituitary reproductive axis [1,2]. Melatonin exerts anticancer effects on different tumor types [3][4][5], and it also is a broad spectrum antioxidant [6] and free radical scavenger [7][8][9]. Melatonin interacts with estrogen-signaling pathways through indirect neuroendocrine mechanisms, direct actions at the tumor cell level, and regulation of enzymes involved in the biosynthesis of estrogens [3,10]. ...
Calcium-binding protein-D9k (CaBP-9k) is a 9-kDa polypeptide, with 2 calcium binding sites, found in mammalian intestine, placenta, uterus, kidney, pituitary gland, and growth cartilage. However, the regulation of CaBP-9k by endocrine factors (i.e. melatonin) in pituitary gland is not known yet. Melatonin, the major secretory product of the pineal gland, has been known to interact with the neuroendocrine axis, circadian rhythms, and apoptotic pathways in various cell types. Thus, in this study, we investigated whether CaBP-9k gene is regulated by melatonin in association with hydrogen peroxide (H2O2)-induced cell death or apoptosis in rat pituitary GH3 cells. We examined the expression levels of CaBP-9k mRNA by RT-PCR and immunoblot analysis, and further measured protein levels of p53, Bax, and Bcl-2 by immunoblot analysis, and kit-8 cell survival marker by cell counting following mRNA or protein isolation by Trizol reagent or Proprep solution, respectively. CaBP-9k expression was increased by melatonin in a dose-dependent (0, 0.1, 0.25, 0.5, and 1 mm) and time-dependent (1 to 48 h) manner, indicating that CaBP-9k expression may be related to melatonin receptor-mediated signal transduction in these cells. Cell death increased about 10% in H2O2 (0.25 mm) plus melatonin (1 mm) compared with treatment with only H2O2 (0.25 mm) or H2O2 (0.25 mm) plus melatonin (0.5 mm), and CaBP-9k expression was augmented by this treatment with H2O2 (0.25 mm) plus melatonin (1 mm). This suggests that the mechanism between the increase in cell death and melatonin-induced CaBP-9k expression may be involved in apoptosis by hydrogen peroxide. Bax as a cell death marker was detected in cell death condition of H2O2 (0.25 mm) or H2O2 (0.25 mm) plus melatonin (0.5 or 1 mm), whereas Bcl-2 as a survival marker was identified in the culture condition with melatonin (0.5 or 1 mm) or H2O2 (0.25 mm) plus melatonin (1 mm). p53 as a stress marker mediated with calcium change was decreased in the melatonin only treatment or H2O2 plus melatonin. This result is in agreement with CaBP-9k expression level. Knockdown of CaBP-9k using its siRNA (5′GAGCG CTAAG AAATC TCCCG AAGAA3′, Invitrogen Life Technologies) showed that the reduction of H2O2-induced cell death, suggesting that induction of CaBP-9k expression caused by melatonin is associated with H2O2-induced cell death in rat pituitary GH3 cells.
The skin is a site of melatonin synthesis, and melatonin has a role in protecting against ultraviolet radiation-induced damage. Ultraviolet B (UVB) induced erythema seems to vary between morning and evening. We investigated whether epidermal melatonin immunoreactivities in the morning differed from those in the evening, and whether UVB-induced erythema was associated with these melatonin immunoreactivities in healthy volunteers. Erythema sensitivity of the skin was determined in the morning and in the evening by scoring the Minimal Erythema Dose and quantifying the erythema index (EI). We took biopsies from the non-UVB-exposed skin of healthy volunteers (n = 39) in the morning and in the evening to study melatonin immunoreactivity with immunohistochemistry (IHC). In the IHC staining, there was more melatonin immunoreactivity in the evening than in the morning (p < .001). Erythema was more pronounced in the evening than in the morning irradiated skin (p < .001). The graded amount of melatonin immunoreactivity in the samples was not associated with the EI. We discovered melatonin immunoreactivity of the non-irradiated skin to vary diurnally. However, endogenous skin melatonin does not seem to be the reason why NB-UVB induces more erythema in the evening than in the morning.
Oncogenes alters metabolic pathways while the resulted metabolites, in turn, modifies the expression and production of oncogenes or tumor suppressors. Metabolic reprogramming has been considered as a consequence of oncogenes’ activity more than a phenotypic change of cancer cells. Currently, three different metabolic alterations for cancer cells, i.e. an increased ability to acquire nutrients, preferred metabolic pathways or differentiation pathways, have been described. Melatonin is a molecule which has been extensively investigated since it was discovered more than 60 years ago. From the aggregation of melanophores to antioxidant chain reactions, melatonin has been proposed to be an important molecule affecting the physiology of mammals but also the biology of unicellular organisms. Thus, the decrease in melatonin synthesis in humans with age has been related to several diseases including neurodegeneration and cancer. For many years, it has been believed that melatonin crosses biological membranes easily to exert its functions. However, this notion has been challenged by recent discovery that majority of melatonin might cross biological membranes through glucose transporters. This initial observation has generated a new important idea about melatonin’s function, that is, the membrane transportation of melatonin and glucose by the same transporter in cancer cells would be a new promising mechanism of this indole by either reprogramming glucose metabolism, impeding nutrients uptake or assigning preferred metabolic pathways in cancer cells. In this review, we will focus the role of melatonin as an antiproliferative agent, and its connection with metabolic changes due to melatonin competition with glucose.
Importance:
A "mystery" illness striking US and Canadian diplomats to Cuba (and now China) "has confounded the FBI, the State Department and US intelligence agencies." Sonic explanations for the so-called "health attacks" have long dominated media reports, propelled by peculiar sounds heard and auditory symptoms experienced. Sonic mediation was justly rejected by experts. We assessed whether pulsed radiofrequency/microwave radiation (RF/MW) exposure can accommodate reported facts in diplomats, including unusual ones.
Observations:
1. Noises: Chirping, ringing or grinding noises were heard at night, during episodes reportedly triggering health problems, by many diplomats. Pulsed RF/MW engenders just these "sounds" via the "Frey effect." Ability to hear the sounds depends on high frequency hearing and low ambient noise. "Sounds" differ by head dimensions. 2. Signs/symptoms: Hearing loss and tinnitus are prominent in affected diplomats - and in RF/MW-affected individuals. Each of protean symptoms that diplomats report, also affect persons reporting symptoms from RF/MW: Sleep problems, headaches, and cognitive problems dominate in both groups. Sensations of pressure or vibration figure in each. Both encompass vision, balance and speech problems, and nosebleeds. Brain injury and brain swelling are reported in both. 3. Mechanisms: Oxidative stress provides a documented mechanism of RF/MW injury compatible with reported signs and symptoms; sequelae of endothelial dysfunction (yielding blood flow compromise), membrane damage, blood brain barrier disruption, mitochondrial injury, apoptosis, and autoimmune triggering afford downstream mechanisms, of varying persistence, that merit investigation. 4. Of note, microwaving of the US embassy in Moscow is historically documented.
Conclusions and relevance:
Reported facts appear consistent with RF/MW as the source of injury in Cuba diplomats. Non-diplomats citing symptoms from RF/MW, often with an inciting pulsed-RF/MW exposure, report compatible health conditions. Under the RF/MW hypothesis, lessons learned for diplomats and for RF/MW-affected "civilians" may each aid the other.
Melatonin, a neuroindole mainly produced by the pineal gland, has antioxidant, antiproliferative and anti-inflammatory properties which can be responsible to its beneficial effects on human health. It is well known that melatonin serum levels are reduced in cancer patients since late 80'ies and its role on the growth of cancer cells has been clearly demonstrated. Melatonin directly inhibits the growth of several cell types from diverse embryological origins including breast, prostate, melanoma, lung, kidney or brain; additionally, melatonin is a modulator of the immune function. Physiologically, melatonin administration results in a functional enhancement of immune cells which might play a key role against cancer cells in vivo. In fact, there is a direct crosstalk between the pineal gland and the immune system in several ways. Previous data suggest that the increase in circulating tumor necrosis factor-alpha (TNFα), after a defense response transiently blocks nocturnal melatonin production. In fact, the transcription of arylalkylamine-N-acetyltransferase, the rate-limiting enzyme in melatonin biosynthesis, together with the synthesis of the melatonin precursor N-acetylserotonin, was inhibited by TNFα. It is also clear that cytokine production caused by infection or inflammation, including TNFα, is reduced by melatonin pretreatment. The remarkable ability of TNFα to inhibit the growth of malignant tumor cells is unfortunately limited by its systemic toxicity. New strategies are being tested in order to reduce TNFα toxicity without losing its antitumor efficiency. On the other hand TNFα, induced by a wide range of pathogenic stimuli induces other inflammatory mediators and proteases that act as tumor promoters. The role of TNF in cancer has been linked to all steps of carcinogenesis including carcinogenesis, cellular transformation, promotion, survival, proliferation, angiogenesis and metastasis and how the cytokine works in this intricate link is actually a matter of debate. Since melatonin has been claimed to prevent the toxicity of several anticancer drugs and more recently, to enhance the toxicity of TNFα in cancer cells, we will discuss here the innovative idea of the employment of melatonin in combination with TNFα in cancer treatments. The possible use of melatonin in preventing the toxicity of TNFα without losing its antitumor properties as well as its capacity to promote ability to kill cancer cells especially resistant to TNFα treatment is an idea which needs to be deeply explored.
Despite great scientific breakthroughs toward understanding the identity of human hepatocellular carcinoma (HCC) mechanistically, there are still no clinically efficient therapeutic methods for this cancer. Melatonin (N‐acetyl‐5‐methoxytryptamine) is a multi‐tasking hormone that has long been known for its anti‐cancer activity against various human cancers including HCC, which is a focus of this review. PubMed database was searched for relevant articles with the keywords: hepatocellular carcinoma (HCC), melatonin, apoptosis, proliferation, invasion, angiogenesis, autophagy, oxidative stress, tumor immunity, and mitogen‐activated protein kinase (MAPK) focusing on just human cell lines and English language articles. Melatonin inhibits apoptosis resistance and activates both extrinsic and intrinsic pathways of apoptosis in HCC. Melatonin induces ensoplasmic reticulum (ER)‐ and autophagy‐mediated apoptosis in cancer cells. Melatonin works against cancer cell proliferation, motility, and invasiveness by modulating actions of a variety of transcription factors and related pathways. Melatonin also relieves an immunosuppressive state in HCC cancer cells through making a control over tumor‐derived exosomes. Both pro‐and anti‐oxidative functions of melatonin are necessary for combating HCC. Combination of melatonin with chemotherapy could also provide cumulative effects on cancer cells. Melatonin exerts most of these roles by acting on the members of MAPK family. Melatonin (N‐acetyl‐5‐methoxytryptamine) has been known for its anti‐cancer activity against HCC in clinical trials. It could be speculate that application of melatonin is regarded as a promising choice for combating HCC in human subjects due to some virtues, including multifunctionality, versatile ability through modulation of two diverse functions, and its potential to provide cumulative effects in combination therapies.
The androgen receptor (AR) plays a key role in the development and progression of prostate cancer (CaP). Since the mid-1990s, reports in the literature pointed out higher incidences of CaP in some select groups, such as airline pilots and night shift workers in comparison to those working regular hours. The common finding in these 'high-risk' groups was that they all experienced a deregulation of the body's internal circadian rhythm. Here we discuss how the circadian rhythm affects androgen levels and modulates CaP development and progression. Circadian rhythmicity of androgen production is lost in CaP patients, with the clock genes Per1 and Per2 decreasing, and Bmal1 increasing, in these individuals. Periodic expression of the clock genes was restored upon administration of the neurohormone melatonin, thereby suppressing CaP progression. Activation of the melatonin receptors and the AR antagonized each other, and therefore the tumor suppressive effects of melatonin and the clock genes were most clearly observed in the absence of androgens, that is, in conjunction with androgen deprivation therapy (ADT). In addition, a large-scale study found that high-dose radiation was more effective in CaP patients when it was delivered before 5PM, compared to those delivered after 5PM, suggesting that the therapy was more effective when delivered in synchrony with the patient's circadian clock. As CaP patients are shown to become easily resistant to new therapies, perhaps circadian delivery of these therapeutic agents or delivery in conjunction with melatonin and its novel analogs should be tested to see if they prevent this resistance.
Objective To evaluate the efficacy and safety of melatonin as an adjuvant therapy for the tumor patients receiving chemotherapy or radiotherapy. Methods Such databases as MEDLINE (1980 to Jan. 2010), Te Cochrane Library (Issue 4, 2009), Wan Fang Data (1980 to Jan. 2010), CBM (1980 to Jan. 2010), CNKI (1980 to Jan. 2010), ELSEVIER Science Direct (SDOS, 1980 to Jan. 2010), Nature (1980 to Jan. 2010) and ongoing clinical trials (www.clinicaltrials.gov and www. controlled-trials.com) were searched to collect randomized controlled trials (RCTs). The data were extracted and the quality of the included RCTs was assessed by two reviewers. Then meta-analyses were performed by using Stata 10.1 software. Results Eight RCTs were included. The results of meta-analyses showed that melatonin significantly improved the remission rate for tumor patients (RR=1.98, 95% CI 1.52 to 2.58) and the one-year survival rate (RR=1.90, 95%CI 1.28 to 2.83), and significantly reduced the toxic effects of bone marrow suppression caused by chemotherapy or radiotherapy (RR=0.12, 95%CI 0.06 to 0.27). No reports of adverse events were associated with melatonin. Conclusion The existing evidence reveals that the melatonin, as an adjuvant therapy drug for tumor, plays a certain role in improving disease remission rate, reducing the toxicity of chemotherapy and radiotherapy, and prolonging the life. It requires more high-quality RCTs for further verification because of the limitation of the included studies.
Melatonin, an indolamine derived from the amino-acid tryptophan via synthesis of serotonin, is secreted by the pineal gland in cyclical periods. In mammals, melatonin is involved in physiological processes, such as sleep/wake regulation in the circadian cycle. It has antioxidant oncostatic and anti-inflammatory properties, functions as an immunomodulator, and stimulates bone metabolism. In particular, the antitumor effects of melatonin, have been studied in multiple cancer cell types including melanoma, breast and prostate cancer, lymphoma, ovarian and colorectal cancer. This chapter summarizes the numerous observations about melatonin anticancer effects in both in vivo and in vitro studies published in recent years as well as the action mechanisms of melatonin involved in its anticarcinogenic activity focusing on the signalling pathways that regulate programmed cell death. In the majority of studies, melatonin has shown to inhibit development and/or growth of various experimental animal tumors and human cancer cell lines in vitro promoting apoptosis in contrast to the obvious inhibition of apoptotic processes in normal cells (focused in immune cells and neurons). Furthermore, if melatonin uniformly induced apoptosis in cancer cells, the findings could have important clinical utility given that many tumors show resistance to drug treatment due to their resistance to undergo apoptosis. © 2012 Springer Science+Business Media Dordrecht. All rights are reserved.
Aim: To investigate the anti-proliferative activities of melatonin (MT) and its influence on NF-κB level in HeLa cells. Methods: The anti-proliferative activities of MT were evaluated by MTT assay and AO/EB staining, and NF-κB level was observed by Western blot analysis. Results: The IC50 on HeLa cells by MT for 72 h was 61.71 mg·L -1. HeLa cells stained with AO/EB were damaged in a time-dependent manner by MT 1 g·L-1 for 1 d,2 d and 3 d. As the time goes on, more necrocytosis were seen and less apoptosis were observed. It was shown that MT could down-regulate NF-κB level in a time-dependent and a dose-dependent manner after treated with MT 0.2 g· L-1 for 1 d,2 d and 3 d and with MT 0.008, 0.04 and 0.2 g·L-1 for 3 days. Conclusion MT could inhibit the proliferation of HeLa cells with a concomitant down-regulation of NF-κB level, which may be related to its antiproliferative activity.
Background: Our previous studies have demonstrated that melatonin inhibits the adipogenic differentiation of bone marrow mesenchymal stem cells. However, the mechanism underlying the effect of melatonin on adipogenesis is still unknown. Objective: To determine whether melatonin can inhibit the adipogenesis of bone marrow mesenchymal stem cells through retinoid-related orphan receptor α. Methods: Bone marrow mesenchymal stem cells were isolated and purified by density gradient centrifugation combined with cell attachment culture. The phenotype was investigated by flow cytometry. Then, cells were induced for adipogenic differentiation with melatonin, CGP52608 and normal adipose tissue, respectively. The levels of retinoid-related orphan receptor α mRNA and protein were investigated by real-time RT-PCR and western blot assay, respectively. Further, the effect of retinoid-related orphan receptor α on the dipogenic differentiation of bone marrow mesenchymal stem cells was investigated by CGP52608. Results and Conclusion: The primary isolated bone marrow mesenchymal stem cells were spindle-shaped fibroblast-like cells. These cells did not express hematopoietic stem cells markers: CD34 and CD45; and highly expressed MSC markers: CD29, CD44, and CD10. The result of RT-PCR demonstrated that melatonin nuclear receptor, retinoid-related orphan receptor α, was highly expressed in bone marrow mesenchymal stem cells and the expression of retinoid-related orphan receptor α was further enhanced by melatonin in a dose-dependent manner, which was confirmed at protein level by western blot assay. During adiogenesis, the expression of retinoid-related orphan receptor α mRNA was up-regulated in the early stage, but maintained at a low level in the mild-later stage. While the retinoid-related orphan receptor α was activated by agonist CGP52608, the adipogenic differentiation of bone marrow mesenchymal stem cells was inhibited, which was similar to the inhibitory effect of melatonin. Therefore, melatonin inhibited the adipogenic differentiation of bone marrow mesenchymal stem cells through retinoid-related orphan receptor α, suggesting that melatonin plays an important role in the differentiation of adipocytes.
In children with sleep‐onset insomnia and delayed dim‐light melatonin onset, melatonin treatment not only improves sleep but also health, behavior and parenting stress. The aim of the present study was to see whether the latter effects are dependent on the direct effects on sleep. Data come from 41 children (24 boys, 17 girls; mean age = 9.43 years). They entered melatonin treatment (1–5 mg per day) for three weeks, then discontinued treatment by first taking a half dose for one week, and then stopped completely for another week. Sleep was measured with sleep diaries filled in by parents and with actometers. We found a positive effect of actual sleep duration on health but this disappeared after discontinuing treatment. We also found that melatonin treatment decreased behavior problems, which effect appeared to be stronger for children with an earlier dim‐light melatonin onset. These results show that the melatonin effects on health and behavior problems may partly be dependent on sleep.
Melatonin is known to exert antitumor activity in several types of human cancers, but the underlying mechanisms as well as the efficacy of different doses of melatonin are not well defined. Here, we test the hypothesis whether melatonin in the nanomolar range is effective in exerting antitumor activity in vivo, and examine the correlation with the hypoxia signaling mechanism, which may be a major molecular mechanism by which melatonin antagonizes cancer. To test this hypothesis, LNCaP human prostate cancer cells were xenografted into seven-week old Foxn1nu/nu male mice that were treated with melatonin (18 i.p. injections of 1 mg/kg in 41 days). Saline-treated mice served as control. We found that the melatonin levels in plasma and xenografted tissue were 4x and 60x higher, respectively, than in control samples. Melatonin tended to restore the redox imbalance by increasing expression of Nrf2. As part of the phenotypic response to these perturbations, xenograft microvessel density was less in melatonin-treated animals, indicative of lower angiogenesis, and the xenograft growth rate was slower (P<0.0001). These changes were accompanied by a reduced expression of Ki67, elevated expression of HIF-1α and increased phosphorylation of Akt in melatonin than saline-treated mice. We conclude that the beneficial effect of melatonin in reducing cancer growth in vivo was evident at melatonin plasma levels as low as 4 nM, and was associated to decreased angiogenesis. Higher HIF-1α expression in xenograft tissue indicates that the antitumor effect cannot be due to a postulated anti-hypoxic effect, but may stem from lower angiogenesis potential.This article is protected by copyright. All rights reserved.
It is well established that melatonin exerts antitumoral effects in many cancer types, mostly decreasing cell proliferation at low concentrations. On the other hand, induction of apoptosis by melatonin has been described in the last few years in some particular cancer types. The cytotoxic effect occurs after its administration at high concentrations, and the molecular pathways involved have been only partially determined. Moreover, a synergistic effect has been found in several cancer types when it is administered in combination with chemotherapeutic agents. In the present review, we will summarize published work on the pro-apoptotic effect of melatonin in cancer cells and the reported mechanisms involved in such action. We will also construct a hypothesis on how different cell signaling pathways may relate each other on account for such effect.
Background:
Melatonin shows potential oncostatic action, and light exposure during night suppresses melatonin production. There is little information, however, about the direct effect of night work on the risk of cancer. We investigated the effect of night work in breast cancer.
Methods:
We examined the relationship between breast cancer and working on rotating night shifts during 10 years of follow-up in 78 562 women from the Nurses' Health Study. Information was ascertained in 1988 about the total number of years during which the nurses had worked rotating night shifts with at least three nights per month. From June 1988 through May 1998, we documented 2441 incident breast cancer cases. Logistic regression models were used to calculate relative risks (RRs) and 95% confidence intervals (CIs), adjusted for confounding variables and breast cancer risk factors. All statistical tests were two-sided.
Results:
We observed a moderate increase in breast cancer risk among the women who worked 1-14 years or 15-29 years on rotating night shifts (multivariate adjusted RR = 1.08 [95% CI = 0.99 to 1.18] and RR = 1.08 [95% CI = 0.90 to 1.30], respectively). The risk was further increased among women who worked 30 or more years on the night shift (RR = 1.36; 95% CI = 1.04 to 1.78). The test for trend was statistically significant (P =.02).
Conclusions:
Women who work on rotating night shifts with at least three nights per month, in addition to days and evenings in that month, appear to have a moderately increased risk of breast cancer after extended periods of working rotating night shifts.
Melatonin, the chief hormone secreted by the pineal gland, has been previously shown to inhibit human breast cancer cell growth at the physiological concentration of 1 nM in vitro. In this study, using the estrogen receptor (ER)-positive human breast tumor cell line MCF-7, we have shown that 10 microM L-buthionine-[S,R]-sulfoximine (L-BSO), an inhibitor of gamma-glutamylcysteine synthetase (the rate-limiting enzyme in glutathione synthesis), blocks the oncostatic action of 1 nM melatonin over a 5-day incubation, indicating that glutathione is required for melatonin action. The result was repeated with ZR75-1 cells, suggesting that the glutathione requirement is a general phenomenon among ER+ breast cancer cells. Addition of exogenous glutathione (1 microM) to L-BSO-treated groups restored the melatonin response in both cell lines. Further demonstration of the importance of glutathione was shown using the ER- breast tumor cell line HS578T, which is normally unresponsive to melatonin. Growth in this cell line was inhibited in the presence of 1 microM ethacrynic acid (an inhibitor of glutathione S-transferase) plus 1 nM melatonin, and this effect was blocked with 10 microM L-BSO. We also observed a steady decrease of intracellular glutathione in MCF-7 cells over a 5-day incubation, suggesting that these cells metabolize glutathione differently than do normal cells.
The prostate is an androgen-regulated organ, which has led to long-standing interest in the role of androgens in prostate carcinogenesis. Although evidence of a hormonal etiology for prostate cancer is strong, it is almost entirely circumstantial. Much of the problem in proving a causal relationship relates to the continued difficulties in reliably measuring human tissue-specific exposure to endogenous steroid hormones. The international and racial-ethnic variations in prostate cancer incidence, combined with the effects of migration on risk patterns, have suggested that whereas environmental factors are likely to be important, genetic factors might also play a central role in determining prostate cancer risk. We are developing a polygenic model of prostate carcinogenesis focused around a series of genes involved in androgen biosynthesis and androgen activation, transport, and metabolism in the prostate. In this developing model, we have initially targeted four genes based on three main criteria: (a) all encode products that play important roles in inducing androgen stimulation in the prostate; (b) all are polymorphic; and (c) all show substantial allelic variation in the polymorphic marker among the racial-ethnic groups of greatest interest in terms of prostate cancer risk. In addition to studying how the polymorphic markers of interest are related to prostate cancer development within and between racial-ethnic groups, we are concurrently evaluating whether genotypic variations correlate in the anticipated direction with biochemical parameters in vitro and in vivo. We summarize the development of this model and the state of knowledge related to each of the genes comprising the current model. We discuss the extent to which the current model can explain demographic variation in prostate cancer risk as well as the potential for future expansion of the model to incorporate environmental risk factors as well as additional genes. The model, when fully developed, can potentially provide a basis for targeting populations for screening interventions and/or preventive strategies aimed at the multigene products or at the genes themselves.
Previous studies have suggested that male hormones (androgens) and certain forms of oxygen (reactive oxygen species) are linked to the development of prostate cancer. We hypothesized that androgens contribute to prostate carcinogenesis by increasing oxidative stress. We further hypothesized that antioxidants reduce prostate cancer risk by modulating androgen effects on cellular processes.
To test these hypotheses, we looked for 1) a change in the level of reactive oxygen species in the presence of androgens, 2) androgen-induced binding activity of transcriptional activators AP-1 and NF-kappaB, whose activities are known to be altered during cell proliferation, and 3) the effect of antioxidants on androgen-induced transcription factor binding.
Physiologic concentrations (1 nM) of 5alpha-dihydrotestosterone or 1-10 nM R1881, a synthetic androgen, produced sustained elevation of AP-1 and NF-kappaB DNA-binding activity in LNCaP cells, an androgen-responsive human prostate carcinoma cell line. Androgen-independent DU145 cells (another human prostate carcinoma cell line) were unaffected by R1881 treatment. AP-1-binding activity increased 5 hours after 1 nM R1881 treatment; NF-kappaB DNA-binding activity increased after 36 hours. Both activities remained elevated for at least 120 hours. Nuclear AP-1 and NF-kappaB protein levels were not elevated. Antioxidant vitamins C plus E blocked both androgen-induced DNA-binding activity and production of reactive oxygen species.
Physiologic concentrations of androgens induce production of reactive oxygen species and cause prolonged AP-1 and NF-kappaB DNA-binding activities, which are diminished by vitamins C and E.
The growth of rat hepatoma 7288CTC in vivo is stimulated by the uptake of linoleic acid (LA) and its metabolism to 13-hydroxyoctadecadienoic acid (13-HODE), an important mitogenic signaling molecule within this tumor. Conversely, the growth of a variety of experimental cancers in vivo is inhibited by either physiological or pharmacological levels of the pineal gland hormone melatonin, although the mechanism(s) are unknown. We tested the hypothesis that the mechanism of melatonin's anticancer action in vivo involves the inhibition of tumor LA uptake and metabolism to 13-HODE in hepatoma 7288CTC. Tumor uptake of LA and release of 13-HODE, measured in tissue-isolated rat hepatoma 7288CTC at 4-h intervals over a 24-h period, were highest during the light phase and lowest during the mid-dark phase, when plasma melatonin levels were lowest and highest, respectively. Pinealectomy eliminated this rhythm of tumor LA uptake and 13-HODE production, indicating that it was driven by the circadian melatonin rhythm. Perfusion of tissue-isolated tumors in situ with melatonin (1 nM) rapidly and reversibly inhibited the uptake of plasma fatty acids (FAs), including LA, and its metabolism to 13-HODE. These inhibitory effects of melatonin on tumor FA uptake and 13-HODE release were completely reversed by perfusion of tumors in situ with melatonin receptor antagonist S-20928, pertussis toxin, forskolin, or 8-bromo-cAMP. Perfusion of tumors in situ with melatonin also decreased tumor [3H]thymidine incorporation and DNA content; these effects on DNA synthesis were also prevented by the coperfusion of tumors with melatonin and S-20928, pertussis toxin, forskolin, 8-Br-cAMP, or 13-HODE. Pinealectomy stimulated tumor growth, LA uptake and metabolism to 13-HODE, and FA storage in hepatoma 7288CTC, whereas melatonin administration (200 microg/day) was inhibitory in vivo. Northern blot analysis revealed that, compared with normal liver tissue, hepatoma 7288CTC overexpressed mRNA transcripts for a plasma membrane-associated FA transport protein (FATP). FATP mRNA expression was unaffected by the treatment of tumor-bearing rats with daily afternoon melatonin injections or exposure to constant light. These results support a novel mechanism of tumor growth inhibition by melatonin involving a melatonin receptor-mediated suppression of cAMP levels, resulting in diminished tumor FA transport, possibly via decreased FATP function. The inhibition of these signal transduction events by melatonin culminates in the suppression of LA uptake, LA metabolism to the mitogenic signaling molecule 13-HODE, and cancer growth.
Apoptotic pathways controlled by the Rel/NF-kappaB family of transcription factors may regulate the response of cells to DNA damage. Here, we have examined the NF-kappaB status of several prostate tumor cell lines. In the androgen-independent prostate tumor cells PC-3 and DU-145, the DNA-binding activity of NF-kappaB was constitutively activated and IkappaB-alpha levels were decreased. In contrast, the androgen-sensitive prostate tumor cell line LNCaP had low levels of NF-kappaB which were upregulated following exposure to cytokines or DNA damage. The activity of the IkappaB-alpha kinase, IKKalpha, which mediates NF-kappaB activation, was also measured. In PC-3 cells, IKKalpha activity was constitutively active, whereas LNCaP cells had minimal IKKalpha activity that was activated by cytokines. The anti-inflammatory agent ibuprofen inhibited the constitutive activation of NF-kappaB and IKKalpha in PC-3 and DU-145 cells, and blocked stimulated activation of NF-kappaB in LNCaP cells. However, ibuprofen did not directly inhibit IkappaB-alpha kinase. The results demonstrate that NF-kappaB is constitutively activated in the hormone-insensitive prostate tumor cell lines PC-3 and DU-145, but not in the hormone responsive LNCaP cell line. The constitutive activation of NF-kappaB in prostate tumor cells may increase expression of anti-apoptotic proteins, thereby decreasing the effectiveness of anti-tumor therapy and contributing to the development of the malignant phenotype.
While the role of nuclear transcription factor activator protein-1 (AP-1) in cell proliferation, and of nuclear factor-kappaB (NF-kappaB) in the suppression of apoptosis are known, their role in survival of prostate cancer cells is not well understood. We investigated the role of NF-kappaB and AP-1 in the survival of human androgen-independent (DU145) and -dependent (LNCaP) prostate cancer cell lines. Our results show that the faster rate of proliferation of DU145 cells when compared to LNCaP cells correlated with the constitutive expression of activated NF-kappaB and AP-1 in DU-145 cells. The lack of constitutive expression of NF-kappaB and AP-1 in LNCaP cells also correlated with their sensitivity to the antiproliferative effects of tumor necrosis factor (TNF). TNF induced NF-kappaB activation but not AP-1 activation in LNCaP cells. In DU145 cells both c-Fos and c-Jun were expressed and treatment with TNF activated c-Jun NH2-terminal kinase (JNK), needed for AP-1 activation. In LNCaP cells, however, only low levels of c-Jun was expressed and treatment with TNF minimally activated JNK. Treatment of cells with curcumin, a chemopreventive agent, suppressed both constitutive (DU145) and inducible (LNCaP) NF-kappaB activation, and potentiated TNF-induced apoptosis. Curcumin alone induced apoptosis in both cell types, which correlated with the downregulation of the expression of Bcl-2 and Bcl-xL and the activation of procaspase-3 and procaspase-8. Overall, our results suggest that NF-kappaB and AP-1 may play a role in the survival of prostate cancer cells, and curcumin abrogates their survival mechanisms.
Melatonin is a pineal hormone that strongly inhibits the growth of breast cancer cells in vitro and in vivo. We report thefirst use of immunohistochemical analysis to determine the distribution of the high-affinity melatonin receptor subtype, MTI, in human breast tissue, the hypothalamic suprachiasmatic nucleus, and skin. The MT1 antibody, which is specific for the cytoplasmic portion of the receptor, produced cytoplasmic staining in normal-appearing breast epithelial cells and ductal carcinoma cells; stromal cells, myoepithelial cells, and adipocytes were nonreactive. The majority of nonneoplastic samples (13/19 [68%]) were negative to weakly positive, while moderate to strong reactivity was seen in most cancer samples (49/65 [75%]). Thus, although MT1 receptors were detectable in normal and malignant breast epithelium, high receptor levels occurred more frequently in tumor cells (P < .001), and tumors with moderate or strong reactivity were more likely to be high nuclear grade (P < .045). These findings may have implications for the use of melatonin in breast cancer therapy.
Melatonin (N-acetyl-5-methoxytryptamine) is a molecule with a very wide phylogenetic distribution from plants to man. In vertebrates, melatonin was initially thought to be exclusively of pineal origin recent studies have shown, however, that melatonin synthesis may occur in a variety of cells and organs. The concentration of melatonin within body fluids and subcellular compartments varies widely, with blood levels of the indole being lower than those at many other sites. Thus, when defining what constitutes a physiological level of melatonin, it must be defined relative to a specific compartment. Melatonin has been shown to have a variety of functions, and research in the last decade has proven the indole to be both a direct free radical scavenger and indirect antioxidant. Because of these actions, and possibly others that remain to be defined, melatonin has been shown to reduce the toxicity and increase the efficacy of a large number of drugs whose side effects are well documented. Herein, we summarize the beneficial effects of melatonin when combined with the following drugs: doxorubicin, cisplatin, epirubicin, cytarabine, bleomycin, gentamicin, ciclosporin, indometacin, acetylsalicylic acid, ranitidine, omeprazole, isoniazid, iron and erythropoietin, phenobarbital, carbamazepine, haloperidol, caposide-50, morphine, cyclophosphamide and L-cysteine. While the majority of these studies were conducted using animals, a number of the investigations also used man. Considering the low toxicity of melatonin and its ability to reduce the side effects and increase the efficacy of these drugs, its use as a combination therapy with these agents seems important and worthy of pursuit.
It is well known that intracellular antioxidant glutathione (GSH) plays major roles in the maintenance of redox status and defense of oxidative stress. Ras, a small GTP-binding protein, may send growth-stimulating message to the nucleus through downstream Rac oncoprotein and superoxide (O(2*-)). These findings led us to investigate the effects of GSH and melatonin, a free-radical scavenger, on Ras-Rac-O(2*-)-related growth signal transduction. Our results demonstrate that overexpression of the inducible Ha-ras oncogene by isopropyl-beta-D-thiogalactoside (IPTG) increases the levels of reactive oxygen species (ROS, including O(2*-) and hydrogen peroxide (H(2)O(2))) and GSH in an Ha-ras-transformed NIH/3T3 fibroblast cell line. On the contrary, melatonin significantly suppresses ras-triggered cell growth by inhibiting the increase of ROS and GSH. Moreover, severe apoptosis of this transformed cell line occurred when the cell redox balance between ROS and GSH was dramatically changed in the presence of IPTG and L-buthionine-[S,R]-sulfoximine (BSO, a specific inhibitor of GSH synthetase). That BSO-induced cell apoptosis needs Ras to increase the ROS level was demonstrated by the free-radical scavenger melatonin. It effectively blocked cell apoptosis, but cell growth was also slowed without affecting Ras expression. Based on our studies, two approaches can be applied to treating ras-related cancers. One is utilizing melatonin to suppress cancer cell proliferation, and the other is utilizing BSO to induce cancer-cell apoptosis. Cotreatment of ras-related cancer cells with melatonin and BSO stops cell growth as well as apoptosis. Whether these cancer cells will undergo further regression or become recurrent merits investigation.
Antioxidant enzymes are critical in oxidative stress responses. Radioresistant variants isolated from MCF-7 human carcinoma cells following fractionated ionizing radiation (MCF+FIR cells) or overexpression of manganese superoxide dismutase (MCF+SOD cells) demonstrated dose-modifying factors at 10% isosurvival of 1.8 and 2.3, respectively. MCF+FIR and MCF-7 cells (exposed to single-dose radiation) demonstrated 5- to 10-fold increases in MnSOD activity, mRNA, and immunoreactive protein. Radioresistance in MCF+FIR and MCF+SOD cells was reduced following expression of antisense MnSOD. DNA microarray analysis and immunoblotting identified p21, Myc, 14-3-3 zeta, cyclin A, cyclin B1, and GADD153 as genes constitutively overexpressed (2- to 10-fold) in both MCF+FIR and MCF+SOD cells. Radiation-induced expression of these six genes was suppressed in fibroblasts from Sod2 knockout mice (-/-) as well as in MCF+FIR and MCF+SOD cells expressing antisense MnSOD. Inhibiting NF-kappa B transcriptional activity in MCF+FIR cells, by using mutant I kappa B alpha, inhibited radioresistance as well as reducing steady-state levels of MnSOD, 14-3-3 zeta, GADD153, cyclin A, and cyclin B1 mRNA. In contrast, mutant I kappa B alpha was unable to inhibit radioresistance or reduce 14-3-3 zeta, GADD153, cyclin A, and cyclin B1 mRNAs in MCF+SOD cells, where MnSOD overexpression was independent of NF-kappa B. These results support the hypothesis that NF-kappa B is capable of regulating the expression of MnSOD, which in turn is capable of increasing the expression of genes that participate in radiation-induced adaptive responses.
Exposure to light at night suppresses the physiologic production of melatonin, a hormone that has antiproliferative effects
on intestinal cancers. Although observational studies have associated night-shift work with an increased risk of breast cancer,
the effect of night-shift work on the risk of other cancers is not known. We prospectively examined the relationship between
working rotating night shifts and the risk of colorectal cancers among female participants in the Nurses’ Health Study. We
documented 602 incident cases of colorectal cancer among 78 586 women who were followed up from 1988 through 1998. Compared
with women who never worked rotating night shifts, women who worked 1–14 years or 15 years or more on rotating night shifts
had multivariate relative risks of colorectal cancer of 1.00 (95% confidence interval [CI] = 0.84 to 1.19) and 1.35 (95% CI
= 1.03 to 1.77), respectively (Ptrend = .04). These data suggest that working a rotating night shift at least three nights per month for 15 or more years may increase
the risk of colorectal cancer in women.
There is an increasing interest in identifying potent cancer preventive and therapeutic agents against prostate cancer (PCA). In a recent study, we showed that a polyphenolic fraction isolated from grape seeds (hereafter referred to as GSP) that is substantially rich in antioxidant procyanidins exerts exceptionally high preventive effects against tumorigenesis in a murine skin model. In the present study, we investigated the anticarcinogenic effect of GSP against PCA by employing DU145 human prostate carcinoma cells. GSP treatment (10–100 μg/mL doses for 2–6 d) of cells resulted in a highly significant (P < 0.01–0.001) inhibition of cell growth in both dose‐ and time‐dependent manner. Compared with the vehicle, 2 d of GSP treatment resulted in 27, 39, and 76% growth inhibition at 50, 75, and 100 μg/mL doses, respectively, whereas 28–97% and 12–98% inhibition was evident at 10–100 μg/mL doses of GSP after 4 and 6 d of treatment, respectively. These doses of GSP also resulted in dose‐ and time‐dependent cell death (6–50%, P <0.1–0.001) that was later characterized as apoptotic death. In molecular mechanistic studies, treatment of DU145 cells with GSP at 25–75 μg/mL doses for 24, 48, and 72 h resulted in 77–88%, 65–93%, and 38–98% reduction, respectively (P < 0.001), in phospho–extracellular signal‐regulated protein kinase (ERK) 1 and 78%, 19–76%, and 63–71% reduction (P < 0.1–0.001) in phospho‐ERK2 levels, respectively. In other studies, similar doses of GSP showed up to 1.9‐fold increases in Cip1/p21 and a significant (P < 0.001) decrease in cyclin‐dependent kinase (CDK) 4 (up to 90% decrease), CDK2 (up to 50% decrease), and cyclin E (up to 60% decrease). GSP treatment of DU145 cells also resulted in a significant (P < 0.001) G1 arrest in cell‐cycle progression in a dose‐dependent manner. The growth‐inhibitory and cell‐death effects of GSP were also observed in another human PCA line, LNCaP. Together, these results suggest that GSP may exert strong anticarcinogenic effect against PCA and that this effect possibly involves modulation of mitogenic signaling and cell‐cycle regulators and induction of G1 arrest, cell‐growth inhibition, and apoptotic death. Mol. Carcinog. 28:129–138, 2000. © 2000 Wiley‐Liss, Inc.
Over the past few years, we have shown that the surge of melatonin in the circulation during darkness represents a potent oncostatic signal to tissue-isolated rat hepatoma 7288CTC, which is an ER+ adenocarcinoma of the liver. This oncostatic effect occurs via a melatonin receptor-mediated suppression of tumor cAMP production that leads to a suppression of the tumor uptake of linoleic acid (1,A), an essential fatty acid with substantial oncogenic properties. The ability of LA to promote cancer progression is accomplished by its intracellular metabolism to 13-hydroxyoctadecadienoic acid (13-HODE) which amplifies the activity of the epidermal growth factor receptor/mitogen-activated protein kinase pathway leading to cell proliferation. By blocking tumor LA uptake, melatonin effectively blocks the production of 13-HODE and thus, markedly attenuates tumor growth. A similar effect of melatonin is observed in tissue-isolated, ER+ MCF-7 human breast cancer xenografts and nitrosomethylurea (NMU)-induced rat mammary cancers. When male rats bearing tissue-isolated hepatomas are exposed either to constant bright light (300 lux) or dim light (0.25 lux) during the dark phase of a 12L:12D photoperiod, the latency to onset was significantly reduced while the growth of tumors was markedly increased over a 4 wk period as compared with control tumors in 12L: 12D-exposed rats. In constant light- and dim light during darkness-exposed rats, melatonin levels were completely suppressed while tumor growth, I A uptake and 13-HODE production were markedly increased. Similar results were obtained in constant bright light-exposed female rats bearing tissue-isolated NMU-induced mammary cancers or MCF-7 human breast cancer xenografts. To date, these studies provide the most definitive experimental evidence that light exposure during darkness increases the risk of cancer progression via elimination of the nocturnal melatonin signal and its suppression of tumor LA uptake and metabolism to 13-HODE.
We have presently determined the effect of inhibition of the DNA repair enzyme poly(ADP-ribose) polymerase (PARP) on the occurrence of apoptosis in insulin-producing cells. The ADP-ribosylation activities of intact cells were decreased by incubation of RINm5F cells for 16 h with the PARP inhibitors nicotinamide (NA) (20-50 mM) or 3-aminobenzamide (3-ABA) (10 mM). Exposure to 20-50 mM NA or 10 mM 3-ABA both resulted in massive apoptosis in RINm5F cells. A 24 h exposure to 50 mM nicotinamide induced apoptosis in fetal but not adult rat islet cells. In addition, exposure of RINm5F cells to 50 mM NA for 12-24 h induced the appearance of the 85 kDa proteolytic PARP fragment, indicating activation of the ICE-like protease caspase-3. Incubation with 20-50 mM NA did not induce any consistent effects upon transcription factor NF-kappaB activity, demonstrating that this pathway is not involved in induction of apoptosis by NA. It is concluded that in insulin-producing cells with a high mitotic rate, inhibition of ADP-ribosylation--and consequently of auto-modification and release of PARP bound to DNA strand breaks--leads to activation of programmed cell death.
Oxidative stress (OS) has been implicated in various degenerative diseases in aging. In an attempt to quantify OS in a cell model, we examined OS induced by incubating for 30 min with various free radical generators in PC12 cells by using the dichlorofluorescein (DCF) assay, modified for use by a fluorescent microplate reader. The nonfluorescent fluorescin derivatives (dichlorofluorescin, DCFH), after being oxidized by various oxidants, will become DCF and emit fluorescence. By quantifying the fluorescence, we were able to quantify the OS. Our results indicated that the fluorescence varied linearly with increasing concentrations (between 0.1 and 1 mM) of H2O2 and 2,2′-azobios(2-amidinopropane) dihydrochloride (AAPH; a peroxyl radical generator). By contrast, the fluorescence varied as a nonlinear response to increasing concentrations of 3-morpholinosydnonimine hydrochloride (SIN-1; a peroxynitrite generator), sodium nitroprusside (SNP; a nitric oxide generator), and dopamine. Dopamine had a biphasic effect; it decreased the DCF fluorescence, thus acting as an antioxidant, at concentrations
It is not clear why on treatment with certain killer cytokines or chemotherapeutic agents, some cells undergo apoptosis while others do not. The delineation of sensitivity/resistance pathways should provide a more specific therapy for cancer and other hyperproliferative diseases. Most cells die either by apoptosis or by necrosis. The biochemical pathway that mediates these two modes of cell death has recently been described. The nuclear factor (NF)-κB and the genes regulated by this transcription factor have been shown to play a critical role in induction of resistance to killer agents. Thus, inhibitors of NF-κB activation have a potential in overcoming resistance to apoptosis induced by various agents. The evidence for and against such a notion is discussed.
Drug resistance, intrinsic or acquired, is a problem for all chemotherapeutic agents. In this review, we examine numerous strategies that have been tested or proposed to reverse drug resistance. Included among these strategies are approaches targeting the apoptosis pathway. Although the process of apoptosis is complex, it provides several potential sites for therapeutic intervention. A variety of targets and approaches are being pursued, including the suppression of proteins inhibiting apoptosis using antisense oligonucleotides (ASOs), and small molecules targeted at proteins that modulate apoptosis. An alternate strategy is based on numerous studies that have documented methylation of critical regions in the genome in human cancers. Consequently, efforts have been directed at re-expressing genes, including genes that affect drug sensitivity, using 5-azacytidine and 2'-deoxy-5-azacytidine (DAC, decitabine) as demethylating agents. While this strategy may be effective as a single modality, success will most likely be achieved if it is used to modulate gene expression in combination with other modalities such as chemotherapy. At a more basic level, attempts have been made to modulate glutathione (GSH) levels. Owing to its reactivity and high intracellular concentrations, GSH has been implicated in resistance to several chemotherapeutic agents. Several approaches designed to deplete intracellular GSH levels have been pursued including the use of buthionine-(S,R)-sulfoxime (BSO), a potent and specific inhibitor of gamma-glutamyl cysteine synthetase (gamma-GCS), the rate-limiting step in the synthesis of GSH, a hammerhead ribozyme against gamma-GCS mRNA to downregulate specifically its levels and targeting cJun expression to reduce GSH levels. Alternate strategies have targeted p53. The frequent occurrence of p53 mutations in human cancer has led to the development of numerous approaches to restore wild-type (wt) p53. The goals of these interventions are to either revert the malignant phenotype or enhance drug sensitivity. The approach most extensively investigated has utilized one of several viral vectors. An alternate approach, the use of small molecules to restore wt function to mutant p53, remains an option. Finally, the conceptually simplest mechanism of resistance is one that reduces intracellular drug accumulation. Such reduction can be effected by a variety of drug efflux pumps, of which the most widely studied is P-glycoprotein (Pgp). The first strategy utilized to inhibit Pgp function relied on the identification of non-chemotherapeutic agents as competitors. Other approaches have included the use of hammerhead ribozymes against the MDR-1 gene and MDR-1-targeted ASOs. Although modulation of drug resistance has not yet been proven to be an effective clinical tool, we have learned an enormous amount about drug resistance. Should we succeed, these pioneering basic and clinical studies will have paved the road for future developments.
The tetrazolium salt (MTT) method involving conversion of MTT to coloured formazan by cells serving as indirect measurements of cell growth/cell kill has been reported by several groups, although technical problems have been encountered. The present investigation was undertaken in order to delineate what laboratory variables have direct influence on the sensitivity and reproducibility of the method. The pH of the extraction buffer was of the utmost importance, since it was demonstrated that a pH greater than 5 would give rise to false signals. Furthermore, modifying the composition of the extraction buffer, all formazan dye grains were solubilised, totally. A direct comparison with published methods demonstrated that only the modified method would yield 100% higher signals without increasing the background. In contrast to previous reports, it was shown that phenol red does not interfere with the measurements and no washing steps are required since all ingredients can be added subsequently. Serum proteins at concentrations up to 25% have no influence on the result. All samples can be measured in an ELISA scanner at 570 nm with little intra-assay variation.
The total glutathione content of biological samples is conveniently determined with an enzymatic recycling assay based on glutathione reductase (F. Tietze, 1969, Anal. Biochem.27, 502–522). In the original and several subsequent descriptions of this procedure, glutathione disulfide is selectively determined by assaying samples in which glutathione is masked by pretreatment with N-ethylmaleimide. Since N-ethylmaleimide is a potent inhibitor of glutathione reductase, it is necessary to remove excess reagent; the procedures used are laborious and contribute significantly to experimental error. It is reported here that 2-vinylpyridine is a much better reagent for the derivitization of glutathione. In contrast to N-ethylmaleimide, 2-vinylpyridine does not inhibit glutathione reductase significantly and therefore need not be removed from the sample solutions. 2-Vinylpyridine reacts with glutathione at slightly acidic pH values where spontaneous formation of glutathione disulfide is minimal. It is demonstrated that the total glutathione concentration in mouse plasma is substantially higher than generally reported and that glutathione disulfide constitutes less than 30% of the total glutathione present.
Reactive oxygen species produced by normal cellular metabolism have been considered to play a causative role in spontaneously occurring genomic instability and carcinogenesis. To study the genotoxic consequences of an enhanced flux of metabolically produced reactive oxygen species, cells may be exposed to hyperoxia (elevated concentrations of oxygen), a condition known to generate high levels of microscopically visible chromosomal damage. Here we assess the mutagenic potential of normobaric hyperoxia in several mammalian cells lines (CHO-K1-BH4 and AS52 Chinese hamster cells and TK6 human lymphoblastoid cells) using different target genes, including hprt, xprt and tk. Exposure of cell cultures to hyperoxia to 10-40% clonogenic cell survival, failed to induce mutations at the hprt and xprt loci. In human TK6 cells, hyperoxia failed to induce normal growing tk mutants, but efficiently induced slow growing tk mutants. The latter type of mutant is supposed to result from very large deletions or mutlilocus events. Our results suggest that elevated levels of endogenous activated oxygen species are inefficient in inducing point mutations or small deletions, but tend to generate gross rearrangements. Mammalian cells under oxidative stress thus exhibit a hyper-recombination phenotype. The carcinogenic impact of metabolic oxygen radical fluxes may thus be based on enhanced mitotic recombination rates, leading to tumor suppressor gene inactivation through 'loss of heterozygosity'.
Recently, the neurohormone melatonin was found to be a potent endogenous hydroxyl radical scavenger. Since the activation of an important transcriptional regulator, nuclear factor-kappa B (NF-kappa B) involves free radicals as second messengers, we investigated whether melatonin alters NF-kappa B expression if present during treatment of HeLa S3 cells with known activators. The results show that upon treatment of HeLa S3 cells with tumor necrosis factor-alpha or phorbol 12-myristate 13-acetate, or with ionizing radiation, there is a profound induction of NF-kappa B binding activity. If present at the time of treatment, exogenously added melatonin, at a concentration as low as 10 microM, was found to inhibit the activation of NF-kappa B by these agents. This results leads to the hypothesis that melatonin can play a role in many physiological functions through its modulation of NF-kappa B (and possibly other) transcriptional regulators.
It is known that neoplastic cachexia shows metabolic characteristics different from other common causes of malnutrition, and that it is mainly due to an abnormal secretion of TNF, whose levels are often high in patients with advanced neoplasia. Previous clinical studies have suggested that the pineal hormone melatonin (MLT), which plays an essential role in the neuroendocrine regulation of biological systems, may improve the clinical status of advanced cancer patients and inhibit TNF secretion. To investigate the relationship between MLT, TNF and cancer-related weight loss, 100 untreatable metastatic solid tumour patients entered this study to receive either supportive care alone, or supportive care plus MLT (20 mg/day orally in the evening). Patients were observed for 3 months, and were considered evaluable when they were observed for at least 2 months. There were 86 evaluable patients, the other 14 patients having died from rapid progression of disease. The per cent of weight loss greater than 10% was significantly higher in patients treated by supportive care alone than in those concomitantly treated by MLT, with no difference in food intake (P < 0.01). Mean serum levels of TNF progressively increased in the supportive care group, but to levels that were not significantly different from pretreatment values. In contrast, TNF mean concentrations significantly decreased (P < 0.05) in patients concomitantly treated by MLT. These results suggest that the pineal hormone MLT may be effective in the treatment of the neoplastic cachexia by decreasing TNF blood concentrations.