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δ-tocotrienol induce nasopharyngeal carcinoma apoptosis and Growth arrest in the CNE1 cells
Abstract
Nasopharyngeal carcinoma has a notably high incidence rate in Southern China, Southeast Asia, North Africa, Middle East, and the Arctic. δ-tocotrienol is abundant in cereal and has some health benefits....
BACKGROUND
Porcupine quills, a by‐product of porcupine pork, are rich in keratin, which is an excellent source of bioactive peptides. The objective of this study was to investigate the underlying mechanism of anti‐proliferation effect of porcupine quills keratin peptides (PQKPs) on MCF‐7 cells.
RESULTS
Results showed that PQKPs induced MCF‐7 cells apoptosis by significantly decreasing the secretion level of anti‐apoptosis protein Bcl‐2 and increasing the secretion levels of pro‐apoptosis proteins Bax, cytochrome c, caspase 9, caspase 3 and PARP. PQKPs also arrested the cell cycle at G0/G1 phase via remarkably reducing the protein levels of CDK4 and enhancing the protein levels of p53 and p21. High‐performance liquid chromatography–tandem mass spectrometry (HPLC–MS/MS) analysis identified nine peptides with molecular weights less than 1000 Da in PQKPs. Molecular docking results showed that TPGPPT and KGPAC identified from PQKPs could bind with p53 mutant and Bcl‐2 protein by conventional hydrogen bonds, carbon hydrogen bonds and van der Waals force. Furthermore, the anti‐proliferation impact of synthesized peptides (TPGPPT and KGPAC) was shown in MCF‐7 cells.
CONCLUSION
These findings indicated that PQKPs suppressed the proliferation of MCF‐7 breast cancer cells by triggering apoptosis and G0/G1 cell cycle arrest. Moreover, the outcome of this study will bring fresh insights into the production and application of animal byproducts. © 2023 Society of Chemical Industry.
Wound healing is a complex physiological process for maintaining skin integrity after a wound. Bone marrow-derived mesenchymal stem cells (BMSCs) are excellent cellular candidates for wound healing, which could be enhanced by exogenous stimulation. We aimed to explore the role of δ-Tocotrienol (δ-TT) in BMSC ability of wound healing. Firstly, transcriptome and single-cell analysis were used to explore the genes and pathways related to ferroptosis in wound tissues. In vitro, cell proliferation, migration, and angiogenesis of δ-TT-BMSCs were detected. In addition, qRT-PCR and immunofluorescence (IF) were applied for observing the promoting wound healing ability of δ-TT-BMSC conditioned medium (CM) on NIH-3T3 and PAM-212 cells. The level of ferroptosis was determined by the mitochondrial membrane potential and total/lipid reactive oxygen species (ROS) in the cells and the morphological changes of mitochondria were observed by transmission electron microscope. The BTB and CNC homology 1 (BACH1) expression and activation of the PI3K/AKT signaling pathway were detected by IF and western blot (WB). The effect of δ-TT-BMSCs on wound healing was observed in vivo. The regulatory mechanism of δ-TT-BMSCs on ferroptosis was verified by IHC and IF staining. In vitro, δ-TT-BMSCs declined the level of lipid ROS in NIH-3T3 and PAM-212 cells and enhanced mitochondrial membrane potential. In vivo, δ-TT-BMSCs promoted wound healing in mice by decreasing ferroptosis. In terms of mechanism, δ-TT-BMSCs inhibited the expression of BACH1 and activated PI3K/AKT signaling pathway. This study demonstrated the ability of δ-TT-BMSCs to promote wound healing by inhibiting BACH1-related ferroptosis. In addition, PI3K/AKT signaling pathway was activated by δ-TT-BMSCs and could be involved in wound healing. δ-TT-BMSCs might be a promising strategy for treating wounds.
Annatto seed oil (ASO) and cupuassu seed fat (CSF) were combined at the ratios: 30:70, 50:50, and 70:30 (% w/w). Their fatty acid profile, nutritional quality, FTIR (Fourier Transform Infrared) spectra, and rheological behavior were evaluated. ASO increased the content of polyunsaturated fatty acids in the blends; whereas CSF conferred higher contents of monounsaturated fatty acids. The blends exhibited low atherogenicity and thrombogenicity indices, suggesting nutritional advantages. The Newtonian fluid behavior and FTIR results suggested that mixing ASO and CSF at different proportions did not affect the functional groups. ASO showed an activation energy value which indicated that this fat viscosity was more sensitive to temperature changes. The Newtonian model proved to be suitable to describe the behavior of samples, according to statistical fit parameters R2, χ2, and RSS. The resulting blends presented improved physicochemical properties and nutritional attributes, indicating their feasibility for the development of new products.
The therapeutic potential of the tocotrienol group stems from its nutraceutical properties as a dietary supplement. It is largely considered to be safe when consumed at low doses for attenuating pathophysiology as shown by animal models, in vitro assays, and ongoing human trials. Medical researchers and the allied sciences have experimented with tocotrienols for many decades, but its therapeutic potential was limited to adjuvant or concurrent treatment regimens. Recent studies have focused on targeted drug delivery by enhancing the bioavailability through carriers, self‐sustained emulsions, nanoparticles, and ethosomes. Epigenetic modulation and computer remodeling are other means that will help increase chemosensitivity. This review will focus on the systemic intracellular anti‐cancer, antioxidant, and anti‐inflammatory mechanisms that are stimulated and/or regulated by tocotrienols while highlighting its potent therapeutic properties in a diverse group of clinical diseases.
Omega 3-docosahexaenoic acid (DHA) and vitamin E Delta-tocotrienol (Delta-T3) are extensively studied as protective nutrients against cancer development. Little is known about the biological mechanisms targeted by these bioactive molecules on lipid droplet (LD) biogenesis, an important breast cancer aggressiveness marker, and the occurrence of lipophagy in breast cancer cells. The aim of this study was to investigate the effect of DHA, Delta-T3 and DHA plus Delta-T3 co-treatment in LD biogenesis and lipophagy process in triple negative breast cancer cell line MDA-MB-231. Cells were treated with 50 μM DHA and/or 5 μM Delta-T3. Our results demonstrated that DHA can trigger an increase in LD biogenesis and co-treatment with Delta-T3 was able to reduce this LD biogenesis. In addition, we showed that a higher cytoplasmic LD content is associated with a higher breast cancer cells malignance and proliferation. Reduction of cytoplasmic LD content by silencing ADRP (adipose differentiation-related protein), a structural LD protein, also decreased cell proliferation in MDA-MB-231 cells. Treatment with DHA and Delta-T3 alone or co-treatment did not reduce cell viability. Moreover, we showed here that DHA can trigger lipophagy in MDA-MB-231 cells and DHA plus Delta-T3 co-treatment was able to enhance this lipophagy process. Our findings demonstrated that co-treatment with DHA plus Delta-T3 in MDA-MB-231 cells could reduce LD biogenesis and potentiate lipophagy in these cells, possibly having a positive impact to inhibit breast cancer malignancy. Therefore, suitable doses of DHA and Delta-T3 vitamin E isoform supplementation can be a prominent tool in therapeutic treatments against breast cancer.
Through their many and varied metabolic functions, mitochondria power life. Paradoxically, mitochondria also have a central role in apoptotic cell death. Upon induction of mitochondrial apoptosis, mitochondrial outer membrane permeabilization (MOMP) usually commits a cell to die. Apoptotic signalling downstream of MOMP involves cytochrome c release from mitochondria and subsequent caspase activation. As such, targeting MOMP in order to manipulate cell death holds tremendous therapeutic potential across different diseases, including neurodegenerative diseases, autoimmune disorders and cancer. In this Review, we discuss new insights into how mitochondria regulate apoptotic cell death. Surprisingly, recent data demonstrate that besides eliciting caspase activation, MOMP engages various pro-inflammatory signalling functions. As we highlight, together with new findings demonstrating cell survival following MOMP, this pro-inflammatory role suggests that mitochondria-derived signalling downstream of pro-apoptotic cues may also have non-lethal functions. Finally, we discuss the importance and roles of mitochondria in other forms of regulated cell death, including necroptosis, ferroptosis and pyroptosis. Collectively, these new findings offer exciting, unexplored opportunities to target mitochondrial regulation of cell death for clinical benefit.
Background:
Vitamin E δ-tocotrienol (VEDT), a vitamin E compound isolated from sources such as palm fruit and annatto beans, has been reported to have cancer chemopreventive and therapeutic effects.
Methods:
We report a novel function of VEDT in augmenting tumor necrosis factor-related apoptosis-inducing ligand- (TRAIL-) induced apoptosis in pancreatic cancer cells. The effects of VEDT were shown by its ability to trigger caspase-8-dependent apoptosis in pancreatic cancer cells.
Results:
When combined with TRAIL, VEDT significantly augmented TRAIL-induced apoptosis of pancreatic cancer cells. VEDT decreased cellular FLICE inhibitory protein (c-FLIP) levels without consistently modulating the expression of decoy death receptors 1, 2, 3 or death receptors 4 and 5. Enforced expression of c-FLIP substantially attenuated VEDT/TRAIL-induced apoptosis. Thus, c-FLIP reduction plays an important part in mediating VEDT/TRAIL-induced apoptosis. Moreover, VEDT increased c-FLIP ubiquitination and degradation but did not affect its transcription, suggesting that VEDT decreases c-FLIP levels through promoting its degradation. Of note, degradation of c-FLIP and enhanced TRAIL-induced apoptosis in pancreatic cancer cells were observed only with the anticancer bioactive vitamin E compounds δ-, γ-, and β-tocotrienol but not with the anticancer inactive vitamin E compounds α-tocotrienol and α-, β-, γ-, and δ-tocopherol.
Conclusions:
c-FLIP degradation is a key event for death receptor-induced apoptosis by anticancer bioactive vitamin E compounds in pancreatic cancer cells. Moreover, VEDT augmented TRAIL inhibition of pancreatic tumor growth and induction of apoptosis in vivo. Combination therapy with TRAIL agonists and bioactive vitamin E compounds may offer a novel strategy for pancreatic cancer intervention.
Background:
Chinese-style salted fish intake in early life is considered an established risk factor for nasopharyngeal carcinoma (NPC). However, results for adult intakes of salted fish and preserved foods are inconsistent.
Objective:
The aim of this study was to ascertain the relations of Chinese-style hard and soft salted fish and preserved food intakes with NPC risk.
Methods:
We conducted a population-based case-control study in southern China with 2554 NPC cases identified through a rapid case ascertainment system and 2648 healthy controls, frequency-matched on age, sex, and area. Subjects (aged 20-74 y) were interviewed via a food-frequency questionnaire, including information on portion size. Data were also collected on alcohol consumption and potential confounders. Food intake was grouped into 3-5 energy-adjusted intake levels during adulthood (10 y prior) and adolescence (16-18 y). For childhood (at age 10 y), intake frequency of selected food items was collected. Multivariate-adjusted ORs with 95% CIs were estimated via logistic regression.
Results:
We found no association between NPC and intake of hard Chinese-style salted fish during adulthood, and an increased risk at the highest level of intake during adolescence (OR: 1.19; 95% CI: 1.03, 1.39). In contrast, we found a decreased risk for the middle intake level of soft salted fish during adulthood (OR: 0.68; 95% CI: 0.57, 0.81) and adolescence (OR: 0.71; 95% CI: 0.59, 0.85). Preserved foods showed contrasting risk profiles, e.g., the highest adult intake level of salted egg (OR: 1.51; 95% CI: 1.22, 1.87) and fermented black beans (OR: 0.67; 95% CI: 0.56, 0.80). Associations with NPC were weaker than previously reported, e.g., for weekly childhood intake of salted fish (OR: 1.56; 95% CI: 1.24, 1.97).
Conclusions:
Hard and soft salted fish have different risk profiles. Salted fish and other preserved foods were at most weak risk factors for NPC in all periods and may play a smaller role in NPC occurrence than previously thought.
The growth and development of non-small cell lung cancer (NSCLC) primarily depends on glutamine. Both glutamine and essential amino acids (EAAs) have been reported to upregulate mTOR in NSCLC, which is a bioenergetics sensor involved in the regulation of cell growth, cell survival, and protein synthesis. Seen as novel concepts in cancer development, ASCT2 and LAT transporters allow glutamine and EAAs to enter proliferating tumors as well as send a regulatory signal to mTOR. Blocking or downregulating these glutamine transporters in order to inhibit glutamine uptake would be an excellent therapeutic target for treatment of NSCLC. This study aimed to validate the metabolic dysregulation of glutamine and its derivatives in NSCLC using cellular 1H-NMR metabolomic approach while exploring the mechanism of delta-tocotrienol (δT) on glutamine transporters, and mTOR pathway. Cellular metabolomics analysis showed significant inhibition in the uptake of glutamine, its derivatives glutamate and glutathione, and some EAAs in both cell lines with δT treatment. Inhibition of glutamine transporters (ASCT2 and LAT1) and mTOR pathway proteins (P-mTOR and p-4EBP1) was evident in Western blot analysis in a dose-dependent manner. Our findings suggest that δT inhibits glutamine transporters, thus inhibiting glutamine uptake into proliferating cells, which results in the inhibition of cell proliferation and induction of apoptosis via downregulation of the mTOR pathway.
Objectives
Prostate cancer, after the phase of androgen dependence, may progress to the castration‐resistant prostate cancer (CRPC) stage, with resistance to standard therapies. Vitamin E‐derived tocotrienols (TTs) possess a significant antitumour activity. Here, we evaluated the anti‐cancer properties of δ‐TT in CRPC cells (PC3 and DU145) and the related mechanisms of action.
Materials and methods
MTT, Trypan blue and colony formation assays were used to assess cell viability/cell death/cytotoxicity. Western blot, immunofluorescence and MTT analyses were utilized to investigate apoptosis, ER stress and autophagy. Morphological changes were investigated by light and transmission electron microscopy.
Results
We demonstrated that δ‐TT exerts a cytotoxic/proapoptotic activity in CRPC cells. We found that in PC3 cells: (a) δ‐TT triggers both the endoplasmic reticulum (ER) stress and autophagy pathways; (b) autophagy induction is related to the ER stress, and this ER stress/autophagy axis is involved in the antitumour activity of δ‐TT; in autophagy‐defective DU145 cells, only the ER stress pathway is involved in the proapoptotic effects of δ‐TT; (c) in both CRPC cell lines, δ‐TT also induces an intense vacuolation prevented by the ER stress inhibitor salubrinal and the protein synthesis inhibitor cycloheximide, together with increased levels of phosphorylated JNK and p38, supporting the induction of paraptosis by δ‐TT.
Conclusions
These data demonstrate that apoptosis, involving ER stress and autophagy (in autophagy positive PC3 cells), and paraptosis are involved in the anti‐cancer activity of δ‐TT in CRPC cells.
Delta tocotrienol has anti-neoplastic activity as demonstrated in several in-vitro and in-vivo investigations. The effect relies on inhibition of different pathways. It also has antiangiogenic activity, and an additive effect to bevacizumab may be expected.
The present study was a phase II trial of bevacizumab combined with tocotrienol in chemotherapy refractory ovarian cancer. The study also included analysis of circulating tumor specific HOXA9 methylated DNA (HOXA9 meth-ctDNA) during treatment.
The study included 23 patients. The rate of disease stabilization was 70% with very low toxicity. The median PFS was 6.9 months and the median OS 10.9 months, which is rather high compared to the current literature. A division of the patients according to level of HOXA9 meth-ctDNA already after the first cycle of chemotherapy resulted in two groups of patients with different prognoses. Patients with an increasing level of HOXA9 meth-ctDNA had a median PFS and OS of 1.4 and 4.3 months, respectively, compared to 7.8 and 12 months in the group with stable or decreasing levels.
The combination of bevacizumab and tocotrienol is potent in chemotherapy refractory ovarian cancer. The level of HOXA9 meth-ctDNA after one cycle of chemotherapy holds important prognostic information.
Background
Delta-tocotrienol (δT), an isomer of vitamin E, exhibits anticancer properties in different cancer types including non-small-cell lung cancer (NSCLC). Yet, anti-invasive effects of δT and its underlying cellular mechanism in NSCLC have not been fully explored. Matrix metalloproteinase 9 (MMP-9)-based cell migration and invasion are critical cellular mechanisms in cancer development. The current evidence indicates that MMP-9 is upregulated in most patients, and the inhibition of MMPs is involved in decreasing invasion and metastasis in NSCLC. Therefore, its suppression is a promising strategy for attenuating cell invasion and metastasis processes in NSCLC.
Purpose
The aim of this study was to evaluate the possibility of MMP-9 inhibition as the underlying mechanism behind the antimetastatic properties of δT on NSCLC cells.
Methods
The effects of δT on cell proliferation, migration, invasion, adhesion, and aggregation capabilities were investigated using different cell-based assays. An inhibitory effect of MMP-9 enzyme activity with δT was also identified using gel zymography. Using real-time PCR and Western blot analysis, a number of cellular proteins, regulatory genes, and miRNA involved in the Notch-1 and urokinase-type plasminogen activator (uPA)-mediated MMP-9 pathways were examined.
Results
The study found that δT inhibited cell proliferation, cell migration, invasion, aggregation, and adhesion in a concentration-dependent manner and reduced MMP-9 activities. Real-time PCR and Western blot analysis data revealed that δT increased miR-451 expressions and downregulated Notch-1-mediated nuclear factor-κB (NF-κB), which led to the repressed expression of MMP-9 and uPA proteins.
Conclusion
δT attenuated tumor invasion and metastasis by the repression of MMP-9/uPA via downregulation of Notch-1 and NF-κB pathways and upregulation of miR-451. The data suggest that δT may have potential therapeutic benefit against NSCLC metastasis.
One of the most common head and neck cancers is nasopharynx cancer. Knowledge about the incidence and mortality of this disease and its distribution in terms of geographical areas is necessary for prevention for further study and better planning. Therefore, this study was done with the aim of determining incidence and mortality of nasopharynx cancer and its relationship with the Human Development in Asia in 2012.
Dysregulation of the p16-cyclin D1-CDK4/6-Rb pathway occurs frequently in melanoma; however, the therapeutic efficacy of CDK4/6 inhibition remains to be critically evaluated. We demonstrate that CDK4/6 inhibition inhibits melanoma progression through induction of senescence. Palbociclib, a specific CDK4/6 inhibitor, rapidly induces cell cycle within 24h and continued exposure for 8-days or longer induces senescence. The induction of senescence correlates with inhibition of mTOR and more specifically mTORC1 signaling. Vemurafenib, a specific BRAFV600E inhibitor, has significant clinical efficacy in BRAFV600E positive melanomas but its impact is hampered by a rapid acquisition of resistance. Strikingly, we found that vemurafenib-resistant tumors remain sensitive to palbociclib suggesting that initial treatment with vemurafenib followed by palbociclib with or without mTOR inhibitors might provide an avenue to overcome recurrence of vemurafenib resistant, metastatic disease. Taken together these results support palbociclib as a promising therapeutic for treatment of melanoma.
Vitamin E intake has been implicated in reduction of bladder cancer risk. However, the mechanisms remain elusive. Here we reported that δ-tocotrienol (δ-T3), one of vitamin E isomers, possessed the most potent cytotoxic capacity against human bladder cancer cells, compared with other Vitamin E isomers. δ-T3 inhibited cancer cell proliferation and colonogenicity through induction of G1 phase arrest and apoptosis. Western blotting assay revealed that δ-T3 increased the expression levels of cell cycle inhibitors (p21, p27), proapoptotic protein (Bax) and suppressed expression levels of cell cycle protein (Cyclin D1), anti-apoptotic proteins (Bcl-2, Bcl-xL and Mcl-1), resulting in the Caspase-3 activation and cleavage of PARP. Moreover, the δ -T3 treatment inhibited ETK phosphorylation level and induced SHP-1 expression, which was correlated with downregulation of STAT3 activation. In line with this, δ-T3 reduced the STAT3 protein level in nuclear fraction, as well as its transcription activity. Knockdown of SHP-1 partially reversed δ-T3-induced cell growth arrest. Importantly, low dose of δ-T3 sensitized Gemcitabine-induced cytotoxic effects on human bladder cancer cells. Overall, our findings demonstrated, for the first time, the cytotoxic effects of δ-T3 on bladder cancer cells and suggest that δ-T3 might be a promising chemosensitization reagent for Gemcitabine in bladder cancer treatment.
Tocotrienols, especially the gamma isomer was discovered to possess cytotoxic effects associated with the induction of apoptosis in numerous cancers. Individual tocotrienol isomers are believed to induce dissimilar apoptotic mechanisms in different cancer types. This study was aimed to compare the cytotoxic potency of alpha-, gamma- and delta-tocotrienols, and to explore their resultant apoptotic mechanisms in human lung adenocarcinoma A549 and glioblastoma U87MG cells which are scarcely researched.
The cytotoxic effects of alpha-, gamma- and delta-tocotrienols in both A549 and U87MG cancer cells were first determined at the cell viability and morphological aspects. DNA damage types were then identified by comet assay and flow cytometric study was carried out to support the incidence of apoptosis. The involvements of caspase-8, Bid, Bax and mitochondrial membrane permeability (MMP) in the execution of apoptosis were further expounded.
All tocotrienols inhibited the growth of A549 and U87MG cancer cells in a concentration- and time-dependent manner. These treated cancer cells demonstrated some hallmarks of apoptotic morphologies, apoptosis was further confirmed by cell accumulation at the pre-G1 stage. All tocotrienols induced only double strand DNA breaks (DSBs) and no single strand DNA breaks (SSBs) in both treated cancer cells. Activation of caspase-8 leading to increased levels of Bid and Bax as well as cytochrome c release attributed by the disruption of mitochondrial membrane permeability in both A549 and U87MG cells were evident.
This study has shown that delta-tocotrienol, in all experimental approaches, possessed a higher efficacy (shorter induction period) and effectiveness (higher induction rate) in the execution of apoptosis in both A549 and U87MG cancer cells as compared to alpha- and gamma-tocotrienols. Tocotrienols in particular the delta isomer can be an alternative chemotherapeutic agent for treating lung and brain cancers.
Natural bioactives or phytochemicals are generally referred to as the compounds that have specific biological activity in human. Studies have shown that natural phytochemicals derived from certain plants have the capability to prevent carcinogenesis. In this special issue, we collected numerous studies which provide novel evidence to support the opinion. For instance, [6]-gingerol prevents disassembly of cell junctions and activities of MMPs in invasive human pancreas cancer cells; butein inhibits angiogenesis of human endothelial progenitor cells; the anticancer effects of sterol fraction come from red algae porphyra dentata; zeaxanthin induces apoptosis in human uveal melanoma cells; and ocotillol enhanced the antitumor activity of doxorubicin. It is therefore believed that the appropriate application of natural bioactives or phytochemicals should be a supplementary and safe way to prevent carcinogenesis and/or to enhance the efficacy of cancer therapy.
Shun-Fa Yang
Chia-Jui Weng
Gautam Sethi
Dan-Ning Hu
Introduction
Loss of the retinoblastoma protein tumor suppressor gene (RB) coding for a nuclear phosphoprotein that regulates the cell cycle is found in many human cancers and probably leads to disruption of the p16-cyclin D1-CDK4/6-RB pathway. Cyclin D1 is known to activate CDK4, which then phosphorylates the RB protein, leading to cell cycle progression. p16 inhibits CDK4, keeping RB hypophosphorylated and preventing cell cycle progression. The significance of these three markers, cyclin D1, CDK4 and p16, for breast cancer and carcinogenesis is nevertheless still controversial.
Methods
The material consisted of 102 formalin-fixed human breast cancer samples, in which cyclin D1, CDK4 and p16 expression was evaluated immunohistochemically. The amounts of cyclin D1 mRNA present were analyzed by quantitative real time PCR.
Results
High cyclin D1 expression statistically significantly correlated with lower tumor grade, estrogen and progesterone receptor positivity and lower proliferation activity in breast tumors and increased breast cancer-specific survival and overall survival. Tumors with high cyclin D1 protein had 1.8 times higher expression of cyclin D1 mRNA. CDK4 expression did not correlate with cyclin D1 expression or the survival data. p16 expression was associated with Human Epidermal Growth Factor Receptor 2 (HER2) negativity and increased breast cancer-specific survival and disease-free survival. No statistical correlations between cyclin D1, CDK4 and p16 were found.
Conclusions
Cyclin D1 was associated with a good breast cancer prognosis but functioned independently of CDK4. High cyclin D1 expression may be partially due to increased CCND1 transcription. p16 correlated with a better prognosis and may function without CDK4. In conclusion, it appears that cyclin D1, CDK4 and p16 function independently in human breast cancer.
MDA-7/IL-24 was involved in the specific cancer apoptosis through suppression of Bcl-2 expression, which is a key apoptosis regulatory protein of the mitochondrial death pathway. However, the underlying mechanisms of this regulation are unclear. We report here that tumor-selective replicating adenovirus ZD55-IL-24 leads to Bcl-2 S-denitrosylation and concomitant ubiquitination, which take part in the 26S proteasome degradation. IL-24-siRNA completely blocks Bcl-2 ubiquitination via reversion of Bcl-2 S-denitrosylation and protects it from proteasomal degradation which confirmed the significant role of MDA-7/IL-24 in regulating posttranslational modification of Bcl-2 in cancer cells. Nitric oxide (NO) is a key regulator of protein S-nitrosylation and denitrosylation. The NO donor, sodium nitroprusside (SNP), down-regulates Bcl-2 S-denitrosylation, attenuates Bcl-2 ubiquitination and subsequently counteracts MDA-7/IL-24 induced cancer cell apoptosis, whereas NO inhibitor 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxy-3-oxide (PTIO) shows the opposite effect. At the same time, these NO modulators fail to affect Bcl-2 phosphorylation, suggesting that NO regulates Bcl-2 stability in a phosphorylation-independent manner. In addition, Bcl-2 S-nitrosylation reduction induced by ZD55-IL-24 was attributed to both iNOS decrease and TrxR1 increase. iNOS-siRNA facilitates Bcl-2 S-denitrosylation and ubiquitin-degradation, whereas the TrxR1 inhibitor auranofin prevents Bcl-2 from denitrosylation and ubiquitination, thus restrains the caspase signal pathway activation and subsequent cancer cell apoptosis. Taken together, our studies reveal that MDA-7/IL-24 induces Bcl-2 S-denitrosylation via regulation of iNOS and TrxR1. Moreover, denitrosylation of Bcl-2 results in its ubiquitination and subsequent caspase protease family activation, as a consequence, apoptosis susceptibility. These findings provide a novel insight into MDA-7/IL-24 induced growth inhibition and carcinoma apoptosis.
In addition to glycolysis, the oncogenic transcription factor c-MYC (MYC) stimulates glutamine catabolism to fuel growth and proliferation of cancer cells through up-regulating glutaminase (GLS). Glutamine is converted to glutamate by GLS, entering the tricarboxylic acid cycle as an important energy source. Less well-recognized, glutamate can also be converted to proline through Δ(1)-pyrroline-5-carboxylate (P5C) and vice versa. This study suggests that some MYC-induced cellular effects are due to MYC regulation of proline metabolism. Proline oxidase, also known as proline dehydrogenase (POX/PRODH), the first enzyme in proline catabolism, is a mitochondrial tumor suppressor that inhibits proliferation and induces apoptosis. MiR-23b* mediates POX/PRODH down-regulation in human kidney tumors. MiR-23b* is processed from the same transcript as miR-23b; the latter inhibits the translation of GLS. Using MYC-inducible human Burkitt lymphoma model P493 and PC3 human prostate cancer cells, we showed that MYC suppressed POX/PRODH expression primarily through up-regulating miR-23b*. The growth inhibition in the absence of MYC was partially reversed by POX/PRODH knockdown, indicating the importance of suppression of POX/PRODH in MYC-mediated cellular effects. Interestingly, MYC not only inhibited POX/PRODH, but also markedly increased the enzymes of proline biosynthesis from glutamine, including P5C synthase and P5C reductase 1. MYC-induced proline biosynthesis from glutamine was directly confirmed using (13)C,(15)N-glutamine as a tracer. The metabolic link between glutamine and proline afforded by MYC emphasizes the complexity of tumor metabolism. Further studies of the relationship between glutamine and proline metabolism should provide a deeper understanding of tumor metabolism while enabling the development of novel therapeutic strategies.
Infectious spleen and kidney necrosis virus (ISKNV) is the type species of the Megalocytivirus genus of the Iridoviridae family. It causes a serious and potentially pandemic disease in wild and cultured fishes. ISKNV infection induces evident apoptosis in mandarin fish (Siniperca chuatsi) and zebrafish (Danio renio). However, the mechanism is still unknown. After a genome-wide bioinformatics analysis of ISKNV-encoded proteins, the ISKNV open reading frame 111L (ORF111L) shows a high similarity to the tumour necrosis factor receptor-associated factor (TRAF) encoded by fish, mice and mammals, which is essential for apoptotic signal transduction. Moreover, ORF111L was verified to directly interact with the zebrafish TNF receptor type 1 associated death domain protein (TRADD). A recombinant plasmid containing the DNA sequence of ORF111L was constructed and microinjected into zebrafish embryos at the 1-2 cell stage to investigate its biological function in vivo. ORF111L overexpression in the embryos resulted in increased apoptosis. ORF111L-induced apoptosis was clearly associated with significant caspase 8 upregulation and activation. The knockdown of zebrafish caspase 8 expression effectively blocked the apoptosis induced by ORF111L overexpression. Significantly, ORF111L overexpression resulted in much stronger effect on caspase 8 and caspase 3 upregulation compared to zebrafish TRAF2. This is the first report of a viral protein similar to TRAF that interacts with TRADD and induces caspase 8-mediated apoptosis, which may provide novel insights into the pathogenesis of ISKNV infection.
Unlabelled:
Tocotrienols of palm oil have been shown to possess potent neuroprotective, antioxidative, anticancer, and cholesterol-lowering activities. In this study, the authors examined the antiproliferative effects of alpha-, gamma- and delta-tocotrienols (alphaT3, gammaT3, and deltaT3), and alpha-tocopherol (alphaT) in human cervical carcinoma (HeLa) cells. Their mechanism(s) of action on cell cycle signaling pathway were also investigated.
Results:
3.19 +/- 0.05 microM) and gammaT3 (IC(50): 2.85 +/- 0.07 microM) was more potent than deltaT3 (IC(50): >100 microM) and alphaT (IC(50): 69.46 +/- 3.01 microM). Both alphaT3 and gammaT3 also demonstrated a dose-dependent and time-dependent induction of cell death.They caused cell cycle arrest at G2/M phase and triggered apoptosis as displayed by the externalization of annexin V-targeted phosphatidylserine and accumulation of sub-G1 peak. At a concentration of 3 microM, alphaT3 downregulated the expression of cyclin D3, p16, and CDK6, while having no effect on cyclin D1, p15, p21, p27, and CDK4 expression. However, gammaT3 showed no effect on these proteins. The induction of HeLa cell apoptosis by alphaT3 and gammaT3 appeared to be associated with the expression of IL-6, but not the other cytokines (IFN-gamma, IL-2, and IL-10).Taken together, the results suggest that alphaT3 and gammaT3 are more effective than deltaT3 and alphaT in inhibiting HeLa cell proliferation, and their mode of action could be through the upregulation of IL-6, and the downregulation of cyclin D3, p16, and CDK6 expression in the cell cycle signaling pathway.
gamma-Tocotrienol, a member of the vitamin E family of compounds, induces apoptosis in a variety of cancer cell types. However, previous studies have clearly demonstrated that gamma-tocotrienol-induced apoptosis in neoplastic mouse +SA mammary epithelial cells is not mediated through mitochondrial stress or death receptor apoptotic signaling. Therefore, studies were conducted to determine the role of endoplasmic reticulum (ER) stress in mediating gamma-tocotrienol-induced apoptosis in +SA mammary tumor cells. Treatment with 15-40 microM gamma-tocotrienol induced +SA cell death in a dose-responsive manner, and these effects were associated with a corresponding increase in poly (ADP-ribose) polymerase (PARP)-cleavage and activation of protein kinase-like endoplasmic reticulum kinase/eukaryotic translational initiation factor/activating transcription factor 4 (PERK/eIF2alpha/ATF-4) pathway, a marker of ER stress response. These treatments also caused a large increase in C/EBP homologous protein (CHOP) levels, a key component of ER stress mediated apoptosis that increases expression of tribbles 3 (TRB3). Knockdown of CHOP by specific siRNAs attenuated gamma-tocotrienol-induced PARP-cleavage, CHOP and TRB3 expression. gamma-Tocotrienol treatment also reduced full-length caspase-12 levels, an indication of caspase-12 cleavage and activation. Intracellular levels of 3-hydroxy-3-methylglutaryl-coenzyme A (HMGCoA) reductase, an ER-transmembrane enzyme catalyzing the synthesis of mevalonate, decreased following gamma-tocotrienol treatment, but combined treatment with mevalonate did not reverse gamma-tocotrienol-induced apoptosis, suggesting that a decrease in HMGCoA reductase activity is not required for gamma-tocotrienol induced apoptosis. These results demonstrate that ER stress apoptotic signaling is associated with gamma-tocotrienol-induced apoptosis in +SA mammary tumor cells.
Beta-blocking agents reduce the risk of hospitalization and death in patients with mild-to-moderate heart failure, but little is known about their effects in severe heart failure.
We evaluated 2289 patients who had symptoms of heart failure at rest or on minimal exertion, who were clinically euvolemic, and who had an ejection fraction of less than 25 percent. In a double-blind fashion, we randomly assigned 1133 patients to placebo and 1156 patients to treatment with carvedilol for a mean period of 10.4 months, during which standard therapy for heart failure was continued. Patients who required intensive care, had marked fluid retention, or were receiving intravenous vasodilators or positive inotropic drugs were excluded.
There were 190 deaths in the placebo group and 130 deaths in the carvedilol group. This difference reflected a 35 percent decrease in the risk of death with carvedilol (95 percent confidence interval, 19 to 48 percent; P=0.00013, unadjusted; P=0.0014, adjusted for interim analyses). A total of 507 patients died or were hospitalized in the placebo group, as compared with 425 in the carvedilol group. This difference reflected a 24 percent decrease in the combined risk of death or hospitalization with carvedilol (95 percent confidence interval, 13 to 33 percent; P<0.001). The favorable effects on both end points were seen consistently in all the subgroups we examined, including patients with a history of recent or recurrent cardiac decompensation. Fewer patients in the carvedilol group than in the placebo group withdrew because of adverse effects or for other reasons (P=0.02).
The previously reported benefits of carvedilol with regard to morbidity and mortality in patients with mild-to-moderate heart failure were also apparent in the patients with severe heart failure who were evaluated in this trial.
It has been estimated that 30-40 percent of all cancers can be prevented by lifestyle and dietary measures alone. Obesity, nutrient sparse foods such as concentrated sugars and refined flour products that contribute to impaired glucose metabolism (which leads to diabetes), low fiber intake, consumption of red meat, and imbalance of omega 3 and omega 6 fats all contribute to excess cancer risk. Intake of flax seed, especially its lignan fraction, and abundant portions of fruits and vegetables will lower cancer risk. Allium and cruciferous vegetables are especially beneficial, with broccoli sprouts being the densest source of sulforophane. Protective elements in a cancer prevention diet include selenium, folic acid, vitamin B-12, vitamin D, chlorophyll, and antioxidants such as the carotenoids (alpha-carotene, beta-carotene, lycopene, lutein, cryptoxanthin). Ascorbic acid has limited benefits orally, but could be very beneficial intravenously. Supplementary use of oral digestive enzymes and probiotics also has merit as anticancer dietary measures. When a diet is compiled according to the guidelines here it is likely that there would be at least a 60-70 percent decrease in breast, colorectal, and prostate cancers, and even a 40-50 percent decrease in lung cancer, along with similar reductions in cancers at other sites. Such a diet would be conducive to preventing cancer and would favor recovery from cancer as well.
Apoptosis is the best-characterized form of programmed cell death (PCD) and is of fundamental importance in tissue homeostasis. In mammalian systems, there are two major pathways that are involved in the initiation of apoptosis: the "extrinsic" death receptor pathway and the "intrinsic" mitochondrial pathway. Although these pathways act independently to initiate the death machinery in some cellular systems, in many cell types, including numerous tumor cells, there is delicate coordination and cross talk between the extrinsic and intrinsic pathways, which leads to the activation of the executioner caspase cascade. Additionally, there appears to be a fine balance between the caspase-mediated arm of death receptor signaling that engages mitochondria and the caspase-independent arm that promotes vacuole proliferation in many cells. Here, we review our current knowledge about the layers of complexity that are posed by the interactions between death receptor-induced pathways and how they influence mitochondria to regulate cellular life and death decisions.
The process of programmed cell death, or apoptosis, is generally characterized by distinct morphological characteristics and energy-dependent biochemical mechanisms. Apoptosis is considered a vital component of various processes including normal cell turnover, proper development and functioning of the immune system, hormone-dependent atrophy, embryonic development and chemical-induced cell death. Inappropriate apoptosis (either too little or too much) is a factor in many human conditions including neurodegenerative diseases, ischemic damage, autoimmune disorders and many types of cancer. The ability to modulate the life or death of a cell is recognized for its immense therapeutic potential. Therefore, research continues to focus on the elucidation and analysis of the cell cycle machinery and signaling pathways that control cell cycle arrest and apoptosis. To that end, the field of apoptosis research has been moving forward at an alarmingly rapid rate. Although many of the key apoptotic proteins have been identified, the molecular mechanisms of action or inaction of these proteins remain to be elucidated. The goal of this review is to provide a general overview of current knowledge on the process of apoptosis including morphology, biochemistry, the role of apoptosis in health and disease, detection methods, as well as a discussion of potential alternative forms of apoptosis.
Nasopharyngeal carcinoma is characterised by distinct geographical distribution and is particularly prevalent in east and southeast Asia. Epidemiological trends in the past decade have shown that its incidence has declined gradually but progressively, and mortality has been reduced substantially. These findings probably reflect lifestyle and environmental changes, enhanced understanding of the pathogenesis and risk factors, population screening, advancements in imaging techniques, and individualised comprehensive chemoradiotherapy strategies. In particular, plasma Epstein-Barr virus (EBV) DNA has been used for population screening, prognostication, predicting treatment response for therapeutic adaptation, and disease surveillance. Moreover, the widespread application of intensity-modulated radiotherapy and optimisation of chemotherapy strategies (induction, concurrent, adjuvant) have contributed to improved survival with reduced toxicities. Among the existing developments in novel therapeutics, immune checkpoint therapies have achieved breakthroughs for treating recurrent or metastatic disease and represent a promising future direction in nasopharyngeal carcinoma.
The therapeutic options for castration resistance prostate cancer (CRPC) are still limited. Natural bioactive compounds were shown to possess pro-death properties in different tumors. We previously reported that δ-tocotrienol (δ-TT) induces apoptosis, paraptosis and autophagy in CRPC cells. Here, we investigated whether δ-TT might exert its activity by impairing mitochondrial functions. We demonstrated that, in PC3 and DU145 cells, δ-TT impairs mitochondrial respiration and structural dynamics. In both cell lines, δ-TT triggers mitochondrial Ca²⁺ and ROS overload. In PC3 cells, both Ca²⁺ and ROS mediate the δ-TT-related anticancer activities (decrease of cell viability, apoptosis, paraptosis, autophagy and mitophagy). As expected, in autophagy-defective DU145 cells, Ca²⁺ overload was involved in δ-TT-induced pro-death effects but not in autophagy and mitophagy. In this cell line, we also demonstrated that ROS overload is not involved in the anticancer activities of δ-TT, supporting a low susceptibility of these cells to ROS-related oxidative stress. Taken together, these data demonstrate that, in CRPC cells, δ-TT triggers cell death by inducing mitochondrial functional and structural impairments, providing novel mechanistic insights in its antitumor activity.
Objectives:
This study aimed to explore the prognostic value of extensive invasion of primary tumor volume for local control in patients with T3-4 NPC receiving intensity-modulated radiotherapy (IMRT).
Materials and methods:
Between January 2009 and December 2015, initial volume of GTV-P, the confined and extensive invasion part of GTV-P (GTV-C and GTV-E) were obtained from 159 prospectively enrolled non-metastatic T3-4 NPC patients. GTV-E included the tumor with infiltration of bony structures at skull base, cervical vertebra, paranasal sinuses or with intracranial extension. GTV-C was calculated by the subtraction of GTV-E from GTV-P. The effects of tumor volume levels on local control rate (LC) were evaluated by Kaplan-Meier method and multivariate analysis.
Results:
GTV-P (P = 0.015) and GTV-E (P = 0.001) were significantly correlated with local failure, while GTV-C (P = 0.494) was not. Then optimal cut-off values of GTV-P (43 mL) and GTV-E (22 mL) were determined by receiver operating characteristic curve analysis. Patients with small (<22 mL) GTV-E achieved better 5-year LC rate than those with large (≥22 mL) GTV-E (96.3% vs.76.1%, P < 0.001), but no significant difference was found between patients with small (<43 mL) and large (≥43 mL) GTV-P (95.9% vs. 85.5%, P = 0.094). Multivariate analysis also demonstrated large (≥22 mL) GTV-E to be an independent unfavorable prognostic factor for LC (hazard ratio [HR], 3.805; 95% CI, 1.100-13.166; P = 0.035).
Conclusion:
GTV-E is an independent prognostic factor for LC in T3-4 NPC and may further assist in the optimization of treatment strategies.
Due to TRAIL's explicit cancer cell-selectivity, the current study aimed to explore novel agents that sensitized cancer cell for TRAIL-induced apoptosis while sparing normal cell. In this study, we found that TRAIL could induce PARP-1 cleavage and apoptosis in colon cancer HCT116 cell, but HT-29 cell was not sensitive to TRAIL. However, non-cytotoxic doses of ipatasertib in conjunction with TRAIL could induce apoptosis in HT-29 cell. Mechanism studies showed that intracellular ROS level was significant increased during ipatasertib treatment. Excessive cellular levels of ROS further induced DNA damage and subsequently activated apoptotic signaling pathways in TRAIL-resistant HT-29 cells. Combined treatment with sub-toxic doses of ipatasertib and TRAIL leads to caspase activation and PARP-1 cleavage in HT-29 cells. Pretreated with NAC, an antioxidant, could inhibit ROS production and PARP-1 cleavage as well as prevent cell apoptotic death induced by combination therapy with TRAIL and ipatasertib. In addition, NAC can block the up-regulation of p53/PUMA induced by combined treatment with ipatasertib and TRAIL. Transfection with p53 or Puma siRNA for 48 h can reverse ipatasertib-mediated TRAIL sensitization. In conclusion, p53 and PUMA may play a pivotal role in sensitizing colon cancer cell to TRAIL-induced apoptosis by sub-toxic doses of ipatasertib treatment.
This study evaluated the preclinical activity of δ-tocotrienol (DT3), a bioactive form of vitamin E, in the inhibition of colorectal cancer growth and development in vitro and in vivo. DT3 is the most bioactive isomer of vitamin E in inhibiting growth of colorectal cancer cells. However, it had little effect on the proliferation of normal colon mucosal cells NCM460. In HCT-116 and SW-620 colorectal cancer cells, DT3 (50 µM) significantly inhibited malignant transformation (P < .02, P < .001), cell migration (P < .02, P < .05) and invasion (P < .05, P < .01) compared to vehicle. DT3 inhibited markers for epithelial (E-cadherin) to mesenchymal (vimentin) transition, metastasis (matrix metalloproteinase 9), angiogenesis vascular endothelial growth factor (VEGF), inflammation (NF-kB), and Wnt signaling (β-catenin) compared to vehicle in colorectal cancer cells. DT3 induced apoptosis selectively in colorectal cancer cells (SW-620 cells, HCT-116 cells, and HT-29) without affecting the normal colon cells. In the Azoxymethane-induced colorectal carcinogenesis model in rats, DT3 (200 mg/kg orally twice a day) for 20 weeks significantly inhibited colorectal polyps by 70% and colorectal cancer by almost 99% compared to the vehicle treatment group (P < .02, P < .001), and the cancer inhibition effect was more potent than sulindac (50%). Taken together, these data demonstrate that DT3 is a potential chemopreventive agent in colorectal cancer, warranting further investigation into its clinical use in the prevention and treatment of colorectal cancer.
The loss of vital cells within healthy tissues contributes to the development, progression and treatment outcomes of many human disorders, including neurological and infectious diseases as well as environmental and medical toxicities. Conversely, the abnormal survival and accumulation of damaged or superfluous cells drive prominent human pathologies such as cancers and autoimmune diseases. Apoptosis is an evolutionarily conserved cell death pathway that is responsible for the programmed culling of cells during normal eukaryotic development and maintenance of organismal homeostasis. This pathway is controlled by the BCL-2 family of proteins, which contains both pro-apoptotic and pro-survival members that balance the decision between cellular life and death. Recent insights into the dynamic interactions between BCL-2 family proteins and how they control apoptotic cell death in healthy and diseased cells have uncovered novel opportunities for therapeutic intervention. Importantly, the development of both positive and negative small-molecule modulators of apoptosis is now enabling researchers to translate the discoveries that have been made in the laboratory into clinical practice to positively impact human health.
Colon cancer, one of the leading causes of cancer-associated deaths, is a target of choice for nutrition-based prevention approaches because of the direct and early contact of the active compounds with the cancerous tissues. We previously reported alkylresorcinols (ARs) as the major active components in wheat bran against human colon cancer. Here, we further investigated the anticancer mechanisms of action of ARs. Our mechanistic studies indicated that AR C15 and AR C17 exerted their anticancer activities in colon cancer cells by inducing apoptosis through PUMA up-regulation and mitochondrial pathway activation, inducing cell cycle arrest through p21 up-regulation, and inhibiting proteasome activity and Mdm2 expression. This cascade of distinct mechanisms was linked to the consequent activation and accumulation of p53. The results of treatment with p53 inhibitor further confirmed that p53 pathway might play a very important role on the AR-induced apoptosis in colon cancer cells. Altogether these results show that AR C15 and AR C17 can specifically activate the mitochondrial pathway of apoptosis and cause cell cycle arrest, and that inhibition of p53 greatly reduced the activation of this pathway.
Background
Nasopharyngeal carcinoma (NPC) is the most common type of head and neck cancers which is notable for its distinctive pattern of geographical distribution. HOTAIR has been reported to regulate nasopharyngeal carcinoma tumorigenesis and progression. However, the detailed mechanism underlying HOTAIR-promoted nasopharyngeal carcinoma remains not fully understood.
Methods
We used RT-qPCR approach to examine genes expression and mRNA level. MTT assay and soft agar assay were used to detect cell growth rate in culture and under suspended condition, respectively. Besides, we employed wound healing assay and transwell invasion assay to determine migration and invasion ability of nasopharyngeal carcinoma cells. We predicted direct downstream targets of miR-101 by bioinformatic analysis, which was confirmed by dual luciferase reporter assay.
Results
HOTAIR was upregulated in NPC tissues and cells. miR-101 inhibitor greatly enhanced HOTAIR knockdown-regulated cell proliferation, migration and invasion of CNE1 and CNE2 cells. miR-101 was shown to directly bind 3′-UTR of COX-2 and downregulate COX-2 expression. Finally, COX-2 overexpression was demonstrated to rescue the tumor phenotypes of nasopharyngeal carcinoma cells attenuated by HOTAIR knockdown or miR-101 mimic.
Conclusions
Here, we highlight the importance of HOTAIR/miR-101/COX-2 axis in progression of nasopharyngeal carcinoma cells. Our findings provide a novel mechanism for explaining HOTAIR-induced nasopharyngeal carcinoma and help developing the therapeutical strategies by targeting HOTAIR.
The human body generates 10-100 billion cells every day, and the same number of cells die to maintain homeostasis in our body. Cells infected by bacteria or viruses also die. The cell death that occurs under physiological conditions mainly proceeds by apoptosis, which is a noninflammatory, or silent, process, while pathogen infection induces necroptosis or pyroptosis, which activates the immune system and causes inflammation. Dead cells generated by apoptosis are quickly engulfed by macrophages for degradation. Caspases are a large family of cysteine proteases that act in cascades. A cascade that leads to caspase 3 activation mediates apoptosis and is responsible for killing cells, recruiting macrophages, and presenting an "eat me" signal(s). When apoptotic cells are not efficiently engulfed by macrophages, they undergo secondary necrosis and release intracellular materials that represent a damage-associated molecular pattern, which may lead to a systemic lupus-like autoimmune disease. Expected final online publication date for the Annual Review of Immunology Volume 36 is April 26, 2018. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.
The growth-suppressive effect of d-?-tocotrienol and geranylgeraniol is at least partially attributed to their impact on 3-hydroxy-3-methylglutaryl coenzyme A (HMG CoA) reductase, the rate-limiting enzyme in the mevalonate pathway that provides essential intermediates for the posttranslational modification of growth-related proteins including RAS. We hypothesize that these agents synergistically impact cell growth based on their complementary mechanisms of action with HMG CoA reductase. d-?-tocotrienol (0-40??mol/L; half maximal inhibitory concentration [IC50] = 15??mol/L) and geranylgeraniol (0-100??mol/L; IC50 = 60??mol/L) each induced concentration-dependent suppression of the growth of human DU145 prostate carcinoma cells. Blends of the two agents synergistically suppressed the growth of DU145 cells, with combination index values ranging 0.67-0.75. While 7.5??mol/L d-?-tocotrienol and 30??mol/L geranylgeraniol individually had no impact on cell cycle distribution in DU145 cells, a blend of the agents induced cell cycle arrest at the G1 phase. The synergistic downregulation of the expression of HMG CoA reductase by 7.5??mol/L d-?-tocotrienol and 30??mol/L geranylgeraniol was accompanied by a reduction in membrane K-RAS protein. Our finding supports the cancer chemopreventive action of plant-based diets and their isoprenoid constituents. Properly formulated isoprenoids and derivatives may provide novel approaches in prostate cancer prevention and therapy.
Organismal development and function requires multiple and accurate signal transduction pathways to ensure that proper balance between cell proliferation, differentiation, inactivation, and death is achieved. Cell death via apoptotic caspase signal transduction is extensively characterized and integral to this balance. Importantly, the view of apoptotic signal transduction has expanded over the previous decades. Sub-apoptotic caspase signaling has surfaced as mechanism that can promote the adoption of a range of cellular fates. An emerging mechanism of sub-apoptotic caspase signaling is the activation of the Caspase-Activated DNase (CAD) through controlled cleavage of the Inhibitor of CAD, ICAD. CAD-induced DNA breaks incite a DNA damage response, frequently invoking p53 signaling, that transduces a change in cell fate. Cell differentiation and senescence are fates demonstrated to arise from CAD induced DNA breaks. Further, an apparent consequence of CAD activity is also emerging, as a potential source of oncogenic mutations. This review will discuss the mechanisms underlying CAD-induced DNA breaks and highlight how CAD activity promotes diverse cell fates. This article is protected by copyright. All rights reserved.
p21 (WAF1/CIP1; CDKN1a) is a universal cell-cycle inhibitor directly controlled by p53 and p53-independent pathways. Knowledge of the regulation and function of p21 in normal and cancer cells has opened up several areas of investigation and has led to novel therapeutic strategies. The discovery in 1993 and subsequent work on p21 has illuminated basic cellular growth control, stem cell phenotypes, the physiology of differentiation, as well as how cells respond to stress. There remain open questions in the signaling networks, the ultimate role of p21 in the p53-deficiency phenotype in the context of other p53 target defects, and therapeutic strategies continue to be a work in progress. Cancer Res; 76(18); 5189–91. ©2016 AACR.
See related article by El-Deiry et al., Cancer Res 1994;54:1169–74.
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The cyclin-dependent kinase inhibitor p21(WAF1/CIP1) (p21) is a cell-cycle checkpoint effector and inducer of senescence, regulated by p53. Yet, evidence suggests that p21 could also be oncogenic, through a mechanism that has so far remained obscure. We report that a subset of atypical cancerous cells strongly expressing p21 showed proliferation features. This occurred predominantly in p53-mutant human cancers, suggesting p53-independent upregulation of p21 selectively in more aggressive tumour cells. Multifaceted phenotypic and genomic analyses of p21-inducible, p53-null, cancerous and near-normal cellular models showed that after an initial senescence-like phase, a subpopulation of p21-expressing proliferating cells emerged, featuring increased genomic instability, aggressiveness and chemoresistance. Mechanistically, sustained p21 accumulation inhibited mainly the CRL4-CDT2 ubiquitin ligase, leading to deregulated origin licensing and replication stress. Collectively, our data reveal the tumour-promoting ability of p21 through deregulation of DNA replication licensing machinery-an unorthodox role to be considered in cancer treatment, since p21 responds to various stimuli including some chemotherapy drugs.
An appropriate control over cell cycle progression depends on many factors. Cyclin-dependent kinase (CDK) inhibitor p21 (also known as p21(WAF1/Cip1)) is one of these factors that promote cell cycle arrest in response to a variety of stimuli. The inhibitory effect of P21 on cell cycle progression correlates with its nuclear localization. P21 can be induced by both p53-dependent and p53-independent mechanisms. Some other important functions attributed to p21 include transcriptional regulation, modulation or inhibition of apoptosis. These functions are largely dependent on direct p21/protein interactions and also on p21 subcellular localizations. In addition, p21 can play a role in DNA repair by interacting with proliferating cell nuclear antigen (PCNA). In this review, we will focus on the multiple functions of p21 in cell cycle regulation, apoptosis and gene transcription after DNA damage and briefly discuss the pathways and factors that have critical roles in p21 expression and activity.
This definition includes two main areas: (1) descriptive epidemiology, covering the distribution of diseases in place and time; and (2) analytical epidemiology, aimed at characterizing possible causal factors.
Anticancer activity and mitochondrial mechanism of the vitamin E form δ-tocotrienol (δ-T3) was investigated in HER-2/neu-overexpressing human SKBR3 and murine TUBO breast cancer cells. δ-T3 was confirmed to possess high cytotoxic and apoptotic activity in SKBR3 cells as compared with all natural forms of vitamin E and several synthetic forms that included novel derivatives with the same backbone of δ-T3 such as δ-tocotrienyl-succinyl amide (δ-T3AS) and the redox-active analogue δ-tocotrienyl amine (δ-T3NH2). As observed in the case of alpha-TOS, a prototypical anticancer drug derived from α-tocopherol, succinylation of δ-T3 enhanced citotoxicity and apoptotic activity of the vitamer. δ-T3 induced apoptosis of SKBR3 cells was associated with mitochondrial destabilization, energy failure, and unbalanced activity of stress/survival MAPKs, namely p38 and ERK1/2 pathways. An increased generation of ROS followed to such a series of early events. Enhanced activity of δ-T3 in this human carcinoma cell line was characterized by the sustained uptake and oxidative transformation to the quinone derivative δ-T3Q, thereby suggesting redox effects in SKBR3 mitochondria by this vitamer. Viability and uptake data show a different pattern of responses in TUBO cells with higher response to synthetic derivatives of δ-T3 than in SKBR3 cells. In conclusion, synthetic derivatives of δ-T3 with enhanced apoptotic activity in breast carcinoma cells are investigated for the first time in this study also describing mechanistic aspects of mitochondrial effects of δ-T3. Further investigation in preclinical models of HER2/neu-high breast adenocarcinoma is underway to identify other and more effective forms of VE in this type of cancer. © 2013 BioFactors, 2013.
Tocotrienols are naturally occurring forms of vitamin E based on their structural similarity. This study focused on investigating anticancer effects of tocotrienols and the mechanisms of apoptosis induction by tocotrienols in vivo and in vitro. Dietary delivery of γ-tocotrienol (γ-T3) suppressed tumor growth in a syngeneic implantation mouse mammary cancer model by inhibiting cell proliferation and inducing apoptosis. In cell culture studies, γ-T3 inhibited colony formation of a mouse mammary cancer cell line and human breast cancer cell lines. The anti-proliferative effects of tocotrienols were highly correlated with an increase in apoptosis based on Annexin V assessment. Treatment of human MDA-MB-231 and MCF-7 cells with γ-T3 induced cleavages of PARP as well as caspase-8, -9, and -3. Additional analyses showed that γ-T3 activated c-Jun NH(2)-terminal kinase (JNK) and p38 MAPK, and upregulated death receptor 5 (DR5) and C/EBP homologous protein (CHOP), an endoplasmic reticulum (ER) stress marker. Silencing either JNK or p38 MAPK reduced the increase in DR5 and CHOP and partially blocked γ-T3-induced apoptosis. Both DR5 and CHOP upregulation were required for γ-T3-induced apoptosis, and DR5 was transcriptionally regulated by CHOP after γ-T3 treatment. Moreover, γ-T3 increased the level of other ER-stress markers. Taken together, these results suggest that upregulation of DR5 by γ-T3 treatment is dependent on JNK and p38 MAPK activation which is mediated by ER-stress.
gamma-Tocotrienol is a major component of the tocotrienol-rich fraction of palm oil, but there is limited evidence that it has antitumor activity. In particular, the effects of gamma-tocotrienol on human colon carcinoma cells have not been reported. To investigate the chemopreventive effects of gamma-tocotrienol on colon cancer, we examined its capacity to inhibit proliferation and induce apoptosis in HT-29 cells and explored the mechanism underlying these effects.
We cultured HT-29 cells in the presence of gamma-tocotrienol. The effect of gamma-tocotrienol on cell proliferation was investigated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, mitotic index, and colony formation. The cell-cycle distribution was investigated by flow cytometry. We measured apoptosis by nuclear staining, transmission electron microscopy, and DNA fragmentation. Apoptosis-related proteins and the nuclear factor-kappaB p65 protein were determined by western blotting and immunofluorescence.
gamma-Tocotrienol inhibited cell growth and arrested HT-29 cells in G(0)/G(1) phase. The 50% inhibitory concentration was 31.7 micromol/L (48 h). gamma-Tocotrienol-induced apoptosis in HT-29 cells was accompanied by downregulation of Bcl-2, upregulation of Bax, and activation of caspase-3. Furthermore, we found that gamma-tocotrienol reduced the expression level of total nuclear factor-kappaB p65 protein and inhibited its nuclear translocation.
The results indicated that gamma-tocotrienol inhibits cell proliferation and induces apoptosis in HT-29 cells in a time- and dose-dependent manner, and that this process is accompanied by cell-cycle arrest at G(0)/G(1), an increased Bax/Bcl-2 ratio, and activation of caspase-3. Our data also indicated that nuclear factor-kappaB p65 protein may be involved in these effects.
Tables showing representative values for the vitamin E content of human foods have been developed from all the available reliable information. These tables cover animal products, plant products, fats and oils, baked products, infant foods, and mixed dishes. The effects on vitamin E content are discussed for heating and storage of dairy products, grains, vegetables, and plant oils; for the refining of plant oils; and for the processing and baking of grain products. Causes of variation in vitamin E levels are presented and the distribution of the different forms of vitamin E in foods is shown. The biologic activities of these forms are used to calculate approximate vitamin activity values of representative foods.
This optimization study for tocopherols and tocotrienols involved both normal- and reverse-phase liquid chromatography using various columns and mobile phases. Normal-phase systems showed elution of the homologs in order of increasing polarity with separation based on methyl substituents on the chromanol moiety. Reverse-phase systems showed class separation based on the saturation of the phytyl side chain; the more saturated tocopherols were retained on the column longer. When the Zorbax ODS was used with an isocratic ternary acetonitrile:methanol:methylene chloride (60:35:5) mixture, the optimized resolution was greater than 2.0 and separation was achieved in less than 13 min, but there was no separation of beta- and gamma-tocopherols. The normal-phase silica and amino columns provided separation of all available isomers with resolution greater than 1.1 and separation times of less than 5.5 and less than 10 min, respectively. Optimized isocratic binary solvent mixtures of hexane:2-propanol were used for silica (99:1) and amino (98:2) columns. Derivative spectra showed differences depending on substituents in the chromanol moiety but not the phytyl side chain. Second- and fourth-derivative spectra gave the best differentiation of the vitamin E isomers.
Epidemiological studies show that the consumption of Chinese salted fish is a causative factor for nasopharyngeal carcinoma (NPC) in southern China. In the present study, N-nitrosamines and their precursors were analyzed in 145 samples of cooked, salted fish collected from various areas in China. The results show that N-dimethylnitrosamine (NDMA), N-diethylnitrosamine (NDEA), N-nitrosopyrrolidine (NPYR) and N-nitrosopiperidine (NPIP) were present in the salted fish. Total volatile N-nitrosamines (TVN) in the salted fish were 0.028 to 4.54 mg/kg. The samples from areas with higher NPC risk showed a higher average level of TVN than those from areas of lower NPC risk. Positive correlations were found between the levels of NDMA, NDEA and TVN and mortality from NPC. Although neither the nitrates nor the nitrites in the salted fish were present at significantly high levels, in vitro data regarding nitrosation of salted fish showed that the N-nitrosamine content had increased substantially. The results support the conclusion that the high NPC risk in southern Chinese may be attributed to consumption of salted fish containing high levels of N-nitrosamines.
Two novel tocotrienols were isolated from stabilized and heated rice bran, apart from the known alpha-, beta-, gamma-, and delta-tocopherols and tocotrienols. These new tocotrienols were separated by HPLC, using a normal phase silica column. Their structures were determined by ultraviolet, infrared, nuclear magnetic resonance, circular dichroism, and high-resolution mass spectroscopies and established as desmethyl tocotrienol [3, 4-dihydro-2-methyl-2-(4,8,12-trimethyltrideca-3'(E),7'(E), 11'-trienyl)-2H-1-benzopyran-6-ol] and didesmethy tocotrienol [3, 4-dihydro-2-(4,8,12-trimethyltrideca-3'(E),7'(E), 11'-trienyl)-2H-1-benzopyran-6-ol]. These tocotrienols significantly lowered serum total and LDL cholesterol levels and inhibited HMG-CoA reductase activity in chickens. They had much greater in vitro antioxidant activities and greater suppression of B16 melanoma cell proliferation than alpha-tocopherol and known tocotrienols. Results indicated that the number and position of methyl substituents in tocotrienols affect their hypocholesterolemic, antioxidant, and antitumor properties.
Studies were conducted to determine the comparative effects of tocopherols and tocotrienols on preneoplastic (CL-S1), neoplastic (-SA), and highly malignant (+SA) mouse mammary epithelial cell growth and viability in vitro. Over a 5-day culture period, treatment with 0-120 microM alpha- and gamma-tocopherol had no effect on cell proliferation, whereas growth was inhibited 50% (IC50) as compared with controls by treatment with the following: 13, 7, and 6 microM tocotrienol-rich-fraction of palm oil (TRF); 55, 47, and 23 microM delta-tocopherol; 12, 7, and 5 microM alpha-tocotrienol; 8, 5, and 4 microM gamma-tocotrienol; or 7, 4, and 3 microM delta-tocotrienol in CL-S1, -SA and +SA cells, respectively. Acute 24-hr exposure to 0-250 microM alpha- or gamma-tocopherol (CL-S1, -SA, and +SA) or 0-250 microM delta-tocopherol (CL-S1) had no effect on cell viability, whereas cell viability was reduced 50% (LD50) as compared with controls by treatment with 166 or 125 microM delta-tocopherol in -SA and +SA cells, respectively. Additional LD50 doses were determined as the following: 50, 43, and 38 microM TRF; 27, 28, and 23 microM alpha-tocotrienol; 19, 17, and 14 microM gamma-tocotrienol; or 16, 15, or 12 microM delta-tocotrienol in CL-S1, -SA, and +SA cells, respectively. Treatment-induced cell death resulted from activation of apoptosis, as indicated by DNA fragmentation. Results also showed that CL-S1, -SA, and +SA cells preferentially accumulate tocotrienols as compared with tocopherols, and this may partially explain why tocotrienols display greater biopotency than tocopherols. These data also showed that highly malignant +SA cells were the most sensitive, whereas the preneoplastic CL-S1 cells were the least sensitive to the antiproliferative and apoptotic effects of tocotrienols, and suggest that tocotrienols may have potential health benefits in preventing and/or reducing the risk of breast cancer in women.
Beneath the complexity and idiopathy of every cancer lies a limited number of 'mission critical' events that have propelled the tumour cell and its progeny into uncontrolled expansion and invasion. One of these is deregulated cell proliferation, which, together with the obligate compensatory suppression of apoptosis needed to support it, provides a minimal 'platform' necessary to support further neoplastic progression. Adroit targeting of these critical events should have potent and specific therapeutic consequences.
Tocotrienols, which are Vitamin E isoforms, are known to inhibit the growth of human breast cancer cells due partly to apoptosis. However, the characterization of tocotrienol-induced apoptosis is incomplete, particularly what happens during the initiation phase that precedes execution of the cells. The objective of this study was to clarify the apoptotic effects of tocotrienols, with especial emphasis in determining if the mitochondria-mediated death pathway is activated when human breast cancer cells are incubated with a specific tocotrienol isomer. During incubation with gamma-tocotrienol, MDA-MB-231 human breast cancer cells showed membrane blebbing, and apoptotic bodies were present. Upon 4',6-diamidino-2-phenylindole staining of the cells, chromatin condensation and fragmentation were observed. Additionally, the annexin V-binding assay detected the translocation of membrane phospholipid during earlier analysis of the cells. Taken together, these results further establish that gamma-tocotrienol can induce apoptosis in human breast cancer cells. To help elucidate how gamma-tocotrienol induced the apoptosis, some important parameters related to the mitochondria-mediated death pathway were examined next. In gamma-tocotrienol-treated cells, the mitochondria were disrupted. Collapse of the mitochondrial membrane potential was detected, and cytochrome c was released later from mitochondria. However, expression of Bax and Bcl-2 (mRNA and protein) did not change. Furthermore, poly-(ADP-ribose)-polymerase cleavage was not detected, suggesting that caspases were not involved in the gamma-tocotrienol-induced apoptosis. These results imply that cytochrome c is not the critical protein released from mitochondria that triggers gamma-tocotrienol-induced apoptosis in MDA-MB-231 cells.