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Anticancer effects of anandamide on head and neck squamous cell carcinoma cells via the production of receptor-independent reactive oxygen species

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Abstract

Background: The endocannabinoids, anandamide (AEA) and 2-arachidonoyl glycerol (2-AG), are considered promising potential anticancer agents. In this study, we examined the anticancer effects of AEA and 2-AG in head and neck squamous cell carcinoma (HNSCC) cell lines. Methods and results: Our results showed that AEA effectively inhibited proliferation of HNSCC cells whereas 2-AG did not. The anticancer effect of AEA seemed to be mediated by a receptor-independent mechanism. Inhibitors of AEA intracellular transportation and transfection of HNSCC cells with fatty acid amide hydrolase, a key enzyme in AEA metabolism, reversed AEA-dependent inhibition of cell proliferation. We found that cyclooxygenase-2 (COX-2) did not mediate the anticancer effects of AEA; instead we observed an increase in reactive oxygen species (ROS) production after AEA treatment. Moreover, antioxidants partially reversed AEA-dependent inhibition of cell proliferation. Conclusion: These findings suggest that AEA might have anticancer effects on HNSCC cells by mediating an increase in ROS levels through a receptor-independent mechanism.

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... The ECS is biologically widespread and plays a role in multiple physiopathological processes. The aerodigestive tract is a system in which endocannabinoids and their receptors play an important role, including in olfaction, appetite stimulation, asthma/ airway immune response, and cancer (Hutch et al. 2015;Fraguas-Sanchez et al. 2018;Bozkurt 2019)Furthermore, alteration of endocannabinoid expression in head and neck epithelium, and bronchi alveolar epithelium occurs in multiple diseases (Zoerner et al. 2011;Shang et al. 2016) and in some cancers (Whyte et al. 2010;Park et al. 2015;Gegotek et al. 2016). ...
... Furthermore, 2-AG decreased cell proliferation to a greater degree that AEA in LSCC cells and the difference was significant (p = 0.026*). Park et al. (2015) observed the antiproliferative effect of AEA on HNSCC cell lines [SNU-1041: hypopharyngeal squamous cell carcinoma; SNU-1066: LSCC] using the Cell County Kit-8 at 72 h, whereas 2-AG did not produce the same antiproliferative effect, in contrast to the present 2-AG findings. This difference might be due to differences in the dose range; in the present study 30 lM of 2-AG was administered to the cell proliferation assay according to its Ki value for CB2, whereas, Park et al. (2015) used 20 lM of 2-AG. ...
... Park et al. (2015) observed the antiproliferative effect of AEA on HNSCC cell lines [SNU-1041: hypopharyngeal squamous cell carcinoma; SNU-1066: LSCC] using the Cell County Kit-8 at 72 h, whereas 2-AG did not produce the same antiproliferative effect, in contrast to the present 2-AG findings. This difference might be due to differences in the dose range; in the present study 30 lM of 2-AG was administered to the cell proliferation assay according to its Ki value for CB2, whereas, Park et al. (2015) used 20 lM of 2-AG. Another difference is that cell proliferation was measured on d 4 in the present study, versus d 3 in Park et al.'s study. ...
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The level of the major endocannabinoids anandamide (AEA) and 2-arachidonoylglycerol (2-AG) are altered in several types of carcinomas, and are known to regulate tumor growth. Thusly, this study hypothesized that the HEp-2 human laryngeal squamous cell carcinoma (LSCC) cell line releases AEA and 2-AG, and aimed to determine if their exogenous supplementation has an anti-proliferative effect in vitro. In this in vitro observational study a commercial human LSCC cell line (HEp-2) was used to test for endogenous AEA and 2-AG release via liquid chromatography-tandem mass spectrometry (LC–MS/MS). The anti-proliferative effect of AEA and 2-AG supplementation was evaluated via WST-1 proliferation assay. It was observed that the HEp-2 LSCC cell line released AEA and 2-AG; the median quantity of AEA released was 15.69 ng mL–1 (range: 14.55–15.95 ng mL–1) and the median quantity of 2-AG released was 2.72 ng –1 (range: 2.67–2.74 ng mL–1). Additionally, both AEA and 2-AG exhibited an anti-proliferative effect. The anti-proliferative effect of 2-AG was stronger than that of AEA. These findings suggest that AEA might function via a CB1 receptor-independent pathway and that 2-AG might function via a CB2-dependent pathway. The present findings show that the HEp-2 LSCC cell line releases the major endocannabinoids AEA and 2-AG, and that their supplementation inhibits tumor cell proliferation in vitro. Thus, cannabinoid ligands might represent novel drug candidates for laryngeal cancers, although functional in vivo studies are required in order to validate their potency.
... DHEA and NALA effectively induced the cell death in the HNSCC cell lines (Fig. 1b). CB1 is expressed only in SNU-1066 and no expression of CB2 is observed in all the cells tested, while VR1 expression is observed in all cells (in our own study) [23]. We also found that the anti-cancer effect of DHEA and NALA was not reversed by antagonists of the endocannabinoid receptors CB1 and VR1 (AM251 and cay10448) (Fig. 1c). ...
... In our own study, we observed that AEA increased intracellular oxidative stress, including lipid peroxidation [23]. Since DHEA and NALA are very similar to AEA, we assumed that DHEA and NALA might affect cell viability by increasing intracellular ROS production. ...
... Since psychotropic side effects by cannabis are reported to be mediated by classic cannabinoid receptors [1], there might be some concern about the idea of adopting endocannabinoids as a cancer treatment. However, it has been also reported that the cell-killing effect of several endocannabinoids is mediated by cannabinoid receptor- independent mechanisms [6,7,23]. In addition to classic receptors like CB1 and CB2, GPR55 and GPR35 were recently reported as putative receptors of endocannabinoids [13,27]. ...
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Background: Endocannabinoids have recently drawn attention as promising anti-cancer agents. We previously observed that anandamide (AEA), one of the representative endocannabinoids, effectively inhibited the proliferation of head and neck squamous cell carcinoma (HNSCC) cell lines in a receptor-independent manner. In this study, using HNSCC cell lines, we examined the anti-cancer effects and the mechanisms of action of docosahexaenoyl ethanolamide (DHEA) and N-arachidonoyl-L-alanine (NALA), which are polyunsaturated fatty acid (PUFA)-based ethanolamides like AEA. Methods and results: DHEA and NALA were found to effectively inhibit HNSCC cell proliferation. These anti-proliferative effects seemed to be mediated in a cannabinoid receptor-independent manner, since the antagonist of cannabinoid receptor-1 (CB1) and vanilloid receptor-1 (VR1), two endocannabinoid receptors, did not reverse the ability of DHEA and NALA to induce cell death. Instead, we observed an increase in reactive oxygen species (ROS) production and a decrease of phosphorylated Akt as a result of DHEA and NALA treatment. Antioxidants efficiently reversed the inhibition of cell proliferation and the decrease of phosphorylated Akt induced by DHEA and NALA; inhibition of 5-lipoxygenase (5-LO), which is expected to be involved in DHEA- and NALA-degradation pathway, also partially blocked the ability of DHEA and NALA to inhibit cell proliferation and phosphorylated Akt. Interestingly, ROS production as a result of DHEA and NALA treatment was decreased by inhibition of 5-LO. Conclusions: From these findings, we suggest that ROS production induced by the 5-LO pathway mediates the anti-cancer effects of DHEA and NALA on HNSCC cells. Finally, our findings suggest the possibility of a new cancer-specific therapeutic strategy, which utilizes 5-LO activity rather than inhibiting it.
... It was previously reported that polyunsaturated fatty acids can increase intracellular oxidative stress, including lipid peroxidation [53,54]. Indeed, AEA has been found to enhance the production of 8-isoprotane in head and neck squamous cell carcinoma cells and microglial cells treated with lipopolysaccharide (LPS) [55,56]. Taken together, these observations indicate that methanandamide is capable of acting as a prooxidant when administered in high concentrations in the isolated bovine retina. ...
... In a series of experiments, exposure of retinal tissues to low concentrations of 2-AG (1-3 µM) for 30 min significantly blocked the H 2 O 2 -dependent increase in 8-isoprostane levels, whereas higher concentrations of the endocannabinoid enhanced 8-isoprostane production in the neural retina. The observed enhancement of H 2 O 2 -induced 8-isoprostane production is similar to responses elicited by methanadamine indicating that 2-AG may also be capable of acting as a prooxidant [55,56]. In summary, the observed pharmacological actions of methanandamide and 2-AG in the bovine retina support the dualistic nature of cannabinoids in their ability to regulate oxidative stress. ...
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Both hydrogen sulfide and endocannabinoids can protect the neural retina from toxic insults under in vitro and in vivo conditions. Purpose: The aim of the present study was two-fold: (a) to examine the neuroprotective action of cannabinoids [methanandamide and 2-arachidonyl glycerol (2-AG)] against hydrogen peroxide (H2O2)-induced oxidative damage in the isolated bovine retina and (b) to evaluate the role of endogenously biosynthesized hydrogen sulfide (H2S) in the inhibitory actions of cannabinoids on the oxidative stress in the bovine retina. Methods: Isolated neural retinas from cows were exposed to oxidative damage using H2O2 (100 µM) for 10 min. When used, tissues were pretreated with methanandamide (1 nM–100 nM) and 2-AG (1–10 µM) for 30 min before a 10 min treatment with H2O2 (100 µM). In some experiments, retinas were pretreated with inhibitors of the biosynthesis of H2S [cystathionine β-synthase/cystathionine γ-lyase (CBS/CSE), aminooxyacetic acid, AOAA 30 µM, or 3-mercaptopyruvate sulfurtransferase (3MST), α-keto-butyric acid, KBA 1 mM] and the CB1-receptor antagonist, AM251 (100 nM) for 30 min before treatment with methanandamide (1 nM–100 µM). Enzyme immunoassay measurement of 8-epi PGF2α (8-isoprostane) levels was performed to assess lipid peroxidation in retinal tissues. Results: In the presence of H2O2 (100 µM), methanandamide (1 nM–100 µM) and 2-AG (1–10 µM) significantly (p < 0.001) blocked the H2O2-induced elevation in 8-isoprostane levels in the isolated bovine retina. In the presence of the CB1 antagonist AM251 (100 nM), the effect of methanandamide (1 nM) on the H2O2-induced 8-isoprostane production was significantly (p < 0.001) attenuated. While AOAA (30 µM) had no significant (p > 0.05) effect on the inhibition of H2O2-induced oxidative stress elicited by methanandamide, KBA (1 mM) reversed the neuroprotective action of methanandamide. Conclusions: The cannabinoids, methanandamide and 2-AG can prevent H2O2-induced oxidative stress in the isolated bovine retina. The neuroprotective actions of cannabinoids are partially dependent upon the activation of the CB1 receptors and endogenous production of H2S via the 3-MST/CAT pathway.
... Identified interactions with control probe 8 are used to filter out nonspecific PUFAderived probe interactions in the data analysis of the proteomics. Following earlier in vitro studies investigating the anti-inflammatory effect of DHEA and AEA in this and similar models, 9,12,14,15,17,18,21,27 probe concentrations of 10 μM were used, which are of the same order of magnitude or even below those used in comparable studies with similar lipid probes. 6,28,29 Lastly, applying 10 μM probe counters the attrition that is associated with different steps in the methodology (i.e., uptake of probes by macrophages, nonquantitative yield of photolabeling, 22 and loss during enrichment) to obtain sufficient levels of labeled protein above the detection limit of the liquid chromatography tandem mass spectrometry (LC−MS/MS). ...
... Previous proteomic screening with AA, the PUFA precursor of AEA, also showed an interaction of AA with ROS regulators in RAW264.7 macrophages, which was ascribed to the induction of lipid electrophile-driven coupling upon stimulation of the macrophages with the LPS mimetic Kdo 2 -lipid A. 29 Although our methodology used diazirine crosslinking, lipid electrophile coupling to ROS scavengers could not be ruled out as a possible interaction mechanism between AEA, DHEA, and Prdxs. Interestingly, both DHEA and AEA were reported to induce the ROS production in HNSCC cells, 12,27 and in 0.1 μg mL −1 LPS-stimulated mouse macrophages, 10 nM DHEA was found to reduce ROS production. 10 In addition to Prdxs, we found ribosomal proteins, acetyl-CoA acetyltransferase (Acat1, mitochondrial), and the signaling regulator Rhoc in the top 10 AEA probe 5 interactors (Table 1). ...
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We studied the mechanistic and biological origins of anti-inflammatory poly-unsaturated fatty acid-derived N-acylethanolamines using synthetic bifunctional chemical probes of docosahexaenoyl ethanolamide (DHEA) and arachidonoyl ethanolamide (AEA) in RAW264.7 macrophages stimulated with 1.0 μg mL-1 lipopolysaccharide. Using a photoreactive diazirine, probes were covalently attached to their target proteins, which were further studied by introducing a fluorescent probe or biotin-based affinity purification. Fluorescence confocal microscopy showed DHEA and AEA probes localized in cytosol, specifically in structures that point toward the endoplasmic reticulum and in membrane vesicles. Affinity purification followed by proteomic analysis revealed peroxiredoxin-1 (Prdx1) as the most significant binding interactor of both DHEA and AEA probes. In addition, Prdx4, endosomal related proteins, small GTPase signaling proteins, and prostaglandin synthase 2 (Ptgs2, also known as cyclooxygenase 2 or COX-2) were identified. Lastly, confocal fluorescence microscopy revealed the colocalization of Ptgs2 and Rac1 with DHEA and AEA probes. These data identified new molecular targets suggesting that DHEA and AEA may be involved in reactive oxidation species regulation, cell migration, cytoskeletal remodeling, and endosomal trafficking and support endocytosis as an uptake mechanism.
... Figure 3 provides an overview of the mechanisms of the proapoptotic effect of AEA on tumorigenic keratinocytes. Furthermore, AEA, but not 2-AG, was found to exert an anticancer effect on head and neck squamous cell carcinoma cell lines (SNU-1041, SNU-1066 and PCI-1) via a receptor-independent mechanism mediated by an increase in ROS [98]. It is noteworthy that in the latter study, no involvement of COX-2 in AEA-induced apoptosis was detected. ...
... It is noteworthy that in the latter study, no involvement of COX-2 in AEA-induced apoptosis was detected. In line with this finding, the authors were also unable to detect any cytotoxic effect of the Furthermore, AEA, but not 2-AG, was found to exert an anticancer effect on head and neck squamous cell carcinoma cell lines (SNU-1041, SNU-1066 and PCI-1) via a receptorindependent mechanism mediated by an increase in ROS [98]. It is noteworthy that in the latter study, no involvement of COX-2 in AEA-induced apoptosis was detected. ...
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Simple Summary Recent research has suggested that the endocannabinoid system offers several pharmacotherapeutic targets for drug administration as new options for the treatment and prophylaxis of skin cancer. This review focused on the anticarcinogenic mechanisms of cannabinoids at the different levels of skin cancer progression, such as inhibition of tumour growth, proliferation, invasion and angiogenesis, as well as inducing apoptosis and autophagy. Abstract Drugs targeting the endocannabinoid system are of interest as potential systemic chemotherapeutic treatments and for palliative care in cancer. In this context, cannabinoid compounds have been successfully tested as a systemic therapeutic option in preclinical models over the past decades. Recent findings have suggested an essential function of the endocannabinoid system in the homeostasis of various skin functions and indicated that cannabinoids could also be considered for the treatment and prophylaxis of tumour diseases of the skin. Cannabinoids have been shown to exert their anticarcinogenic effects at different levels of skin cancer progression, such as inhibition of tumour growth, proliferation, invasion and angiogenesis, as well as inducing apoptosis and autophagy. This review provides an insight into the current literature on cannabinoid compounds as potential pharmaceuticals for the treatment of melanoma and squamous cell carcinoma.
... Early diagnosed sporadic CSCC is usually treated with surgery or radiochemotherapy, but the metastatic form is the cause of high mortality and unfavorable prognosis [30,31]. CB1 and CB2 are highly expressed in CSCC and basal cell carcinoma (BCC) [19,24,31] and several studies demonstrated the anti-proliferative and anti-migratory effects of (endo)cannabinoids in these tumors [24,[32][33][34][35]. The epithelialto-mesenchymal transition is a crucial event in tumor progression and metastasis [36][37][38][39]. ...
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The endocannabinoid system regulates physiological processes, and the modulation of endogenous endocannabinoid (eCB) levels is an attractive tool to contrast the development of pathological skin conditions including cancers. Inhibiting FAAH (fatty acid amide hydrolase), the degradation enzyme of the endocannabinoid anandamide (AEA) leads to the increase in AEA levels, thus enhancing its biological effects. Here, we evaluated the anticancer property of the FAAH inhibitor URB597, investigating its potential to counteract epithelial-to-mesenchymal transition (EMT), a process crucially involved in tumor progression. The effects of the compound were determined in primary human keratinocytes, ex vivo skin explants, and the squamous carcinoma cell line A431. Our results demonstrate that URB597 is able to hinder the EMT process by downregulating mesenchymal markers and reducing migratory potential. These effects are associated with the dampening of the AKT/STAT3 signal pathways and reduced release of pro-inflammatory cytokines and tumorigenic lipid species. The ability of URB597 to contrast the EMT process provides insight into effective approaches that may also include the use of FAAH inhibitors for the treatment of skin cancers.
... The levels of plasma and/or tissue 2-AG are elevated in colorectal cancer [55], craniopharyngioma [117], diffuse large B-cell lymphoma [118], glioma [78], and hepatocellular carcinoma [100], whereas the levels of AEA are reduced in hepatocellular carcinoma [100] and glioma [78]. In consistence with downregulation of AEA in glioma and hepatocellular carcinoma [78,100], the functional studies support a tumor suppressive role of AEA in head and neck and laryngeal squamous cell carcinomas [119,120]. Although 2-AG was elevated in various human malignancies [55,78,100,117,118], the functional evidence does not support an oncogenic role of 2-AG in tumor progression. ...
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Citation: Cherkasova, V.; Wang, B.; Gerasymchuk, M.; Fiselier, A.; Kovalchuk, O.; Kovalchuk,
... The levels of plasma and/or tissue 2-AG are elevated in colorectal cancer [55], craniopharyngioma [117], diffuse large B-cell lymphoma [118], glioma [78], and hepatocellular carcinoma [100], whereas the levels of AEA are reduced in hepatocellular carcinoma [100] and glioma [78]. In consistence with downregulation of AEA in glioma and hepatocellular carcinoma [78,100], the functional studies support a tumor suppressive role of AEA in head and neck and laryngeal squamous cell carcinomas [119,120]. Although 2-AG was elevated in various human malignancies [55,78,100,117,118], the functional evidence does not support an oncogenic role of 2-AG in tumor progression. ...
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The endocannabinoid system (ECS) is an ancient homeostasis mechanism operating from embryonic stages to adulthood. It controls the growth and development of many cells and cell lineages. Dysregulation of the components of the ECS may result in uncontrolled proliferation, adhesion, invasion, inhibition of apoptosis and increased vascularization, leading to the development of various malignancies. Cancer is the disease of uncontrolled cell division. In this review, we will discuss whether the changes to the ECS are a cause or a consequence of malignization and whether different tissues react differently to changes in the ECS. We will discuss the potential use of cannabinoids for treatment of cancer, focusing on primary outcome/care—tumor shrinkage and eradication, as well as secondary outcome/palliative care—improvement of life quality, including pain, appetite, sleep, and many more factors. Finally, we will complete this review with the chapter on sex- and gender-specific differences in ECS and response to cannabinoids, and equality of the access to treatments with cannabinoids.
... Our results indicated a significantly increased level of ROS induced by CM treatment in both compartments (Figure 2, panels A and B). This outcome was in accordance with a report made by Park et al. who showed that the endocannabinoid anandamide (AEA) had an anti-cancer effect on head and neck squamous cell carcinoma (HNSCC) cell lines, which was mediated by increased ROS levels [36]. In addition, this increase in mitochondria was associated with a significant decrease in their ΔΨm suggesting an impaired functional capacity of the organelle (Figure 2, panel C). ...
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Cannabinoids, the active components of cannabis exert palliative effects in cancer patients by preventing nausea, vomiting and pain as well as by stimulating appetite. Recent studies indicated that cannabinoids could be helpful in treating certain rare forms of cancer and other inflammatory diseases. The objective of this study was to investigate the cytotoxic effect of a cannabinoid mixture (CM) in oral cells. Thus, normal and cancer gingival cells were treated with different concentrations of CM to evaluate their proliferation by MTT assay, cytotoxicity by using LDH assay, colony formation with crystal violet and migration by the scratch method. In addition, apoptosis, autophagy, oxidative stress, antioxidant level, DNA damage and the mitochondrial membrane potential (ΔΨm) generated by proton pumps were measured by flow cytometry. Furthermore, deactivation of the key signaling pathways involved in cancer progression such as NF-κB, ERK1/2, p38, STAT1, STAT3, STAT5 was also evaluated by this technique. These outcomes indicate that CM, at a concentration higher than 0.1 µg/mL, provokes high cytotoxicity in Ca9-22 oral cancer cells but not in GMSM-K gingival normal cells. Apoptosis, autophagy, antioxidant levels and mitochondrial stress as well as DNA damage in oral cells were increased following exposure to low concentration (1 µg/mL). In addition, major signaling pathways that are involved such as MAPKase, STATs and NF-κB pathways were inhibited by CM as well as cell migration. Our results suggest that cannabinoids could potentially have a beneficial effect on oral cancer therapy.
... Thus, we decided to check if anandamide had the same influence on the glucose uptake performed by melanoma cells and what effect it had on the results from the intensive metabolism production of reactive oxygen species, as the disturbance in the glucose uptake is typically followed by changes in the natural by-products of the metabolism in the form of various reactive species (oxygen, ROS; or nitrogen, RNS) [25]. With both performed analyses we received a significant increase in the resulting values of glucose uptake and ROS production (approximately 150% of control) for only the metastatic cell lines treated with 1 µM AEA. Park et al. [54] suggested that a significant rise of ROS levels (depending on the cell line 200-350% of control) caused by the 18 h treatment with AEA, in general, plays a partial role in the anticancer effect of this endocannabinoid on the head and neck squamous cell carcinoma (HNSCC) lines. Moreover, a 2 h incubation with 10 µM AEA induced a significant increase (30-times) in the intracellular ROS accumulation in cholangiocytes isolated from BDL mice [55]. ...
Article
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An effective therapy for advanced melanoma, a skin cancer with the highest mortality, has not yet been developed. The endocannabinoid system is considered to be an attractive target for cancer treatment. The use of endocannabinoids, such as anandamide (AEA), is considered to be much greater than as a palliative agent. Thus, we checked its influence on various signaling pathways in melanoma cells. Our investigation was performed on four commercial cell lines derived from different progression stages (radial WM35 and vertical WM115 growth phases, lymph node WM266-4 metastasis, solid tumor A375-P metastasis). Cell viability, glucose uptake, quantification of reactive oxygen species production, expression of selected genes encoding glycosyltransferases, quantification of glycoproteins production and changes in the glycosylation profile and migration, as well as in cell elastic properties were analyzed. The cell glycosylation profile was investigated using the biophysical profiling method—the quartz crystal microbalance with dissipation monitoring (QCM-D). Anandamide treatment of only metastatic cells resulted in: an increase in the cell metabolism, a decrease in GFAT-1 and DPM1 expression, followed by a decrease in L1-CAM glycoprotein production, which further influenced the reduction in the cell glycosylation profile and migration. Considering our results, AEA usage is highly recommended in the combined therapy of advanced melanoma.
... Moreover, AEA was demonstrated to induce a cyclooxygenase-2 (COX-2)-dependent cell death in apoptosisresistant colon cancer cells at a concentration of 25 µM devoid of CB 1 and CB 2 receptor activation (Patsos et al., 2010). In contrast to these findings, another investigation could not confirm a contribution of COX-2 to the AEA-induced apoptosis of HNSCC cell lines (Park et al., 2015). In this study, a high concentration of AEA (20 µM) was shown to induce apoptosis via enhanced oxidative stress bypassing cannabinoid-activated receptors. ...
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Currently, the involvement of the endocannabinoid system in cancer development and possible options for a cancer-regressive effect of cannabinoids are controversially discussed. In recent decades, a number of preclinical studies have shown that cannabinoids have an anticarcinogenic potential. Therefore, especially against the background of several legal simplifications with regard to the clinical application of cannabinoid-based drugs, an extended basic knowledge about the complex network of the individual components of the endocannabinoid system is required. The canonical endocannabinoid system consists of the endocannabinoids N-arachidonoylethanolamine (anandamide) and 2-arachidonoylglycerol as well as the Gi/o protein-coupled transmembrane cannabinoid receptors CB1 and CB2. As a result of extensive studies on the broader effect of these factors, other fatty acid derivatives, transmembrane and intracellular receptors, enzymes and lipid transporters have been identified that contribute to the effect of endocannabinoids when defined in the broad sense as “extended endocannabinoid system.” Among these additional components, the endocannabinoid-degrading enzymes fatty acid amide hydrolase and monoacylglycerol lipase, lipid transport proteins of the fatty acid-binding protein family, additional cannabinoid-activated G protein-coupled receptors such as GPR55, members of the transient receptor family, and peroxisome proliferator-activated receptors were identified as targets for possible strategies to combat cancer progression. Other endocannabinoid-related fatty acids such as 2-arachidonoyl glyceryl ether, O-arachidonoylethanolamine, N-arachidonoyldopamine and oleic acid amide showed an effect via cannabinoid receptors, while other compounds such as endocannabinoid-like substances exert a permissive action on endocannabinoid effects and act via alternative intracellular target structures. This review gives an overview of the modulation of the extended endocannabinoid system using the example of anticancer cannabinoid effects, which have been described in detail in preclinical studies.
... Also, the silencing of PGC-1α decreased the mitochondrial function, as evidenced by the reduction in the mitochondrial complex I and IV activities and the oxygen consumption ratio. The production of ROS during chemotherapy, including 5FU-based therapies, is a critical mechanism by which anti-cancer drugs exert their effects [44]. We confirmed that the downregulation of PGC-1α induced mitochondrial ROS and inhibited the activity of antioxidant enzymes after treatment with 5FU in 5FU-resistant CRC cells. ...
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Anti-cancer drug resistance is a serious issue for patients with colorectal cancer (CRC). Although recent studies have shown the mechanism by which CRC cells become drug resistant, novel strategies for overcoming this drug resistance have not yet been developed. To address this problem, we characterized 5-fluorouracil (5FU)-resistant CRC cells after treatment with 5FU, and focused on the expression of peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) in these cells. In 5FU-resistant CRC cells, the 5FU did not considerably decrease the mitochondrial biogenesis or mitochondrial complex I and IV activities, and only partially decreased the antioxidant enzymatic activity, oxygen consumption ratio, and cell survival. The expression of PGC-1α was remarkably increased in the 5FU-resistant CRC cells compared with the 5FU-sensitive CRC cells. The 5FU-resistant CRC cells displayed enhanced mitochondrial biogenesis, oxidative phosphorylation, and antioxidant enzyme activities against 5FU-induced reactive oxygen species, because of the increased expression of PGC-1α. PGC-1α inhibited 5FU-induced endoplasmic reticulum (ER) stress in the 5FU-resistant CRC cells, resulting in the suppression of apoptosis. These findings reveal that PGC-1α plays an important role in drug resistance in 5FU-resistant CRC cells. Moreover, PGC-1α could serve as a novel target in patients with 5FU-resistant CRC.
... In the past, the increase of reactive oxygen species (ROS) has been seen as a disadvantageous circumstance associated with carcinogenesis and cancer progression. In contrast, there are agents known to kill cancer cells in vitro by promoting cellular ROS accumulation (3)(4)(5). Additionally, since some cancer cells are more sensitive to ROS than normal cells, (6) selective generation of ROS may be a promising strategy for killing cancer cells without significantly harming benign tissue (7)(8)(9). ...
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Despite partial advances in therapy for patients suffering from head and neck squamous cell carcinomas (HNSCC), prognosis still remains poor with minimal improvement in survival for over the last several decades. Some agents found are known to cause cancer cell death in vitro by promoting cellular reactive oxygen species (ROS) accumulation. This is particularly of interest as some cancer cells are more sensitive to ROS than normal cells. It could be shown that the novel polyphenol conjugate (E)-3-(3',5'-Dimethoxyphenyl)-1-(2'-methoxyphenyl) prop-2-en-1-one (DPP-23) offers antitumor effects by the selective generation of ROS without an indication of toxicity in normal tissues in vitro and in vivo. In order to further evaluate the role of DPP-23 as a potential agent in head and neck oncology, the present study investigated its cytotoxic effects on well-established HNSCC cell lines such as HLaC 78 and FaDu, as well as primary human bone marrow stem cells (hBMSCs) and human peripheral blood lymphocytes in vitro. As DPP-23 is not commercially available, it was synthesized via a ‘cold’ procedure of the Claisen-Schmidt condensation. Following cell treatment with DPP-23 for 24 h, viability and apoptosis were measured via a MTT assay and the Annexin V-propidium iodide test. The results suggest a dose-dependent cytotoxicity in the tested HNSCC tumor cell lines, as well as in hBMSC and lymphocytes. In contrast to previous findings, these preliminary results indicate that the cytotoxic effects of DPP-23 in benign cells may be notably greater than previously suspected. This may indicate a limitation for in the feasibility, or at least of the systemic application, of DPP-23 for patients with HNSCC.
... However, the oxidative properties of AEA and the role of oxidative stress in AEA-induced tumor cell death have not been fully characterized. It has been reported that AEA-induced cell death was prevented by the antioxidants, NAC, GSH, and ebselen in head and neck squamous cell carcinoma cells [57]. In addition, we showed previously that inhibiting the generation of oxidative stress with NAC blocked AEA-mediated apoptosis in tumorigenic keratinocytes. ...
Article
Endocannabinoids are neuromodulatory lipids that regulate central and peripheral physiological functions. Endocannabinoids have emerged as effective antitumor drugs due to their ability to induce apoptosis in various cancer studies. The G-protein coupled cannabinoid receptors (CB1 and CB2) and the TRPV1 ion channel were reported to mediate the antiproliferative activity of endocannabinoids. However, receptor-independent effects also account for their activity. Our previous studies showed that the antiproliferative activity of anandamide (AEA) was regulated by cyclooxygenase-2 (COX-2) via induction of endoplasmic reticulum (ER) stress. We also determined that AEA induced oxidative stress. However, the role of oxidative stress, the cannabinoid receptors, and TRPV1 in AEA-induced ER stress-apoptosis was unclear. Therefore, the current study examines the role of oxidative stress in ER stress-apoptosis and investigates whether this effect is modulated by CB1, CB2, or TRPV1. In non-melanoma skin cancer (NMSC) cells, AEA reduced the total intracellular level of glutathione and induced oxidative stress. To evaluate the importance of oxidative stress in AEA-induced cell death, the antioxidants, N-acetylcysteine (NAC) and Trolox, were utilized. Each antioxidant ameliorated the antiproliferative effect of AEA. Furthermore, Trolox inhibited AEA-induced CHOP10 expression and caspase 3 activity, indicating that oxidative stress was required for AEA-induced ER stress-apoptosis. On the other hand, selective blockade of CB1, CB2, and TRPV1 did not inhibit AEA-induced oxidative stress or ER stress-apoptosis. These findings suggest that AEA-induced ER stress-apoptosis in NMSC cells is mediated by oxidative stress through a receptor-independent mechanism. Hence, receptor-independent AEA signaling pathways may be targeted to eliminate NMSC. © 2015 Wiley Periodicals, Inc.
... Elevated levels of caspase-3, along with apoptotic proteins caspase-9, cytochrome c, apoptotic protease-activating factor-1 (Apaf-1), apoptosis-inducing factor (AIF), and Bcl2-associated X protein (Bax) were also demonstrated in cisplatin-resistant oral cancer cells exposed to curcumin nanoparticles, along with increased production of ROS (Chang et al, 2013). The endocannabinoid anandamide inhibited cell proliferation by increasing ROS via a receptor-independent mechanism (Park et al, 2014). Xanthorrhizol, a natural sesquiterpenoid, also decreased cell viability and induced apoptosis via ROS-mediated p38 MAP kinase and JNK activation; it also decreased the incidence of buccal pouch tumors and increased survival in hamsters exposed to the carcinogen 7,12-dimethylbenz[a]anthracene (Kim et al, 2013). ...
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Oxidative species, including reactive oxygen species (ROS), are components of normal cellular metabolism and are required for intracellular processes as varied as proliferation, signal transduction, and apoptosis. In the situation of chronic oxidative stress, however, ROS contribute to various pathophysiologies and are involved in multiple stages of carcinogenesis. In head and neck cancers specifically, many common risk factors contribute to carcinogenesis via ROS-based mechanisms, including tobacco, areca quid, alcohol, and viruses. Given their widespread influence on the process of carcinogenesis, ROS and their related pathways are attractive targets for intervention. The effects of radiation therapy, a central component of treatment for nearly all head and neck cancers, can also be altered via interfering with oxidative pathways. These pathways are also relevant to the development of many benign oral diseases. In this review, we outline how ROS contribute to pathophysiology with a focus toward head and neck cancers and benign oral diseases, describing potential targets and pathways for intervention that exploit the role of oxidative species in these pathologic processes.This article is protected by copyright. All rights reserved.
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Amazingly, almost 50 years after the first demonstration of anticancer effects of cannabinoids in vitro and in vivo, well-designed clinical trials that definitively prove tumour-inhibiting effects in man are still missing. Whereas a large number of preclinical studies exist that describe tumour-inhibiting effects of cannabinoids, alone or in combination, but also in the form of medical cannabis or natural extracts in vitro, the number of in vivo studies is still limited. Even more limited are well-documented experiences in man. Most animal studies and experience with cannabinoids in man concern brain tumours. This review summarises the effects of phytocannabinoids in brain, breast, colorectal, head and neck, haematological, liver, lung, pancreatic, ovarian, prostate, and skin cancers in animal models and, if available, in patients. The large majority of animal studies demonstrate tumour-inhibiting effects of cannabinoids, thus confirming in vitro data. Experiences in cancer patients are almost exclusively limited to individual case reports and case series without a control group. Many questions are currently unanswered such as the role of pure cannabinoids compared to combinations, cannabinoids as the eventual sole cancer therapy, optimal dosages, or duration of treatment. Pure cannabidiol (CBD) seems to be superior to pure delta-9-tetrahydrocannabinol (THC) in experimental settings. The role of medical cannabis or extracts is less clear as they vary in their phytochemical composition. In conclusion, cannabis/cannabinoids may slow the progression of tumours. However, the hope that cannabinoids could eventually cure cancer as often spread in social media, is, at present, wishful thinking. Above all, well-designed clinical trials paired with long-term follow-up of cancer patients are needed.
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I am a head and neck radiation oncologist in a tertiary care practice in Minnesota. I am credentialed in the state of Minnesota to certify patients for medical cannabis. Over the last 6 years, I have certified select patients for medical cannabis as part of management of their cancer-related symptoms and effects of treatment. In this paper, I review my approach to incorporating medical cannabis into the management of patients with head and neck cancer.
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The endocannabinoid system is currently under intense investigation due to the therapeutic potential of cannabinoid-based drugs as treatment options for a broad variety of diseases including cancer. Besides the canonical endocannabinoid system that includes the cannabinoid receptors CB1 and CB2 and the endocannabinoids N-arachidonoylethanolamine (anandamide) and 2-arachidonoylglycerol, recent investigations suggest that other fatty acid derivatives, receptors, enzymes, and lipid transporters likewise orchestrate this system as components of the endocannabinoid system when defined as an extended signaling network. As such, fatty acids acting at cannabinoid receptors (e.g. 2-arachidonoyl glyceryl ether [noladin ether], N-arachidonoyldopamine) as well as endocannabinoid-like substances that do not elicit cannabinoid receptor activation (e.g. N-palmitoylethanolamine, N-oleoylethanolamine) have raised interest as anticancerogenic substances. Furthermore, the endocannabinoid-degrading enzymes fatty acid amide hydrolase and monoacylglycerol lipase, lipid transport proteins of the fatty acid binding protein family, additional cannabinoid-activated G protein-coupled receptors, members of the transient receptor potential family as well as peroxisome proliferator-activated receptors have been considered as targets of antitumoral cannabinoid activity. Therefore, this review focused on the antitumorigenic effects induced upon modulation of this extended endocannabinoid network.
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The endocannabinoid system encompassing cannabinoid receptors, endogenous receptor ligands (endocannabinoids), as well as enzymes conferring the synthesis and degradation of endocannabinoids has emerged as a considerable target for pharmacotherapeutical approaches of numerous diseases. Besides palliative effects of cannabinoids used in cancer treatment, phytocannabinoids, synthetic agonists, as well as substances that increase endogenous endocannabinoid levels have gained interest as potential agents for systemic cancer treatment. Accordingly, cannabinoid compounds have been reported to inhibit tumor growth and spreading in numerous rodent models. The underlying mechanisms include induction of apoptosis, autophagy, and cell cycle arrest in tumor cells as well as inhibition of tumor cell invasion and angiogenic features of endothelial cells. In addition, cannabinoids have been shown to suppress epithelial-to-mesenchymal transition, to enhance tumor immune surveillance, and to support chemotherapeutics’ effects on drug-resistant cancer cells. However, unwanted side effects include psychoactivity and possibly pathogenic effects on liver health. Other cannabinoids such as the nonpsychoactive cannabidiol exert a comparatively good safety profile while exhibiting considerable anticancer properties. So far experience with anticarcinogenic effects of cannabinoids is confined to in vitro studies and animal models. Although a bench-to-bedside conversion remains to be established, the current knowledge suggests cannabinoid compounds to serve as a group of drugs that may offer significant advantages for patients suffering from cancer diseases. The present review summarizes the role of the endocannabinoid system and cannabinoid compounds in tumor progression.
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Introduction: Molecular structures of the endocannabinoid system have gained interest as potential pharmacotherapeutical targets for systemic cancer treatment. Areas covered: The present review covers the contribution of the endocannabinoid system to cancer progression. Particular focus will be set on the accumulating preclinical data concerning antimetastatic, anti-invasive and anti-angiogenic mechanisms induced by cannabinoids. Expert opinion: The main goal of targeting endocannabinoid structures for systemic anticancer treatment is the comparatively good safety profile of cannabinoid compounds. In addition, antitumorigenic mechanisms of cannabinoids are not restricted to a single molecular cascade but involve multiple effects on various levels of cancer progression such as angiogenesis and metastasis. Particularly the latter effect has gained interest for pharmacological interventions. Thus, drugs aiming at the endocannabinoid system may represent potential "antimetastatics" for an upgrade of a future armamentarium against cancer diseases.
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G protein-coupled receptors (GPCRs) modulate a vast array of cellular processes. The current review gives an overview of the general characteristics of GPCRs and their role in physiological conditions. In addition, it describes the current knowledge of the physiological and pathophysiological functions of GPR55, an orphan GPCR, and how it can be exploited as a therapeutic target to combat various cancers.
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Cyclooxygenase 2 (COX-2) is upregulated in most colorectal cancers and is responsible for metabolism of the endogenous cannabinoid, anandamide, into prostaglandin-ethanolamides (PG-EAs). The aims of this study were to determine whether anandamide and PG-EAs induce cell death in colorectal carcinoma (CRC) cells, and whether high levels of COX-2 in CRC cells could be utilised for their specific targeting for cell death by anandamide. We determined the effect of anandamide on human CRC cell growth by measuring cell growth and cell death, whether this was dependent on COX-2 protein expression or enzyme activity, and the potential involvement of PG-EAs in induction of cell death. Anandamide inhibited the growth of CRC cell lines HT29 and HCA7/C29 (moderate and high COX-2 expressors, respectively) but had little effect on the very low COX-2 expressing CRC cell line, SW480. Induction of cell death in HT29 and HCA7/C29 cell lines was partially rescued by the COX-2 selective inhibitor NS398. Cell death induced by anandamide was neither apoptosis nor necrosis. Furthermore, inhibition of fatty acid amide hydrolase potentiated the non-apoptotic cell death, indicating that anandamide induced cell death was mediated via metabolism of anandamide by COX-2, rather than its degradation into arachidonic acid and ethanolamine. Interestingly, both PGE2-EA and PGD2-EA induced classical apoptosis. These findings suggest anandamide may be a useful chemopreventive/therapeutic agent for colorectal cancer as it targets cells that are high expressors of COX-2, and may also be used in the eradication of tumour cells that have become resistant to apoptosis.
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Cannabis, or marijuana, has been used for medicinal purposes for many years. Several types of cannabinoid medicines are available in the United States and Canada. Dronabinol (schedule III), nabilone (schedule II), and nabiximols (not U.S. Food and Drug Administration approved) are cannabis-derived pharmaceuticals. Medical cannabis or medical marijuana, a leafy plant cultivated for the production of its leaves and flowering tops, is a schedule I drug, but patients obtain it through cannabis dispensaries and statewide programs. The effect that cannabinoid compounds have on the cannabinoid receptors (CB(1) and CB(2) ) found in the brain can create varying pharmacologic responses based on formulation and patient characteristics. The cannabinoid Δ(9) -tetrahydrocannabinol has been determined to have the primary psychoactive effects; the effects of several other key cannabinoid compounds have yet to be fully elucidated. Dronabinol and nabilone are indicated for the treatment of nausea and vomiting associated with cancer chemotherapy and of anorexia associated with weight loss in patients with acquired immune deficiency syndrome. However, pain and muscle spasms are the most common reasons that medical cannabis is being recommended. Studies of medical cannabis show significant improvement in various types of pain and muscle spasticity. Reported adverse effects are typically not serious, with the most common being dizziness. Safety concerns regarding cannabis include the increased risk of developing schizophrenia with adolescent use, impairments in memory and cognition, accidental pediatric ingestions, and lack of safety packaging for medical cannabis formulations. This article will describe the pharmacology of cannabis, effects of various dosage formulations, therapeutics benefits and risks of cannabis for pain and muscle spasm, and safety concerns of medical cannabis use.
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Cannabinoids (CBs) have been found to exert antiproliferative effects upon a variety of cancer cells, including colorectal carcinoma cells. However, little is known about the signalling mechanisms behind the antitumoural effect in these cells, whether the effects are shared by endogenous lipids related to endocannabinoids, or whether such effects are synergistic with treatment paradigms currently used in the clinic. The aim of this preclinical study was to investigate the effect of synthetic and endogenous CBs and their related fatty acids on the viability of human colorectal carcinoma Caco-2 cells, and to determine whether CB effects are synergistic with those seen with the pyrimidine antagonist 5-fluorouracil (5-FU). The synthetic CB HU 210, the endogenous CB anandamide, the endogenous structural analogue of anandamide, N-arachidonoyl glycine (NAGly), as well as the related polyunsaturated fatty acids arachidonic acid and eicosapentaenoic acid showed antiproliferative and cytotoxic effects in the Caco-2 cells, as measured by using [(3)H]-thymidine incorporation assay, the CyQUANT proliferation assay and calcein-AM fluorescence. HU 210 was the most potent compound examined, followed by anandamide, whereas NAGly showed equal potency and efficacy as the polyunsaturated fatty acids. Furthermore, HU 210 and 5-FU produced synergistic effects in the Caco-2 cells, but not in the human colorectal carcinoma cell lines HCT116 or HT29. The compounds examined produced cytotoxic, rather than antiproliferative effects, by a mechanism not involving CB receptors, since the CB receptor antagonists AM251 and AM630 did not attenuate the effects, nor did pertussis toxin. However, alpha-tocopherol and the nitric oxide synthase inhibitor L-NAME attenuated the CB toxicity, suggesting involvement of oxidative stress. It is concluded that the CB system may provide new targets for the development of drugs to treat colorectal cancer.
Article
It has recently been found that 5-lipoxygenase (5-LO) and cytochrome P450-2J2 (CYP2J2), molecules capable of arachidonic acid (AA) metabolism, might promote cancer cell viability through several mechanisms similar to those of cyclooxygenase-2 (COX-2). We found that not only COX-2 expression, but also the expression of 5-LO and CYP2J2 is up-regulated in head and neck squamous cell carcinoma (HNSCC) cell lines. From these observations, we hypothesized that AA metabolism by 5-LO and/or CYP2J2 may lower the efficacy of anti-cancer effect by COX-2 inhibition. Although COX-2 was highly expressed in all cell lines tested, COX-2-specific inhibition showed little growth-inhibitory effect in some cell lines. Inhibition of COX-2 resulted in increased production of LTB(4) and 14-15-DHET/EET, metabolites of 5-LO and CYP2J2, respectively. Combined knock-down of COX-2 and 5-LO or CYP2J2 by siRNA results in a decrease in cell proliferation and VEGF production. Furthermore, these results are dependent on 5-LO and CYP2J2 expression in cells. Therefore, combined inhibition of COX-2 and 5-LO or CYP2J2 may be one way to overcome low efficacy of single inhibition of COX-2 in cancer cells. In addition, combined therapies should be chosen based on the expression of members of other AA metabolism pathways.
Article
To study the influences of endocannabinoid-anandamide (AEA) on the proliferation and apoptosis of the colorectal cancer cell line (CaCo-2) and to elucidate the effects of CB1 and lipid rafts, and to further elucidate the molecular mechanism and the effect of AEA on the generation and development of colorectal cancer. Human colorectal cancer cell line CaCo-2 was cultured in RPMI 1640 medium supplemented with 10% fetal bovine serum in 5% CO(2) atmosphere at 37°C. CaCo-2 cells were divided into different groups and treated with different concentrations of AEA, AEA + SR141716A, AEA + AM630 and AEA + methyl-β-cyclodextrin (MCD). MTT assay was used to determine the effects of AEA, its putative CB1, CB2 receptor antagonists (SR141716A and AM630) and MCD on the proliferation of CaCo-2 cells. Annexin V-PE/7AAD binding assay was used to detect apoptosis in the CaCo-2 cells. Western-blot was applied to check the expressions of CB1, CB2, p-AKT and caspase-3 proteins in different groups of CaCo-2 cells. AEA inhibited the proliferation of CaCo-2 cells in a concentration-dependent manner and the effect could be antagonized by SR141716A and MCD. The inhibiting rates were (21.52 ± 0.45)%, (42.16 ± 0.21)%, (73.64 ± 0.73)% and (83.28 ± 0.71)%, respectively, at different concentrations of AEA (5, 10, 20 and 40 µmol/L). The three groups (20 µmol/L AEA, 20 µmol/L AEA + 10 µmol/L SR141716A and 20 µmol/L AEA + 1 mmol/L MCD) showed different inhibiting rates [(73.64 ± 0.73)%, (16.15 ± 0.75)% and (12.58 ± 0.63)%], respectively. Annexin V-PE/7AAD binding assay showed that AEA induced apoptosis in the CaCo-2 cells and MCD could antagonize this effect. The apoptosis rates of the three groups (control, 20 µmol/L AEA and 20 µmol/L AEA + 1 mmol/L MCD) were (2.95 ± 0.73)%, (39.61 ± 0.73)% and (14.10 ± 0.64)%, respectively. The expressions of CB1, CB2, p-AKT and Caspase-3 proteins were all observed in the CaCo-2 cells. AEA inhibited p-AKT protein expression and induced caspase-3 protein expression. The two actions were also antagonized by MCD. AEA can strongly suppress the proliferation of colorectal cancer CaCo-2 cells via the CB1 receptor and membrane cholesterol-LRs and induce apoptosis via lipid rafts. Anandamide plays a very important role in the carcinogenesis and development of colorectal cancer. MCD is a critical member in this system.
Article
The endocannabinoid system comprises the cannabinoid receptors type 1 (CB1) and type 2 (CB2), their endogenous ligands (endocannabinoids), and the proteins responsible for their biosynthesis and degradation. This ubiquitous signalling system, that has attracted a great deal of scientist interest in the past 15 years, regulates several physiological and pathological functions. In mammals, among other functions, the endocannabinoid is involved in nervous, cardiovascular, metabolic, reproductive and immune functions. Finally, yet importantly, endocannabinoids are known to exert important antiproliferative actions in a great number of tumor cells including breast, brain, skin, thyroid, prostate and colorectal. The following review describes our current knowledge on the effects of two of the most studied endocannabinoids (AEA and 2-AG) on various types of tumor and summarizes the possible mechanism of observed antitumor effects.
Article
We have previously observed that cyclooxygenase-2 (COX-2) inhibition blocked the production of vascular endothelial growth factor (VEGF) in some head and neck squamous cell carcinoma (HNSCC) cells. However, as some HNSCC cells showed little response to COX-2 inhibition, although they highly expressed COX-2 and prostaglandin E2, we set out to elucidate what made this difference between them and focused on the possibility of the differential expression of COX-1. In western blotting, we found that COX-1 was expressed in SNU-1041 and SNU-1066, but not in SNU-1076 and PCI-50. Only in those cell lines without expression of COX-1 was VEGF production blocked meaningfully by small interfering RNA of COX-2. However, by cotreating with small interfering RNAs of COX-2 and COX-1, VEGF synthesis and prostaglandin E2 were inhibited in SNU-1041 and SNU-1066, similarly in SNU-1076 and PCI-50 with high expression of only COX-2. We also found that there was no difference in the pattern of prostaglandin synthesis between COX-2 and COX-1 through enzyme-linked immunosorbent assay for various prostaglandins. Our study suggests that, as COX-1 and COX-2 express and affect VEGF synthesis in HNSCC cells, we should check COX-1 expression in investigations on cancer treatment by inhibiting COX-2-induced prostaglandins.
Article
Endocannabinoids (ECs), anandamide (AEA) and 2-arachidonoylglycerol (2-AG), inhibit proliferation of carcinoma cells. Several enzymes hydrolyze ECs to reduce endogenous EC concentrations and produce eicosanoids that promote cell growth. In this study, we determined the effects of EC hydrolysis inhibitors and a putative EC, 2-arachidonylglyceryl ether (noladin ether, NE) on proliferation of prostate carcinoma (PC-3, DU-145, and LNCaP) cells. PC-3 cells had the least specific hydrolysis activity for AEA and administration of AEA effectively inhibited cell proliferation. The proliferation inhibition was blocked by SR141716A (a selective CB1R antagonist) but not SR144528 (a selective CB2R antagonist), suggesting a CB1R-mediated inhibition mechanism. On the other hand, specific hydrolysis activity for 2-AG was high and 2-AG inhibited proliferation only in the presence of EC hydrolysis inhibitors. NE inhibited proliferation in a concentration-dependent manner; however, SR141716A, SR144528 and pertussis toxin did not block the NE-inhibited proliferation, suggesting a CBR-independent mechanism of NE. A peroxisome proliferator-activated receptor gamma (PPARγ) antagonist GW9662 did not block the NE-inhibited proliferation, suggesting that PPARγ was not involved. NE also induced cell cycle arrest in G(0)/G(1) phase in PC-3 cells. NE inhibited the nuclear translocation of nuclear factor-kappa B (NF-κB p65) and down-regulated the expression of cyclin D1 and cyclin E in PC-3 cells, suggesting the NF-κB/cyclin D and cyclin E pathways are involved in the arrest of G1 cell cycle and inhibition of cell growth. These results indicate therapeutic potentials of EC hydrolysis inhibitors and the enzymatically stable NE in prostate cancer.
Article
It has been observed that several cyclooxygenase-2 (COX-2) inhibitory chemicals might inhibit proliferation of various cancer cells through COX-2-independent action. We also identified that celecoxib more selectively kills cell lines derived from head and neck squamous cell carcinoma (HNSCC) than its non-cancerous counterparts, irrespective of COX-2 expression. Herein, we investigated whether the regulation of mitogen-activated protein kinases activity might be one of the main mechanisms related to a conspicuous COX-2-independent tumor-killing effect of celecoxib in HNSCC cell lines. We assessed the effect of celecoxib on extracellular signal-regulated kinase (ERK), p38, and c-Jun NH2-terminal kinase activity by a transcription factor activation assay then evaluated, if these factors might be involved in the COX-2-independent tumor-killing effect of celecoxib by blocking their activity. We found that the blocking activation of ERK and/or p38 could reverse the celecoxib-induced cell growth inhibition by 50-80% in HNSCC cell lines, but it was not tested in cancer cells of other types. In conclusion, our study suggests that most COX-2-independent tumor-killing action of celecoxib is mediated by the upregulation of ERK and/or p38 activity in HNSCC cells. These results encourage investigation on the underlying mechanisms and detailed outcomes of mitogen-activated protein kinases activation by celecoxib more concisely, for using its excellent tumor-killing effect more safely in the clinical field of cancer treatment.
Article
Since many studies have suggested the impact of dietary polyunsaturated fatty acids on cancer progression and prognosis, there is an assumption of possible pre-sensitizing effects of their application in combined treatment. The present work evaluates modulation of photodynamic therapy (PDT) with hypericin by pre-treatment with n-3 and n-6 fatty acids in HT-29 and HeLa tumour cells. We observed stimulation of cytotoxic effects by docosahexaenoic acid (n-3) and arachidonic acid (n-6) in several stages of action in both cell lines. Treatment with either fatty acids or photodynamic therapy alone induced apoptosis in a dose- and time-dependent manner; however the effect was even more striking in mutual combination applied as pre-treatment with fatty acids prior to photodynamic therapy. Moreover, the combination also induced changes in membrane lipid composition leading to alteration in cell membrane fluidity. Increased toxicity of combined treatment was also confirmed by the presence of oxidative stress demonstrated by ROS production, RNS accumulation and increased presence of lipoperoxides. In conclusion, we suggest that pre-treatment with polyunsaturated fatty acids may contribute to cytotoxic effects induced by photodynamic therapy with hypericin.
Article
Despite recent advances in understanding colorectal tumour biology, there is still a need to improve the 5-year survival rate of patients with colorectal cancer as approximately 40% of patients presenting with advanced disease will remain resistant to therapy. One of the major contributing factors in resistance to therapy is the failure of colorectal tumour cells to undergo apoptosis. Hence there is an urgent need to develop novel therapeutic approaches that can target apoptosis-resistant cells. To this end, we investigated the potential efficacy of the endogenous cannabinoid anandamide to induce cell death in apoptosis-resistant colon cancer cells. Here, for the first time, we show that anandamide can induce cell death in the apoptosis-resistant HCT116 Bax-/- colorectal cell line. Importantly, we provide direct genetic evidence that this induction of cell death is dependent on COX-2 expression. Interestingly, increased COX-2 expression also sensitised the SW480 colorectal cancer cell line (low endogenous COX-2) to anandamide-induced death, whereas COX-2 suppression by RNAi inhibited anandamide-induced cell death in the HCA7 colorectal cancer cell line (high endogenous COX-2 expression). This COX-2-dependent death was independent of cannabinoid receptor engagement (CB1 or CB2), and not a direct consequence of reactive oxygen species (ROS) formation. This study demonstrates a novel utilisation for COX-2 expression, targeting apoptotic defective colorectal cancer cells for destruction by anandamide. As COX-2 is not expressed in the normal colorectal epithelium, but highly expressed in colorectal tumours and apoptosis resistance contributes to treatment failure, these data suggest that anandamide has the potential to be an effective therapeutic in colorectal cancer.
Article
The endocannabinoid system comprises specific cannabinoid receptors such as Cb1 and Cb2, the endogenous ligands (anandamide and 2-arachidonyl glycerol among others) and the proteins responsible for their synthesis and degradation. This system has become the focus of research in recent years because of its potential therapeutic value several disease states. The following review describes our current knowledge of the changes that occur in the endocannabinoid system during carcinogenesis and then focuses on the effects of anandamide on various aspects of the carcinogenic process such as growth, migration, and angiogenesis in tumors from various origins.
Article
Acylethanolamides are lipid substances widely distributed in the body, generated from a membrane phospholipid precursor, N-acylphosphatidylethanolamine (NAPE). The recent identification of arachidonoyl ethanolamide (anandamide or AEA) as an endogenous cannabinoid ligand has focused attention on acylethanolamides, which has further increased with the subsequent identification of related additional acylethanolamides with signaling function, such as oleoylethanolamide (OEA) and palmitoylethanolamide (PEA). Most of the biological functions of anandamide are mediated by the two G protein-coupled cannabinoid receptors identified to date, CB(1) and CB(2), with the transient receptor potential vanilloid-1 receptor being an additional potential target. There has been increasing pharmacological evidence for the existence of additional cannabinoid receptors, with the orphan G protein-coupled receptor GPR55 being the most actively scrutinized, and is one of the subjects of this review. The other receptor reviewed here is GPR119, which can recognize OEA and PEA. These two acylethanolamides, although structurally related to anandamide, do not interact with classical cannabinoid receptors. Instead, they have high affinity for the nuclear receptor PPARalpha, which is believed to mediate many of their biological effects.
Article
Nonmelanoma skin cancer is the most prevalent cancer in the United States with approximately 1.25 million new cases diagnosed each year. Cyclooxygenase-2 (COX-2) expression is commonly elevated in these and other epithelial tumors. Cyclooxygenases metabolize arachidonic acid to prostaglandins, which promote growth and survival of tumor cells. COX-2 also metabolizes endocannabinoids forming prostaglandin-ethanolamides (PG-EA); however, the role of these lipid molecules in tumor cell survival is unclear. The goal of this research is to determine if the metabolic products of COX-2 contribute to endocannabinoid-induced cell death. Anandamide [also known as arachidonyl ethanolamide (AEA)] induced cell death in the COX-2 overexpressing squamous carcinoma cell line JWF2. In contrast, AEA did not initiate cell death in HaCaT keratinocytes, which express low basal levels of COX-2. Resistance to AEA-mediated cell death in HaCaT cells was reversed by overexpressing COX-2 in these cells. Next, ELISA assays were carried out to identify prostaglandins involved in AEA-mediated cell death. D-type prostaglandins were predominantly formed in AEA-exposed JWF2 cells although significant increases in E- and F-type prostaglandins were also seen. Cells were then treated with various prostaglandins or PG-EA to determine the contribution of each to AEA-induced cell death. PGD(2) and PGD(2)-EA were found to be cytotoxic to JWF2 keratinocytes and the PGD(2) dehydration products, PGJ(2) and 15-deoxy Delta(12,14) PGJ(2), were also potent inducers of cell death. These results suggest that AEA selectively induces cell death in tumorigenic keratinocytes due to COX-2 overexpression and the resulting metabolism of AEA to cytotoxic prostaglandins.
Article
Cannabinoids have received renewed interest due to their antitumorigenic effects. Using human cervical carcinoma cells (HeLa), this study investigates the role of cyclooxygenase-2 (COX-2) in apoptosis elicited by the endocannabinoid analog R(+)-methanandamide (MA). COX-2 expression was assessed by RT-PCR and Western blotting. PGE2/PGD2 levels in cell culture supernatants and DNA fragmentation were measured by ELISA. MA led to an induction of COX-2 expression, PGD2 and PGE2 synthesis. Cells were significantly less sensitive to MA-induced apoptosis when COX-2 was suppressed by siRNA or the selective COX-2 inhibitor NS-398. COX-2 expression and apoptosis by MA was also prevented by the ceramide synthase inhibitor fumonisin B1, but not by antagonists to cannabinoid receptors and TRPV1. In line with the established role of peroxisome proliferator-activated receptor gamma (PPARgamma) in the proapoptotic action of PGs of the D and J series, inhibition of MA-induced apoptosis was also achieved by siRNA targeting lipocalin-type PGD synthase (L-PGDS) or PPARgamma. A role of COX-2 and PPARgamma in MA-induced apoptosis was confirmed in another human cervical cancer cell line (C33A) and in human lung carcinoma cells (A549). This study demonstrates COX-2 induction and synthesis of L-PGDS-derived, PPARgamma-activating PGs as a possible mechanism of apoptosis by MA.
Article
Delta(9)-Tetrahydrocannabinol, the active agent of Cannabis sativa, exhibits well-documented antitumor properties, but little is known about the possible effects mediated by endogenous cannabinoids on human tumors. In the present study, we analyzed the effect of arachidonyl ethanolamide (AEA) on cervical carcinoma (CxCa) cell lines. To assess the sensitivity of CxCa cells to AEA, we selected three cell lines that were exposed to increasing doses of AEA with or without antagonists to receptors to AEA. DNA fragmentation and caspase-7 activity were used as apoptosis markers. The expression of receptors to AEA were analyzed in CxCa cell lines as well as CxCa biopsies. The major finding was that AEA induced apoptosis of CxCa cell lines via aberrantly expressed vanilloid receptor-1, whereas AEA binding to the classical CB1 and CB2 cannabinoid receptors mediated a protective effect. Furthermore, unexpectedly, a strong expression of the three forms of AEA receptors was observed in ex vivo CxCa biopsies. Overall, these data suggest that the specific targeting of VR1 by endogenous cannabinoids or synthetic molecules offers attractive opportunities for the development of novel potent anticancer drugs.
Article
Fatty acid amide hydrolase (FAAH) is an integral membrane enzyme within the amidase-signature family that terminates the action of several endogenous lipid messengers, including oleamide and the endocannabinoid anandamide. The hydrolysis of such messengers leads to molecules devoid of biological activity, and, therefore, modulates a number of neurobehavioral processes in mammals, including pain, sleep, feeding, and locomotor activity. Investigations into the structure and function of FAAH, its biological and therapeutic implications, as well as a description of different families of FAAH inhibitors are the topic of this review.