Resveratrol inhibits proliferation of human epidermoid carcinoma A431 cells by modulating MEK1 and AP-1 signalling pathways

Reactive oxygen species, toxicity, oxidative stress, and antioxidants: chronic diseases and aging

A physiological level of oxygen/nitrogen free radicals and non-radical reactive species (collectively known as ROS/RNS) is termed oxidative eustress or "good stress" and is characterized by low to mild levels of oxidants involved in the regulation of various biochemical transformations such as carboxylation, hydroxylation, peroxidation, or modulation of signal transduction pathways such as Nuclear factor-κB (NF-κB), Mitogen-activated protein kinase (MAPK) cascade, phosphoinositide-3-kinase, nuclear factor erythroid 2-related factor 2 (Nrf2) and other processes. Increased levels of ROS/RNS, generated from both endogenous (mitochondria, NADPH oxidases) and/or exogenous sources (radiation, certain drugs, foods, cigarette smoking, pollution) result in a harmful condition termed oxidative stress ("bad stress"). Although it is widely accepted, that many chronic diseases are multifactorial in origin, they share oxidative stress as a common denominator. Here we review the importance of oxidative stress and the mechanisms through which oxidative stress contributes to the pathological states of an organism. Attention is focused on the chemistry of ROS and RNS (e.g. superoxide radical, hydrogen peroxide, hydroxyl radicals, peroxyl radicals, nitric oxide, peroxynitrite), and their role in oxidative damage of DNA, proteins, and membrane lipids. Quantitative and qualitative assessment of oxidative stress biomarkers is also discussed. Oxidative stress contributes to the pathology of cancer, cardiovascular diseases, diabetes, neurological disorders (Alzheimer's and Parkinson's diseases, Down syndrome), psychiatric diseases (depression, schizophrenia, bipolar disorder), renal disease, lung disease (chronic pulmonary obstruction, lung cancer), and aging. The concerted action of antioxidants to ameliorate the harmful effect of oxidative stress is achieved by antioxidant enzymes (Superoxide dismutases-SODs, catalase, glutathione peroxidase-GPx), and small molecular weight antioxidants (vitamins C and E, flavonoids, carotenoids, melatonin, ergothioneine, and others). Perhaps one of the most effective low molecular weight antioxidants is vitamin E, the first line of defense against the peroxidation of lipids. A promising approach appears to be the use of certain antioxidants (e.g. flavonoids), showing weak prooxidant properties that may boost cellular antioxidant systems and thus act as preventive anticancer agents. Redox metal-based enzyme mimetic compounds as potential pharmaceutical interventions and sirtuins as promising therapeutic targets for age-related diseases and anti-aging strategies are discussed.

Cancer Chemoprevention: A Strategic Approach Using Phytochemicals

Cancer chemoprevention approaches are aimed at preventing, delaying, or suppressing tumor incidence using synthetic or natural bioactive agents. Mechanistically, chemopreventive agents also aid in mitigating cancer development, either by impeding DNA damage or by blocking the division of premalignant cells with DNA damage. Several pre-clinical studies have substantiated the benefits of using various dietary components as chemopreventives in cancer therapy. The incessant rise in the number of cancer cases globally is an issue of major concern. The excessive toxicity and chemoresistance associated with conventional chemotherapies decrease the success rates of the existent chemotherapeutic regimen, which warrants the need for an efficient and safer alternative therapeutic approach. In this scenario, chemopreventive agents have been proven to be successful in protecting the high-risk populations from cancer, which further validates chemoprevention strategy as rational and promising. Clinical studies have shown the effectiveness of this approach in managing cancers of different origins. Phytochemicals, which constitute an appreciable proportion of currently used chemotherapeutic drugs, have been tested for their chemopreventive efficacy. This review primarily aims to highlight the efficacy of phytochemicals, currently being investigated globally as chemopreventives. The clinical relevance of chemoprevention, with special emphasis on the phytochemicals, curcumin, resveratrol, tryptanthrin, kaempferol, gingerol, emodin, quercetin genistein and epigallocatechingallate, which are potential candidates due to their ability to regulate multiple survival pathways without inducing toxicity, forms the crux of this review. The majority of these phytochemicals are polyphenols and flavanoids. We have analyzed how the key molecular targets of these chemopreventives potentially counteract the key drivers of chemoresistance, causing minimum toxicity to the body. An overview of the underlying mechanism of action of these phytochemicals in regulating the key players of cancer progression and tumor suppression is discussed in this review. A summary of the clinical trials on the important phytochemicals that emerge as chemopreventives is also incorporated. We elaborate on the pre-clinical and clinical observations, pharmacokinetics, mechanism of action, and molecular targets of some of these natural products. To summarize, the scope of this review comprises of the current status, limitations, and future directions of cancer chemoprevention, emphasizing the potency of phytochemicals as effective chemopreventives.

Resveratrol-Induced Signal Transduction in Wound Healing

Resveratrol is a well-known polyphenol that harbors various health benefits. Besides its well-known anti-oxidative potential, resveratrol exerts anti-inflammatory, pro-angiogenic, and cell-protective effects. It seems to be a promising adjuvant for various medical indications, such as cancer, vascular, and neurodegenerative diseases. Additionally, resveratrol was shown to display beneficial effects on the human skin. The polyphenol is discussed to be a feasible treatment approach to accelerate wound healing and prevent the development of chronic wounds without the drawback of systemic side effects. Despite resveratrol’s increasing popularity, its molecular mechanisms of action are still poorly understood. To take full advantage of resveratrol’s therapeutic potential, a profound knowledge of its interactions with its targets is needed. Therefore, this review highlights the resveratrol-induced molecular pathways with particular focus on the most relevant variables in wound healing, namely inflammation, oxidative stress, autophagy, collagen proliferation and angiogenesis.

Anti-Inflammatory Action and Mechanisms of Resveratrol

Resveratrol (3,4',5-trihy- droxystilbene), a natural phytoalexin polyphenol, exhibits anti-oxidant, anti-inflammatory, and anti-carcinogenic properties. This phytoalexin is well-absorbed and rapidly and extensively metabolized in the body. Inflammation is an adaptive response, which could be triggered by various danger signals, such as invasion by microorganisms or tissue injury. In this review, the anti-inflammatory activity and the mechanism of resveratrol modulates the inflammatory response are examined. Multiple experimental studies that illustrate regulatory mechanisms and the immunomodulatory function of resveratrol both in vivo and in vitro. The data acquired from those studies are discussed.

An Update on the Role of Dietary Phytochemicals in Human Skin Cancer: New Insights into Molecular Mechanisms

Human skin is continuously subjected to environmental stresses, as well as extrinsic and intrinsic noxious agents. Although skin adopts various molecular mechanisms to maintain homeostasis, excessive and repeated stresses can overwhelm these systems, leading to serious cutaneous damage, including both melanoma and non-melanoma skin cancers. Phytochemicals present in the diet possess the desirable effects of protecting the skin from damaging free radicals as well as other benefits. Dietary phytochemicals appear to be effective in preventing skin cancer and are inexpensive, widely available, and well tolerated. Multiple in vitro and in vivo studies have demonstrated the significant anti-inflammatory, antioxidant, and anti-angiogenic characteristics of dietary phytochemicals against skin malignancy. Moreover, dietary phytochemicals affect multiple important cellular processes including cell cycle, angiogenesis, and metastasis to control skin cancer progression. Herein, we discuss the advantages of key dietary phytochemicals in whole fruits and vegetables, their bioavailability, and underlying molecular mechanisms for preventing skin cancer. Current challenges and future prospects for research are also reviewed. To date, most of the chemoprevention investigations have been conducted preclinically, and additional clinical trials are required to conform and validate the preclinical results in humans.

Role of Resveratrol in Regulating Cutaneous Functions

Protective role of the skin is against external insults and maintenance of electrolyte homeostasis of the body. Cutaneous dysfunction can account for the development of both cutaneous and systemic disorders. Thus, improvements in cutaneous functions can benefit a number of extracutaneous and cutaneous functions. Resveratrol, a natural ingredient, displays multiple benefits for various systems/organs, including the skin. The benefits of resveratrol for cutaneous functions include stimulation of keratinocyte differentiation and antimicrobial peptide expression, inhibition of keratinocyte proliferation and cutaneous inflammation, UV protection, anticancer, antiaging, and inhibition of melanogenesis. The mechanisms of action of resveratrol include activation of sirtuin 1 and nuclear factor erythroid 2-related factor 2, and inhibition of mitogen-activated protein kinase signaling. Evidence suggests that topical resveratrol could be a valuable alternative not only for daily skin care, but also for the prevention and treatment of various cutaneous disorders. This review summarizes the benefits of resveratrol for cutaneous functions.

Therapeutic Approaches of Resveratrol on Endometriosis via Anti-Inflammatory and Anti-Angiogenic Pathways

Endometriosis represents a severe gynecological pathology, defined by implantation of endometrial glands and stroma outside the uterine cavity. This pathology affects almost 15% of women during reproductive age and has a wide range of consequences. In affected women, infertility has a 30% rate of prevalence and endometriosis implants increase the risk of ovarian cancer. Despite long periods of studies and investigations, the etiology and pathogenesis of this disease still remain not fully understood. Initially, endometriosis was related to retrograde menstruation, but new theories have been launched, suggesting that chronic inflammation can influence the development of endometriosis because inflammatory mediators have been identified elevated in patients with endometriosis, specifically in the peritoneal fluid. The importance of dietary phytochemicals and their effect on different inflammatory diseases have been highlighted, and nowadays more and more studies are focused on the analysis of nutraceuticals. Resveratrol is a phytoestrogen, a natural polyphenolic compound with antiproliferative and anti-inflammatory actions, found in many dietary sources such as grapes, wine, peanuts, soy, berries, and stilbenes. Resveratrol possesses a significant anti-inflammatory effect via inhibition of prostaglandin synthesis and it has been proved that resveratrol can exhibit apoptosis-inducing activities. From the studies reviewed in this paper, it is clear that the anti-inflammatory effect of this natural compound can contribute to the prevention of endometriosis, this phenolic compound now being considered a new innovative drug in the prevention and treatment of this disease.

A novel tetrazole analogue of resveratrol is a potent anticancer agent

A series of novel tetrazole analogues of resveratrol were synthesized and evaluated for their anti-leukemic activity against an extensive panel of human cancer cell lines and against the MV4-11 AML cell line. These molecules were designed as drug-like derivatives of the resveratrol analogue DMU-212 and its cyano derivatives. Four compounds 8g, 8h, 10a and 10b exhibited LD₅₀ values of 4.60 µM, 0.02 µM, 1.46 µM, and 1.08 µM, respectively, against MV4-11 leukemia cells. The most potent compounds, 8h and 10b, were also found to be active against an extensive panel of human hematological and solid tumor cell lines; compound 8h was the most potent compound with GI₅₀ values <10 nM against more than 90% of the human cancer cell lines in the 60-cell panel. Analogues 8g, 8h, 10a and 10b were also tested for their ability to inhibit the polymerization of tubulin, and compound 8h was found to be the most potent analogue. Molecular modeling studies demonstrated that 8h binds to the colchicine binding site on tubulin. Thus, compound 8h is considered to be a lead druglike molecule from this tetrazole series of compounds.

Resveratrol induces apoptosis in SGC-7901 gastric cancer cells

The aim of the present study was to investigate the effect of resveratrol on apoptosis in SGC-7901 gastric cancer cells and its molecular mechanisms of action. Following resveratrol treatment, the inhibition rate of SGC-7901 cells was determined using an MTT assay. The morphological changes in apoptosis were observed by fluorescence microscopy based on acridine orange/ethidium bromide double staining. Furthermore, cell cycle and apoptosis were detected using flow cytometry, and the expression levels of nuclear factor κB (NF-κB) as well as apoptosis-associated proteins [B-cell lymphoma 2 (Bcl-2), Bcl-2-associated X protein (Bax), cleaved caspase-3 and cleaved caspase-8] were analyzed by western blotting. The results of the present study indicated that resveratrol was able to significantly inhibit the viability of SGC-7901 cells in a dose- and time-dependent manner. When treated with 200 µM resveratrol, the inhibition rate of SGC-7901 cells reached ~50%. In the presence of resveratrol, the proportion of apoptotic cells was also increased in a dose-dependent manner. Flow cytometry revealed that resveratrol induced S-phase arrest of SGC-7901 cells. When treated with 50, 200 and 400 µM resveratrol, the proportions of SGC-7901 cells in the S-phase were respectively increased to 33.8±2.42, 60.01±2.43 and 56.05±2.67%, compared with 25.62±3.29% for the control group cells in S-phase. Additionally, the levels of the pro-apoptotic proteins Bax, cleaved caspase-3 and cleaved caspase-8 were upregulated in a dose-dependent manner, whereas the level of the anti-apoptotic protein Bcl-2 was downregulated dose-dependently. Importantly, the activation of NF-κB (p65) was evidently decreased following treatment with resveratrol compared with in the control group. In conclusion, the results of the present study revealed that resveratrol was able to inhibit viability and induce apoptosis in SGC-7901 cells by suppressing NF-κB activation. Therefore, resveratrol may be considered as a potential drug candidate for the treatment of gastric cancer.

Modulating the Global Response Regulator, LuxO of V. cholerae Quorum Sensing System Using a Pyrazine Dicarboxylic Acid Derivative (PDCApy): An Antivirulence Approach

Vibrio cholerae is a Gram-negative pathogen which causes acute diarrhoeal disease, cholera by the expression of virulence genes through quorum sensing (QS) mechanism. The QS circuit of V. cholerae is controlled by the global quorum regulator, LuxO, which at low cell density (LCD) state produces major virulence factors such as, toxin co-regulated pilus (TCP) and cholera toxin (CT) to mediate infection. On the contrary, at the high cell density (HCD) state the virulent genes are downregulated and the vibrios are detached from the host intestinal epithelial cells, promoted by HapA protease. Hence, targeting the global regulator LuxO would be a promising approach to modulate the QS to curtail V. cholerae pathogenesis. In our earlier studies, LuxO targeted ligand, 2,3 pyrazine dicarboxylic acid (PDCA) and its derivatives having desired pharmacophore properties were chemically synthesized and were shown to have biofilm inhibition as well as synergistic activity with the conventionally used antibiotics. In the present study, the QS modulatory effect of the PDCA derivative with pyrrolidine moiety designated as PDCA^py against the V. cholerae virulence gene expression was analyzed at various growth phases. The data significantly showed a several fold reduction in the expression of the genes, tcp and ct whereas the expression of hapR was upregulated at the LCD state. In addition, PDCA^py reduced the adhesion and invasion of the vibrios onto the INT407 intestinal cell lines. Collectively, our data suggest that PDCA^py could be a potential QS modulator (QSM) for the antivirulence therapeutic approach.

Resveratrol and endometriosis: In vitro and animal studies and underlying mechanisms (Review)

Endometriosis is characterized by the existence of endometrial tissue and stroma exterior to the uterus. Despite the high prevalence, the etiology of endometriosis remains elusive. The search for the most promising compounds for treatment of endometriosis has led to the identification of resveratrol. Resveratrol, a plant-derived polyphenolic phytoalexin, demonstrates broad-spectrum health beneficial effects, including anti-proliferative, anti-inflammatory, antineoplastic and antioxidant. Because of these properties and its wide distribution in plants, resveratrol is proposed as a great potential to treat endometriosis. In animal models of endometriosis, resveratrol supplementation has displayed beneficial results as it decreased the number and volume of endometrial implants, suppressed proliferation, vascularization, inflammation, cell survival and increased apoptosis. On the other hand, resveratrol treatment in-vitro studies, reduced invasiveness of endometriotic stromal cells (ESCs) and suppressed their inflammatory responses. In this review, we will summarize the recent studies in in-vitro and animal studies on resveratrol and endometriosis.

Growth-Inhibiting Activity of Resveratrol Imine Analogs on Tumor Cells In Vitro

Although resveratrol exerts manifold antitumorigenic effects in vitro, its efficacy against malignancies in vivo seems limited. This has been increasingly recognized in recent years and has prompted scientists to search for structurally related compounds with more promising anticarcinogenic and/or pharmacokinetic properties. A class of structurally modified resveratrol derivatives, so-called resveratrol imine analogs (IRA's), might meet these requirements. Therefore, the biological activity of five of these compounds was examined and compared to that of resveratrol. Firstly, the antiproliferative potency of all five IRA's was investigated using the p53 wildtype-carrying colorectal carcinoma cell line HCT-116wt. Then, using the former and a panel of various other tumor cell lines (including the p53 knockout variant HCT-116p53-/-), the growth-inhibiting and cell cycle-disturbing effects of the most potent IRA (IRA 5, 2-[[(2-hydroxyphenyl)methylene]amino]-phenol) were studied as was its influence on cyclooxygenase-2 expression and activity. Finally, rat liver microsomes were used to determine the metabolic stability of that compound. IRA 5 was clearly the most potent compound in HCT-116wt cells, with an unusually high IC50-value of 0.6 μM. However, in the other five cell lines used, the antiproliferative activity was mostly similar to resveratrol and the effects on the cell cycle were heterogeneous. Although all cell lines were affected by treatment with IRA 5, cells expressing functional p53 seemed to react more sensitively, suggesting that this protein plays a modulating role in the induction of IRA 5-mediated biological effects. Lastly, IRA 5 led to contradictory effects on cyclooxygenase-2 expression and activity and was less glucuronidated than resveratrol. As IRA 5 is approximately 50 times more toxic towards HCT-116wt cells, exerts different effects on the cyclooxygenase-2 and is metabolized to a lesser extent, it shows certain advantages over resveratrol and could therefore serve as basis for additional chemical modifications, potentially yielding compounds with more favorable biological and pharmacokinetic features.

Polyphenols in Health and Disease

Deadly diseases, such as cardiovascular diseases and cancer, remain the major health problems worldwide. Research in cardiovascular diseases and genome-wide association studies were successful in indentifying the gene loci associated with these threatening diseases. Yet, a substantial number of casual factors remain unexplained. Over the last decade, a better understanding of molecular and biochemical mechanisms of cardiac diseases led to developing a rationale for combining various protective agents, such as polyphenols, to target multiple signaling pathways. The present review article summarizes recent advances of the use of polyphenols against diseases, such as cardiac diseases.

Unraveling the Anticancer Effect of Curcumin and Resveratrol

Resveratrol and curcumin are natural products with important therapeutic properties useful to treat several human diseases, including cancer. In the last years, the number of studies describing the effect of both polyphenols against cancer has increased; however, the mechanism of action in all of those cases is not completely comprehended. The unspecific effect and the ability to interfere in assays by both polyphenols make this challenge even more difficult. Herein, we analyzed the anticancer activity of resveratrol and curcumin reported in the literature in the last 11 years, in order to unravel the molecular mechanism of action of both compounds. Molecular targets and cellular pathways will be described. Furthermore, we also discussed the ability of these natural products act as chemopreventive and its use in association with other anticancer drugs.

A Novel Resveratrol Based Tubulin Inhibitor Induces Mitotic Arrest and Activates Apoptosis in Cancer Cells

Resveratrol is one of the most widely studied bioactive plant polyphenols which possesses anticancer properties. Previously we have reported synthesis, characterization and identification of a novel resveratrol analog, SS28. In the present study, we show that SS28 induced cytotoxicity in several cancer cell lines ex vivo with an IC₅₀ value of 3–5 μM. Mechanistic evaluation of effect of SS28 in non-small cell lung cancer cell line (A549) and T-cell leukemic cell line (CEM) showed that it inhibited Tubulin polymerization during cell division to cause cell cycle arrest at G2/M phase of the cell cycle at 12–18 h time period. Immunofluorescence studies confirmed the mitotic arrest upon treatment with SS28. Besides, we show that SS28 binds to Tubulin with a dissociation constant of 0.414 ± 0.11 μM. Further, SS28 treatment resulted in loss of mitochondrial membrane potential, activation of Caspase 9 and Caspase 3, leading to PARP-1 cleavage and finally cell death via intrinsic pathway of apoptosis. Importantly, treatment with SS28 resulted in regression of tumor in mice. Hence, our study reveals the antiproliferative activity of SS28 by disrupting microtubule dynamics by binding to its cellular target Tubulin and its potential to be developed as an anticancer molecule.

Resveratrol for breast cancer prevention and therapy: Preclinical evidence and molecular mechanisms

Globally, breast cancer is the most frequently diagnosed cancer among women. The major unresolved problems with metastatic breast cancer is recurrence after receiving objective response to chemotherapy, drug-induced side effects of first line chemotherapy and delayed response to second line of treatment. Unfortunately, very few options are available as third line treatment. It is clear that under such circumstances there is an urgent need for new and effective drugs. Phytochemicals are among the most promising chemopreventive treatment options for the management of cancer. Resveratrol (3,5,4'-trihydroxy-trans-stilbene), a non-flavonoid polyphenol present in several dietary sources, including grapes, berries, soy beans, pomegranate and peanuts, has been shown to possess a wide range of health benefits through its effect on a plethora of molecular targets.The present review encompasses the role of resveratrol and its natural/synthetic analogue in the light of their efficacy against tumor cell proliferation, metastasis, epigenetic alterations and for induction of apoptosis as well as sensitization toward chemotherapeutic drugs in various in vitro and in vivo models of breast cancer. The roles of resveratrol as a phytoestrogen, an aromatase inhibitor and in stem cell therapy as well as adjuvent treatment are also discussed. This review explores the full potential of resveratrol in breast cancer prevention and treatment with current limitations, challenges and future directions of research.

The main potentialities of resveratrol for drug delivery systems

Resveratrol (RSV), a natural polyphenol found in grapes, was found to be effective in the prevention and therapy of several diseases, however, it does have unfavourable physicochemical properties. In this context, an increasing number of studies have aimed at developing novel therapeutic systems for its delivery to overcome these disadvantages. This review focuses on the mechanisms of action and therapeutic applications. Finally, it also describes some tested formulations for RSV administration, controlled release and targeting, developed with the purpose of increasing RSV bioavailability.

Shikonin causes cell-cycle arrest and induces apoptosis by regulating the EGFR-NF-κB signalling pathway in human epidermoid carcinoma A431 cells

Shikonin, a naphthoquinone pigment isolated from the Chinese herbal Zicao, has been shown to exhibit antioxidant and anticancer effects. In the present study, we investigated the antiproliferative and pro-apoptotic effects of shikonin on A431 cells and explored the underlying molecular mechanisms. In the present study, our results showed that shikonin significantly inhibited the growth of A431 cells in a concentration- and time-dependent manner, and caused cell cycle arrest by upregulation of p21 and p27, and downregulation of cyclins and cyclin-dependent kinases. In addition, shikonin evidently induced apoptosis due to decreasing Bcl-2 expression, increasing Bax expression, activating caspase and inactivating NF-κB, while pretreatment with a pan-caspase inhibitor Z-Asp-CH2-DCB abrogated shikonin-induced apoptosis. Moreover, EGF could significantly increase the NF-κB DNA-binding activity and reversed the shikonin-induced inactivation of NF-κB. As anticipated AG1478 (EGFR inhibitor) and Bay11-7082 (NF-κB inhibitor) blocked EGF-reversed the inactivation of NF-κB induced by shikonin. Our data also showed that EGF could evidently reverse the shikonin-induced decreases in cell viability and increases in apoptosis. Then, the NF-κB inhibitors such as Bay11-7082, SN50, Helenalin and the EGFR inhibitor AG1478 and its downstream inhibitor such as PI3K inhibitor LY294002 and STAT3 inhibitor Stattic dramatically blocked EGF-reversed decreases in cell viability and increases in apoptosis induced by shikonin. Collectively, our findings indicated that shikonin inhibited cell growth and caused cell cycle arrest of the A431 cells through the regulation of apoptosis. Moreover, these effects were mediated at least partially by suppressing the activation of the EGFR-NF-κB signaling pathways.

In vitro and in vivo antitumoral effects of combinations of polyphenols, or polyphenols and anticancer drugs: perspectives on cancer treatment

Carcinogenesis is a multistep process triggered by genetic alterations that activate different signal transduction pathways and cause the progressive transformation of a normal cell into a cancer cell. Polyphenols, compounds ubiquitously expressed in plants, have anti-inflammatory, antimicrobial, antiviral, anticancer, and immunomodulatory properties, all of which are beneficial to human health. Due to their ability to modulate the activity of multiple targets involved in carcinogenesis through direct interaction or modulation of gene expression, polyphenols can be employed to inhibit the growth of cancer cells. However, the main problem related to the use of polyphenols as anticancer agents is their poor bioavailability, which might hinder the in vivo effects of the single compound. In fact, polyphenols have a poor absorption and biodistribution, but also a fast metabolism and excretion in the human body. The poor bioavailability of a polyphenol will affect the effective dose delivered to cancer cells. One way to counteract this drawback could be combination treatment with different polyphenols or with polyphenols and other anti-cancer drugs, which can lead to more effective antitumor effects than treatment using only one of the compounds. This report reviews current knowledge on the anticancer effects of combinations of polyphenols or polyphenols and anticancer drugs, with a focus on their ability to modulate multiple signaling transduction pathways involved in cancer.

Resveratrol analogue (E)-8-acetoxy-2-[2-(3,4-diacetoxyphenyl)ethenyl]-quinazoline induces G₂/M cell cycle arrest through the activation of ATM/ATR in human cervical carcinoma HeLa cells

Styrylquinazolines are synthetic analogues of resveratrol and have been suggested to cause anti-inflammatory activity by modulating prostaglandin E₂ (PGE₂) production. In the present study, we evaluated cytotoxic effects of various styrylquinazoline derivatives and found that (E)-8-acetoxy-2-[2-(3,4-diacetoxyphenyl)ethenyl]-quinazoline (8-ADEQ) most potently inhibited the proliferation of the human cervical carcinoma HeLa cells. Exploring the growth-inhibitory mechanisms of 8-ADEQ, we found that it causes a cell cycle arrest at the G₂/M phase by DNA flow cytometric analysis, which was accompanied by upregulation of cyclin B1 expression and cyclin-dependent protein kinase 1 (Cdk1) phosphorylation. In addition, we observed that 8-ADEQ causes phosphorylation of the cell division cycle 25C (Cdc25C) protein through the activation of checkpoint kinases 1 (Chk1) and Chk2, which in turn were activated via ataxia telangiectasia mutated (ATM)/ataxia telangiectasia-Rad3-related (ATR) kinases in response to the DNA damage. Furthermore, ATM/ATR inhibitor caffeine, p53- or ATM/ATR-specific siRNA significantly attenuated 8-ADEQ-induced G₂/M arrest. These results suggest that the 8-ADEQ inhibits the proliferation of human cervical cancer HeLa cells by DNA damage-mediated G₂/M cell cycle arrest. 8-ADEQ‑induced G₂/M arrest is mediated by the activation of both Chk1/2-Cdc25 and p53-p21CIP1/WAF1 via ATM/ATR pathway, and indicates that 8-ADEQ appears to have potential in the treatment of cervical cancer.

Effect of resveratrol on restoring spermatogenesis in experimental cryptorchid mice and analysis of related differentially expressed proteins

The present study aimed to evaluate the effect of trans-Resveratrol on spermatogenesis. Male Kunming suckling mice (10 days old) were surgically rendered cryptorchid and subcutaneously injected with trans-Resveratrol at doses of 5, 10, 20, and 40 µg/g/day as groups I, II, III, and IV, respectively, for 35 days. Animals in the control group received 10 µL/mouse/day of olive oil. Serum estradiol, testosterone, FSH, and LH levels were measured on day 45. Tissue analysis and sperm morphological abnormalities analysis were done. Results showed that in the control group and group I only spermatogonia and primary spermatocytes were present, whereas spermatogenesis was totally restored in groups II, III, and IV. Sperm counts in groups III and IV were remarkably higher than the control group (P<0.05). The morphological abnormalities in resveratrol-treated groups were higher than the mature mice. Serum estradiol levels in the resveratrol-treated groups were not significantly different from the control group, but were lower than the mature mice (P<0.05). There was no significant difference in serum testosterone levels between the resveratrol-treated groups and mature mice, but the levels in the resveratrol-treated groups was significantly lower than the control group (P<0.05). No significant influence of trans-Resveratrol was observed on serum FSH levels in all cryptorchid mice. Serum LH levels in groups I, II, and III were higher than the control group. These results indicate that trans-Resveratrol restores spermatogenesis in cryptorchid mice. In addition, proteomic analysis between the 20 μg/g/day resveratrol-treated group and the control group was carried out, and five kinds of proteins (BAF250, ZFP261, CHD1L, RBBP9, and SOHLH2) were identified. The expression of SOHLH2 increased, while that of BAF250, ZFP261, CHD1L, and RBBP9 decreased in the 20 µg/g/day resveratrol-treated group, indicating that SOHLH2 may contribute to testicular germ cell differentiation.

Resveratrol Represses Pokemon Expression in Human Glioma Cells

POK erythroid myeloid ontogenic factor (Pokemon), an important proto-oncoprotein, is a transcriptional repressor that regulates the expression of many genes and plays an important role in tumorigenesis. Resveratrol (RSV), a natural polyphenolic compound, has many beneficial biological effects on health. In this study, we investigated the role of Pokemon in RSV-induced biological effects and the effect of RSV on the expression of Pokemon in glioma cells. We found that overexpression of Pokemon decreased RSV-induced cell apoptosis, senescence, and anti-proliferative effects. Moreover, we showed that RSV could efficiently decrease the activity of the Pokemon promoter and the expression of Pokemon. Meanwhile, RSV also inhibited Sp1 DNA binding activity to the Pokemon promoter; whereas, it did not influence the expression and nuclear translocation of Sp1. In addition, we found that RSV could increase the recruitment of HDAC1, but decreased p300 to the Pokemon promoter. Taken together, all these results extended our understanding on the anti-cancer mechanism of RSV in glioma cells.

Broad targeting of angiogenesis for cancer prevention and therapy

Deregulation of angiogenesis – the growth of new blood vessels from an existing vasculature – is a main driving force in many severe human diseases including cancer. As such, tumor angiogenesis is important for delivering oxygen and nutrients to growing tumors, and therefore considered an essential pathologic feature of cancer, while also playing a key role in enabling other aspects of tumor pathology such as metabolic deregulation and tumor dissemination/metastasis. Recently, inhibition of tumor angiogenesis has become a clinical anti-cancer strategy in line with chemotherapy, radiotherapy and surgery, which underscore the critical importance of the angiogenic switch during early tumor development. Unfortunately the clinically approved anti-angiogenic drugs in use today are only effective in a subset of the patients, and many who initially respond develop resistance over time. Also, some of the anti-angiogenic drugs are toxic and it would be of great importance to identify alternative compounds, which could overcome these drawbacks and limitations of the currently available therapy. Finding “the most important target” may, however, prove a very challenging approach as the tumor environment is highly diverse, consisting of many different cell types, all of which may contribute to tumor angiogenesis. Furthermore, the tumor cells themselves are genetically unstable, leading to a progressive increase in the number of different angiogenic factors produced as the cancer progresses to advanced stages. As an alternative approach to targeted therapy, options to broadly interfere with angiogenic signals by a mixture of non-toxic natural compound with pleiotropic actions were viewed by this team as an opportunity to develop a complementary anti-angiogenesis treatment option. As a part of the “Halifax Project” within the “Getting to know cancer” framework, we have here, based on a thorough review of the literature, identified 10 important aspects of tumor angiogenesis and the pathological tumor vasculature which would be well suited as targets for anti-angiogenic therapy: (1) endothelial cell migration/tip cell formation, (2) structural abnormalities of tumor vessels, (3) hypoxia, (4) lymphangiogenesis, (5) elevated interstitial fluid pressure, (6) poor perfusion, (7) disrupted circadian rhythms, (8) tumor promoting inflammation, (9) tumor promoting fibroblasts and (10) tumor cell metabolism/acidosis. Following this analysis, we scrutinized the available literature on broadly acting anti-angiogenic natural products, with a focus on finding qualitative information on phytochemicals which could inhibit these targets and came up with 10 prototypical phytochemical compounds: (1) oleanolic acid, (2) tripterine, (3) silibinin, (4) curcumin, (5) epigallocatechin-gallate, (6) kaempferol, (7) melatonin, (8) enterolactone, (9) withaferin A and (10) resveratrol. We suggest that these plant-derived compounds could be combined to constitute a broader acting and more effective inhibitory cocktail at doses that would not be likely to cause excessive toxicity. All the targets and phytochemical approaches were further cross-validated against their effects on other essential tumorigenic pathways (based on the “hallmarks” of cancer) in order to discover possible synergies or potentially harmful interactions, and were found to generally also have positive involvement in/effects on these other aspects of tumor biology. The aim is that this discussion could lead to the selection of combinations of such anti-angiogenic compounds which could be used in potent anti-tumor cocktails, for enhanced therapeutic efficacy, reduced toxicity and circumvention of single-agent anti-angiogenic resistance, as well as for possible use in primary or secondary cancer prevention strategies.

Resveratrol down-regulates a glutamate-induced tissue plasminogen activator via Erk and AMPK/mTOR pathways in rat primary cortical neurons

Resveratrol (3,5,4'-trihydroxy-trans-stilbene, RSV) is a polyphenolic compound present in a variety of plant species (including grapes) that produces a myriad of biological activities including anti-inflammatory, antioxidant and neuroprotective effects. In this study, we investigate the effects of resveratrol on the basal and glutamate-stimulated expression and activity of a tissue plasminogen activator (tPA) that plays neuromodulatory or neurotoxic roles in many different neurological situations. Under basal conditions, resveratrol decreased the tPA expression and activity without affecting the tPA mRNA level in rat primary cortical neurons. RSV induced AMPK phosphorylation and inhibited mTOR phosphorylation. Inhibition of AMPK phosphorylation using compound C prevented resveratrol-induced down-regulation of tPA activity. This suggested that AMPK/mTOR-dependent translational inhibition contributes to the down-regulation of the tPA. Under glutamate-stimulated conditions of rat primary cortical neurons, tPA activity and expression were increased along with increased tPA mRNA expression but afterward treatment of RSV inhibited the glutamate-induced increase in tPA activity and expression and tPA mRNA expression. Glutamate stimulation induced activation of Akt and MAPK pathways as well as mTOR which were inhibited by RSV. Interestingly, the Erk pathway inhibitor U0126, but neither PI3K-Akt inhibitor LY294002 nor p38 inhibitor SB203580, mimicked the inhibitory action of RSV on glutamate-induced tPA up-regulation. This suggested the essential role of Erk in the transcriptional up-regulation of tPA expression, which is targeted by RSV. Glutamate stimulation induced neuronal cell death as determined by PI staining and MTT assay. However, RSV protected the cultured rat primary cortical neurons from glutamate-induced cell death as paralleled with the changes in tPA expression. These results suggested that RSV can modulate tPA activity under basal and stimulated conditions by both translational and transcriptional mechanisms. The regulation of the tPA by RSV provides additional therapeutic targets on top of the growing number of molecular substrates of RSV's action in the brain.

Anticancer mechanisms of resveratrol in liver cancer

Primary liver cancer is one of the most common malignant tumors. Because primary liver cancer has a high degree of malignancy and the early diagnosis is very difficult, it has a very poor prognosis and is associated with high mortality. Resveratrol is found in a variety of natural plants. Recent studies found that resveratrol has significant effects against liver cancer cells in vivo without obvious side effect, so it may become one of the most promising anticancer agents. This article will review the advances in understanding the anticancer mechanisms of resveratrol in liver cancer.

Resveratrol stimulates AP-1-regulated gene transcription

SCOPE

Many intracellular functions have been attributed to resveratrol, a polyphenolic phytoalexin found in grapes and in other plants, including the regulation of transcription. Here, we have analyzed the impact of resveratrol on the activity of the transcription factor activator protein-1 (AP-1).

METHODS AND RESULTS

Using a chromosomally embedded AP-1-responsive reporter gene, we show that the AP-1 activity was significantly elevated in resveratrol-treated 293 human embryonic kidney and HepG2 hepatoma cells. The 12-O-tetradecanoylphorbol-13-acetate-responsive element, a binding site for c-Jun and c-Fos, was identified as resveratrol-responsive element. Expression of c-Jun and c-Fos, two proteins that constitute AP-1, is upregulated in resveratrol-stimulated HEK293 cells. On the transcriptional level, c-Jun and the ternary complex factor Elk-1 are essential for the activation of AP-1 in resveratrol-treated cells. In addition, mitogen-activated protein kinases and protein kinase C are required to connect resveratrol stimulation with enhanced AP-1 controlled transcription. Finally, we show that resveratrol increased the activities of the AP-1 responsive cyclin D1 and tumor necrosis factor α promoters.

CONCLUSION

Resveratrol regulates gene transcription via activation of stimulus-regulated protein kinases and the stimulus-responsive AP-1 transcription factors. The fact that resveratrol regulates AP-1 activity may explain many of the pleiotropic intracellular alterations induced by resveratrol.

New Enlightenment of Skin Cancer Chemoprevention through Phytochemicals: In Vitro and In Vivo Studies and the Underlying Mechanisms

Skin cancer is still a major cause of morbidity and mortality worldwide. Skin overexposure to ultraviolet irradiations, chemicals, and several viruses has a capability to cause severe skin-related disorders including immunosuppression and skin cancer. These factors act in sequence at various steps of skin carcinogenesis via initiation, promotion, and/or progression. These days cancer chemoprevention is recognized as the most hopeful and novel approach to prevent, inhibit, or reverse the processes of carcinogenesis by intervention with natural products. Phytochemicals have antioxidant, antimutagenic, anticarcinogenic, and carcinogen detoxification capabilities thereby considered as efficient chemopreventive agents. Considerable efforts have been done to identify the phytochemicals which may possibly act on one or several molecular targets that modulate cellular processes such as inflammation, immunity, cell cycle progression, and apoptosis. Till date several phytochemicals in the light of chemoprevention have been studied by using suitable skin carcinogenic in vitro and in vivo models and proven as beneficial for prevention of skin cancer. This revision presents a comprehensive knowledge and the main molecular mechanisms of actions of various phytochemicals in the chemoprevention of skin cancer.

Effects of resveratrol on vascular endothelial growth factor expression in osteosarcoma cells and cell proliferation

The aim of the current study was to investigate the effects of resveratrol (Res) on vascular endothelial growth factor (VEGF) expression and cell proliferation in the human osteosarcoma cell line U20S. U20S cells were treated with Res at various concentrations (0, 10, 20 and 40 μmol/l) for various times (24, 48 and 72 h). The inhibitory effect of Res on U20S proliferation was observed using methyl thiazolyl tetrazolium (MTT) colorimetry. VEGF expression was determined using real-time polymerase chain reaction (RT-PCR) and western blot analysis. The inhibitory effect of Res on U20S proliferation increased as the concentration of Res increased. The inhibitory effect also increased with time. Res had an inhibitory effect on VEGF expression and significantly inhibited U20S cell proliferation. Res may exert an anti-osteosarcoma effect by inhibiting VEGF expression in tumor cells.

Resveratrol induces apoptosis associated with mitochondrial dysfunction in bladder carcinoma cells

OBJECTIVE

Resveratrol shows chemopreventive activity in a variety of human cancers by targeting mitochondria and triggering apoptosis. The purpose of this study was to investigate the antitumor action of resveratrol in bladder cancer and its underlying mechanism.

METHODS

Using two different bladder cell lines, BTT739 and T24, the cytotoxicity of resveratrol were determined by MTT assay. The apoptosis induced by resveratrol was assayed by transferase dUTP nick end labeling staining. To show whether the mitochondrial dysfunction involved in the effects of resveratrol, mitochondrial function was detected by mitochondrial membrane potential, reactive oxygen species production and adenosine 5'-triphosphate content. In addition, the markers of apoptosis in the intrinsic mitochondrial-dependent pathway were analyzed by the release of cytochrome c and the activities of caspase-9 and caspase-3.

RESULTS

Resveratrol effectively decreased cell viability and induced apoptosis in a concentration- and time-dependent manner. In addition, resveratrol significantly disrupted the mitochondrial membrane potential in both intact cells and isolated mitochondria. Resveratrol also increased reactive oxygen species production and reduced adenosine 5'-triphosphate concentrations. Western blot analysis showed that resveratrol provoked the release of cytochrome c from mitochondria to the cytosol. Furthermore, resveratrol significantly promoted the activation of caspase-9 and caspase-3.

CONCLUSIONS

These findings suggest that resveratrol efficiently triggers apoptosis in bladder cancer cells through the intrinsic mitochondrial-dependent pathway, which is associated with mitochondrial dysfunction. Resveratrol might have great pharmacological promise in the treatment of bladder cancer.

A metabolic perturbation by U0126 identifies a role for glutamine in resveratrol-induced cell death

Recent evidence has identified substantial overlap between metabolic and oncogenic biochemical pathways, suggesting novel approaches to cancer intervention. For example, cholesterol lowering statins and the antidiabetes medication metformin both act as chemopreventive agents in prostate and other cancers. The natural compound resveratrol has similar properties: increasing insulin sensitivity, suppressing adipogenesis, and inducing apoptotic death of cancer cells in vitro. However, in vivo tumor xenografts acquire resistance to resveratrol by an unknown mechanism, while mouse models of metabolic disorders respond more consistently to the compound. Here we demonstrate that castration-resistant human prostate cancer C4-2 cells are more sensitive to resveratrol-induced apoptosis than isogenic androgen-dependent LNCaP cells. The MEK inhibitor U0126 antagonized resveratrol-induced apoptosis in C4-2 cells, but this effect was not seen with other MEK inhibitors. U0126 was found to inhibit mitochondrial function and shift cells to aerobic glycolysis independently of MEK. Mitochondrial activity of U0126 arose through decomposition, producing both mitochondrial fluorescence and cyanide, a known inhibitor of complex IV. Applying U0126 mitochondrial inhibition to C4-2 cell apoptosis, we tested the possibility that glutamine supplementation of citric acid cycle intermediate α-ketoglutarate may be involved. Suppression of the conversion of glutamate to α-ketoglutarate antagonized resveratrol-induced death in C4-2 cells. A similar effect was also seen by reducing extracellular glutamine concentration in the culture medium, suggesting that resveratrol-induced death is dependent on glutamine metabolism, a process frequently dysregulated in cancer. Further work on resveratrol and metabolism in cancer is warranted to ascertain if the glutamine dependence has clinical implications.

Resveratrol suppresses human colon cancer cell proliferation and induces apoptosis via targeting the pentose phosphate and the talin-FAK signaling pathways-A proteomic approach

Background

We and others have previously reported that resveratrol (RSV) suppresses colon cancer cell proliferation and elevates apoptosis in vitro and/or in vivo, however molecular mechanisms are not fully elucidated. Particularly, little information is available on RSV's effects on metabolic pathways and the cell-extra cellular matrix (ECM) communication that are critical for cancer cell growth. To identify important targets of RSV, we analyzed whole protein fractions from HT-29 advanced human colon cancer cell line treated with solvent control, IGF-1 (10 nM) and RSV (150 μM) using LC/MS/MS-Mud PIT (Multidimensional Protein Identification Technology).

Results

Pentose phosphate pathway (PPP), a vital metabolic pathway for cell cycle progression, was elevated and suppressed by IGF-1 and RSV, respectively in the HT-29 cell line. Enzymatic assays confirmed RSV suppression of glucose-6 phosphate dehydrogenase (rate limiting) and transketolase, key enzymes of the PPP. RSV (150 μM) suppressed, whereas IGF-1 (10 nM) elevated focal adhesion complex (FAC) proteins, talin and pFAK, critical for the cell-ECM communication. Western blotting analyses confirmed the suppression or elevation of these proteins in HT-29 cancer cells treated with RSV or IGF-1, respectively.

Conclusions

Proteomic analysis enabled us to establish PPP and the talin-pFAK as targets of RSV which suppress cancer cell proliferation and induce apoptosis in the colon cancer cell line HT-29. RSV (150 μM) suppressed these pathways in the presence and absence of IGF-1, suggesting its role as a chemo-preventive agent even in obese condition.

Cancer cell survival following DNA damage-mediated premature senescence is regulated by mammalian target of rapamycin (mTOR)-dependent Inhibition of sirtuin 1

DNA-damaging agents can induce premature senescence in cancer cells, which contributes to the static effects of cancer. However, senescent cancer cells may re-enter the cell cycle and lead to tumor relapse. Understanding the mechanisms that control the viability of senescent cells may be helpful in eliminating these cells before they can regrow. Treating human squamous cell carcinoma (SCC) cells with the anti-cancer compounds, resveratrol and doxorubicin, triggered p53-independent premature senescence by invoking oxidative stress-mediated DNA damage. This process involved the mTOR-dependent phosphorylation of SIRT1 at serine 47, resulting in the inhibition of the deacetylase activity of SIRT1. SIRT1 phosphorylation caused concomitant increases in p65/RelA NF-κB acetylation and the expression of an anti-apoptotic Bfl-1/A1. SIRT1 physically interacts with the mTOR-Raptor complex, and a single amino acid substitution in the TOS (TOR signaling) motif in the SIRT1 prevented Ser-47 phosphorylation and Bfl-1/A1 induction. The pharmacologic and genetic inhibition of mTOR, unphosphorylatable S47A, or F474A TOS mutants restored SIRT1 deacetylase activity, blocked Bfl-1/A1 induction, and sensitized prematurely senescent SCC cells for apoptosis. We further show that the treatment of UVB-induced SCCs with doxorubicin transiently stabilized tumor growth but was followed by tumor regrowth upon drug removal in p53(+/-)/SKH-1 mice. The subsequent treatment of stabilized SCCs with rapamycin decreased tumor size and induced caspase-3 activation. These results demonstrate that the inhibition of SIRT1 by mTOR fosters survival of DNA damage-induced prematurely senescent SCC cells via Bfl-1/A1 in the absence of functional p53.

The grape antioxidant resveratrol for skin disorders: promise, prospects, and challenges

Resveratrol, a phytoalexin antioxidant found in red grapes, has been shown to have both chemopreventive and therapeutic effects against many diseases and disorders, including those of the skin. Studies have shown protective effects of resveratrol against ultraviolet radiation-mediated oxidative stress and cutaneous damages including skin cancer. Because many of the skin conditions stem from ultraviolet radiation and oxidative stress, this antioxidant appears to have promise and prospects against a wide range of cutaneous disorders including skin aging and skin cancers. However, there are a few roadblocks in the way of this promising agent regarding its translation from the bench to the bedside. This review discusses the promise and prospects of resveratrol in the management of skin disorders and the associated challenges.

Resveratrol targets transforming growth factor-β2 signaling to block UV-induced tumor progression

Resveratrol (RES) is a potent anti-cancer agent. We have previously reported that RES arrests the growth of invasive human A431 squamous cell carcinoma (SCC) cells. In this study, we show that oral administration of RES to highly tumor-susceptible p53(+/-)/SKH-1 mice markedly delayed UV-induced skin tumorigenesis and reduced the malignant conversion of benign papillomas to SCCs. Transforming growth factor-β2 (TGF-β2) was predominantly overexpressed in UV-induced SCCs and its expression was diminished in RES-treated SCCs/skin. In addition to the inhibition of TGF-β2 expression, RES increased the level of epithelial cadherin. This RES-mediated TGF-β2 downregulation led to the inhibition of both TGF-β2/Smad-dependent and -independent pathways, and suppressed the invasiveness of A431 cells. Addition of TGF-β2, but not TGF-β1, rescued the RES-mediated downregulation of p-extracellular signal-regulated kinases 1/2, p-Smad3, and α-smooth muscle actin. The protein kinase B (Akt) substrate cAMP response-binding protein (pCREB) transcription factor is known to regulate TGF-β2 expression, and RES treatment decreased phosphorylation of Akt and pCREB. Expression of constitutively active Akt blocked RES inhibition of CREB and TGF-β2, and rescued RES inhibition of cellular invasiveness. Our data indicate that RES suppresses UV-induced malignant tumor progression in p53(+/-)/SKH-1 mice and that RES-inhibited invasiveness of human A431 SCC cells appears to occur, in part, through the Akt-mediated downregulation of TGF-β2.

3,5,3',4',5'-pentamethoxystilbene (MR-5), a synthetically methoxylated analogue of resveratrol, inhibits growth and induces G1 cell cycle arrest of human breast carcinoma MCF-7 cells

3,5,3',4',5'-pentamethoxystilbene (MR-5) is a synthetically methoxylated analogue of resveratrol and has been suggested to have antitumor activity because of structural similarity to resveratrol. Herein, we investigate the antiproliferative effect of MR-5 in human breast cancer MCF-7 cells and demonstrate that MR-5 had a more potent inhibition on cell growth compared with resveratrol and other methoxylated derivatives. Exploring the growth-inhibitory mechanisms of MR-5, we found that it is accompanied by G1 cell cycle arrest, which coincides with a marked inhibition of G1 cell cycle regulatory proteins, including decreased cyclins (D1/D3/E) and cyclin-dependent kinases (CDK2/4/6) and increased CDK inhibitors (CKIs) such as p15, p16, p21, and p27. Furthermore, the increase in CKI levels by MR-5 resulted in a concomitant increase in their interactions of CDK4 and CDK2, along with a strong inhibition in CDK4 kinase activity and the accumulation of hypophosphorylated Rb. MR-5 also modulated some critical kinase activities related to cell cycle regulation, including Akt, mitogen-activated protein kinase (ERK1/2), p38 mitogen-activated protein kinase (p38 MAPK), and focal adhesion kinase (FAK) in MCF-7 cells. In total, our results demonstrate that MR-5 affects multiple cellular targets that contribute to its antiproliferative activity in MCF-7 cells and provide novel information for synthetic chemists to design new antitumor agents with introduction of methoxylated group(s) in the basic compound.

Multiple molecular targets of resveratrol: Anti-carcinogenic mechanisms

Plant-derived polyphenolic compounds, such as the stilbene resveratrol (trans-3,4',5-trihydroxystilbene), have been identified as potent anti-cancer agents. Extensive in vitro studies revealed multiple intracellular targets of resveratrol, which affect cell growth, inflammation, apoptosis, angiogenesis, and invasion and metastasis. These include tumor suppressors p53 and Rb; cell cycle regulators, cyclins, CDKs, p21WAF1, p27KIP and INK and the checkpoint kinases ATM/ATR; transcription factors NF-kappaB, AP-1, c-Jun, and c-Fos; angiogenic and metastatic factors, VEGF and matrix metalloprotease 2/9; cyclooxygenases for inflammation; and apoptotic and survival regulators, Bax, Bak, PUMA, Noxa, TRAIL, APAF, survivin, Akt, Bcl2 and Bcl-X(L). In addition to its well-documented anti-oxidant properties, there is increasing evidence that resveratrol exhibits pro-oxidant activity under certain experimental conditions, causing oxidative DNA damage that may lead to cell cycle arrest or apoptosis. This review summarizes in vitro mechanistic data available for resveratrol and discusses new potential anti-cancer targets and the antiproliferative mechanisms of resveratrol.

Inhibition of 12-LOX and COX-2 reduces the proliferation of human epidermoid carcinoma cells (A431) by modulating the ERK and PI3K-Akt signalling pathways

Eicosanoids, the oxygenated metabolites of arachidonic acid (AA), mediate a variety of human diseases, such as cancer, inflammation and arthritis. To evaluate the role of eicosanoids in epidermoid carcinoma, the expression of AA metabolizing enzymes, such as lipoxygenases (LOXs) and cyclooxygenases (COXs), was analysed in a human epidermoid carcinoma cell line (A431). These studies revealed overexpression of 12-R-LOX and COX-2 in A431 cells. Baicalein (a 12-LOX inhibitor) and celecoxib (a COX-2 inhibitor) significantly reduced thymidine incorporation, whereas 12-(R)-HETE and 12-(S)-HETE (12-LOX metabolites) and PGE(2) (COX-2 metabolite) significantly enhanced thymidine incorporation, suggesting a role for these enzymes in the regulation of A431 cell proliferation. Further studies on the mechanism of cell death by baicalein and celecoxib revealed that the induction of apoptosis in A431 cells was associated with reduction in the Bcl-2/Bax ratio, release of cytochrome c, activation of caspase-3 and PARP cleavage. The apoptosis induced by baicalein and celecoxib was mediated by down regulation of ERK and PI3K-Akt pathways. Further, 12-(R)-HETE, 12-(S)-HETE and PGE(2) upregulated the p-ERK and p-Akt levels, suggesting the involvement of ERK and Akt pathways in the 12-LOX- and COX-2-mediated regulation of growth in A431 cells. Our findings suggest that 12-R-LOX and COX-2 play a critical role in the regulation of growth in epidermoid carcinoma and that their inhibitors may be of potential therapeutic importance.

Resveratrol addiction: to die or not to die

Resveratrol, a polyphenol derived from red grapes, berries, and peanuts, has been shown to mediate death of a wide variety of cells. The mechanisms by which resveratrol mediates cell death include necrosis, apoptosis, autophagy, and others. While most studies suggest that resveratrol kills tumor cells selectively, evidence is emerging that certain normal cells such as endothelial cells, lymphocytes, and chondrocytes are vulnerable to resveratrol. Cell killing by this stilbene may be mediated through any of numerous mechanisms that involve activation of mitochondria and of death caspases; upregulation of cyclin-dependent kinase inhibitors, tumor suppressor gene products, or death-inducing cytokines and cytokine receptors; or downregulation of cell survival proteins (survivin, cFLIP, cIAPs, X-linked inhibitor of apoptosis protein (XIAP), bcl-2, bcl-XL) or inhibition of cell survival kinases (e.g., mitogen-activiated protein kinases (MAPKs), AKT/phosphoinositide 3-kinase (PI3K), PKC, EGFR kinase) and survival transcription factors (nuclear factor-kappaB (NF-kappaB), activating protein 1 (AP-1), HIF-1alpha, signal transducer and activator of transcription (STAT3)). Induction of any of these pathways by resveratrol leads to cell death. While cell death is a hallmark of resveratrol, this polyphenol also has been linked with suppression of inflammation, arthritis, and cardiovascular diseases and delaying of aging. These attributes of resveratrol are discussed in detail in this review.

trans-Resveratrol inhibits H2O2-induced adenocarcinoma gastric cells proliferation via inactivation of MEK1/2-ERK1/2-c-Jun signalling axis

In this report we investigate the signalling pathway activated by H(2)O(2) in human adenocarcinoma gastric cells (AGS) and we evaluate the anti-proliferative action of the natural stilbene trans-resveratrol. We demonstrate that H(2)O(2) accelerates cell growth and induces a prompt MEK1/2-ERK1/2 activation. Such events are also associated with the activation of c-Jun and its translocation into the nuclear compartment. A specific inhibitor of ERK1/2 phosphorylation by MEK1/2 (U0126) abrogates these phenomena. On the contrary, specific inhibition of JNK activity does not influence H(2)O(2)-mediated growth, suggesting that cell proliferation likely proceeds via MEK1/2-ERK1/2-Jun signalling axis. trans-Resveratrol is also able to completely suppress the increase in proliferation. We demonstrate that this property is not due to its antioxidant capacity but rather due to a specific inhibition of ERK1/2 phosphorylation by MEK1/2 and repression of c-Jun activation.

Resveratrol inhibits PDGF receptor mitogenic signaling in mesangial cells: role of PTP1B

Mesangioproliferative glomerulonephritis is associated with overactive PDGF receptor signal transduction. We show that the phytoalexin resveratrol dose dependently inhibits PDGF-induced DNA synthesis in mesangial cells with an IC(50) of 10 microM without inducing apoptosis. Remarkably, the increased SIRT1 deacetylase activity induced by resveratrol was not necessary for this inhibitory effect. Resveratrol significantly blocked PDGF-stimulated c-Src and Akt kinase activation, resulting in reduced cyclin D1 expression and attenuated pRb phosphorylation and cyclin-dependent kinase-2 (CDK2) activity. Furthermore, resveratrol inhibited PDGFR phosphorylation at the PI 3 kinase and Grb-2 binding sites tyrosine-751 and tyrosine-716, respectively. This deficiency in PDGFR phosphorylation resulted in significant inhibition of PI 3 kinase and Erk1/2 MAPK activity. Interestingly, resveratrol increased the activity of protein tyrosine phosphatase PTP1B, which dephosphorylates PDGF-stimulated phosphorylation at tyrosine-751 and tyrosine-716 on PDGFR with concomitant reduction in Akt and Erk1/2 kinase activity. PTP1B significantly inhibited PDGF-induced DNA synthesis without inducing apoptosis. These results for the first time provide evidence that the stilbene resveratrol targets PTP1B to inhibit PDGFR mitogenic signaling.