Analysis of resveratrol as a lung cancer chemopreventive agent in A/J mice exposed to benzo[a]pyrene

Chemo-Preventive Action of Resveratrol: Suppression of p53-A Molecular Targeting Approach

Extensive experimental, clinical, and epidemiological evidence has explained and proven that products of natural origin are significantly important in preventing and/or ameliorating various disorders, including different types of cancer that researchers are extremely focused on. Among these studies on natural active substances, one can distinguish the emphasis on resveratrol and its properties, especially the potential anticancer role. Resveratrol is a natural product proven for its therapeutic activity, with remarkable anti-inflammatory properties. Various other benefits/actions have also been reported, such as cardioprotective, anti-ageing, antioxidant, etc. and its rapid digestion/absorption as well. This review aims to collect and present the latest published studies on resveratrol and its impact on cancer prevention, molecular signals (especially p53 protein participation), and its therapeutic prospects. The most recent information regarding the healing action of resveratrol is presented and concentrated to create an updated database focused on this topic presented above.

Natural substances in cancer—do they work?

Owing to anticancer properties of selected natural substances, it is assumed that they have potential to be used in oncological therapy. Here, the recently proven effects of the selected natural polyphenols, resveratrol and curcumin, are described. Secondly, the potential of probiotics and prebiotics in modulation of immunological response and/or enhancing the chemotherapeutic treatments is reported based on the recent clinical trials. Further, the chapter presents current knowledge regarding the targeted supplementation of the patient with probiotic bacteria and known efficacy of probiotics to support immunotherapy. The major clinical trials are listed, aiming to verify whether, and to which extent the manipulation of patient’s microbiome can improve the outcome of chemotherapies. In the end, a potential of natural substances and feed ingredients to pose epigenetic changes is highlighted. The chapter provides an insight into the scientific proofs about natural bioactive substances in relation to cancer treatment, leaded by the question – do they really work?

Delivery of Natural Agents by Means of Mesoporous Silica Nanospheres as a Promising Anticancer Strategy

Natural prodrugs derived from different natural origins (e.g., medicinal plants, microbes, animals) have a long history in traditional medicine. They exhibit a broad range of pharmacological activities, including anticancer effects in vitro and in vivo. They have potential as safe, cost-effective treatments with few side effects, but are lacking in solubility, bioavailability, specific targeting and have short half-lives. These are barriers to clinical application. Nanomedicine has the potential to offer solutions to circumvent these limitations and allow the use of natural pro-drugs in cancer therapy. Mesoporous silica nanoparticles (MSNs) of various morphology have attracted considerable attention in the search for targeted drug delivery systems. MSNs are characterized by chemical stability, easy synthesis and functionalization, large surface area, tunable pore sizes and volumes, good biocompatibility, controlled drug release under different conditions, and high drug-loading capacity, enabling multifunctional purposes. In vivo pre-clinical evaluations, a significant majority of results indicate the safety profile of MSNs if they are synthesized in an optimized way. Here, we present an overview of synthesis methods, possible surface functionalization, cellular uptake, biodistribution, toxicity, loading strategies, delivery designs with controlled release, and cancer targeting and discuss the future of anticancer nanotechnology-based natural prodrug delivery systems.

Genistein Affects Expression of Cytochrome P450 (CYP450) Genes in Hepatocellular Carcinoma (HEPG2/C3A) Cell Line

BACKGROUND

Genistein (5,7-Dihydroxy-3-(4-hydroxyphenyl)-4H-1-benzopyran-4-one) is the most abundant isoflavone in soybean, which has been associated with a lower risk of development of cancer and cardiovascular diseases. Of particular interest regarding cancer preventive properties of flavonoids is their interaction with cytochrome P450 enzymes (CYPs). However, contradictory data report the effect of genistein on expression of СYPs enzymes.

OBJECTIVE

The aim of this study was to investigate the effects of genistein on cytochrome P450 (CYP) gene expression levels in human hepatocellular carcinoma (HepG2/C3A) and colon adenocarcinoma (HT29) cells.

METHODS

Real-time RT-PCR was used to examine the expression of genes families involved in xenobiotic metabolism, such as CYP1 (CYP1A1, CYP1B1), CYP2 (CYP2E1, CYP2D6), CYP3 (CYP3A4); and of a family involved in the catabolism of the all-trans-retinoic acid (ATRA), CYP26 (CYP26A1, CYP26B1).

RESULTS

RT-qPCR data analysis showed that after 12 h of exposure of HepG2/C3A cells to genistein (5 and 50 µM) there was an upregulation of CYP1A1 and CYP1B1 and downregulation of CYP2D6, CYP26A1 and CYP26B1 mRNA levels. There was no change in the mRNA levels of CYP P450 genes in HT29 cells.

CONCLUSION

Our results suggest that treatment with genistein in non-toxic concentrations may impact the expression level of CYPs involved in the biotransformation of xenobiotics and drug metabolizing enzymes. Moreover, the downregulation of ATRA metabolism-related genes opens a new research path for the study of genistein as retinoic acid metabolism blocking agent for treating cancer and other pathologies.

Intranasal administration of resveratrol successfully prevents lung cancer in A/J mice

Lung cancer is the most lethal cancer in the world. About 80% of lung cancer deaths are linked to tobacco use. As a complement to tobacco control, efficient chemoprevention strategies are needed to tackle lung cancer epidemic. Resveratrol is one of the most studied natural products, notably for its cancer chemoprevention properties. However, its low oral bioavailability has often limited the translation of in vitro activities to in vivo effects. While oral administration of resveratrol effectively inhibited colorectal carcinogenesis, it failed to protect mice from chemically-induced lung carcinogenesis. Therefore, non-invasive parenteral routes must be considered to bring resveratrol to the lungs. In the present study, intranasal administration of a concentrated formulation proved to be a valid method to expose the lungs to a sufficient amount of resveratrol. This formulation was administered three times a week for 25 weeks to A/J mice having 4-[methyl(nitroso)amino]-1-(3-pyridinyl)-1-butanone-induced lung carcinogenesis. Resveratrol-treated mice showed a 27% decrease in tumour multiplicity, with smaller tumours, resulting in 45% decrease in tumour volume/mouse. In vitro investigations highlighted apoptosis as a potential mechanism of action. This study presents an effective way to overcome resveratrol low oral bioavailability, encouraging a reevaluation of its use in future clinical trials.

Alteration of benzo(a)pyrene biotransformation by resveratrol in ApcMin/+ mouse model of colon carcinogenesis

Epidemiological surveys have revealed that environmental and dietary factors contribute to most of the human cancers. Our earlier studies have shown that resveratrol (RVT), a phytochemical reduced the tumor number, size and incidence of dysplasias induced by benzo(a)pyrene (BaP), an environmental toxicant in the Apc^Min/+ mouse model of colon cancer. In this study we investigated to ascertain whether the preventive effects of RVT on BaP-induced colon carcinogenesis is a result of altered BaP biotransformation by RVT. For the first group of mice, 100 μg BaP/kg bw was administered in peanut oil via oral gavage over a 60 day period. For the second group, 45 μg RVT/kg bw was co-administered with BaP. For the third group, RVT was administered for 1 week prior to BaP exposure. Blood, colon and liver were collected from control and BaP/RVT-treated mice at 60 days post-BaP & RVT exposure. We have assayed activities and expression (protein & mRNA) of drug metabolizing enzymes such as cytochrome P4501A1 (CYP1A1), CYP1B1, and glutathione-S-transferase (GST) in colon and liver samples from the treatment groups mentioned above. An increased expression of CYP1A1 in liver and colon and of CYP1B1 in liver of BaP-treated mice was seen, while RVT inhibited the extent of biotransformation mediated by these enzymes in the respective tissue samples. In the case of GST, an increased expression in colon of BaP alone-treated mice was noted when RVT was administered prior to BaP or simultaneously with BaP. However, there is no change in liver GST expression between BaP and RVT treatment groups. The concentrations of BaP aqueous (phase II) metabolites were found to be greater than the organic (phase I) metabolites, suggesting that RVT slows down the phase I metabolism (metabolic activation) of BaP, while enhancing phase II metabolism (detoxification). Additionally, the BaP-DNA adduct concentrations measured in colon and liver of BaP + RVT-treated mice were low relative to their BaP counterparts. Taken together, our findings strongly suggest that RVT alleviates BaP-induced colon carcinogenesis by impairing biotransformation pathways and DNA adduct formation, and therefore holds promise as a chemopreventive agent.

Identification of karanjin isolated from the Indian beech tree as a potent CYP1 enzyme inhibitor with cellular efficacy via screening of a natural product repository

CYP1A1 is thought to mediate carcinogenesis in oral, lung and epithelial cancers. In order to identify a CYP1A1 inhibitor from an edible plant, 394 natural products in the IIIM's natural product repository were screened, at 10 μM concentration, using CYP1A1-Sacchrosomes™ (i.e. microsomal enzyme isolated from recombinant baker's yeast). Twenty-seven natural products were identified that inhibited 40-97% of CYP1A1's 7-ethoxyresorufin-O-deethylase activity. The IC50 values of the 'hits', belonging to different chemical scaffolds, were determined. Their selectivity was studied against a panel of 8 CYP-Sacchrosomes™. In order to assess cellular efficacy, the 'hits' were screened for their capability to inhibit CYP enzymes expressed within live recombinant human embryonic kidney (HEK293) cells from plasmids encoding specific CYP genes (1A2, 1B1, 2C9, 2C19, 2D6, 3A4). Isopimpinellin (IN-475; IC50, 20 nM) and karanjin (IN-195; IC50, 30 nM) showed the most potent inhibition of CYP1A1 in human cells. Isopimpinellin is found in celery, parsnip, fruits and in the rind and pulp of limes whereas different parts of the Indian beech tree, which contain karanjin, have been used in traditional medicine. Both isopimpinellin and karanjin negate the cellular toxicity of CYP1A1-mediated benzo[a]pyrene. Molecular docking and molecular dynamic simulations with CYP isoforms rationalize the observed trends in the potency and selectivity of isopimpinellin and karanjin.

The Role of Resveratrol in Cancer Therapy

Natural product compounds have recently attracted significant attention from the scientific community for their potent effects against inflammation-driven diseases, including cancer. A significant amount of research, including preclinical, clinical, and epidemiological studies, has indicated that dietary consumption of polyphenols, found at high levels in cereals, pulses, vegetables, and fruits, may prevent the evolution of an array of diseases, including cancer. Cancer development is a carefully orchestrated progression where normal cells acquires mutations in their genetic makeup, which cause the cells to continuously grow, colonize, and metastasize to other organs such as the liver, lungs, colon, and brain. Compounds that modulate these oncogenic processes can be considered as potential anti-cancer agents that may ultimately make it to clinical application. Resveratrol, a natural stilbene and a non-flavonoid polyphenol, is a phytoestrogen that possesses anti-oxidant, anti-inflammatory, cardioprotective, and anti-cancer properties. It has been reported that resveratrol can reverse multidrug resistance in cancer cells, and, when used in combination with clinically used drugs, it can sensitize cancer cells to standard chemotherapeutic agents. Several novel analogs of resveratrol have been developed with improved anti-cancer activity, bioavailability, and pharmacokinetic profile. The current focus of this review is resveratrol’s in vivo and in vitro effects in a variety of cancers, and intracellular molecular targets modulated by this polyphenol. This is also accompanied by a comprehensive update of the various clinical trials that have demonstrated it to be a promising therapeutic and chemopreventive agent.

Cancer Chemoprevention by Resveratrol: The p53 Tumor Suppressor Protein as a Promising Molecular Target

Increasing epidemiological and experimental evidence has demonstrated an inverse relationship between the consumption of plant foods and the incidence of chronic diseases, including cancer. Microcomponents that are naturally present in such foods, especially polyphenols, are responsible for the benefits to human health. Resveratrol is a diet-derived cancer chemopreventive agent with high therapeutic potential, as demonstrated by different authors. The aim of this review is to collect and present recent evidence from the literature regarding resveratrol and its effects on cancer prevention, molecular signaling (especially regarding the involvement of p53 protein), and therapeutic perspectives with an emphasis on clinical trial results to date.

In vitro and in vivo anti-inflammatory activities of mixed fruit and vegetable juice

In this study, we attempted to develop fruit-based functional juice with anti-inflammatory activity for consumers living under heavy air pollution. At first, four different formulations for functional juice prepared by combining 10 kinds of fruits and other ingredients in various ratios were tested for NAD(P)H: quinoneoxidoreductase 1 (NQO1)-inducing activity in mouse hepatoma Hepa1c1c7 cells. The formulation showing the highest NQO1-inducing activity [named detoxification juice (DJ)] was investigated for its anti-inflammatory activity in a co-culture system of human lung carcinoma A549 cell line and a differentiated human monocytic cell line THP-1. DJ significantly reduced the LPS-induced production of proinflammatory cytokines, such as interleukin-6 (IL-6), IL-1β, and tumor necrosis factor α (TNF-α). Furthermore, DJ administration suppressed the benzo[a]pyreneinduced elevation of plasma cytokine levels of C57BL/6 mice. However, the protective effect of DJ against inflammation in lung and trachea caused by air pollution needs to be assessed through clinical studies.

Curcumin Affects Phase II Disposition of Resveratrol Through Inhibiting Efflux Transporters MRP2 and BCRP

PURPOSE

To evaluate the impact of curcumin on the disposition of resveratrol phase II metabolites in vivo, and explain the observations by performing in vitro studies in transporter-overexpressed cells.

METHODS

Pharmacokinetic studies of resveratrol with and without the co-administration of curcumin were performed in both FVB wild-type and Bcrp1 (-/-) mice. Human UGT1A9-overexpressing HeLa cells and human MRP2-overexpressing MDCK II-UGT1A1 cells were used as in vitro tools to further determine the impact of curcumin as a transporter inhibitor on resveratrol metabolites.

RESULTS

We observed higher exposure of resveratrol conjugates in Bcrp1 (-/-) mice compared to wild-type mice. In wild-type mice, curcumin increased the AUC of resveratrol glucuronide by 4-fold compared to the mice treated without curcumin. The plasma levels of resveratrol and its sulfate conjugate also increased moderately. In Bcrp1 (-/-) mice, there was a further increase (6-fold increase) in AUC of resveratrol glucuronide observed when curcumin was co-administered compared to AUC values obtained in wild-type mice without curcumin treatment. In the presence of 50 nM curcumin, the clearance of resveratrol-3-O-glucuronide and resveratrol-3-O-sulfate reduced in both MRP2-overexpressing MDCKII-UGT1A1 cells and Human UGT1A9-overexpressing HeLa cells.

CONCLUSIONS

These results suggest that curcumin alters the phase II distribution of resveratrol through inhibiting efflux transporters including MRP2 and BCRP.

Induction of c-Jun by air particulate matter (PM₁₀) of Mexico city: Participation of polycyclic aromatic hydrocarbons

The carcinogenic potential of urban particulate matter (PM) has been partly attributed to polycyclic aromatic hydrocarbons (PAHs) content, which activates the aryl hydrocarbon receptor (AhR). Here we report the effect of PM with an aerodynamic size of 10 μm (PM10) on the induction of AhR pathway in A549 cells, evaluating its downstream targets CYP1B1, IL-6, IL-8 and c-Jun. Significant increases in CYP1B1 protein and enzyme activity; IL-6 and IL-8 secretion and c-Jun protein were found in response to PM10. The formation of PAH-DNA adducts was also detected. The involvement of AhR pathway was confirmed with Resveratrol as AhR antagonist, which reversed CYP1B1 and c-Jun induction. Nevertheless, in IL-6 and IL-8 secretion, the Resveratrol was ineffective, suggesting an effect independent of this pathway. Considering the role of c-Jun in oncogenesis, its induction by PM may be contributing to its carcinogenic potential through induction of AhR pathway by PAHs present in PM10.

Effect of phytochemical intervention on dibenzo[a,l]pyrene-induced DNA adduct formation

Dibenzo[a,l]pyrene (DBP) has been found to be the most potent carcinogen of the polycyclic aromatic hydrocarbons (PAHs). Primary sources for DBP in the environment are combustion of wood and coal burning, gasoline and diesel exhaust, and tires. Given the likelihood of environmental exposure to DBP and strong experimental evidence of its potency, it is likely to contribute to lung cancer development. Intervention with compounds of natural origin ("phytochemicals") is considered an effective means to prevent cancer development and favorably modulate the underlying mechanisms, including DNA adduct formation. In this study, several agents have been identified that inhibit environmental carcinogen-induced DNA adduct formation using a cell-free microsomal system. Of the ten agents tested, resveratrol (648 ± 26 adducts/10(9) nucleotides), oltipraz (1007 ± 348 adducts/10(9) nucleotides), delphinidin (1252 ± 142 adducts/10(9) nucleotides), tanshinone I (1981 ± 213 adducts/10(9) nucleotides), tanshinone IIA (2606 ± 478 adducts/10(9) nucleotides) and diindoylmethane (3643 ± 469 adducts/10(9) nucleotides) were the most effective compared to vehicle treatment (14,062 ± 1097 adducts/10(9) nucleotides). DBP is metabolized by phase I metabolizing enzymes CYP1A1, CYP1A2, and CYP1B1. DBP-induced DNA adducts can be inhibited by several mechanisms. We found that all the test agents inhibited DNA adducts by inhibiting one or more of these enzymes. Oltipraz inhibited DNA adducts entirely by inhibiting the CYP450s, while resveratrol and delphinidin inhibited DNA adducts by also interacting directly with the carcinogenic metabolite, anti-dibenzo(a,l)pyrene-11,12-dihydrodiol-13,14-epoxide.

The pharmacology of resveratrol in animals and humans

In addition to thousands of research papers related to resveratrol (RSV), approximately 300 review articles have been published. Earlier research tended to focus on pharmacological activities of RSV related to cardiovascular systems, inflammation, and carcinogenesis/cancer development. More recently, the horizon has been broadened by exploring the potential effect of RSV on the aging process, diabetes, neurological dysfunction, etc. Herein, we primarily focus on the in vivo pharmacological effects of RSV reported over the past 5 years (2009-2014). In addition, recent clinical intervention studies performed with resveratrol are summarized. Some discrepancies exist between in vivo studies with animals and clinical studies, or between clinical studies, which are likely due to disparate doses of RSV, experimental settings, and subject variation. Nevertheless, many positive indications have been reported with mammals, so it is reasonable to advocate for the conduct of more definitive clinical studies. Since the safety profile is pristine, an added advantage is the use of RSV as a dietary supplement. This article is part of a Special Issue entitled: Resveratrol: Challenges in translating pre-clinical findings to improved patient outcomes.

The role of reactive oxygen species and subsequent DNA-damage response in the emergence of resistance towards resveratrol in colon cancer models

In spite of the novel strategies to treat colon cancer, mortality rates associated with this disease remain consistently high. Tumour recurrence has been linked to the induction of resistance towards chemotherapy that involves cellular events that enable cancer cells to escape cell death. Treatment of colon cancer mainly implicates direct or indirect DNA-damaging agents and increased repair or tolerances towards subsequent lesions contribute to generate resistant populations. Resveratrol (RSV), a potent chemosensitising polyphenol, might share common properties with chemotherapeutic drugs through its indirect DNA-damaging effects reported in vitro. In this study, we investigated how RSV exerts its anticancer effects in models of colon cancer with a particular emphasis on the DNA-damage response (DDR; PIKKs-Chks-p53 signalling cascade) and its cellular consequences. We showed in vitro and in vivo that colon cancer models could progressively escape the repeated pharmacological treatments with RSV. We observed for the first time that this response was correlated with transient activation of the DDR, of apoptosis and senescence. In vitro, a single treatment with RSV induced a DDR correlated with S-phase delay and apoptosis, but prolonged treatments led to transient micronucleations and senescence phenotypes associated with polyploidisation. Ultimately, stable resistant populations towards RSV displaying higher degrees of ploidy and macronucleation as compared to parental cells emerged. We linked these transient effects and resistance emergence to the abilities of these cells to progressively escape RSV-induced DNA damage. Finally, we demonstrated that this DNA damage was triggered by an overproduction of reactive oxygen species (ROS) against which cancer cells could adapt under prolonged exposure to RSV. This study provides a pre-clinical analysis of the long-term effects of RSV and highlights ROS as main agents in RSV's indirect DNA-damaging properties and consequences in terms of anticancer response and potent resistance emergence.

Resveratrol and clinical trials: the crossroad from in vitro studies to human evidence

Resveratrol (3,5,4’-trihydroxy-trans-stilbene) is a non-flavonoid polyphenol that may be present in a limited number of food-stuffs such as grapes and red wine. Resveratrol has been reported to exert a plethora of health benefits through many different mechanisms of action. This versatility and presence in the human diet have drawn the worldwide attention of many research groups over the past twenty years, which has resulted in a huge output of in vitro and animal (preclinical) studies. In line with this expectation, many resveratrol-based nutraceuticals are consumed all over the world with questionable clinical/scientific support. In fact, the confirmation of these benefits in humans through randomized clinical trials is still very limited. The vast majority of preclinical studies have been performed using assay conditions with a questionable extrapolation to humans, i.e. too high concentrations with potential safety concerns (adverse effects and drug interactions), short-term exposures, in vitro tests carried out with non-physiological metabolites and/or concentrations, etc. Unfortunately, all these hypothesis-generating studies have contributed to increased the number of ‘potential’ benefits and mechanisms of resveratrol but confirmation in humans is very limited. Therefore, there are many issues that should be addressed to avoid an apparent endless loop in resveratrol research. The so-called ‘Resveratrol Paradox’, i.e., low bioavailability but high bioactivity, is a conundrum not yet solved in which the final responsible actor (if any) for the exerted effects has not yet been unequivocally identified. It is becoming evident that resveratrol exerts cardioprotective benefits through the improvement of inflammatory markers, atherogenic profile, glucose metabolism and endothelial function. However, safety concerns remain unsolved regarding chronic consumption of high RES doses, specially in medicated people. This review will focus on the currently available evidence regarding resveratrol’s effects on humans obtained from randomized clinical trials. In addition, we will provide a critical outlook for further research on this molecule that is evolving from a minor dietary compound to a possible multi-target therapeutic drug.

Comparison of intake and systemic relative effect potencies of dioxin-like compounds in female mice after a single oral dose

BACKGROUND

Risk assessment for mixtures of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and polychlorinated biphenyls (PCBs) is performed using the toxic equivalency factor (TEF) approach. These TEF values are derived mainly from relative effect potencies (REPs) linking an administered dose to an in vivo toxic or biological effect, resulting in "intake" TEFs. At present, there is insufficient data available to conclude that intake TEFs are also applicable for systemic concentrations (e.g., blood and tissues).

OBJECTIVE

We compared intake and systemic REPs of 1,2,3,7,8-pentachlorodibenzodioxin (PeCDD), 2,3,4,7,8-pentachlorodibenzofuran (4-PeCDF), 3,3',4,4',5-pentachlorobiphenyl (PCB-126), 2,3',4,4',5-pentachlorobiphenyl (PCB-118), and 2,3,3',4,4',5-hexachlorobiphenyl (PCB-156) in female C57BL/6 mice 3 days after a single oral dose.

METHODS

We calculated intake REPs and systemic REPs based on administered dose and liver, adipose, or plasma concentrations relative to TCDD. Hepatic cytochrome P450 1A1-associated ethoxyresorufin-O-deethylase (EROD) activity and gene expression of Cyp1a1, 1a2 and 1b1 in the liver and peripheral blood lymphocytes (PBLs) were used as biological end points.

RESULTS

We observed up to one order of magnitude difference between intake REPs and systemic REPs. Two different patterns were discerned. Compared with intake REPs, systemic REPs based on plasma or adipose levels were higher for PeCDD, 4-PeCDF, and PCB-126 but lower for the mono-ortho PCBs 118 and 156.

CONCLUSIONS

Based on these mouse data, the comparison between intake REPs and systemic REPs reveals significant congener-specific differences that warrants the development of systemic TEFs to calculate toxic equivalents (TEQs) in blood and body tissues.

Chemoprevention of benzo(a)pyrene-induced colon polyps in ApcMin mice by resveratrol

Human dietary exposure to benzo(a)pyrene (BaP) has generated interest with regard to the association of BaP with gastrointestinal carcinogenesis. Since colon cancer ranks third among cancer-related mortalities, it is necessary to evaluate the effect of phytochemicals on colon cancer initiation and progression. In this study, we investigated the preventive effects of resveratrol (RVT) on BaP-induced colon carcinogenesis in Apc(Min) mouse model. For the first group of mice, 100 μg BaP/kg body weight was administered to mice in peanut oil via oral gavage over a 60-day period. For the second group, RVT was coadministered with BaP at a dose of 45 μg/kg. For the third group, RVT was administered for 1 week prior to BaP exposure for 60 days. Jejunum, colon and liver were collected at 60 days post BaP and RVT exposure; adenomas in jejunum and colon were counted and subjected to histopathology. RVT reduced the number of colon adenomas in BaP+RVT-treated mice significantly compared to that in mice that received BaP alone. While dysplasia of varying degrees was noted in colon of BaP-treated mice, the dysplasias were of limited occurrence in RVT-treated mice. To ascertain whether the tumor inhibition is a result of altered BaP-induced toxicity of tumor cells, growth, apoptosis and proliferation of adenocarcinoma cells were assessed posttreatment with RVT and BaP. Cotreatment with RVT increased apoptosis and decreased cell proliferation to a greater extent than with BaP alone. Overall, our observations reveal that RVT inhibits colon tumorigenesis when given together with BaP and holds promise as a therapeutic agent.

Mechanisms of plant polyphenols anti-cancer effects I. Blockade of carcinogenesis initiation

Mechanisms of anti-cancer effects of polyphenols, found in fruits, vegetables, spices and representing parts of daily nutrition, have been considered. These compounds may be the basis for development of cancer preventive preparations. They can block carcinogenesis initiation by inactivation of exogenous or endogenous genotoxic molecules including reactive oxygen species. Another mechanism consists in inhibition of activity and synthesis of carcinogen-metabolizing enzymes. Plant polyphenols also induce expression of antioxidant and detoxification enzymes genes.

What is new for an old molecule? Systematic review and recommendations on the use of resveratrol

Background

Resveratrol is a natural compound suggested to have beneficial health effects. However, people are consuming resveratrol for this reason without having the adequate scientific evidence for its effects in humans. Therefore, scientific valid recommendations concerning the human intake of resveratrol based on available published scientific data are necessary. Such recommendations were formulated after the Resveratrol 2010 conference, held in September 2010 in Helsingør, Denmark.

Methodology

Literature search in databases as PubMed and ISI Web of Science in combination with manual search was used to answer the following five questions: ¹Can resveratrol be recommended in the prevention or treatment of human diseases?; ²Are there observed “side effects” caused by the intake of resveratrol in humans?; ³What is the relevant dose of resveratrol?; ⁴What valid data are available regarding an effect in various species of experimental animals?; ⁵Which relevant (overall) mechanisms of action of resveratrol have been documented?

Conclusions/Significance

The overall conclusion is that the published evidence is not sufficiently strong to justify a recommendation for the administration of resveratrol to humans, beyond the dose which can be obtained from dietary sources. On the other hand, animal data are promising in prevention of various cancer types, coronary heart diseases and diabetes which strongly indicate the need for human clinical trials. Finally, we suggest directions for future research in resveratrol regarding its mechanism of action and its safety and toxicology in human subjects.

Dietary flavonoids as cancer prevention agents

Dietary agents identified from fruits and vegetables contribute to keeping balanced cell proliferation and preventing cell carcinogenesis. Dietary flavonoids, combined with other components such as various vitamins, play an important role in cancer prevention. Flavonoids act on reactive oxygen species, cell signal transduction pathways related to cellular proliferation, apoptosis, and angiogenesis. Many studies demonstrate that flavonoids are responsible for chemoprevention, although mechanisms of action remain to be investigated. Overall, exciting data show that dietary flavonoids could be considered as a useful cancer preventive approach. This review summarizes recent advancements on potential cancer preventive effects and mechanic insight of dietary flavonoids.

Biotransformation of benzo[a]pyrene in Ahr knockout mice is dependent on time and route of exposure

Benzo[a]pyrene (BP) is an ubiquitous environmental pollutant with potent mutagenic and carcinogenic properties. The Ah receptor (Ahr) is important in the metabolic activation of BP and is therefore central to BP-induced carcinogenesis. Although Ahr(-/-) mice are refractory to BP-induced carcinogenesis, higher levels of BP-DNA and -protein adducts were formed in them than in wild-type mice. These results indicated the presence of an Ahr-independent and/or a slower biotransformation of BP in Ahr knockout mice. To address this issue further, we have now performed a time-course experiment, with mice receiving a single oral dose of BP (100 mg/kg). Wild-type mice have an effective clearance of BP metabolites, mainly through 3-hydroxybenzo[a]pyrene and 9-hydroxybenzo[a]pyrene in the feces with reduced levels of DNA and protein adducts in the examined tissues. On the other hand, the Ahr(-/-) mice appear to have a lower metabolic clearance of BP resulting in increased levels of DNA and protein adducts and of unmetabolized BP. In addition, we have performed an administration route experiment and found that skin-exposed Ahr(-/-) mice showed lower levels of protein adducts along with markedly reduced P450 1B1 expression, but only in the exposed area, as compared with the wild-type mice. In addition, the systemic uptake of BP is increased in the Ahr(-/-) mice as compared with the wild-type mice. Hence, the lack of a functional Ah receptor results in an Ahr-independent biotransformation of BP with a slower clearance of BP and higher levels of DNA and protein adducts, but the distribution and levels of BP and BP-protein adducts are clearly dependent on the route of exposure.

Tea polyphenols inhibit cyclooxygenase-2 expression and block activation of nuclear factor-kappa B and Akt in diethylnitrosoamine induced lung tumors in Swiss mice

BACKGROUND

Due to lack of validated screening methods and hence poor prognosis, treatment of lung cancer has not still improved up to the expectations. Therefore, risk of lung cancer needs to be minimized by efficient preventive measures. Tea (Camellia sinensis) and its bioactive polyphenols have been associated with prevention of human cancer for several organs. Thus, intake of tea polyphenols seems to be a viable mean to control lung cancer burden. In the present study, we studied the chemopreventive effects of green tea polyphenols (GTP) and black tea polyphenols (BTP) against diethylnitrosoamine (DEN) induced lung tumors in Swiss albino mice.

RESULTS

Chemopreventive potential of tea polyphenols, was recorded as evident by, low incidence of alveologenic tumors in lungs of animals at tested doses (0.1% and 0.2% of both GTP and BTP) when compared with DEN (20 mg/kg b wt) treated animals. As a mechanism of cancer chemoprevention cellular signaling pathways were also targeted. GTP and BTP treatment inhibited the expression of Akt, cyclooxygenase-2 and inactivated nuclear factor-kappa B via blocking phosphorylation and subsequent degradation of IkappaB alpha.

CONCLUSION

Thus, the study suggests that polyphenolic constituents of both cultivars of tea, i.e. green and black, have chemopreventive effects in DEN induced lung tumorigenesis in Swiss albino mice.

Cancer prevention and treatment with resveratrol: from rodent studies to clinical trials

Resveratrol (3,4',5-trihydroxy-trans-stilbene) is a dietary polyphenol derived from grapes, berries, peanuts, and other plant sources. During the last decade, resveratrol has been shown to possess a fascinating spectrum of pharmacologic properties. Multiple biochemical and molecular actions seem to contribute to resveratrol effects against precancerous or cancer cells. Resveratrol affects all three discrete stages of carcinogenesis (initiation, promotion, and progression) by modulating signal transduction pathways that control cell division and growth, apoptosis, inflammation, angiogenesis, and metastasis. The anticancer property of resveratrol has been supported by its ability to inhibit proliferation of a wide variety of human tumor cells in vitro. These in vitro data have led to numerous preclinical animal studies to evaluate the potential of this drug for cancer chemoprevention and chemotherapy. This review provides concise, comprehensive data from preclinical in vivo studies in various rodent models of human cancers, highlighting the related mechanisms of action. Bioavailability, pharmacokinetic, and potential toxicity studies of resveratrol in humans and ongoing interventional clinical trials are also presented. The conclusion describes directions for future resveratrol research to establish its activity and utility as a human cancer preventive and therapeutic drug.

Alteration of xenobiotic metabolizing enzymes by resveratrol in liver and lung of CD1 mice

Conflicting data on the anticancer properties of the polyphenolic natural product resveratrol (RSV) have been reported. Since the inhibition of "bioactivating" Phase-I xenobiotic metabolizing enzymes (XMEs) and/or induction of "detoxifying" Phase-II XMEs have long been considered important cancer chemopreventive strategies, in the current study we investigated the effect of RSV treatment on several Cytochrome P450 (CYP)-dependent oxidations and Phase-II markers in liver and lung subcellular preparations from CD1 male mice. These mice were i.p treated with RSV (25 or 50mg/Kg b.w.) daily for one or for seven consecutive days. Using either specific probes for different CYPs, or the regio- and stereo-selective metabolism of testosterone, we found that most of the Phase-I XMEs were significantly suppressed (up to approximately 61% loss for the CYP3A1/2-linked 6 beta-hydroxylation of testosterone in liver and up to approximately 97% loss for 2 alpha-hydroxylase in lung) following RSV treatment for 7 days at 50mg/kg b.w. Glutathione S-transferase was significantly inhibited, particularly in lung (approximately 76% loss of activity) after single administration of 25mg/kg b.w. A different response for the UDP-glucuronosyl transferase was observed, where a significant induction was seen (approximately 83%) in the liver and a significant reduction was observed in the lung (up to approximately 83% loss) following treatment with 25mg/kg b.w. for seven days. These data indicate that murine XMEs are altered by RSV, and that this alteration is dependent on the RSV dose, duration and way of administration. These results could provide mechanistic explanations for the conflicting chemopreventive results reported for RSV.

Grapes and human health: a perspective

Grapes are a valuable source of numerous phytonutrients, including the intensively studied constituent, resveratrol. A question worth addressing is the potential of dietary grape consumption to positively modulate human health. Many studies have suggested cardiovascular benefits, and some work has indicated cancer chemopreventive activity. Data are particularly compelling in the area of skin cancer prevention. With financial support provided by the California Table Grape Commission, novel and exciting preliminary data are emerging from independent research suggesting beneficial activity against other less prevalent but devastating illnesses, such as Alzheimer's disease and urinary bladder dysfunction. It is further suggested that some of the copious amounts of data obtained with resveratrol may be relevant to grape consumption, especially responses that can be mediated by low concentrations of the substance. Whether future specific health claims will be sought from or allowed by regulatory authorities is not known, but based on existing data, it is clear that grapes should be considered an integral component of fruit and vegetable enriched diets that are recommended by health authorities and widely accepted as beneficial for human health and disease prevention.

Molecular mechanisms of resveratrol action in lung cancer cells using dual protein and microarray analyses

Resveratrol, a natural phytoestrogen found in red wine and a variety of plants, is reported to have protective effects against lung cancer; however, there is little work directed toward the understanding of the mechanism of its action in this disease. In this study, we used a combination of experimental approaches to understand the biological activity and molecular mechanisms of resveratrol. Microarray gene expression profiling and high-throughput immunoblotting (PowerBlot) methodologies were employed to gain insights into the molecular mechanisms of resveratrol action in human lung cancer cells. In this report, we confirm the up-regulation of p53 and p21 and the induction of apoptosis by the activation of the caspases and the disruption of the mitochondrial membrane complex. We show the arrest of A549 cells in the G(1) phase of cell cycle in the presence of resveratrol and also report alterations in both gene and protein expressions of cyclin A, chk1, CDC27, and Eg5. Furthermore, the results indicated that resveratrol action is mediated via the transforming growth factor-beta pathway, particularly through the Smad proteins. Results showed the down-regulation of the Smad activators 2 and 4 and the up-regulation of the repressor Smad 7 as a result of resveratrol treatment. Resveratrol is a potent inhibitor of A549 lung cancer cell growth, and our results suggest that resveratrol may be a promising chemopreventive or chemotherapeutic agent for lung cancer.

Predicting the physiological relevance of in vitro cancer preventive activities of phytochemicals

There is growing interest in the ability of phytochemicals to prevent chronic diseases, such as cancer and heart disease. However, some of these agents have poor bioavailability and many of the in-depth studies into their mechanisms of action have been carried out in vitro using doses which are unachievable in humans. In order to optimize the design of chemopreventive treatment, it is important to determine which of the many reported mechanisms of action are clinically relevant. In this review we consider the physiologically achievable doses for a few of the best studied agents (indole-3-carbinol, diindolylmethane, curcumin, epigallocatechin-3-gallate and resveratrol) and summarize the data derived from studies using these low concentrations in cell culture. We then cite examples of in vitro effects which have been observed in vivo. Finally, the ability of agent combinations to act synergistically or antagonistically is considered. We conclude that each of the compounds shows an encouraging range of activities in vitro at concentrations which are likely to be physiologically relevant. There are also many examples of in vivo studies which validate in vitro observations. An important consideration is that combinations of agents can result in significant activity at concentrations where any single agent is inactive. Thus, for each of the compounds reviewed here, in vitro studies have provided useful insights into their mechanisms of action in humans. However, data are lacking on the full range of activities at low doses in vitro and the benefits or otherwise of combinations in vivo.

Anthocyanin-Rich Grape Extract Blocks Breast Cell DNA Damage

Anthocyanins, belonging to the flavonoid family of phytochemicals, have received attention as agents that may have potential in preventing chronic diseases such as cardiovascular diseases and certain cancers. In the present study, an anthocyanin-rich extract from Concord grapes [referred to as Concord grape extract (CGE)] and the anthocyanin delphinidin were evaluated for their capacity to inhibit DNA adduct formation due to the environmental carcinogen benzo[a]pyrene (BP) in MCF-10F cells, a noncancerous, immortalized human breast epithelial cell line. CGE at 10 and 20 microg/mL and delphinidin at 0.6 microM concentrations significantly inhibited BP-DNA adduct formation. This was associated with a significant increase in activities of the phase II detoxification enzymes glutathione S-transferase and NAD(P)H:quinone reductase 1. In addition, these grape components also suppressed reactive oxygen species (ROS) formation, but did not induce antioxidant response element-dependent transcription. Taken together, these data suggest that CGE and a component grape anthocyanin have breast cancer chemopreventive potential due in part to their capacity to block carcinogen-DNA adduct formation, modulate activities of carcinogen-metabolizing enzymes, and suppress ROS in these noncancerous human breast cells.

Resveratrol: a review of preclinical studies for human cancer prevention

The search for novel and effective cancer chemopreventive agents has led to the identification of various naturally occurring compounds one of which is resveratrol (trans-3,4',5-trihydroxystilbene), a phytoalexin derived from the skin of grapes and other fruits. Resveratrol is known to have potent anti-inflammatory and antioxidant effects and to inhibit platelet aggregation and the growth of a variety of cancer cells. Its potential chemopreventive and chemotherapeutic activities have been demonstrated in all three stages of carcinogenesis (initiation, promotion, and progression), in both chemically and UVB-induced skin carcinogenesis in mice, as well as in various murine models of human cancers. Evidence from numerous in vitro and in vivo studies has confirmed its ability to modulate various targets and signaling pathways. This review discusses the current preclinical and mechanistic data available and assesses resveratrol's anticancer effects to support its potential as an anticancer agent in human populations.

Lack of promotion of mammary, lung and skin tumorigenesis by 20 kHz triangular magnetic fields

In order to evaluate possible tumorigenic effects of a 20 kHz intermediate frequency triangular magnetic field (IF), a frequency emitted from TV and PC monitors at 6.25 microT rms, which is the regulated exposure limit of magnetic field for the public in Korea, mammary tumors were produced in female Sprague-Dawley rats by oral intubation of dimethylbenz(a)anthracene (DMBA), lung tumors in ICR mice by scapular region injection of benzo(a)pyrene (BP), and skin tumors in female ICR mice by topical application of DMBA and tetradecanoylphorbol ester (TPA). IF was applied 8 h/day for 14 weeks beginning the day after DMBA treatment for mammary tumor experiment, for 6 weeks after weaning for lung tumor, and for 20 weeks beginning 1 week after DMBA application for skin tumor experiment. For skin tumors, TPA was applied once a week for 19 weeks. Results showed no significant differences in tumor incidence, mean tumor number and volume, and histological patterns between IF magnetic-field exposed and sham control rats in the above three tumor models. Therefore, we conclude that within the limitation or number of animals and the experimental conditions, 20 kHz IF triangular magnetic field exposure of 6.25 microT does not appear to be a strong co-tumorigenic agent in the chosen murine mammary, lung and skin models.

Quantitative analysis of benzo[a]pyrene biotransformation and adduct formation in Ahr knockout mice

Benzo[a]pyrene (BP) is an ubiquitous environmental pollutant with potent mutagenic and carcinogenic properties. The Ah receptor (Ahr) is involved in the metabolic activation of BP and is therefore important in the induction of chemical carcinogenesis. In this study, the relationship between Ahr genotype and biotransformation of BP in internal organs was investigated in Ahr (+/+), Ahr (+/-) and Ahr (-/-) mice. The mice were treated with BP (100mg/kg) by gavage. Gene expression was measured after 24h by real-time RT-PCR and showed induction of Cyp1a1 in liver and lung, and Cyp1b1 in lung in both Ahr (+/+) and Ahr (+/-). No induction of the Cyp genes was observed in the Ahr (-/-). There was a significant basal expression of Cyp1b1 in the liver of all genotypes, and this expression was independent of the BP exposure. Analyzed by HPLC-fluorescence, there were increased levels of protein and DNA adducts, metabolites, conjugates and unmetabolized BP in the internal organs of Ahr (-/-) as compared to Ahr (+/+) and Ahr (+/-) mice. This may be partly explained by a delayed bioactivation of BP in the Ahr deficient mice. The BP metabolism observed in the Ahr (-/-) mice is also evidence of an Ahr independent biotransformation of BP.

Oncogenicity evaluation of resveratrol in p53(+/-) (p53 knockout) mice

A six-month study was conducted in p53(+/-) mice to evaluate the possible oncogenicity of resveratrol (3,5,4'-trihydroxy-trans-stilbene), a cancer chemopreventive agent present in grapes and other foods. p53(+/-) mice (25/sex/group) received daily gavage exposure to vehicle only (negative control), resveratrol doses of 1000, 2000, or 4000 mg/kg/day, or p-cresidine (400 mg/kg/day; positive control). No mortality was seen in mice receiving the low dose of resveratrol. However, the mid and high doses induced mortality associated with impaction of the test article in the gastrointestinal tract. Resveratrol had no effect on body weight, food consumption, or clinical signs in surviving mice in any dose group, but induced dose-related increases in liver weight and serum cholesterol in both sexes. Mild anemia was seen in male mice at the high dose only; hematologic effects were not seen in females. Histopathology identified the kidney (hydronephrosis) and urinary bladder (epithelial hyperplasia) as target tissues for resveratrol toxicity. The incidences of both benign and malignant tumors in mice exposed to resveratrol were comparable to those in vehicle controls. By contrast, the positive control article, p-cresidine, induced urinary bladder cancer in both sexes. When administered to p53(+/-) mice at its maximum tolerated dose, resveratrol demonstrates no evidence of oncogenicity.

Therapeutic potential of resveratrol: the in vivo evidence

Resveratrol, a constituent of red wine, has long been suspected to have cardioprotective effects. Interest in this compound has been renewed in recent years, first from its identification as a chemopreventive agent for skin cancer, and subsequently from reports that it activates sirtuin deacetylases and extends the lifespans of lower organisms. Despite scepticism concerning its bioavailability, a growing body of in vivo evidence indicates that resveratrol has protective effects in rodent models of stress and disease. Here, we provide a comprehensive and critical review of the in vivo data on resveratrol, and consider its potential as a therapeutic for humans.

Preferential induction of CYP1B1 by benzo[ a ]pyrene in human oral epithelial cells: impact on DNA adduct formation and prevention by polyphenols

The roles of CYP1A1 and 1B1 in tobacco smoke carcinogen, e.g. benzo[a]pyrene (BaP), induced DNA binding and their inhibition by the dietary polyphenol 5,7-dimethoxyflavone (DMF), compared with 3',4'-dimethoxyflavone (3',4'-DMF) and resveratrol, were investigated in the human oral epithelial squamous cell carcinoma (SCC)-9 cells. A low concentration of BaP (1 microM) dramatically induced BaP-DNA adduct formation (approximately 40-fold) in a time-dependent manner, while it only increased CYP1A1/1B1 activities, as measured by ethoxyresorufin O-deethylation, approximately 3-fold. Furthermore, BaP induced both CYP1B1 and CYP1A1 mRNA and protein expression, as determined by the branched DNA assay and western blot analysis, but with considerably higher levels of CYP1B1. Combined treatment of SCC-9 cells with 1 microM BaP and 20 microM DMF inhibited BaP-DNA adduct formation. The mechanism of this effect appeared to be direct inhibition of CYP1B1 enzyme with a K(i) value of 0.58 microM, a highly potent inhibition considering the high cellular uptake of DMF in the SCC-9 cells. DMF also inhibited CYP1A1, but not CYP1B1 protein, and mRNA expression in the cells. In an extension to other polyphenols, the structural analog 3',4'-DMF, in contrast to DMF, inhibited the expression of CYP1B1 both at the mRNA and protein levels. Surprisingly, in contrast to previous studies in other cell types, resveratrol had no effect on CYP1B1 in the SCC-9 cells. Based on this study, CYP1B1 mRNA may be an early biomarker of oral cancer, being a sensitive signal for tobacco-carcinogen exposure. Methoxylated dietary flavonoids, e.g. DMF and 3',4'-DMF, may be potent chemoprotectants by direct inhibition of CYP1B1/1A1 function and/or their protein expression.

Molecular mechanisms of the chemopreventive effects of resveratrol and its analogs in carcinogenesis

Resveratrol (3,4',5-trihydroxy-trans-stilbene), a phytoalexin found in grape skins, peanuts, and red wine, has been reported to exhibit a wide range of biological and pharmacological properties. It has been speculated that dietary resveratrol could be an explanation for the so-called 'French paradox' as it may act as an antioxidant, promote nitric oxide production, inhibit platelet aggregation, and increase high-density lipoprotein cholesterol, and thereby serve as a cardioprotective agent. Recently, it has been demonstrated that resveratrol can function as a cancer chemopreventive agent, and there has been a great deal of experimental effort directed toward defining this effect. It has been shown that resveratrol and some of its analogs interfere with signal transduction pathways, modulate cell cycle-regulating proteins, and is a potent inducer of apoptosis in multiple carcinoma cell lines. This review summarizes the recent advances that have provided new insights into the molecular mechanisms underlying the promising properties of resveratrol.

Role of cell signaling in B[a]P-induced apoptosis: characterization of unspecific effects of cell signaling inhibitors and apoptotic effects of B[a]P metabolites

Here we show that several cell signaling inhibitors have effect on cyp1a1 expression and the metabolism of benzo[a]pyrene (B[a]P) in Hepa1c1c7 cells. The CYP1A1 inhibitor alpha-naphthoflavone (alpha-NF), the p53 inhibitor pifithrin-alpha (PFT-alpha), the ERK inhibitors PD98059 and U0126, and the p38 MAPK inhibitors SB202190 and PD169316 induced the expression and level of cyp1a1 protein. On the other hand, during the first h the inhibitors appeared to reduce the metabolism of B[a]P as measured by the generation of tetrols and by covalent binding of B[a]P to macromolecules. In contrast, the phosphatidylinositol-3 (PI-3) kinase inhibitor wortmannin, had neither an effect on the cyp1a1 expression nor the B[a]P-metabolism. In order to avoid these unspecific effects, we characterized the mechanisms involved in the apoptotic effects of B[a]P-metabolites. B[a]P and the B[a]P-metabolites B[a]P-7,8-DHD and BPDE-I induced apoptosis, whereas B[a]P-4,5-DHD had no effect. B[a]P, B[a]P-7,8-DHD and BPDE-I induced an accumulation and phosphorylation of p53, while the Bcl-2 proteins Bcl-xl, Bad and Bid were down-regulated. Interestingly, the levels of anti-apoptotic phospho-Bad were up-regulated in response to B[a]P as well as to B[a]P-7,8-DHD and BPDE-I. Both p38 MAPK and JNK were activated, but the p38 MAPK inhibitors were not able to inhibit BPDE-I-induced apoptosis. PFT-alpha reduced the BPDE-I-induced apoptosis, while both the PI-3 kinase inhibitor and the ERK inhibitors increased the apoptosis in combination with BPDE-I. BPDE-I also triggered apoptosis in primary cultures of rat lung cells. In conclusion, often used cell signaling inhibitors both enhanced the expression and the level of cyp1a1 and more directly acted as inhibitors of cyp1a1 metabolism of B[a]P. However, studies with the B[a]P-metabolite BPDE-I supported the previous suggestion that p53 has a role in the pro-apoptotic signaling pathway induced by B[a]P. Furthermore, these studies also show that the reactive metabolites of B[a]P induce the anti-apoptotic signals, Akt and ERK. Neither the induction nor the activity of p38 MAPK and JNK seems to be of major importance for the B[a]P-induced apoptosis.