John M. Pezzuto

Resveratrol Inhibits Cyclooxygenase-2 Transcription and Activity in Phorbol Ester-treated Human Mammary Epithelial Cells

We determined whether resveratrol, a phenolic antioxidant found in grapes and other food products, inhibited phorbol ester (PMA)-mediated induction of COX-2 in human mammary and oral epithelial cells. Treatment of cells with PMA induces COX-2 and causes a marked increase in the production of prostaglandin E2. These effects were inhibited by resveratrol. Resveratrol suppressed PMA-mediated increases in COX-2 mRNA and protein. Nuclear run-offs revealed increased rates of COX-2transcription after treatment with PMA, an effect that was inhibited by resveratrol. PMA caused about a 6-fold increase in COX-2promoter activity, which was suppressed by resveratrol. Transient transfections utilizing COX-2 promoter deletion constructs and COX-2 promoter constructs, in which specific enhancer elements were mutagenized, indicated that the effects of PMA and resveratrol were mediated via a cyclic AMP response element. Resveratrol inhibited PMA-mediated activation of protein kinase C. Overexpressing protein kinase C-α, ERK1, and c-Jun led to 4.7-, 5.1-, and 4-fold increases in COX-2 promoter activity, respectively. These effects also were inhibited by resveratrol. Resveratrol blocked PMA-dependent activation of AP-1-mediated gene expression. In addition to the above effects on gene expression, we found that resveratrol also directly inhibited the activity of COX-2. These data are likely to be important for understanding the anti-cancer and anti-inflammatory properties of resveratrol.

Plant-derived anticancer agents

Natural product drugs play a dominant role in pharmaceutical care. This is especially obvious in the case of antitumor drugs, as exemplified by paclitaxel (Taxol), vincristine (Oncovin), vinorelbine (Navelbine), teniposide (Vumon), and various water-soluble analogs of camptothecin (e.g., Hycamtin). The most efficient method of discovering drugs such as these (i.e. novel chemical prototypes that may function through unique mechanisms of action) is bioactivity-guided fractionation, and it is certain that additional natural product drugs, some of which should be useful for the treatment of humans, remain to be discovered. For the commercial procurement of structurally complex natural product drugs, isolation from plant material may be most practical. With the advent of combinatorial chemistry and high throughput screening, however, even greater progress may now be expected with natural product leads. While systemic drug therapy, to an appreciable extent based on natural products, has been the mainstay of pharmaceutical care, the logic of disease prevention is overwhelming. Bearing in mind the pandemic nature of cancer, a proposal is put forth to create a cancer chemoprevention drug formulation for utilization on a widespread basis by the general population. Cancer chemopreventive agents, many of which are natural products, are capable of preventing or inhibiting the process of carcinogenesis. As with other pharmaceutical agents useful for disease prevention, a pharmacoeconomic analysis of a cancer chemopreventive formulation would need to be considered, and the composition of the formulation should improve over time. Nonetheless, implementation should commence immediately.

Botanicals in cancer chemoprevention.

Botanicals have been used for the treatment of various human diseases throughout history. In addition, botanicals play a role in disease prevention. For example, epidemiologic studies have suggested that a reduced risk of cancer is associated with high consumption of vegetables and fruits. Thus, the cancer chemopreventive potential of naturally occurring phytochemicals is of great interest. In this review, we discuss the cancer chemopreventive activity of cruciferous vegetables such as cabbage and broccoli, Allium vegetables such as garlic and onion, green tea, Citrus fruits, tomatoes, berries, ginger and ginseng, as well as some medicinal plants. In addition, methods for the discovery of active compounds from plant sources are described. Several lead compounds, such as brassinin (from cruciferous vegetables like Chinese cabbage), sulforaphane (from broccoli) and its analog sulforamate, withanolides (from tomatillos), and resveratrol (from grapes and peanuts among other foods), are in preclinical or clinical trials for cancer chemoprevention. Phytochemicals of these types have great potential in the fight against human cancer, and a variety of delivery methods are available as a result of their occurrence in nature.

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.

Cancer Prevention With Natural Compounds

Botanical and nutritional compounds have been used for the treatment of cancer throughout history. These compounds also may be useful in the prevention of cancer. Population studies suggest that a reduced risk of cancer is associated with high consumption of vegetables and fruits. Thus, the cancer chemopreventive potential of naturally occurring phytochemicals is of great interest. There are numerous reports of cancer chemopreventive activity of dietary botanicals, including cruciferous vegetables such as cabbage and broccoli, Allium vegetables such as garlic and onion, green tea, Citrus fruits, soybeans, tomatoes, berries, and ginger, as well as medicinal plants. Several lead compounds, such as genistein (from soybeans), lycopene (from tomatoes), brassinin (from cruciferous vegetables), sulforaphane (from asparagus), indole-3-carbinol (from broccoli), and resveratrol (from grapes and peanuts) are in preclinical or clinical trials for cancer chemoprevention. Phytochemicals have great potential in cancer prevention because of their safety, low cost, and oral bioavailability. In this review, we discuss potential natural cancer preventive compounds and their mechanisms of action.

Human, rat, and mouse metabolism of resveratrol.

AbstractPurpose. Resveratrol, a phenolic phytoalexin occurring in grapes, wine, peanuts, and cranberries, has been reported to have anticarcinogenic, antioxidative, phytoestrogenic, and cardioprotective activities. Because little is known about the metabolism of this potentially important compound, the in vitro and in vivo metabolism of trans-resveratrol were investigated. Methods. The in vitro experiments included incubation with human liver microsomes, human hepatocytes, and rat hepatocytes and the in vivo studies included oral or intraperitoneal administration of resveratrol to rats and mice. Methanol extracts of rat urine, mouse serum, human hepatocytes, rat hepatocytes, and human liver microsomes were analyzed for resveratrol metabolites using reversed-phase high-performance liquid chromatography with on-line ultraviolet-photodiode array detection and mass spectrometric detection (LC-DAD-MS and LC-UV-MS-MS). UV-photodiode array analysis facilitated the identification of cis- and trans-isomers of resveratrol and its metabolites. Negative ion electrospray mass spectrometric analysis provided molecular weight confirmation of resveratrol metabolites and tandem mass spectrometry allowed structural information to be obtained. Results. No resveratrol metabolites were detected in the microsomal incubations, and no phase I metabolites, such as oxidations, reductions, or hydrolyzes, were observed in any samples. However, abundant trans-resveratrol-3-O-glucuronide and trans-resveratrol-3-sulfate were identified in rat urine, mouse serum, and incubations with rat and human hepatocytes. Incubation with β-glucuronidase and sulfatase to release free resveratrol was used to confirm the structures of these conjugates. Only trace amounts of cis-resveratrol were detected, indicating that isomerization was not an important factor in the metabolism and elimination of resveratrol. Conclusion. Our results indicate that trans-resveratrol-3-O-glucuronide and trans-resveratrol-3-sulfate are the most abundant metabolites of resveratrol. Virtually no unconjugated resveratrol was detected in urine or serum samples, which might have implications regarding the significance of in vitro studies that used only unconjugated resveratrol.

A Mixed Micellar Formulation Suitable for the Parenteral Administration of Taxol

Taxol is a promising antitumor agent with poor water solubility. Intravenous administration of a current taxol formulation in a non-aqueous vehicle containing Cremophor EL may cause allergic reactions and precipitation upon aqueous dilution. In this study a novel approach to formulate taxol in aqueous medium for i.v. delivery is described. The drug is solubilized in bile salt (BS)/phospholipid (PC) mixed micelles. The solubilization potential of the mixed micelles increased as the total lipid concentration and the molar ratio of PC/BS increased. Precipitation of the drug upon dilution was avoided by the spontaneous formation of drug-loaded liposomes from mixed micelles. The formulation can be stored in a freeze-dried form as mixed micelles to achieve optimum stability, and liposomes can be prepared by simple dilution just before administration. As judged by a panel of cultured cell lines, the cytotoxic activity of taxol was retained when formulated as a mixed-micellar solution. Further, for the same solubilization potential, the mixed-micellar vehicle appeared to be less toxic than the standard nonaqueous vehicle of taxol containing Cremorphor EL.

The role of cyclooxygenase and lipoxygenase in cancer chemoprevention.

The involvement of prostaglandins (PGs) and other eicosanoids in the development of human cancer has been known for over two decades. Importantly, an increase in PG synthesis may influence tumor growth in human beings and experimental animals, and numerous studies have illustrated the effect of PG synthesis on carcinogen metabolism, tumor cell proliferation and metastatic potential. PGs produced by cyclooxygenases (COXs) are represented by a large series of compounds that mainly enhance cancer development and progression, acting as carcinogens or tumor promoters, with profound effects on carcinogenesis. Further investigations suggest that arachidonic acid (AA) metabolites derived from lipoxygenase (LOX) pathways play an important role in growth-related signal transduction, implying that intervention through these pathways should be useful for arresting cancer progression. We discuss here the implications of COX and LOX in colon, pancreatic, breast, prostate, lung, skin, urinary bladder and liver cancers. Select inhibitors of COX and LOX are described, including nonsteroidal antiinflammatory drugs (NSAIDs), selective COX-2 inhibitors, curcumin, tea, silymarin and resveratrol, as well as a method useful for evaluating inhibitors of COX. Although a substantial amount of additional work is required to yield a better understanding of the role of COX and LOX in cancer chemoprevention, it is clear that beneficial therapeutic effects can be realized through drug-mediated modulation of these metabolic pathways.

Evaluation of the mutagenic, cytotoxic, and antitumor potential of triptolide, a highly oxygenated diterpene isolated from Tripterygium wilfordii

Triptolide, a highly oxygenated diterpene isolated from Tripterygium wilfordii Hook f. (Celastraceae), has been shown to demonstrate potent antileukemic activity in rodent models at remarkably low treatment doses. A variety of other physiological responses are known to be mediated by this compound, including immunosuppressive and antifertility effects. We currently report that triptolide was not mutagenic toward Salmonella typhimurium strain TM677, either in the presence or absence of a metabolic activating system. Relatively potent but non-specific cytotoxicity was observed with a panel of cultured mammalian cell lines, and modest antitumor activity was observed when an i.p. dose of 25 microg was administered three times weekly to athymic mice carrying human breast tumors. Treatment regimens involving higher doses of triptolide (e.g. 50 microg/mouse three times weekly) were lethal.

NFκB: a promising target for natural products in cancer chemoprevention

The transcription factor nuclear factor kappa B (NFκB) is found in nearly all animal cell types. It is involved in cellular responses to stimuli such as stress, cytokines, free radicals, ultraviolet irradiation, oxidized LDL and microbial antigens, and has been shown to regulate the expression of a number of genes including bcl‐2, bcl‐xl, cIAP, suvivin, TRAF, COX‐2, MMP‐9, iNOS and cell cycle‐regulatory components. Many carcinogens, inflammatory agents and tumor promoters have been shown to activate NFκB, and resulting tumors demonstrate misregulated NFκB. Incorrect regulation of NFκB has been linked to inflammatory and autoimmune diseases, septic shock, viral infection and improper immune development. Aberrant regulation of NFκB is involved in cancer development and progression as well as in drug resistance. Inhibitors of NFκB mediate effects potentially leading to antitumor responses or greater sensitivity to the action of antitumor agents. Tools have been developed for the rapid assessment of NFκB activity, so in concert with a better understanding of NFκB activation mechanisms, many agents capable of suppressing NFκB activation have been identified. The present article focuses on the functions of NFκB, its role in human cancer and the therapeutic potential and benefit of targeting NFκB by natural products in cancer chemoprevention. Copyright