Chandra K. Singh

Resveratrol and cancer: Challenges for clinical translation

Significant work has been done towards identifying the health-beneficial effects of the grape antioxidant resveratrol in a variety of bioassay- and disease- models, with much research being focused on its possible application to cancer management. Despite the large number of preclinical studies dealing with different aspects of the biological effects of resveratrol, its translation to clinics is far from reality due to a variety of challenges. In this review, we discuss the issues and questions associated with resveratrol becoming an effective in vivo anticancer drug, from basic metabolic issues to the problems faced by incomplete understanding of the mechanism(s) of action in the body. We also explore efforts taken by researchers, both public and private, to contend with some of these issues. By examining the published data and previous clinical trials, we have attempted to identify the problems and issues that hinder the clinical translation of resveratrol for cancer management. This article is part of a Special Issue entitled: Resveratrol: Challenges in translating pre-clinical findings to improved patient outcomes.

Resveratrol Restores Nrf2 Level and Prevents Ethanol-Induced Toxic Effects in the Cerebellum of a Rodent Model of Fetal Alcohol Spectrum Disorders

In humans, ethanol exposure during pregnancy produces a wide range of abnormalities in infants collectively known as fetal alcohol spectrum disorders (FASD). Neuronal malformations in FASD manifest as postnatal behavioral and functional disturbances. The cerebellum is particularly sensitive to ethanol during development. In a rodent model of FASD, high doses of ethanol (blood ethanol concentration 80 mM) induces neuronal cell death in the cerebellum. However, information on potential agent(s) that may protect the cerebellum against the toxic effects of ethanol is lacking. Growing evidence suggests that a polyphenolic compound, resveratrol, has antioxidant and neuroprotective properties. Here we studied whether resveratrol (3,5,4′-trihydroxy-trans-stilbene), a phytoalexin found in red grapes and blueberries, protects the cerebellar granule neurons against ethanol-induced cell death. In the present study, we showed that administration of resveratrol (100 mg/kg) to postnatal day 7 rat pups prevents ethanol-induced apoptosis by scavenging reactive oxygen species in the external granule layer of the cerebellum and increases the survival of cerebellar granule cells. It restores ethanol-induced changes in the level of transcription factor nuclear factor-erythroid derived 2-like 2 (nfe2l2, also known as Nrf2) in the nucleus. This in turn retains the expression and activity of its downstream gene targets such as NADPH quinine oxidoreductase 1 and superoxide dismutase in cerebellum of ethanol-exposed pups. These studies indicate that resveratrol exhibits neuroprotective effects in cerebellum by acting at redox regulating proteins in a rodent model of FASD.

Resveratrol-based combinatorial strategies for cancer management.

In recent years combination chemoprevention has been increasingly appreciated and investigated as a viable and effective strategy for cancer management. A plethora of evidence suggests that a combination of agents may afford synergistic (or additive) advantage for cancer management by multiple means, such as by (1) enhancing the bio‐availability of chemopreventive agents, (2) modifying different molecular targets, and (3) lowering the effective dose of agent/drug to be used for cancer management. Resveratrol has been shown to afford chemopreventive and therapeutic effects against certain cancers. Recent studies are suggesting that resveratrol may be very useful when given in combination with other agents. The two major advantages of using resveratrol in combination with other agents are synergistically or additively enhancing the efficacy against cancer and limiting the toxicity and side effects of existing therapies. However, concerted and multidisciplinary efforts are needed to identify the most optimal combinatorial strategies.

SIRT1 deacetylase is overexpressed in human melanoma and its small molecule inhibition imparts anti-proliferative response via p53 activation

Melanoma causes more deaths than any other skin cancer, and its incidence in the US continues to rise. Current medical therapies are insufficient to control this deadly neoplasm, necessitating the development of new target-based approaches. The objective of this study was to determine the role and functional significance of the class III histone deacetylase SIRT1 in melanoma. We have found that SIRT1 is overexpressed in clinical human melanoma tissues and human melanoma cell lines (Sk-Mel-2, WM35, G361, A375, and Hs294T) compared to normal skin and normal melanocytes, respectively. In addition, treatment of melanoma cell lines A375, Hs294T, and G361 with Tenovin-1, a small molecule SIRT1 inhibitor, resulted in a significant decrease in cell growth and cell viability. Further, Tenovin-1 treatment also resulted in a marked decrease in the clonogenic survival of melanoma cells. Further experiments showed that the anti-proliferative response of Tenovin-1 was accompanied by an increase in the protein as well as activity of the tumor suppressor p53. This increase in p53 activity was substantiated by an increase in the protein level of its downstream target p21. Overall, these data suggest that small molecule inhibition of SIRT1 causes anti-proliferative effects in melanoma cells. SIRT1 appears to be acting through the activity of the tumor suppressor p53, which is not mutated in the majority of melanomas. However, future detailed studies are needed to further explore the role and mechanism of SIRT1 in melanoma development and progression and its usefulness in melanoma treatment.

Diabetic complications in pregnancy: is resveratrol a solution?

Diabetes is a metabolic disorder that, during pregnancy, may affect fetal development. Fetal outcome depends on the type of diabetes present, the concentration of blood glucose and the extent of fetal exposure to elevated or frequently fluctuating glucose concentrations. The result of some diabetic pregnancies will be embryonic developmental abnormalities, a condition referred to as diabetic embryopathy. Tight glycemic control in type 1 diabetes during pregnancy using insulin therapy together with folic acid supplementation are partially able to prevent diabetic embryopathy; however, the protection is not complete and additional interventions are needed. Resveratrol, a polyphenol found largely in the skins of red grapes, is known to have antidiabetic action and is in clinical trials for the treatment of diabetes, insulin resistance, obesity and metabolic syndrome. Studies of resveratrol in a rodent model of diabetic embryopathy reveal that it significantly improves the embryonic outcome in terms of diminishing developmental abnormalities. Improvements in maternal and embryonic outcomes observed in rodent models may arise from resveratrols antioxidative potential, antidiabetic action and antidyslipidemic nature. Whether resveratrol will have similar actions in human diabetic pregnancy is unknown. Here, we review the potential therapeutic use of resveratrol in diabetes and diabetic pregnancy.

Resveratrol, in its natural combination in whole grape, for health promotion and disease management

The grape antioxidant resveratrol has been a topic of intense research for the past three decades. Resveratrol and other grape ingredients, as well as whole‐grape products, have shown considerable promise in health promotion and disease management. Phytochemically, whole grape represents a natural combination of resveratrol and other phytonutrients, as it contains several catechins, anthocyanins, polyphenols, and flavonols. Thus, whole grape products or specific combinations of grape constituents provide us with the possibility of synergistic interactions leading to improved efficacy. Recent research has suggested that whole‐grape products may help in maintaining heart health and protect against aging, aging‐associated diseases, neurodegeneration, and some cancers. On the basis of available recent literature, the grape fruit or whole‐grape products seem to be safer choices for better health and disease prevention. However, for advanced disease conditions, individual grape ingredients (such as resveratrol) or combinations of multiple ingredients, together with existing therapies, appear to be better approaches. Further clinical studies are needed to understand the benefits of grapes and their products in the prevention and management of specific diseases.

Targeted nanoparticles encapsulating (−)-epigallocatechin-3-gallate for prostate cancer prevention and therapy

Earlier we introduced the concept of ‘nanochemoprevention’ i.e. the use of nanotechnology to improve the outcome of cancer chemoprevention. Here, we extended our work and developed polymeric EGCG-encapsulated nanoparticles (NPs) targeted with small molecular entities, able to bind to prostate specific membrane antigen (PSMA), a transmembrane protein that is overexpressed in prostate cancer (PCa), and evaluated their efficacy in preclinical studies. First, we performed a molecular recognition of DCL- and AG-PEGylation on ligand binding on PSMA active site. Next, the biocompatible polymers PLGA-PEG-A were synthesized and used as base to conjugate DCL or AG to obtain the respective copolymers, needed for the preparation of targeted NPs. The resulting EGCG encapsulating NPs led to an enhanced anti-proliferative activity in PCa cell lines compared to the free EGCG. The behavior of EGCG encapsulated in NPs in modulating apoptosis and cell-cycle, was also determined. Then, in vivo experiments, in mouse xenograft model of prostatic tumor, using EGCG-loaded NPs, with a model of targeted nanosystems, were conducted. The obtained data supported our hypothesis of target-specific enhanced bioavailability and limited unwanted toxicity, thus leading to a significant potential for probable clinical outcome.

Resveratrol-zinc combination for prostate cancer management.

Zinc, an essential trace element, plays a critical role in cell signaling, and defect(s) in zinc homeostasis may contribute to adverse physiological and pathological conditions, including cancer. Zinc is present in healthy prostate at a very high concentration, where it is required for important prostatic functions. However, zinc levels are significantly diminished in cancerous tissue, and intracellular zinc level is inversely correlated with prostate cancer progression. During neoplastic transformation, zinc-accumulating, citrate-producing normal prostate cells are metabolically transformed to citrate oxidizing cells that lose the ability to accumulate zinc. Interestingly, zinc has been shown to function as chemopreventive agent against prostate cancer, albeit at high doses, which may lead to many adverse effects. Therefore, novel means to enhance bioaccumulation of sufficient zinc in prostate cells via increasing zinc transport could be useful against prostate cancer. On the basis of available evidence, we present a possibility that the grape antioxidant resveratrol, when given with zinc, may lead to retuning the zinc homeostasis in prostate, thereby abolishing or reversing malignancy. If experimentally verified in in vivo model(s) of prostate cancer, such as transgenic mouse models, this may lead to novel means toward management of prostate cancer and other conditions with compromised zinc homeostasis.

Sirtuin deacetylases: a new target for melanoma management.

Melanoma continues to cause more deaths than any other skin cancer, necessitating the development of new avenues of treatment. One promising new opportunity comes in the form of mechanism-based therapeutic targets. We recently reported the overexpression and delocalization of the class III histone deacetylase SIRT1 in melanoma, and demonstrated that its small molecule inhibition via Tenovin-1 decreased cell growth and viability of melanoma cells, possibly by a p53 mediated induction of p21. Here, we support our data using additional SIRT inhibitors, viz. Sirtinol and Ex-527, which suggests possible benefits of concomitantly inhibiting more than one Sirtuin for an effective cancer management strategy. This “Extra View” paper also includes a discussion of our results in the context of similar recent and concurrent studies. Furthermore, we expand upon our findings in an analysis of new research that may link the cellular localization and growth effects of SIRT1 with the PI3K signaling pathway.

Microfluidic-integrated patterned ITO immunosensor for rapid detection of prostate-specific membrane antigen biomarker in prostate cancer

An optically transparent patterned indium tin oxide (ITO) three-electrode sensor integrated with a microfluidic channel was designed for label-free immunosensing of prostate-specific membrane antigen (PSMA), a prostate cancer (PCa) biomarker, expressed on prostate tissue and circulating tumor cells but also found in serum. The sensor relies on cysteamine capped gold nanoparticles (N-AuNPs) covalently linked with anti-PSMA antibody (Ab) for target specificity. A polydimethylsiloxane (PDMS) microfluidic channel is used to efficiently and reproducibly introduce sample containing soluble proteins/cells to the sensor. The PSMA is detected and quantified by measuring the change in differential pulse voltammetry signal of a redox probe ([Fe(CN)6]3-/[Fe(CN)6]4-) that is altered upon binding of PSMA with PSMA-Ab immobilized on N-AuNPs/ITO. Detection of PSMA expressing cells and soluble PSMA was tested. The limit of detection (LOD) of the sensor for PSMA-based PCa cells is 6/40µL (i.e., 150 cells/mL) (n=3) with a linear range of 15-400 cells/40µL (i.e., 375-10,000 cells/mL), and for the soluble PSMA is 0.499ng/40µL (i.e., 12.5ng/mL) (n=3) with the linear range of 0.75-250ng/40µL (i.e., 19-6250ng/mL), both with an incubation time of 10min. The results indicate that the sensor has a suitable sensitivity and dynamic range for routine detection of PCa circulating tumor cells and can be adapted to detect other biomarkers/cancer cells.