Effects of Resveratrol on Regulation of ARV7 Protein Levels in Prostate Cancer

Prostate cancer (PCa) has become a commonly diagnosed disease and it is the second-leading cause of cancer-related deaths in the US. A normal functioning prostate is androgen-dependent because it relies on androgens and the androgen receptor (AR) for cell maintenance, proliferation, survival and growth. Normally, the AR is a full-length receptor made up for 4 protein domains: N-terminal transactivation domain (NTD), a central DNA-binding domain (DBD), a hinge region and a C-terminal ligand-binding domain (LBD). Upon androgens binding to the LBD, activation of AR-FL occurs. The androgen-bound AR-FL forms a homodimer and translocates into the nucleus, where it binds to androgen-response elements (AREs) and regulates canonical AR-target genes such as prostate specific antigen (PSA). As PCa progresses to castration-resistant prostate cancer (CRPC), a more aggressive form of PCa, it shifts from being androgen-dependent to becoming androgen-independent. The change occurs because the AR is no longer a full-length receptor, but rather a variant (ARV). The most common variant is ARV7, a truncated protein that has lost the LBD where the androgen binds. As a result, ARV7 is constitutively active and can enhance tumor growth, independent of androgens. At this point resistance to current drug therapies and androgen deprivation therapy (ADT) is reached by PCa and CRPC patients. Recent work has shown that resveratrol, a polyphenol with antioxidant properties, has anti-cancerous effects in PCa by inducing apoptosis and inhibiting cell proliferation. However, the mechanism by which RSV provides these effects is not exactly known. Some studies show that RSV decreases expression of AR mRNA and AR protein levels post-translationally. Identification of the mechanism by which RSV exerts its effects on CRPC cells is crucial as new lines of therapeutic treatments for prostrate cancer are needed, due to the relapse after ADT and resistance developed to current drugs by PCa and CRPC patients. We hypothesize that RSV exerts its anti-cancerous properties in CRPC cell lines via specific ubiquitin degradation of ARV7 at a post-translational level. The 22RV1 cell line is CRPC. Cells were treated with RSV at different concentrations. 22RV1 cells were treated with MG132, a protease inhibitor, used to inhibit specific-ubiquitin degradation of ARV7. RT-PCR, qPCR and Western Blot were all performed. There is a dose-dependent effect of RSV on ARV7 mRNA and protein levels in CRPC. The effects of the combination of RSV/MG132 treatment on ARV7 protein levels seem comparable to the control, meaning that RSV might indeed regulate ARV7 protein levels via the ubiquitin degradation pathway