WASHINGTON, DC USA (UroToday.com) - Capsaicin is a compound found in the Capsicum species of plants and is a widely consumed food additive in areas with low prostate cancer incidence. Capsaicin is also used to treat chronic pain syndromes. These investigators presented the radiosensitizing capacity of capsaicin in prostate cancer cells in vitro. Radiosensitizing agents sensitize cells to the lethal effects of ionizing radiation (IR). This permits use of lower doses of radiation to achieve equivalent cancer control thereby minimizing adverse effects to normal tissues. Compounds occurring naturally in the diet make ideal potential radiosensitizing agents. The transient receptor potential vanilloid-receptor (TRPV)-1 and TRPV6 cation-selective channels are thought to be partly responsible for mediating the analgesic and anti-neoplastic effects. TRPV-1 and TRPV-6 expression is upregulated in prostate cancer tissue correlating directly with increasing tumor grade. This suggests TRPV1 and/or TRPV6 may be potential therapeutic targets for capsaicin-mediated interventions in prostate cancer patients. As IR and capsaicin both promote apoptosis and inhibit cell cycle progression in vitro, the researchers hypothesized that there would be an additive effect of combining these two therapies. They performed clonogenic assays to assess the effect of ionizing radiation (1-8 Gy) and/or capsaicin (1-10ìM) on colony formation rates in 4 human prostate cancer cell lines (LNCaP, PC3, PC3AR2, DU145). Proliferative, apoptotic, TRPV-6 protein markers were assessed using Western blot analyses.
Exposure of cells to capsaicin (1-10ìM) or IR (1-8Gy) caused significant dose-dependent inhibition of colony formation (p<0.001). Combining capsaicin with IR resulted in further significant inhibition of colony formation rates (P<0.001). LNCaP cells treated with capsaicin and/or IR had increased expression of pro-apoptotic proteins BAX and Bad, tumor-suppressor proteins p21 and p27 and reduced androgen receptor. Additionally, capsaicin monotherapy caused a dramatic alteration in TRPV1 and TRPV6 expression.
Presented by Laurence Klotz, et al. at the American Urological Association (AUA) Annual Meeting - May 14 - 19, 2011 - Walter E. Washington Convention Center, Washington, DC USA
Reported for UroToday by Christopher P. Evans, MD, FACS, Professor and Chairman, Department of Urology, University of California, Davis, School of Medicine.
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