Abstract 1727: Interleukin-6 and intracrine androgens in prostate cancer cells

Abstract

Abstract INTRODUCTION AND OBJECTIVES: The standard systemic treatment for prostate cancer patients is androgen deprivation therapy. Although serum testosterone concentrations were significantly reduced after androgen deprivation therapy, levels of intraprostatic androgens are reproducibly measured at concentrations sufficient to activate androgen receptor (AR) and stimulate tumor growth, suggesting that prostate cancer cells may survive androgen deprivation therapies by increasing intracrine androgen synthesis within the prostate. However, factors that regulate de novo intracrine androgen synthesis have not been identified. Interleukin-6 (IL-6) has been implicated in the modulation of AR activation and growth and differentiation in prostate cancer. In this study, we investigate whether IL-6 regulates intraprostatic androgen synthesis in prostate cancer cells. METHODS: Quantitative reverse transcription-PCR and western blot were performed to detect expression levels of steroidogenic enzymes. AKR1C3 promoter reporter was constructed and analyzed for IL-6-mediated AKR1C3 transcriptional activity. IL-6-mediated signaling was knocked down using siRNAs specific to IL-6R and gp130 and the effect on AKR1C3 expression was examined. To measure intraprostatic androgen levels, IL-6 overexpressing LNCaP-IL6+ cells were inoculated orthotopically into the prostate of castrated male nude mice and generated tumors. Intraprostatic androgen levels were measured by an enzyme immunoassay (Testosterone EIA kit) based on the competition between testosterone and a testosterone-acetylcholinesterase (AChE) conjugate (testosterone tracer) for a limited amount of testosterone in the sample. RESULTS: We found that IL-6 increases the expression of genes encoding many steroidogenic enzymes including HSD3B2 and AKR1C3 involved in androgen biosynthesis. Down regulation of IL-6 receptor and gp130 expression using specific siRNA abolished IL-6 mediated AKR1C3 expression, suggesting that IL-6 signaling is responsible for AKR1C3 expression. IL-6 increases AKR1C3 promoter activity, indicating that the increase in IL-6-mediated AKR1C3 expression is in part at the transcriptional level. Treatment of IL-6 increased testosterone level in LNCaP cells. The tumor testosterone levels were detected at 378 pg/g in tumors generated from IL-6 overexpressing LNCaP-IL6+ cells inoculated orthotopically into the prostates of castrated male nude mice. CONCLUSIONS: These results suggest that IL-6 increases levels of intracrine androgens through enhanced expression of genes mediating androgen metabolism in prostate cancer cells during androgen deprivation therapy. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 1727.