Human Cancer Biology Interleukin-6 Regulates Androgen Synthesis in Prostate Cancer Cells

Purpose: 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 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 androgen receptor activation and growth and differentiation in prostate cancer. In this study, we investigate whether IL-6 regulates intraprostatic androgen synthesis in prostate cancer cells. Experimental Design: Quantitative reverse transcription-PCR and Western blotting were done 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 small interfering RNA specific to IL-6 receptor and gp130, and the effect on AKR1C3 expression was examined. Intraprostatic androgen levels in prostate cancer cells in culture and in tumors were measured by an enzyme immunoassay (Testosterone EIA kit). 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 small interfering RNA 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. The growth of prostate epithelial cells requires physiologic levels of androgen to both stimulate proliferation and inhibit apoptotic death (1). Because the growth of prostate cancer cells depends on the presence of androgens, almost all patients with advanced prostate cancer respond initially to androgen deprivation and antiandrogen therapy. However, virtually every patient will relapse due to the growth of androgen-independent or castration-resistant cancer cells. Although serum testosterone concentrations are significantly reduced after androgen deprivation therapy, levels of intraprostatic androgens are reproducibly measured to be at concentrations sufficient to activate the androgen receptor (AR) and stimulate tumor growth (2–9). Accumulating evidence suggests that prostate cancer cells may survive androgen deprivation therapies by increasing intracrine androgen synthesis within the prostate. Intraprostatic androgens can be synthesized de novo from cholesterol or other ubiquitous molecular precursors such as dehydroepiandrosterone mediated by genes encoding many steroidogenic enzymes, including AKR1C3, HSD3B2, SRD5A1, CYP17A1, CYP19A1, and UBT2B15. AKR1C3 (also known as 17βHSD5) converts androstenedione to testosterone in the prostate. HSD3B2 converts dehydroepiandrosterone to androstenedione, a substrate for conversion to testosterone. SRD5A1 converts testosterone to the more potent androgen dihydrotestosterone Authors' Affiliations: Department of Urology, Graduate Program of Pharmacology and Toxicology, and Department of Biological Chemistry, and Cancer Center, University of California at Davis, Sacramento, California Received 3/16/09; revised 4/21/09; accepted 4/23/09; published OnlineFirst 7/28/09. Grant support: NIH grants CA118887 and CA109441. The costs of publication of this article were defrayed in part by the payment of page charges. This articlemust therefore be herebymarked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. Requests for reprints: Allen C. Gao, Department of Urology, University of California at Davis Medical Center, 4645 2nd Avenue, Research III, Suite 1300, Sacramento, CA 95817. Phone: 916-734-8718; Fax: 916-734-8714; E-mail: [email protected]. F 2009 American Association for Cancer Research. doi:10.1158/1078-0432.CCR-09-0640 4815 Clin Cancer Res 2009;15(15) August 1, 2009 www.aacrjournals.org Research. on April 15, 2017. © 2009 American Association for Cancer clincancerres.aacrjournals.org Downloaded from Published OnlineFirst July 28, 2009; DOI: 10.1158/1078-0432.CCR-09-0640