Abstract 456: ERG regulation of intracrine androgen production and castration-resistant prostate cancer progression

Abstract

Abstract Introduction and Objective: Intratumoral androgen synthesis in prostate cancer (PC) contributes to the development of castration-resistant prostate cancer (CRPC). Several enzymes responsible for androgen biosynthesis have been shown to be overexpressed in CRPC, thus, contributing to CRPC in a castrated environment. However, little is known regarding their mode of regulation and expression in this context. The TMPRSS2-ERG transcription factor has been shown to be present in primary PC tumors as well as CRPC tumors; however, its biological function contributing to the development CRPC in the context of intratumoral androgen synthesis is not known. We hypothesize that TMPRSS2-ERG fusions regulate androgen biosynthetic enzyme (ABE) gene expression and the production of androgens, which contributes to the development of CRPC. Methods: We used a variety of methods including lentiviral knockdown and overexpression of ERG, qPCR, Western blot, ChIP-PCR, and Mass Spectrometry. Results: We found that (a) shRNA knockdown of ERG in VCaP PC cells significantly reduces the expression of ABE's AKR1C3, HSD17B6, and HSD17B4; (b) overexpression of truncated ERG or wild-type ERG in LNCaP PC cells significantly increases the expression of AKR1C3 and HSD17B6; (c) ERG binds to the AKR1C3 gene in VCaP PC cells; and (d) DHT synthesis is reduced in VCaP shERG cells treated with 5α-Androstanedione, a DHT precursor metabolite, compared to VCaP shScrambled controls. Conclusions: These data suggest that AKR1C3 catalyzes the biochemical reduction of 5α-Androstanedione to DHT in PC cells, and that ERG may regulate this step through upregulation of AKR1C3 expression. Elucidation of ERG regulation of ABEs in CRPC may help to stratify TMPRSS2-ERG fusion-positive PC patients in the clinic for anti-hormone driven therapies. Additionally, not all PC tumors express CYP17A1 enzyme, therefore this study emphasizes the importance of investigating ABEs other than CYP17A1, such as AKR1C3 and HSD17B6. In summary, this study addresses alternative ABE drug targets as well as possible drug resistance modes in PC treatment. Citation Format: Katelyn A. Powell, Louie Semaan, Krishna R. Maddipati, Katie (Mary) Conley-Lacomb, Yanfeng Li, Michael Cher, Sreenivasa R. Chinni. ERG regulation of intracrine androgen production and castration-resistant prostate cancer progression. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 456. doi:10.1158/1538-7445.AM2014-456