Abstract 3030: HSD3B1 mediated anti-androgen resistance in prostate cancer requires specific androgen precursors

Abstract

Abstract Resistance to anti-androgens, such as enzalutamide (Enza) or abiraterone (Abi), develops within 24 months of initial exposure in most prostate cancer (PCa) patients. Commonly, dysregulated androgen signaling is a key feature of resistant disease. Previous studies demonstrate that androgen synthesis is upregulated in Enza and Abi resistance. HSD3B1 is steroidogenic enzyme which contributes to androgen synthesis and is associated with PCa progression. This study aims to determine the role of HSD3B1 in promoting Enza and Abi resistance in PCa. Enza resistant (C4-2B MDVR) and Abi resistant (C4-2B AbiR) C4-2B PCa cells were generated by chronically exposing parental C4-2B cells to increasing Enza or Abi concentrations for >12 months. Cells were maintained in 20 µM Enza or 10 µM Abi thereafter. Microarray, RNA-seq, and rtPCR were used to determine differences in gene expression between parental and anti-androgen resistant cells and confirmed by Western blot. HSD3B1 expression was knocked down in C4-2B MDVR and C4-2B AbiR cells using shRNA and cell number was determined in media containing FBS, charcoal dextran stripped FBS (CDFBS), or CDFBS supplemented with 100 nM pregnenolone (P5), 100 nM DHEA, or 10 nM DHT in the presence and absence of 20 µM Enza or 10 µM Abi. PSA secretion was determined by ELISA and PSA-luciferase activity was measured by reporter assay. C4-2B MDVR and C4-2B AbiR cells have increased HSD3B1 expression compared to parental C4-2B cells. This correlates to an increase in intracrine androgens in C4-2B MDVR cells as determined by LC-MS. Knockdown of HSD3B1 in C4-2B MDVR resensitized cells to Enza in FBS, CDFBS+DHT and CDFBS+P5 conditions as determined by a reduction in cell number and PSA secretion and/or PSA-luciferase activity in response to Enza. In the C4-2B AbiR cells, inhibition of HSD3B1 re-sensitized cells to treatment with Abi in FBS, CDFBS, and CDFBS+P5 conditions with the greatest effects seen in the FBS and CDFBS+P5 conditions. Supplementation with P5, but not DHEA, was able to induce PSA-luciferase activity and cell growth in C4-2B MDVR and C4-2B AbiR cells and this could be blocked by knockdown of HSD3B1. HSD3B1 overexpression in C4-2B MDVR and C4-2B AbiR cells contributes to Enza and Abi resistance and targeting this enzyme could be a viable strategy to improve anti-androgen response in PCa cells. HSD3B1 activity is reliant on select androgen precursors, such as pregnenolone, indicating preference towards a specific androgen synthesis pathway by HSD3B1 in mediating anti-androgen resistance. Citation Format: Cameron M. Armstrong, Chengfei Liu, Wei Lou, Alan P. Lombard, Christopher Evans, Allen C. Gao. HSD3B1 mediated anti-androgen resistance in prostate cancer requires specific androgen precursors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3030.