MP66-10 CHARACTERIZATION OF SUSCEPTIBILITY LOCI IN HEREDITARY PROSTATE CANCER FAMILIES USING COPY NUMBER VARIATION AND LINKAGE ANALYSIS

Abstract

INTRODUCTION AND OBJECTIVES: The intratumoral androgen synthesis is one of the mechanisms by which androgen receptor (AR) is aberrantly re-activated in castration-resistant prostate cancer (CRPC) after androgen ablation. However, pathways controlling steroidogenic enzyme expression and de novo androgen synthesis in prostate cancer (PCa) cells are largely unknown. In this study, we explored the potential roles of DAB2IP/AKR1C3 signaling in androgen synthesis and castration-resistant progression of PCa. METHODS: Tumor growth of two PCa cells (androgenindependent C4-2 and androgen-dependent LAPC-4) with or without DAB2IP expression was compared under castrated condition by MTT assay and subcutaneous xenograft model. Expression levels of steroidogenic enzymes were measured by real-time RT-PCR. Regulation of AKR1C3 expression by DAB2IP, subsequent alteration of AR activity and prostate-specific antigen (PSA) re-expression were examined by luciferase reporter assays or western blotting. Intracrine levels of androgens were measured by EIA in PCa cells, xenografts or castrated DAB2IP-/mice prostate tissues. The correlation between DAB2IP and AKR1C3 expression in PCa xenografts, DAB2IP-/mice prostate and human PCa tissues were examined by immunohistochemical (IHC) staining or western blotting. RESULTS: DAB2IP loss could potentiate the castration-resistant tumor growth of PCa cells in vitro and in vivo, and reprogram the expression profiles of steroidogenic enzymes, such as AKR1C3, CYP17A1, 17BHSD2, 17BHSD3, AKR1C1/2 and UGT2B17. Furthermore, DAB2IP coulddramatically inhibit thepromoter activity ofAKR1C3andsuppress its expression. Consistently, the levels of total testosteronewere significantly higher in DAB2IP-deficient PCa cells, xenografts or DAB2IP-/mice prostate tissues, in which more AR phosphorylation or nuclear staining and higher PSA expression were observed. Moreover, knockdown of AKR1C3 using shRNA could abolish all of these phenomena. In addition, DAB2IP expression inversely correlated with AKR1C3 in PCa xenografts, DAB2IP-/mice prostate and human PCa tissues. CONCLUSIONS: Loss of DAB2IP in PCa cells enhances AKR1C3 expression and de novo androgen synthesis, which may contribute to the development of CPRC.