Abstract 2082: Extragonadal and regional androgen biosynthesis associated with a common steroidogenic enzyme polymorphism promotes radioresistance in prostate cancer

Purpose: Androgen deprivation therapy (ADT) is the linchpin therapeutic for locally advanced and metastatic PCa. However, resistance to ADT is common and has been associated with a gain of function mutation (A1245C) in the 3β-HSD enzyme, which catalyzes intratumoral DHT synthesis. As androgen signaling is known to upregulate the DNA damage response (DDR), we investigated whether variant HSD3B1 modulates DDR and radiosensitivity in PCa via extragonadal androgen biosynthesis. Methods: We stably knocked down HSD3B1 in LNCaP, C42 and VCaP cell lines (which carry the protein stabilizing variant allele), and overexpressed the variant HSD3B1 allele in LAPC4 (that harbors WT allele, where the protein readily undergoes degradation). We examined the proliferative and clonogenic capacity of these cells in presence and absence of substrate, the extragonadal androgen precursors DHEA, followed by treatment with IR (200,400, 600 and 800 cGy, single fraction). We studied DNA DSB formation and resolution kinetics using phospho- γH2AX labelling and neutral COMET assay. We also measured 3β-HSD dependent changes in expression of DDR response genes pre- and post-radiation Results: Control shRNA transduced prostate cancer cell lines expressing the variant HSD3B1 allele had increased cell proliferation (3.1289-fold, p