Intratumoral androgen biosynthesis associated with 3 -hydroxysteroid dehydrogenase 1 promotes resistance to radiotherapy in prostate cancer

Half of all men with advanced prostate cancer (PCa) inherit at least 1 copy of an adrenal-permissive HSD3B7 (1245C) allele, which increases levels of 3 beta-hydroxysteroid dehydrogenase 1 (3 beta HSD1) and promotes intracellular androgen biosynthesis. Germline inheritance of the adrenally permissive allele confers worse outcomes in men with advanced PCa. We investigated whether HSD3B7 (1245C) drives resistance to combined androgen deprivation and radiotherapy. Adrenally permissive 3 beta HSD1 enhanced resistance to radiotherapy in PCa cell lines and xenograft models engineered to mimic the human adrenal/gonadal axis during androgen deprivation. The allele-specific effects on radiosensitivity were dependent on availability of DHEA, the substrate for 3 beta HSD1. In lines expressing the HSD3B7 (1245C) allele, enhanced expression of DNA damage response (DDR) genes and more rapid DNA double-strand break (DSB) resolution were observed. A correlation between androgen receptor (AR) expression and increased DDR gene expression was confirmed in 680 radical prostatectomy specimens. Treatment with the nonsteroidal antiandrogen enzalutamide reversed the resistant phenotype of HSD3B7 (1245C) PCa in vitro and in vivo. In conclusion, 3 beta HSD1 promotes prostate cancer resistance to combined androgen deprivation and radiotherapy by upregulating DNA DSB repair. This work supports prospective validation of early combined androgen blockade for high-risk men harboring the HSD3B7 (1245C) allele.