Dihydrotestosterone (DHT), the principal driver of prostate cancer, is inactivated via reduction of its 3-keto group to a 3β-hydroxyl (3β-OH). 3β-Hydroxysteroid dehydrogenase type 1 (3β-HSD1), encoded by HSD3B1, catalyzes 3β-OH oxidation and is stabilized by an adrenal-permissive germline variant, thereby enhancing androgen biosynthesis. Here, we tested whether 3β-HSD1 maintains androgen receptor (AR) signaling by back-converting the inactive metabolite 3β-androstanediol (3β-diol) to DHT, and whether it similarly oxidizes the abiraterone metabolite 3β-OH-5α-abiraterone (3β-OH-5α-Abi) to 3-keto-5α-Abi, a weak AR agonist. Using HSD3B1-overexpression and knockout in vitro models, we quantified steroid interconversion by mass spectrometry and AR-responsive gene expression by qPCR and RNA sequencing following 3β-diol exposure. HSD3B1 overexpression efficiently enabled the conversion of 3β-diol to DHT and 3β-OH-5α-Abi to 3-keto-5α-Abi. In C4-2 prostate cancer cells, 3β-diol-derived DHT regeneration and subsequent AR gene induction were blocked by the 3β-HSD1 inhibitor trilostane or abolished by HSD3B1 knockout. Clinically, in chemotherapy-naïve metastatic castration-resistant prostate cancer (mCRPC) patients treated with abiraterone, apalutamide, and prednisone in the PANTHER trial, men harboring the adrenal-permissive HSD3B1 genotype showed significantly greater serum depletion of 3β-OH-5α-Abi. These findings demonstrate that 3β-HSD1-mediated steroid back-conversion can maintain intratumoral androgens, providing further mechanistic insight into the poor outcomes associated with the adrenal-permissive HSD3B1 genotype and highlighting 3β-HSD1 as a critical therapeutic target in prostate cancer. Implications: 3β-HSD1-mediated back-conversion of inactivated androgens (3β-diol→DHT) and abiraterone metabolites (3β-OH-5α-Abi→3-keto-5α-Abi) regenerates AR-active ligands, supporting sustained AR signaling and motivating 3β-HSD1 targeting and HSD3B1 genotype-informed treatment strategies in CRPC.
Molecular cancer research : MCR. 2026 Jul 28 [Epub ahead of print]
Masoud Bitaraf, Mohammad Alyamani, Nikou Fotouhi, Jinyuan Shi, Ziqi Zhu, Yoon-Mi Chung, Jennifer Freedman, Daniel J George, Nima Sharifi
Desai Sethi Urology Institute, University of Miami Miller School of Medicine, Miami, Florida Miami, FL United States., University of Miami Miami, FL United States., University of Miami Health System United States., Duke University Durham, NC United States.