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BackgroundHuman 3β-hydroxysteroid dehydrogenase type 1 (HSD3B1) plays a vital role in steroidogenesis in breast tumors and may therefore be a suitable target for treatment of breast cancer. This study investigated the role of HSD3B1 in the pathogenesis of breast cancer in clinical and experimental settings.MethodsExpression of HSD3B1 in primary tumors of 258 breast cancer patients was evaluated by immunohistochemistry. Screening of breast cancer cell lines indicated that triple-negative MDA-MB-231 cells expressed HSD3B1. The effects from genetic and pharmacologic inhibition of HSD3B1 were assessed in vitro and in vivo.ResultsThe findings showed that 44% of the 258 breast cancers were HSD3B1-positive. The HSD3B1-positivity was associated with advanced-stage disease (p = 0.009) and reduced recurrence-free survival (p = 0.048) but not with tumor subtype or estrogen receptor status. Silencing of HSD3B1 or treatment with an HSD3B1 inhibitor (trilostane) reduced colony formation in breast cancer cells. Knockdown of HSD3B1 inhibited cell proliferation and migration. Analysis of a murine xenograft tumor model indicated that trilostane significantly slowed tumor growth.ConclusionsExpression of HSD3B1 in breast cancer is negatively associated with prognosis. The study found HSD3B1 to be a potential therapeutic target for breast cancer independent of estrogen receptor status.