Abstract 647: Association between adrenal-restrictive HSD3B1 inheritance and hormone independent subtypes of endometrial and breast cancer

Abstract Breast and endometrial cancer are both malignancies that can be classified into subtypes based on their hormone dependence, such as estrogen receptor (ER)-positive vs. ER-negative breast cancer and low-grade vs. high-grade endometrial cancer. The gene HSD3B1 encodes the steroid metabolism enzyme 3β-hydroxysteroid dehydrogenase 1, which catalyzes a critical step in conversion of adrenal precursor steroids to potent androgens and estrogens. Associations between the missense-encoding germline variant rs1047303 in HSD3B1 have been described to affect outcomes of castration-resistant prostate cancer and associated with ER positivity in postmenopausal breast cancer. The adrenal-permissive 1245C allele enables greater production of androgens and estrogens from adrenal precursors, whereas the adrenal-restrictive 1245A allele limits this reaction pathway. Using data from The Cancer Genome Atlas’s TCGA-UCEC and TCGA-BRCA projects, we interrogated whether the adrenal-restrictive rs1047303 genotype was associated with less hormone-driven genomic clusters of endometrial and breast cancer. We determined the genotype frequencies for different tumor subtypes, as classified by the genomic analysis of Sanchez-Vega, et al. (2018). The adrenal-restrictive HSD3B1(1245A) allele was associated with the copy number (CN) high cluster of endometrial cancer (OR 1.59, 95% CI 1.12-2.26, p = 0.0098), notably composed of serous and high-grade endometrioid endometrial cancers which are less estrogen-dependent than low-grade endometrioid tumors. Similarly, the adrenal-restrictive HSD3B1(1245A) was associated with the basal subtype of breast cancer (OR 1.54 [1.13-2.09], p = 0.0057), a subtype that is largely ER-negative and is known to share genomic features with serous-type endometrial cancers. Lastly, we interrogated overall survival of endometrial cancer patients in the UK Biobank and found that patients homozygous for the adrenal-restrictive HSD3B1(1245A) had worse overall survival (HR 1.39 [1.16-1.68], p = 0.00049) and cancer-specific survival (HR 1.39 [1.14-1.70], p = 0.0013), a finding consistent with the A allele being enriched in the more aggressive CN-high subtype of endometrial cancer. Taken together, these findings suggest a role for adrenal-restrictive vs. adrenal-permissive steroidogenesis, by way of rs1047303 genotype, in the development of and/or outcomes from at least three different commonly hormone-associated types of cancer: prostate, breast, and endometrial. Citation Format: Jeffrey M. McManus, Roberto Vargas, Peter Bazeley, Navin Sabharwal, Nima Sharifi. Association between adrenal-restrictive HSD3B1 inheritance and hormone independent subtypes of endometrial and breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 647.