Abstract 3658: Brd4-bound enhancers drive critical sex differences in glioblastoma

Abstract

Sex can be an important determinant of cancer phenotype and exploring sex-specific tumor biology holds promise for identifying novel therapeutic targets and new approaches to cancer treatment. In an established model of glioblastoma, we discovered transcriptome-wide sexual dimorphism in gene-expression that was concordant with sex differences in H3K27ac marks, large Brd4-bound enhancer usage, and Brd4 co-localization with Myc and p53. The sex-specific enhancer usage drove sex differences in stem cell function and tumorigenicity. Moreover, male and female GBM cells exhibited opposing responses to pharmacological or genetic inhibition of Brd4. Brd4 knockdown or inhibition decreased male GBM cell clonogenicity and in vivo tumorigenesis, while increasing both in female GBM cells. These results were validated in male and female patient-derived GBM cell lines. Thus, for the first time, Brd4 activity is revealed to drive a sexually dimorphic stem cell and tumorigenic phenotype, resulting in diametrically opposite responses to BET inhibition in male and female glioblastoma cells. This has critical implications for the clinical evaluation and use of BET inhibitors. Citation Format: Najla Kfoury-Beaumont, Zongtai Qi, Michael Wilkinson, Lauren Broestl, Kristopher Berrett, Arnav Moudgil, Sumithra Sankararaman, Xuhua Chen, Jay Gertz, Robi Mitra, Joshua B. Rubin. Brd4-bound enhancers drive critical sex differences in glioblastoma [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3658.