Epigenetic reader ZMYND8 bridges BRD4 and hypoxia-inducible factors to mediate breast cancer progression and metastasis

Metastatic breast cancer has high rates of relapse and mortality. The absence of definitive prognostic biomarker and effective therapeutic target is the major obstacle to end this aggressive disease. Epigenetic dysregulation plays a crucial role in breast cancer metastasis. However, the mechanism by which epigenetic dysregulation stimulates the hypoxia-mediated breast cancer progression and metastasis remains unknown. Based on luciferase reporter assays and analysis of expression changes of 720 epigenetic genes in three microarray datasets, we identified epigenetic reader ZMYND8 as a novel hypoxia-inducible factor (HIF) target gene. Human breast cancer tissue microarray data indicated that ZMYND8 is highly expressed in invasive breast tumors and this overexpression is significantly correlated with poor clinical outcomes in patients with breast cancer. ZMYND8 depletion dramatically attenuates the tumorigenic potential of breast cancer cells in colony formation, migration and invasion in vitro, and suppresses breast tumor growth and metastasis in mice. To elucidate the underlying mechanism, we performed co-immunoprecipitation, chromatin immunoprecipitation and quantitative PCR assays and found that ZMYND8 interacts with HIF complex and acetyl lysine 16 of histone H3 at the hypoxia inducible elements (HREs) to provoke the expression of HIF target genes LOX, AGR2, AQP1 and VEGFA. ZMYND8 controls breast cancer growth and metastasis through HIF in mice. We further found that p300 binds and acetylates ZMYND8 in breast cancer cells. Acetylated ZMYND8 interacts with and recruits BRD4 to the HREs to stimulate RNA polymerase II phosphorylation, thereby promoting transcriptional elongation of HIF target genes. ZMYND8 acetylation is necessary and sufficient for breast tumor growth and metastasis in vitro and in mice. Together, p300-ZMYND8-BRD4-HIF axis is critical for breast cancer progression and metastasis. In summary, ZMYND8 represents a positive feedback mechanism that amplifies HIF-mediated breast cancer progression and metastasis, and provides a potential epigenetic target for the prognosis and treatment of breast cancer. Citation Format: Yan Chen, Bo Zhang, Lei Bao, Lai Jin, Mingming Yang, Yan Peng, Jennifer Wang, Chenliang Wang, Xuan Zou, Yingfei Wang, Weibo Luo. Epigenetic reader ZMYND8 bridges BRD4 and hypoxia-inducible factors to mediate breast cancer progression and metastasis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 82.