Abstract LB205: The IRF8-MEF2D transcription factor circuit regulated by a druggable multiple post-translational modification (PTM) reader ZMYND8 in acute myeloid leukemia

Abstract The transformed state in acute leukemia requires gene regulatory programs involving transcription factors (TFs) and chromatin modulators. Here, we uncover an IRF8-MEF2D TF regulatory circuit as an acute myeloid leukemia (AML)-specific dependency. We discover and characterize the mechanism by which the chromatin ‘reader' ZMYND8 directly activates IRF8 in parallel with the MYC proto-oncogene through their AML-specific enhancers. ZMYND8 is essential for AML proliferation in vitro and in vivo and associates with MYC and IRF8 enhancer elements that we define in cell lines and in patient samples. ZMYND8 occupancy at IRF8 and MYC enhancers requires BRD4, a transcriptional coactivator essential for AML proliferation. We show that ZMYND8 binds to the ET domain of BRD4 via its chromatin reader cassette, which in turn is required for proper chromatin occupancy and maintenance of leukemic growth in vivo. Our results rationalize ZMYND8 as a potential selective therapeutic target for modulating essential transcriptional programs in AML. Citation Format: Zhendong Cao, Krista A. Budinich, Hua Huang, Bin Lu, Zhen Zhang, Diqiu Ren, Yeqiao Zhou, Yuhan Huang, Bianca Pingul, Molly C. Kingsley, Alexandra K. Lenard, Jun Qi, Martin P. Carroll, Gerd A. Blobel, Robert B. Faryabi, Kathrin M. Bernt, Shelley L. Berger, Junwei Shi. The IRF8-MEF2D transcription factor circuit regulated by a druggable multiple post-translational modification (PTM) reader ZMYND8 in acute myeloid leukemia [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr LB205.