Abstract SY05-01: Targeting chromatin adaptor proteins in cancer

Abstract Menin interacts with oncogenic fusion proteins produced by MLL1 rearrangements, and small molecules capable of disrupting these interactions are currently under investigation in clinical trials for the treatment of leukemia. Our research, which combines chromatin-focused and genome-wide CRISPR screenings with a range of genetic, pharmacological, and biochemical strategies in both mouse and human models, has led to the discovery of a molecular mechanism that acts as a switch between the MLL1-Menin and MLL3/4-UTX chromatin modifying complexes, influencing the efficacy of Menin-MLL inhibitors. We demonstrate that the MLL1-Menin complex plays a critical role in maintaining leukemia cell survival by preventing the MLL3/4-UTX complex from binding to certain gene promoters. Interruption of the Menin-MLL1 interaction results in the UTX-dependent transcriptional activation of a tumor suppressor gene program, which significantly influences therapeutic outcomes in both murine and human leukemia models. Notably, the therapeutic activation of this gene program through CDK4/6 inhibitors can overcome resistance in leukemia cells that do not respond to Menin inhibitors. The identification of this molecular switch between MLL1-Menin and MLL3/4-UTX complexes on chromatin highlights the complex roles of these evolutionarily conserved epigenetic regulators and underscores their importance in understanding and addressing the molecular mechanisms underlying response and resistance in leukemia treatment trials. Citation Format: Yadira Soto-Feliciano. Targeting chromatin adaptor proteins in cancer abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts) ; 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84 (7Suppl): Abstract nr SY05-01.