Orthogonal proteogenomic approaches identify the druggable PA2G4-MYC axis in 3q26 AML

Selective and pan-histone deacetylase inhibitors (HDACis) emerged at the intersection of these approaches. HDACis suppress EVI1 expression and preferentially impair leukemia proliferation in 3q26 AML compared to other leukemia subtypes in multiple preclinical models. To understand this mechanism of action, we dissected the expression dynamics of the bone marrow leukemia cells of patients treated with hit list compounds, reconstituted with the chromatin-associated co-transcriptional complex of EVI1 by rapid immunoprecipitation mass spectrometry (RIME) in human 3q26 AML models; we focused on the role of the proliferation-associated 2G4 (PA2G4) protein. We demonstrated that genetic and HDACi-mediated suppression of EVI1 modulates MYC and that PA2G4 overexpression rescues AML cells from the inhibitory effects of HDACis. Genetic and small molecule inhibition of PA2G4 abrogated EVI1 and, consequently, MYC in 3q26 AML models, including in patient-derived leukemia xenografts. In conclusion, our work positions PA2G4 at the crosstalk of the EVI1 leukemogenic signal for developing new therapeutics and, at this time, urges the use of upfront HDACi-based combination therapies in patients with 3q26 AML. Overall design: In this work, we challenged the ecotropic viral integration site-1 gene (EVI1/MECOM), the most lethal oncogenic TF in AML carrying chromosome 3q26 abnormalities, by crossing cell-based screens, gene expression tools, and mass spectrometry–based approaches to identify modulators of EVI1.