Menin-MLL inhibitors enhance JUND activity in MLLr leukemic cells, contributing to tumorigenesis and therapy resistance

Abstract Mixed lineage leukemia (MLL)-rearranged (MLLr) acute myeloid leukemia (AML) and acute lymphoid leukemia involve reciprocal translocations of the KMT2A (MLL1) gene with various translocation partner genes, yielding oncogenic chimeric MLL1 fusion proteins (MLL-FPs). Menin, the protein product of the MEN1 gene, is essential for the leukemogenic activity of MLL-FPs. Revumenib is a small-molecule inhibitor that selectively disrupts the menin-MLL interaction, and it is now in clinical use for treatment of MLLr and NPM1-mutated acute leukemia. Notably, menin also interacts with the JUND, a member of the activator protein 1 transcription factor family, through a conserved protein sequence in the MLL1/2 binding pocket of menin. Despite this structural similarity, the impact of menin-MLL inhibitors on JUND function has remained unexplored. In this study, we investigated the influence of menin-MLL inhibitors on JUND activity. Quantitative mass spectrometry analysis of MLLr leukemic cells demonstrated that menin-MLL inhibitors also disrupt menin-JUND interactions. Furthermore, CRISPR-mediated inactivation of JUND or pharmacologic inhibition using c-Jun N-terminal kinase inhibitors synergistically enhanced the antileukemic effects of menin-MLL inhibitors, leading to reduced cell proliferation, cell cycle arrest, and apoptosis. RNA sequencing and chromatin-binding assays revealed that menin-MLL inhibitor treatment increased JUND chromatin occupancy, leading to the upregulation of target genes and contributing to resistance against menin-MLL inhibitors. Immunocompromised mice engrafted with JUND-deficient leukemia cells exhibited reduced tumor burden compared with control mice engrafted with wild-type leukemic cells. These findings reveal a role for JUND in MLLr-AML and suggest that targeting JUND transcription factor activity may enhance the efficacy of menin-MLL inhibitors toward MLLr leukemic cells.