Comprehensive Molecular and Functional Analysis of NUTM1-Rearranged Leukemia [leukemia-RNA-seq]

NUTM1-rearrangement (NUTM1-r) represents a significant subset of infant B-ALL, particularly prevalent in cases lacking KMT2A-rearrangements (KMT2A-r). However, the underlying molecular mechanisms for the characteristic leukemia have not been fully elucidated. Our comprehensive analysis reveals that NUTM1-r infant leukemia is characterized by a unique transcriptomic and epigenetic landscape with global hypomethylation, delineating a discrete leukemia entity. Functional interrogation of the BRD9-NUTM1 fusion demonstrates its dual role in promoting B-lineage commitment while conferring leukemic stem cell properties. Strikingly, single transduction of BRD9-NUTM1 is sufficient to induce serially-transplantable pro-B-like leukemia in vivo, recapitulating key features of human NUTM1-r B-ALL, including NUTM1 overexpression, skewed B cell transcriptional programs, and low CD34 expression. Mechanistically, BRD9-NUTM1 expression gives rise to distinctive open chromatin regions with global enhancement of H3K27Ac, particularly at loci associated with Myc, NF-κB, and posterior Hoxa genes. Notably, BRD9-NUTM1 leukemic cells responded robustly to cytarabine, in contrast to the relative resistance observed in KMT2A-r leukemias. Interestingly, our findings highlight a discrepancy observed in the clinical behavior of NUTM1-r leukemias, where the transformed cells display characteristics of stemness, yet tend to lose these properties under chemotherapy due to the dependence on active transcription. Our findings delineate the unique molecular profile of NUTM1-r leukemias, suggesting opportunities for targeted therapies that exploit these specific vulnerabilities.