Vulnerability of <i>SRSF2</i> -mutated chronic myelomonocytic leukemia to perturbation of the cGAS-STING pathway

Chronic myelomonocytic leukemia (CMML) is characterized by monocytosis in blood and bone marrow and natural progression to acute myeloid leukemia (AML) in ≤30% of patients. The mutation landscape of CMML has been reported, and animal models that recapitulate its clinicopathologic features and progression are needed. We report a CMML zebrafish model based on transgenic SRSF2P95H expression that closely resembled the human disease. Hematological assessment of the transgenic animals showed myelodysplasia, monocytosis, and leukemia transformation. Transcriptomic analysis confirmed global splicing alterations and identified inflammatory phenotypes associated with activation of the cyclic GMP-AMP synthase-stimulator of interferon genes (cGAS-STING) pathway. DNA damage, R-loop formation, and double-strand DNA accumulation were evident. Inhibition of R-loop formation or cGAS-STING axis significantly reduced gene expression associated with inflammation and immune activation and mitigated the leukemia phenotype. The inflammatory effects and their response to treatment were recapitulated in human hematopoietic stem and progenitor cells. Collectively, our findings show a pathogenetic link between SRSF2P95H and cGAS-STING activation in CMML and its vulnerability to therapeutic intervention.