3239 – DETERMINING THE MECHANISM BY WHICH RUNX1 LOSS LEADS TO AN INFLAMMATORY RESPONSE IN HEMATOPOIETIC CELLS

Abstract

The transcription factor RUNX1 is often mutated in acute myeloid leukemia. Familial platelet disorder with associated myeloid malignancy (FPDMM) is caused by mutations in RUNX1 and is associated with an increased risk of leukemia. Many FPDMM patients have heightened inflammation. Inflammation can promote malignancies and understanding how RUNX1 mutations increase inflammation is critical for determining how to halt leukemia progression. We created a pan hematopoietic RUNX1 knockout (KO) mouse model and found that RUNX1 KO neutrophils overproduced cytokines in response to toll-like receptor 4 (TLR4) stimulation with lipopolysaccharide (LPS). The hyper-responsiveness of RUNX1 KO neutrophils correlated with increased expression of several genes encoding proteins in the TLR4 pathway. To determine if RUNX1 regulates TLR4 signaling in neutrophils, we deleted RUNX1 specifically in neutrophils. Unexpectedly, RUNX1 deletion did not cause an inflammatory phenotype, indicating that alterations in the TLR4 signaling pathway are established in a neutrophil precursor. Single cell transcriptomic data suggests that RUNX1 deficiency dysregulates TLR4 signaling in a precursor of neutrophils, specifically the granulocyte-monocyte progenitor (GMP) population. We determined that RUNX1 loss in GMPs was sufficient to establish the inflammatory phenotype in neutrophils. We performed ATAC-seq and found that RUNX1 loss led to chromatin opening at key TLR signaling genes. We determined that the inflammatory phenotype driven by the IRF and STAT family of transcription factors. Together this data suggests that the dysregulated inflammatory response of neutrophils is a downstream consequence of RUNX1 deletion in GMPs and can be dampened by inhibiting either the TLR4 or JAK/STAT signaling pathways. The transcription factor RUNX1 is often mutated in acute myeloid leukemia. Familial platelet disorder with associated myeloid malignancy (FPDMM) is caused by mutations in RUNX1 and is associated with an increased risk of leukemia. Many FPDMM patients have heightened inflammation. Inflammation can promote malignancies and understanding how RUNX1 mutations increase inflammation is critical for determining how to halt leukemia progression. We created a pan hematopoietic RUNX1 knockout (KO) mouse model and found that RUNX1 KO neutrophils overproduced cytokines in response to toll-like receptor 4 (TLR4) stimulation with lipopolysaccharide (LPS). The hyper-responsiveness of RUNX1 KO neutrophils correlated with increased expression of several genes encoding proteins in the TLR4 pathway. To determine if RUNX1 regulates TLR4 signaling in neutrophils, we deleted RUNX1 specifically in neutrophils. Unexpectedly, RUNX1 deletion did not cause an inflammatory phenotype, indicating that alterations in the TLR4 signaling pathway are established in a neutrophil precursor. Single cell transcriptomic data suggests that RUNX1 deficiency dysregulates TLR4 signaling in a precursor of neutrophils, specifically the granulocyte-monocyte progenitor (GMP) population. We determined that RUNX1 loss in GMPs was sufficient to establish the inflammatory phenotype in neutrophils. We performed ATAC-seq and found that RUNX1 loss led to chromatin opening at key TLR signaling genes. We determined that the inflammatory phenotype driven by the IRF and STAT family of transcription factors. Together this data suggests that the dysregulated inflammatory response of neutrophils is a downstream consequence of RUNX1 deletion in GMPs and can be dampened by inhibiting either the TLR4 or JAK/STAT signaling pathways.