FLT3-ITD mutation expands dendritic cells and alters CD4+ T cells in acute myeloid leukemia

Fms-like tyrosine kinase 3 (FLT3) is a critical receptor for functional dendritic cell (DC) development. Mutations associated with FLT3 are commonly observed in acute myeloid leukemia (AML) patients. Internal tandem duplication (FLT3-ITD) results in ligand-independent constitutive signaling and promotes tumor survival. Basic characterization of dendritic cells in the context of AML is lacking, therefore we investigated how FLT3-ITD impacts DC homeostasis and what downstream affects on the immune system may be. During AML we found that patient bone marrow DC homesostasis is disrupted and in a mouse model of AML we found that T-bet- cDC2s are increased in vivo and both Treg and Th17 cells are increased. In vitro co-cultures of AML DCs and naive OT-II cells results in more Th17 phenotype by IL-17A secretion. We propose that in FLT3-ITD+ AML DC homeostasis is dysregulated and Th17 cells are increased as a result. Overall design: Spleens from aged matched (36 weeks) AML mice and healthy WT mice were processed for ADT and sc-RNAseq (3' GEX using 10X Genomics Chromium Platform).