Role of p21 activated kinase in Leukemogenesis

ABSTRACT During the previous funding cycle, our research focused on studies related to mechanism(s) of transformation by FLT3ITD and oncogenic KIT in myeloid leukemia’s including in AMLs and MPNs. We identified novel signaling pathways downstream from these oncogenes that function individually as well as in cooperation with mutations in epigenetic regulators such as TET2 and DNMT3A. The focus of this competitive renewal application involves a better understanding of the role of the PI3Kinase/c-Myc/GCN2 pathway as well as the p38α MAPK pathway in driving TET2 mediated clonal hematopoiesis (CH) in pre-leukemic cells and its cooperation with FLT3ITD driven frank AML. We recently provided experimental evidence supporting the notion that exposure of HSCPs with somatic TET2 (ten-eleven translocation 2, one of the most frequently mutated genes in individuals exhibiting CH) mutations to acute/chronic infection or hyperglycemia (HG), as noted in patients with diabetes and obesity, profoundly accelerates the development of CH and leukemia. We showed that this is in part due to enhanced production of inflammatory cytokines by mutant HSCPs, which in a feed-forward loop drive the survival, expansion and self-renewal of mutant HSCPs but induce apoptosis and differentiation in normal HSCPs. However, the signaling mechanism(s) downstream from these mutations in HSCPs, which contribute to their enhanced cellular competitiveness, are not known and the main focus of this proposal. Identifying these pathways would allow us to therapeutically target these mutant cells to mitigate their competitiveness thereby preventing or mitigating CH, development of leukemia and CVD. We performed an unbiased RNAseq analysis on WT and Tet2 KO HSCPs and identified several dysregulated signaling pathways in Tet2 KO HSCPs compared to WT. Here, we have focused our efforts on the PI3Kinase/c-Myc/GCN2 and the p38 MAPK pathway. We show that these pathways provide competitive advantage to Tet2 mutant HSCPs but not WT HSCPs. Inhibition of these pathways in Tet2 KO HSCPs, reverses and rescues, a significant number of cellular competitive advantages associated with these cells. We will define the role of these pathways in more detail. Furthermore, we will identify the mechanism(s) by which these pathways alter the function of downstream signals.