Co-targeting BET Bromodomain Proteins and Aberrant Signaling in AML.

PROJECT SUMMARY Acute myeloid leukemia (AML) comprises 20% of childhood leukemia cases. In contrast to acute lymphoblastic leukemia (ALL), cure rates for AML remain poor with the majority of patients dying from refractory leukemia or treatment related toxicities. In contrast to AML in older adults, genome-wide studies of AML in children, adolescents, and young adults (AYA) revealed a lower mutational burden and highly prevalent transcription factor fusions and RAS pathway mutations. Additionally, while transcription factor fusions are hypothesized to promote a transcriptional signature that is permissive for AML development, experimental data suggest that signaling mutations play a central role in driving leukemic growth in vivo. Thus, simultaneously targeting the abnormal transcriptional program and aberrant signaling pathways in AML is a rational therapeutic approach that is particularly relevant in children and AYA patients. The overall goals of this proposal are to investigate the efficacy of promising drug combinations that simultaneously target key pathways in pediatric AML and to elucidate molecular mechanisms underlying drug synergy and resistance to these targeted approaches through the following specific aims: (1) to identify and validate mechanisms of drug synergy and resistance to BET + MEK inhibition; and, (2) to investigate the in vivo efficacy of this combination in patient derived xenograft (PDX) models of pediatric AML.