PROJECT SUMMARY/ABSTRACT Acute Myeloid Leukemia (AML) is a lethal hematologic malignancy characterized by impaired myeloid differentiation and blast proliferation, inhibiting normal hematopoiesis. Isocitrate Dehydrogenase (IDH) mutations are highly prevalent in AML and contribute to leukemogenesis through production of oncometabolite 2HG. Mutant IDH inhibitors (Enasidenib for IDH2, Ivosidenib for IDH1) suppress 2HG production and differentiate leukemic cells to functional neutrophils. Despite initial excitement for differentiation agents, overall survival remains abysmal as differentiation therapy fails to induce durable responses in most patients. Concomitant oncogenic Nras mutations are the most consistent predictor of primary resistance to mutant IDH inhibitors. While IDH mutations cause stem cell bias, surprisingly, oncogenic Nras mutations are associated with aberrant myeloid differentiation. The role of oncogenic Nras in modulating IDH mutant AML leukemogenesis and the mechanism by which it contributes to therapeutic resistance is completely undefined. The goal of this research proposal is to define the mechanistic contribution of Nras to IDH mutant AML leukemogenesis and characterize its role in therapeutic resistance. There are no available mouse models that recapitulate patient phenotypes and provide dynamic range to study oncogenic Nras. We developed two orthogonal mouse models (genetically engineered mouse models and patient derived xenograft models) of IDH mutant AMLs with and without concomitant Nras. We will utilize serial IDHm AML patient samples to ensure translational relevance. Preliminary data indicates oncogenic Nras causes aberrant myeloid differentiation in IDH mutant AMLs, leads to rapidly lethal disease, and is not susceptible to Ivosidenib mediated differentiation. We show in vitro inhibition of Mek signaling promotes IDH/Nras co-mutant AML susceptibility to Ivosidenib. Aim1 proposes to characterize oncogenic Nras mediated changes in IDHm AML hematopoiesis (Aim1A) and leukemic cells of propagation (Aim1B). Aim2 evaluates the mechanism by which oncogenic Nras modulates response to Ivosidenib, characterizing how oncogenic Nras mitigates Ivosidenib mediated differentiation changes (Aim2A) and evaluating the role of Mek in attenuating Ivosidenib response (Aim2B). This work carefully considers the role of DNA and histone methylation and metabolism in these processes, utilizing metabolomics, bisulfite sequencing, and RNA-Seq. Completion of these aims will elucidate novel therapeutic targets for this high-risk AML sub-group and reveal how signaling environments influence a cell’s differentiation state response to therapy. This project is ideal for an aspiring physician-scientist, given its blend of clinical and basic biological questions. The work and training plan outlined will be completed in the laboratory of Dr. Ross Levine at Memorial Sloan Kettering, with a thesis committee of physician scientists, bioinformatic and metabo...