Aging-related hematopoietic stem cell intrinsic and microenvironmental signals in AML transformation

Summary Acute myeloid leukemia (AML) is a disease of the elderly that often transforms from pre-AML states of age- related clonal hematopoiesis (ARCH), myelodysplastic syndromes (MDS) or myeloproliferative neoplasms (MPN). Traditional models ascribe this association to the slow process of acquiring mutations over time. Work from our group suggests that functional declines in aging blood-forming hematopoietic stem cells (HSC) and signals from the aging niche that alter the transcriptional milieu or promote expansion of HSC compartments have an impactful role in myeloid disease progression by promoting clonal expansion of mutated (pre-leukemic) HSCs and emergence of AML. These two aspects, genetic drift and HSC extrinsic events, are typically studied separately. The goal of our program is to apply cutting edge genetic tools and single cell technology to integrate studies of clonal mutational evolution and niche components in patients and mouse models, to establish the mechanisms through which the aging marrow supports outgrowth of AML initiating clones. We have collected data that led us to hypothesize that inflammatory, transcriptional and stromal niche pressures mounting in the aging BM act on mutated pre-leukemic HSCs to promote their clonal outgrowth ultimately enabling AML development from pre-AML states. To address this hypothesis our goals are to: 1. Establish the role of transcriptional deregulation and environment-triggered inflammatory and stromal signals in AML transformation. We will examine whether AML transformation from ARCH, MDS, MPN results from clonal outgrowth of pre-leukemic HSCs through inflammation-induced activation of emergency myelopoiesis (EM) facilitating HSC expansion; MDM4-induced β-catenin, IL-1 signaling and P53 inactivation; and stromal cell - induced CNOT6L-mediated transcriptional deregulation in HSCs. Interactions among these pathways and their independent vs. collective contribution to disease progression will be examined. Data from shared patient samples and mouse models, single-cells analyses and functional screens will be integrated to identify targetable pathways elicited by novel facilitators of clonal outgrowth. 2. Map human AML evolution at the mutational and transcriptomic level and in the context of HSC intrinsic and niche factors using a patient sample cohort analyzed at the single cell level for mutational and transcriptional status to establish a trajectory of AML development in the context of aging and identify new regulatory nodes to target for clinical interventions.3: Characterize the molecular profile of HSC populations implementing clonal outgrowth in AML and determine how interactions between HSCs and specific niche populations affect transformation by deconvoluting shared transcriptional signatures among specific BM and niche cell populations that will provide new intervention paradigms. Our studies will deliver an integrated molecular and cellular characterization of aging-related mechanisms implicated in AML progression, paving the way for the development of specific therapeutic interventions aimed at curtailing AML transformation in patients with high risk ARCH, MDS and MPN.