EPI_T-ALL

BACKGROUND: T-cell acute lymphoblastic leukemia (T-ALL) is a malignancy with refractory/relapsed cases, due to the ineffective targeting of leukemia initiating cells (LICs). Over 50% of patients harbour DNA mutations, leading to the hyperactivation of Notch signalling. Moreover, loss-of-function mutations have been identified in genes encoding epigenetic modifiers that may be relevant for T-ALL development and progression. Interestingly, we reported that NOTCH1-induced T-cell leukemias generated from mouse hematopoietic stem/progenitor cells (HSPCs) with different expression levels of the histone-methyltransferase EZH2, diverged dramatically in LIC activity, suggesting that the loss of distinct epigenetic modifiers, such as EZH2 may support the maintenance and progression of T-ALL.

HYPOTHESIS: This proposal aims to characterize the functional role of loss of distinct epigenetic modifiers in the NOTCH1-driven malignant transformation of human hematopoietic cells and T-ALL pathogenesis. We hypothesize that the activity of unique chromatin modifiers, such as EZH2, modulates functional pathways of human T-cell transformation and leukemia progression that may underlie the different clinical outcomes of relapsed/recurrent T-cell leukemias.

SPECIFIC AIMS: 1) To understand cancer initiation and progression by characterization of the epigenetic landscape; 2) To study the potential use of epigenetic modulators to overcome resistance to anti-cancer therapies.

STUDY DESIGN: We will employ a novel model of human T-ALL in which HSPCs, derived from different tissues including cord blood are transformed into clonal T-ALL-like malignant cells. Specifically, HSPCs will be transduced with lentiviral vectors encoding NOTCH1-dE (a constitutively active NOTCH1 variant) alone or in combination with known T-ALL oncogenes, and subsequently injected into immunocompromised mice. We will evaluate the contribution of distinct epigenetic modifiers in which loss-of function mutations have been previously identified in T-ALL patients, to leukemogenesis and LIC-related phenotypes using gain/loss-of-function assays. Multiparameter flow cytometry analyses combined with single-cell RNA sequencing methods (scRNA-Seq and Strand-Seq), will decipher the mechanistic insights of T-cell leukemias in response to conventional epigenetic modulators.

EXPECTED RESULTS AND POTENTIAL IMPACT: These studies will characterize critical molecular events that drive the progression of human T-cell progenitors from normal to outright malignant states. They will define the genomic mechanisms that underlie enactment of the malignant gene expression program in T-ALL. They will also identify points of vulnerability that are unique to malignant cells and provide rationale for designing more effective, less toxic therapies. Finally, these findings will improve our current understanding of leukemic cell heterogeneity and underline the biological processes that promote cancer growth and survival.