3170 – SINGLE-CELL MULTI-OMICS RESOLVES THE EVOLUTION OF TP53-MUTANT LEUKEMIA

TP53 regulates self-renewal and quiescence of hematopoietic stem cells, and its disruption leads to the development of hematological malignancies. In myeloid neoplasms, TP53 mutations define a distinct clinical entity, associated with complex cytogenetics and dismal outcomes. Understanding the cellular and molecular framework through which TP53 mutation drives clonal evolution is a crucial step towards the design of rational therapeutic strategies. Here, we carry out TARGET-seq single-cell multi-omic analysis of haematopoietic stem/progenitor cells (HSPC) from patients with a myeloproliferative neoplasm who had transformed to TP53-mutant secondary acute myeloid leukaemia (sAML), a trackable model of TP53-driven clonal evolution. We invariably identified convergent clonal evolution leading to complete loss of TP53 wild-type (WT) alleles and gain of multiple chromosomal abnormalities upon transformation. TP53-mutant leukaemia stem cells (LSC) were transcriptionally distinct from de novo AML, with evidence of inflammation-associated transcription and aberrant erythroid differentiation. We identified a TP53-mutant LSC signature which was strongly predictive of adverse outcome in both TP53-mutant (HR:3.4) and WT AML (HR:3.1). Finally, we demonstrate a hitherto unrecognised effect of chronic inflammation in promoting disease progression. Sustained inflammatory stimuli (pIpC) led to a 2.5-fold expansion of TP53-mutant cells in WT:TP53R172H/+ chimeras, whereas WT cells were depleted. This indicates that pro-inflammatory cues promote fitness advantage of TP53-mutant cells whilst suppressing antecedent clones. In summary, we present a comprehensive single-cell multi-omic analysis ofTP53-mediated transformation, providing unique insights into the evolution of chronic hematological malignancies towards an aggressive acute leukemia and of broader relevance to other cancer types.