A gain-of-function p53 mutant oncogene promotes cell fate plasticity and myeloid leukemia through the pluripotency factor Foxh1

Mutations in the TP53 tumor suppressor gene are common in many cancer types, including the acute myeloid leukemia (AML) subtype known as complex karyotype (CK) AML. Here, we identify a gain-of-function (GOF) p53 mutation that accelerates CK-AML initiation beyond p53 loss and, surprisingly, is required for disease maintenance. The p53R172H mutation (TP53R175H in humans) exhibits a neomorphic function by promoting aberrant self-renewal in leukemic cells, a phenotype that is present in hematopoietic stem and progenitor cells (HSPCs) even prior to their transformation. We identify the Forkhead box H1 transcription factor (Foxh1) as a critical mediator of mutant p53 function that binds to and regulates stem cell-associated genes and transcriptional programs. Our results identify a context where mutant p53 acts as a bona fide oncogene that contributes to the pathogenesis of CK-AML and suggests a common biological theme for TP53 gain-of-function in cancer. RNA-sequencing of duplicated samples per condition were derived from idependent biological replicates and were then sequenced using Illumina Hiseq 2500 ChIP-sequencing of Foxh1 in p53R172H mutant murine AML cells