p53^-/- synergizes with enhanced Nras^G12D signaling to transform megakaryocyte-erythroid progenitors in acute myeloid leukemia

Somatic mutations in TP53 and NRAS are associated with transformation of human chronic myeloid diseases to acute myeloid leukemia (AML). Here, we report that concurrent RAS pathway and TP53 mutations are identified in a subset of AML patients and confer an inferior overall survival. To further investigate the genetic interaction between p53 loss and endogenous Nras^G12D/1 in AML, we generated conditional Nras^G12D/1p53²/2 mice. Consistent with the clinical data, recipient mice transplanted with Nras^G12D/1p53²/2 bone marrow cells rapidly develop a highly penetrant AML. We find that p53²/² cooperates with Nras^G12D/1 to promote increased quiescence in megakaryocyte-erythroid progenitors (MEPs). Nras^G12D/1p53²/² MEPs are transformed to self-renewing AML-initiating cells and are capable of inducing AML in serially transplanted recipients. RNA sequencing analysis revealed that transformed MEPs gain a partial hematopoietic stem cell signature and largely retain an MEP signature. Their distinct transcriptomes suggests a potential regulation by p53 loss. In addition, we show that during AML development, transformed MEPs acquire overexpression of oncogenic Nras, leading to hyperactivation of ERK1/2 signaling. Our results demonstrate that p53²/² synergizes with enhanced oncogenic Nras signaling to transform MEPs and drive AML development. This model may serve as a platform to test candidate therapeutics in this aggressive subset of AML.