Targeting the MTF2-MDM2 Axis Sensitizes Refractory Acute Myeloid Leukemia to Chemotherapy

Next generation sequencing of acute myeloid leukemia (AML) patient samples has enabled more granular risk stratification of patients; however, refractory AML patients can be found across all risk groups, suggesting that non-genetic lesions regulate chemoresponsiveness. Consistent with this hypothesis is the finding that many of the mutated AML driver genes are encode epigenetic modifiers. Thus, unraveling the epigenetic dysregulation in AML is critical to better understand disease initiation and progression, as well as develop targeted therapies. Metal Response Element Binding Transcription Factor 2/Polycomblike 2 (MTF2/PCL2) plays a fundamental role in recruiting the Polycomb repressive complex 2 (PRC2) to chromatin and we show that it is commonly silenced in primary AML patient cells at diagnosis. Furthermore, the loss of MTF2 in hematopoietic stem and progenitor cells (HSPCs) leads to an altered epigenetic state that underlies refractory AML. By implementing unbiased systems analyses, we identified the E3 ubiquitin ligase MDM2 that inhibits p53 as a direct target of MTF2-PRC2. MTF2 deficiency leads to over-expression of MDM2 and inhibition of p53-mediated cell cycle regulation and apoptosis, leading to chemoresistance and refractory AML. Targeting this dysregulated signaling pathway by MTF2 overexpression or MDM2 inhibitors sensitized refractory patient leukemic cells to induction chemotherapeutics and prevented relapse in AML patient-derived xenograft (PDX) mice. Therefore, we have uncovered a direct epigenetic mechanism by which MTF2 functions as a tumor suppressor required for AML chemotherapeutic sensitivity and identified a potential therapeutic strategy to treat refractory AML.