EZH2-driven immune evasion defines high-risk pediatric AML with t(16;21) FUS::ERG gene fusion.

Minimal improvement in outcomes for high-risk pediatric acute myeloid leukemia (pAML) patients has been made in the past decades. Nowhere is this more evident than in patients carrying a t(16;21)(p11;q22) FUS::ERG translocation; quick time to relapse and universal failure of hematopoietic stem cell transplant contribute to one of the lowest survival rates in childhood leukemia. Here, we have identified a unique, defining immune-evasion phenotype in FUS::ERG pAML driven by EZH2 and characterized by loss of MHC class I and II molecules and immune co-stimulatory receptors. This loss of immune engagement, present at diagnosis, allows pervasiveness of blasts that prove resistant to standard treatment. We demonstrate that treatment with the FDA-approved EZH2 inhibitor tazemetostat, in combination with IFN-γ, reverses the phenotype, re-expresses MHC receptor expression, and reduces blast viability. EZH2 inhibitors provide a novel therapeutic option for this high-risk population and may prove a beneficial supplemental treatment for FUS::ERG pAML.