PRDM9 and neoplasm: EPZ-6438 is an inhibitor of the histone methyltransferase EZH2 that has recently entered clinical trials for MPM patients due to its antiproliferative effects on tumor cells [21,22]; however, the impact of this epigenetic modulator on the TME and the effects of TME on MPM cell responsiveness to EZH2 inhibitors are still largely unexplored.