Knockdown of EPC1 or EPC2 induced cell apoptosis in K562 cells rather than in embryonic HSPCs, not only agreeing with the reports that knockdown of EPC1 and/or EPC2 induced apoptosis in AML cells,20 but also suggesting that roles of EPC1 and EPC2 in apoptosis are different between in vivo and in vitro cells. This evidence concerns the gene EPC2 and acute myeloid leukemia.