NPM1 and acute myeloid leukemia: To investigate the role of NPM1-mA on differentiation of leukemia cells, We first confirmed that, in contrast to AML cell line OCI-AML3 naturally carrying NPM1-mA [25], the AML cell lines KG-1a, HL60, K562 and THP-1 lacked NPM1-mA expression (Figure 1A–1B).