NPM1 and acute myeloid leukemia: The most frequent mutations in cytogenetically normal AML affect the FLT3 and NPM1 genes (the latter lead to a predominantly cytoplasmic localization of the chaperone protein NPM1, hence are referred to as “NPM1c”) [4,5,6], and mice whose hematopoietic cells carry a Flt3-ITD and an Npm1c allele develop an aggressive, AML-like disease [38].