The cytoplasmic-localized NPM1 mutants (NPMc+) have a significant role in the development of AML.13 Moreover, integration of the GM-CSF encoding Csf2 gene into the genome of NPMc+ transgenic mice could accelerate the onset of AML.15 In light of the GM-CSF-induced P-STAT5–NPM1 signaling pathway, the increased GM-CSF levels resulting from aberrant Csf2 expression are likely to suppress NPM1 expression level in leukemic cells. This evidence concerns the gene NPM1 and acute myeloid leukemia.