Thus, the C terminus of the mutated NPM1 loses the amino acid tryptophan in positions W288 and W290 (or W290 alone), causing the disruption of the folded helix structure, the loss of the nucleolar localization signal and the aberrant cytoplasmic localization of NPM1 mutants, as observed in AML [7,11,12,13,14]. This evidence concerns the gene NPM1 and acute myeloid leukemia.