The frequency of NPM1 mutations in childhood acute myeloid leukemia

Mutations in the nucleophosmin (NPM1) gene have been solely associated with childhood acute myeloid leukemia (AML). We evaluated the frequency of NPM1 mutations in childhood AML, their relation to clinical and cytogenetic features and the presence of common FLT3 and RAS mutations. NPM1 mutations were found in 8% of cases. They involved the typical type 'A' mutation and one novel mutation characterized by two individual base pair substitutions, which resulted in 2 amino acid changes (W290) and (S293) in the NPM protein. FLT3/ITD mutations were observed in 12% of the cases and in one NPM1-mutated case bearing also t(8;21) (q22;q22). No common RAS mutations were identified. A relatively consistent NPM1 mutation rate was observed, but with variations in types of mutations. The role of different types of NPM1 mutations, either individually or in the presence of other common gene mutations may be essential for childhood AML prognosis.