Mutation of NPM1 and FLT3 Genes in Acute Myeloid Leukemia and Their Association with Clinical and Immunophenotypic Features

BACKGROUND Mutations in NPM1 and FLT3 genes represent the most frequent genetic alterations and important diagnostic and prognostic indicators in patients with acute myeloid leukemia (AML). OBJECTIVE We investigated the prevalence and clinical characteristics of NPM1 and FLT3 mutations in 161 patients of de novo AML including adults and children. RESULTS NPM1 mutation was found in 21% and FLT3 mutation in 25% of the AML patients. Thirteen (8%) samples were positive for both NPM1 and FLT3/ITD mutations. Adult patients had significantly higher frequency of NPM1 mutation than children (25.8% versus 8.8%; P = 0.02). Further, NPM1 mutation was found to be more frequent in patients above 45 years of age (P = 0.02). NPM1 mutation was significantly associated with higher platelet count (P = 0.05) and absence of hepatosplenomegaly (P = 0.01), while FLT3/ITD mutation was associated with higher white blood count (P = 0.01). Immunophenotypically, NPM1 mutation was associated with the lack of CD34 (P < 0.001) and HLD-DR expression (P < 0.001), while FLT3/ITD mutation was positively associated with the expression of CD7 (P = 0.04). No correlation was found between NPM1 mutation and fusion gene. Interestingly, FLT3/ITD mutation was found to be inversely associated with AML/ETO fusion gene (P = 0.04). CONCLUSIONS The results suggest that distinct clinical and immunophenotypic characteristics of NPM1 and FLT3/ITD mutations present further insight into the molecular mechanism of leukemogenesis.