Research Of NPM1 And FLT3-ITD Gene Mutations In Adult Patients With Acute Myeloid Leukemia

Objectives To detect the mutations of nucleophosmin(NPM1) and Internal tandem duplication of the FLT3 (FLT3-ITD)gene in acute myeloid leukemia (AML), observe the distribution of NPM1 and FLT3-ITD mutations in different subsets of AML, explore the relation of NPM1 and FLT3-ITD mutations with regard to clinical feature of AML, so that to provide theory evidence for clinic diagnosis, prognosis evaluation and targeted therapy.Methods1. NPM1 exon 12 mutations were detected using PCR and then directed to sequence. All the mutation cases were cloned with pMD18-T vector and sequenced again to analyze mutational location and types.2. FLT3-ITD mutations were determined by agarose electrophoresis of genomic DNA-PCR products. Resultes1. NPM1 exon 12 mutations were detected in 21 0f 75 (28%) AML cases. In acute myeloid leukemia with normal karyotype (AML-nk), NPM1 exon 12 mutations were detected in 14 0f 38 (36.8%) AML cases.2.Sequence analysis revealed 3 known mutations (type A,B,D) as well as a novel sequence variation. All mutation types were heterozygous. The known mutational types showed a 4bp insertion while the newly one was a different 3bp deletion and then 7bp insertions. Mutation A, due to a TCTG duplication, which accounts for 61.9% of adult cases was the most frequent mutation type. All the mutations were inserted between position nucleotide 960 through 961 or 960 through 964(Genebank accession number NM₀02520). Despite the heterogeneity of NPM1 mutations, all mutant proteins have lost both tryptophan residues 290 and 288 and shared the last 5 amino acid residues VSLRK at their C-terminus mutations.3. 16 of 75(21.3%) AML cases were detected with FLT3-ITD mutations. 26.7% of AML-nk were FLT3 ITD-mutated AML. Accoding to the electrophoresis results, the length of ITD was variety.4. FLT3-ITD was detected in 9 of 21(42.9 %) patients with AML who had NPM1 mutations.5. Aggregate analysis NPM1 and FLT3-ITD gene mutations in AML cases, 12 patients were NPM1-mutated/FLT3 ITD-negative group, 16 patients were FLT3 ITD-positive group. In the NPM1-mutated/FLT3 ITD-negative group, 9 patients were conducted as induction therapy, 8 patients reached complete remission(CR), the CR rate was 88.9%(8/9). In the FLT3 ITD-positive group, 9 patients were conducted as induction therapy, 4 patients reached CR, the CR rate was 44.4%(4/9).Conclusions1. NPM1 mutations had been found in AML with an incidence of 28% in adults, while FLT3-ITD mutations had been found of 21.3% in adults patients with acute myeloid leukemia. FLT3-ITD was detected in 42.9 % patients with AML who had NPM1 mutations.2. 4 different variant mutations have been identified in this research, 3 had been reported, another one was a newly found to date.3. To detect NPM1 and FLT3-ITD mutations could provide theory evidence for risk-adapted treatment protocols to improve treatment outcome and earlier period direct interference or target therapy with AML.