NPM1 Mutation in Acute Myeloid Leukemia

Nucleophosmin (NPM) is a ubiquitously expressed chaperone protein that shuttles rapidly between the nucleous and cytoplasm, but predominantly resides in the nucleous. It plays key roles in ribosome biogenesis, centrosome duplication, genomic stability, cell cycle progression and apoptosis. Somatic mutations in exon 12 of the NPM gene (NPM1) are the most frequent genetic abnormality in adult AML, found in approximately 35% of all cases and up to 60% of patients with normal karyotype AML. NPM1 mutations lead to aberrant localization of the NPM protein into the cytoplasm Mutated nucleophosmin (NPM1) gene which as a molecular biomarker, plays an important role in the prognostication of adult acute myeloid leukemia (AML) and is currently investigated in AML patients. we designed a rapid and sensitive method based on the amplification-refractory mutation system- polymerase chain reaction (ARMS-PCR), to detect the most common mutations of the NPM1 gene, which are mostly four base pair insertions and compared its detection rate with that of two currently used methods, namely direct sequencing and capillary electrophoresis. Results: According to the results of capillary electrophoresis analysis and direct sequencing, the incidence of mutation was 22% (33% of patients with normal karyotypes and only 16% of patients abnormal karyotypes). The ARMS results were 100% consistent. ARMS also helped determine the mutation status of an extra set of patients who had low call rates on capillary electrophoresis and appeared normal on direct sequencing. The low mutation rate in some patients hindered the detection because of the mingling of the mutation signal into background noise. The low sensitivity of these methods in detecting low rate mutations could result in a false negative result that adversely affects prognostication and therapy. It was observed that the detection rate of ARMS could be higher than direct sequencing and capillary electrophoresis analysis, most probably because of the fact that in the ARMS- based method, the mutated variant is specifically detected by a specific primer which would otherwise escape detection in a simple PCR method because of lower quantity. We concluded that this asset together with the rapidity and low expense could make it a suitable choice for clinical laboratories.

کلیدواژه ها:

nucleophosmin ، NPM1 ، ARMS-PCR ، PCR ، capillary electrophoresis ، fragment analysis ، direct sequencing