Nucleophosmin (NPM1) gene variants in Egyptian patients with acute myeloid leukemia

To the editor Kassem et al. [1] described a novel mutational deletion [del 1178 (A)] in the 30 untranslated region of NPM1 gene detected in a heterozygous form in seven de novo acute myeloid leukemia (AML) patients of their study population. The described nucleotide deletion is an NPM1 gene polymorphism recorded in db SNP database (rs34351976; g28027: Genbank accession number NG016018.1) (http://www.ncbi.nlm.nih.gov/projects/SNP/) and was described previously by Do hner et al. [2] and Chou et al. [3]. This variant accounted for 60-70% of AML patients with normal karyotype [2]. The putative deletion was also identified in healthy volunteers and persisted at complete remission and also at relapse of AML patients [3]. This deletion had no effect on the predicted amino acid sequence and is not in linkage disequilibrium with any previously identified NPM1 mutations [2,3]. Analysis of RNA folding at the region surrounding the rs34351976 in the presence or absence of the deletion using Mfold analysis software (http://www.mfold.rna.albany.edu) revealed no RNA folding change that may alter RNA splicing and subsequently gene expression. Furthermore, splicing motifs analysis using Human Splicing Finder software version 2.4.1 showed that the presence of the deletion does not abolish any recognition site of exonic or intronic enhancers or silencer motifs. In general, it seems that the impact of NMP1 polymorphisms on the molecular pathogenesis of AML is not clear yet and needs further investigation. Kassem et al. [1] describes the molecular aspect of de novo AML in the Egyptian population. The previously known NPM1 mutations mentioned in their study are less frequent compared to the figures recorded worldwide. Moreover, the authors wondered whether the NPM1 variants identified in their patients may confer a better outcome of AML. According to the previously mentioned data, one can speculate that the presence of NPM1 gene polymorphism (rs34351976) should not be mistaken as being a diagnostic or prognostic marker of de novo AML. Although NPM1 mutation detection is important in the diagnostic work-up of AML patients with normal karyotype, physicians should be more cautious while interpreting the data of NPM1 gene sequencing. In addition, the relation of NPM1 polymorphism to de novo AML etiology necessitates further clarification.