Document Type : Research Articles
Department of Microbiology, Hematology and Immunology, Faculty of Pharmacy, Damascus University, Ministry of High Education, Damascus, Syria.
Department of Molecular Biology and Biotechnology, Human Genetics Division, Atomic Energy Commission, Damascus, Syria.
Objective: Somatic mutations in exon 12 of the NPM1 gene is one of the most common genetic abnormalities in adult acute myeloid leukemia (AML), which is observed in 25-35% of AML patients and in 50-60% of patients with cytogenetically normal AML (CN-AML). Methods: We performed Sanger sequencing of exon 12 of the NPM1 gene, on 44 CN-AML patients to characterize NPM1 status. Results: In this study, NPM1 mutations were identified in 10 (22.7%) of the 44 CN-AML patients. Among the 10 patients with NPM1 mutations, type A NPM1 mutations were identified in 8 (80%) patients, whereas non-A type NPM1 mutations were observed in 2 (20%) patients. Two non-A type NPM1 mutations were not previously reported: c.867-868InsCGGA and c.861-862InsTGCA. These two novel mutant proteins display a nuclear export signal (NES) motif (L-xxx-L-xx-V-x-L) less frequently and L-x-Lx-V-xx-V-x-L it has been never seen before, yet. However, both novel mutations show a tryptophan loss at codon 288 and 290 at the mutant C-terminus which are crucial for aberrant nuclear export of NPM into the cytoplasm. Conclusions: This study suggests previously unreported NPM1 mutations may be non-rare and thus additional sequence analysis is needed along with conventional targeted mutational analysis to detect non type-A NPM1 mutations.