Flow cytometry in detection of Nucleophosmin 1 mutation in acute myeloid leukemia patients: A reproducible tertiary hospital experience

Introduction: Nucleophosmin 1 (NPM1) mutation is one of the most frequent gene mutations in adult acute myeloid leukemia (AML), being detected in 35% of all cases and in up to 60% of patients with normal karyotype AML. AML with mutated NPM1 has distinct pathology, immunophenotyping, and confirmed favorable prognostic significance. Hence, AML with mutated NPM1 is a separate entity in the revised 2016 World Health Organization classification. This study aimed to evaluate the use of a reproducible flow cytometry approach in the assay of mutant NPM1 protein in AML patients and to correlate flow cytometric results with the NPM1 gene mutation.

Methods: Eighty-nine newly diagnosed AML patients were evaluated for the expression of mutant NPM1 using flow cytometry and for the presence of NPM1 exon 12 mutations using high-resolution melting polymerase chain reaction (HRM PCR).

Results: The NPM1 mutation was found in 35 (39.3%) patients by HRM PCR. These patients showed a significantly higher level of percentage of positive-stained cells (% positive cells) and normalized median fluorescence intensity (MFI) for mutant NPM1 by flow cytometry than the negative mutation group.

Conclusion: Flow cytometric detection of mutant NPM1 offers a possible tool to indicate NPM1 mutational status.