[The Mutated Gene Sequenced by NGS and the Correlation of Their Coexistent Mutual Exclusiveness in NPM1 Mutated Acute Myeloid Leukemia]

Objective: To analyze the clinicobiological heterogeneity of NPM1 mutated (NPM1^mut) acute myeloid leukemia (AML) detected by next generation sequencing (NGS) and their coexistence and mutual exclusivity relationship in the AML subtype.

Methods: The NGS data based on 112 genes related to blood disease in 238 newly diagnosed patients with NPM1^mut were collected. The χ2 test and non-parametric test were used to analyze the distribution correlation between the genes in the mutational spectrum.

Results: Among all the patients, at least one co-mutation was detected out. The median number per case of the mutated genes, including NPM1^mut was 4.5 (range 2－14), among them, there were 5.0 (range 2－10) for NPM1^mut/FLT3-ITD⁺ and 4.0 (range 2－14) for NPM1^mut/FLT3-ITD^- cases, but it was no significant difference between the two groups (P=0.378). A total of 240 NPM1 mutational events were detected out in entire 238 NPM1^mut patients, of which 10 (4.2%) were missense mutations, and were all found in NPM1^mut/FLT3-ITD^- patients. Most (9/10, 90%) of these NPM1 missense mutations were accompanied by AML subtype-defining cytogenetic or molecular abnormalities, of which 7 patients were in low risk or 2 in high risk. The most common NPM1^mut coexisting mutations were DNMT3A (104, 43.7%), followed were FLT3-ITD (95, 39.9%) and FAT1 (57, 23.9%), FLT3-ITD and DNMT3A showed significant coexistence (P=0.005). FLT3-ITD showed significantly reciprocal exclusivity with FLT3-nonITD (P<0.001), NRAS (P<0.001), PTPN11 (P=0.017) and IDH1 (P=0.005), and showed an exclusivity inclination with KRAS (P=0.073). In addition, FLT3-nonITD along with KRAS (P=0.035), NRAS along with KRAS (P=0.008) and PTPN11 (P=0.039) coexisted significantly.

Conclusion: Prognoses of AML involving less common NPM1 missense mutations should be stated on a case by case basis. The mutational landscape and co-occurrence and mutual exclusivity correlations of NPM1^mut AML provide a mechanism explaining biological diversity and clinical heterogeneity in this AML subset.