PF247 CONSEQUENCES OF NRAS MUTATIONS IN PATIENTS WITH ACUTE MYELOID LEUKEMIA
Authors: Durinikova A. , Folta A. , Culen M. , Kosarova Z. , Tom N. , Al Tukmachi D. , Cetkovsky P. , Jindra P. , Szotkowski T. , Zak P. , Mayer J. , Racil Z. , Jeziskova I. 
Published: June 2019

Background:

Acute myeloid leukemia (AML) is a malignancy with a high prevalence of NRAS mutations. Transforming point mutations, located dominantly at hotspot codons 12, 13 and 61 of NRAS gene, occur in 11 to 22% of patients. Mutations in NRAS gene stimulate signalling activity of RAS pathway, resulting in an increased cellular proliferation and reduced apoptosis. Prognostic significance of NRAS gene mutations in AML patients remains controversial.

Aims:

The aim of our work was to analyze the association of NRAS gene mutations in AML with patient characteristics and outcomes.

Methods:

A total of 297 consecutive AML (non‐acute promyelocyte leukemia) patients (median age 53 years; range 19–70) with curative therapy were analyzed by next generation sequencing (NGS) using ClearSeq AML panel (Agilent Technologies) on MiSeq and NextSeq (Illumina). The NRAS mutations detected by NGS with variant allele frequency (VAF) ≥1.0% were verified by NRAS StripAssay (ViennaLab). Only mutations scored as positive by both methods were included in further analyses. Overall survival (OS) was analyzed by log‐rank (Mantel‐Cox) test. The comparative statistical analyses were evaluated by t‐test and Fisher's exact test.

Results:

In total, 84 mutations were identified in 66/297 (22.2%) analyzed AML patients. Fifteen patients (22.7%) were carriers of multiple gene mutations (range 1–3 mutations per patient). The mutations were most frequently found in the codon G12 (44/84 mutations, 52.4%), the most frequent gene mutations were: G12D (26/84; 31.0% mutations), G13D (15/84; 17.9%) and G12S (14/84; 16.7%). Furthermore, rare mutation G60E was identified in one patient. The median VAF of NRAS mutations was 7.0% (range 1.0–53.4%). Frequency of co‐mutation with FLT3‐TKD reached statistical significance (p = 0.025) and a trend for co‐mutation with NPM1 (p = 0.082) and DNMT3A (p = 0.091). A trend for mutual exclusivity was observed for FLT3‐ITD mutations with allelic ratio above 0.5 (p = 0.063). Occurrence of NRAS mutations was associated with younger age (median 48 vs. 54 years, respectively, p = 0.012), and a trend towards higher white blood cell count (median 41.0 vs. 14.2, respectively, p = 0.069). There was no association with OS, blast percentage in BM or sex. The presence of multiple NRAS mutations was not associated with analyzed characteristics nor patient outcomes.

Summary/Conclusion:

Our study showed NRAS gene mutations detected by two independent methods in more than one fifth of AML patients with curative therapy. Most of them have low VAF, therefore suggesting their later occurrence during leukemogenesis and limited proliferative potential. Although approximately 5% of AML patients harbor multiple NRAS mutations, we were not able to identify the difference between patients with one or more NRAS mutations.

Supported by Ministry of Health of the Czech Republic, grant nr. 15–25809A, project FNBr. 65269705 and project MUNI/A/1105/2018. All rights reserved.