Somatic exonic deletions in RUNX1 constitutes a novel recurrent genomic abnormality in acute myeloid leukemia.

Abstract

In acute myeloid leukemia (AML), somatic mutations (commonly missense, nonsense and frameshift indels) in RUNX1 are associated with a dismal clinical outcome. Inherited RUNX1 mutations cause familial platelet disorder. As approximately 5-10% of germline RUNX1 mutations are large exonic deletions, we hypothesized that such exonic RUNX1 aberrations may also be acquired during the development of AML. Sixty well-characterized AML patients were analyzed with Multiplex Ligation-dependent Probe Amplification (MLPA, n=60), micro-array (n=11) and/or whole genome sequencing (WGS, n=8). In total, 25 (42% of the cohort) RUNX1-aberrant patients (defined by the presence of classical mutations and/or exonic deletions) were identified. Sixteen patients (27%) carried only exonic deletions, 5 (8%) carried classical mutations and 4 (7%) carried both exonic deletions and mutations. No significant difference was observed between patients with classical RUNX1 mutations and RUNX1 exonic deletions in median overall survival (OS, 53.1 vs 38.8 months respectively, p=0.63). When applying the European Leukemia Net (ELN) classification including the RUNX1-aberrant group, 20% of the patients initially stratified as intermediate-risk (5% of the whole cohort) were re-assigned to the high-risk group, which improved the performance of ELN classification regarding OS between intermediate and high-risk group (18.9 vs 9.6 months, p=0.09). Somatic RUNX1 exonic deletions constitute a novel recurrent aberration in AML. Our findings have important clinical implications regarding AML classification, risk-stratification and treatment decision. Moreover, they argue in favor of further investigating such genomic aberrations not only in RUNX1 but also in other genes implicated in cancer biology and management.