Dysfunctional DNA double‐strand break repair is present in a subset of primary t‐aml myeloblasts

Abstract

We hypothesized that dysregulation of double‐strand DNA break (DSB) repair occurs in treatment related acute myeloid leukemia (t‐AML), a tumor characterized by chromosomal abnormalities, and may result from acquired mutations in homology‐directed repair (HDR) or non‐homologous end joining (NHEJ) pathway genes. We used next‐generation sequencing technology to identify acquired mutations in 6/24 t‐AML patients in 3 genes (RAD51L3, EME1, TP53) involved in HDR/NHEJ and DNA damage response. We used array comparative genomic hybridization array (aCGH) to identify 104 copy number alterations (CNAs) in 30 t‐AML samples, of which 40 CNAs were detected only by aCGH and not by cytogenetics, with many CNAs containing DNA repair genes. Finally, a functional assay was used to evaluate the induction and kinetics of histone H2AX (pH2AX) phosphorylation, a well established marker for DSB, following irradiation (IR) of primary tumor cells. Compared to normal human CD34+ hematopoietic progenitor cells (controls), 11/15 t‐AML patients had abnormal pH2AX levels at baseline or post IR, consistent with dysfunctional DSB repair. 10/11 abnormal t‐AML samples had a mutation or CNA in a DNA repair gene compared to 1/4 t‐AML samples with no pH2AX abnormality (p<0.05). This study confirms that DNA repair genes are mutated in t‐AML and suggests that dysfunctional DSB repair is present in t‐AML tumor cells. T32‐HL007088, K12 HL087107.