FLT3 and JAK2 mutations in acute myeloid leukemia promote inter-chromosomal homologous recombination and the potential for copy neutral loss of heterozygosity (CN-LOH)

Acquired copy neutral loss-of-heterozygosity (CN-LOH) is a frequent occurrence in myeloid malignancies and is often associated with resistance to standard therapeutic modalities and poor survival. Here we show that constitutive signaling driven by mutated FLT3 and JAK2 confers inter-chromosomal homologous recombination (iHR), a precedent for CN-LOH. Using a targeted recombination assay, we determined significant iHR activity in internal tandem duplication FLT3 (FLT3-ITD) and JAK2V617F mutated cells. Sister chromatid exchanges, a surrogate measure of iHR, was significantly elevated in primary FLT3-ITD normal karyotype acute myeloid leukemia (NK-AML) compared to wild type FLT3 NK-AML. Homologous recombination (HR) was harmonized to S phase of the cell cycle to repair broken chromatids and prevent iHR. Increased HR activity in G0 arrested primary FLT3-ITD NK-AML in contrast to wild-type FLT3 NK-AML. Cells expressing mutated FLT3-ITD demonstrated a relative increase in mutation frequency as detected by thymidine kinase (TK) gene mutation assay. Moreover, resistance was associated with CN-LOH at the TK locus. Treatment of FLT3-ITD and JAK2V617F mutant cells with the antioxidant N-acetylcysteine diminished reactive oxygen species (ROS), restoring iHR and HR levels. Our findings show that mutated FLT3-ITD and JAK2 augment ROS production and HR, shifting the cellular milieu towards illegitimate recombination events such as iHR and CN-LOH. Therapeutic reduction of ROS may thus prevent leukemic progression and relapse in myeloid malignancies.

from #AlexandrosSfakianakis via Alexandros G.Sfakianakis on Inoreader http://ift.tt/2iVsaJY
via IFTTT