IDH1/2 mutations sensitize acute myeloid leukemia to PARP inhibition and this is reversed by IDH1/2-mutant inhibitors

Somatic mutations in IDH1/2 occur in ~20% of patients with myeloid neoplasms, including acute myeloid leukemia (AML). IDH1/2MUT enzymes produce D-2-hydroxyglutarate (D2HG), which associates with increases in DNA damage and improved responses to chemo/radiotherapy and PARP inhibitors in solid tumor cells. Whether this also holds true for IDH1/2MUT AML is not known. Well-characterized primary IDH1MUT, IDH2MUT and IDH1/2WT AML cells were analyzed for DNA damage and responses to daunorubicin, ionizing radiation and PARP inhibitors. IDH1/2MUT caused increased DNA damage and sensitization to daunorubicin, irradiation, and the PARP inhibitors olaparib and talazoparib in AML cells. IDH1/2MUT inhibitors protected against these treatments. Combined treatment with a PARP inhibitor and daunorubicin had an additive effect on the killing of IDH1/2MUT AML cells. We provide evidence that the therapy sensitivity of IDH1/2MUT cells was caused by D2HG-mediated downregulation of expression of the DNA damage response gene ATM and not by altered redox responses due to metabolic alterations in IDH1/2MUT cells. IDH1/2MUT AML cells are sensitive to PARP inhibitors as monotherapy but especially when combined with a DNA-damaging agent such as daunorubicin, whereas concomitant administration of IDH1/2MUT inhibitors during cytotoxic therapy decrease the efficacy of both agents in IDH1/2MUT AML. These results advocate in favor of clinical trials of PARP inhibitors either or not in combination with daunorubicin in IDH1/2MUT AML