oligomycins and Leukemia--Myelogenous--Chronic--BCR-ABL-Positive

Chronic myeloid leukemia (CML) is effectively treated with tyrosine kinase inhibitors (TKIs), targeting the BCR::ABL1 oncoprotein. Still, resistance to therapy, relapse after treatment discontinuation, and side effects remain significant issues of long-term TKI treatment. Preliminary studies have shown that targeting oxidative phosphorylation (oxPhos) and the unfolded protein response (UPR) are promising therapeutic approaches to complement CML treatment. Here, we tested the efficacy of different TKIs, combined with the ATP synthase inhibitor oligomycin and the ER stress inducer thapsigargin in the CML cell lines K562, BV173, and KU812 and found a significant increase in cell death. Both, oligomycin and thapsigargin, triggered the upregulation of the UPR proteins ATF4 and CHOP, which was inhibited by imatinib. We observed comparable effects on cell death when combining TKIs with the ATP synthase inhibitor 8-chloroadenosine (8-Cl-Ado) as a potentially clinically applicable therapeutic agent. Stress-related apoptosis was triggered via a caspase cascade including the cleavage of caspase 3 and the inactivation of poly ADP ribose polymerase 1 (PARP1). The inhibition of PARP by olaparib also increased CML death in combination with TKIs. Our findings suggest a rationale for combining TKIs with 8-Cl-Ado or olaparib for future clinical studies in CML.

Topics: Adenosine Triphosphate; Apoptosis; Drug Resistance, Neoplasm; Enzyme Inhibitors; Fusion Proteins, bcr-abl; Humans; Leukemia, Myelogenous, Chronic, BCR-ABL Positive; Oligomycins; Oxidative Phosphorylation; Protein Kinase Inhibitors; Thapsigargin; Tyrosine Kinase Inhibitors

Although tyrosine kinase inhibitors (TKI) can be effective therapies for leukemia, they fail to fully eliminate leukemic cells and achieve durable remissions for many patients with advanced BCR-ABL(+) leukemias or acute myelogenous leukemia (AML). Through a large-scale synthetic lethal RNAi screen, we identified pyruvate dehydrogenase, the limiting enzyme for pyruvate entry into the mitochondrial tricarboxylic acid cycle, as critical for the survival of chronic myelogenous leukemia (CML) cells upon BCR-ABL inhibition. Here, we examined the role of mitochondrial metabolism in the survival of Ph(+) leukemia and AML upon TK inhibition.. Ph(+) cancer cell lines, AML cell lines, leukemia xenografts, cord blood, and patient samples were examined.. We showed that the mitochondrial ATP-synthase inhibitor oligomycin-A greatly sensitized leukemia cells to TKI in vitro. Surprisingly, oligomycin-A sensitized leukemia cells to BCR-ABL inhibition at concentrations of 100- to 1,000-fold below those required for inhibition of respiration. Oligomycin-A treatment rapidly led to mitochondrial membrane depolarization and reduced ATP levels, and promoted superoxide production and leukemia cell apoptosis when combined with TKI. Importantly, oligomycin-A enhanced elimination of BCR-ABL(+) leukemia cells by TKI in a mouse model and in primary blast crisis CML samples. Moreover, oligomycin-A also greatly potentiated the elimination of FLT3-dependent AML cells when combined with an FLT3 TKI, both in vitro and in vivo.. TKI therapy in leukemia cells creates a novel metabolic state that is highly sensitive to particular mitochondrial perturbations. Targeting mitochondrial metabolism as an adjuvant therapy could therefore improve therapeutic responses to TKI for patients with BCR-ABL(+) and FLT3(ITD) leukemias.

Topics: Animals; Antineoplastic Combined Chemotherapy Protocols; Apoptosis; Cell Line, Tumor; Dihydrolipoyllysine-Residue Acetyltransferase; Disease Models, Animal; Female; fms-Like Tyrosine Kinase 3; Fusion Proteins, bcr-abl; Humans; Imatinib Mesylate; Ketone Oxidoreductases; Leukemia, Myelogenous, Chronic, BCR-ABL Positive; Membrane Potential, Mitochondrial; Mice; Mice, Inbred C57BL; Mice, Inbred NOD; Mice, Knockout; Mitochondria; Mitochondrial Proteins; Mitochondrial Proton-Translocating ATPases; Oligomycins; Protein Kinase Inhibitors; Protein-Tyrosine Kinases; RNA Interference; RNA, Small Interfering; Superoxides