Journal Article

Apoptotic Efficacy of Etomoxir in Human Acute Myeloid Leukemia Cells. Cooperation with Arsenic Trioxide and Glycolytic Inhibitors, and Regulation by Oxidative Stress and Protein Kinase Activities

Calvo, Susana, Calviño, Eva, Guillén-Guío, Beatriz, Estañ, María Cristina, Aller, Patricio, de Blas, Elena, Rial, Eduardo, Boyano-Adánez, María del Carmen

2014

Overview

Fatty acid synthesis and oxidation are frequently exacerbated in leukemia cells, and may therefore represent a target for therapeutic intervention. In this work we analyzed the apoptotic and chemo-sensitizing action of the fatty acid oxidation inhibitor etomoxir in human acute myeloid leukemia cells. Etomoxir caused negligible lethality at concentrations up to 100 µM, but efficaciously cooperated to cause apoptosis with the anti-leukemic agent arsenic trioxide (ATO, Trisenox), and with lower efficacy with other anti-tumour drugs (etoposide, cisplatin), in HL60 cells. Etomoxir-ATO cooperation was also observed in NB4 human acute promyelocytic cells, but not in normal (non-tumour) mitogen-stimulated human peripheral blood lymphocytes. Biochemical determinations in HL60 cells indicated that etomoxir (25-200 µM) dose-dependently inhibited mitochondrial respiration while slightly stimulating glycolysis, and only caused marginal alterations in total ATP content and adenine nucleotide pool distribution. In addition, etomoxir caused oxidative stress (increase in intracellular reactive oxygen species accumulation, decrease in reduced glutathione content), as well as pro-apoptotic LKB-1/AMPK pathway activation, all of which may in part explain the chemo-sensitizing capacity of the drug. Etomoxir also cooperated with glycolytic inhibitors (2-deoxy-D-glucose, lonidamine) to induce apoptosis in HL60 cells, but not in NB4 cells. The combined etomoxir plus 2-deoxy-D-glucose treatment did not increase oxidative stress, caused moderate decrease in net ATP content, increased the AMP/ATP ratio with concomitant drop in energy charge, and caused defensive Akt and ERK kinase activation. Apoptosis generation by etomoxir plus 2-deoxy-D-glucose was further increased by co-incubation with ATO, which is apparently explained by the capacity of ATO to attenuate Akt and ERK activation. In summary, co-treatment with etomoxir may represent an interesting strategy to increase the apoptotic efficacy of ATO and (with some limitations) 2-deoxy-D-glucose which, although clinically important anti-tumour agents, exhibit low efficacy in monotherapy.

• Publisher: Public Library of Science,Public Library of Science (PLoS)
• Subject: Acute myeloid leukemia / Adenine / Adenosine triphosphate / AKT protein / AMP / Analysis / Anticancer properties / Antineoplastic Combined Chemotherapy Protocols - therapeutic use / Apoptosis / Apoptosis - drug effects / Arsenic / Arsenic Trioxide / Arsenicals - therapeutic use / ATP / Biology and Life Sciences / Cancer / Cell Line, Tumor / Chemotherapy / Cisplatin / Cooperation / Deoxyglucose - therapeutic use / Dextrose / Effectiveness / Electron transport / Energy charge / Epoxy Compounds - therapeutic use / Etoposide / Extracellular signal-regulated kinase / Fatty acids / Glucose / Glucose metabolism / Glutathione / Glycolysis / Glycolysis - drug effects / Health aspects / Humans / Incubation / Indazoles - therapeutic use / Inhibitors / Lethality / Leukemia / Leukemia, Myeloid, Acute - drug therapy / Lymphocytes / Medicine and Health Sciences / Mitochondria / Myeloid leukemia / Oxidation / Oxidative stress / Oxidative Stress - drug effects / Oxides - therapeutic use / Oxygen / Peripheral blood / Protein kinase / Protein kinases / Protein Kinases - drug effects / Reactive oxygen species / Sensitizing / Synthesis / Tumors