title: Mitochondrial regulation by c-Myc and hypoxia-inducible factor-1 alpha controls sensitivity to econazole.
abstract: Econazole is an azole antifungal with anticancer activity that blocks Ca(2+) influx and stimulates endoplasmic reticulum (ER) Ca(2+) release through the generation of mitochondrial reactive oxygen species (ROS), resulting in sustained depletion of ER Ca(2+) stores, protein synthesis inhibition, and cell death. c-Myc, a commonly activated oncogene, also promotes apoptosis in response to growth factor withdrawal and a variety of chemotherapeutic agents. We have investigated the role of c-myc in regulating sensitivity to econazole. Here, we show that c-myc-negative cells are profoundly resistant to econazole. c-Myc-negative rat fibroblasts failed to generate mitochondrial ROS in response to econazole and consequently failed to deplete the ER of Ca(2+). HL60 cells knocked down for c-myc expression also displayed decreased ROS generation and decreased econazole sensitivity. Addition of H(2)O(2) restored sensitivity to econazole in both c-myc-negative rat fibroblasts and c-myc knocked-down HL60 cells, supporting a role for ROS in cell death induction. c-Myc-negative cells and HL60 cells knocked down for c-myc have reduced mitochondrial content compared with c-myc-positive cells. The hypoxia sensor, hypoxia-inducible factor-1alpha (HIF-1alpha), interacts antagonistically with c-myc and also regulates mitochondrial biogenesis. Knockdown of HIF-1alpha in c-myc-negative cells increased mitochondrial content restored ROS generation in response to econazole and increased sensitivity to the drug. Taken together, these results show that c-myc and HIF-1alpha regulate sensitivity to econazole by modulating the ability of the drug to generate mitochondrial ROS.
authors.affiliation: Arthritis and Immune Disorder Research Centre, University Health Network, Toronto Medical Discovery Tower, Toronto, ON, Canada.
authors.forename: Yongmao
authors.initials: Y
authors.lastname: Yu
authors.forename: Maryam
authors.initials: M
authors.lastname: Niapour
authors.forename: Yicheng
authors.initials: Y
authors.lastname: Zhang
authors.forename: Stuart A
authors.initials: SA
authors.lastname: Berger
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D004464:Econazole / Q000494:pharmacology*; D004721:Endoplasmic Reticulum / Q000378:metabolism; D018922:HL-60 Cells; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000502:physiology*; D008928:Mitochondria / Q000502:physiology*; D016271:Proto-Oncogene Proteins c-myc / Q000502:physiology*; D051381:Rats; D017382:Reactive Oxygen Species / Q000378:metabolism
chemical_list: D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D016271:Proto-Oncogene Proteins c-myc; D017382:Reactive Oxygen Species; D004464:Econazole; D002118:Calcium