title: Mitotane alters mitochondrial respiratory chain activity by inducing cytochrome c oxidase defect in human adrenocortical cells.
abstract: Mitotane, 1,1-dichloro-2-(o-chlorophenyl)-2-(p-chlorophenyl)ethane is the most effective medical therapy for adrenocortical carcinoma, but its molecular mechanism of action remains poorly understood. Although mitotane is known to have mitochondrial (mt) effects, a direct link to mt dysfunction has never been established. We examined the functional consequences of mitotane exposure on proliferation, steroidogenesis, and mt respiratory chain, biogenesis and morphology, in two human adrenocortical cell lines, the steroid-secreting H295R line and the non-secreting SW13 line. Mitotane inhibited cell proliferation in a dose- and a time-dependent manner. At the concentration of 50 μM (14 mg/l), which corresponds to the threshold for therapeutic efficacy, mitotane drastically reduced cortisol and 17-hydroxyprogesterone secretions by 70%. This was accompanied by significant decreases in the expression of genes encoding mt proteins involved in steroidogenesis (STAR, CYP11B1, and CYP11B2). In both H295R and SW13 cells, 50 μM mitotane significantly inhibited (50%) the maximum velocity of the activity of the respiratory chain complex IV (cytochrome c oxidase (COX)). This effect was associated with a drastic reduction in steady-state levels of the whole COX complex as revealed by blue native PAGE and reduced mRNA expression of both mtDNA-encoded COX2 (MT-CO2) and nuclear DNA-encoded COX4 (COX4I1) subunits. In contrast, the activity and expression of respiratory chain complexes II and III were unaffected by mitotane treatment. Lastly, mitotane exposure enhanced mt biogenesis (increase in mtDNA content and PGC1α (PPARGC1A) expression) and triggered fragmentation of the mt network. Altogether, our results provide first evidence that mitotane induced a mt respiratory chain defect in human adrenocortical cells.
authors.affiliation: INSERM U693, Fac Med Paris Sud, Rue Gabriel Péri, Le Kremlin-Bicêtre F-94276, France.
authors.forename: Ségolène
authors.initials: S
authors.lastname: Hescot
authors.forename: Abdelhamid
authors.initials: A
authors.lastname: Slama
authors.forename: Anne
authors.initials: A
authors.lastname: Lombès
authors.forename: Angelo
authors.initials: A
authors.lastname: Paci
authors.forename: Hervé
authors.initials: H
authors.lastname: Remy
authors.forename: Sophie
authors.initials: S
authors.lastname: Leboulleux
authors.forename: Rita
authors.initials: R
authors.lastname: Chadarevian
authors.forename: Séverine
authors.initials: S
authors.lastname: Trabado
authors.forename: Larbi
authors.initials: L
authors.lastname: Amazit
authors.forename: Jacques
authors.initials: J
authors.lastname: Young
authors.forename: Eric
authors.initials: E
authors.lastname: Baudin
authors.forename: Marc
authors.initials: M
authors.lastname: Lombès
mesh_terms: D019326:17-alpha-Hydroxyprogesterone / Q000378:metabolism; D000302:Adrenal Cortex / Q000166:cytology; D018931:Antineoplastic Agents, Hormonal / Q000494:pharmacology*; D002460:Cell Line; D004272:DNA, Mitochondrial / Q000378:metabolism; D004579:Electron Transport / Q000187:drug effects; D003576:Electron Transport Complex IV / Q000378:metabolism; D006801:Humans; D006854:Hydrocortisone / Q000378:metabolism; D008928:Mitochondria / Q000187:drug effects* / Q000378:metabolism; D008939:Mitotane / Q000494:pharmacology*
chemical_list: D018931:Antineoplastic Agents, Hormonal; D004272:DNA, Mitochondrial; D019326:17-alpha-Hydroxyprogesterone; D008939:Mitotane; D003576:Electron Transport Complex IV; D006854:Hydrocortisone
keywords: adrenocortical carcinoma; cytochrome c oxidase; mitochondria; mitotane; o,p'-DDD