Morphofunctional effects of mitotane on mitochondria in human adrenocortical cancer cells

Abstract

At present, mitotane (MTT) represents the first-line pharmacological approach for the treatment of advanced adrenocortical carcinoma (ACC). Despite clear evidence that the drug can reduce the clinical signs of steroid excess in secreting ACC, the mechanism mediating the possible toxic effect of MTT on tumor cells still remains obscure. This study investigated the intracellular events underlying the toxic effect of MTT by studying qualitative and quantitative alterations in mitochondrial morphology and functions in human adrenocortical cancer cell lines, H295R and SW13. Increasing concentrations of MTT resulted in rapid intracellular accumulation and conversion of the drug. Cytostatic and cytotoxic effects were evident at doses corresponding to the therapeutic window (30-50 mM) through an apoptotic mechanism involving caspase 3/7. Electron microscopic analysis of cell mitochondria displayed MTT-induced dose-and time-dependent alterations in the morphology of the organelle. These alterations were characterized by a marked swelling and a decrease in the number of respiratory cristae, accompanied by a significant depolarization of the mitochondrial membrane potential, finally leading to the disruption of the organelle. A drastic reduction of oxygen consumption was observed due to mitochondrial membrane damage, which was accompanied by a decrease in the levels of VDAC1 integral membrane channel. These findings contribute to better understand the intracellular mechanism of action of MTT in ACC cells, showing that its cytotoxic effect seems to be mainly mediated by an apoptotic process activated by the disruption of mitochondria.

EJE PRIZE 2014: Current and evolving treatment options in adrenocortical carcinoma: where do we stand and where do we want to go?

“…This was confirmed to some extent in cell culture suggesting that down-regulation of the mitochondrial respiratory chain might be involved in the cytotoxic effect of the drug (37,38). We personally have some doubts if the covalent binding of a mitotane intermediate to mitochondrial proteins is actually causative of decreased steroid synthesis and cell death in ACCs as i) in the original report, protein adducts have been mainly found in non-human adrenocortical tissue and only weakly in NCI-H295 cells, ii) these presumed adducts have never been identified, and iii) alterations of the respiratory chain also occur during apoptosis which may be triggered by completely separate pathways.…”

ATR-101 disrupts mitochondrial functions in adrenocortical carcinoma cells and in vivo

“…Many inhibitors of electron transport as well as of F1F0-ATPase cause cell death under conditions that require respiration, but not under glycolytic conditions (Marroquin et al 2007; Poli, et al 2013; Tettamanti, et al 2008). Numerous inhibitors of oxidative phosphorylation have been investigated as potential anti-cancer agents (Rohlena, et al 2013).…”

The proteomic 2D-DIGE approach reveals the protein voltage-dependent anion channel 2 as a potential therapeutic target in epithelial thyroid tumours

“…Besides VDAC2, we also detected VDAC1 in the human epithelial thyroid tumours and in the thyroid cell lines. In 2010, Koren et al showed that this isoform is essential for normal growth of tumoural cells, and that silencing VDAC1 expression in T-Rex-293 cells by means of RNA interference reduced ATP production and decreased cell growth (Koren et al, 2010).…”