Endocrinology Unit, Department of Experimental and Clinical Biomedical Sciences, Research Unit of Histology and Embryology, University of Florence, Viale Pieraccini 6, Florence, Italy.
Endocr Relat Cancer. 2013 Jun 27;20(4):537-50. doi: 10.1530/ERC-13-0150. Print 2013 Aug.
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 μM) 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.
目前，米托坦（MTT）是治疗晚期肾上腺皮质癌（ACC）的一线药物治疗方法。尽管有明确的证据表明该药物可以减少分泌性 ACC 中类固醇过多的临床症状，但介导 MTT 对肿瘤细胞可能产生的毒性作用的机制仍不清楚。本研究通过研究人肾上腺皮质癌细胞系 H295R 和 SW13 中线粒体形态和功能的定性和定量变化，研究了 MTT 毒性作用的细胞内事件。随着药物浓度的增加，MTT 迅速在细胞内积累并转化。在与治疗窗（30-50μM）相对应的剂量下，通过涉及半胱天冬酶 3/7 的凋亡机制，出现细胞生长抑制和细胞毒性作用。对细胞线粒体的电子显微镜分析显示，MTT 诱导的细胞器形态改变呈剂量和时间依赖性。这些变化的特征是明显肿胀和呼吸嵴数量减少，同时线粒体膜电位显著去极化，最终导致细胞器破裂。由于线粒体膜损伤，观察到耗氧量急剧减少，同时 VDAC1 整合膜通道的水平降低。这些发现有助于更好地了解 MTT 在 ACC 细胞中的细胞内作用机制，表明其细胞毒性作用似乎主要是通过激活由线粒体破坏引起的凋亡过程来介导的。
