Regorafenib, a multiple kinase inhibitor, is recently approved for treatment of patients with advanced hepatocellular carcinoma (HCC). Previous studies demonstrated that regorafenib was a mitochondrial toxicant, which associated with the impairment of mitochondria. Sirt3 is involved in the regulation of mitochondrial function in cancers. This study aimed to investigate the mechanism of Sirt3 involved in the mitochondrial dysfunction which associated with regorafenib treatment in liver cancer cells. We found regorafenib inhibited Sirt3 and p-ERK expression in HCC cells in a dose-dependent manner. Bioinformatics analysis showed that Sirt3 expression was down-regulated in liver cancer tissues and its low expression was correlated with worse overall survival (OS) in liver cancer patients. After transfected with Sirt3 overexpression plasmid, we found that Sirt3 sensitized liver cancer cells to regorafenib and resulted in much more apoptosis with a significant increase of ROS level. However, exogenous antioxidant could not weaken the apoptosis. Mitochondrial membrane potential assay indicated that Sirt3 overexpression accelerated the mitochondrial depolarization process induced by regorafenib and aggravated mitochondrial injury. Cellular oxygen consumption assay showed that mitochondrial dysfunction was caused by the damage of the electron transport chain. The results demonstrated that Sirt3 overexpression promoted the increase of ROS and apoptosis induced by regorafenib through the acceleration of mitochondrial dysfunction by impairing function of the electron transport chain in liver cancer cells. Our studies verified the functional role of Sirt3 in regorafenib treatment and suggested that regorafenib accompanied with Sirt3 activator as a novel treatment strategy for HCC.

Regorafenib是一种多激酶抑制剂，最近被批准用于治疗晚期肝细胞癌（HCC）患者。先前的研究表明雷戈非尼是一种线粒体毒物，与线粒体损伤有关。Sirt3参与癌症线粒体功能的调节。这项研究旨在探讨Sirt3参与线粒体功能异常的机制，该功能与肝癌细胞中瑞格非尼的治疗有关。我们发现雷戈非尼以剂量依赖性方式抑制HCC细胞中Sirt3和p-ERK的表达。生物信息学分析表明，Sirt3表达在肝癌组织中下调，而其低表达与肝癌患者较差的总体生存率（OS）相关。用Sirt3过表达质粒转染后，我们发现Sirt3使肝癌细胞对regorafenib敏感并导致更多的细胞凋亡，且ROS水平显着增加。但是，外源抗氧化剂不能减弱细胞凋亡。线粒体膜电位测定表明，Sirt3过表达加速了雷戈非尼引起的线粒体去极化过程，并加剧了线粒体损伤。细胞耗氧量测定表明线粒体功能障碍是由电子传输链的损伤引起的。结果表明，Sirt3的过表达通过损害肝癌细胞中电子传输链的功能，加速线粒体功能障碍，从而促进了雷戈非尼诱导的ROS和细胞凋亡的增加。