Kameyama Kazuhisa, Motoyama Keiichi, Tanaka Nao, Yamashita Yuki, Higashi Taishi, Arima Hidetoshi
Department of Physical Pharmaceutics, Graduate School of Pharmaceutical Sciences.
Program for Leading Graduate Schools "HIGO (Health Life Science: Interdisciplinary and Glocal Oriented) Program," Kumamoto University, Kumamoto, Japan.
Int J Nanomedicine. 2017 Apr 28;12:3433-3446. doi: 10.2147/IJN.S133482. eCollection 2017.
Mitophagy is the specific autophagic elimination system of mitochondria, which regulates cellular survival via the removal of damaged mitochondria. Recently, we revealed that folate-appended methyl-β-cyclodextrin (FA-M-β-CyD) provides selective antitumor activity in folate receptor-α (FR-α)-expressing cells by the induction of autophagy. In this study, to gain insight into the detailed mechanism of this antitumor activity, we focused on the induction of mitophagy by the treatment of FR-α-expressing tumor cells with FA-M-β-CyD. In contrast to methyl-β-cyclodextrin, FA-M-β-CyD entered KB cells, human epithelial cells from a fatal cervical carcinoma (FR-α (+)) through FR-α-mediated endocytosis. The transmembrane potential of isolated mitochondria after treatment with FA-M-β-CyD was significantly elevated. In addition, FA-M-β-CyD lowered adenosine triphosphate (ATP) production and promoted reactive oxygen species production in KB cells (FR-α (+)). Importantly, FA-M-β-CyD enhanced light chain 3 (LC3) conversion (LC3-I to LC3-II) in KB cells (FR-α (+)) and induced PTEN-induced putative kinase 1 (PINK1) protein expression, which is involved in the induction of mitophagy. Furthermore, FA-M-β-CyD had potent antitumor activity in BALB/c mice xenografted with KB cells (FR-α (+)) without any significant side effects. Taken together, these findings demonstrate that the autophagic cell death elicited by FA-M-β-CyD could be associated with mitophagy induced by an impaired mitochondrial function.
线粒体自噬是线粒体特有的自噬清除系统，通过清除受损线粒体来调节细胞存活。最近，我们发现叶酸修饰的甲基-β-环糊精（FA-M-β-CyD）通过诱导自噬在表达叶酸受体-α（FR-α）的细胞中提供选择性抗肿瘤活性。在本研究中，为深入了解这种抗肿瘤活性的详细机制，我们聚焦于用FA-M-β-CyD处理表达FR-α的肿瘤细胞所诱导的线粒体自噬。与甲基-β-环糊精不同，FA-M-β-CyD通过FR-α介导的内吞作用进入KB细胞，即来自致命宫颈癌的人上皮细胞（FR-α(+)）。用FA-M-β-CyD处理后分离线粒体的跨膜电位显著升高。此外，FA-M-β-CyD降低了KB细胞（FR-α(+)）中的三磷酸腺苷（ATP）生成并促进了活性氧的产生。重要的是，FA-M-β-CyD增强了KB细胞（FR-α(+)）中的轻链3（LC3）转化（LC3-I向LC3-II）并诱导了参与线粒体自噬诱导的PTEN诱导的假定激酶1（PINK1）蛋白表达。此外，FA-M-β-CyD在接种了KB细胞（FR-α(+)）的BALB/c小鼠中具有强大的抗肿瘤活性，且无任何明显副作用。综上所述，这些发现表明FA-M-β-CyD引发的自噬性细胞死亡可能与线粒体功能受损诱导的线粒体自噬有关。
