Wang Yufang, Lv Junping, Cheng Yao, Du Jipei, Chen Degao, Li Chengtao, Zhang Ji
Department of Pathophysiology, School of Preclinical and Forensic Medicine, Sichuan University, Chengdu, P.R. China.
Department of Pharmacology, Beijing Institute of Biomedicine, Beijing, P.R. China.
PLoS One. 2015 Apr 10;10(4):e0124812. doi: 10.1371/journal.pone.0124812. eCollection 2015.
Melanoma is an aggressive skin cancer. Unfortunately, there is currently no chemotherapeutic agent available to significantly prolong the survival of the most patients with metastatic melanomas. Here we report that the Ginkgo biloba extract (EGb761), one of the most widely sold herbal supplements in the world, potently induces apoptosis in human melanoma cells by disturbing the balance between pro- and anti-apoptosis Bcl-2 family proteins. Treatment with EGb761 induced varying degrees of apoptosis in melanoma cell lines but not in melanocytes. Induction of apoptosis was caspase-dependent and appeared to be mediated by the mitochondrial pathway, in that it was associated with reduction in mitochondrial membrane potential and activation of Bax and Bak. Although EGb761 did not cause significant change in the expression levels of the BH3-only Bcl-2 family proteins Bim, Puma, Noxa, and Bad, it significantly downregulated Mcl-1 in sensitive but not resistant melanoma cells, suggesting a major role of Mcl-1 in regulating apoptosis of melanoma cells induced by EGb761. Indeed, siRNA knockdown of Mcl-1 enhanced EGb761-induced apoptosis, which was associated with increased activation of Bax and Bak. Taken together, these results demonstrate that EGb761 kills melanoma cells through the mitochondrial apoptotic pathway, and that Mcl-1 is a major regulator of sensitivity of melanoma cells to apoptosis induced by EGb761. Therefore, EGb761 with or without in combination with targeting Mcl-1 may be a useful strategy in the treatment of melanoma.
黑色素瘤是一种侵袭性皮肤癌。不幸的是,目前尚无化疗药物可显著延长大多数转移性黑色素瘤患者的生存期。在此我们报告,银杏叶提取物(EGb761)是世界上销售最广泛的草药补充剂之一,它通过扰乱促凋亡和抗凋亡Bcl-2家族蛋白之间的平衡,有效诱导人黑色素瘤细胞凋亡。用EGb761处理可在黑色素瘤细胞系中诱导不同程度的凋亡,但对黑素细胞无此作用。凋亡的诱导是半胱天冬酶依赖性的,且似乎由线粒体途径介导,因为它与线粒体膜电位降低以及Bax和Bak的激活有关。尽管EGb761并未引起仅含BH3结构域的Bcl-2家族蛋白Bim、Puma、Noxa和Bad表达水平的显著变化,但它在敏感而非耐药的黑色素瘤细胞中显著下调了Mcl-1,这表明Mcl-1在调节EGb761诱导的黑色素瘤细胞凋亡中起主要作用。事实上,Mcl-1的小干扰RNA敲低增强了EGb761诱导的凋亡,这与Bax和Bak的激活增加有关。综上所述,这些结果表明EGb761通过线粒体凋亡途径杀死黑色素瘤细胞,且Mcl-1是黑色素瘤细胞对EGb761诱导凋亡敏感性的主要调节因子。因此,单独或联合靶向Mcl-1的EGb761可能是治疗黑色素瘤的一种有效策略。