Key Laboratory for Molecular Enzymology and Engineering of the Ministry of Education, College of Life Science, Jilin University, Changchun, 130012, China.
Protein Cell. 2014 Mar;5(3):224-34. doi: 10.1007/s13238-014-0027-2. Epub 2014 Mar 13.
We have recently reported that Ginsenoside Rh2 (G-Rh2) induces the activation of two initiator caspases, caspase-8 and caspase-9 in human cancer cells. However, the molecular mechanism of its death-inducing function remains unclear. Here we show that G-Rh2 stimulated the activation of both caspase-8 and caspase-9 simultaneously in HeLa cells. Under G-Rh2 treatment, membrane death receptors Fas and TNFR1 are remarkably upregulated. However, the induced expression of Fas but not TNFR1 was contributed to the apoptosis process. Moreover, significant increases in Fas expression and caspase-8 activity temporally coincided with an increase in p53 expression in p53-non-mutated HeLa and SK-HEP-1 cells upon G-Rh2 treatment. In contrast, Fas expression and caspase-8 activity remained constant with G-Rh2 treatment in p53-mutated SW480 and PC-3 cells. In addition, siRNA-mediated knockdown of p53 diminished G-Rh2-induced Fas expression and caspase-8 activation. These results indicated that G-Rh2-triggered extrinsic apoptosis relies on p53-mediated Fas over-expression. In the intrinsic apoptotic pathway, G-Rh2 induced strong and immediate translocation of cytosolic BAK and BAX to the mitochondria, mitochondrial cytochrome c release, and subsequent caspase-9 activation both in HeLa and in SW480 cells. p53-mediated Fas expression and subsequent downstream caspase-8 activation as well as p53-independent caspase-9 activation all contribute to the activation of the downstream effector caspase-3/-7, leading to tumor cell death. Taken together, we suggest that G-Rh2 induces cancer cell apoptosis in a multi-path manner and is therefore a promising candidate for anti-tumor drug development.
我们最近报道人参皂甙 Rh2（G-Rh2）诱导人癌细胞中两种起始半胱天冬酶（caspase-8 和 caspase-9）的激活。然而，其诱导细胞死亡的功能的分子机制尚不清楚。在这里，我们显示 G-Rh2 可同时刺激 HeLa 细胞中 caspase-8 和 caspase-9 的激活。在 G-Rh2 处理下，膜死亡受体 Fas 和 TNFR1 显著上调。然而，诱导 Fas 的表达而不是 TNFR1 的表达有助于凋亡过程。此外，在 G-Rh2 处理下，p53 非突变的 HeLa 和 SK-HEP-1 细胞中 Fas 表达和 caspase-8 活性的显著增加与 p53 表达的增加同时发生。相比之下，在 p53 突变的 SW480 和 PC-3 细胞中，Fas 表达和 caspase-8 活性在 G-Rh2 处理下保持不变。此外，siRNA 介导的 p53 敲低减弱了 G-Rh2 诱导的 Fas 表达和 caspase-8 激活。这些结果表明，G-Rh2 触发的外源性细胞凋亡依赖于 p53 介导的 Fas 过表达。在内在凋亡途径中，G-Rh2 诱导细胞质 BAK 和 BAX 迅速向线粒体转位、线粒体细胞色素 c 释放以及 caspase-9 在 HeLa 和 SW480 细胞中的随后激活。p53 介导的 Fas 表达和随后下游 caspase-8 的激活以及 p53 非依赖性 caspase-9 的激活都有助于下游效应 caspase-3/-7 的激活，导致肿瘤细胞死亡。总之，我们认为 G-Rh2 通过多种途径诱导癌细胞凋亡，因此是开发抗肿瘤药物的有前途的候选药物。
