Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore.
Cell Death Dis. 2013 Apr 4;4(4):e568. doi: 10.1038/cddis.2013.103.
Although statins are known to inhibit proliferation and induce death in a number of cancer cell types, the mechanisms through which downregulation of the mevalonate (MVA) pathway activates death signaling remain poorly understood. Here we set out to unravel the signaling networks downstream of the MVA pathway that mediate the death-inducing activity of simvastatin. Consistent with previous reports, exogenously added geranylgeranylpyrophosphate, but not farnesylpyrophosphate, prevented simvastatin's growth-inhibitory effect, thereby suggesting the involvement of geranylgeranylated proteins such as Rho GTPases in the anticancer activity of simvastatin. Indeed, simvastatin treatment led to increased levels of unprenylated Ras homolog gene family, member A (RhoA), Ras-related C3 botulinum toxin substrate 1 (Rac1) and cell division cycle 42 (Cdc42). Intriguingly, instead of inhibiting the functions of Rho GTPases as was expected with loss of prenylation, simvastatin caused a paradoxical increase in the GTP-bound forms of RhoA, Rac1 and Cdc42. Furthermore, simvastatin disrupted the binding of Rho GTPases with the cytosolic inhibitor Rho GDIα, which provides a potential mechanism for GTP loading of the cytosolic Rho GTPases. We also show that the unprenylated RhoA- and Rac1-GTP retained at least part of their functional activities, as evidenced by the increase in intracellular superoxide production and JNK activation in response to simvastatin. Notably, blocking superoxide production attenuated JNK activation as well as cell death induced by simvastatin. Finally, we provide evidence for the involvement of the B-cell lymphoma protein 2 family, Bcl-2-interacting mediator (Bim), in a JNK-dependent manner, in the apoptosis-inducing activity of simvastatin. Taken together, our data highlight the critical role of non-canonical regulation of Rho GTPases and involvement of downstream superoxide-mediated activation of JNK pathway in the anticancer activity of simvastatin, which would have potential clinical implications.
尽管他汀类药物已被证实能够抑制多种癌细胞类型的增殖并诱导其死亡，但下调甲羟戊酸（MVA）途径激活死亡信号的机制仍知之甚少。在这里，我们着手揭示介导辛伐他汀诱导死亡活性的 MVA 途径下游信号网络。与先前的报道一致，外源性添加香叶基香叶基焦磷酸，但不是法呢基焦磷酸，可防止辛伐他汀的生长抑制作用，从而表明 geranylgeranylated 蛋白（如 Rho GTPases）参与了辛伐他汀的抗癌活性。事实上，辛伐他汀处理导致未prenylated Ras 同源基因家族，成员 A（RhoA），Ras 相关 C3 肉毒杆菌毒素底物 1（Rac1）和细胞分裂周期 42（Cdc42）水平升高。有趣的是，与预期的失prenylation 抑制 Rho GTPases 功能相反，辛伐他汀导致 RhoA、Rac1 和 Cdc42 的 GTP 结合形式呈悖论性增加。此外，辛伐他汀破坏了 Rho GTPases 与胞质抑制剂 Rho GDIα 的结合，这为胞质 Rho GTPases 的 GTP 加载提供了一种潜在机制。我们还表明，未prenylated 的 RhoA 和 Rac1-GTP 保留了至少部分功能活性，这表现为细胞内超氧化物产生和 JNK 激活增加，对辛伐他汀有反应。值得注意的是，阻断超氧化物产生可减弱 JNK 激活以及辛伐他汀诱导的细胞死亡。最后，我们提供了证据表明 B 细胞淋巴瘤蛋白 2 家族，Bcl-2 相互作用调节剂（Bim），以 JNK 依赖性方式参与辛伐他汀诱导的细胞凋亡。总之，我们的数据强调了非典型调节 Rho GTPases 的关键作用以及下游超氧化物介导的 JNK 途径的激活在辛伐他汀抗癌活性中的作用，这将具有潜在的临床意义。
