Department of Pharmaco-Biology, Centro Sanitario, Faculty of Pharmacy Nutritional and Health Sciences, University of Calabria, Arcavacata di Rende, Cosenza, Italy.
Cell Cycle. 2011 Jul 15;10(14):2344-54. doi: 10.4161/cc.10.14.15917.
The combined treatment with nanomolar doses of the PPARγ ligand Rosiglitazone (BRL) and the RXR ligand 9-cis‑retinoic acid (9RA) induces a p53-dependent apoptosis in MCF7, SKBR3 and T47D human breast cancer cells. Since MCF7 cells express a wild-type p53 protein, while SKBR3 and T47D cells harbor endogenous mutant p53, we elucidated the mechanism through which PPARγ and RXR ligands triggered apoptotic processes independently of p53 transcriptional activity. We showed an upregulation of Bid expression enhancing the association between Bid/p53 in both cytosol and mitochondria after the ligand treatment. Particularly in the mitochondria, the complex involves the truncated Bid that plays a key role in the apoptotic process induced by BRL and 9RA, since the disruption of mitochondrial membrane potential, the induction of PARP cleavage and the percentage of TUNEL-positive cells were reversed after knocking down Bid. Moreover, PPARγ and RXR ligands were able to reduce mitochondrial GST activity, which was no longer noticeable silencing Bid expression, suggesting the potential of Bid in the regulation of mitochondrial intracellular reactive oxygen species scavenger activity. Our data, providing new insight into the role of p53/Bid complex at the mitochondria in promoting breast cancer cell apoptosis upon low doses of PPARγ and RXR ligands, address Bid as a potential target in the novel therapeutical strategies for breast cancer.
纳摩尔浓度的过氧化物酶体增殖物激活受体 γ（PPARγ）配体罗格列酮（BRL）与视黄酸受体 RXR 配体 9-顺式维甲酸（9RA）联合治疗可诱导 MCF7、SKBR3 和 T47D 人乳腺癌细胞发生 p53 依赖性细胞凋亡。由于 MCF7 细胞表达野生型 p53 蛋白，而 SKBR3 和 T47D 细胞则含有内源性突变型 p53，因此我们阐明了 PPARγ 和 RXR 配体触发凋亡过程而不依赖于 p53 转录活性的机制。我们发现，配体处理后，Bid 表达上调，增强了细胞质和线粒体中 Bid/p53 的结合。特别是在线粒体中，涉及截断的 Bid，它在 BRL 和 9RA 诱导的凋亡过程中起着关键作用，因为破坏线粒体膜电位、诱导 PARP 切割和 TUNEL 阳性细胞的百分比在敲低 Bid 后均得到逆转。此外，PPARγ 和 RXR 配体能够降低线粒体 GST 活性，而沉默 Bid 表达则不再可见，这表明 Bid 在调节线粒体细胞内活性氧清除剂活性方面具有潜在作用。我们的数据为 p53/Bid 复合物在低剂量的 PPARγ 和 RXR 配体诱导乳腺癌细胞凋亡过程中在线粒体中的作用提供了新的见解，提示 Bid 可能成为乳腺癌新治疗策略的潜在靶点。
