Department of Pharmacology & Chemical Biology, University of Pittsburgh Cancer Institute, University of Pittsburgh School of Medicine, 2.32A Hillman Cancer Center Research Pavilion, 5117 Centre Avenue, Pittsburgh, PA 15213, USA.
Breast Cancer Res Treat. 2012 Nov;136(1):45-56. doi: 10.1007/s10549-012-2239-6. Epub 2012 Sep 11.
Ayurvedic medicine plants continue to draw attention for the discovery of novel anticancer agents. Withaferin A (WA) is one such small-molecule constituent of the ayurvedic medicine plant Withania somnifera with efficacy against cultured and xenografted human breast cancer cells. However, the mechanism underlying anticancer effect of WA is not fully understood. This study was undertaken to determine the role of Notch signaling in anticancer effects of WA using human breast cancer cells as a model. Notably, Notch signaling is often hyperactive in human breast cancers. Exposure of MDA-MB-231 and MCF-7 human breast cancer cells to pharmacological concentrations of WA resulted in cleavage (activation) of Notch2 as well as Notch4, which was accompanied by transcriptional activation of Notch as evidenced by RBP-Jk, HES-1A/B, and HEY-1 luciferase reporter assays. On the other hand, WA treatment caused a decrease in levels of both transmembrane and cleaved Notch1. The WA-mediated activation of Notch was associated with induction of γ-secretase complex components presenilin1 and/or nicastrin. Inhibition of MDA-MB-231 and MDA-MB-468 cell migration resulting from WA exposure was significantly augmented by knockdown of Notch2 as well as Notch4 protein. Activation of Notch2 was not observed in cells treated with withanone or withanolide A, which are structural analogs of WA. The results of this study indicate that WA treatment activates Notch2 and Notch4, which impede inhibitory effect of WA on breast cancer cell migration.
阿育吠陀医学植物继续引起人们的关注，因为它们是新型抗癌药物的发现来源。Withaferin A（WA）是一种来自于阿育吠陀医学植物 Withania somnifera 的小分子成分，对培养的和异种移植的人乳腺癌细胞具有疗效。然而，WA 的抗癌作用机制尚未完全阐明。本研究旨在使用人乳腺癌细胞作为模型，确定 Notch 信号通路在 WA 的抗癌作用中的作用。值得注意的是，Notch 信号通路在人类乳腺癌中经常过度活跃。用药理浓度的 WA 处理 MDA-MB-231 和 MCF-7 人乳腺癌细胞，导致 Notch2 和 Notch4 的切割（激活），这伴随着 Notch 的转录激活，如 RBP-Jk、HES-1A/B 和 HEY-1 荧光素酶报告基因检测所示。另一方面，WA 处理导致跨膜和切割的 Notch1 水平降低。WA 介导的 Notch 激活与 γ-分泌酶复合物成分早老素 1 和/或尼克酰胺酶的诱导有关。WA 暴露导致 MDA-MB-231 和 MDA-MB-468 细胞迁移减少，这种减少通过 Notch2 和 Notch4 蛋白的敲低显著增强。用结构类似物 withanone 或 withanolide A 处理的细胞中没有观察到 Notch2 的激活。本研究的结果表明，WA 处理激活 Notch2 和 Notch4，这阻碍了 WA 对乳腺癌细胞迁移的抑制作用。
