Stan Silvia D, Zeng Yan, Singh Shivendra V
University of Pittsburgh Cancer Institute, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA.
Nutr Cancer. 2008;60 Suppl 1(Suppl 1):51-60. doi: 10.1080/01635580802381477.
Withaferin A (WA) is derived from the medicinal plant Withania somnifera that has been safely used for centuries in the Indian Ayurvedic medicine for treatment of various ailments. We now demonstrate that WA treatment causes G2 and mitotic arrest in human breast cancer cells. Treatment of MDA-MB-231 (estrogen-independent) and MCF-7 (estrogen-responsive) cell lines with WA resulted in a concentration- and time-dependent increase in G2-M fraction, which correlated with a decrease in levels of cyclin-dependent kinase 1 (Cdk1), cell division cycle 25C (Cdc25C) and/or Cdc25B proteins, leading to accumulation of Tyrosine15 phosphorylated (inactive) Cdk1. Ectopic expression of Cdc25C conferred partial yet significant protection against WA-mediated G2-M phase cell cycle arrest in MDA-MB-231 cells. The WA-treated MDA-MB-231 and MCF-7 cells were also arrested in mitosis as judged by fluorescence microscopy and analysis of Ser10 phosphorylated histone H3. Mitotic arrest resulting from exposure to WA was accompanied by an increase in the protein level of anaphase promoting complex/cyclosome substrate securin. In conclusion, the results of this study suggest that G2-M phase cell cycle arrest may be an important mechanism in antiproliferative effect of WA against human breast cancer cells.
睡茄素A（WA）源自药用植物印度人参，这种植物在印度阿育吠陀医学中已被安全使用了几个世纪，用于治疗各种疾病。我们现在证明，WA处理会导致人乳腺癌细胞出现G2期和有丝分裂停滞。用WA处理MDA-MB-231（雌激素非依赖性）和MCF-7（雌激素反应性）细胞系，会导致G2-M期比例呈浓度和时间依赖性增加，这与细胞周期蛋白依赖性激酶1（Cdk1）、细胞分裂周期25C（Cdc25C）和/或Cdc25B蛋白水平的降低相关，导致酪氨酸15磷酸化（无活性）Cdk1的积累。Cdc25C的异位表达对WA介导的MDA-MB-231细胞G2-M期细胞周期停滞提供了部分但显著的保护。通过荧光显微镜检查和对Ser10磷酸化组蛋白H3的分析判断，经WA处理的MDA-MB-231和MCF-7细胞也停滞在有丝分裂期。暴露于WA导致的有丝分裂停滞伴随着后期促进复合物/细胞周期体底物securin蛋白水平的增加。总之，本研究结果表明，G2-M期细胞周期停滞可能是WA对人乳腺癌细胞抗增殖作用的重要机制。
