Journal of Shangluo University, 2013, 18(11):13200-13217.

Genistein Enhances the Radiosensitivity of Breast Cancer Cells via G2/M Cell Cycle Arrest and Apoptosis

Xiongxiong Liu, Chao Sun, Xiaodong Jin, et al

Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000, Gansu, China

The aim of the present study was to investigate the radiosensitizing effect of genistein, and the corresponding mechanisms of action on breast cancer cells with different estrogen receptor (ER) status. Human breast cancer cell lines such as MCF-7 (ER-positive, harboring wild-type p53) and MDA-MB-231 (ER-negative, harboring mutant p53) were irradiated with X-rays in the presence or absence of genistein. Cell survival, DNA damage and repair, cell cycle distribution, cell apoptosis, expression of proteins related to G₂/M cell cycle checkpoint and apoptosis were measured with colony formation assays, immunohistochemistry, flow cytometry and western blot analysis, respectively. Genistein showed relatively weak toxicity to both cell lines at concentrations in the range of 5-20 μM. Using the dosage of 10 μM genistein, the sensitizer enhancement ratios after exposure to X-rays at a 10% cell survival (IC₁₀) were 1.43 for MCF-7 and 1.36 for MDA-MB-231 cells, respectively. Significantly increased DNA damages, arrested cells at G₂/M phase, decreased homologous recombination repair protein Rad51 foci formation and enhanced apoptotic rates were observed in both cell lines treated by genistein combined with X-rays compared with the irradiation alone. The combined treatment obviously up-regulated the phosphorylation of ATM, Chk2, Cdc25c and Cdc2, leading to permanent G₂/M phase arrest, and up-regulated Bax and p73, down-regulated Bcl-2, finally induced mitochondria-mediated apoptosis in both cell lines. These results suggest that genistein induces G₂/M arrest by the activation of the ATM/Chk2/Cdc25C/Cdc2 checkpoint pathway and ultimately enhances the radiosensitivity of both ER+ and ER- breast cancer cells through a mitochondria-mediated apoptosis pathway.

中国《商洛学院学报》，2013年11月

金雀异黄素通过 G2/M 期细胞周期中止和细胞凋亡提高乳腺癌细胞的放射敏感性

刘雄雄， 孙超，金晓东，等

中国甘肃兰州中国科学院现代物理学研究所

本研究旨在探讨金雀异黄素的增敏作用，以及对具有不同雌激素受体 (ER) 状态的乳腺癌细胞相应的行动机制。在金雀异黄素存在与否的情况下对人体乳腺癌细胞例如 MCF-7 （ER-阳性，隐匿野生型 p53） 和MDA-MB-231 （ER 阴性，隐匿突变型 p53） 进行X 射线辐照。用菌落形成测定、 免疫组化、 流式细胞仪和免疫印迹分析，分别测定细胞存活率、 DNA 损伤与修复，细胞周期分布，细胞凋亡、 G₂/M 期细胞周期检查点相关蛋白的表达和细胞凋亡。浓度范围内在 5-20 μ M的金雀异黄素表现出相对对这两种细胞较弱的毒性。使用 10 μM 金雀异黄素的用量，在接触X 射线后增敏剂增强比例在 10%细胞生存率 (IC₁₀)的分别为MCF-7的1.43 和 MDA-MB-231 细胞的 1.36。与单独照射治疗相比，在用金雀异黄素联合X射线治疗两种细胞时，观察到显著提高 DNA 的损伤作用，中止 G₂/M 期细胞，降低同源重组修复蛋白 Rad51 中心的形成，提高细胞凋亡率。联合治疗明显上调了 ATM、 Chk2、 Cdc25c 和 Cdc2的磷酸化，导致永久 G₂/M 期阻滞，上调 Bax 和 p73，下调 Bcl-2，最后诱导在这两种细胞中线粒体介导的细胞凋亡。这些结果表明，金雀异黄素诱导 G₂/M 期阻滞的通过ATM/Chk2/Cdc25C/Cdc2 检查点途径的活化并最终提高ER +、 ER 乳腺癌细胞的放射增敏性，通过线粒体介导的细胞凋亡途径。