Zhu Bao-he, He Yu-long, Zhan Wen-hua, Cai Shi-rong, Wang Zhao, Zhang Chang-hua, Chen Hua-yun
Department of Gastrointestinopancreatic Surgery, Sun Yat-sen University, Guangzhou 510080, China.
Zhonghua Wei Chang Wai Ke Za Zhi. 2011 Aug;14(8):631-5.
To investigate the molecular mechanism involved in the downregulation of vascular endothelial growth factor(VEGF) expression through the suppression of signal transducer and activator of transcription 3(Stat3) by(-)-Epigallocatechin-3-gallate (EGCG).
After human gastric cancer cells (AGS) were treated with IL-6 (50 μg/L) and EGCG(0, 5, 10, 25 or 50 μmol/L), the expression levels of VEGF, total Stat3(tStat3), and activated Stat3(pStat3) in tumor cells were examined by Western blotting. The influence of the inhibitor of Stat3 pathway on the IL-6-induced VEGF expression was investigated. VEGF protein level in tumor cell culture medium was determined by ELISA and VEGF mRNA expression in tumor cells by RT-PCR. Tumor cell nuclear extract was prepared and nuclear expression of pStat3 was detected. Stat3-DNA binding activity was examined with chromatin immunoprecipitation (ChIP) assay.
IL-6 significantly increased VEGF expression in AGS gastric cancer cells. Compared with the group without IL-6, the expression and secretion of VEGF protein, and mRNA expression increased by 2.4 fold,2.8 fold, and 3.1 fold(all P<0.01), respectively. EGCG treatment markedly reduced VEGF protein, release and mRNA expression in a dose-dependent manner. When compared with the control group induced by IL-6, EGCG and AG490(a Stat3 pathway inhibitor) significantly inhibited VEGF expression induced by IL-6 (P<0.01). EGCG dose-dependently inhibited pStat3 induced by IL-6(P<0.05), but not tStat3 (P>0.05). Stat3 nuclear translocation and Stat3-DNA binding activity in AGS cells or that induced by IL-6 were directly inhibited by EGCG(P<0.05).
EGCG reduces expression of VEGF in gastric cancer cells through the inhibition of Stat3 activity.
研究（-）-表没食子儿茶素-3-没食子酸酯（EGCG）通过抑制信号转导和转录激活因子3（Stat3）来下调血管内皮生长因子（VEGF）表达的分子机制。
用人胃癌细胞（AGS）分别用白细胞介素-6（IL-6，50μg/L）和EGCG（0、5、10、25或50μmol/L）处理后，通过蛋白质印迹法检测肿瘤细胞中VEGF、总Stat3（tStat3）和活化Stat3（pStat3）的表达水平。研究Stat3信号通路抑制剂对IL-6诱导的VEGF表达的影响。通过酶联免疫吸附测定（ELISA）法测定肿瘤细胞培养基中VEGF蛋白水平，通过逆转录-聚合酶链反应（RT-PCR）检测肿瘤细胞中VEGF mRNA表达。制备肿瘤细胞核提取物并检测pStat3的核表达。用染色质免疫沉淀（ChIP）试验检测Stat3与DNA的结合活性。
IL-6显著增加AGS胃癌细胞中VEGF的表达。与无IL-6组相比，VEGF蛋白的表达和分泌以及mRNA表达分别增加了2.4倍、2.8倍和3.1倍（均P<0.01）。EGCG处理以剂量依赖性方式显著降低VEGF蛋白、释放量和mRNA表达。与IL-6诱导的对照组相比，EGCG和AG490（一种Stat3信号通路抑制剂）显著抑制IL-6诱导的VEGF表达（P<0.01）。EGCG以剂量依赖性方式抑制IL-6诱导的pStat3（P<0.05），但不抑制tStat3（P>0.05）。EGCG直接抑制AGS细胞中或IL-6诱导的Stat3核转位和Stat3与DNA的结合活性（P<0.05）。
EGCG通过抑制Stat3活性降低胃癌细胞中VEGF的表达。
