表没食子儿茶素没食子酸酯抑制胃癌生长和血管生成及其分子机制的研究

Epigallocatechin-3-gallate inhibits growth and angiogenesis of gastric cancer and its molecular mechanism

目的探讨表没食子儿茶素没食子酸酯（EGCG）抑制胃癌生长和血管生成的分子机制。方法建立裸鼠异位胃癌肿瘤模型．检测肿瘤生长及肿瘤组织微血管密度（MVD）。培养SGC-7901胃癌细胞．Western印迹方法检测肿瘤细胞及其组织血管内皮生长因子（VEGF）、总信号转导、转录活化因子（Star3）和磷酸化形式Stat3的表达，同时采用ELISA方法检测肿瘤细胞培养液中VEGF蛋白水平．RT-PCR方法检测胃癌细胞VEGFmRNA的表达水平。结果EGCG组肿瘤组织平均质量（0．32±0．08）g，显著低于对照组（0．81±0．12）g，t=7．24，P〈0．01。EGCG组平均肿瘤抑制率为（60．4±6．1）％：其肿瘤生长曲线也显著低于对照组、EGCG组的肿瘤组织MVD（15．2±4．3）也显著低于对照组（24．6±6．6）（t=3．41，P〈0．01）。EGCG组胃癌组织的VEGF表达也减少78．6％．并呈剂量依赖性地下降：其肿瘤组织中Stat3磷酸化活化也减少了53．5％，也呈剂量依赖性地下降：但并未影响总的Stat3表达。结论EGCG通过抑制Stat3活化减少胃癌细胞VEGF表达．从而抑制胃癌生长和血管生成。

Objective To investigate the inhibitory effect of epigallocatechin-3-gallate （EGCG） on growth and angiogenesis of gastric cancer and to explore its molecular mechanism. Methods Heterotopic tumor was established by subcutaneously injection with SGC-7901 cells in nude mice. Once the tumor was established, the mice were allocated randomly into two groups and received intraperitoneal injection of EGCG or phosphate buffered saline respectively. Tumor growth was measured hy caliper in two dimensions, and angiogenesis was determined with tumor microvessel density （MVD） by immunohistochemistry. Protein levels of vascular endothelial growth factor （VEGF） and activation of signal transducer and activator of transcription 3 （Stat3） in tumor cells and tumor tissues were examined by Western blot. VEGF release in tumor culture medium was determined by ELISA and VEGF mRNA expression in tumor cells by RT-PCR. Results Intraperitoneal injection of EGCG significantly inhibited the growth of gastric cancer [ （0.32±0.08） g vs （0.81±0.12 ） g, t=7.24, P〈 0.01 ], and an average of 60.4% suppression of primary tumor growth was observed. Microvessel density in tumor tissues receiving EGCG treatment was also markedly reduced（15.2±4.3 vs 24.6±6.6, t=3.41, P〈0.01）, and an average of 38.2% suppression was observed. EGCG treatment markedly reduced VEGF protein level in vitro and in vivo. Secretion and mRNA expression of VEGF in tumor cells were also suppressed by EGCG in a dose-dependent manner. This inhibitory effect was associated with reduced activation of Stat3. Star3 activation was dose-dependently suppressed by EGCG in tumor cells, and an average of 53.5% reduction was observed in tumor tissues, but EGCG treatment did not change total Star3 expression. Conclusion EGCG reduces expression of VEGF in gastric cancer by inhibiting activation of Stat3, thereby inhibits tumor growth and angiogenesis of gastric cancer.