Garbisa S, Sartor L, Biggin S, Salvato B, Benelli R, Albini A
Department of Experimental Biomedical Sciences, Medical School, University of Padova, viale G. Colombo 3, 35121 Padova, Italy.
Cancer. 2001 Feb 15;91(4):822-32. doi: 10.1002/1097-0142(20010215)91:4<822::aid-cncr1070>3.0.co;2-g.
Given the association of consumption of green tea with prevention of cancer development, metastasis, and angiogenesis, the effect of the main flavanol present, epigallocatechin-3-gallate (EGCG), on two gelatinases most frequently overexpressed in cancer and angiogenesis (MMP-2 and MMP-9) and on tumor cell invasion and chemotaxis were examined.
Zymography, Western blotting, and enzyme linked immuoadsorbent assay were used to analyze the effect of EGCG on MMP-2 and MMP-9 activity, whereas its effect on tumor cell invasion and chemotaxis was examined using modified Boyden chamber assays.
A Zn2+ chelation-independent, dose-dependent, noncompetitive inhibition by EGCG of both gelatinases was found at concentrations 500 times lower than that reported to inhibit urokinase. Tumor cell invasion of a reconstituted basement membrane matrix, but not chemotaxis, was reduced by 50% with EGCG concentrations equivalent to that in the plasma of moderate green tea drinkers, and 2 orders of magnitude below those of tissue inhibitors of MMPs. Although higher concentrations of EGCG were associated with increased levels of both cell-associated gelatinases and their activator MT1-MMP, no increased gelatinase activation was found, and TIMP-1 and TIMP-2 inhibitors were up-regulated. Finally, concentrations of EGCG active in restraining proliferation and inducing apoptosis of transformed cells were more than 100 times lower than those reported for normal cells.
Epigallocatechin-3-gallate is a potent inhibitor of gelatinases and an orally available pharmacologic agent that may confer the antiangiogenic and antimetastatic activity associated with green tea.
鉴于饮用绿茶与预防癌症发展、转移及血管生成之间的关联，研究了绿茶中主要的黄烷醇表没食子儿茶素没食子酸酯（EGCG）对癌症和血管生成中最常过度表达的两种明胶酶（基质金属蛋白酶-2和基质金属蛋白酶-9）以及对肿瘤细胞侵袭和趋化性的影响。
采用酶谱法、蛋白质印迹法和酶联免疫吸附测定法分析EGCG对基质金属蛋白酶-2和基质金属蛋白酶-9活性的影响，而使用改良的Boyden小室测定法检测其对肿瘤细胞侵袭和趋化性的影响。
发现EGCG对两种明胶酶的抑制作用不依赖锌螯合，呈剂量依赖性且非竞争性，其浓度比报道的抑制尿激酶的浓度低500倍。与中度饮茶者血浆中浓度相当的EGCG可使重构基底膜基质的肿瘤细胞侵袭减少50%，但对趋化性无影响，且该浓度比基质金属蛋白酶组织抑制剂的浓度低两个数量级。尽管较高浓度的EGCG与细胞相关明胶酶及其激活剂膜型基质金属蛋白酶-1（MT1-MMP）水平升高有关，但未发现明胶酶激活增加，且金属蛋白酶组织抑制剂-1（TIMP-1）和金属蛋白酶组织抑制剂-2（TIMP-2）上调。最后，抑制转化细胞增殖和诱导其凋亡的EGCG浓度比正常细胞报道的浓度低100倍以上。
表没食子儿茶素没食子酸酯是一种有效的明胶酶抑制剂，也是一种口服可用的药物，可能具有与绿茶相关的抗血管生成和抗转移活性。
