Inhibitory effect of epigallocatechin-gallate on brain tumor cell lines in vitro

Abstract

We investigated the effect of epigallocatechin-gallate (EGCG), the main constituent of green tea polyphe-nols, on human glioblastoma cell lines U-373 MG and U-87 MG, rat glioma cell line C6, and rat nonfunc-tioning pituitary adenoma cell line MtT/E. Cell viability was determined by assay with 3-(4,5-dimethylthia-zol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT), and the extent of apoptosis was studied by ow cyto-metric analysis. Apoptosis was also characterized by morphology using uorescent microscopy. The role of insulin-like growth factor-I (IGF-I) was studied by assay with MTT, immunohistochemistry, and immunoradiometric assay. After 72-h exposure, a statistically signiicant loss of viability (P = < 0.0001) was observed at concentrations of 12.5, 25, 50, and 100 µg/ml in U-373 MG cells and U-87 MG cells. EGCG at concentrations of 50 µg/ml and higher signiicantly reduced the viability of C6 cells. EGCG inhibited viability of MtT/E cells only at a concentration of 100 µg/ml. Quantitative study by ow cytometry demonstrated that lower doses of EGCG (12.5, 25, 50 µg/ml) induced apoptosis in U-373 MG, U-87 MG, and C6 cells; however, only the highest dose (100 µg/ml) induced apoptosis in MtT/E cells. Compared with other cell lines, MtT/E cells showed stronger IGF-I immunoreactivity. Neutralization of IGF-I with an antihuman IGF-I antibody reduced viability of the cell lines. It can be concluded that EGCG has an inhibitory effect on malignant brain tumors, and IGF-I may be involved in the effects of EGCG.