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

Department of Neurosurgery (S.Y., H.H., N.W., J.K.), Laboratory and Molecular Medicine (K.P.S.), Faculty of Medicine, Kagoshima University, Kagoshima 890-8520, Japan

¹ Address correspondence and reprint requests to Shunichi Yokoyama, Department of Neurosurgery, Faculty of Medicine, Kagoshima University, 8-35-1 Sakuragaoka, Kagoshima 890-8520, Japan.

Abstract

We investigated the effect of epigallocatechin-gallate (EGCG), the main constituent of green tea polyphenols, on human glioblastoma cell lines U-373 MG and U-87 MG, rat glioma cell line C6, and rat nonfunctioning pituitary adenoma cell line MtT/E. Cell viability was determined by assay with 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT), and the extent of apoptosis was studied by `ow cytometric 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 significant 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 significantly 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.

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