[Epigallocatechin-3-gallate induces G1 phase cell cycle arrest in KB cells].

OBJECTIVE: To explore the effects of epigallocatechin-3-gallate (EGCG) on the proliferation of human oral epithelial cancer cell line KB cells and the molecular mechanisms. METHOD: KB cells were treated with various concentrations of EGCG for 24 or 48 h. MTT assay was used to test the cell viability. The changes of cell cycle in KB cells treated with EGCG for 48 h were analyzed using flow cytometry. The expressions of cyclin A, cyclin D1 and cyclin E were detected by RT-PCR and Western blotting. RESULT: The viability of KB cells treated with various concentrations of EGCG (25, 50, 100, 200, 400, and 800 micromol/L) for 48 h were decreased to (85.4-/+2.4)%, (80.4-/+2.8)%, (51.5-/+4.5)%, (30.2-/+1.9)%, (25.3-/+1.5)%, (20.0-/+1.1)%, respectively, showing significant difference from that of the control group [(100.0-/+2.2)%, P<0.05). EGCG decreased the viabilities of KB cells in a dose-dependent manner. Flow cytometry demonstrated that treatment with EGCG significantly increased the cell percentage in sub-G1 phase, which was (73.5-/+4.4)% after a 48-h EGCG treatment, significantly different from that in the control group [(47.3-/+3.5)%, P<0.05). EGCG-induced G1 phase arrest was correlated to the down-regulation of cyclin A and cyclin E. CONCLUSION: EGCG inhibits the proliferation of KB cells by inducing G1 phase arrest, which involves the downregulation of cyclin E.