| Objective: To investigate the effects of green tea extract epigallocatechin-3-gallate (EGCG) on proliferation of human colon cancer cell line HT-29 and its molecular mechanism.Methods: HT-29 cells were cultured in vitro. MTT assay was used to test the inhibitory effects of EGCG on proliferation in HT-29 cells. The change of cell cycle in HT-29 cells treated with EGCG for various dose and for various time periods was analyzed using flow cytometry. The expression of PCNA,p53 proteins were detected by immunocytochemistry. The Cyclin D1 protein, phosphorylated and total protein levels of p38MAPK and Rb were examined using western blot.Results: MTT assay has shown that EGCG from 30 to 70μg/ml significantly inhibited HT-29 cells and exhibited a dose-time-dependent modal(P<0.05). As exposed to optics microscope , HT-29 cells took on malignance declining as cellular heteromorphism diminished, nucleocytoplasmic proportion was reliable to reasonableness, cellular apparatus were abundant in plasm ,nuclear and partial cell organs manifest retrograde alters. Flow cytometry analysis revealed that EGCG induce human colon cancer HT-29 G1 phase arrest. In various time or concentration groups, the proportion of cells in G1 phase after treatment with EGCG were increased compared with untreated groups(P<0.05). Immunocytochemical stain detected the expression downregulation of p53, PCNA proteins in HT-29 cells treated with EGCG (50ug/mL) for 48 h. Western blot confirmed EGCG effectively downregulated phosphor-p38MAPK, phosphor-Rb protrein levels and the expressions of Cyclin D1.Conclusions:1.EGCG significantly inhibits proliferation of HT-29 cells in a dose-dependent and time-dependent model.2.EGCG inhibit the proliferation of HT-29 cells via induction of cell cycle G1 phase arrest. 3.The cell cycle G1 phase arrest effect of EGCG may be associated with downregulation the phosphorylation level of p38MAPK and RB protein, the expression of Cyclin D1, p53 and PCNA proteins.
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