Liver Cancer
Copyright ©The Author(s) 2005. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Gastroenterol. Sep 14, 2005; 11(34): 5273-5276
Published online Sep 14, 2005. doi: 10.3748/wjg.v11.i34.5273
Tea pigments induce cell-cycle arrest and apoptosis in HepG2 cells
Xu-Dong Jia, Chi Han, Jun-Shi Chen
Xu-Dong Jia, Chi Han, Jun-Shi Chen, Institute of Nutrition and Food Safety, Chinese Center for Disease Control and Prevention, 29 Nanwei Road, Beijing 100050, China
Author contributions: All authors contributed equally to the work.
Supported by the National Natural Science Foundation of China, No. 39970639
Correspondence to: Dr. Jun-Shi Chen, Institute for Nutrition and Food Safety, Chinese Center for Disease Control and Prevention, 29 Nanwei Road, Beijing 100050 China. jshchen@ilsichina-fp.org
Telephone: +86-10-83132553 Fax: +86-10-83132021
Received: November 20, 2004
Revised: December 15, 2004
Accepted: December 21, 2004
Published online: September 14, 2005
Abstract

AIM: To investigate the molecular mechanisms by which tea pigments exert preventive effects on liver carcinogenesis.

METHODS: HepG2 cells were seeded at a density of 5×105/well in six-well culture dishes and incubated overnight. The cells then were treated with various concentrations of tea pigments over 3 d, harvested by trypsinization, and counted using a hemocytometer. Flow cytometric analysis was performed by a flow cytometer after propidium iodide labeling. Bcl-2 and p21WAF1 proteins were determined by Western blotting. In addition, DNA laddering assay was performed on treated and untreated cultured HepG2 cells.

RESULTS: Tea pigments inhibited the growth of HepG2 cells in a dose-dependent manner. Flow-cytometric analysis showed that tea pigments arrested cell cycle progression at G1 phase. DNA laddering was used to investigate apoptotic cell death, and the result showed that 100 mg/L of tea pigments caused typical DNA laddering. Our study also showed that tea pigments induced upregulation of p21WAF1 protein and downregulation of Bcl-2 protein.

CONCLUSION: Tea pigments induce cell-cycle arrest and apoptosis. Tea pigments may be used as an ideal chemopreventive agent.

Keywords: Tea pigments; Cell cycle; Apoptosis