Tea pigments induce cell-cycle arrest and apoptosis in HepG2 cells

doi:10.3748/wjg.v11.i34.5273

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World Journal of Gastroenterology

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1007-9327

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Baishideng Publishing Group Inc, 7041 Koll Center Parkway, Suite 160, Pleasanton, CA 94566, USA

Liver Cancer

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 p21^WAF1 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 p21^WAF1 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