Tea pigments induce cell-cycle arrest and apoptosis in HepG2 cells.
OBJECTIVE
To investigate the molecular mechanisms by which tea pigments exert preventive effects on liver carcinogenesis.


METHODS
HepG2 cells were seeded at a density of 5X10(5)/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.


CONCLUSIONS
Tea pigments induce cell-cycle arrest and apoptosis. Tea pigments may be used as an ideal chemopreventive agent.
Jia
Xu-Dong
XD
Institute for Nutrition and Food Safety, Chinese Center for Disease Control and Prevention, 29 Nanwei Road, Beijing 100050 China. jshchen@ilsichina-fp.org
Han
Chi
C
Chen
Jun-Shi
JS
D016588:Anticarcinogenic Agents / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D006528:Carcinoma, Hepatocellular; D045744:Cell Line, Tumor / Q000166:cytology / Q000187:drug effects; D016193:G1 Phase / Q000187:drug effects; D006801:Humans; D008113:Liver Neoplasms; D010860:Pigments, Biological / Q000494:pharmacology*; D010936:Plant Extracts / Q000494:pharmacology; D013662:Tea
D016588:Anticarcinogenic Agents; D010860:Pigments, Biological; D010936:Plant Extracts; D013662:Tea