Inhibitory effects of polyphenol-enriched extract from Ziyang tea against human breast cancer MCF7 cells through reactive oxygen species-dependent mitochondria molecular mechanism

Inhibitory effects of polyphenol-enriched extract from Ziyang tea against human breast cancer MCF7 cells through reactive oxygen species-dependent mitochondria molecular mechanism

A polyphenol-enriched extract from selenium-enriched Ziyang green tea (ZTP) was selected to evaluate its antitumor effects against human breast cancer MCF-7 cells. In ZTP, ()-epigallocatechin gallate (28.2%) was identified as the major catechin, followed by ()-epigallocatechin (5.7%) and ()-epicatechin gallate (12.6%). ZTP was shown to inhibit MCF-7 cell proliferation (half maximal inhibitory concentration, IC50=172.2 mg/mL) by blocking cellcycle progression at the G0/G1 phase and inducing apoptotic death. Western blotting assay indicated that ZTP induced cell-cycle arrest by upregulation of p53 and reduced the expression of CDK2 in MCF-7 cells. ZTP-caused cell apoptosis was associated with an increase in Bax/Bcl-2 ratio, and activation of caspase-3 and -9. MCF-7 cells treated with ZTP also showed an overproduction of reactive oxygen species, suggesting that reactive oxygen species played an important role in the induction of apoptosis in MCF-7 cells. This is the first report showing that ZTP is a potential novel dietary agent for cancer chemoprevention or chemotherapy.