Inhibitory effects of polyphenol-enriched extract from Ziyang tea against human breast cancer MCF-7 cells through reactive oxygen species-dependent mitochondria molecular mechanism
Wenfeng Li a, Nianwu He b, Lingmin Tian a, Xiaolong Shi a, Xingbin Yang a,*
a Key Laboratory of Ministry of Education for Medicinal Resource and Natural Pharmaceutical Chemistry, College of Food Engineering and Nutritional Science, Shaanxi Normal University, Xi'an, China
b College of Biopharmaceutical and Food Engineering, Shangluo University, Shangluo, China
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 μg/mL) by blocking cell-cycle 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.
Keywords: apoptosis, breast cancer, MCF-7 cells, polyphenols, Ziyang green tea