Anti-tumor Effects of Epigallocatechin-3-gallate Extracted from Green Tea on Ovarian Cancer Cell Lines

Huh, Seung Won; Bae, Su Mi; Han, Chan Hee; Choi, Ji Hyang; Kim, Chong Kook; Park, Eun Kyung; Ro, Duck Young; Lee, Joon Mo; Namkoong, Sung Eun; Ahn, Woong Shick

Abstract

OBJECTIVE
A constituent of green tea, (-)-epigallocatechin-3-gallate (EGCG), has been known to possess anti-diabetes, anti-hypertension and anti-cancer properties. In this study, we investigated the anticancer effects of EGCG on human ovarian cancer cell lines. The growth inhibitory mechanism(s) and regulation of cell cycle-related proteins by EGCG were also evaluated.
METHODS
To carry out cell counting assay to observe the anti-proliferative effects, we treated 25, 50, and 100 uM EGCG to both ovarian cancer cell lines SKOV-3 and OVCAR-3, respectively. Also, we treated EGCG to PA-1 cells with 6.25, 12.5 and 25 uM, respectively. Six days later, we examined the characteristics of apoptosis and changes in cell cycle regulation by cell counting assay, Annexin V-FITC staining and DNA fragmentation assay, and FACS analysis. In addition, protein and gene expression patterns in SKOV-3 cell were investigated by using cell cycle cDNA chip, RT-PCR, and Western blot analyses.
RESULTS
Inhibition of cell growth by cell counts showed in SKOV-3 cells with 48.8%, 82.5%, 99.2% after six days of the treatment with 25, 50, 100 uM of EGCG, respectively. OVCAR-3 cells showed 53.9%, 84.8%, and 97.7% growth inhibition patterns. And PA-1 cells showed 17.1%, 48.4%, and 74.1%, as compared to control. When SKOV-3 cells were tested for EGCG-induced apoptosis, apoptotic cells were observed with 8.6, 11.4, and 23.3-fold at 25, 50, 100 uM EGCG, respectively. And PA-1 cells showed 1.7, 2.4, and 4.2-fold, as compared to control. In contrast, OVCAR-3 did not show EGCG-induced apoptosis. When SKOV-3 cells were tested for their gene expression using cell cycle cDNA chip after treatment with 24.5 uM of EGCG, up-regulations of p21, Bax and cyclin G were shown, while down-regulations of CDK6, E2F-4, and cyclin A were shown. In Western blot assay, up-regulations of Bax and p21 proteins were shown, while down- regulations of cyclin D1, Bcl-XL, Rb, CDK2, E2F-1, E2F-4, PCNA proteins were shown.
CONCLUSION
These data support that EGCG can inhibit ovarian cancer cell growth through induction of apoptosis and cell cycle arrest as well as regulation of gene and protein expressions. Thus, EGCG likely provides an additional option for a new and potential drug approach for ovarian cancer.