Epigallocatechin-3-gallate and bicalutamide cause growth arrest and apoptosis in NRP-152 and NRP-154 prostate epithelial cells

Aim: A number of epidemiological studies have suggested that consumption of green tea reduces the risk of prostate cancer. The aim of this study was to elucidate the effects of epigallocatechin-3-gallate (EGCG), one of the major constituents of green tea, on growth inhibition and apoptosis in prostate epithelial cell lines with and without bicalutamide. Methods: The effects of EGCG and bicalutamide alone and in combination were examined on NRP-152 and NRP-154 cells derived from the dorso-lateral prostate of the Lobund-Wistar rat. Following treatments, cell number and levels of apoptosis were assessed. Results: After treatment with EGCG, both cell lines displayed a dose-dependent decrease in cell number; this effect was more pronounced in NRP-154 cells. This decrease in cell number was caused by growth arrest in NRP-152 cells and apoptosis in NRP-154 cells. The apoptotic events in the NRP-154 cells were concurrent with a loss of manganese superoxide dismutase expression. Androgen ablation was achieved by androgen withdrawal using charcoal stripped serum or treatment with bicalutamide. Bicalutamide decreased cell number and induced apoptosis in a dose-dependent manner in both cell lines; however, androgen withdrawal did not. There was a loss of androgen receptor expression in NRP-152 cells with bicalutamide treatment. However, as the NRP-154 cells are androgen receptor negative, the loss in cell number and increased apoptotic events in these cells cannot be attributed to the anti-androgenic activity of bicalutamide. Cells treated with a combination of bicalutamide and EGCG also demonstrated a dose-dependent decrease in cell number that was significantly greater than bicalutamide alone. Conclusions: This study demonstrates the potential use of EGCG and other antioxidants as therapeutic candidates for prostate cancer.