Growth inhibition and cell cycle arrest effects of epigallocatechin gallate in the NBT‐II bladder tumour cell line

OBJECTIVES To examine the growth inhibition and cell cycle arrest effects of epigallocatechin gallate (EGCG), a major constituent of green tea polyphenols, on the NBT‐II bladder tumour cell line. MATERIALS AND METHODS Growth inhibition and cell cycle arrest effects of EGCG were evaluated by the tetrazolium assay, flow cytometry and apoptotic DNA ladder tests. The cell cycle‐related oncogene and protein expressions in NBT‐II bladder tumour cells, when incubated with EGCG, were detected with reverse transcription‐polymerase chain reaction (RT‐PCR) and Western blot analysis. RESULTS EGCG inhibited growth of the NBT‐II bladder tumour cells in a dose‐ and time‐dependent manner. Flow cytometry showed a G0/G1 arrest in cells when cultured with EGCG at doses of 10, 20 or 40 µmol/L for 48 or 72 h. The apoptotic DNA ladder test showed that EGCG at 10 µmol/L induced early apoptosis after 48 h of incubation. A down‐regulation of cyclin D1 was detected by RT‐PCR when the cells were incubated with EGCG (20 µmol/L for 48 h. EGCG also down‐regulated protein expression of cyclin D1, cyclin‐dependent kinase 4/6 and phosphorylated retinoblastoma protein, in both a time‐ and dose‐dependent manner, when detected by Western blot. CONCLUSION EGCG had growth inhibition and cell‐cycle arrest effects in NBT‐II bladder tumour cells by down‐regulating the cyclin D1, cyclin‐dependent kinase 4/6 and retinoblastoma protein machinery for regulating cell‐cycle progression.