Enhancement of radiosensitivity and the potential mechanism on human esophageal carcinoma cells by tetrandrine.

The purposes of this study were to test the effect of tetrandrine, alone or combined with radiation, on human esophageal cancer cell line TE1 (TE1 cells) and investigate the potential antitumor mechanism. Human esophageal cancer cell line TE1 was tested by methyl thiazolyl tetrazolium assay for cell proliferation, colony-forming assay for cell radiosensitivity, flow cytometry assay for cell cycle distribution, and western blot assay for cell cycle protein expression. When treated alone, tetrandrine had a time- and concentration-dependent cytotoxic effect on TE1 cells. The dose-enhancement ratio for combined tetrandrine and radiation was markedly increased when compared with tetrandrine alone. Further, expression of cyclin B1 protein increased after addition of tetrandrine when compared with radiation only. Radiation-induced G2 arrest was abrogated with treatment of tetrandrine. In conclusion, tetrandrine can enhance the radiosensitivity of TE1 cells and this may involve relief of radiation-induced G2/M arrest in TE1 cells.