Preliminary study on the mechanism of oridonin-induced apoptosis in human squamous cell oesophageal carcinoma cell line EC9706.

Objective: To study the apoptosis-inducing effect of the Chinese medicine oridonin in the human oesophageal squamous cell carcinoma cell line EC9706, in vitro.

Methods: The effect of oridonin on cell proliferation was studied using the colorimetric 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Effects on the cell cycle and apoptosis were studied by flow cytometry; effects on intracellular Ca(2+) concentration were studied by measuring the fluorescence intensity of a fluorescent Ca(2+) probe by laser scanning confocal microscopy.

Results: The EC9706 cell-proliferation rate decreased with time and oridonin concentration (10-40 µmol/l). The number of cells in G0 and G1 phases increased significantly following exposure to oridonin for 48 and 72 h respectively, and oridonin was shown to be most effective at inducing apoptosis in EC9706 cells at 40 µmol/l. Compared with the control group, all concentrations of oridonin tested (10-40 µmol/l) significantly increased the Ca(2+) fluorescence intensity of EC9706 cells.

Conclusions: Oridonin was shown to inhibit proliferation and induce apoptosis in the human oesophageal squamous cell carcinoma cell line EC9706, in vitro. These data provide preliminary experimental evidence for the anticancer effects of oridonin, which is as a traditional Chinese medicine used to treat various cancers, including oesophageal squamous cell carcinoma. Further studies are required to elucidate the mode of action.