Characteristics of cytostatic effects of oridonin in vitro

The cytostatic effects of oridonin on the MGc80-3 human gastric adenocarcinoma cells in different proliferation stages were studied by colony-forming assay. An exposure of exponential-phase cells to oridonin for 1 or 24 h resulted in a threshold-exponential dose-survival curve. The plateau-phase cells exposed for the some periods of time seemed to be resistant to the drug. The synchronized cells caused by pretreatment with low-serum and hydroxyurea were exposed to oridonin 25 or 35 microg/ml for 1 h and there was no significant difference in the drug sensitivities between the different phases. These data suggest that oridonin seems to be a cyclespecific anticancer drug.