ANTITUMOR-ACTIVITY OF THEVETOSIDE, IN-VITRO

Objective. To study the effects of thevetoside (TS), a cardiac glycosi de, and an inhibitor of Na+, K+-ATPase, on tumor cells cultured in vit ro. Methods. The cytotoxic effects of TS on tumor cells were determine d by trypan blue dye exclusion, neutral red vital staining and clonoge nic assay. The time-effect relationship and growth inhibition of tumor cells by TS were assayed with trypan blue exclusion method. Results. TS at low doses (0.005-0.1 mg . L(-1)), with dose dependence, was able to kill SMMC-7721, SGC-7901 and HeLa cells. IC50 values for SMMC-7721 , SGC-7901 and HeLa cells were 0.007, 0.011 and 0.018 mg . L(-1) by tr ypan blue dye exclusion test and 0.016, 0.055 and 0.078 mg . L(-1) neu tral red vital staining test. TS inhibited the clonal forming rate of SMMC-7721 and SGC-7901 significantly with IC50 values of 0.021 and 0.0 36 mg . L(-1), respectively. Only when the cells were continuously tre ated with TS for more than 8 hours, the drug-induced cell lethality co uld be displayed and strengthened quickly. The growth of tumor cells w as notably inhibited after they were exposed to 0.1 mu g/ml of TS for 12 hours. All the experimental results of antitumor activity in vitro showed that SMMC-7721 was most sensitive to TS among the three kinds o f tumor cells. Conclusions. TS has cytotoxic action on tumor cells cul tured in vitro and this lethal effect must have an action process, in which tumor cells are not dead but suffer from deadly injury and lost the capability of unlimited proliferation.