Abstract: Objective　To investigate the induction of apoptosis on human oral epidermoid carcinoma KB cells and multidrug resistant KBv200 cells byMatrine.Methods　MTT assay was used to investigate the inhibition ability of Matrine on the cellsin vitro. Transmission electronmicroscopewas used to observe the ultrastructure feature of cells aftertreated byMatrine. Acridine or- ange (AO)/Ethidium bromide (EB) fluorescent staining and flow cytometry were used to observe apoptosis induced by Matrine. Flow cytometry was applied to study the effects of the drug on cell cycles of the cells.Results　When 0.50,1.00,1.50,2.00 mg/ml of Matrine was used, the vital rates of KB and KBv200 cellswere decreased according toMatrine′s concentration. The IC50 concentrations ofMatrine on KB and KBv200 cells were 1.35 mg/ml and 1.43 mg/ml individually. The results of AO/EB fluores- cent staining and flow cytometry showed thatMatrine could induce apoptosis of two kinds of cells. While observed by transmission electron microscope, there were more contraction of cells, condensation of nuclei, bubble of cytoplasm in both kinds of cells after treated byMatrine. Matrine could stop the growth of KB and KBv200 cells at S period and restrain mitosis of cells.Conclusion　 Matrine can inhibit the growth of KB and KBv200 cells by inducing apoptosis. The apoptosis effect is dose-dependent and it has certain relation to the blocking of S period cells.

Key words: matrine, human oral epidermoid carcinoma, KB cell, multidrug resistant, apoptosis