[Modification of the cytotoxic effect of peplomycin by cepharanthine]

The cytotoxicity of peplomycin modified by cepharanthine, was studied on in vitro cultured Chinese Hamster V-79 cells. Cepharanthine alone showed almost no cytotoxicity on this tumor system. It was revealed that cepharanthine enhanced the cell killing action of peplomycin and also promoted the recovering process from the effects of peplomycin. The enhancing effect increased with an increase of the concentration at the lower concentrations but there were limitations at the higher concentrations. The bi-phasic properties specific to peplomycin on the dose-survival curves were unchanged even in combination with cepharanthine was observed in the recovering process from the effects of peplomycin. From these results, cepharanthine seemed not to affect on the mechanism of action of peplomycin.