[The new antitumor drug cycloplatam: cytotoxicity and DNA interstrand cross-linking]

Cytotoxicity genetic mechanisms such as induction of SOS-repair, excision repair and interstrand coupling induced by cycloplatam or ammine (cyclopentyl amine)-S(-) malatoplatinum (II), a new antitumor drug, were for the first time studied in comparison to those of the known drug cis-diammine dichloroplatinum (II) (DDP) in a model system of Escherichia coli. In the cells of E. coli the cycloplatam cytotoxicity was much lower than that of DDP. Both the drugs induced SOS-repair in E. coli PQ37. In a concentration of 25 microM DDP was 20 times as active as cycloplatam. In concentrations of 40 to 100 microM the difference leveled. Both the drugs induced interstrand coupling in specimens of pure DNA from calf thymus and E. coli. When the cells of the wild type E. coli AB1157 were incubated in the presence of the drugs only DDP induced the DNA interstrand coupling. No correlation between the DNA interstrand coupling induced by cycloplatam or DDP and cytotoxicity of the drugs was observed.