Studies on radiosensitization of Escherichia coli cells by cis-platinum complexes

We recently reported that the antitumor drug cis-Pt(NH3)2Cl2 (cis-DDP) produces significant radiosensitization of anoxic E coli C cells. We have extended these studies to three other platinum drugs, all of which have been shown to be more effective antitumor drugs than cis-DDP. The drugs are: cis-dichloro bis(ethylene imine) Pt(II) (cis-DEP); cis-dichlorobicyclopentylamine Pt(II) (cis-PAD); and Pt-thymine blue (cis-PTB). Survival curve studies indicate that these drugs all produce greater anoxic radiosensitization of E coli C than cis-DDP at concentrations which are less toxic to the cells than similar concentrations of cis-DDP. If the cells are treated with any one of these drugs for two hours and then washed to remove the drug before irradiation, no detectable radiosensitization is found. We conclude that these drugs have the potential for being useful agents in combined modality therapy and that they warrant further study in mammalian systems