Carcinogenic potency in rodents versus genotoxic potency in E. coli: a correlation analysis for bifunctional alkylating agents.

The mutagenic (M), recombinagenic (R) and SOS inducing (I) potencies of 6 bifunctional directly acting alkylating agents (mitomycin C, thiotepa, chlorambucil, nitrogen mustard, bis(2-chloroethyl)ether and bis(2-chloroethyl)nitrosourea) were measured in an E. coli test system (E. coli multitest) as the integral under the yield-dose curve obtained for each event. This potency corresponds to the cumulative yield of the affected cell population over the entire effective dose range of the chemical treatment. A weak mutagenic activity was detected only for mitomycin C and thiotepa. Except for bis(2-chloroethyl)ether, all agents were recombinagenic and SOS inducing. When the 3 genotoxic potencies (M, R and I) of these bifunctional alkylating agents were correlated, separately or in combination, with the respective carcinogenic potencies in rodents, a highly significant correlation was obtained with both the recombinagenic and SOS inducing potencies.