Hypersensitivity of Fac −/− mice to MMC. (A) Survival curves of Fac +/+, +/−, and −/− mice from different genetic backgrounds after one injection of 1 mg/kg MMC. (B) Survival curves of Fac +/+ and −/− mice from different genetic backgrounds after weekly injections of 0.3 mg/kg MMC. Controls include Fac −/− mice that received weekly saline injections or one single injection of 0.3 mg/kg MMC. Survival is expressed as the percentage of the number of live mice subjected to MMC treatment (n = 17). All control animals survived for up to several months before being killed for histological analysis.