Evaluation of mutant frequencies of chemically induced tumors and normal tissues in lambda/cII transgenic mice.

Genomic instability has been implicated as an important component in tumor progression. Evaluation of mutant frequencies (MFs) in tumors of transgenic mice containing nontranscribed marker genes should be useful for quantitating mutation rates in tumors as the physiologically inactive transgene provides neither a positive nor a negative selective pressure on the tumor. We have conducted long-term carcinogenicity studies in lambda/cII transgenic B6C3F1 mice using a variety of genotoxic and nongenotoxic test agents and have evaluated the mutant frequencies in both tumors and normal tissues from these animals.