Evidence For Tumor Response

Additional genotoxicity testing in appropriate models may be conducted for compounds that were negative in the standard test battery but which have shown effects in carcinogenicity bioassay(s) with no clear evidence for a non-genotoxic mechanism.

To help understand the mechanism of action, additional testing can include modified conditions for metabolic activation in in vitro tests or can include in vivo tests measuring genetic damage in target organs of tumor induction ( e.g. , liver UDS test, 32 P-postlabelling, mutation induction in transgenes, or molecular characterization of genetic changes in tumor-related genes).