Development of a new human cell genotoxicity assay to reduce the use of live animals in drug development

Regulatory in vitro mammalian cell genotoxicity assays have an unacceptably high incidence of false positive results. As a consequence, compounds with unique in vitro positive results frequently proceed to live animal tests because they might not actually carry a carcinogenic hazard. We have demonstrated substantial proof of principle for a novel, high specificity, high sensitivity genomic stress asssay. It exploits our discovery that corrrect regulation of genotoxin-induced GADD45a promoter activity is dependent on p53 interaction with intron 3 of GADD45a. A novel GADD45a-GFP construct is induced by all classes of genotoxic stress including direct acting genotoxins, aneugens, nucleotide synthesis inhibitors, topoisomerase inhibitors,and reactive oxygen species. It is proposed to investigate whether the number of potential carcinogens identified by the test can be increased, either by the use of a human liver-derived host cell line for the reporter, or by the development of a liver extract (S9) metabolic activation protocol. High specificity testing should reduce the number of compounds, carrying false positive in vitro data from other tests, needlessly going forward to live animal tests.

• Research Review 2013: Better genotoxicity assays to reduce animal use