Modeling the Responsiveness of Sensitive Populations to Genotoxic Agents Using DNA Repair Inhibitors

Project Summary It is well recognized that conventional toxicology assays exhibit a crucial deficiency. Specifically, their use of limited numbers of cell lines and rodent strains does not provide information about toxic responses that may occur in sensitive human populations. Although studying very large numbers of cell lines and laboratory rodent models could theoretically address this issue, it is not a practical answer. There are simply too many legacy chemicals and new chemical substances being developed for this to represent a routine testing scheme. Fortunately, in the area of genetic toxicology, a solution exists. Our innovative approach takes into account the fact that inter-subject differences in sensitivity to genotoxic agents is predominately due to variable DNA repair capacity. Our project will develop an efficient, high throughput, in vitro genotoxicity assay platform that provides information about chemicals’ potential to cause DNA damage in prototypical and sensitive human populations. The high efficiency of our proposed approach is in part explained by our decision to study a single p53- competent human cell line (TK6) to generate prototypical genotoxic response profiles. Sensitive population responses will be modelled by co-exposing cells to each test chemical in combination with a panel of small molecule DNA repair inhibitors. These inhibitors will be chosen to cover each of the major DNA repair pathways. In addition to our use of DNA repair inhibitors to efficiently mimic sensitive populations, other innovative aspects of our project include our use of a multiplexed DNA damage assay to cover multiple biomarkers of genotoxicity and cytotoxicity, and state-of-the-art benchmark dose software to characterize the family of dose-response relationships that will be generated for each chemical studied. Once reduced to practice, we will make the assay available as a set of kit-formatted reagents, and also through fee-for-service testing.