In vitro mammalian cell mutation assays based on transgenic reporters: A report of the International Workshop on Genotoxicity Testing (IWGT)
- DOI
- Language of the publication
- English
- Date
- 2019-04-13
- Type
- Article
- Author(s)
- White, Paul A.
- Luijten, Mirjam
- Mishima, Masayuki
- Cox, Julie A.
- Hanna, Joleen N.
- Maertens, Rebecca M.
- Zwart, Edwin P.
- Publisher
- Elsevier
Abstract
Chemical safety evaluations require assessment of genetic toxicity. Transgenic rodent (TGR) assays permit enumeration of mutations in chromosomally-integrated targets contained in shuttle vectors. In order to improve in vitro mutagenicity assessment, and to substantially reduce animal use, in vitro assays using transgenic reporters have been developed. These assays are based on cells derived from TGRs, or cells transfected with transgenic shuttle vectors containing a mutation target. As part of the 7th International Workshop on Genotoxicity Testing, an In Vitro Mammalian Cell Gene Mutation Assay working group reviewed all published information pertaining to in vitro transgene mutagenicity assays; the utility, advantages and disadvantages of the assays were evaluated and discussed. The review revealed that over 20 TGR-based in vitro assays have been used to assess the mutagenic activity of over 150 agents. Overall, the Working Group considered in vitro transgene mutagenicity assays pragmatic tools for the safety evaluation of new and existing substances. A formal SWOT (strengths, weaknesses, opportunities, threats) analysis revealed advantages including the use of established scoring protocols, avoidance of laborious clone isolation and enumeration, ability to use metabolically competent primary cells, ability to detect different types of genetic damage, large dynamic range, and complementarity to in vivo TGR endpoints. Disadvantages include lack of validation and little consistency in protocols, the use of specialised reagents, the time and effort required for mutant enumeration, the use of some cell lines that lack metabolic capacity, and the need for multiple assays to cover all mutational mechanisms. Several assays have been partially validated, indicating promising reliability, reproducibility and applicability domain. Once in vitro transgene mutagenicity assays have been more thoroughly validated, they are well placed to augment or replace existing in vitro mammalian cell mutagenicity assays, particularly in cases where the in vivo TGR mutation assay is intended for follow-up.
Plain language summary
Chemical safety evaluations, including those conducted by Health Canada, require assessment of genetic toxicity (i.e., ability to damage DNA). Transgenic rodent (TGR) assays permit enumeration of chemically-induced mutations in DNA targets integrated into the genomes of experimental animals (i.e., rat and mouse). In order to reduce the use of animals, researchers have developed mutagenicity assays based on cultured cells that contain reporters inserted into their genome (i.e., in vitro assays). These transgenic reporters contain genes used as mutation targets. As part of the 7th International Workshop on Genotoxicity Testing (IWGT), an In Vitro Mammalian Cell Gene Mutation Assay working group reviewed all published information pertaining to in vitro transgene mutagenicity assays; the utility, advantages and disadvantages of the assays were evaluated and discussed. The review revealed that over 20 TGR-based assays have been used to assess the mutagenic activity of over 150 agents. Overall, the Working Group considered in vitro transgene mutagenicity assays pragmatic tools for the safety evaluation of new and existing substances. A formal SWOT (strengths, weaknesses, opportunities, threats) analysis revealed advantages including the use of established scoring protocols, ability to use metabolically-competent cells, ability to detect different types of genetic damage, large dynamic range, and complementarity to in vivo TGR endpoints. Disadvantages include lack of validation and little consistency in protocols, the use of specialised reagents, the time and effort required for scoring induced mutations, the use of some cells that lack metabolic capacity, and the need for multiple assays to cover all mutational mechanisms. Several assays have been partially validated; indicating promising reliability and reproducibility. Once in vitro transgene mutagenicity assays have been more thoroughly validated, they are well placed to augment or replace existing mammalian cell mutagenicity assays, particularly in cases where the in vivo TGR mutation assay is intended for follow-up.
Subject
- Health,
- Health and safety