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Published on: February 22, 2015
Interlaboratory assessment of the GreenScreen HC GADD45a-GFP genotoxicity screening assay: an enabling study for
Nicholas Billinton1, Paul W Hastwell, Dominiek Beerens
1Gentronix Ltd, CTF Building, 46 Grafton Street, Manchester M13 9NT, UK. nick.billinton@gentronix.co.uk
Abstract:
Sixteen coded compounds were blind-tested at 4 laboratories using the recently described GADD45a-GFP genotoxicity assay. The compounds were chosen to include non-genotoxic compounds as well as weak and strong genotoxins. None of the compounds required metabolic activation in order to exhibit genotoxic effects. The participating laboratories included 2 global pharmaceutical companies, a global consumer goods company and the Gentronix laboratory in Manchester. Each compound was tested 4 times on different days following a protocol previously described. The tests were carried out after a 3-day training period from the parent lab (Manchester). Following the exclusion of data from tests with positive control failures and data series with 'spikes', 92% of assays gave the correct result: non-genotoxins giving negative results and genotoxins giving positive results. There were no randomly distributed problems suggesting that differences between the results from different sites reflected the use of different instruments, procedural differences and operator experience. In naïve operator laboratories the quality of data improved with operator practice. It was concluded that simple clarification of the protocol would provide the level of reliability required for widespread use of the assay in hazard assessment.
Insights
The GADD45a-GFP genotoxicity assay accurately identified genotoxic and non-genotoxic compounds across multiple labs. Protocol clarification can enhance its reliability for hazard assessment.
Area of Science:
- Biotechnology
- Toxicology
- Molecular Biology
Background:
- Genotoxicity assays are crucial for chemical safety assessment.
- The GADD45a-GFP assay is a novel tool for evaluating DNA damage response.
- Standardization and inter-laboratory validation are essential for assay adoption.
Purpose of the Study:
- To validate the GADD45a-GFP genotoxicity assay across multiple independent laboratories.
- To assess the assay's reliability in distinguishing between genotoxic and non-genotoxic compounds.
- To identify factors influencing assay performance and potential areas for protocol improvement.
Main Methods:
- Blind testing of 16 coded compounds (non-genotoxins, weak and strong genotoxins) at 4 laboratories.
- Utilizing the GADD45a-GFP genotoxicity assay with a standardized protocol.
- Excluding data from positive control failures and 'spikes' for robust analysis.
Main Results:
- 92% of assays yielded correct results, accurately classifying compounds.
- Genotoxins were consistently identified as positive, and non-genotoxins as negative.
- Operator experience and procedural consistency impacted data quality, with improvement observed over time.
Conclusions:
- The GADD45a-GFP assay demonstrates high reliability for genotoxicity testing.
- Inter-laboratory variability is linked to instrument differences, procedures, and operator experience.
- Refinement of the assay protocol is recommended for widespread adoption in hazard assessment.
