Evaluation of high-throughput genotoxicity assays used in profiling the US EPA ToxCast chemicals.
Three high-throughput screening (HTS) genotoxicity assays-GreenScreen HC GADD45a-GFP (Gentronix Ltd.), CellCiphr p53 (Cellumen Inc.) and CellSensor p53RE-bla (Invitrogen Corp.)-were used to analyze the collection of 320 predominantly pesticide active compounds being tested in Phase I of US. Environmental Protection Agency's ToxCast research project. Between 9% and 12% of compounds were positive for genotoxicity in the assays. However, results of the varied tests only partially overlapped, suggesting a strategy of combining data from a battery of assays. The HTS results were compared to mutagenicity (Ames) and animal tumorigenicity data. Overall, the HTS assays demonstrated low sensitivity for rodent tumorigens, likely due to: screening at a low concentration, coverage of selected genotoxic mechanisms, lack of metabolic activation and difficulty detecting non-genotoxic carcinogens. Conversely, HTS results demonstrated high specificity, >88%. Overall concordance of the HTS assays with tumorigenicity data was low, around 50% for all tumorigens, but increased to 74-78% (vs. 60% for Ames) for those compounds producing tumors in rodents at multiple sites and, thus, more likely genotoxic carcinogens. The aim of the present study was to evaluate the utility of HTS assays to identify potential genotoxicity hazard in the larger context of the ToxCast project, to aid prioritization of environmentally relevant chemicals for further testing and assessment of carcinogenicity risk to humans.
Knight
Andrew W
AW
Gentronix Ltd., CTF Building, Manchester, M13 9NT, UK. andrew.knight@gentronix.co.uk
Little
Stephen
S
Houck
Keith
K
Dix
David
D
Judson
Richard
R
Richard
Ann
A
McCarroll
Nancy
N
Akerman
Gregory
G
Yang
Chihae
C
Birrell
Louise
L
Walmsley
Richard M
RM
D000818:Animals; D001681:Biological Assay; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D004247:DNA / Q000187:drug effects; D004249:DNA Damage; D004785:Environmental Pollutants / Q000145:classification / Q000633:toxicity*; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects; D005809:Genes, Regulator / Q000187:drug effects; D017930:Genes, Reporter / Q000187:drug effects; D049452:Green Fluorescent Proteins / Q000096:biosynthesis; D045325:HCT116 Cells / Q000187:drug effects / Q000473:pathology; D056945:Hep G2 Cells / Q000187:drug effects / Q000473:pathology; D057166:High-Throughput Screening Assays; D006801:Humans; D008297:Male; D051379:Mice; D009152:Mutagenicity Tests / Q000379:methods*; D009153:Mutagens / Q000145:classification / Q000633:toxicity*; D010575:Pesticides / Q000145:classification / Q000633:toxicity*; D051381:Rats; D014481:United States; D014484:United States Environmental Protection Agency
D004785:Environmental Pollutants; D009153:Mutagens; D010575:Pesticides; D049452:Green Fluorescent Proteins; D004247:DNA