title: GADD45α induction in the GreenScreen HC indicator assay does not occur independently of cytotoxicity.
abstract: Mammalian chromosomal integrity assays are influenced by cytotoxicity, a phenomenon which impacts data interpretation, assay specificity, and regulatory testing guidelines. Concordance of the GADD45α GreenScreen HC indicator assay to established in vitro and in vivo genetic toxicological assays has previously been described, yet a detailed description in the manner by which cytotoxicity influences its performance has not. Here we present a post-hoc analysis of a previously tested set of 91 proprietary and nonproprietary compounds investigating the influence of cytotoxicity on GADD45α induction and how varying assay cutoff criteria impacts assay performance. Significant cytotoxicity was identified to accompany the majority (72%) of compounds classified as genotoxic by GADD45α induction. Decreasing the GADD45α genotoxic induction criteria (from a 50 to a 30% increase over solvent controls) resulted in an increased assay sensitivity (from 30 to 68%) and concordance (from 55 to 68%), though a concomitant decrease in specificity was also observed (from 97 to 68%). We conclude that GADD45α induction in the GreenScreen HC indicator assay is influenced by cytotoxicity and that assay performance can be improved if different cutoff criteria are implemented.
authors.affiliation: Non Clinical Safety, Hoffmann-La Roche, Nutley, New Jersey, USA. andrew.olaharski@roche.com
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Olaharski
authors.forename: Silvio
authors.initials: S
authors.lastname: Albertini
authors.forename: Lutz
authors.initials: L
authors.lastname: Mueller
authors.forename: Andreas
authors.initials: A
authors.lastname: Zeller
authors.forename: Melanie
authors.initials: M
authors.lastname: Struwe
authors.forename: Elmar
authors.initials: E
authors.lastname: Gocke
authors.forename: Kyle
authors.initials: K
authors.lastname: Kolaja
mesh_terms: D001681:Biological Assay / Q000379:methods*; D018797:Cell Cycle Proteins / Q000378:metabolism*; D005786:Gene Expression Regulation; D006801:Humans; D009152:Mutagenicity Tests / Q000379:methods*; D009687:Nuclear Proteins / Q000378:metabolism*; D000097642:GADD45 Proteins
chemical_list: D018797:Cell Cycle Proteins; D009687:Nuclear Proteins; C439070:GADD45A protein, human; D000097642:GADD45 Proteins