title: Reduction of misleading ("false") positive results in mammalian cell genotoxicity assays. III: sensitivity of human cell types to known genotoxic agents.
abstract: We have demonstrated previously that the seemingly high rate of "false" or "misleading" positive results from in vitro micronucleus assays (MNvit) was greater when rodent derived cell lines and certain toxicity measures, such as relative cell count or replication index, were used. These studies suggested that the use of a human cell type with functional p53 and a toxicity measure that included a function of cell proliferation could dramatically reduce the detection of misleading positive results. A reduced "false positive rate" should not be at the expense of a loss of sensitivity of the assay. Therefore, we have investigated the sensitivity of the MNvit assay to known genotoxic agents using three cell types shown previously to be less prone to misleading positives, namely human lymphocytes (HuLy), TK6 and HepG2 cells. The 17 chemicals are well characterised and are from a list of chemicals known to produce positive results in in vitro mammalian cell assays. These data demonstrated a high sensitivity of the assay in which TK6 and HuLy cells were employed, such that 15 out of the 17 chemicals were correctly identified. By contrast, the use of HepG2 cells resulted in far fewer than expected positive responses. In conclusion, using TK6 and HuLy cells in preference to long established rodent cell lines in order to improve specificity does not compromise the sensitivity of the MNvit to detect known genotoxic agents.
authors.affiliation: Unilever, Safety and Environmental Assurance Centre, Colworth Science Park, Sharnbrook, Bedfordshire MK44 1LQ, UK. Electronic address: pauljamesfowler@gmail.com.
authors.forename: Paul
authors.initials: P
authors.lastname: Fowler
authors.affiliation: Covance Laboratories Limited, Otley Road, Harrogate HG3 1PY, UK.
authors.forename: Robert
authors.initials: R
authors.lastname: Smith
authors.affiliation: Covance Laboratories Limited, Otley Road, Harrogate HG3 1PY, UK.
authors.forename: Katie
authors.initials: K
authors.lastname: Smith
authors.affiliation: Quotient Bioresearch Ltd., Pegasus Way, Rushden, Northamptonshire, NN10 6ER, UK.
authors.forename: Jamie
authors.initials: J
authors.lastname: Young
authors.affiliation: Covance Laboratories Limited, Otley Road, Harrogate HG3 1PY, UK.
authors.forename: Laura
authors.initials: L
authors.lastname: Jeffrey
authors.affiliation: Unilever, Safety and Environmental Assurance Centre, Colworth Science Park, Sharnbrook, Bedfordshire MK44 1LQ, UK.
authors.forename: Paul
authors.initials: P
authors.lastname: Carmichael
authors.affiliation: Kirkland Consulting, PO Box 79, Tadcaster LS24 0AS, North Yorkshire, UK.
authors.forename: David
authors.initials: D
authors.lastname: Kirkland
authors.affiliation: Procter & Gamble, 8700 Mason-Montgomery Road, Mason, OH 45040, USA.
authors.forename: Stefan
authors.initials: S
authors.lastname: Pfuhler
mesh_terms: D001681:Biological Assay / Q000379:methods*; D003603:Cytotoxins / Q000009:adverse effects* / Q000494:pharmacology; D005189:False Positive Reactions; D056945:Hep G2 Cells; D006801:Humans; D048629:Micronuclei, Chromosome-Defective; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism
chemical_list: D003603:Cytotoxins; C495901:TP53 protein, human; D016159:Tumor Suppressor Protein p53
keywords: Genotoxicity; Human cells; Misleading positive results; Sensitivity