title: Isotonic Regression Based-Method in Quantitative High-Throughput Screenings for Genotoxicity.
abstract: Quantitative high-throughput screenings (qHTSs) for genotoxicity are conducted as part of comprehensive toxicology screening projects. The most widely used method is to compare the dose-response data of a wild-type and DNA repair gene knockout mutants, using model-fitting to the Hill equation (HE). However, this method performs poorly when the observed viability does not fit the equation well, as frequently happens in qHTS. More capable methods must be developed for qHTS where large data variations are unavoidable. In this study, we applied an isotonic regression (IR) method and compared its performance with HE under multiple data conditions. When dose-response data were suitable to draw HE curves with upper and lower asymptotes and experimental random errors were small, HE was better than IR, but when random errors were big, there was no difference between HE and IR. However, when the drawn curves did not have two asymptotes, IR showed better performance (p < 0.05, exact paired Wilcoxon test) with higher specificity (65% in HE vs. 96% in IR). In summary, IR performed similarly to HE when dose-response data were optimal, whereas IR clearly performed better in suboptimal conditions. These findings indicate that IR would be useful in qHTS for comparing dose-response data.
authors.affiliation: Center for Genomic Medicine, Kyoto University Graduate School of Medicine, Japan.
authors.forename: Yosuke
authors.initials: Y
authors.lastname: Fujii
authors.affiliation: Department of Radiation Genetics, Kyoto University Graduate School of Medicine, Japan.
authors.forename: Takeo
authors.initials: T
authors.lastname: Narita
authors.affiliation: Division of the National Toxicology Program, National Institute of Environmental Health Sciences, USA.
authors.forename: Raymond Richard
authors.initials: RR
authors.lastname: Tice
authors.affiliation: Department of Radiation Genetics, Kyoto University Graduate School of Medicine, Japan.
authors.forename: Shunich
authors.initials: S
authors.lastname: Takeda
authors.affiliation: Department of Radiation Genetics, Kyoto University Graduate School of Medicine, Japan.
authors.forename: Ryo
authors.initials: R
authors.lastname: Yamada
keywords: Hill equation; Isotonic regression; genotoxicity; quantitative high-throughput screening