MAQC-II Project: Iconix data set

The Iconix data set (endpoint B) was provided by Iconix Biosciences, Inc. (Mountain View, CA, USA). The study objective was to assess, upon short term exposure, hepatic tumor induction bynon-genotoxic chemicals, since there are currently no accurate and well-validated short-term tests to identify non-genotoxic hepatic tumorigens, thus necessitating an expensive 2-year rodent bioassay before a risk assessment can begin. The reanalysis has been carried out with log2 transformed gene expression levels of the raw signal values. The data in this Series were initially submitted in GEO Series GSE8251. The training set consists of hepatic gene expression data from 216 male Sprague-Dawley rats treated for 5 days with one of 76 structurally and mechanistically diverse nongenotoxic hepatocarcinogens and non-hepatocarcinogens. The validation set consists of 201 male Sprague-Dawley rats treated for 5 days with one of 68 structurally and mechanistically diverse non-genotoxic hepatocarcinogens and non- hepatocarcinogens. Gene expression data were generated using the Amersham Codelink Uniset Rat 1 Bioarray (GE HealthCare, Piscataway, NJ). The separation of the training set and validation set was based on the time when the microarray data were collected; i.e., microarrays processed earlier in the study were used as training and those processed later were used as validation.