IN VITRO SYSTEMS Benzo[a]pyrene-induced transcriptomic responses in primary hepatocytes and in vivo liver: Toxicokinetics is essential for in vivo–in vitro comparisons P. C. E. van Kesteren • P. E. Zwart • M. M. Schaap • T. E. Pronk • M. H. M. van Herwijnen • J. C. S. Kleinjans • B. G. H. Bokkers • R. W. L. Godschalk • M. J. Zeilmaker • H. van Steeg • M. Luijten Received: 20 July 2012 / Accepted: 18 September 2012 / Published online: 2 October 2012 Ó Springer-Verlag Berlin Heidelberg 2012 Abstract The traditional 2-year cancer bioassay needs replacement by more cost-effective and predictive tests. The use of toxicogenomics in an in vitro system may provide a more high-throughput method to investigate early alterations induced by carcinogens. Recently, the differential gene expression response in wild-type and cancer-prone Xpa -/- p53 ?/- primary mouse hepatocytes after exposure to benzo[a]pyrene (B[a]P) revealed downregulation of cancer- related pathways in Xpa -/- p53 ?/- hepatocytes only. Here, we investigated pathway regulation upon in vivo B[a]P exposure of wild-type and Xpa -/- p53 ?/- mice. In vivo transcriptomics analysis revealed a limited gene expression response in mouse livers, but with a significant induction of DNA replication and apoptotic/anti-apoptotic cellular responses in Xpa -/- p53 ?/- livers only. In order to be able to make a meaningful in vivo–in vitro comparison we estimated internal in vivo B[a]P concentrations using DNA adduct levels and physiologically based kinetic modeling. Based on these results, the in vitro concentration that corresponded best with the internal in vivo dose was chosen. Comparison of in vivo and in vitro data demonstrated similarities in transcri- ptomics response: xenobiotic metabolism, lipid metabolism and oxidative stress. However, we were unable to detect cancer-related pathways in either wild-type or Xpa -/- p53 ?/- exposed livers, which were previously found to be induced by B[a]P in Xpa -/- p53 ?/- primary hepatocytes. In conclusion, we showed parallels in gene expression responses between livers and primary hepatocytes upon exposure to equivalent concentrations of B[a]P. Furthermore, we recommend con- sidering toxicokinetics when modeling a complex in vivo endpoint with in vitro models. Keywords Toxicogenomics Á Carcinogenesis Á Benzo[a]pyrene Á Xpa -/- p53 ?/- Á Physiologically based kinetic modeling Abbreviations ANOVA Analysis of variance B[a]P Benzo[a]pyrene BPDE Benzo[a]pyrene-7,8-diol-9,10-epoxide GI Gastrointestinal FDR False discovery rate GenMAPP Gene Map Annotator and Pathway Profiler GO Gene Ontology KEGG Kyoto Encyclopedia of Genes and Genomes Electronic supplementary material The online version of this article (doi:10.1007/s00204-012-0949-5) contains supplementary material, which is available to authorized users. P. C. E. van Kesteren Á P. E. Zwart Á M. M. Schaap Á T. E. Pronk Á H. van Steeg Á M. Luijten (&) Laboratory for Health Protection Research, National Institute for Public Health and the Environment, P.O. Box 1, 3720 BA Bilthoven, The Netherlands e-mail: mirjam.luijten@rivm.nl P. C. E. van Kesteren Á T. E. Pronk Á M. H. M. van Herwijnen Á J. C. S. Kleinjans Department of Toxicogenomics, Maastricht University, Maastricht, The Netherlands M. M. Schaap Á H. van Steeg Department of Toxicogenetics, Leiden University Medical Center (LUMC), Leiden, The Netherlands B. G. H. Bokkers Á M. J. Zeilmaker Centre for Substances and Integral Risk Assessment, National Institute for Public Health and the Environment (RIVM), Bilthoven, The Netherlands R. W. L. Godschalk Department of Toxicology, School for Nutrition, Toxicology and Metabolism (NUTRIM), Maastricht University, Maastricht, The Netherlands 123 Arch Toxicol (2013) 87:505–515 DOI 10.1007/s00204-012-0949-5