title: Biological networks for predicting chemical hepatocarcinogenicity using gene expression data from treated mice and relevance across human and rat species.
abstract: BACKGROUND
  Several groups have employed genomic data from subchronic chemical toxicity studies in rodents (90 days) to derive gene-centric predictors of chronic toxicity and carcinogenicity. Genes are annotated to belong to biological processes or molecular pathways that are mechanistically well understood and are described in public databases.
  
  
  OBJECTIVE
  To develop a molecular pathway-based prediction model of long term hepatocarcinogenicity using 90-day gene expression data and to evaluate the performance of this model with respect to both intra-species, dose-dependent and cross-species predictions.
  
  
  METHODS
  Genome-wide hepatic mRNA expression was retrospectively measured in B6C3F1 mice following subchronic exposure to twenty-six (26) chemicals (10 were positive, 2 equivocal and 14 negative for liver tumors) previously studied by the US National Toxicology Program. Using these data, a pathway-based predictor model for long-term liver cancer risk was derived using random forests. The prediction model was independently validated on test sets associated with liver cancer risk obtained from mice, rats and humans.
  
  
  RESULTS
  Using 5-fold cross validation, the developed prediction model had reasonable predictive performance with the area under receiver-operator curve (AUC) equal to 0.66. The developed prediction model was then used to extrapolate the results to data associated with rat and human liver cancer. The extrapolated model worked well for both extrapolated species (AUC value of 0.74 for rats and 0.91 for humans). The prediction models implied a balanced interplay between all pathway responses leading to carcinogenicity predictions.
  
  
  CONCLUSIONS
  Pathway-based prediction models estimated from sub-chronic data hold promise for predicting long-term carcinogenicity and also for its ability to extrapolate results across multiple species.
authors.affiliation: Division of Environmental Health Sciences, School of Public Health, University of California, Berkeley, California, USA.
authors.forename: Reuben
authors.initials: R
authors.lastname: Thomas
authors.forename: Russell S
authors.initials: RS
authors.lastname: Thomas
authors.forename: Scott S
authors.initials: SS
authors.lastname: Auerbach
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Portier
mesh_terms: D000465:Algorithms; D000818:Animals; D001681:Biological Assay; D063646:Carcinogenesis / Q000139:chemically induced*; D019295:Computational Biology / Q000379:methods*; D030541:Databases, Genetic; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D008099:Liver / Q000187:drug effects* / Q000378:metabolism*; D008113:Liver Neoplasms / Q000139:chemically induced / Q000235:genetics / Q000473:pathology; D051379:Mice; D015233:Models, Statistical; D012372:ROC Curve; D051381:Rats; D013045:Species Specificity; D059467:Transcriptome / Q000187:drug effects*