title: Development and evaluation of a genomic signature for the prediction and mechanistic assessment of nongenotoxic hepatocarcinogens in the rat.
abstract: Evaluating the risk of chemical carcinogenesis has long been a challenge owing to the protracted nature of the pathology and the limited translatability of animal models. Although numerous short-term in vitro and in vivo assays have been developed, they have failed to reliably predict the carcinogenicity of nongenotoxic compounds. Extending upon previous microarray work (Fielden, M. R., Nie, A., McMillian, M., Elangbam, C. S., Trela, B. A., Yang, Y., Dunn, R. T., II, Dragan, Y., Fransson-Stehen, R., Bogdanffy, M., et al. (2008). Interlaboratory evaluation of genomic signatures for predicting carcinogenicity in the rat. Toxicol. Sci. 103, 28-34), we have developed and extensively evaluated a quantitative PCR-based signature to predict the potential for nongenotoxic compounds to induce liver tumors in the rat as a first step in the safety assessment of potential nongenotoxic carcinogens. The training set was derived from liver RNA from rats treated with 72 compounds and used to develop a 22-gene signature on the TaqMan array platform, providing an economical and standardized assay protocol. Independent testing on over 900 diverse samples (66 compounds) confirmed the interlaboratory precision of the assay and its ability to predict known nongenotoxic hepatocarcinogens (NGHCs). When tested under different experimental designs, strains, time points, dose setting criteria, and other preanalytical processes, the signature sensitivity and specificity was estimated to be 67% (95% confidence interval [CI] = 38-88%) and 59% (95% CI = 44-72%), respectively, with an area under the receiver operating characteristic curve of 0.65 (95% CI = 0.46-0.83%). Compounds were best classified using expression data from short-term repeat dose studies; however, the prognostic expression changes appeared to be preserved after longer term treatment. Exploratory evaluations also revealed that different modes of action for nongenotoxic and genotoxic compounds can be discriminated based on the expression of specific genes. These results support a potential early preclinical testing paradigm to catalyze broader understanding of putative NGHCs.
authors.affiliation: Comparative Biology and Safety Sciences, Amgen, South San Francisco, California 94080, USA. mfielden@amgen.com
authors.forename: Mark R
authors.initials: MR
authors.lastname: Fielden
authors.forename: Alex
authors.initials: A
authors.lastname: Adai
authors.forename: Robert T
authors.initials: RT
authors.lastname: Dunn
authors.forename: Andrew
authors.initials: A
authors.lastname: Olaharski
authors.forename: George
authors.initials: G
authors.lastname: Searfoss
authors.forename: Joe
authors.initials: J
authors.lastname: Sina
authors.forename: Jiri
authors.initials: J
authors.lastname: Aubrecht
authors.forename: Eric
authors.initials: E
authors.lastname: Boitier
authors.forename: Paul
authors.initials: P
authors.lastname: Nioi
authors.forename: Scott
authors.initials: S
authors.lastname: Auerbach
authors.forename: David
authors.initials: D
authors.lastname: Jacobson-Kram
authors.forename: Nandini
authors.initials: N
authors.lastname: Raghavan
authors.forename: Yi
authors.initials: Y
authors.lastname: Yang
authors.forename: Andrew
authors.initials: A
authors.lastname: Kincaid
authors.forename: Jon
authors.initials: J
authors.lastname: Sherlock
authors.forename: Shen-Jue
authors.initials: SJ
authors.lastname: Chen
authors.forename: Bruce
authors.initials: B
authors.lastname: Car
mesh_terms: D000818:Animals; D002273:Carcinogens / Q000145:classification / Q000633:toxicity*; D020869:Gene Expression Profiling; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D005819:Genetic Markers; D023281:Genomics; D008099:Liver / Q000187:drug effects* / Q000378:metabolism; D008114:Liver Neoplasms, Experimental / Q000139:chemically induced* / Q000235:genetics; D008297:Male; D008957:Models, Genetic; D011237:Predictive Value of Tests; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D002273:Carcinogens; D005819:Genetic Markers