title: A metabolomics investigation of non-genotoxic carcinogenicity in the rat.
abstract: Non-genotoxic carcinogens (NGCs) promote tumor growth by altering gene expression, which ultimately leads to cancer without directly causing a change in DNA sequence. As a result NGCs are not detected in mutagenesis assays. While there are proposed biomarkers of carcinogenic potential, the definitive identification of non-genotoxic carcinogens still rests with the rat and mouse long-term bioassay. Such assays are expensive and time-consuming and require a large number of animals, and their relevance to human health risk assessments is debatable. Metabolomics and lipidomics in combination with pathology and clinical chemistry were used to profile perturbations produced by 10 compounds that represented a range of rat non-genotoxic hepatocarcinogens (NGC), non-genotoxic non-hepatocarcinogens (non-NGC), and a genotoxic hepatocarcinogen. Each compound was administered at its maximum tolerated dose level for 7, 28, and 91 days to male Fisher 344 rats. Changes in liver metabolite concentration differentiated the treated groups across different time points. The most significant differences were driven by pharmacological mode of action, specifically by the peroxisome proliferator activated receptor alpha (PPAR-α) agonists. Despite these dominant effects, good predictions could be made when differentiating NGCs from non-NGCs. Predictive ability measured by leave one out cross validation was 87% and 77% after 28 days of dosing for NGCs and non-NGCs, respectively. Among the discriminatory metabolites we identified free fatty acids, phospholipids, and triacylglycerols, as well as precursors of eicosanoid and the products of reactive oxygen species linked to processes of inflammation, proliferation, and oxidative stress. Thus, metabolic profiling is able to identify changes due to the pharmacological mode of action of xenobiotics and contribute to early screening for non-genotoxic potential.
authors.affiliation: Medical Research Council Human Nutrition Research (MRC HNR), Elsie Widdowson Laboratory , 120 Fulbourn Road, Cambridge CB1 9NL, U.K. , The Department of Biochemistry, University of Cambridge , 80 Tennis Court Road, Cambridge CB2 1GA, U.K. , and Cambridge Systems Biology Centre (CSBC), University of Cambridge , Cambridge CB2 1QR, U.K.
authors.forename: Zsuzsanna
authors.initials: Z
authors.lastname: Ament
authors.forename: Claire L
authors.initials: CL
authors.lastname: Waterman
authors.forename: James A
authors.initials: JA
authors.lastname: West
authors.forename: Catherine
authors.initials: C
authors.lastname: Waterfield
authors.forename: Richard A
authors.initials: RA
authors.lastname: Currie
authors.forename: Jayne
authors.initials: J
authors.lastname: Wright
authors.forename: Julian L
authors.initials: JL
authors.lastname: Griffin
mesh_terms: D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D002273:Carcinogens / Q000145:classification / Q000633:toxicity*; D004249:DNA Damage; D015777:Eicosanoids / Q000378:metabolism; D005230:Fatty Acids, Nonesterified / Q000378:metabolism; D015870:Gene Expression; D006801:Humans; D050356:Lipid Metabolism / Q000187:drug effects; D008099:Liver / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D008114:Liver Neoplasms, Experimental / Q000139:chemically induced / Q000378:metabolism* / Q000473:pathology; D008297:Male; D055432:Metabolomics; D009153:Mutagens / Q000145:classification / Q000633:toxicity*; D047493:PPAR alpha / Q000819:agonists / Q000235:genetics / Q000378:metabolism; D010743:Phospholipids / Q000378:metabolism; D051381:Rats; D011916:Rats, Inbred F344; D017382:Reactive Oxygen Species / Q000378:metabolism; D014280:Triglycerides / Q000378:metabolism
chemical_list: D015415:Biomarkers; D002273:Carcinogens; D015777:Eicosanoids; D005230:Fatty Acids, Nonesterified; D009153:Mutagens; D047493:PPAR alpha; D010743:Phospholipids; D017382:Reactive Oxygen Species; D014280:Triglycerides