title: Collaborative studies in toxicogenomics in rodent liver in JEMS·MMS; a useful application of principal component analysis on toxicogenomics.
abstract: Toxicogenomics is a rapidly developing discipline focused on the elucidation of the molecular and cellular effects of chemicals on biological systems. As a collaborative study group of Toxicogenomics/JEMS·MMS, we conducted studies on hepatocarcinogens in rodent liver in which 100 candidate marker genes were selected to discriminate genotoxic hepatocarcinogens from non-genotoxic hepatocarcinogens. Differential gene expression induced by 13 chemicals were examined using DNA microarray and quantitative real-time PCR (qPCR), including eight genotoxic hepatocarcinogens [o-aminoazotoluene, chrysene, dibenzo[a,l]pyrene, diethylnitrosamine (DEN), 7,12-dimethylbenz[a]anthracene, dimethylnitrosamine, dipropylnitrosamine and ethylnitrosourea (ENU)], four non-genotoxic hepatocarcinogens [carbon tetrachloride, di(2-ethylhexyl)phthalate (DEHP), phenobarbital and trichloroethylene] and a non-genotoxic non-hepatocarcinogen [ethanol]. Using qPCR, 30 key genes were extracted from mouse livers at 4 h and 28 days following dose-dependent gene expression alteration induced by DEN and ENU: the most significant changes in gene expression were observed at 4 h. Next, we selected key point times at 4 and 48 h from changes in time-dependent gene expression during the acute phase following administration of chrysene by qPCR. We successfully showed discrimination of eight genotoxic hepatocarcinogens [2-acetylaminofluorene, 2,4-diaminotoluene, diisopropanolnitrosamine, 4-dimethylaminoazobenzene, 4-(methylnitsosamino)-1-(3-pyridyl)-1-butanone, N-nitrosomorpholine, quinoline and urethane] from four non-genotoxic hepatocarcinogens [1,4-dichlorobenzene, dichlorodiphenyltrichloroethane, DEHP and furan] using qPCR and principal component analysis. Additionally, we successfully identified two rat genotoxic hepatocarcinogens [DEN and 2,6-dinitrotoluene] from a nongenotoxic-hepatocarcinogen [DEHP] and a non-genotoxic non-hepatocarcinogen [phenacetin] at 4 and 48 h. The subsequent gene pathway analysis by Ingenuity Pathway Analysis extracted the DNA damage response, resulting from the signal transduction of a p53-class mediator leading to the induction of apoptosis. The present review of these studies suggests that application of principal component analysis on the gene expression profile in rodent liver during the acute phase is useful to predict genotoxic hepatocarcinogens in comparison to non-genotoxic hepatocarcinogens and/or non-carcinogenic hepatotoxins.
authors.affiliation: School of Science and Engineering, Aoyama Gakuin University, Sagamihara, Kanagawa 252-5258 Japan ; Division of Molecular Target and Gene Therapy Products, National Institute of Health Sciences, Setagaya-ku, Tokyo, 158-8501 Japan.
authors.forename: Chie
authors.initials: C
authors.lastname: Furihata
authors.affiliation: School of Science and Engineering, Aoyama Gakuin University, Sagamihara, Kanagawa 252-5258 Japan ; Laboratory for Integrative Genomics, RIKEN Center for Integrative Genomics, RIKEN Yokohama Institute, 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama, 230-0045 Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Watanabe
authors.affiliation: Division of Molecular Target and Gene Therapy Products, National Institute of Health Sciences, Setagaya-ku, Tokyo, 158-8501 Japan.
authors.forename: Takayoshi
authors.initials: T
authors.lastname: Suzuki
authors.affiliation: Nonclinical Research Center, Drug Development Service Segment, LSI Medience Corporation, Kamisu-shi, Ibaraki 314-0255 Japan.
authors.forename: Shuichi
authors.initials: S
authors.lastname: Hamada
authors.affiliation: Genetic Toxicology Group, Biosafety Research Center, Foods, Drugs, and Pesticides, Shioshinden 582-2, Fukude-cho, Iwata-gun, Shizuoka 437-1213 Japan ; Education and Research Department, University of Shizuoka, Shizuoka, 422-8526 Japan.
authors.forename: Madoka
authors.initials: M
authors.lastname: Nakajima
keywords: DNA microarray; Gene network; Hepatocarcinogen; Principal component analysis; Quantitative real-time PCR; Rodent liver; Toxicogenomics