Biomedical subjects

Kazunari Tsujimura

Publications and source records attributed to Kazunari Tsujimura.

4 recordsLinked to original sources

PubMed2006

Prediction of carcinogenic potential by a toxicogenomic approach using rat hepatoma cells.

The long-term rodent bioassay is the standard method to predict the carcinogenic hazard of chemicals for humans. However, this assay is costly, and the results take at least two years to produce. In the present study, we conducted gene expression profiling of cultured cells exposed to carcinogenic chemicals with the aim of providing a basis for rapid and reliable prediction of carcinogenicity using microarray technology. We selected 39 chemicals, including 17 rat hepatocarcinogens and eight compounds demonstrating carcinogenicity in organs other than the liver. The remaining 14 were non-carcinogens. When rat hepatoma cells (MH1C1) were treated with the chemicals for 3 days at a non-toxic dose, analysis of gene expression changes with our in-house microarray allowed a set of genes to be identified differentiating hepatocarcinogens from non-carcinogens, and all carcinogens from non-carcinogens, by statistical methods. Moreover, optimization of the two gene sets for classification with an SVM and LOO-CV resulted in selection of 39 genes. The highest predictivity was achieved with 207 genes for differentiation between non-hepatocarcinogens and non-carcinogens. The overlap between the two selected gene sets encompassed 26 genes. This gene set contained significant genes for prediction of carcinogenicity, with a concordance of 84.6% by LOO-CV SVM. Using nine external samples, correct prediction of carcinogenicity by SVM was 88.9%. These results indicate that short-term bioassay systems for carcinogenicity using gene expression profiling in hepatoma cells have great promise.

Animals↗

PubMed2005

Downregulation of apoptosis revealed by laser microdissection and cDNA microarray analysis of related genes in rat liver preneoplastic lesions.

Regulation of cell proliferation and apoptosis plays a key role in tumor development. To elucidate mechanisms underlying hepatocarcinogenesis, patterns of gene expression, including apoptosis-related genes, were compared between glutathione S-transferase placental form (GST-P)-positive preneoplastic foci and surrounding tissue in the rat. Lesions were induced with a single intraperitoneal injection of diethylnitrosamine (DEN, 200 mg/kg bw) and then 100 ppm 2-acetylaminofluorene (2-AAF)-containing diet combined with two-thirds partial hepatectomy. Frozen sections of the livers were applied for immunohistochemical staining of GST-P, and both positive foci and surrounding negative areas were harvested by laser microdissection. Total RNAs were extracted and amplified with T7 polymerase to allow gene expression analysis by cDNA microarray assays. In the GST-P-positive foci, altered levels were observed for many genes, mostly related to metabolism or catalysis, with increased expression of testosterone-repressive prostate message-2 (TRPM-2), which is reported to act as a protective factor against apoptosis, and decreased expression of thymus-expressed acidic protein (TEAP), which is considered to promote apoptosis. The results indicate that rat liver preneoplastic lesions might be protected against apoptosis and that the approach adopted is useful for clarification of mechanisms underlying hepatocarcinogenesis.

Alkylating Agents↗

PubMed2004

Rapid analysis of gene expression changes caused by liver carcinogens and chemopreventive agents using a newly developed three-dimensional microarray system.

We investigated changes of gene expression in livers of rats treated with carcinogens and tumor promoters using a novel three-dimensional microarray system developed by Olympus Optical Co., Ltd., to assess the feasibility of predicting modifying effects on hepatocarcinogenesis on the basis of changes in the patterns. For this purpose, two genotoxic carcinogens, two nongenotoxic carcinogens (promoters) and seven candidate chemopreventive agents were examined. Six-week-old male F344 rats were treated for 2 weeks with the 11 chemicals (0.05% phenobarbital, 0.3% clofibrate, 0.01% N-diethylnitrosamine (DEN), 0.01% 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx), 1% catechol, 1% caffeic acid, 0.05% nobiletin, 0.05% garcinol, 0.05% auraptene, 0.05% zermbone and 0.05% 1'-acetoxychavicol acetate (ACA). Test chemicals were mixed in food with the exception of DEN, which was administered in drinking water. RNAs from liver were then analyzed using two kinds of customized microarrays (PamChip(\xa8) microarray A spotted for 28 genes of drug-metabolizing enzymes in duplicate, and PamChip microarray B spotted for 131 genes which are known to be up- or down-regulated in hepatocarcinoma cells). Hybridization and subsequent analysis were usually completed within 2 h and the data obtained were highly reproducible. Carcinogens were classified into genotoxic and nongenotoxic substances by clustering analysis. We could also divide test chemicals into carcinogens and chemopreventive agents from their effects on gene expression. In this study, we have thus shown that it is feasible to predict the modifying effects of chemicals on the basis of changes of gene expression patterns after only 2 weeks of exposure, using our novel three-dimensional microarrays.

Animals↗

PubMed2003

Specific differences in gene expression profile revealed by cDNA microarray analysis of glutathione S-transferase placental form (GST-P) immunohistochemically positive rat liver foci and surrounding tissue.

Glutathione S-transferase placental form (GST-P), one of the glutathione S-transferases family of detoxification enzymes, is a very useful marker of rat liver pre-neoplastic lesions. We here investigated the gene expression profile in GST-P positive foci as compared with surrounding GST-P negative areas in the same liver of rats treated with diethylnitrosamine and then 2-acetylaminofluorene combined with partial hepatectomy. GST-P positive foci were harvested by laser microdissection and total RNAs were extracted to allow gene expression profiles to be assessed by cDNA microarray assays. Transaldolase, rat aflatoxin B1 aldehyde reductase and gamma-glutamylcysteine synthetase were found as up-regulated genes and regucalcin as a down-regulated gene, in line with findings for hepatocellular carcinomas. The results indicate that the approach adopted is useful for understanding mechanisms of hepatocarcinogenesis and identification of new markers for rat liver pre-neoplastic foci.

Animals↗