Journal Article

Detection of early gene expression changes by differential display in the livers of mice exposed to dichloroacetic acid

Sheau-Fung Thai, James W. Allen, Anthony B. DeAngelo, Michael H. George and James C. Fuscoe

in Carcinogenesis

Volume 22, issue 8, pages 1317-1322
Published in print August 2001 | ISSN: 0143-3334
Published online August 2001 | e-ISSN: 1460-2180 | DOI: http://dx.doi.org/10.1093/carcin/22.8.1317
Detection of early gene expression changes by differential display in the livers of mice exposed to dichloroacetic acid

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Dichloroacetic acid (DCA) is a major by-product of water disinfection by chlorination. Several studies have demonstrated the hepatocarcinogenicity of DCA in mice when administered in drinking water. The mechanism of DCA carcinogenicity is not clear and we speculate that changes in gene expression may be important. In order to analyze early changes in gene expression induced by DCA treatment we used the differential display method. Mice were treated with 2 g/l DCA in drinking water for 4 weeks. Total RNAs were obtained from livers of both control and treated mice for analysis. Of ~48 000 bands on the differential display gels representing an estimated 96% of RNA species, 381 showed differences in intensity. After cloning and confirmation by both reverse-northern and northern analyses, six differentially expressed genes were found. The expression of five of these genes was suppressed in the DCA-treated mice while one was induced. After sequencing, four genes were identified and two were matched to expressed sequence tags through the BLAST program. These genes are alpha-1 protease inhibitor, cytochrome b5, stearoyl-CoA desaturase and carboxylesterase. Stearoyl-CoA desaturase was induced ~3-fold in the livers of DCA-treated mice and the other three genes were suppressed approximately 3-fold. Stearoyl-CoA desaturase, cytochrome b5 and carboxylesterase are endoplasmic reticulum membrane-bound enzymes involved in fatty acid metabolism. The expression pattern of four of these genes was similar in DCA-induced hepatocellular carcinomas and the 4 week DCA-treated mouse livers. The expression of stearoyl-CoA desaturase and one of the unidentified genes returned to control levels in the carcinomas. Understanding the roles and interactions between these genes may shed light on the mechanism of DCA carcinogenesis.

Keywords: DCA, dichloroacetic acid; DD, differentially displayed; EST, expressed sequence tag; GAPDH, glyceraldehyde 3-phosphate dehydrogenase; MDD, mean daily dosage.

Journal Article.  5224 words.  Illustrated.

Subjects: Clinical Cytogenetics and Molecular Genetics

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