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DETECTION OF EARLY GENE EXPRESSION CHANGES BY DIFFERENTIAL DISPLAY IN THE LIVERS OF MICE EXPOSED TO DICHLOROACETIC ACID
Citation:
Thai, S. F., J W. Allen, A B. DeAngelo, M H. George, AND J C. Fuscoe. DETECTION OF EARLY GENE EXPRESSION CHANGES BY DIFFERENTIAL DISPLAY IN THE LIVERS OF MICE EXPOSED TO DICHLOROACETIC ACID. CARCINOGENESIS 22(8):1317-1322, (2001).
Description:
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 treatments we used the differential display method. Mice were treated with DCA (2g/l) in drinking water for four weeks. Total RNAs were otained from livers of both control and treated mice for analysis. Of approximately 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 iduced about 3-fold in the livers of DCA-treated mice, and the other three genes were suppressed about 3-fold. Stearoyl-CoA desaturase, cytochrome b5 and carboxylesterase are endoplasmic reticulum membrane-bound enzymes involved in fatty acid metabolism. The expression pattern of 4 of these genes was similar in DCA-induced hepatocellular carcinomas and the four-week DCA-treated mouse livers. The expression of stearoyl-CoA desaturase and one of the unidentified genes returned to control leverls in the carcinomas. Understanding of the roles and the interactions between these genes may shed light on the mechanism of DCA carcinogenesis.