Carcinogenesis, Vol. 23, No. 10, 1685-1694,
October 2002
© 2002 Oxford University Press
CARCINOGENESIS |
Ethanol interactions with a choline-deficient, ethionine-supplemented feeding regime potentiate pre-neoplastic cellular alterations in rat liver
Western Australian Institute for Medical Research, Biochemistry and Molecular Biology, School of Biomedical and Chemical Sciences, The University of Western Australia, Crawley 6009, Australia
To examine the effect of ethanol on hepatocarcinogenesis induced by a choline-deficient, ethionine-supplemented (CDE) diet, rats were fed either an ethanol-supplemented diet or ethanol-free, isocaloric diet for 2 months, followed by a CDE diet or control diet for up to 8 months. Changes to cellular composition and pattern of gene expression in the liver were determined at 0 and 3 days, and 1, 2 and 3 weeks after commencing the CDE diet, using histological/immunochemical techniques and northern analysis. Oval cells in the liver were identified morphologically and by expression of pi-glutathione S-transferase (
-GST), alpha-fetoprotein (AFP) and the embryonic isoform of pyruvate kinase (M2-PK). Oval cell numbers and changes in the pattern of gene expression induced by the CDE diet were accelerated by pre-treatment with ethanol. At all stages, the proportion of oval cells in the test group exceeded that in controls. After 1 week, oval cells had spread sufficiently from the periportal region to be observed pericentrally in test animals and by 3 weeks, extensive formation of ductal structures was apparent, which were absent in controls. Additionally, M2-PK and AFP mRNA were detected earlier, and in greater abundance in animals pre-treated with ethanol. After 8 months of CDE treatment, one or two small hepatic foci (<10 hepatocytes), strongly positive for -GST, were detected in the liver of ethanol-pre-treated animals. These foci were absent in CDE-treated animals; however, animals pre-treated with ethanol followed by chronic CDE treatment showed increased size (>40 hepatocytes) and numbers of foci, correlating with the extent of liver damage and varying from 5 to 50% of the liver section. Our data suggest that ethanol pre-treatment potentiates the short-term effects of the CDE diet by enhancing oval cell proliferation, while chronic CDE administration enhances the appearance of pre-malignant hepatic foci that are observed with ethanol pre-treatment alone.