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Open Access Genetic Resistance to Chemical Hepatocarcinogenesis in the DRH Rat Strain

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The carcinogen-resistant inbred rat strain DRH established from closed-colony Donryu rats by use of selective brother-sister mating over 20 generations under continuous feeding of 3′-methyl-4-dimethylaminoazobenzene (3′-Me-DAB) maintains a highly resistant phenotype without carcinogen exposure for many years. We reported that the clonal expansion of preneoplastic glutathione S-transferase-P(GST-P)-positive foci induced by 3′-Me-DAB was less extensive in the liver of DRH rats than in the liver of susceptible strains, such as Donryu and F344, although levels of DNA adducts were comparable among these rats. Comparative studies of the events after initiation indicate that DRH rats are constitutionally less prone to cellular damage caused by continuous administration of 3′-Me-DAB than are parental Donryu rats. Consequently, the reduced growth response of the liver during the promotion stage may contribute to the low susceptibility to development of liver tumors. Genetic analysis of (F344 × DRH)F2 rats identified two quantitative trait loci, Drh1 on chromosome 1 and Drh2 on chromosome 4, which provide resistance to the development of GST-P-positive preneoplastic foci induced by 3′-Me-DAB during the early stage of its administration. The resistance to progression to hepatocellular carcinoma is affected solely by Drh2. These observations indicate that at least two genetic loci are critically involved in the steps leading to chemical hepatocarcinogenesis. The DRH rat is a useful experimental model with which to study genetic susceptibility and resistance to chemically induced liver cancers.

Document Type: Research Article

Affiliations: 1: Department of Pathology and Biology of Diseases, Kyoto University Graduate School of Medicine, Yoshida-konoe-cho, Sakyo-ku, Kyoto 606-8501 2: Department of Oncological Pathology, Cancer Center, Nara Medical University, Kashiwara, Nara 634-8522 3: College of Nutrition, Koshien University, Takarazuka 6650006, Japan

Publication date: August 1, 2004

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  • Comparative Medicine (CM), an international journal of comparative and experimental medicine, is the leading English-language publication in the field and is ranked by the Science Citation Index in the upper third of all scientific journals. The mission of CM is to disseminate high-quality, peer-reviewed information that expands biomedical knowledge and promotes human and animal health through the study of laboratory animal disease, animal models of disease, and basic biologic mechanisms related to disease in people and animals.

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