Increased sensitivity to the hepatocarcinogen diethylnitrosamine in transgenic mice carrying the hepatitis B virusX gene

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Abstract
The role of the hepatitis B virus (HBV) X protein in liver tumorigenesis is unresolved. Transgenic mice harboring the X gene (nt 1376–1840 under the control of the human α-1-antitrypsin regulatory elements) (ATX mice) display only minor histopathologic alterations of the liver. To determine if ATX mice are more susceptible to the effects of hepatocarcinogens, 12- to 15-d-old male ATX and control littermate mice were injected with a single dose (2 μg/g body weight) of diethylnitrosamine (DEN). The animals were killed 6–10 mo after exposure and were analyzed for histological changes in the liver. One hundred percent of the DEN-treated ATX mice developed abnormal liver lesions. When their liver tissues were compared by stereological analysis with those of non-transgenic animals, the ATX mice had a relative twofold increase in the total number of focal lesions and a twofold increase in the incidence of hepatocellular carcinoma. Elevated levels of X protein and p53 protein were not detected in carcinogen-induced nodules or tumors. These results are consistent with a model in which the expression of the HBV X protein potentiates the induction of DEN-mediated liver disease.