Genetic dissection of the HBV pX transactivation, apoptotic and tumor promoting function. Isolation and characterization of mutated HBV pX proteins from HBV patients. Generation of transgenic animals, expressing wt or mutated HBV pX in liver or in mammary gland epithelial cells.
The HBV encoded pX protein plays a major role in the development of hepatocellular carcinoma by either modulating the susceptibility of the infected cells to apoptosis or by inducing uncontrolled cell growth. Although hepatocellular carcinoma is the most prevalent human cancer, only a minority of patients suffering from chronic viral hepatitis undergoes neoplastic transformation indicating that pX synthesis per se is not sufficient to induce tumor formation. Cell transformation may require either activation of cellular oncogenes or alteration of the expression level of cellular genes involved in the regulation of apoptotic cell death of hepatocytes. In addition the HBV undergoes a high rate of spontaneous mutations in chronically infected individuals. Thus the possibility exists that transformation may be linked to the emergence of mutant pX proteins more than to the expression of the wild type pX protein. In the concerted action, both hypothesis will be tested in transgenic animals and in tissue culture cell lines. The identification of co-oncogenic events will be pursued by pairing wild type HBV-X mice either with transgenic animals expressing known oncogenes to generate double transgenic mice or with knock-out mice lacking key modulators of apoptotic cell death. To access the role of pX variability the pX gene will be cloned from a panel of HBV patients with different clinical outcome. Naturally occurring mutants will be tested in vitro to select functionally relevant mutations which will be used to generate transgenic mice and to test in vivo their transforming potential.
Hepatitis B virus (HBV), pX protein, mutant pX proteins, hepatocellular carcinoma, transgenic animals, cell transformation, apoptosis.