1C). The treatment of the core Tg mice with DEN and Pb induced more severe steatosis and dysplasia (Fig. 1D, panels a and f). Administration CHIR-99021 of DEN resulted in comparable increases in the serum levels of aspartate aminotransferase (AST) and alanine aminotransferase, the markers for liver damage, in both WT and core Tg mice (data not shown) suggesting that the hepatotoxin induced comparable liver necrosis in both groups of mice. The extent of hepatocellular proliferation, as assessed by proliferating

cell nuclear antigen (PCNA) staining and liver weight, was nearly two-fold higher in the HCV core Tg mice than in WT mice under DEN/Pb treatment (Fig. 1E), indicating that dysregulated hepatocyte proliferation may be the cause of increased hepatocellular transformation in Tg mice. This difference was not apparent in carcinogen-untreated mice (Fig. 1E). To test if the livers in core RO4929097 clinical trial Tg mice had JNK and STAT3 activation, we stained tissue sections for phospho-STAT3 and phospho-JNK. The staining and phospho-STAT3 protein levels as determined by immunoblotting were clearly

increased in DEN/Pb-treated Tg mice as compared to WT mice (Fig. 1F). These results indicate that increased liver tumor development in HCV core Tg mice is associated with enhanced hepatocyte proliferation and activation of JNK and STAT3. To determine the possible role of c-jun in core-induced or core-enhanced liver oncogenesis, we bred core Tg mice with c-jun conditional knockout (c-junflox/flox) mice. The c-jun gene in this mouse line is flanked by the lox site, which will recombine to delete the c-jun gene in the presence of the Cre recombinase. We injected mice with a recombinant adenovirus that expresses Cre (A5CMVCre) to induce the deletion of the c-jun gene primarily in the liver. As a control, adenovirus expressing lacZ (Ad.LAcZ) was injected (see the experimental design in Fig. 2A). Immunoblot

and quantitative reverse transcription PCR (qRT-PCR) of c-Jun demonstrated effective c-Jun deficiency in animals which received Ad5CMVCre (Fig. 2A, lower blots and graph). The mortality 4-Aminobutyrate aminotransferase associated with DEN/Pb treatment in core Tg mice was significantly attenuated by c-Jun deficiency (Fig. 2B). Spontaneous HCC development (without DEN/Pb treatment) in core Tg mice was largely abrogated by c-Jun deficiency (Fig. 2C). The enhanced tumor incidence in the core-Tg mice treated with DEN/Pb was also reduced by 60% (P < 0.001) due to c-Jun deficiency (Fig. 2C,E), whereas a smaller 30% reduction was observed in c-Jun–deficient WT mice given DEN/Pb (Fig. 2C). The number of cells double-positive for CD133 and CD49f, which are markers for cancer stem cells, clearly increased in core Tg mice treated with DEN/Pb but not in c-Jun–deficient core Tg mice or WT mice treated with the carcinogens (Fig. 2F). Thus, our results demonstrate that HCV core protein not only serves as an independent tumor inducer, but also accentuates carcinogen-induced HCC development in a manner largely dependent on c-Jun.