Our results indicate that HBx does not seem to cooperate with constitutively active NRAS
to induce liver tumorigenesis in HBx/NRAS animals. This was evident from the relatively low ALT levels in serum (Table 1), the low tumor multiplicity, and the liver weight http://www.selleckchem.com/products/gsk2126458.html to whole mass percentage (Fig. 3A,B) in HBx/NRAS mice. HBx has been suggested to up-regulate the Ras signaling pathway.17 Perhaps HBx expression and activated Ras are redundant in this transformation assay. Even when all the transgenes were coinjected (HBx/NRAS/shp53), there was only a marginally significant increase (P < 0.05) in tumorigenicity in comparison with HBx alone. Moreover, no significant increase in tumorigenicity was seen in HBx/NRAS animals versus animals with NRAS alone (Fig. 3A). Our results indicate that HBx up-regulates the Wnt signaling pathway, and this may play a role in liver tumorigenesis (Fig. 4), whereas constitutively active NRAS seems to induce hyperplasia, probably via the
RAF/mitogen-activated protein kinase kinase/extracellular signal-regulated kinase and/or phosphoinositide 3-kinase (PI3K)/v-akt murine thymoma see more viral oncogene homolog 1 (AKT) associated pathways (Fig. 5). In addition, we detected high levels of CD45-positive staining cells in livers of animals injected with HBx alone or in combination with other transgenes (Supporting Information Fig. 4). These cells could represent infiltrating lymphocytes, which are often associated with HBV infection. Indeed, the HBx protein would be predicted to act as a foreign antigen in our system, unlike previously reported HBx transgenic mouse models. HBx-induced inflammation may play some selleck products role in HCC progression; this hypothesis could be tested
with our model. Elevated pAkt levels were detected by IHC in experimental animals injected with NRAS alone or in combination with shp53, and this indicates that NRAS is likely signaling via the Pi3k/Akt pathway (Fig. 5). HBx has been previously shown to activate the WNT/CTNNB1 signaling pathway in human hepatoma cell lines.8HBx antigen has also been associated with the accumulation of CTNNB1 in the cytoplasm and/or nucleus and the up-regulation of the HBx antigen effector up-regulated gene 11, which results in increased activation of CTNNB1.18 The CTNNB1 staining pattern can be correlated with the histopathological types of liver tumors.19 The absence of nuclear staining and strong membranous staining with rare, weak cytoplasmic expression of Ctnnb1 suggested that the hyperplastic nodules induced by HBx or HBx/shp53 were adenocarcinomas or poorly differentiated HCC (Fig. 4). We did not detect any activation of Stat3 in liver tumors expressing HBx by IHC in our experimental cohorts with a phospho-Stat3 (Tyr705)–specific antibody (data not shown) despite the previous suggestion that HBx activates Stat3.