There is an urgent need to understand the molecular signaling pathways that drive or mediate the development of hepatocellular carcinoma (HCC). The focal adhesion kinase (FAK) gene protein tyrosine kinase 2 is amplified in 16.4% of The Cancer Genome Atlas HCC specimens, and its amplification leads to increased FAK mRNA expression. It is not known whether the overexpression of FAK alone is sufficient to induce HCC or whether it must cooperate in some ways with other oncogenes. In this study, we found that 34.8% of human HCC samples with FAK amplification also show β-catenin mutations, suggesting a co-occurrence of FAK overexpression and β-catenin mutations in HCC. We overexpressed FAK alone, constitutively active forms of β-catenin (CAT) alone, or a combination of FAK and CAT in the livers of C57/BL6 mice. We found that overexpression of both FAK and CAT, but neither FAK nor CAT alone, in mouse livers was sufficient to lead to tumorigenesis. We further demonstrated that FAK's kinase activity is required for FAK/CAT-induced tumorigenesis. Furthermore, we performed RNA-sequencing analysis to identify the genes/signaling pathways regulated by FAK, CAT, or FAK/CAT. We found that FAK overexpression dramatically enhances binding of β-catenin to the promoter of androgen receptor (AR), which leads to increased expression of AR in mouse livers. Moreover, ASC-J9, an AR degradation enhancer, suppressed FAK/ CAT-induced HCC formation. Conclusion: FAK overexpression and β-catenin mutations often co-occur in human HCC tissues. Co-overexpression of FAK and CAT leads to HCC formation in mice through increased expression of AR; this mouse model may be useful for further studies of the molecular mechanisms in the pathogenesis of HCC and could lead to the identification of therapeutic targets.

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Hepatocellular carcinoma (HCC) is the fifth most common primary cancer and second largest cause of cancer‐related death worldwide. The first‐line oral chemotherapeutic agent sorafenib only increases survival in patients with advanced HCC by less than 3 months. Most patients with advanced HCC have shown limited response rates and survival benefits with sorafenib. Although sorafenib is an inhibitor of multiple kinases, including serine/threonine‐protein kinase c‐Raf, serine/threonine‐protein kinase B‐Raf, vascular endothelial growth factor receptor (VEGFR)‐1, VEGFR‐2, VEGFR‐3, and platelet‐derived growth factor receptor β, HCC cells are able to escape from sorafenib treatment using other pathways that the drug insufficiently inhibits. The aim of this study was to identify and target survival and proliferation pathways that enable HCC to escape the antitumor activity of sorafenib. We found that insulin‐like growth factor 1 receptor (IGF1R) remains activated in HCC cells treated with sorafenib. Knockdown of IGF1R sensitizes HCC cells to sorafenib treatment and decreases protein kinase B (AKT) activation. Overexpression of constitutively activated AKT reverses the effect of knockdown of IGF1R in sensitizing HCC cells to treatment with sorafenib. Further, we found that ceritinib, a drug approved by the U.S. Food and Drug Administration for treatment of non‐small cell lung cancer, effectively inhibits the IGF1R/AKT pathway and enhances the inhibitory efficacy of sorafenib in human HCC cell growth and survival in vitro, in a xenograft mouse model and in the c‐Met/β‐catenin‐driven HCC mouse model. Conclusion: Our study provides a biochemical basis for evaluation of a new combination treatment that includes IGF1R inhibitors, such as ceritinib and sorafenib, in patients with HCC. (Hepatology Communications 2018;2:732‐746)

It is critical to understand the molecular mechanisms of hepatocarcinogenesis in order to prevent or treat hepatocellular carcinoma (HCC). The development of HCC is commonly associated with hepatocyte death and compensatory proliferation. However, the role of Caspase-3, a key apoptotic executor, in hepatocarcinogenesis is unknown. In this study, we used Caspase-3-deficient mice to examine the role of Caspase-3 in hepatocarcinogenesis in a chemical (diethylnitrosamine, DEN)-induced HCC model. We found that Caspase-3 deficiency significantly increased DEN-induced HCC. Unexpectedly, Caspase-3 deficiency increased apoptosis induced by DEN and the subsequent compensatory proliferation. Intriguingly, we discovered that Caspase-3 deficiency increased the activation of p38 with and without DEN treatment. Moreover, we demonstrated that TNFα and IL1α stimulated increased activation of p38 in Caspase-3 KO hepatocytes compared with wild-type hepatocytes. Finally, we found that inhibition of p38 by SB202190 abrogated enhanced hepatocyte death, compensatory proliferation and HCC induced by DEN in Caspase-3-deficient mice. Overall, our data suggest that Caspase-3 inhibits chemical-induced hepatocarcinogenesis by suppressing p38 activation and hepatocyte death.