Like normal stem cells, tumor-initiating cells (T-ICs) are regulated extrinsically within the tumor microenvironment. Because HCC develops primarily in the context of cirrhosis, in which there is an enrichment of activated fibroblasts, we hypothesized that cancer-associated fibroblasts (CAFs) would regulate liver T-ICs. We found that the presence of α-SMA(+) CAFs correlates with poor clinical outcome. CAF-derived HGF regulates liver T-ICs via activation of FRA1 in an Erk1,2-dependent manner. Further functional analysis identifies HEY1 as a direct downstream effector of FRA1. Using the STAM NASH-HCC mouse model, we find that HGF-induced FRA1 activation is associated with the fibrosis-dependent development of HCC. Thus, targeting the CAF-derived, HGF-mediated c-Met/FRA1/HEY1 cascade may be a therapeutic strategy for the treatment of HCC.

Identification of therapeutic targets against tumor‐initiating cells (TICs) is a priority in the development of new therapeutic paradigms against cancer. We enriched a TIC population capable of tumor initiation and self‐renewal by serial passages of hepatospheres with chemotherapeutic agents. In chemoresistant hepatospheres, CD47 was found to be up‐regulated, when compared with differentiated progenies. CD47 is preferentially expressed in liver TICs, which contributed to tumor initiation, self‐renewal, and metastasis and significantly affected patients' clinical outcome. Knockdown of CD47 suppressed stem/progenitor cell characteristics. CD47+ hepatocellular carcinoma (HCC) cells preferentially secreted cathepsin S (CTSS), which regulates liver TICs through the CTSS/protease‐activated receptor 2 (PAR2) loop. Suppression of CD47 by morpholino approach suppressed growth of HCC in vivo and exerted a chemosensitization effect through blockade of CTSS/PAR2 signaling. Conclusion: These data suggest that CD47 may be an attractive therapeutic target for HCC therapy. (Hepatology 2014;60:179–191)

Sorafenib is a new standard treatment for patients with advanced hepatocellular carcinoma (HCC). However, the survival benefit of this treatment is modest, partly owing to drug resistance. Recent evidence has demonstrated the existence of tumor-initiating cells (T-ICs) as the culprit for treatment resistance. To examine whether sorafenib resistance was a result of the presence of liver T-ICs, we developed sorafenib-resistant HCC cells both in vitro and in vivo through continuous exposure to sorafenib. Using these models, we found that sorafenibresistant clones demonstrated enhanced T-IC properties, including tumorigenicity, selfrenewal, and invasiveness. In addition, several T-IC markers were found to be up-regulated, among which CD47 was found to be most significant. Using chromatin immunoprecipitation assays and expression analyses, CD47 expression was found to be regulated by nuclear factor kappa B (NF-jB) through a specific response element in the promoter of CD47, and the site occupancy and expression were increased and decreased upon stimulation and inhibition of NF-jB, respectively. Consistently, NF-jB was activated in sorafenib-resistant HCC cells, and this finding was confirmed in clinical HCC samples, which showed a positive correlation between NF-jB and CD47 expression. Functional characterization of CD47 in sorafenib-resistant HCC cells was evaluated using a lentivirus-based knockdown approach and showed increased sensitization to sorafenib upon CD47 knockdown. Furthermore, blockade of CD47 using anti-CD47 antibody (Ab) showed a similar effect. Using a patientderived HCC xenograft mouse model, we found that anti-CD47 Ab (500 lg/mouse) in combination with sorafenib (100 mg/kg, orally) exerted synergistic effects on tumor suppression, as compared with sorafenib and anti-CD47 Ab alone. Conclusions: NF-jB-mediated CD47 up-regulation promotes sorafenib resistance, and targeting CD47 in combination with sorafenib is an attractive therapeutic regimen for the treatment of HCC patients. (HEPATOLOGY 2015;62:534-545) L iver cancer (hepatocellular carcinoma; HCC) is a major malignancy worldwide, 1 and the front-line treatment for this disease is liver transplantation and surgical resection. However, most HCCs are inoperable, given that patients typically present at advanced stages, and even after surgical resection, the long-term prognosis of HCC remains unsatisfactory owing to its high recurrence rate. For advanced-staged HCC