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.

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

Frequent relapse and drug resistance in patients with hepatocellular carcinoma (HCC) can be attributed to the existence of tumor-initiating cells (TIC) within the tumor bulk. Therefore, targeting liver TICs may improve the prognosis of these patients. From transcriptome sequencing of 16 pairs of clinical HCC samples, we report that interleukin-1 receptor-associated kinase 1 (IRAK1) in the TLR/IRAK pathway is significantly upregulated in HCC. IRAK1 overexpression in HCC was further confirmed at the mRNA and protein levels and correlated with advanced tumor stages and poor patient survival. Interestingly, IRAK4, an upstream regulator of IRAK1, was also consistently upregulated. IRAK1 regulated liver TIC properties, including self-renewal, tumorigenicity, and liver TIC marker expression. IRAK1 inhibition sensitized HCC cells to doxorubicin and sorafenib treatment via suppression of the apoptotic cascade. Pharmacological inhibition of IRAK1 with a specific IRAK1/4 kinase inhibitor consistently suppressed liver TIC populations. We identified aldo-keto reductase family 1 member 10 (AKR1B10) as a novel downstream target of IRAK1, which was found to be overexpressed in HCC and significantly correlated with IRAK1 expression. Knockdown of AKR1B10 negated IRAK1-induced TIC functions via modulation of the AP-1 complex. Inhibition of IRAK1/4 inhibitor in combination with sorafenib synergistically suppressed tumor growth in an HCC xenograft model. In conclusion, targeting the IRAK4/IRAK1/AP-1/AKR1B10 signaling pathway may be a potential therapeutic strategy against HCC. IRAK4/IRAK1/AP-1/AKR1B10 signaling pathway regulates cancer stemness and drug resistance and may be a novel therapeutic target in HCC. .