The E3 ubiquitin ligase Fbxw7 functions as a general tumor suppressor by targeting several well-known oncoproteins for ubiquitination and proteasomal degradation. However, the clinical significance of Fbxw7 and the mechanisms involved in the anti-cancer effect of Fbxw7 in HCC are not clear. The Fbxw7 and YAP expression in 60 samples of surgical resected HCC and matched normal tumor-adjacent tissues were assessed using IHC or immunoblotting. Flow cytometry, caspase 3/7 activity assay, BrdU cell proliferation assay and MTT assay were used to detect proliferation and apoptosis of HCC cells. The regulatory effect of Fbxw7 on YAP in HCC cells was confirmed by qRT-PCR, immunoblotting and immunofluorescence. Co-immunoprecipitation was used to analyze interaction between YAP and Fbxw7. Nude mice subcutaneous injection, Ki-67 staining and TUNEL assay were used to evaluate tumor growth and apoptosis in vivo. In this study, we found that Fbxw7 expression was impaired in HCC tissues and loss of Fbxw7 expression was correlated with poor clinicopathological features including large tumor size, venous infiltration, high pathological grading and advanced TNM stage. Additionally, we demonstrated that patients with positive Fbxw7 expression had a better 5-year survival and Fbxw7 was an independent factor for predicting the prognosis of HCC patients. We confirmed that Fbxw7 inhibited HCC by inducing both apoptosis and growth arrest. Elevated YAP expression was observed in the same cohort of HCC tissues. Pearson's correlation coefficient analysis indicated that Fbxw7 was inversely associated with YAP protein expression in HCC tissues. We also found that Fbxw7 regulated YAP protein abundance by targeting YAP for ubiquitination and proteasomal degradation in HCC. Furthermore, restoring YAP expression partially abrogated Fbxw7 induced HCC cell apoptosis and growth arrest in vitro and in vivo. These results indicate that Fbxw7 may serve as a prognostic marker and that YAP may be a potential target of Fbxw7 in HCC.

Sterol regulatory element-binding protein 1 (SREBP-1) is a well-known nuclear transcription factor involved in lipid synthesis. Recent studies have focused on its functions in tumor cell proliferation and apoptosis, but its role in cell migration and invasion, especially in hepatocellular carcinoma (HCC), is still unclear. In this study, we found that the expression of SREBP-1 in HCC tissues was significantly higher than those in matched tumor-adjacent tissues (p < 0.05). SREBP-1 was expressed at significantly higher levels in patients with large tumor size, high histological grade and advanced tumor-node-metastasis (TNM) stage (p < 0.05). The positive expression of SREBP-1 correlated with a worse 3-year overall and disease-free survival of HCC patients (p < 0.05). Additionally, SREBP-1 was an independent factor for predicting both 3-year overall and disease-free survival of HCC patients (p < 0.05). In vitro studies revealed that downregulation of SREBP-1 inhibited cell proliferation and induced apoptosis in both HepG2 and MHCC97L cells (p < 0.05). Furthermore, wound healing and transwell assays showed that SREBP-1 knockdown prominently inhibited cell migration and invasion in both HepG2 and MHCC97L cells (p < 0.05). These results suggest that SREBP-1 may serve as a prognostic marker in HCC and may promote tumor progression by promoting cell growth and metastasis.

The Hedgehog (Hh) pathway is an evolutionarily conserved signaling mechanism that controls many aspects of cell differentiation and the development of tissues and organs during embryogenesis. Early investigations have focused on the effects of Hh activity on the development of organs including skin, gut, the nervous system and bone. However, in addition to normal developmental processes, these investigations also found that Hh signaling is involved in aberrant proliferation and malignant transformation. Consequently, the role of Hh in cancer pathology, and its modulation by environmental factors is the subject of many investigations. Numerous environmental toxins, alcohol, and hepatitis viruses can cause hepatocellular carcinoma (HCC), which is the most common form of liver cancer. Significant hyperactivation of Hh signaling has been observed in liver injury and cirrhosis which often leads to the development of HCC lesions. Moreover, Hh activity plays an important role in the progression of HCC. Here, we review findings relevant to our understanding of the role of Hh signaling in HCC pathogenesis.

MircroRNA-130b (miR-130b) is proposed as a novel tumor-related miRNA and has been found to be significantly dysregulated in tumors. In this study, the expression level of miR-130b was found to be obviously higher in hepatocellular carcinoma (HCC) tissues than that in nontumor tissues. Further, miR-130b was expressed at significantly higher levels in aggressive and recurrent tumor tissues. Clinical analysis indicated that high-expression of miR-130b was prominently correlated with venous infiltration, high Edmondson-Steiner grading and advanced tumor-node-metastasis (TNM) tumor stage in HCC. Elevated miR-130b expression was observed in all HCC cell lines (HepG2, SMMC-7721, Huh7, Hep3B and MHCC97H) as compared with that in a nontransformed hepatic cell line (LO2). Furthermore, an inverse correlation between miR-130b and E-cadherin and a positive correlation between miR-130b and Vimentin were observed in HCC tissues. Down-regulation of miR-130b expression reduced invasion and migration in both Hep3B and MHCC97H cells. Peroxisome proliferator-activated receptor gamma (PPAR-γ) was inversely correlated with miR-130b expression in HCC tissues. In addition, down-regulation of miR-130b restored PPAR-γ expression and subsequently suppressed epithelial-mesenchymal transition (EMT) in HCC cells. We identified PPARγ as a direct target of miR-130b in HCC in vitro. Notably, PPAR-γ knockdown abolished down-regulation of miR-130b-inhibited EMT in MHCC97H cells. In conclusion, miR-130b may promote HCC cell migration and invasion by inhibiting PPAR-γ and subsequently inducing EMT.

P300/CBP-associated factor (PCAF), a histone acetyltransferase (HAT), has been found to regulate numerous cell signaling pathways controlling cell fate by acetylating both histone and non-histone proteins. We previously reported that PCAF upregulates cell apoptosis by inactivating Serine/Threonine Protein Kinase 1 (AKT1) signaling and consequently inhibits hepatocellular carcinoma (HCC) cell growth. Here, we show that PCAF can directly acetylate cytoplasmic GLI1 protein at lysine 518, preventing its nuclear translocation and promoter occupancy, and consequently suppressing Hedgehog (Hh) signaling in HCC. Further, our results show that GLI1 can increase Bcl-2 expression and downregulate BAX. Interestingly, forced expression of PCAF reduced Bcl-2 expression, upregulated BAX and repressed cell apoptosis. Further, we provide evidence that knockdown of GLI1 abrogates the inhibitory effect of PCAF on the growth of HCC in vitro. PCAF was also found to sensitize HCC cells to 5-fluorouracil (5-FU) treatment by regulating GLI1/Bcl-2/BAX axis-dependent apoptosis. In vivo experiments also confirmed the regulatory effect of PCAF on the GLI1/Bcl-2/BAX axis and its synergistic antitumor effects with 5-FU. Gene expression microarray studies showed that PCAF was downregulated in HCC tissues compared with adjacent liver tissues and that PCAF expression was significantly associated with longer overall survival and recurrence-free survival after surgery. Together, these results show that PCAF can induce cell apoptosis by modulating a GLI1/Bcl-2/BAX axis that in turn suppresses HCC progression, and suggest that 5-FU may exert a stronger anti-tumor effect in patients with PCAF expression in HCC tumors.