title: Fbxw7 is an independent prognostic marker and induces apoptosis and growth arrest by regulating YAP abundance in hepatocellular carcinoma.
abstract: BACKGROUND
  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.
  
  
  METHODS
  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.
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  These results indicate that Fbxw7 may serve as a prognostic marker and that YAP may be a potential target of Fbxw7 in HCC.
authors.forename: Kangsheng
authors.initials: K
authors.lastname: Tu
authors.forename: Wei
authors.initials: W
authors.lastname: Yang
authors.forename: Chao
authors.initials: C
authors.lastname: Li
authors.forename: Xin
authors.initials: X
authors.lastname: Zheng
authors.forename: Zhongtang
authors.initials: Z
authors.lastname: Lu
authors.forename: Cheng
authors.initials: C
authors.lastname: Guo
authors.forename: Yingmin
authors.initials: Y
authors.lastname: Yao
authors.affiliation: Department of Hepatobiliary Surgery, the First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, Shaanxi 710061, China. liuqingguang@vip.sina.com.
authors.forename: Qingguang
authors.initials: Q
authors.lastname: Liu
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics* / Q000378:metabolism; D000328:Adult; D000368:Aged; D000818:Animals; D017209:Apoptosis; D014408:Biomarkers, Tumor / Q000235:genetics* / Q000378:metabolism; D006528:Carcinoma, Hepatocellular / Q000175:diagnosis / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D059447:Cell Cycle Checkpoints / Q000235:genetics; D018797:Cell Cycle Proteins / Q000235:genetics* / Q000378:metabolism; D049109:Cell Proliferation; D044783:F-Box Proteins / Q000235:genetics* / Q000378:metabolism; D000073979:F-Box-WD Repeat-Containing Protein 7; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D008113:Liver Neoplasms / Q000175:diagnosis / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D008297:Male; D051379:Mice; D008819:Mice, Nude; D008875:Middle Aged; D060787:Neoplasm Grading; D009367:Neoplasm Staging; D009368:Neoplasm Transplantation; D010750:Phosphoproteins / Q000235:genetics* / Q000378:metabolism; D011379:Prognosis; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D059748:Proteolysis; D015398:Signal Transduction; D014157:Transcription Factors; D059016:Tumor Microenvironment; D044767:Ubiquitin-Protein Ligases / Q000235:genetics* / Q000378:metabolism; D000091102:YAP-Signaling Proteins
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D014408:Biomarkers, Tumor; D018797:Cell Cycle Proteins; D044783:F-Box Proteins; D000073979:F-Box-WD Repeat-Containing Protein 7; C513273:FBXW7 protein, human; D010750:Phosphoproteins; D014157:Transcription Factors; D000091102:YAP-Signaling Proteins; C088374:YAP1 protein, human; D044767:Ubiquitin-Protein Ligases; D046988:Proteasome Endopeptidase Complex