title: Integrative analysis of aberrant Wnt signaling in hepatitis B virus-related hepatocellular carcinoma.
abstract: OBJECTIVE
  To comprehensively understand the underlying molecular events accounting for aberrant Wnt signaling activation in hepatocellular carcinoma (HCC).
  
  
  METHODS
  This study was retrospective. The HCC tissue specimens used in this research were obtained from patients who underwent liver surgery. The Catalogue of Somatic Mutations in Cancer (COSMIC) database was searched for the mutation statuses of CTNNB1, TP53, and protein degradation regulator genes of CTNNB1. Dual-luciferase reporter assay was performed with TOP/FOP reporters to detect whether TP53 gain-of-function (GOF) mutations could enhance the transcriptional activity of Wnt signaling. Methylation sensitive restriction enzyme-quantitative PCR was used to explore the methylation status of CpG islands located in the promoters of APC, SFRP1, and SFRP5 in HCCs with different risk factors. Finally, nested-reverse transcription PCR was performed to examine the integration of HBx in front of LINE1 element and the existence of HBx-LINE1 chimeric transcript in Hepatitis B virus-related HCC. All results in this article were analyzed with the software SPSS version 19.0 for Windows, and different groups were compared by χ(2) test as appropriate.
  
  
  RESULTS
  Based on the data from COSMIC database, compared with other solid tumors, mutation frequency of CTNNB1 was significantly higher in HCC (P < 0.01). The rate of CTNNB1 mutation was significantly less frequent in Hepatitis B virus-related HCC than in other etiologies (P < 0.01). Dual-luciferase reporter system and TOP/FOP reporter assays confirmed that TP53 GOF mutants were able to enhance the transcriptional ability of Wnt signaling. An exclusive relationship between the status of TP53 and CTNNB1 mutations was observed. However, according to the COSMIC database, TP53 GOF mutation is rare in HCC, which indicates that TP53 GOF mutation is not a reason for the aberrant activation of Wnt signaling in HCC. APC and AXIN1 were mutated in HCC. By using methylation sensitive restriction enzyme-quantitative PCR, hypermethylation of APC was detected in HCC with different risk factors, whereas SFRP1 and SFRP5 were not hypermethylated in any of the HCC etiologies, which indicates that the mutation of APC and AXIN1, together with the methylation of APC could take part in the overactivation of Wnt signaling. Nested-reverse transcription PCR failed to detect the integration of HBx before the LINE1 element, or the existence of an HBx-LINE1 chimeric transcript, suggesting that integration could not play a role in the aberrant activation of Wnt signaling in HCC.
  
  
  CONCLUSIONS
  In HCC, genetic/epigenetic aberration of CTNNB1 and its protein degradation regulators are the major cause of Wnt signaling overactivation.
authors.affiliation: Shan-Long Ding, Zi-Wei Yang, Jie Wang, Xiao-Lei Zhang, Xiang-Mei Chen, Feng-Min Lu, Department of Microbiology and Infectious Disease Center, School of Basic Medical Sciences, Peking University Health Science Center, Beijing 100191, China.
authors.forename: Shan-Long
authors.initials: SL
authors.lastname: Ding
authors.affiliation: Shan-Long Ding, Zi-Wei Yang, Jie Wang, Xiao-Lei Zhang, Xiang-Mei Chen, Feng-Min Lu, Department of Microbiology and Infectious Disease Center, School of Basic Medical Sciences, Peking University Health Science Center, Beijing 100191, China.
authors.forename: Zi-Wei
authors.initials: ZW
authors.lastname: Yang
authors.affiliation: Shan-Long Ding, Zi-Wei Yang, Jie Wang, Xiao-Lei Zhang, Xiang-Mei Chen, Feng-Min Lu, Department of Microbiology and Infectious Disease Center, School of Basic Medical Sciences, Peking University Health Science Center, Beijing 100191, China.
authors.forename: Jie
authors.initials: J
authors.lastname: Wang
authors.affiliation: Shan-Long Ding, Zi-Wei Yang, Jie Wang, Xiao-Lei Zhang, Xiang-Mei Chen, Feng-Min Lu, Department of Microbiology and Infectious Disease Center, School of Basic Medical Sciences, Peking University Health Science Center, Beijing 100191, China.
authors.forename: Xiao-Lei
authors.initials: XL
authors.lastname: Zhang
authors.affiliation: Shan-Long Ding, Zi-Wei Yang, Jie Wang, Xiao-Lei Zhang, Xiang-Mei Chen, Feng-Min Lu, Department of Microbiology and Infectious Disease Center, School of Basic Medical Sciences, Peking University Health Science Center, Beijing 100191, China.
authors.forename: Xiang-Mei
authors.initials: XM
authors.lastname: Chen
authors.affiliation: Shan-Long Ding, Zi-Wei Yang, Jie Wang, Xiao-Lei Zhang, Xiang-Mei Chen, Feng-Min Lu, Department of Microbiology and Infectious Disease Center, School of Basic Medical Sciences, Peking University Health Science Center, Beijing 100191, China.
authors.forename: Feng-Min
authors.initials: FM
authors.lastname: Lu
mesh_terms: D000818:Animals; D001665:Binding Sites; D014408:Biomarkers, Tumor / Q000235:genetics / Q000378:metabolism*; D006528:Carcinoma, Hepatocellular / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D045744:Cell Line, Tumor; D002472:Cell Transformation, Viral; D016009:Chi-Square Distribution; D018899:CpG Islands; D019175:DNA Methylation; D030541:Databases, Genetic; D044127:Epigenesis, Genetic; D015972:Gene Expression Regulation, Neoplastic; D020022:Genetic Predisposition to Disease; D057809:HEK293 Cells; D019694:Hepatitis B, Chronic / Q000150:complications* / Q000175:diagnosis; D006801:Humans; D008113:Liver Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology / Q000821:virology; D009154:Mutation; D010641:Phenotype; D011401:Promoter Regions, Genetic; D059748:Proteolysis; D012189:Retrospective Studies; D049490:Systems Biology; D018511:Systems Integration; D015533:Transcriptional Activation; D014162:Transfection; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism*; D060449:Wnt Signaling Pathway / Q000235:genetics; D051176:beta Catenin / Q000235:genetics / Q000378:metabolism*
chemical_list: D014408:Biomarkers, Tumor; C495270:CTNNB1 protein, human; C495901:TP53 protein, human; D016159:Tumor Suppressor Protein p53; D051176:beta Catenin
keywords: CTNNB1; Hepatitis B virus; Hepatocellular carcinoma; TP53; Wnt signaling; β-catenin