Wnt signaling in hepatocellular carcinoma: analysis of mutation and expression of beta-catenin, T-cell factor-4 and glycogen synthase kinase 3-beta genes.
OBJECTIVE
Hepatocellular carcinoma (HCC) is a common killer cancer in the world. Recently, abnormal activation of the Wnt pathway has been found to be involved in the carcinogenesis of several human cancers including HCC. The goal of the present study was to investigate the mechanism of inappropriate activation of the Wnt pathway in hepatocarcinogenesis.


METHODS
We analyzed the alterations of three key components of the Wnt pathway: beta-catenin, glycogen synthase kinase (GSK)-3beta and T-cell factor (Tcf)-4 in 34 HCC and paracancerous normal liver by immunohistochemistry, polymerase chain reaction (PCR)-single-strand conformation polymorphism (SSCP), direct sequencing, and quantitative real-time reverse transcription (RT)-PCR.


RESULTS
We found that 61.8% (21/34) of all HCC examined showed an abnormal beta-catenin protein accumulation in the cytoplasm or nuclei. The RT-PCR-SSCP and direct sequencing showed that beta-catenin exon 3 mutations existed in 44.1% (15/34) of the HCC. No mutations of GSK-3beta or Tcf-4 were detected in HCC. Moreover, messenger RNA of beta-catenin and Tcf-4, but not GSK-3beta, was found to be overexpressed in HCC. On analyzing the relationship between alterations of beta-catenin or Tcf-4 and C-myc or Cyclin D1 expression, we found that mutations of beta-catenin, as well as overexpression of beta-catenin or the Tcf-4 gene were independently correlated with C-myc gene overexpression in HCC.


CONCLUSIONS
Our present findings strongly suggest that mutations of beta-catenin, as well as overexpression of beta-catenin and the Tcf-4 gene, independently activate the Wnt pathway in HCC, with the target gene most likely to be C-myc.
Cui
Jian
J
Liver Cancer Institute, Medical Center of Fudan University, Shanghai, China. cuij@msu.edu
Zhou
Xinda
X
Liu
Yinkun
Y
Tang
Zhaoyou
Z
Romeih
Mahmoud
M
D014408:Biomarkers, Tumor / Q000235:genetics / Q000378:metabolism; D006528:Carcinoma, Hepatocellular / Q000235:genetics* / Q000378:metabolism; D002681:China; D019938:Cyclin D1 / Q000096:biosynthesis / Q000235:genetics; D003598:Cytoskeletal Proteins / Q000096:biosynthesis / Q000235:genetics; D004252:DNA Mutational Analysis; D015536:Down-Regulation / Q000502:physiology; D004587:Electrophoresis, Agar Gel; D005091:Exons / Q000235:genetics; D016259:Genes, myc / Q000235:genetics; D038362:Glycogen Synthase Kinase 3 / Q000096:biosynthesis / Q000235:genetics; D000071679:Glycogen Synthase Kinase 3 beta; D006801:Humans; D007150:Immunohistochemistry; D008113:Liver Neoplasms / Q000235:genetics* / Q000378:metabolism; D009154:Mutation / Q000235:genetics; D018807:Polymorphism, Single-Stranded Conformational; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013223:Statistics as Topic; D051820:TCF Transcription Factors; D015534:Trans-Activators / Q000096:biosynthesis / Q000235:genetics; D058118:Transcription Factor 7-Like 2 Protein; D014157:Transcription Factors / Q000096:biosynthesis / Q000235:genetics; D051176:beta Catenin
D014408:Biomarkers, Tumor; C495270:CTNNB1 protein, human; D003598:Cytoskeletal Proteins; D012333:RNA, Messenger; D051820:TCF Transcription Factors; C544894:TCF7L2 protein, human; D015534:Trans-Activators; D058118:Transcription Factor 7-Like 2 Protein; D014157:Transcription Factors; D051176:beta Catenin; D019938:Cyclin D1; C000605506:GSK3B protein, human; D000071679:Glycogen Synthase Kinase 3 beta; D038362:Glycogen Synthase Kinase 3