Human homolog of NOTUM, overexpressed in hepatocellular carcinoma, is regulated transcriptionally by beta-catenin/TCF.
The Drosophila Notum gene, which is regulated by the Wingless pathway, encodes a secreted hydrolase that modifies heparan sulfate proteoglycans. In comparative analysis of the gene expression profiles in primary human hepatocellular carcinomas (HCC) and normal organs, we observed that the human ortholog of Drosophila Notum was overexpressed markedly in a subset of HCC, but expressed rarely in adult normal tissues. Immunoblotting confirmed the overexpression of NOTUM protein in 12 of 40 primary HCC cases (30%). High levels of NOTUM protein were significantly associated with intracellular (nuclear or cytoplasmic) accumulation of beta-catenin protein: all 10 HCC with high intracellular beta-catenin also had high NOTUM expression, whereas only 2 of 30 cases (6.7%) without intracellular beta-catenin had high NOTUM expression (P < 0.00001). NOTUM expression in HepG2 cells was downregulated significantly by induction of a dominant-negative mutant of TCF4, a beta-catenin partner. In vivo binding of the beta-catenin/TCF complex to the NOTUM promoter was demonstrated by chromatin immunoprecipitation in HepG2 and SW480 cells, where canonical Wnt signaling is activated constitutively. These findings provide evidence that NOTUM is a novel target of beta-catenin/TCF4 and is upregulated in Wnt/beta-catenin signaling-activated HCC.
Torisu
Yuichi
Y
Genome Science Division, Research Center for Advanced Science and Technology, The University of Tokyo, 4-6-1, Komaba, Meguro-ku, Tokyo 153-8904, Japan.
Watanabe
Akira
A
Nonaka
Aya
A
Midorikawa
Yutaka
Y
Makuuchi
Masatoshi
M
Shimamura
Takahiro
T
Sugimura
Haruhiko
H
Niida
Atsushi
A
Akiyama
Tetsu
T
Iwanari
Hiroko
H
Kodama
Tatsuhiko
T
Zeniya
Mikio
M
Aburatani
Hiroyuki
H
D000328:Adult; D000368:Aged; D000818:Animals; D000911:Antibodies, Monoclonal; D006528:Carcinoma, Hepatocellular / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D047369:Chromatin Immunoprecipitation; D029721:Drosophila Proteins / Q000235:genetics* / Q000276:immunology / Q000378:metabolism; D005260:Female; D020869:Gene Expression Profiling; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007114:Immunization; D015151:Immunoblotting; D008113:Liver Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D008297:Male; D051379:Mice; D008875:Middle Aged; D016297:Mutagenesis, Site-Directed; D020411:Oligonucleotide Array Sequence Analysis; D011401:Promoter Regions, Genetic; D011817:Rabbits; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D015398:Signal Transduction; D051820:TCF Transcription Factors / Q000235:genetics / Q000378:metabolism; D058118:Transcription Factor 7-Like 2 Protein; D014158:Transcription, Genetic; D014407:Tumor Cells, Cultured; D051176:beta Catenin / Q000378:metabolism*
D000911:Antibodies, Monoclonal; C495270:CTNNB1 protein, human; D029721:Drosophila Proteins; C456459:Notum protein, Drosophila; D011993:Recombinant Fusion Proteins; D051820:TCF Transcription Factors; C544894:TCF7L2 protein, human; C544895:Tcf7l2 protein, mouse; D058118:Transcription Factor 7-Like 2 Protein; D051176:beta Catenin