title: Strong expression of methylthioadenosine phosphorylase (MTAP) in human colon carcinoma cells is regulated by TCF1/[beta]-catenin.
abstract: Methylthioadenosine phosphorylase (MTAP) is known as a ubiquitously expressed house keeping gene important in biochemical salvage processes. The MTAP gene is localized on the human chromosomal region 9p21, a region often deleted in cancer. Recently, several groups including our own have shown that MTAP serves as a tumour suppressor gene. The aim of this study was to analyse the role of MTAP in colon carcinoma and normal colon epithelium and the regulation of gene expression. To examine MTAP RNA and protein expression, we screened six colon carcinoma cell lines and human primary colon epithelial cells by RT-PCR and immunoblotting. MTAP expression was confirmed in vivo by immunohistochemical staining of normal colon tissue compared to adenoma and colon carcinoma. Interestingly, we found strong MTAP mRNA and protein expression by colon carcinoma cell lines but no expression by colonic epithelial cells. To analyse the regulation of MTAP expression, promoter studies were performed and revealed control of MTAP expression by LEF/TCF/beta-catenin. Furthermore, we demonstrated a significant correlation between MTAP protein expression and tumour progression as the intensity of MTAP protein staining increased from normal tissue to carcinoma. In addition, the recently postulated association between MTAP activity and interferon (IFN) sensitivity was confirmed in colon epithelial cells showing only little response to IFN-gamma, in contrast to the carcinoma cell lines. In summary, these data indicate for the first time that MTAP is not expressed in normal human colonic epithelium but is strongly upregulated in colon carcinoma. This finding may be of clinical significance concerning the homeostasis of normal colon epithelium and potential treatment of colon carcinoma.
authors.affiliation: Institute of Pathology, University of Regensburg Medical School, Regensburg, Germany.
authors.forename: Frauke
authors.initials: F
authors.lastname: Bataille
authors.forename: Gerhard
authors.initials: G
authors.lastname: Rogler
authors.forename: Katharina
authors.initials: K
authors.lastname: Modes
authors.forename: Ina
authors.initials: I
authors.lastname: Poser
authors.forename: Marion
authors.initials: M
authors.lastname: Schuierer
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Dietmaier
authors.forename: Petra
authors.initials: P
authors.lastname: Ruemmele
authors.forename: Marcus
authors.initials: M
authors.lastname: Mühlbauer
authors.forename: Susanne
authors.initials: S
authors.lastname: Wallner
authors.forename: Claus
authors.initials: C
authors.lastname: Hellerbrand
authors.forename: Anja-Katrin
authors.initials: AK
authors.lastname: Bosserhoff
mesh_terms: D000230:Adenocarcinoma / Q000201:enzymology* / Q000473:pathology; D001943:Breast Neoplasms / Q000201:enzymology / Q000473:pathology; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D003110:Colonic Neoplasms / Q000201:enzymology* / Q000473:pathology; D003598:Cytoskeletal Proteins / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism*; D019084:Fluorescent Antibody Technique, Indirect; D015972:Gene Expression Regulation, Neoplastic; D051537:Hepatocyte Nuclear Factor 1; D051538:Hepatocyte Nuclear Factor 1-alpha; D006801:Humans; D007413:Intestinal Mucosa / Q000201:enzymology; D008545:Melanoma / Q000201:enzymology / Q000473:pathology; D009687:Nuclear Proteins / Q000378:metabolism*; D011683:Purine-Nucleoside Phosphorylase / Q000235:genetics* / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012878:Skin Neoplasms / Q000201:enzymology / Q000473:pathology; D015534:Trans-Activators / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism*; D015854:Up-Regulation; D051176:beta Catenin
chemical_list: C495270:CTNNB1 protein, human; D003598:Cytoskeletal Proteins; D004268:DNA-Binding Proteins; C496487:HNF1A protein, human; D051538:Hepatocyte Nuclear Factor 1-alpha; D009687:Nuclear Proteins; D012333:RNA, Messenger; D015534:Trans-Activators; D014157:Transcription Factors; D051176:beta Catenin; D051537:Hepatocyte Nuclear Factor 1; D011683:Purine-Nucleoside Phosphorylase; C021784:5'-methylthioadenosine phosphorylase