title: Transmembrane carbonic anhydrase, MN/CA IX, is a potential biomarker for biliary tumours.
abstract: OBJECTIVE
  Carbonic anhydrase isoenzyme IX (MN/CA IX) is a transmembrane protein with a suggested function in maintaining the acid-base balance and intercellular communication. Previous studies have demonstrated that MN/CA IX is expressed in the basolateral plasma membrane of normal biliary epithelial cells, but not in hepatocytes. This study was designed to examine the expression of MN/CA IX in hepatobiliary neoplasms and to elucidate its value as a marker for biliary differentiation.
  
  
  METHODS
  Fifty-seven hepatobiliary lesions were immunostained for MN/CA IX using biotin-streptavidin complex method. Twenty samples containing normal biliary epithelium and five containing normal liver tissue were used as controls.
  
  
  RESULTS
  In the biliary epithelial tumours, immunostaining for MN/CA IX was mainly localized at the basolateral surface of the epithelial cells, like in normal mucosa. All non-invasive dysplastic lesions and 57% of invasive lesions of gall-bladder expressed MN/CA IX. In liver, 78% of cholangiocellular malignant lesions showed a positive reaction for MN/CA IX, whereas only 33% of hepatocellular carcinomas showed a weak immunoreaction.
  
  
  CONCLUSIONS
  Our results suggest that abnormal expression of MN/CA IX may be linked to malignant transformation of hepatobiliary cells. In addition, it seems to be a promising marker for biliary differentiation in hepatobiliary neoplasms.
authors.affiliation: Department of Surgery, University of Oulu, Kajaanintie 52A, FIN-90220 Oulu, Finland. juha.saarnio@oulu.fi
authors.forename: J
authors.initials: J
authors.lastname: Saarnio
authors.forename: S
authors.initials: S
authors.lastname: Parkkila
authors.forename: A K
authors.initials: AK
authors.lastname: Parkkila
authors.forename: S
authors.initials: S
authors.lastname: Pastoreková
authors.forename: K
authors.initials: K
authors.lastname: Haukipuro
authors.forename: J
authors.initials: J
authors.lastname: Pastorek
authors.forename: T
authors.initials: T
authors.lastname: Juvonen
authors.forename: T J
authors.initials: TJ
authors.lastname: Karttunen
mesh_terms: D000951:Antigens, Neoplasm; D001661:Biliary Tract Neoplasms / Q000201:enzymology / Q000473:pathology*; D014408:Biomarkers, Tumor / Q000032:analysis; D000071231:Carbonic Anhydrase IX; D002256:Carbonic Anhydrases / Q000032:analysis*; D006528:Carcinoma, Hepatocellular / Q000201:enzymology / Q000473:pathology; D004847:Epithelial Cells / Q000166:cytology / Q000201:enzymology / Q000473:pathology; D006801:Humans; D007150:Immunohistochemistry; D007527:Isoenzymes / Q000032:analysis; D019394:Ki-67 Antigen / Q000032:analysis; D008113:Liver Neoplasms / Q000201:enzymology / Q000473:pathology; D008565:Membrane Proteins / Q000032:analysis; D009363:Neoplasm Proteins / Q000032:analysis*; D012016:Reference Values
chemical_list: D000951:Antigens, Neoplasm; D014408:Biomarkers, Tumor; D007527:Isoenzymes; D019394:Ki-67 Antigen; D008565:Membrane Proteins; D009363:Neoplasm Proteins; C089226:CA9 protein, human; D000071231:Carbonic Anhydrase IX; D002256:Carbonic Anhydrases