title: The tumor-associated antigen, RCAS1, can be expressed in immune-mediated diseases as well as in carcinomas of biliary tract.
abstract: OBJECTIVE
  RCAS1, which is recognized by the specific antibody 22-1-1, was first identified as a tumor-associated antigen in gynecological carcinomas. RCAS1 is the ligand of a putative receptor present on lymphocytes, the expression of which is enhanced by lymphocyte activation. RCAS1 inhibits the growth of receptor-bearing cells and induces apoptotic death. Here we examined RCAS1 expression in biliary diseases.
  
  
  METHODS
  RCAS1 expression was immunohistochemically examined on tissue samples. Apoptotic death was analyzed by DNA fragmentation detection method. RCAS1 production by cell lines was investigated by flow cytometry, enzyme-linked immunosorbent assay, and reverse transcription-polymerase chain reaction.
  
  
  RESULTS
  All cholangiocarcinoma cell lines examined clearly expressed RCAS1 at both the protein and RNA level. Immunohistochemically, RCAS1 was expressed in a high percentage of biliary adenocarcinomas (85.9% of intrahepatic cholangiocarcinomas, 96.4% of extrahepatic cholangiocarcinomas and gallbladder carcinomas). Apoptotic tumor-infiltrating lymphocytes could be found in these specimens. RCAS1 expression was frequently detected also in biliary epithelial cells in cases of immune-mediated cholangitis (74.2% in primary biliary cirrhosis, 66.6% in graft-versus-host disease), although the staining pattern for RCAS1 was different compared with cancer cells.
  
  
  CONCLUSIONS
  RCAS1 is highly expressed not only in cancer cells but also in non-tumor bile duct cells subjected to immune attack.
authors.affiliation: Department of Medicine and Bioregulatory Science, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan. enjoji@intmed3.med.kyushu-u.ac.jp
authors.forename: Munechika
authors.initials: M
authors.lastname: Enjoji
authors.forename: Manabu
authors.initials: M
authors.lastname: Nakashima
authors.forename: Hidehiro
authors.initials: H
authors.lastname: Nishi
authors.forename: Ilseung
authors.initials: I
authors.lastname: Choi
authors.forename: Hideki
authors.initials: H
authors.lastname: Oimomi
authors.forename: Rie
authors.initials: R
authors.lastname: Sugimoto
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Kotoh
authors.forename: Ken ichi
authors.initials: Ki
authors.lastname: Taguchi
authors.forename: Makoto
authors.initials: M
authors.lastname: Nakamuta
authors.forename: Hajime
authors.initials: H
authors.lastname: Nawata
authors.forename: Takeshi
authors.initials: T
authors.lastname: Watanabe
mesh_terms: D000230:Adenocarcinoma / Q000473:pathology / Q000503:physiopathology; D000818:Animals; D000911:Antibodies, Monoclonal; D000951:Antigens, Neoplasm / Q000032:analysis / Q000235:genetics* / Q000276:immunology; D001652:Bile Ducts / Q000737:chemistry / Q000473:pathology / Q000502:physiology; D001661:Biliary Tract Neoplasms / Q000473:pathology / Q000503:physiopathology*; D001706:Biopsy; D018281:Cholangiocarcinoma / Q000473:pathology / Q000503:physiopathology*; D006086:Graft vs Host Disease / Q000473:pathology / Q000503:physiopathology*; D006801:Humans; D008105:Liver Cirrhosis, Biliary / Q000473:pathology / Q000503:physiopathology*; D051379:Mice; D014407:Tumor Cells, Cultured
chemical_list: D000911:Antibodies, Monoclonal; D000951:Antigens, Neoplasm; C120762:EBAG9 protein, human