The tumor-associated antigen, RCAS1, can be expressed in immune-mediated diseases as well as in carcinomas of biliary tract.
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.
Enjoji
Munechika
M
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
Nakashima
Manabu
M
Nishi
Hidehiro
H
Choi
Ilseung
I
Oimomi
Hideki
H
Sugimoto
Rie
R
Kotoh
Kazuhiro
K
Taguchi
Ken ichi
Ki
Nakamuta
Makoto
M
Nawata
Hajime
H
Watanabe
Takeshi
T
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
D000911:Antibodies, Monoclonal; D000951:Antigens, Neoplasm; C120762:EBAG9 protein, human