Expression and diagnostic evaluation of the human tumor-associated antigen RCAS1 in pancreatic cancer.

Introduction: Receptor-binding cancer antigen expressed on SiSo cells (RCAS1) is one of the membrane molecules expressed on human cancer cells and is presumed to play a protective role for tumor cells against immune surveillance by inhibition of clonal expansion and induction of cell death in immunocytes.

Aims: To address whether RCAS1 is expressed in pancreatic cancer and whether serologic diagnostic evaluation is useful compared with that of carbohydrate antigen 19-9 (CA19-9) and soluble Fas ligand.

Methodology: Immunohistochemical expression of RCAS1 was examined by staining with a 22-1-1 monoclonal antibody, and serum RCAS1 concentrations were determined by an enzyme-linked immunosorbent assay in 20 cases of ductal adenocarcinoma of the pancreas and other pancreatic diseases.

The tumor-associated antigen, RCAS1, can be expressed in immune-mediated diseases as well as in carcinomas of biliary tract.

Background/aims: 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.