Immunochemical and Immunohistological Analyses of Tumor‐associated Antigens Defined by Murine Monoclonal Antibodies against Human Pancreatic Carcinoma Cells

Two murine monoclonal antibodies, SK‐930 (isotype IgG2a) and SK‐117 (isotype IgG1), were produced from spleen cells of mice immunized against human pancreatic carcinoma cell lines, MIA‐PaCa 2 and Panc‐1. With the use of the avidin‐biotin‐immunoperoxidase technique, the SK‐930 and SK‐117 antibodies detected an antigen found in 24 and 23 formalin‐fixed tissue sections, respectively, of tumors obtained from 30 different patients with pancreatic carcinoma. Reactivity was also frequently found with tumors of the gallbladder, bile duct, stomach, colon and esophagus, while a large panel of normal human tissues, including normal pancreatic tissues, displayed little reactivity. These observations suggest that SK‐930 and SK‐117 are of value in identifying tumor‐associated antigen (TAA) expressed in pancreatic carcinoma and other carcinomas of the digestive system. SK‐930 antibody immunoprecipitated a 134 kilodalton molecule from extracts of (125)I‐ or [(35)S]methionine‐ or [(3)H]glucosamine‐labeled tumor cells. The SK‐117‐defined antigen corresponds to 152/137 kilodalton molecules. Moreover, cytofluorometric analyses showed that cells treated with periodic acid exhibited greatly decreased reactivity to the two antibodies, but cells treated with neuraminidase, trypsin or pronase showed unchanged reactivity. The findings suggest that the epitopes of the novel TAA expressed on pancreatic carcinoma cells are carbohydrate moieties.