A tumor-associated antigen in the scirrhous gastric carcinoma cell line MK-01 defined by monoclonal antibody S202

A monoclonal antibody (MAb) S202, with an IgG₁ isotype, that reacted strongly with the scirrhous gastric carcinoma cell line MK-01 was established. MAb S202 reacted with the colonic cancer cell line, SW116, and the pancreatic cancer cell line, PK-1, when tested by indirect immunofluorescence. The S202 reactive antigen was expressed in the majority of acetone-fixed fresh frozen cancer tissues. Eighty to 100 per cent of the paraffin-embedded sections of stomach, colon and pancreatic adenocarcinoma were positive for the S202 antigen, with diffuse cytoplasmic staining, whereas esophageal and breast cancers demonstrated markedly less immunostaining. Supplemented serum-free medium collected from 7 day old tumor cell cultures were assayed for the presence of antibody-defined antigens. Antigens detected by MAb S202 were released by the cell lines SW1116 and PK-1. The binding of MAb S202 to the colonic adenocarcinoma sections was reduced after treatment with sodium periodate which suggests that respective antigenic determinants are of carbohydrate nature without sialic acid residues.