[A monoclonal antibody, KM10 reactive with human gastrointestinal cancer].

A monoclonal antibody, KM10 (IgG1) was produced by fusing spleen cells from a human gastric cancer cell-primed BALB/c mouse with the murine myeloma cell line X63-Ag8-653. The antibody reacted strongly with the plasma membrane of human gastro-intestinal carcinoma. Sections of both malignant and benign tissues were tested with immunoperoxidase. Ten of 10 (100%) large intestine cancers, 26 of 31 (84%) gastric cancers, 5 of 7 (71%) pancreatic cancers and 3 of 3 (100%) ampulla of Vater cancers reacted positively. Moderate or little reactivity was observed with normal human tissues and carcinomas of the liver, mammary, thyroid and adrenal glands. According to a study of the distribution of 125I-labeled KM10 in nude mice bearing human gastric cancer, KM10 selectively localized in tumor tissue rather than normal tissue. Whole-body autoradiography also supported such selective distribution. By enzyme treatment and Western blot analysis, the antigenic determinant of KM10 antigen was demonstrated to be protein with a MW of about 240,000.