A monoclonal antibody-defined antigen associated with gastrointestinal cancer is a ganglioside containing sialylated lacto-N-fucopentaose II.

Two monoclonal antibodies produced by hybridomas obtained from a mouse immunized with a colorectal carcinoma cell line bind specifically to human gastrointestinal cancer cells. The antigen of this antibody in the carcinoma cell line, a monosialoganglioside, has been isolated. Its carbohydrate structure is probably (formula: see text). This oligosaccharide is a sialyl derivative of lacto-N-fucopentaose II, a hapten of the human Lea blood group antigen. About 30 micrograms of ganglioside is obtained from 1 g of cells, wet weight. The ganglioside was detected by autoradiography in lipid extracts of some carcinomas and of meconium, but not in lipid extracts of normal adult tissues. Antigen was detected by solid phase radioimmunoassay in lipid extracts from 12 out of 21 adenocarcinomas of the colon, from 4 out of 5 gastric adenocarcinomas, and from 4 out of 7 pancreatic carcinomas. Antigen was not detected in lipid extracts from 5 esophageal carcinomas or from normal colon and gastric mucosa, pancreas, kidney, liver, and bone marrow.