FC-2.15, a monoclonal antibody active against human breast cancer, specifically recognizes Lewis(x) hapten

FC-2.15 is a murine IgM monoclonal antibody that recognizes breast and colon human carcinomas, chronic myeloid leukemias, Steinberg cells of Hodgkin's lymphoma and some normal cells, such as peripheral polymorphonuclear granulocytes. It has been previously demonstrated that FC- 2.15 recognizes the carbohydrate moiety of different glycoproteins. FC-2.15 is able to mediate the in vitro lysis of Ag-2.15⁺ cells by human complement. In a phase I clinical trial, FC-2.15 induced antitumor responses and reversible neutropenia was its main toxicity. In this work, analysis of epitope specificity has demonstrated that FC-2.15 specifically recognizes terminally exposed Lewis(x) trisaccharide but not sialyl-Lewis(x), Lewis(a), trifucosylated Lewis(y), blood-group antigens A and B, globo H and gangliosides. In polymorphonuclear granulocytes (PMN), myeloid leukemic cells and colon carcinoma T84 cells, Lewis(x) was found to be almost exclusively N- linked to the protein core, whereas in breast carcinoma MCF-7 cells, Lewis(x) appeared to be mostly O-linked. Treatment with neuraminidase increased detection by FC-2.15 in normal PMN, myeloid leukemia cells and T84 cells but not in MCF-7 cells.