title: Internalization and re-expression of antigens of human melanoma cells following exposure to monoclonal antibody.
abstract: Modulation of the surface membrane of human Sk-Mel-28 melanoma cells by monoclonal antibody (MoAb) 96.5 recognizing p97 determinants was examined using direct radioimmunoassay and indirect fluorescent antibody-staining techniques. It was determined that the majority of 111In-labeled antibody that remained associated with cells after a 24-hr incubation at 37 degrees C had been internalized because MoAb 96.5 was no longer visible on the cell surface. A second treatment of these cells with the same antibody 24 hr later not only increased the cell-associated radioactivity, reflecting an increase of total antibody bound, but also rendered these cells membrane immunofluorescent again, indicating the re-expression of surface antigens. Autoradiographs of the electrophoretically analyzed membrane components of Sk-Mel-28 cells further demonstrated the appearance of newly synthesized 97-kDa proteins that were immunoprecipitable with MoAb 96.5. Taken together, the present findings suggest that p97 antigens undergo endocytosis in Sk-Mel-28 cells following exposure to MoAb 96.5. However, the same antigens were regenerated and expressed on the cell surface within a period of 24 hr. The re-expression of tumor cell surface antigen following initial internalization of the MoAb-antigen complex may have implications for diagnosis and therapy.
mesh_terms: D000911:Antibodies, Monoclonal; D000912:Antibodies, Neoplasm; D000937:Antigen-Antibody Reactions / Q000528:radiation effects; D000951:Antigens, Neoplasm; D000954:Antigens, Surface; D002455:Cell Division; D002462:Cell Membrane / Q000276:immunology; D002478:Cells, Cultured; D004705:Endocytosis; D006801:Humans; D008545:Melanoma / Q000276:immunology*
chemical_list: D000911:Antibodies, Monoclonal; D000912:Antibodies, Neoplasm; D000951:Antigens, Neoplasm; D000954:Antigens, Surface