Binding of transferrin to membrane-associated proteoglycans in breast-cancer cells.

Cell surface associated proteoglycans were isolated from MCF-7 breast tumor cells by mild trypsin digestion, extraction by guanidine-hydrochloride and purification by ion-exchange chromatography. Immunological studies showed that transferrin can bind to membrane associated proteoglycans (MAPG). However, these MAPG are not recognized by anti-transferrin receptor antibodies either in an intact, or in a form stripped of glycosaminoglycan chains. Considering the possible involvement of secreted transferrin in proliferation or differentiation of breast tumor cells, we suggest that transferrin binding to MAPG may be related to a specific function of transferrin.