SIALOGLYCOPROTEINS OF HUMAN MAMMARY CELLS - PARTIAL CHARACTERIZATION OF SIALOGLYCOPEPTIDES

Sialoglycopeptides were isolated and fractionated from cultured human mammary cell lines (one control line, HBL-100, and two cancer lines, MDA-MB-231 and MCF-7) into three groups: neutral, less anionic, and more anionic. Cells were cultured with [3H]glucosamine, [3H]glucosamine and [14C]galactose, or [14C]glucosamine and [3H]galactose, following which spent-medium and cell-associated components were analyzed. Exhaustive Pronase digestion and removal of glycosaminoglycans with cetylpyridinium chloride were followed by diethylaminoethylcellulose and wheat germ agglutinin (WGA)-Sepharose chromatography. The cancer lines produced 3-5 times greater amounts of the more anionic glyco-peptides compared to the control line. Within this fraction, WGA-bound material was predominant in the cancer lines. Alkaline borohydride treatment of the WGA-binding fraction from both cancer lines gave rise to a major elimination product not observed with comparable material from HBL-100 cells. Analysis of the asialosaccharide chain gave the structure [formula omitted] The structural requirements for the binding of the glycopeptides to WGA were analyzed. The WGA-binding capacity is dependent on both molecular size and sialic acid content. In addition, the saccharide moiety of the WGA-binding glycopeptides is purely O-glycosidically linked whereas that from the WGA-non-binding material is mainly N-glycosidic. The WGA-binding glycopeptides contain clustered oligosaccharide chains having the sequence [formula omitted]. © 1979, American Chemical Society. All rights reserved.