Structures of O-linked oligosaccharides present in the proteoglycans secreted by human mammary epithelial cells

The structures of O-glycosidically linked oligosaccharides present in the heparan sulfate and chondroitin sulfate proteoglycans isolated from the culture medium of a normal (HBL-100) and a malignant (MDA-MB-231) human mammary epithelial cell line have been determined. Both proteoglycan types from the two cell lines contain a series of O-linked oligosaccharides ranging in size from di- to hexasaccharide. Cells were grown in the presence of either [3H]glucosamine or [3H]galactose and Na2 35SO4, and the proteoglycans were isolated as described (Gowda, D. C., Bhavanandan, V. P., and Davidson, E. A. (1986) J. Biol. Chem. 261, 4926-4934). The O-linked oligosaccharides were released from the proteoglycans by alkaline borohydride treatment and purified by a combination of gel filtration and high voltage paper electrophoresis. The structures of two neutral and seven acidic oligosaccharides were established based on sugar composition, the results of periodate oxidation, sequential exoglycosidase treatment, and methylation analysis. Periodate oxidation, taking advantage of tritium label at specific positions of constituent sugars, proved to be a valuable tool in establishing the structure of isomeric components in the mixture. The structures of the oligosaccharides were assigned as follows: (Formula: see text) The oligosaccharide containing both sialic acid and ester sulfate is novel and has not been reported previously.