Blood group H active glycolipid from rat ascites hepatoma AH 7974F

Carbohydrate structure in tumor immunity

Researchers have endeavored to define surface alterations associated with neoplasia for at least 25 years. In comparisons of normal tissues with animal and human tumors, cultured cells before and after transformation with oncogenic agents, tumorigenic and nontumorigenic transformed cells, metastatic and nonmetastatic tumor cells, high- and low-metastatic variants, and tumor cells before and after induction of differentiation to a less malignant phenotype, a consistent finding has been some form of alteration in surface carbohydrate structures. These changes in glycolipids, glycoproteins and glycosaminoglycans are reviewed, and their structures are illustrated. Both nucleotide sugar biosynthesis and glycosyltransferase changes have been associated with these alterations. In some cases, alterations in transformed cells were related to growth, rather than transformation. In others, the altered glycoconjugates are truly tumor-associated. There is evidence that cell surface glycoconjugates may function in growth control. Altered carbohydrate structures could also serve as receptors for growth promoting factors and be directly responsible for altered growth control. Recent studies with monoclonal antibodies indicate that the vast majority of antibodies recognizing tumor-associated antigens are detecting altered carbohydrate structures. Mechanisms by which the immune system can recognize these carbohydrate structures are considered, and immune recognition of tumor-associated carbohydrate structural alterations is explored. A number of these hypotheses relating to alterations in glycosylation, growth control, and tumor immunity deserve further investigation.

Synthesis of the trisaccharide moiety of gangliotriosylceramide (asialo GM2)

The synthesis of the trisaccharide methyl glycoside beta-D-GalNAc-(1----4)-beta-D-Gal-(1----4)-beta-D-Glc-OMe, which corresponds to the carbohydrate portion of gangliotriosylceramide (asialo GM2), was accomplished by the reaction of 4-O-acetyl-3,6-di-O-benzoyl-2-deoxy-2-phthalimido-D-galactopyranosyl bromide (18) with a benzylated derivative of methyl 4-O-beta-D-galactopyranosyl-beta-D-glucopyranoside. Comparative studies with a 6'-benzyl ether and a 6'-benzoate revealed that the substituent at O-6' is crucial to the outcome of glycosylations at O-4', the ether derivative being much the more reactive. tert-Butyl 4-O-acetyl-3,6-di-O-benzoyl-2-deoxy-2-phthalimido-D-galactopyranoside, which was readily converted into the corresponding bromide 18, was obtained from the gluco derivative via a single-step, crown ether-assisted epimerization.

Glycolipids of rat small intestine. Characterization of a novel blood group H-active triglycosylceramide

A novel blood group H-active triglycosylceramide has been isolated from rat small intestine. It was present exclusively in the epithelial cells. The structure was established by mass spectrometry, NMR spectroscopy and degradative methods to the Fucp alpha 1 leads to 2Galp beta 1 leads to 4Glcp beta 1 leads to 1Cer. The lipophilic part was made up of mainly trihydroxy base (phytosphingosine) and 16 : 0--24 : 0 fatty acids.