NEOGLYCOPROTEINS WITH THE SYNTHETIC COMPLEX BIANTENNARY NONASACCHARIDE OR ITS ALPHA-2,3 ALPHA-2,6-SIALYLATED DERIVATIVES - THEIR PREPARATION, ASSESSMENT OF THEIR LIGAND PROPERTIES FOR PURIFIED LECTINS, FOR TUMOR-CELLS IN-VITRO, AND IN TISSUE-SECTIONS, AND THEIR BIODISTRIBUTION IN TUMOR-BEARING MICE/

Neoglycoproteins were prepared with chemoenzymatically synthesized com plex biantennary N-glycan derivatives the nonreducing ends of which be ar typical sequences found in glycoproteins. A chemically obtained bia ntennary heptasaccharide-azide was reduced and acylated with a 6-amino hexanoyl spacer. Elongation of the deprotected heptasaccharide using g lycosyltransferases yielded a biantennary nonasaccharide with terminal galactose residues and two undecasaccharides terminating with alpha 2 ,6- or alpha 2,3-linked sialic acid. The free amino group of the space r of these oligosaccharides was converted into an isothiocyanate. Its subsequent coupling to bovine serum albumin gave neoglycoproteins with a yield of 2.4-3.6 glycan chains per carrier molecule. This versatile synthetic pathway allows employment of a wide variety of complex-type glycans, which can be introduced to various test systems in vitro and in vivo to evaluate potential biomedical applications. Solid-phase as says with biotinylated sugar receptors revealed discriminatory binding properties of the three neoglycoproteins, especially for the mistleto e lectin. This direct assay system is preferable to the measurement of inhibitory capacities with respect to model ligands. Ligand type-and cell type-dependent quantitative differences in the binding properties of the probes were detected by FACScan analyses with a panel of tumor cell lines and by monitoring of staining in tissue sections for small cell and non-small-cell lung cancer and mesotheliomas. Biodistributio n of iodinated neoglycoproteins in mice gave a prolonged presence of t he sialylated probes in serum. Relative to the nonasaccharide, the upt ake, especially of the iodinated neoglycoprotein with alpha 2,3-sialyl ated ligand chains, was clearly elevated in mice for kidneys and Ehrli ch tumors. On the basis of the documented feasibility of these applica tions, it is concluded that the further elaboration of glycan chain va riants by the described synthetic approach in combination with the giv en test panel is warranted to evaluate the potential of complex glycan chain-carrying neoglycoproteins for diagnostic and therapeutic purpos es.