(Neo)glycoproteins as tools in neuropathology: histochemical patterns of the extent of expression of endogenous carbohydrate-binding receptors, like lectins, in meningiomas.

Abstract

Biotinylated (neo)glycoproteins were used to specifically detect endogenous sugar receptors such as lectins in sections of formaldehydefixed, paraffin-embedded tissue from meningiomas. The histochemical methods used consisted of the application of a carrier protein and various covalently linked sugar moieties, available mainly through chemical synthesis, in an optimized standard protocol. They proved valuable in elucidating differential binding patterns within the various meningioma subtypes. alpha-Fucoside-, beta-galactoside-, alpha-mannoside- and beta-xyloside-specific carbohydrate-binding receptors were detected in all the tumor subclasses examined, although the levels of expression exhibited pronounced quantitative differences. In addition, differences in the extent of histochemical staining were observed, using a labelled carrier protein, derived from N-acetylglucosamine and mannose-6-phosphate moieties, respectively. Quantitative differences in the reaction intensity were also measured in the respective subtypes. Receptors for N-acetyl-D-galactosamine were detected only in the analplastic forms, while glucuronic acid-specific receptors were only present in the meningotheliomatous meningioma. In contrast to the other types, malignant meningiomas failed to show cytoplasmic staining with the alpha-glucoside-specific maltose-(BSA-biotin). Distinct differences in the pattern of expression of endogenous sugar receptors, evaluated by a standard protocol, provided further evidence for a possible additional subtype of meningioma, the submalignant meningioma. Our results suggest that labelled (neo)glycoproteins could be used routinely as tools for assessing the expression of endogenous sugar receptors in diagnostic neuro-oncology.