Endogenous sugar receptor (lectin) profiles of human retinoblastoma and retinoblast cell lines analyzed by cytological markers, affinity chromatography and neoglycoprotein-targeted photolysis.

Plant lectins have previously been employed to map the composition of cellular glycoconjugates on retinoblastoma and other tumor cells. To characterize the cellular receptors in protein-carbohydrate interactions, we have applied cytological markers (fluorescent neoglycoproteins) containing common carbohydrate building-blocks to investigate the presence of endogenous carbohydrate-binding proteins in six human retinoblastoma cell lines and one established human retinoblast cell line. The staining patterns showed similar expression of endogenous sugar receptors in all cell lines, with few qualitative differences. However, application of affinity chromatography using resins with immobilized carbohydrates as affinity ligands to isolate sugar receptors (lectins) with binding specificities for beta-D-galactosides, alpha-D-mannosides, alpha-L-fucosides alpha-D-glucosides and to N-acetyl-D-glucosamine and N-acetyl-D-galactosamine, respectively, revealed significant differences between the cell lines, emphasizing the value of complementary biochemical analysis. To demonstrate the practical use of this type of glycobiochemical profiling, selective photodestruction of retinoblastoma cells in vitro was accomplished following incubation with synthetic neoglycoprotein-hematoporphyrin conjugates and subsequent exposure to light. This phototherapeutical approach thus combined the inherent specificity of a neoglycoprotein for a particular cellular phenotype with targeted drug activation.