heparitin-sulfate and Retinoblastoma

Pigment epithelium-derived factor (PEDF) has binding affinity for cell-surface receptors in retinoblastoma cells and for glycosaminoglycans. We investigated the effects of glycosaminoglycans on PEDF-receptor interactions.. 125I-PEDF formed complexes with protease-resistant components of medium conditioned by human retinoblastoma Y-79 cells. Using specific glycosaminoglycan degrading enzymes in spectrophotometric assays and PEDF-affinity chromatography, we detected heparin and heparan sulfate-like glycosaminoglycans in the Y-79 conditioned media, which had binding affinity for PEDF. The Y-79 conditioned media significantly enhanced the binding of 125I-PEDF to Y-79 cell-surface receptors. However, enzymatic and chemical depletion of sulfated glycosaminoglycans from the Y-79 cell cultures by heparitinase and chlorate treatments decreased the degree of 125I-PEDF binding to cell-surface receptors.. These data indicate that retinoblastoma cells secrete heparin/heparan sulfate with binding affinity for PEDF, which may be important in efficient cell-surface receptor binding.

Topics: Chlorates; Culture Media, Conditioned; Glycosaminoglycans; Heparin; Heparitin Sulfate; Humans; Iodine Radioisotopes; Lyases; Pigment Epithelium of Eye; Receptors, Cell Surface; Receptors, Neuropeptide; Retinal Neoplasms; Retinoblastoma; Tumor Cells, Cultured