Media conditioned by retinoblastoma Y-79 cells enhances the 125 I-PEDF binding to cell-surface receptors. Binding to human retinoblastoma Y-79 cells (1.5 × 105 cells/ml) was performed with 0.8 nM 125I-PEDF (136,000 cpm/point) in their overnight culturing media (conditioned media) or non-conditioned media (fresh media). Free and bound ligand was separated by filtration through glass fiber filters under vacuum. Non-specific binding was binding in the presence of 125-fold molar excess of unlabelled PEDF. Specific binding was calculated by subtracting the non-specific from the total binding. All experimental points are given as the average of triplicates.