Synthesis, binding affinity, and inhibitory capacity of cyclodextrin-based multivalent glycan ligands for human galectin-3

Human galectin 3 (Gal-3) has been implicated to play important roles in different biological recognition processes such as tumor growth and cancer metastasis. High-affinity Gal-3 ligands are desirable for functional studies and as inhibitors for potential therapeutic development. We report here a facile synthesis of β-cyclodextrin (CD)-based Tn and TF antigen-containing multivalent ligands via a click reaction. Binding studies indicated that the synthetic multivalent glycan ligands demonstrated a clear clustering effect in binding to human Gal-3, with up to 153-fold enhanced relative affinity in comparison with the monomeric glycan ligand. The GalNAc (Tn antigen) containing heptavalent ligand showed the highest affinity for human Gal-3 among the synthetic ligands tested, with an EC50 of 1.4 μM in binding to human Gal-3. A cell-based assay revealed that the synthetic CD-based multivalent ligands could efficiently inhibit Gal-3 binding to human airway epithelial cells, with an inhibitory capacity consistent with their binding affinity measured by SPR. The synthetic cyclodextrin-based ligands described in this study should be valuable for functional studies of human Gal-3 and potentially for therapeutic applications.