Multivalent sialyl Lewis x ligands of definite structures as inhibitors of E-selectin mediated cell adhesion

Abstract

We report on the efficiencies of structurally different but well defined multivalent sLe(x)-ligands (di- and trivalent sLe(x)-peptides and sLe(x) bearing liposomes) to block receptor mediated HepG2-cell binding. Using three types of binding assays with distinct receptor accommodations (soluble anti- sLe(x) monoclonal antibody CSLEX1, immobilized E-selectin, activated HUVECs), we quantified considerable differences of the inhibition efficiencies for the same multivalent sLe(x)-ligands. Compared to the monovalent sLe(x) the inhibition powers of both (sLe(x))2-peptides and (sLe(x))3-peptides were enhanced up to 50-fold for cell binding to the soluble antibody, and that of sLe(x)-liposomes by 7 orders of magnitude. Directed to immobilized E-selectin the inhibition activity was enhanced only 3-fold for (sLe(x))2-peptides, 10- fold for (sLe(x))3-peptides but 5 orders of magnitude for sLe(x)-liposomes, respectively. Further decrease of the inhibition efficiencies of glycoligands prepared was observed for cell binding to activated HUVECs. Compared to monovalent sLe(x) we measured relative efficiencies of 1 for (sLe(x))2- peptides, of 2 for (sLe(x))3-peptides but about 20,000 for sLe(x)-liposomes. We concluded that the multivalency of the sLe(x)-ligands prepared is an essential but not sufficient precondition for a high inhibition potency. Additionally, structural properties of the inhibitors determine their binding behavior, which must be considered for the design of potential therapeutic probes.