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

We report on the efficiencies of structurally different but well defined multivalent sLex-ligands (di- and trivalent sLex-peptides and sLexbearing liposomes) to block receptor mediated HepG2-cell binding. Using three types of binding assays with distinct receptor accommodations (soluble anti-sLexmonoclonal antibody CSLEX1, immobilized E-selectin, activated HUVECs), we quantified considerable differences of the inhibition efficiencies for the same multivalent sLex-ligands. Compared to the monovalent sLexthe inhibition powers of both (sLex)2-peptides and (sLex)3-peptides were enhanced up to 50-fold for cell binding to the soluble antibody, and that of sLex-liposomes by 7 orders of magnitude. Directed to immobilized E-selectin the inhibition activity was enhanced only 3-fold for (sLex)2-peptides, 10-fold for (sLex)3-peptides but 5 orders of magnitude for sLex-liposomes, respectively. Further decrease of the inhibition efficiencies of glycoligands prepared was observed for cell binding to activated HUVECs. Compared to monovalent sLexwe measured relative efficiencies of 1 for (sLex)2-peptides, of 2 for (sLex)3-peptides but about 20,000 for sLex-liposomes. We concluded that the multivalency of the sLex-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.