title: Critical role of flanking residues in NGR-to-isoDGR transition and CD13/integrin receptor switching.
abstract: Various NGR-containing peptides have been exploited for targeted delivery of drugs to CD13-positive tumor neovasculature. Recent studies have shown that compounds containing this motif can rapidly deamidate and generate isoaspartate-glycine-arginine (isoDGR), a ligand of alphavbeta3-integrin that can be also exploited for drug delivery to tumors. We have investigated the role of NGR and isoDGR peptide scaffolds on their biochemical and biological properties. Peptides containing the cyclic CNGRC sequence could bind CD13-positive endothelial cells more efficiently than those containing linear GNGRG. Peptide degradation studies showed that cyclic peptides mostly undergo NGR-to-isoDGR transition and CD13/integrin switching, whereas linear peptides mainly undergo degradation reactions involving the alpha-amino group, which generate non-functional six/seven-membered ring compounds, unable to bind alphavbeta3, and small amount of isoDGR. Structure-activity studies showed that cyclic isoDGR could bind alphavbeta3 with an affinity >100-fold higher than that of linear isoDGR and inhibited endothelial cell adhesion and tumor growth more efficiently. Cyclic isoDGR could also bind other integrins (alphavbeta5, alphavbeta6, alphavbeta8, and alpha5beta1), although with 10-100-fold lower affinity. Peptide linearization caused loss of affinity for all integrins and loss of specificity, whereas alpha-amino group acetylation increased the affinity for all tested integrins, but caused loss of specificity. These results highlight the critical role of molecular scaffold on the biological properties of NGR/isoDGR peptides. These findings may have important implications for the design and development of anticancer drugs or tumor neovasculature-imaging compounds, and for the potential function of different NGR/isoDGR sites in natural proteins.
authors.affiliation: Division of Molecular Oncology and IIT Network Research Unit of Molecular Neuroscience, San Raffaele Scientific Institute, 20132 Milan.
authors.forename: Flavio
authors.initials: F
authors.lastname: Curnis
authors.forename: Angela
authors.initials: A
authors.lastname: Cattaneo
authors.forename: Renato
authors.initials: R
authors.lastname: Longhi
authors.forename: Angelina
authors.initials: A
authors.lastname: Sacchi
authors.forename: Anna Maria
authors.initials: AM
authors.lastname: Gasparri
authors.forename: Fabio
authors.initials: F
authors.lastname: Pastorino
authors.forename: Paola
authors.initials: P
authors.lastname: Di Matteo
authors.forename: Catia
authors.initials: C
authors.lastname: Traversari
authors.forename: Angela
authors.initials: A
authors.lastname: Bachi
authors.forename: Mirco
authors.initials: M
authors.lastname: Ponzoni
authors.forename: Gian-Paolo
authors.initials: GP
authors.lastname: Rizzardi
authors.forename: Angelo
authors.initials: A
authors.lastname: Corti
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology; D018826:CD13 Antigens / Q000378:metabolism*; D002448:Cell Adhesion; D004220:Disulfides / Q000737:chemistry; D042783:Endothelial Cells / Q000166:cytology; D006801:Humans; D016023:Integrins / Q000378:metabolism*; D026581:Isoaspartic Acid / Q000737:chemistry; D051379:Mice; D008807:Mice, Inbred BALB C; D009842:Oligopeptides / Q000737:chemistry*; D011485:Protein Binding; D011994:Recombinant Proteins / Q000737:chemistry; D013329:Structure-Activity Relationship
chemical_list: D000970:Antineoplastic Agents; D004220:Disulfides; D016023:Integrins; D026581:Isoaspartic Acid; C526428:NGR peptide; D009842:Oligopeptides; D011994:Recombinant Proteins; D018826:CD13 Antigens