title: Immunogenic and structural properties of the Asn-Gly-Arg (NGR) tumor neovasculature-homing motif.
abstract: Tumor homing peptides containing the NGR motif, such as CNGRC and GNGRG, have been used for delivering cytokines, chemotherapeutic drugs, apoptotic peptides, and liposomes to a CD13 isoform expressed in tumor blood vessels. In view of the potential clinical applications of these drugs and considering the risk that NGR peptides could elicit blocking antibodies we have investigated the immunogenic properties of CNGRC and GNGRG in mice and rabbits, using various products containing these residues and different administration schedules. The results suggest that the immunogenicity of the NGR motif is very low, even when it is conjugated to tumor necrosis factor-alpha or to highly immunogenic carrier proteins. Molecular dynamics simulation experiments showed that both peptides have a strong propensity to populate a turn conformation. Superposition of predicted structures to the CTGNGRGEWKC loop of the 5th type I repeat of human fibronectin, a protein that contains four NGR motives, showed that the root mean square deviation of backbones was 0.7A for GNGRG and 0.5A for NGR. These results suggest that NGR peptides could mimic from an immunological point of view a "self" structure, likely the GNGRG loop of fibronectin, with important implications for the use of these targeting peptides in patients.
authors.affiliation: Department of Biological and Technological Research, San Raffaele H Scientific Institute, 20132 Milan, Italy.
authors.forename: Paola
authors.initials: P
authors.lastname: Di Matteo
authors.forename: Flavio
authors.initials: F
authors.lastname: Curnis
authors.forename: Renato
authors.initials: R
authors.lastname: Longhi
authors.forename: Giorgio
authors.initials: G
authors.lastname: Colombo
authors.forename: Angelina
authors.initials: A
authors.lastname: Sacchi
authors.forename: Luca
authors.initials: L
authors.lastname: Crippa
authors.forename: Maria Pia
authors.initials: MP
authors.lastname: Protti
authors.forename: Mirco
authors.initials: M
authors.lastname: Ponzoni
authors.forename: Salvatore
authors.initials: S
authors.lastname: Toma
authors.forename: Angelo
authors.initials: A
authors.lastname: Corti
mesh_terms: D020816:Amino Acid Motifs / Q000276:immunology; D000595:Amino Acid Sequence; D020533:Angiogenesis Inhibitors / Q000008:administration & dosage; D000818:Animals; D000970:Antineoplastic Agents / Q000008:administration & dosage*; D005353:Fibronectins / Q000276:immunology; D051379:Mice; D008969:Molecular Sequence Data; D009369:Neoplasms / Q000098:blood supply*; D009842:Oligopeptides / Q000737:chemistry / Q000276:immunology*; D010455:Peptides / Q000737:chemistry / Q000276:immunology*; D010456:Peptides, Cyclic / Q000737:chemistry / Q000276:immunology*; D011487:Protein Conformation; D011817:Rabbits
chemical_list: D020533:Angiogenesis Inhibitors; D000970:Antineoplastic Agents; D005353:Fibronectins; D009842:Oligopeptides; D010455:Peptides; D010456:Peptides, Cyclic