title: 111In-labeled cystine-knot peptides based on the Agouti-related protein for targeting tumor angiogenesis.
abstract: Agouti-related protein (AgRP) is a 4-kDa cystine-knot peptide of human origin with four disulfide bonds and four solvent-exposed loops. The cell adhesion receptor integrin α(v)β(3) is an important tumor angiogenesis factor that determines the invasiveness and metastatic ability of many malignant tumors. AgRP mutants have been engineered to bind to integrin α(v)β(3) with high affinity and specificity using directed evolution. Here, AgRP mutants 7C and 6E were radiolabeled with (111)In and evaluated for in vivo targeting of tumor integrin α(v)β(3) receptors. AgRP peptides were conjugated to the metal chelator 1, 4, 7, 10-tetra-azacyclododecane- N, N', N″, N'''-tetraacetic acid (DOTA) and radiolabeled with (111)In. The stability of the radiopeptides (111)In-DOTA-AgRP-7C and (111)In-DOTA-AgRP-6E was tested in phosphate-buffered saline (PBS) and mouse serum, respectively. Cell uptake assays of the radiolabeled peptides were performed in U87MG cell lines. Biodistribution studies were performed to evaluate the in vivo performance of the two resulting probes using mice bearing integrin-expressing U87MG xenograft tumors. Both AgRP peptides were easily labeled with (111)In in high yield and radiochemical purity (>99%). The two probes exhibited high stability in phosphate-buffered saline and mouse serum. Compared with (111)In-DOTA-AgRP-6E, (111)In-DOTA-AgRP-7C showed increased U87MG tumor uptake and longer tumor retention (5.74 ± 1.60 and 1.29 ± 0.02%ID/g at 0.5 and 24 h, resp.), which was consistent with measurements of cell uptake. Moreover, the tumor uptake of (111)In-DOTA-AgRP-7C was specifically inhibited by coinjection with an excess of the integrin-binding peptidomimetic c(RGDyK). Thus, (111)In-DOTA-AgRP-7C is a promising probe for targeting integrin α(v)β(3) positive tumors in living subjects.
authors.affiliation: Department of Nuclear Medicine, Shanghai Sixth People's Hospital, Shanghai Jiao Tong University, Shanghai 200233, China.
authors.forename: Lei
authors.initials: L
authors.lastname: Jiang
authors.forename: Zheng
authors.initials: Z
authors.lastname: Miao
authors.forename: Richard H
authors.initials: RH
authors.lastname: Kimura
authors.forename: Adam P
authors.initials: AP
authors.lastname: Silverman
authors.forename: Gang
authors.initials: G
authors.lastname: Ren
authors.forename: Hongguang
authors.initials: H
authors.lastname: Liu
authors.forename: Hankui
authors.initials: H
authors.lastname: Lu
authors.forename: Jennifer R
authors.initials: JR
authors.lastname: Cochran
authors.forename: Zhen
authors.initials: Z
authors.lastname: Cheng
mesh_terms: D054369:Agouti-Related Protein / Q000737:chemistry / Q000493:pharmacokinetics*; D000595:Amino Acid Sequence; D000818:Animals; D001932:Brain Neoplasms / Q000098:blood supply / Q000000981:diagnostic imaging / Q000378:metabolism; D045744:Cell Line, Tumor; D057771:Cystine-Knot Miniproteins / Q000737:chemistry / Q000493:pharmacokinetics*; D005260:Female; D005909:Glioblastoma / Q000098:blood supply* / Q000000981:diagnostic imaging* / Q000378:metabolism; D006573:Heterocyclic Compounds, 1-Ring / Q000737:chemistry / Q000493:pharmacokinetics; D006801:Humans; D007205:Indium Radioisotopes / Q000737:chemistry / Q000493:pharmacokinetics*; D051379:Mice; D008819:Mice, Nude; D008969:Molecular Sequence Data; D009389:Neovascularization, Pathologic / Q000000981:diagnostic imaging / Q000378:metabolism; D011877:Radionuclide Imaging; D014018:Tissue Distribution; D014183:Transplantation, Heterologous
chemical_list: D054369:Agouti-Related Protein; D057771:Cystine-Knot Miniproteins; D006573:Heterocyclic Compounds, 1-Ring; D007205:Indium Radioisotopes; C071349:1,4,7,10-tetraazacyclododecane- 1,4,7,10-tetraacetic acid