Enhancing PET Signal at Target Tissue in Vivo: Dendritic and Multimeric Tris(hydroxypyridinone) Conjugates for Molecular Imaging of α<sub>v</sub>β<sub>3</sub>Integrin Expression with Gallium-68
作者:Cinzia Imberti、Samantha Y. A. Terry、Carleen Cullinane、Fiona Clarke、Georgina H. Cornish、Nisha K. Ramakrishnan、Peter Roselt、Andrew P. Cope、Rodney J. Hicks、Philip J. Blower、Michelle T. Ma
DOI:10.1021/acs.bioconjchem.6b00621
日期:2017.2.15
Tris(hydroxypyridinone) chelators conjugated to peptides can rapidly complex the positron-emitting isotope gallium-68 (68Ga) under mild conditions, and the resulting radiotracers can delineate peptide receptor expression at sites of diseased tissue in vivo. We have synthesized a dendritic bifunctional chelator containing nine 1,6-dimethyl-3-hydroxypyridin-4-one groups (SCN-HP9) that can coordinate up to three Ga3+ ions. This derivative has been conjugated to a trimeric peptide (RGD3) containing three peptide groups that target the αvβ3 integrin receptor. The resulting dendritic compound, HP9-RGD3, can be radiolabeled in 97% radiochemical yield at a 3-fold higher specific activity than its homologues HP3-RGD and HP3-RGD3 that contain only a single metal binding site. PET scanning and biodistribution studies show that [68Ga(HP9-RGD3)] demonstrates higher receptor-mediated tumor uptake in animals bearing U87MG tumors that overexpress αvβ3 integrin than [68Ga(HP3-RGD)] and [68Ga(HP3-RGD3)]. However, concomitant nontarget organ retention of [68Ga(HP9-RGD3)] results in low tumor to nontarget organ contrast in PET images. On the other hand, the trimeric peptide homologue containing a single tris(hydroxypyridinone) chelator, [68Ga(HP3-RGD3)], clears nontarget organs and exhibits receptor-mediated uptake in mice bearing tumors and in mice with induced rheumatoid arthritis. PET imaging with [68Ga(HP3-RGD3)] enables clear delineation of αvβ3 integrin receptor expression in vivo.
与肽结合的三羟基吡啶酮螯合剂可以在温和的条件下快速络合正电子发射同位素镓-68(68Ga),由此产生的放射性痕量物质可以描述体内病变组织部位的肽受体表达情况。我们合成了一种含有九个 1,6-二甲基-3-羟基吡啶-4-酮基团的树枝状双功能螯合剂(SCN-HP9),它可以配位多达三个 Ga3+ 离子。这种衍生物与含有三个肽基的三聚肽(RGD3)共轭,RGD3 的目标是 αvβ3 整合素受体。由此产生的树枝状化合物 HP9-RGD3 能以 97% 的放射化学收率进行放射性标记,其特异性活性比只含有单一金属结合位点的同源物 HP3-RGD 和 HP3-RGD3 高 3 倍。PET 扫描和生物分布研究表明,与[68Ga(HP3-RGD)]和[68Ga(HP3-RGD3)]相比,[68Ga(HP9-RGD3)]在过表达 αvβ3 整合素的 U87MG 肿瘤动物体内显示出更高的受体介导的肿瘤摄取率。然而,[68Ga(HP9-RGD3)]同时在非靶器官滞留会导致 PET 图像中肿瘤与非靶器官对比度较低。另一方面,含有单个三(羟基吡啶酮)螯合剂的三聚肽同源物[68Ga(HP3-RGD3)]能清除非靶器官,并在患有肿瘤的小鼠和诱发类风湿性关节炎的小鼠中表现出受体介导的摄取。使用[68Ga(HP3-RGD3)]进行正电子发射计算机断层成像可清楚地描述体内αvβ3整合素受体的表达。