Department of Nuclear Medicine, Xijing Hospital, Fourth Military Medical University, Xi'an, Shaanxi, 710032, People's Republic of China.
Amino Acids. 2013 May;44(5):1337-45. doi: 10.1007/s00726-013-1469-1. Epub 2013 Mar 1.
CD13 receptor plays a critical role in tumor angiogenesis and metastasis. We therefore aimed to develop (99m)Tc-labeled monomeric and dimeric NGR-containing peptides, namely, NGR1 and NGR2, for SPECT imaging of CD13 expression in HepG2 hepatoma xenografts. Both NGR-containing monomer and dimer were synthesized and labeled with (99m)Tc. In vivo receptor specificity was demonstrated by successful blocking of tumor uptake of (99m)Tc-NGR dimer in the presence of 20 mg/kg NGR2 peptide. Western blot and immunofluorescence staining confirmed the CD13 expression in HepG2 cells. The NGR dimer showed higher binding affinity and cell uptake in vitro than the NGR-containing monomer, presumably due to a multivalency effect. (99m)Tc-Labeled monomeric and dimeric NGR-containing peptides were subjected to SPECT imaging and biodistribution studies. SPECT scans were performed in HepG2 tumor-bearing mice at 1, 4, 12, and 24 h post-injection of ~7.4 MBq tracers. The metabolism of tracers was determined in major organs at different time points after injection which demonstrated rapid, significant tumor uptake and slow tumor washout for both traces. Predominant clearance from renal and hepatic system was also observed in (99m)Tc-NGR1 and (99m)Tc-NGR2. In conclusion, monomeric and dimeric NGR peptide were developed and labeled with (99m)Tc successfully, while the high integrin avidity and long retention in tumor make (99m)Tc-NGR dimer a promising agent for tumor angiogenesis imaging.
CD13 受体在肿瘤血管生成和转移中起着关键作用。因此，我们旨在开发（99m）Tc 标记的单体和二聚体含 NGR 的肽，即 NGR1 和 NGR2，用于 HepG2 肝癌异种移植中 CD13 表达的 SPECT 成像。合成并标记了含有 NGR 的单体和二聚体与（99m）Tc。通过在存在 20mg/kg NGR2 肽的情况下成功阻断肿瘤摄取（99m）Tc-NGR 二聚体，证明了体内受体特异性。Western blot 和免疫荧光染色证实了 HepG2 细胞中 CD13 的表达。NGR 二聚体在体外显示出比含 NGR 的单体更高的结合亲和力和细胞摄取率，这可能是由于多价效应。（99m）Tc 标记的单体和二聚体含 NGR 的肽进行了 SPECT 成像和生物分布研究。在注射~7.4MBq 示踪剂后 1、4、12 和 24h，对荷瘤 HepG2 小鼠进行 SPECT 扫描。在注射后不同时间点测定了示踪剂在主要器官中的代谢情况，结果表明两种示踪剂均具有快速、显著的肿瘤摄取和缓慢的肿瘤清除。（99m）Tc-NGR1 和（99m）Tc-NGR2 也观察到主要从肾脏和肝脏系统清除。总之，成功地开发并标记了单体和二聚体 NGR 肽，而高整联蛋白亲和力和在肿瘤中的长时间保留使（99m）Tc-NGR 二聚体成为肿瘤血管生成成像的有前途的试剂。
