Department of Radiology, Rudbeck Laboratory, Uppsala University, Uppsala, Sweden.
Eur J Nucl Med Mol Imaging. 2009 Nov;36(11):1864-73. doi: 10.1007/s00259-009-1176-z. Epub 2009 Jun 6.
The purpose of this study was to design and evaluate a novel platform for labelling of Affibody molecules, enabling both recombinant and synthetic production and site-specific labelling with (99m)Tc or trivalent radiometals.
The HER2-specific Affibody molecule PEP05352 was made by peptide synthesis. The chelator sequence SECG (serine-glutamic acid-cysteine-glycine) was anchored on the C-terminal to allow (99m)Tc labelling. The cysteine can alternatively serve as a conjugation site of the chelator DOTA for indium labelling. The resulting (99m)Tc- and (111)In-labelled Affibody molecules were evaluated both in vitro and in vivo.
Both conjugates retained their capacity to bind to HER2 receptors in vitro and in vivo. The tumour to blood ratio in LS174T xenografts was 30 at 4 h post-injection for both conjugates. Biodistribution data showed that the (99m)Tc-labelled Affibody molecule had a fourfold lower kidney accumulation compared with the (111)In-labelled Affibody molecule while the accumulation in other organs was similar. Gamma camera imaging of the conjugates could clearly visualise the tumours 4 h after injection.
Incorporation of the C-terminal SECG sequence in Affibody molecules provides a general multifunctional platform for site-specific labelling with different nuclides (technetium, indium, gallium, cobalt or yttrium) and for a flexible production (chemical synthesis or recombinant).
本研究旨在设计和评估一种新型的亲和体分子标记平台，使其能够进行重组和合成生产，并实现（99m）Tc 或三价放射性金属的定点标记。
HER2 特异性亲和体分子 PEP05352 通过肽合成制备。螯合剂序列 SECG（丝氨酸-谷氨酸-半胱氨酸-甘氨酸）连接在 C 末端，以允许（99m）Tc 标记。该半胱氨酸也可以作为螯合剂 DOTA 的缀合位点，用于铟标记。所得（99m）Tc 和（111）In 标记的亲和体分子在体外和体内进行了评估。
两种缀合物在体外和体内均保留了与 HER2 受体结合的能力。在 LS174T 异种移植瘤中，两种缀合物在注射后 4 小时的肿瘤与血液比分别为 30。生物分布数据表明，与（111）In 标记的亲和体分子相比，（99m）Tc 标记的亲和体分子的肾脏积累降低了四倍，而其他器官的积累则相似。注射后 4 小时，两种缀合物的伽马相机成像均能清晰地显示肿瘤。
在亲和体分子中引入 C 末端 SECG 序列为不同核素（锝、铟、镓、钴或钇）的定点标记以及灵活的生产（化学合成或重组）提供了一个通用的多功能平台。
