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放射性标记生化性质对 EpCAM 结合工程支架蛋白 DARPin Ec1 肿瘤靶向特性的影响。

Effect of a radiolabel biochemical nature on tumor-targeting properties of EpCAM-binding engineered scaffold protein DARPin Ec1.

机构信息

Molecular Immunology Laboratory, Shemyakin & Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, Russia; Research School of Chemistry and Applied Biomedical Sciences, Research Tomsk Polytechnic University, Tomsk, Russia; Center of Biomedical Engineering, Sechenov University, Moscow, Russia.

Research School of Chemistry and Applied Biomedical Sciences, Research Tomsk Polytechnic University, Tomsk, Russia; Department of Immunology, Genetics and Pathology, Uppsala University, Uppsala, Sweden.

出版信息

Int J Biol Macromol. 2020 Feb 15;145:216-225. doi: 10.1016/j.ijbiomac.2019.12.147. Epub 2019 Dec 19.

Abstract

Radionuclide-based imaging of molecular therapeutic targets might facilitate stratifying patients for specific biotherapeutics. New type of imaging probes, based on designed ankyrin repeat proteins (DARPins), have demonstrated excellent contrast of imaging of human epidermal growth factor type 2 (HER2) expression in preclinical models. We hypothesized that labeling approaches, which result in lipophilic radiometabolites (non-residualizing labels), would provide the best imaging contrast for DARPins that internalize slowly after binding to cancer cells. The hypothesis was tested using DARPin Ec1 that binds to epithelial cell adhesion molecule (EpCAM). EpCAM is a promising therapeutic target. Ec1 was labeled with I using two methods to obtain the non-residualizing labels, while residualizing labels were obtained by labeling it with Tc. All labeled Ec1 variants preserved target specificity and picomolar binding affinity to EpCAM-expressing pancreatic adenocarcinoma BxPC-3 cells. In murine models, all the variants provided similar tumor uptake. However, I-PIB-H-Ec1 had noticeably lower retention in normal tissues, which provided appreciably higher tumor-to-organ ratios. Furthermore, I-PIB-H-Ec1 demonstrated the highest imaging contrast in preclinical models than any other EpCAM-imaging agent tested so far. In conclusion, DARPin Ec1 in combination with a non-residualizing label is a promising probe for imaging EpCAM expression a few hours after injection.

摘要

基于放射性核素的分子治疗靶点成像可能有助于对特定生物治疗药物进行分层。新型成像探针基于设计的锚蛋白重复蛋白(DARPins),已在临床前模型中证明了对人类表皮生长因子 2 型(HER2)表达的出色成像对比度。我们假设,导致亲脂性放射性代谢物(非残留标记)的标记方法将为与癌细胞结合后缓慢内化的 DARPins 提供最佳的成像对比度。该假设使用与上皮细胞黏附分子(EpCAM)结合的 DARPin Ec1 进行了测试。EpCAM 是一种很有前途的治疗靶点。使用两种方法用 I 标记 Ec1 以获得非残留标记,而用 Tc 标记则获得残留标记。所有标记的 Ec1 变体均保留了对表达 EpCAM 的胰腺腺癌细胞 BxPC-3 的靶向特异性和皮摩尔结合亲和力。在小鼠模型中,所有变体均可提供相似的肿瘤摄取。然而,I-PIB-H-Ec1 在正常组织中的保留率明显较低,这提供了明显更高的肿瘤与器官比值。此外,与迄今为止测试的任何其他 EpCAM 成像剂相比,I-PIB-H-Ec1 在临床前模型中提供了最高的成像对比度。总之,与非残留标记结合使用的 DARPin Ec1 是一种很有前途的探针,可在注射后数小时内对 EpCAM 表达进行成像。

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