Department of Chemistry and Applied Biosciences (D-CHAB), Laboratory of Organic Chemistry (LOC) , ETH , CH-8093 Zurich , Switzerland.
Department of Chemistry and Applied Biosciences (D-CHAB), Institute of Pharmaceutical Sciences (IPW) , ETH , CH-8093 Zurich , Switzerland.
Bioconjug Chem. 2019 Mar 20;30(3):657-666. doi: 10.1021/acs.bioconjchem.8b00849. Epub 2019 Jan 14.
Derivatized minigastrin analogues make up a promising class of candidates for targeting cholecystokinin receptor subtype 2 (CCK2R), which is overexpressed on cancer cells of various neuroendocrine tumors. The pentaglutamic acid sequence of minigastrin influences its biological properties. In particular, it plays a crucial role in the kidney reuptake mechanism. However, the importance of the binding affinity and interaction of this region with the receptor on a molecular level remains unclear. To elucidate its structure-activity relationship with CCK2R, we replaced this sequence with various linkers differing in their amount of anionic charge, structural characteristics, and flexibility. Specifically, a flexible aliphatic linker, a linker with only three d-Glu residues, and a structured linker with four adjacent β-glutamic acid residues were evaluated and compared to the lead compound PP-F11N (DOTA-[d-Glu,Nle]gastrin-13). 1,4,7,10-Tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) was conjugated to the minigastrin derivatives, which allowed radiolabeling with Lutetium-177. The levels of In vitro internalization into MZ-CRC1 cells and in vivo tumor uptake as well as human blood plasma stability increased in the following order: aliphatic linker < three d-Glu < (β-Glu) < (d-Glu). The in vitro and in vivo behavior was therefore significantly improved with anionic charges. Computational modeling of a CCK2 receptor-ligand complex revealed ionic interactions between cationic residues (Arg and His) of the receptor and anionic residues of the ligand in the linker.
衍生的小胃泌素类似物构成了一类有前途的候选物，可用于靶向胆囊收缩素受体亚型 2（CCK2R），该受体在各种神经内分泌肿瘤的癌细胞上过度表达。小胃泌素的五聚谷氨酸序列影响其生物学特性。特别是，它在肾脏重摄取机制中起着至关重要的作用。然而，该区域与受体在分子水平上的结合亲和力和相互作用的重要性仍不清楚。为了阐明其与 CCK2R 的结构-活性关系，我们用在阴离子电荷、结构特征和灵活性方面存在差异的各种接头取代了该序列。具体来说，评估并比较了柔性脂肪族接头、仅含三个 d-Glu 残基的接头和具有四个相邻β-谷氨酸残基的结构接头与先导化合物 PP-F11N（DOTA-[d-Glu，Nle]gastrin-13）。1,4,7,10-四氮杂环十二烷-1,4,7,10-四乙酸（DOTA）与小胃泌素衍生物缀合，允许用镥-177 进行放射性标记。MZ-CRC1 细胞内内化水平、体内肿瘤摄取以及人血浆稳定性按以下顺序增加：脂肪族接头 < 三个 d-Glu <（β-Glu）<（d-Glu）。因此，阴离子电荷使体外和体内行为得到了显著改善。CCK2 受体-配体复合物的计算建模揭示了受体中的阳离子残基（Arg 和 His）与配体接头中的阴离子残基之间的离子相互作用。
