College of Pharmacy, University of New Mexico, Albuquerque, New Mexico 87131, United States.
Bioconjug Chem. 2011 Aug 17;22(8):1682-9. doi: 10.1021/bc200252j. Epub 2011 Jul 20.
The purpose of this study was to develop novel radiolabeled gonadotropin-releasing hormone (GnRH) receptor-targeting peptides for breast cancer imaging. Three novel 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA)-conjugated GnRH peptides were designed and synthesized. The radiometal chelator DOTA was conjugated to the epsilon or alpha amino group of D-lysine, or the epsilon amino group of L-lysine via an Ahx {aminohexanoic acid} linker to generate DOTA-Ahx-(D-Lys(6)-GnRH1), DOTA-Ahx-(D-Lys(6)-GnRH2) and DOTA-Ahx-(L-Lys(6)-GnRH3), respectively. The conjugation of the DOTA to the epsilon amino group of D-lysine (rather than alpha amino group of D-lysine nor epsilon amino group of L-lysine) maintained the nanomolar GnRH receptor binding affinity. The IC(50) values of DOTA-Ahx-(D-Lys(6)-GnRH1), DOTA-Ahx-(D-Lys(6)-GnRH2) and DOTA-Ahx-(L-Lys(6)-GnRH3) were 36.1 nM, 10.6 mM and 4.3 mM, respectively. Since only DOTA-Ahx-(D-Lys(6)-GnRH1) displayed nanomolar receptor binding affinity, the specific GnRH receptor binding of (111)In-DOTA-Ahx-(D-Lys(6)-GnRH1) was determined in human GnRH receptor membrane preparations. Furthermore, the biodistribution and tumor imaging properties of (111)In-DOTA-Ahx-(D-Lys(6)-GnRH1) were examined in MDA-MB-231 human breast cancer-xenografted nude mice. (111)In-DOTA-Ahx-(D-Lys(6)-GnRH1) exhibited specific GnRH receptor binding and rapid tumor uptake (1.76 ± 0.58% ID/g at 0.5 h postinjection) coupled with fast whole-body clearance through the urinary system. The MDA-MB-231 human breast cancer-xenografted tumor lesions were clearly visualized by single photon emission computed tomography (SPECT)/CT at 1 h postinjection of (111)In-DOTA-Ahx-(D-Lys(6)-GnRH1). The profound impact of DOTA position on the binding affinity of the GnRH peptide provided a new insight into the design of novel radiolabeled GnRH peptides. The successful imaging of MDA-MB-231 human breast cancer-xenografted tumor lesions using (111)In-DOTA-Ahx-(D-Lys(6)-GnRH1) suggested its potential as a novel imaging probe for human breast cancer imaging.
本研究旨在开发新型放射性标记促性腺激素释放激素（GnRH）受体靶向肽用于乳腺癌成像。设计并合成了三种新型 1,4,7,10-四氮杂环十二烷-1,4,7,10-四乙酸（DOTA）-缀合 GnRH 肽。放射性金属螯合剂 DOTA 通过 Ahx（氨基己酸）接头连接到 D-赖氨酸的ε或α氨基，或 L-赖氨酸的ε氨基，分别生成 DOTA-Ahx-（D-Lys（6）-GnRH1）、DOTA-Ahx-（D-Lys（6）-GnRH2）和 DOTA-Ahx-（L-Lys（6）-GnRH3）。DOTA 与 D-赖氨酸的ε氨基（而不是 D-赖氨酸的α氨基或 L-赖氨酸的ε氨基）的缀合保持了纳摩尔 GnRH 受体结合亲和力。DOTA-Ahx-（D-Lys（6）-GnRH1）、DOTA-Ahx-（D-Lys（6）-GnRH2）和 DOTA-Ahx-（L-Lys（6）-GnRH3）的 IC50 值分别为 36.1 nM、10.6 mM 和 4.3 mM。由于只有 DOTA-Ahx-（D-Lys（6）-GnRH1）显示出纳摩尔受体结合亲和力，因此在人 GnRH 受体膜制剂中确定了（111）In-DOTA-Ahx-（D-Lys（6）-GnRH1）的特异性 GnRH 受体结合。此外，在 MDA-MB-231 人乳腺癌异种移植裸鼠中研究了（111）In-DOTA-Ahx-（D-Lys（6）-GnRH1）的生物分布和肿瘤成像特性。（111）In-DOTA-Ahx-（D-Lys（6）-GnRH1）表现出特异性 GnRH 受体结合和快速肿瘤摄取（注射后 0.5 小时为 1.76±0.58% ID/g），并通过泌尿系统快速清除全身。注射（111）In-DOTA-Ahx-（D-Lys（6）-GnRH1）1 小时后，单光子发射计算机断层扫描（SPECT）/CT 清楚地显示了 MDA-MB-231 人乳腺癌异种移植肿瘤病变。DOTA 位置对 GnRH 肽结合亲和力的深远影响为新型放射性标记 GnRH 肽的设计提供了新的见解。使用（111）In-DOTA-Ahx-（D-Lys（6）-GnRH1）成功成像 MDA-MB-231 人乳腺癌异种移植肿瘤病变表明其可能成为人乳腺癌成像的新型成像探针。
