期刊
MOLECULAR PHARMACEUTICS
卷 11, 期 11, 页码 3947-3956出版社
AMER CHEMICAL SOC
DOI: 10.1021/mp5003043
关键词
affibody; EGFR; PET; F-18; NOTA; CBT
资金
- Office of Science (BER), U.S. Department of Energy [DE-SC0008397]
- In vivo Cellular Molecular Imaging Center (ICMIC) [P50 CA114747]
- National Natural Science Foundation of China [81071182]
- Medical Innovation Foundation of Fujian, China [2009-CXB-46]
The epidermal growth factor receptor (EGFR) serves as an attractive target for cancer molecular imaging and therapy. Our previous positron emission tomography (PET) studies showed that the EGFR-targeting affibody molecules Cu-64-DOTA-ZEGFR:1907 and F-18-FBEM-ZEGFR:1907 can discriminate between high and low EGFR-expression tumors and have the potential for patient selection for EGFR-targeted therapy. Compared with Cu-64, F-18 may improve imaging of EGFR-expression and is more suitable for clinical application, but the labeling reaction of F-18-FBEM-ZEGFR:1907 requires a long synthesis time. The aim of the present study is to develop a new generation of F-18 labeled affibody probes ((AlF)-F-18-NOTA-ZEGFR:1907 and F-18-CBT-ZEGFR:1907) and to determine whether they are suitable agents for imaging of EGFR expression. The first approach consisted of conjugating ZEGFR:1907 with NOTA and radiolabeling with (AlF)-F-18 to produce (AlF)-F-18-NOTA-ZEGFR:1907. In a second approach the prosthetic group F-18-labeled-2-cyanobenzothiazole (F-18-CBT) was conjugated to Cys-ZEGFR:1907 to produce F-18-CBT-ZEGFR:1907. Binding affinity and specificity of (AlF)-F-18-NOTA-ZEGFR:1907 and F-18-CBT-ZEGFR:1907 to EGFR were evaluated using A431 cells. Biodistribution and PET studies were conducted on mice bearing A431 xenografts after injection of (AlF)-F-18-NOTA-ZEGFR:1907 or F-18-CBT-ZEGFR:1907 with or without coinjection of unlabeled affibody proteins. The radiosyntheses of (AlF)-F-18-NOTA-ZEGFR:1907 and F-18-CBT-ZEGFR:1907 were completed successfully within 40 and 120 min with a decay-corrected yield of 15% and 41% using a 2-step, 1-pot reaction and 2-step, 2-pot reaction, respectively. Both probes bound to EGFR with low nanomolar affinity in A431 cells. Although F-18-CBT-ZEGFR:1907 showed instability in vivo, biodistribution studies revealed rapid and high tumor accumulation and quick clearance from normal tissues except the bones. In contrast, (AlF)-F-18-NOTA-ZEGFR:1907 demonstrated high in vitro and in vivo stability, high tumor uptake, and relative low uptake in most of the normal organs except the liver and kidneys at 3 h after injection. The specificity of both probes for A431 tumors was confirmed by their lower uptake on coinjection of unlabeled affibody. PET studies showed that (AlF)-F-18-NOTA-ZEGFR:1907 and F-18-CBT-ZEGFR:1907 could clearly identify EGFR positive tumors with good contrast. Two strategies for F-18-labeling of affibody molecules were successfully developed as two model platforms using NOTA or CBT coupling to affibody molecules that contain an N-terminal cysteine. (AlF)-F-18-NOTA-ZEGFR:1907 and F-18-CBT-ZEGFR:1907 can be reliably obtained in a relatively short time. Biodistribution and PET studies demonstrated that (AlF)-F-18-NOTA-ZEGFR:1907 is a promising PET probe for imaging EGFR expression in living mice.
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