Department of Biochemistry, University of Missouri-Columbia School of Medicine, Columbia, Missouri, USA.
J Nucl Med. 2011 Nov;52(11):1819-26. doi: 10.2967/jnumed.111.093716. Epub 2011 Oct 7.
Thomsen-Friedenreich (TF) antigen is a disaccharide, galactose β1-3 N-acetylgalactosamine (Galβ1-3GalNAc), expressed on the cell surfaces of most human carcinomas including breast. In this study, we synthesized and evaluated the in vitro and in vivo properties of a (64)Cu-radiolabeled TF antigen-specific peptide derived from bacteriophage display for the purpose of breast tumor targeting and PET of human breast tumors in xenografted mice.
The TF antigen-specific peptide IVWHRWYAWSPASRI was synthesized with the chelator 1,4,7-triazacyclononane-1,4,7-triacetic acid (NOTA) at the amino terminus, followed by a Gly-Ser-Gly (GSG) spacer. Amino acids Asp and Arg were introduced at both ends to enhance its solubility. Purified NO2A-GSG-DRD-IVWHRWYAWSPASRI-DRD (NO2A-TFpep) was radiolabeled with (64)Cu and evaluated for binding to human MDA-MB-435 breast cancer cells, 50% inhibitory concentration (IC(50)), and serum stability. In vivo pharmacokinetic and small-animal PET studies were performed using SCID mice bearing MDA-MB-435 tumor xenografts.
(64)Cu-NO2A-TFpep bound to human MDA-MB-435 breast carcinoma cells, whereas almost no binding was observed to normal human breast 184A1 cells. The peptide exhibited an apparent IC(50) value of 70 ± 8.0 nM. In vivo biodistribution studies indicated radiolabeled peptide accumulation in tumors of MDA-MB-435 xenografted SCID mice of approximately 1.10 ± 0.20 percentage injected dose per gram (%ID/g) and 0.90 ± 0.12 %ID/g, at 0.5 and 1 h, respectively. Accumulation of radioactivity was low in other organs, with the exception of liver (1.52 ± 0.12 %ID/g) and kidneys (15.4 ± 1.73 %ID/g) at 1 h. Live imaging studies with (64)Cu-NO2A-TFpep (15 MBq) demonstrated good tumor uptake at 1 h after injection, whereas no tumor uptake was observed with a scrambled radiolabeled peptide (64)Cu-NO2A-GSG-DRD-RWSWWAVHRIPYSAI-DRD.
(64)Cu-NO2A-TFpep may function as a noninvasive in vivo tumor imaging agent of human breast and other carcinomas expressing the TF carbohydrate antigen. This is the first such TF antigen-targeting peptide used in tumor imaging.
为了对乳腺癌肿瘤进行靶向和正电子发射断层扫描（PET），我们合成并评估了来自噬菌体展示的一种半乳糖 β1-3 N-乙酰半乳糖胺（Galβ1-3GalNAc）的、针对四旋体抗原（TF）的放射性标记肽的体外和体内特性。
我们在氨基末端合成了 TF 抗原特异性肽 IVWHRWYAWSPASRI，带有螯合剂 1,4,7-三氮杂环壬烷-1,4,7-三乙酸（NOTA），然后连接甘氨酸-丝氨酸-甘氨酸（GSG）间隔物。在两端引入氨基酸天冬氨酸和精氨酸以增强其溶解性。纯化的 NO2A-GSG-DRD-IVWHRWYAWSPASRI-DRD（NO2A-TFpep）用（64）Cu 进行放射性标记，并评估其与人类 MDA-MB-435 乳腺癌细胞的结合、半数抑制浓度（IC50）和血清稳定性。使用携带 MDA-MB-435 肿瘤异种移植物的 SCID 小鼠进行体内药代动力学和小动物 PET 研究。
（64）Cu-NO2A-TFpep 与人类 MDA-MB-435 乳腺癌细胞结合，而与正常的人类乳腺 184A1 细胞几乎没有结合。该肽表现出明显的 IC50 值为 70±8.0 nM。体内生物分布研究表明，放射性标记肽在 MDA-MB-435 异种移植 SCID 小鼠肿瘤中的积累约为 1.10±0.20%注入剂量/克（%ID/g）和 0.90±0.12%ID/g，分别在 0.5 和 1 h。除了肝脏（1.52±0.12%ID/g）和肾脏（15.4±1.73%ID/g）外，其他器官中的放射性积累较低，在 1 h 时。使用（64）Cu-NO2A-TFpep（15 MBq）进行的活体成像研究表明，在注射后 1 h 时肿瘤摄取良好，而用随机化的放射性标记肽（64）Cu-NO2A-GSG-DRD-RWSWWAVHRIPYSAI-DRD 则未观察到肿瘤摄取。
（64）Cu-NO2A-TFpep 可作为表达 TF 碳水化合物抗原的人类乳腺癌和其他癌的非侵入性体内肿瘤成像剂。这是第一个用于肿瘤成像的 TF 抗原靶向肽。
