Short synthetic octapeptide analogs derived from the native somatostatin peptides SST-14 and SST-28, namely, octreotate (TATE) or octreotide (TOC), bind with high affinity to somatostatin receptors (sstr), mainly to subtypes 2 and 5, which are expressed in high density on neuroendocrine tumors (NET). Therefore, radiolabeled TATE or TOC derivatives represent highly valuable imaging probes for NET diagnosis by positron emission tomography (PET). The aim of our study was the development of an 18F-labeled octreotate analog as an alternative radiotracer for the clinically established 68Ga-DOTATOC and 68Ga-DOTATATE. We applied our previously developed method based on copper(I)-catalyzed azide–alkyne cycloaddition (CuAAC) to the radiosynthesis of 18F-fluoroglycosylated TATE ([18F]FGlc-TATE). [18F]FGlc-TATE was obtained in high yields of 19–22% (non-decay-corrected, referred to [18F]fluoride) and in high specific activities of 32–106 GBq/μmol. [18F]FGlc-TATE showed high affinity to sstr expressed on AR42J cells (IC50 = 4.2 nM) with fast and high internalization, and a beneficial logD7.4 of −1.8. In AR42J tumor bearing nude mice, [18F]FGlc-TATE showed high and specific tumor uptake of 5.6%ID/g at 60 min post-injection, as determined by blocking experiments using octreotide, and fast clearance from other organs, resulting in excellent tumor-to-blood ratios increasing from 9 to 17 from 30 to 60 min post-injection. Small animal PET studies revealed high uptake of [18F]FGlc-TATE in the tumor which could be blocked with octreotide by >99%. Overall, [18F]FGlc-TATE revealed excellent in vitro and in vivo properties and is therefore a viable alternative 18F-labeled radiopeptide for imaging somatostatin receptor-positive tumors by PET.
从原生体
生长抑素肽 SST-14 和 SST-28 提取的短合成八肽类似物,即
奥曲肽 (TATE) 或
奥曲肽 (TOC),与体
生长抑素受体 (sSTr) 具有高亲和力,主要与亚型 2 和亚型 5 结合,这些受体在神经内分泌肿瘤 (NET) 上高密度表达。因此,放射性标记的 TATE 或 TOC 衍
生物是通过正电子发射断层扫描(PET)诊断 NET 的极具价值的成像探针。我们研究的目的是开发一种 18F 标记的辛辣酸类似物,作为临床上常用的 68Ga-DOT
ATOC 和 68Ga-DOTATATE 的替代放射性示踪剂。我们将之前开发的基于
铜(I)催化
叠氮-炔环加成(Cu
AAC)的方法应用于 18F
氟糖基化 TATE([18F]FGlc-TATE)的放射合成。[18F]FGlc-TATE 的高产率为 19-22%(非衰变校正,指[18F]
氟化物),高比活度为 32-106 GBq/μmol。[18F]FGlc-TATE对AR42J细胞上表达的sSTr具有高亲和力(IC50 = 4.2 nM),内化速度快且高,有益的logD7.4为-1.8。在携带 AR42J 肿瘤的裸鼠体内,[18F]FGlc-TATE 在注射后 60 分钟显示出很高的特异性肿瘤摄取率(5.6%ID/g),这是由使用
奥曲肽进行的阻断实验确定的,并且能快速从其他器官清除,从而使肿瘤与血液的比率在注射后 30 至 60 分钟内从 9 增至 17。小动物 PET 研究显示,[18F]FGlc-TATE 在肿瘤中的摄取率很高,用
奥曲肽进行阻断可达到 99% 以上。总之,[18F]FGlc-TATE 在体外和体内均显示出优异的特性,因此是一种可行的 18F 标记放射性
多肽,可用于通过 PET 对体
生长抑素受体阳性肿瘤进行成像。