Nikolopoulou Anastasia, Maina Theodosia, Sotiriou Petros, Cordopatis Paul, Nock Berthold A
Institute of Radioisotopes-Radiodiagnostic Products, National Center for Scientific Research Demokritos, 153 10 Athens, Greece.
J Pept Sci. 2006 Feb;12(2):124-31. doi: 10.1002/psc.693.
Two somatostatin analogues, [(99m)Tc]Demotide and [(99m)Tc]Demotate 4, were compared with [(99m)Tc]Demotate 1, a previously reported somatostatin receptor subtype 2 (sst(2)) targeting tracer. Conjugates were prepared by coupling an open-chain tetraamine chelator to D-Phe(1) of [Tyr(3)]-octreotide or [Tyr(3)]-octreotate, respectively, via a p-benzylaminodiglycolic acid spacer adopting solid-phase peptide synthesis techniques. Peptide conjugates were collected in a highly pure form after chromatographic purification. Eventually, [(99m)Tc]Demotide and [(99m)Tc]Demotate 4 were obtained in approximately 1 Ci/micromol specific activity and >96% purity after labeling under alkaline conditions. Demotide and Demotate 4 exhibited similar high binding affinities for the sst(2) expressed in AR4-2J cells with IC(50) values 0.16 and 0.10 nM, respectively. The (radio)metallated analogues [(99m)Tc]Demotide and [(99m)Tc]Demotate 4 showed equally high affinities to the sst(2) during saturation binding assays in AR4-2J cell membranes (K(d)s 0.08 and 0.07 nM, respectively). During incubation at 37 degrees C with AR4-2J cells, the radiopeptides internalized effectively via a receptor-mediated process, with [(99m)Tc]Demotate 4 exhibiting a faster internalization rate than [(99m)Tc]Demotide. After injection in athymic mice bearing sst(2)-expressing AR4-2J tumors, the radiotracers showed high and specific uptake in the tumor (>25%ID/g at 1 h) and in the sst(2)-positive organs. However, both [(99m)Tc]Demotide and [(99m)Tc]Demotate 4 showed unfavorably higher background activity, especially in the abdomen, in comparison to [(99m)Tc]Demotate 1 and are, therefore, less suited than [(99m)Tc]Demotate 1 for sst(2)-targeted tumor imaging in man.
将两种生长抑素类似物[（99m）Tc]Demotide和[（99m）Tc]Demotate 4与[（99m）Tc]Demotate 1进行比较，[（99m）Tc]Demotate 1是先前报道的一种靶向生长抑素受体亚型2（sst(2)）的示踪剂。通过采用固相肽合成技术，经对苄基氨基二乙醇酸间隔基，分别将开链四胺螯合剂与[酪氨酸（3）] - 奥曲肽或[酪氨酸（3）] - 奥曲肽的D - 苯丙氨酸（1）偶联，制备缀合物。经色谱纯化后，以高纯度形式收集肽缀合物。最终，在碱性条件下标记后，获得了比活约为1 Ci/μmol且纯度>96%的[（99m）Tc]Demotide和[（99m）Tc]Demotate 4。Demotide和Demotate 4对AR4 - 2J细胞中表达的sst(2)表现出相似的高结合亲和力，IC(50)值分别为0.16和0.10 nM。在AR4 - 2J细胞膜的饱和结合试验中，（放射性）金属化类似物[（99m）Tc]Demotide和[（99m）Tc]Demotate 4对sst(2)也表现出同样高的亲和力（K(d)分别为0.08和0.07 nM）。在37℃与AR4 - 2J细胞共孵育期间，放射性肽通过受体介导的过程有效内化，[（99m）Tc]Demotate 4的内化速率比[（99m）Tc]Demotide快。在接种了表达sst(2)的AR4 - 2J肿瘤的无胸腺小鼠中注射后，放射性示踪剂在肿瘤（1小时时>25%ID/g）和sst(2)阳性器官中表现出高且特异的摄取。然而，与[（99m）Tc]Demotate 1相比，[（99m）Tc]Demotide和[（99m）Tc]Demotate 4均表现出不利的较高本底活性，尤其是在腹部，因此，在人体sst(2)靶向肿瘤成像方面，它们不如[（99m）Tc]Demotate 1适用。
