Tumor Diagnosis and Therapy in Nuclear Medicine Using Radioactive Technetium and Rhenium Labeled Antitumor Antibody.

本工作的目的是开发新的99m-Tc放射性标记抗肿瘤抗体，用于核医学诊断。利用先前发现的二巯基琥珀酸（Tc-DMS）的多核99m-Tc复合物在肿瘤细胞中积累的特性，估计为与抗体的肿瘤靶向功能相关提供了基础。首先，对放射性标记抗体所需的基本方面进行了筛选。研究了多核Tc-DMS复合物的独特化学性质及其在血液中的稳定性和肿瘤蓄积。特别令人感兴趣的是环境对注射的Tc-DMS的影响；即稀释对约20-30%配体解离的作用，而Tc的多核状态保持稳定。此外，在这种部分解离之后，多核Tc配合物变得pH敏感；在体外细胞实验中，随着pH由中性变为酸性，游离TcO_4^<-3>的肿瘤细胞放射性活性显著增加。另一方面，在肿瘤组织中，有报道称周围细胞pH值低；因此，稀释相关的复合物解离现象已被证明是体内非常特殊的Tc-DMS行为的关键。接下来的任务是建立以多核Tc-DMS复合物结构为放射性标记位点的抗体所需的基础。本文利用异功能交联试剂N-（马来酰亚胺）琥珀酰亚胺合成了DMS配体与抗体分子（IgG）的共轭物，并对其进行了放射性标记。非常初步的数据提供了有希望的结果；因此，可以理解的是，未来对治疗性186-Re标记的研究也是可行的。

The aim of the present work is the development of new 99m-Tc radiolabeled antitumor antibody for diagnostic use in Nuclear Medicine. Exploitation of previously found character of the polynuclear 99m-Tc complex of Dimercaptosuccinic acid (Tc-DMS) to accumulate in tumor cells was estimated as providing the basis to be associated with the tumor targetting function of antibodies.At first, fundamental aspects needed in radiolabeled antibody were screened. The distinctive chemical character of the polynuclear Tc-DMS complex related with its stability in blood and its tumor accumulation were studied. Of particular interest was the effect of the environment on the injected Tc-DMS ; namely, the role of dilution on the dissociation of some 20-30% of the coordinated ligands, while the polynuclear state of Tc remained stable. Moreover, after this partial dissociation, the polynucleated Tc complex became pH sensitive ; in the in-vitro cell experimental, dramatic tumor cell radio activity increase of dissociated TcO_4^<-3> species took place, as the pH changed from neutral to the acidic region. On the other hand, in tumor tissue, low cell surrounding pH has been reported ; thus, the dilution related complex dissociation phenomenon has been demonstrated as holding the key for the very peculiar Tc-DMS behavior in-vivo.The next task was the establishment of the basis required in antibodies holding the polynuclear Tc-DMS complex structure as the radiolabeled site. In this work, a conjugate of the ligand DMS with an antibody molecule (IgG) using the heterofunctional cross linker reagent N- (maleimidocaproyloxy) succinimide was synthesized and radiolabeled. The very preliminar data offered promising results ; so, it is understood that future research on therapeutical 186-Re labeling might be also feasible.