Barendswaard E C, Scott A M, Divgi C R, Williams C, Coplan K, Riedel E, Yao T J, Gansow O A, Finn R D, Larson S M, Old L J, Welt S
Ludwig Institute for Cancer Research, Heidelberg, Victoria, Australia.
Int J Oncol. 1998 Jan;12(1):45-53. doi: 10.3892/ijo.12.1.45.
Monoclonal antibody (mAb) A33 detects a glycoprotein homogeneously expressed by > 95% of human colon cancers and by normal colon cells. The A33 antigen is not secreted or shed and after mAb A33 binds to antigen on the cell membrane, a fraction of membrane-bound mAb A33 is internalized into endosomes. Phase I 131I-mAb A33 biodistribution studies have shown consistent, specific tumor-targeting, and phase I radioimmunotherapy trials with 131I- or 125I-mAb A33 have demonstrated antitumor effects. Here we describe a nude mouse model that was established using a human colon cancer cell line, SW1222, which grows as a relatively hypovascular, invasive heterotransplant when injected i.m. Peak uptake of 131I-labeled or 111In-chelated mAb A33 was observed at 48-96 h, with a mean of 34% (SE +/- 5.0) and 46.7% (SE +/- 1.7) injected dose per gram of tumor tissue, respectively. 111In-mAb A33 was retained in tumor tissue longer than halide radioimmunoconjugates. The specificity of antibody localization was assessed using a control antibody (tumor uptake and pharmacokinetics), a control tumor, corrections for vascular antibody blood-pooling in tumor tissue, and blocking of radiolabeled mAb A33 localization by pretreating mice with excess unlabeled mAb A33. These experiments demonstrate that mAb A33 localization in tumor was specific, and they emphasize the unexpected rapidity with which the antibody localizes. Our conclusions were confirmed by immunohistochemical techniques which allowed direct visualization of localization and distribution of the humanized version of mAb A33 in tumor tissue. Furthermore, antibody doses approximating tumor-saturating doses demonstrated that a homogeneous distribution of antibody in tumor is possible. This model will be valuable for studies focusing on general physiologic aspects of antibody-to-tumor cell localization and critical as a guide to the evaluation of various A33 antibody constructs and combinations with other therapies for the treatment of colon cancer.
单克隆抗体（mAb）A33可检测到一种糖蛋白，该糖蛋白在超过95%的人类结肠癌及正常结肠细胞中均有均匀表达。A33抗原既不分泌也不脱落，mAb A33与细胞膜上的抗原结合后，一部分膜结合的mAb A33会被内化到内体中。I期131I - mAb A33生物分布研究显示出一致的、特异性的肿瘤靶向性，并且用131I - 或125I - mAb A33进行的I期放射免疫治疗试验已证明具有抗肿瘤作用。在此，我们描述了一种裸鼠模型，该模型是使用人结肠癌细胞系SW1222建立的，当经肌肉注射时，该细胞系会生长为相对低血运、具有侵袭性的异种移植瘤。131I标记的或111In螯合的mAb A33在48 - 96小时达到摄取峰值，每克肿瘤组织的注射剂量平均分别为34%（标准误±5.0）和46.7%（标准误±1.7）。111In - mAb A33在肿瘤组织中的保留时间比卤化物放射免疫缀合物更长。使用对照抗体（肿瘤摄取和药代动力学）、对照肿瘤、校正肿瘤组织中血管抗体血池以及用过量未标记的mAb A33预处理小鼠以阻断放射性标记的mAb A33定位来评估抗体定位的特异性。这些实验表明mAb A33在肿瘤中的定位是特异性的，并且它们强调了抗体定位的意外快速性。我们的结论通过免疫组织化学技术得到证实，该技术能够直接观察到肿瘤组织中mAb A33人源化版本的定位和分布。此外，接近肿瘤饱和剂量的抗体剂量表明抗体在肿瘤中实现均匀分布是可能的。该模型对于专注于抗体与肿瘤细胞定位的一般生理方面的研究将具有重要价值，并且作为评估各种A33抗体构建体以及与其他治疗方法联合用于治疗结肠癌的指南至关重要。
