Fogler W E, Klinger M R, Abraham K G, Gottlinger H G, Riethmuller G, Daddona P E
Department of Immunobiology R & D, Centocor, Malvern, Pennsylvania 19355.
Cancer Res. 1988 Nov 15;48(22):6303-8.
The purpose of this report was to investigate the binding specificities and ability to generate antibody dependent cell mediated cytotoxicity (ADCC) or antibody dependent complement mediated cytotoxicity of three novel monoclonal antibodies (mAbs), designated M74, M77, and M79, raised against the colorectal carcinoma antigen 17-1A. As determined by indirect radioimmunoassay, all three mAbs, as well as mAb 17-1A, bound to a similar extent to adherent cultures of the human colon carcinoma cell line, HT-29. Scatchard analysis of direct binding data for mAbs 17-1A, M74, M77, and M79 to HT-29 cells demonstrated equivalent association constants (7.54-9.77 X 10(7) liters/mol) and molecules bound per cell (2.15-2.69 X 10(5)). In contrast to mAbs M77 and M79, mAb M74 inhibited the binding of 125I-labeled mAb 17-1A to HT-29 cells. Similar to mAb 17-1A, incubation of human lymphocytes and blood monocytes with mAbs M74, M77, or M79 generated ADCC activity against HT-29 colon carcinoma cells. Various combinations of noncompeting mAbs to the 17-1A antigen (17-1A and M74; M77 and M79; M74 and either M77 or M79) but not competing mAbs (17-1A and M74; M77 and M79) resulted in a heightened level of ADCC activity. Under optimum conditions (saturation of antigenic sites with mAb), ADCC generated by the combination of noncompeting mAbs to the 17-1A antigen was additive to the activity seen with the respective mAbs alone. Under suboptimum conditions, the combination of noncompeting mAbs to the 17-1A antigen resulted in tumor cell cytotoxicity which was synergistic to the lysis obtained with the respective mAbs alone. No mAb used alone was able to generate antibody dependent complement mediated cytotoxicity against a panel of 17-1A positive colon carcinoma cells. Similarly, no antibody dependent complement mediated cytotoxicity activity was obtained with the combination of competing mAbs to the 17-1A antigen. However, HT-29 cells treated with noncompeting mAbs to the 17-1A antigen antigen were rendered susceptible to lysis by human complement. We conclude that the combination of mAbs recognizing different epitopes on the same tumor antigen could have important implications for the passive immunotherapy of cancer.
本报告的目的是研究三种新型单克隆抗体（mAb），即针对结肠直肠癌抗原17-1A产生的M74、M77和M79的结合特异性以及产生抗体依赖性细胞介导的细胞毒性（ADCC）或抗体依赖性补体介导的细胞毒性的能力。通过间接放射免疫测定法确定，所有这三种单克隆抗体以及单克隆抗体17-1A与人类结肠癌细胞系HT-29的贴壁培养物的结合程度相似。对单克隆抗体17-1A、M74、M77和M79与HT-29细胞的直接结合数据进行Scatchard分析，结果显示其缔合常数相当（7.54 - 9.77×10⁷升/摩尔），且每个细胞结合的分子数为（2.15 - 2.69×10⁵）。与单克隆抗体M77和M79不同，单克隆抗体M74抑制¹²⁵I标记的单克隆抗体17-1A与HT-29细胞的结合。与单克隆抗体17-1A相似，将人淋巴细胞和血液单核细胞与单克隆抗体M74、M77或M79一起孵育可产生针对HT-29结肠癌细胞的ADCC活性。针对17-1A抗原的非竞争性单克隆抗体的各种组合（17-1A和M74；M77和M79；M74与M77或M79中的任一种）而非竞争性单克隆抗体（17-1A和M74；M77和M79）可导致ADCC活性水平升高。在最佳条件下（用单克隆抗体使抗原位点饱和），由针对17-1A抗原的非竞争性单克隆抗体组合产生的ADCC与单独使用各自的单克隆抗体时所观察到的活性具有加和性。在次优条件下，针对17-1A抗原的非竞争性单克隆抗体组合导致肿瘤细胞毒性，这与单独使用各自的单克隆抗体所获得的裂解作用具有协同性。单独使用的任何一种单克隆抗体均无法对一组17-1A阳性结肠癌细胞产生抗体依赖性补体介导的细胞毒性。同样，针对17-1A抗原的竞争性单克隆抗体组合也未获得抗体依赖性补体介导的细胞毒性活性。然而，用针对17-1A抗原的非竞争性单克隆抗体处理的HT-29细胞易被人补体裂解。我们得出结论，识别同一肿瘤抗原上不同表位的单克隆抗体组合可能对癌症的被动免疫治疗具有重要意义。
