Targetted immunotherapy with enzyme-labeled antibodies

癌胚抗原(CEA)仅见于正常结肠柱状上皮细胞的刷状缘处，而在结肠癌细胞表面广泛分布。通过利用转化的上皮细胞表面抗原分布的变化，我们承诺开发一种方法来消除体内的这种肿瘤细胞。作为初步实验，将葡萄糖氧化酶标记的兔抗人CEA抗体注射到荷人CEA荷瘤裸鼠体内。抗体注射后进行静脉注射。在注射NaI时。这种方法的理由是，注射的酶标记抗体将沉积在产生CEA的肿瘤细胞表面并产生过氧化氢，过氧化氢将氧化质膜，使其对碘离子具有渗透性，而碘将杀死细胞。结果发现，肿瘤体积明显缩小，但小鼠出现胰岛素休克样高血糖，肾小球基底膜上有CEA-酶标记抗体免疫复合物沉积。为了解决这一问题，本研究用半乳糖氧化酶代替葡萄糖氧化酶，并寻找了另一种细胞表面抗原，当细胞转化时，其分布会改变为CEA，但不溶于血浆。为了获得该抗原，建立了一种从结肠上皮细胞中分离刷状缘的新方法，并从分离的刷状缘中鉴定出几种相对分子质量为数千的刷状缘特异性抗原。利用细胞表面抗原作为免疫靶向治疗的靶点，不需要肿瘤特异性抗原，使用双氧水标记的抗体可以避免毒素标记抗体的全身副作用。

Carcinoembryonic antigen (CEA) is found only at the brush border of normal colonic columnar epithelial cells,but is found all around the surface of colonic cancer cells. By taking an advantage of the change on the distribution of antigens on the surface of transformed epithelial cells, we undertook to develop a method to eliminate such neoplastic cells from the body. As a preliminary experiment, nude mice bearing human CEA producing tumor were injected with rabbit anti-human CEA IgG labeled with glucose oxidase. The injection of antibody was following by an i.v. in jection of NaI. The rational for this approach was that the injected enzyme-labeled antibody will be deposited on the surface of CEA producing tumor cells and produces hydrogen peroxide, the hydrogen peroxide will oxidize the plasma membrane and become permeable to iodine ion and the iodine will kill the cells. It was found that the size of tumor was reduced significantly, but the mice underwent an insulin shock like hepoglycemia and CEA-enzyme labeled antibody immune complex were deposited on the glomerular basement membrance. To circumvent the problems, with this investigation, galactose oxidase was used in place of glucose oxidase and another cell surface antigen of which distribution will change as the CEA when the cell are transformed, but is insoluble in the plasma were sought. To obtain the antigen, a new isolation method for the brush border from colonic epithelial cells was developed, and from the isolated brush border, several brush border specific antigens with molecular weight of several thousand were identified. The utilization of cell surface antigens which are inaccessible to the circulation on normal epithelial cells, but become accessible upon transformation as the targets of immuno-targeted therpy does not require tumor specific antigens and the use of hydrogen peroxide labeled antibodies should avoid the systemic side effect of toxin labeled antibodies.