Targetted immunotherapy with enzyme-labeled antibodies

癌胚抗原（CEA）仅存在于正常结肠柱状上皮细胞的刷状边缘，而存在于结肠癌细胞的表面。通过利用转化上皮细胞表面抗原分布的变化，我们致力于开发一种从体内消除这种肿瘤细胞的方法。作为初步实验，用葡萄糖氧化酶标记的兔抗人CEA IgG注射人CEA生成瘤裸鼠。抗体注射后静脉注射NaI。这种方法的原理是，注射的酶标记抗体会在产生CEA的肿瘤细胞表面沉积并产生过氧化氢，过氧化氢会氧化质膜并使碘离子渗透，碘会杀死细胞。结果发现肿瘤大小明显减小，但小鼠出现胰岛素休克样的血糖升高，并在肾小球基底膜上沉积了cea -酶标记的抗体免疫复合物。为了避免这些问题，本研究用半乳糖氧化酶代替葡萄糖氧化酶，并寻找另一种细胞表面抗原，该抗原在细胞转化时随CEA的分布而改变，但不溶于血浆。为了获得抗原，建立了一种从结肠上皮细胞中分离刷缘抗原的新方法，并从分离的刷缘中鉴定出了几个分子量为几千的刷缘特异性抗原。利用细胞表面抗原在正常上皮细胞上无法进入循环，但在转化后可作为免疫靶向治疗的靶点，不需要肿瘤特异性抗原，使用过氧化氢标记抗体应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.