Ichiki S, Kuroki M, Matsunaga A, Arakawa F, Okamoto N, Matsuoka Y
Jpn J Cancer Res. 1986 Oct;77(10):1005-11.
Antigenic variations of carcinoembryonic antigens (CEAs) produced by 8 human tumor cell lines of various organ origins--4 derived from colonic, one from gastric, one from pancreatic, and 2 from lung cancers--were investigated on the basis of reactivity with several monoclonal antibodies recognizing either the peptide or the carbohydrate moiety of the CEA molecule by using a sandwich-type solid-phase radioimmunoassay (RIA). CEAs from all the cell lines revealed nearly uniform reactivities with the monoclonal antibodies recognizing the peptide epitopes, and no difference was observed between the reactivities of CEAs released into culture medium (m-CEAs) and of those extracted from cells (c-CEAs). On the other hand, with each of 4 monoclonal antibodies recognizing the carbohydrate epitopes, the reactivities of CEAs were found to be highly variable from one cell line to another, and a marked difference was detected between the reactivities of m-CEA and of c-CEA in every cell line. In general, c-CEA reacted much more strongly than m-CEA with these antibodies. The reactivities of some of the CEAs with 2 out of 4 antibodies to sugar epitopes increased significantly after treatment of CEAs with neuraminidase. These results suggest that distinct structural changes in the carbohydrate moiety may occur during the releasing process of CEA from cells, and that, in some cases, some epitopes may be masked by attachment of sialic acid residues.
利用夹心型固相放射免疫测定法（RIA），基于与几种识别癌胚抗原（CEA）分子肽段或碳水化合物部分的单克隆抗体的反应性，研究了8种源自不同器官的人类肿瘤细胞系所产生的CEA的抗原变异情况，这8种细胞系中4种源自结肠，1种源自胃，1种源自胰腺，2种源自肺癌。所有细胞系的CEA与识别肽表位的单克隆抗体显示出几乎一致的反应性，并且释放到培养基中的CEA（m-CEA）与从细胞中提取的CEA（c-CEA）的反应性之间未观察到差异。另一方面，对于4种识别碳水化合物表位的单克隆抗体中的每一种，发现不同细胞系的CEA反应性差异很大，并且在每个细胞系中m-CEA和c-CEA的反应性之间检测到明显差异。一般来说，c-CEA与这些抗体的反应比m-CEA强烈得多。用神经氨酸酶处理CEA后，一些CEA与4种糖表位抗体中的2种的反应性显著增加。这些结果表明，在CEA从细胞释放的过程中，碳水化合物部分可能发生明显的结构变化，并且在某些情况下，一些表位可能被唾液酸残基的附着所掩盖。
