Significance of a new tumor-associated antigen, MK-1, for diagnosis and therapy of cancer

对于基于抗体的癌症治疗，人源单克隆抗体（mab）优于小鼠，小鼠/人嵌合或人源单克隆抗体，因为它对人的免疫原性最小，并且与人效应细胞有效协作。在本研究中，我们利用含有人类免疫球蛋白基因的基因工程小鼠（KM小鼠^<TM>）制备了针对泛癌抗原MK-1 （Ep-CAM）的人单克隆抗体。用重组MK-1免疫KM小鼠的脾脏细胞与P3-U1小鼠骨髓瘤细胞融合。在分析的44个抗mk -1克隆中，2个为IgG4克隆，其余为IgM克隆。虽然这两个IgG4克隆被认为识别相同的抗原决定因子或两个位置相近的决定因子，但它们的Vk区由不同的轻链基因编码，而它们的VH序列相同。两个IgG4克隆和一个IgM克隆在体外分别显示了对表达MK-1的细胞的抗体依赖细胞介导的细胞毒性和补体依赖细胞毒性，这表明这些针对MK-1及其v区基因生产的完全人源单克隆抗体可用于制备工程化抗体片段，可能用于基于抗体的癌症治疗。

For antibody-based therapy of cancer, monoclonal antibodies (mAbs) of human origin is superior to mouse, mouse/human chimeric or humanized mAbs, because of its minimum immunogenicity to human and its efficient collaboration with human effector cells. In the present study, we prepared human mAbs against a pan-carcinoma antigen, MK-1 (Ep-CAM), using a genetically engineered mouse (KM mouse^<TM>) that contains the human immunoglobulin genes. Spleen cells from KM mice immunized with recombinant MK-1 were fused with the P3-U1 mouse myeloma cells. Of 44 anti-MK-1 clones analyzed, two were of IgG4 and the others of IgM clones. Although the two IgG4 clones were suggested to recognize the same antigenic determinant or two closely located determinants, their Vk regions were encoded by different light-chain genes while their VH sequences were identical. The two IgG4 and one of the IgM clones tested revealed antibody-dependent cell-mediate cytotoxicity and complement-dependent cytotoxicity, respectively, against MK-1-expressing cells in vitro, suggesting that these fully human mAbs produced against MK-1 and their V-region genes, which are applicable for preparation of engineered antibody fragments, may be useful for antibody-based therapy of cancer.