半乳糖结合位点封闭免疫毒素的研制及其杀伤活性

Preparation of an Immunotoxin with the Galactose-Binding Sites Blocked and Its Specific Cytotoxic Effect

作者报道B链半乳糖结合位点封闭的蓖麻毒素-胃癌单克隆抗体MGb_2结合物的制备及其细胞毒特征。首先将引入碘乙酰基团的毒素与引入巯基的抗体反应,得到的结合物通过琼脂糖亲和层析柱除去仍保留半乳糖结合能力的部分。细胞毒性试验结果表明,结合物对肿瘤靶细胞具有较强的选择性杀伤作用,在1.0×10^(-11)mol/L水平,对人胃癌细胞KATOⅢ的杀伤率为46％,优于MGb_2-蓖麻毒素A链结台物(12％),而对非靶细胞作用很弱,在1.0×10^(-9)mol/L水平对正常人胚肺细胞SL_7杀伤率仅为42％,无需半乳糖拮抗。

In the present study, a specific cytotoxic agent was prepared by linking intact ricin to a monoclonal antibody, MGb2, against gastric cancer in a manner producing hidance to the galactose-binding sites on the B-chain of the toxin. The conjugate was syntliesised by reaction of iodoacetylated ricin with thiolated antibody and the components of conjugate with reduced galactose-binding capacity were separated by affinity chromatography on Sepharose, The McAb-ricin conjugate showed highly selective cytotoxicity upon target cells (human gastric cancer cell line KATOⅢ). At the concentration of 10-11, mol/L 46% of tumor cells could be killed by the conjugate. While the conjugate had only a little effect upon non-target cells (normal human embryonic lung cell line SL7). The results suggested that the selective cytotoxicity of conjugate be mediated by antibody.