人肺癌单抗LC-1与天花粉毒蛋白(TCS)结合物的抗肿瘤作用

人肺癌单克隆抗体LC-1为IgM抗体。经ABC染色法证实它与人肺癌组织产生较高的阳性反应,并在人肺腺癌裸小鼠移植癌(LAX-83)中显像定位明显、清晰。本文报道LC-1与天花粉毒蛋白(TCS)经化学修饰,交联生成的结合物对LAX-83的抗肿癌效果。结合物LC-1.TCS的克分子比为1:3。用裸小鼠肾包膜检测法评价疗效,在裸小鼠双侧肾包膜下接种10～15omu(10omu=1mm)大小的癌块,于种后2d开始治疗,每天腹腔给药1次,连续给药7d,于停药后隔日解剖,测量瘤径,计算各组织块增殖大小,与对照组比较,求出各给药组肿瘤抑制率,经统计学处理后评价疗效。实验结果表明,LC-1或TCS单独治疗组以及两者混合物组对LAX-83均无明显疗效。

天花粉毒蛋白免疫毒素对靶细胞凋亡的作用

借化学交联方法将一种自然存在的植物单链毒素——天花粉毒蛋白(TCS)引至胃癌单抗MGb_2分子上,制得抗胃癌天花粉毒蛋白交联物MGb_2—TCS。以示踪技术对MGb_2—TCS在临床人胃癌实体瘤细胞中的内化及其杀伤靶细胞的死亡模式进行了探讨,同时还观察了ras癌基因的活化表达与MGb_2—TCS靶细胞杀伤效应之间的关系。结果显示,MGb_2—TCS以胞膜凹陷方式入胞后,绝大部分由管泡结构输送至多泡小体,然后再由多泡小体输送至溶酶体,并在那里消化降解,仅见少量的MGb_2-TCS自管泡或多泡小体阶段易位至胞质作用位点。超微形态学观察发现,MGb_2-TCS所致的靶细胞损伤出现细胞凋亡的特征性形态学改变。ras癌基因产物p^(21)蛋白的定位进一步显示,MGb_2—TCS损伤的细胞P^(21)多为阴性,而P^(21)阳性的细胞则不受MGb_2—TCS的影响。MGb_2—TCS对胃癌细胞的杀伤是通过启动细胞凋亡机制来实现的。尽管MGb_2—TCS内化后易位至胞质作用位点是MGb_2—TCS杀伤靶细胞的必要条件,但MGb_2-TCS对靶细胞的杀灭尚可能与靶细胞ras癌基因活化表达状态具有一定的关联。

Prediction of antigenic determinants of trichosanthin by molecular modeling

The antigenic determinants of trichosanthin were predicted by molecular modeling. First, the threedimensional structure model of the antigen-binding fragment of anti-trichosanthin immunoglobulin E was built on the basis of its amino-acid sequence and the known three-dimensional structure of an antibody with similar sequence. Secondly, the preferable antigen-antibody interactions were obtained based on the known three-dimensional structure of trichosanthin and of the hypervariable regions of anti-trichosanthin immunoglobulin E. Two regions in the molecular surface of trichosanthin were found to form extensive interactions with the hypervariable regions of the antibody and have been predicted to be the possible antigenic determinants: one is composed of two polypeptide segments, Ile201-Glu210 and Ile225-Asp229, which are close to each other in the three-dimensional structure; and the other is the segment Lys173-Thr178. The former region seems to be the more reasonable antigenic determinant than the latter one.