靶向膀胱癌细胞内突变p53的跨膜重组抗体研究

Traditional antibody therapy did not achieve treatment effects against intracellular mutant proteins, which are abundant、specific and high immunogenic in cancer, duo to low interlazation rate. Our previous study has established a new technology platform to improve antibody endocytosis efficiency (by fusing cell-penetrating peptides to its Fc terminal), and selected Anti-mut-p53 broad specific monoclonal antibodies. However, whether the recombined Anti-mut-p53 could degrade inner mut-p53 is not clear. The present study includude : 1)optimizing strategies to improve recombined Anti-mut-p53 antibodies internalization rate; 2) evaluating the possibility of if recombined antibodies could bind to the inner mut-p53 and degradate it by stimulating TRIM21 dependent intracellular immune; 3) testing wether recombined antibody therapy could stimulate in vivo antitumor immunity in the constructed murine orthotopic bladder cancer model. This study will shed light on the mechanism of mut-p53 degradation through recombined antibody therapy, providing new strategy for intracellular tumor targets design.

肿瘤细胞内有大量特异度高、免疫原性强的突变蛋白，但以其为靶点设计的传统抗体药物治疗效果有限，因为跨膜效率低。我们前期已建立了提高抗体入胞效率的技术平台（通过在其Fc末端融合穿膜肽），并且制备了在肿瘤中广泛存在的突变p53（mut-p53）广谱特异性单抗，但融合有穿膜肽的重组抗体降解mut-p53的效果和机制还有待研究。本项目拟:1）构建融合有穿膜肽的可以高效跨膜的mut-p53重组抗体；2）在膀胱癌细胞模型中，研究重组蛋白降解mut-p53的能力，以及是否激活胞内Fc受体（TRIM21）介导的胞内免疫；3）在已构建的小鼠原位膀胱癌模型中，评估该重组抗体是否可以激发体内抗肿瘤免疫。该项目的实施有望阐明重组抗体降解mut-p53的效果及分子机制，为肿瘤胞内靶标的开发提供新思路。

肿瘤细胞内P53突变广泛存在，驱动肿瘤的发生发展，然而靶向突变P53蛋白的小分子特异性差毒副作用强，传统抗体跨膜效率极低因而未能实现临床转化。本项目主要研究内容为靶向突变P53抗体的开发及机制研究，首先筛选得到了特异识别突变P53蛋白的单克隆抗体，该抗体与野生型P53不反应；进一步通过对抗体的分子改造，在其Fc端融合具有穿膜能力的穿膜肽，实现了重组抗体高效进入肿瘤细胞内并与突变P53结合导致其降解；研究发现该过程通过激活TRIM21介导的胞内免疫途径实现，最终导致突变P53降解；进而在小鼠膀胱癌模型中发现其可以激活体内抗肿瘤免疫，提高抗肿瘤治疗效果。本项目阐述了重组抗体靶向降解突变P53的分子机制，并为肿瘤细胞内突变蛋白的抗体药开发提供了新策略。