新型RGD肽核素纳米载体的实验研究

Non-thyroid cancers could uptake of 131I (iodine) following transfected with hNIS gene, but there were problems that gene transfer was untargeted and short 131I retention time can't kill tumor cells effectively. Our previous studies showed the target-promoter and cotransfected hTPO gene could achieve tumor-specific transfection of the hNIS gene and limited improve the intracellular retention time of 131I， but could not improve the cell kill radio. At the same time ,cyclic arginyl-glycyl-aspartic acid (RGD) nanoparticles can achieve the targeted tumor therapy effectively and has drug sustained-release effect. Based on these results, we plan to use RGD nanoparticles encapsulated 131I complexes, construct a new RGD radionuclide nanoparticles， do cell experiments and animal experiments in tumor cells. Meantime, we will discuss if the nanoparticles carrying hNIS gene can effectively inhibit the intracellular 131I outflow. The new model of RGD nanoparticles is the innovation of old RGD radionuclide nanoparticles. The research had opened up new realms for the targeting nanotechnology in nuclear medicine and tumor treatment field, explored the possibility of nanoparticles used in tumor specific radionuclide imaging.

非甲状腺来源肿瘤转染NIS基因后可以摄取131I（碘），但存在基因转染非靶向性和131I在细胞内存留时间过短不能有效杀死肿瘤的问题。课题组前期研究证明：纳米载体能有效的实现肿瘤靶向性治疗并具有药物缓释作用，使用靶向性启动子和共转染hTPO基因可以实现NIS靶向性表达并有限的提高131I胞内滞留时间，却不能提高肿瘤细胞杀伤率。本研究在此基础上，拟使用纳米微粒包裹131I并以RGD肽为位点实现靶向性治疗，构建一个新型RGD靶向性核素纳米载体，对相应肿瘤细胞进行细胞实验和动物实验，同时探讨纳米载体共装载NIS基因后是否能有效抑制胞内131I外流。新型RGD纳米载体靶向性强，包封率高，缓释效果好，是对以往RGD肽纳米核素载体的创新。本研究开拓了靶向性纳米技术在核医学肿瘤治疗领域的新思路，探索了其应用于肿瘤特异性核素显像的可能性。

本研究在非小细胞肺癌模型中研讨了131I-RGD-BSA-PCL 的内吞生物效应及治疗效果。在RGD过表达的NCI-H460肺癌细胞系中通过共聚焦显微镜研究细胞的靶向性摄取及胞吞。使用流式细胞仪检测细胞凋亡。在非小细胞肺癌动物模型中观察裸鼠经过131I-RGD-BSA-PCL 治疗后的肿瘤体积及体重变化，并进行了免疫组化分析及 SPECT/CT 显像。共聚焦显微镜显示肿瘤细胞在孵育1小时后即观察到明显胞内摄取，8小时后仍未消失。动物实验的131I-BSA-PCL 摄取实验显示在注射药物24h和72h后肿瘤部位组织分布为11.06±2.15%ID/g和3.83±0.87%ID/g，组织摄取率为显著高于其余组织；131I-RGD-BSA-PCL 为 39.49±6.06%ID/g 和6.97±1.43%ID/g，明显高于131I-BSA-PCL。在动物实验中131I-RGD-BSA-PCL 组的裸鼠在实验结束时体重仅降低 3.5% ，而对照组降低21.5% 。131I-RGD-BSA-PCL 组的生存期为27天。RGD-BSA-PCL 表现中极佳的胞内摄取效果，而131I-RGD-BSA-PCL 可以在非小细胞肺癌动物模型中作为显像药物和靶向性治疗药物。