碘131内照射是治疗分化型甲状腺癌的重要方法，但治疗过程中癌细胞容易发生“失分化”现象而丧失摄碘功能，降低疗效，出现恶化和复发。设想如能将碘131靶向转入癌细胞的同时，控制性启动自杀基因表达，可望双重损伤癌细胞。由此，本项目拟构建一种壳聚糖纳米微粒，其外包被甲状腺癌细胞特异性单抗，其内包裹碘131和E9（放射敏感性增强子）及TGp（甲状腺球蛋白启动子）串连组成的“基因开关”调控的、表达双自杀基因CDglyTK的质粒载体。此纳米微粒可靶向转染甲状腺癌细胞，一方面使碘131进入分化型或失分化型甲状腺癌细胞中，发挥内照射作用；另一方面，碘131照射可增强癌细胞中双自杀基因（CDglyTK）在TGp驱动下的表达。于是，碘131的内放射联合自杀基因的细胞毒性作用，可有效损伤甲状腺癌细胞，但对甲状腺周围正常组织无影响，以实现针对该肿瘤的双重靶向治疗，并进一步探讨其分子机制。

Differentiated thyroid cancer (DTC) is not sensitive to the chemotherapy and radiotherapy. Iodine-131 radiation therapy is usally used for treatment of DTC. However, the curative effect might be reduced because of the "dedifferentiation" phenomenon that cancer cells failed to uptake iodine. Thus, the effecacy of Iodine-131 was decreased, leading to deterioration and relapse of the cancer. We hypothized that transfection with both iodine-131 and suicide genes (CDglyTK) into cancer cells might facilitate the cell double damage. we aim to construct a namo-carrier conprising suicide genes driven by e9 (the radiosensitivity enhancer) and TGp (thyroid cancer-specific promoter), as well as iodine 131 that might induce the expression of CDglyTK. The vector will be wrapped up by FTC-133 antibodies, which might effectively and specifically kill the cancer cells in vitro and in vivo.