阳离子超支化聚乙二醇介导的增加肿瘤细胞内放射性碘摄取和滞留的研究

Using radioiodine to perform tumor cell therapy, including thyroid cancer and non thyroid cancer which transferred by NIS gene,is the important study for targeting nuclear therapy. Although a lot of study have been done to improve the retention of radioiodine in cancer cells, including enhance the functional expression of NIS gene in tumor cell or decrease the exclusion of iodine from the tumor cell, at present, the issue of unsatisfied therapy results caused by short time retention of iodine in cell has not been resolved. This project tries to resolve this issue from another way to enhance the retention of iodine in tumor cell. By synthesis of low charge-density hyperbranched PEG (HA-PEGs), nano particle Ag has been delivered into thyroid tumor cells and to form AgI nano particles with iodine ion. AgI nano particle is insoluble and prevent the iodine ion from exclusion from cells.Meantime,since the HA-PEGs has the property of escaping from the endosome/lysosome through an effective "proton sponge", AgI particles in cells will not be exocytosed. If there is a small amount of AgI particles be exocytosed, it could be re-endocytosed into cells. Thus the iodine could be enhanced long term retention in thyroid cancer cells and the radiotherapy results could be got successfully. To non-thyroid tumor, since HA-PEGs exhibited high transfection efficiency of DNA, these tumor cells could have same enhanced long term retention of radioiodine in cell after NIS gene transferred.

利用放射性碘进行肿瘤治疗，包括甲状腺癌和外源性NIS基因导入后的非甲状腺癌，是核素治疗的重要研究内容。尽管有大量研究来增加肿瘤细胞内NIS的功能性表达或减少碘的流出，但仍未解决因放射性碘在肿瘤细胞内滞留时间短而严重影响疗效的问题。本课题试从另一途径来增加碘在肿瘤细胞内的滞留。利用制备的低含氮量的阳离子型超支化聚乙二醇（HA-PEGs）将银纳米颗粒导入甲状腺癌细胞内和碘离子反应，产生不溶的碘化银沉淀，使碘不能以离子的形式再流出细胞；同时，由于HA-PEGs的质子泵效应，能避开细胞内"吞噬小体-溶酶体途径，碘化银颗粒将不被细胞快速外吐，即使有部分被外吐，也将被细胞再摄入。因此，碘可长期滞留在细胞内，对甲状腺癌细胞产生持续的放射治疗效果。对非甲状腺癌细胞，由HA-PEGs携带NIS基因转染细胞并表达后，肿瘤细胞具有摄碘能力，如甲状腺癌细胞一样，同样能加强肿瘤细胞内碘的滞留。

背景：在放射性碘治疗具有摄碘功能的肿瘤细胞过程中，摄碘率不足或下降是影响碘治疗肿瘤的最主要原因。尽管有不少方法用来增加肿瘤细胞中的碘滞留，但效果甚微。究其原因可能是细胞层面上的碘的摄取和流出为一动态平衡，即“肿瘤细胞摄取碘越多，碘流出细胞也越快”的现象。因此寻找另一种途径来增加碘在细胞内的滞留，即让摄入到细胞内的碘和其它离子发生化学反应，产生不溶性沉淀，使放射性碘不能以离子的形式再流出细胞，碘将滞留在细胞内，对细胞产生持续的放射治疗效果。.主要研究内容：1.合成碘化的可携带银离子的高分子化合物I-PEI-Ag (AgCl/ CH3CO-PEI-PhOH-I)；2，转染NIS基因于失分化的分化型甲状腺癌细胞株FTC-133后NIS蛋白功能的确定；3，I-PEI-Ag对提高细胞内碘滞留的作用研究；4，I-PEI-Ag对荷甲状腺癌裸鼠模型中肿瘤碘滞留的作用研究..重要结果及数据：1，所合成的PEI-Ag大小DLS粒径为58nm左右；TEM下可看到包裹着CH3CO-PEI-PhOH的AgCl纳米颗粒粒径均一；2，碘化CH3CO-PEI-PhOH后经IMS 测得碘离子浓度为0.8mg/L（CH3CO-PEI-PhOH浓度为10mg/L）；3，失分化的FTC-133细胞株在与转染了NIS基因后其30分钟的125-碘摄碘率从1500cpm 增加到了4000cpm；4， FTC-133-NIS在I-PEI-Ag作用下，其细胞内的125-碘滞留率在5、10、30和60分钟与均有明显增加，在15min时可减少细胞内的碘流出12%, 在60min时，细胞内的碘滞留增加30%。.结论：纳米化银离子能够帮助放射性碘在摄碘细胞中的碘的滞留，有助于肿瘤细胞的放射性治疗。