核素碘131治疗耐药是临床核医学面临的难题。发表于Life Sciences的本研究前期工作证实midkine（MK）过表达与分化型甲状腺癌（DTC）恶性程度正相关：MK测定可鉴别甲状腺结节良恶性、也可判断DTC是否存在转移灶。随DTC恶性程度的增高会出现碘131治疗耐药。本研究拟用小干扰RNA和MK抗体抑制癌细胞MK，通过转染表达MK质粒和给予MK重组蛋白增强癌细胞MK；做存活分析实验；用Western法检测MK、MK受体、MAPK和PI3K通路关键蛋白及凋亡关键蛋白变化；从基因水平（PCR法）和蛋白水平（Western法）检测碘处理关键蛋白和甲状腺转录因子变化；用体外细胞水平摄碘131实验和荷瘤裸鼠模型活体显像研究抑制MK对癌细胞摄碘131能力的影响；观测体内实验疗效、明确联合碘131和抑制MK与单独用药的区别。临床研究明确血MK水平对DTC碘131治疗疗效、预后和病情监测的价值。

Radioactive isotope iodine 131 therapeutic resistance is a very serious problem for clinical nuclear medicine. In our preliminary work, which is published in Life Sciences, we prove that over-expression of midkine (MK) is positively related with the malignant degree of differentiated thyroid cancer (DTC). MK measurement can be used for differential diagnosis between benign and malignant thyroid nodules, and can also be used for the prediction of metastases in DTC. Iodine 131 therapeutic resistance happens when DTC malignant degree increases. In this research, we use small interference RNA and MK antibody to suppress MK in cancer cells, and we use MK-gene carrying plasmids and MK recombinant protein to over-express or enhance MK in cancer cells. Then cell survival assay is performed. By Western blot, the changes of MK, MK receptors, key proteins in MAPK and PI3K pathways, and key apoptotic proteins are assessed. The changes of iodine-processing proteins and thyroid transcription factors are analyzed by real-time RT-PCR at mRNA level and by Western blot at protein level. The changes of iodine 131 uptake ability influenced by MK suppression are determined by iodine 131 uptake experiment at cellular level and tumor-bearing nude mice models in vivo imaging experiment. In vivo therapeutic effects are to be monitored in nude mice experiment in order to determine the difference between combining iodine 131 with MK suppression and any mono-therapy. Clinical study will determine the values of serum MK for iodine 131 therapeutic effects, prognosis and surveillance of DTC.