MiR-107靶向TDG调节乳头状甲状腺癌放射性碘耐受机制研究

131I ablation for removing residual lesion after surgery is the primary therapy for patients who suffer from papillary thyroid cancer. Some 25%~50% of PTC will become radioactive iodine resistant/refractory (RAIR). The mechanisms however, remain largely to be elucidated. The previously work performed by appliciant with serum miRNA array have found that miR-107 was significant higher in 3 PTC patients after RAIR appeared, interfering the miR-107 expression can downregulate the iodine handling proteins expression. Further work have uncovered TDG as a new putative target of miR-107. We also found that the TDG has lower expression in the tissue samples derived from RAIR-PTC patients through Bioplex luminary chip, and the iodine handling proteins were expressed lower among these patients’ samples. Therefore we proposed a hypothesis that miR-107 would be involved in RAIR-PTC by targeting TDG and affecting 131I uptake and iodine handling proteins, TDG may modulate the demethylation of iodine-handling protein, minewhile it can also interact with thryoid specific factor, transcriptional factor or trans-coactivator to affect the signal pathway in thyroid cancer. We want to construct miR-107 overexpression and downregulation models as well as 131I-tolerant PTC cell lines to systemetic investigate the effect of miR-107 on 131I uptake and iodine-handling proteins to further address the mechanisms of miR-107 regulating TDG involve in RAIR-DTC.

乳头状甲状腺癌（PTC)术后行131I内放射是其首选治疗，但25%～50%以上病人出现放射性碘耐受（RAIR）。目前PTC发生RAIR机制尚不清楚。申请人前期实验通过血清microRNA芯片对PTC患者发生RAIR的前后血清中miRs表达变化进行筛查，发现miR-107表达异常增高，干扰miR-107表达能显著提高碘处理蛋白的表达，并确定了miR-107的靶基因TDG。Bio-Plex液相悬浮芯片技术发现RAIR-PTC中TDG表达下调，碘处理相关蛋白表达下降。据此提出假说：RAIR-PTC中异常高表达的miR-107可导致TDG表达下调，导致其与转录因子和转录共激活因子的相互作用受阻，甲状腺特异因子以及甲状腺碘代谢基因去甲基化，及甲状腺信号通路的异常激活等。我们拟通过miR-107功能性获得或缺失系统探讨miR-107调控TDG参与RAIR的发生机制。

项目背景：25~50%的乳头状甲状腺癌（PTC）术后病人出现放射性碘耐受（RAIR），但是PTC的RAIR机制尚不清楚。项目负责人在RAIR-PTC病人的血清中发现miR107的异常升高，而干扰miR-107的表达能显著提高碘处理蛋白的表达。新近的研究提示长链非编码RNA（long noncoding RNAs, lncRNAs）在许多疾病中扮演着重要的角色。通过生物信息学方法预测了HOTAIRM1为miR-107的上游基因，TDG为miR-107的下游基因。在这些基础上，开展了围绕miR-107靶向TDG的上下游调节机制参与RAIR在PTC中的发生的研究。.主要研究内容：本项目主要对HOTAIRM1/miR-107/TDG轴调节PTC细胞株的细胞生理学的影响等内容进行了研究。完成了miR-107对TDG的靶向性研究，HOTAIRM1对miR-107的靶向性研究的验证。通过体外和体内实验，验证了HOTAIRM1/miR-107/TDG轴在PTC细胞的不良进展过程中的作用。并且，在临床样本中对HOTAIRM1/miR-107/TDG轴中的关键调节因子进行了表达水平的验证。此外，本项目的研究内容也涉及了其他的RAIR相关的研究工作。.重要结果：通过一系列体内体外实验，HOTAIRM1 被证实在PTC组织中显著下调，低表达的HOTAIRM1与淋巴结转移相关。并且体外实验发现HOTAIRM1抑制细胞增殖和促进细胞凋亡，在小鼠移植瘤模型中抑制肿瘤发展。另外，过表达HOTAIRM1抑制PTC细胞的迁移和侵袭能力。机制实验显示HOTAIRM1扮演着miR-107的ceRNA的角色，继而对下游基因进行调控，最终导致了胸腺嘧啶糖苷酶（thymine DNA glycosylase，TDG）的下调。总之，HOTAIRM1通过HOTAIRM1/miR-107/TDG轴抑制PTC细胞增殖和促进细胞凋亡。而HOTAIRM1的表达降低可能会促进不良结局的发生。.此外，项目负责人通过其他相关研究还发现野生型P53在ATC细胞株中能够激活NIS表达，当P53基因突变后，NIS表达下调。而miR-107参与的Wnt/β-catenin信号通路受到Tiam1调节，通过调节EMT促进甲状腺癌转移。这些结果都为研究PTC术后碘耐受的发生机子提供了更多的证据。