HORMAD2甲基化对甲状腺癌细胞碘代谢机制的研究

Thyroid cancer is the most common endocrine maliganant tumor and the majority is differentiated thyroid cancer (DTC). However, some of thyroid cancer lose their ability to concentrate radioiodine, which indicates a poor prognosis. Although oncogenic mutations in BRAF, TERT promoter and TP53 are associated with an increased propensity for induction of dedifferentiation, the role of genetic and epigenetic aberrations and their effects on important intracellular signaling pathways is not yet fully elucidated. In our previous work, we found that HORMAD2 methylation may be involved in the initiation and progression of thyroid cancer. Combined with the latest research results, we hypothesized that HORMAD2 methylation may play an important role in the process of thyroid cancer dedifferentiation. In this study, a series of studies including methylation degree of HORMAD2 will be conducted so as to find out the effect of HORMAD2 methylation on its silencing and dedifferentiation of thyroid cancer. The correlation between HORMAD2 and BRAF mutation will also be studied。Improvement of iodine uptake ability of cells will be observed through demethylation treatment.Finally, the molecular mechanism of dedifferentiation of differentiated thyroid cancer will be described from a new perspective, and an effective method for its redifferentiation will be explored.

甲状腺癌是目前世界上发病率最高的内分泌肿物，其中分化型甲状腺癌最为常见。分化型甲状腺癌失分化而出现摄碘功能障碍是降低131I碘疗效果差，并导致其预后变差的主要原因。目前对失分化甲状腺癌的研究主要针对BRAF、TERT启动子及TP53基因的突变，而这些研究尚未能有效揭示引起失分化的原因及其细胞内重要信号通路。课题组在前期工作中发现HORMAD2甲基化可能涉及甲状腺癌的启动和进展，结合国内外最新研究成果，我们假设HORMAD2甲基化可能在甲状腺癌失分化过程中扮演重要的角色。本研究从通过HORMAD2甲基化程度测定，进行一系列研究，以期发现HORMAD2甲基化致使其沉默及对甲状腺癌失分化的影响，并深入研究HORMAD2与BRAF突变之间的相互关系，同时通过去甲基化治疗，观察细胞摄碘能力改善情况。最终，从新的角度阐述分化型甲状腺癌失分化的分子机制，并探寻有效的使其再分化的方法。

目的：分化型甲状腺癌失分化而出现摄碘功能障碍是降低131I碘疗，并导致其预后变差的主要原因。目前对失分化甲状腺癌的研究主要针对BRAF、TERT启动子及RET基因等的突变，而这些研究尚未能有效揭示引起失分化的原因及其细胞内重要信号通路。本研究拟从新的角度阐述分化型甲状腺癌失分化的分子机制，并探寻有效的使其再分化的方法。方法：本研究通过HORMAD2甲基化程度测定及碘代谢相关基因的表达进行分析；外泌体circ-007293对调控PTC失分化的机制进行初探。结果：①甲状腺癌组织中HORMAD2基因甲基化阳性率高于癌旁组织与正常组织；②甲状腺癌标本中HORMAD2基因mRNA表达量与甲状腺癌患者临床分期、淋巴结转移情况有相关性：临床分期III+IV组甲状腺癌HORMAD2表达明显低于I+II期组，淋巴结转移组HORMAD2表达明显低于淋巴结无转移组；③甲状腺癌组织HORMAD2基因的甲基化水平与NIS表达水平呈负相关，HORMAD2基因mRNA表达量与NIS表达水平呈正相关；④不同5-Azacytidine剂量组细胞HORMAD2甲基化程度与NIS表达差异分析提示10.0 umol/L处理组NIS表达明显高于其他组；⑤外泌体circ-007293通过抑制miR-653-5p活性而增加PTC细胞中PAX6的表达，促进肿瘤细胞增殖、转移和上皮-间质转化。结论：①HORMAD2甲基化致使其沉默，影响甲状腺癌碘代谢；②去甲基化治疗可提高HORMAD2表达，且浓度10.0 umol/L时可改善细胞摄碘能力；③外泌体circ-007293有望成为检测PTC失分化的新型生物标志物。