基于miR-145/ETS2/c-Myc的调控探索TERT启动子突变介导分化型甲状腺癌碘抵抗的机制

Radioiodine-refractory differentiated thyroid cancer (RAIR-DTC) is currently a major challenge in the therapy of thyroid cancer. Our previous study revealed that TERT promoter mutation was closely associated with radioiodine non-avid status of distant metastatic foci. In present study, we focused on radioiodine resistance caused by TERT promoter mutation. Our preliminary data of miRNA microarray and luciferase reporter assay indicated that the under-expression of miR-145 could promote the transcription of two important transcription factors, ETS2 and c-Myc, resulting in the decrease of NIS in TERT mutated DTC cells. Therefore, based on most recent discoveries and our previous research, we have reason to believe that miR-145 participates in the occurrence of radioiodine-resistance in DTC with TERT mutation. We will further illuminate the role of TERT promoter mutation in the radioiodine-resistance of DTC metastatic foci, and explicitly define the molecular mechanism of miR-145 involved in the process of radioiodine resistance through regulating of ETS2 and c-Myc in DTC with TERT mutation.

碘难治性分化型甲状腺癌（RAIR-DTC）是目前甲状腺癌碘-131治疗领域的难点。我们前期研究发现TERT启动子突变与DTC远处转移病灶的不摄碘状态密切相关。本项目聚焦TERT启动子突变导致的碘抵抗，预实验初步发现miR-145低表达可靶向上调TERT启动子突变转录过程中的2个重要转录因子——ETS2和c-Myc的表达，并导致NIS表达水平下降，可能参与了碘抵抗的发生。在结合国际最新报道和前期研究后，我们提出假说：miR-145可通过靶向调控转录因子ETS2及c-Myc参与TERT启动子突变导致的碘抵抗的发生。本课题将进一步阐明TERT启动子突变在DTC远处转移病灶碘抵抗发生机制中的作用，在体外及体内水平系统探讨miR-145/ETS2/c-Myc参与该过程的机理，为提高碘-131治疗疗效提供分子依据。

碘难治性分化型甲状腺癌（RAIR-DTC）是目前甲状腺癌碘-131治疗领域的难点。我们前期研究发现TERT启动子突变与DTC远处转移病灶的不摄碘状态密切相关。本项目聚焦TERT启动子突变导致的碘抵抗，预实验初步发现miR-145低表达可靶向上调TERT启动子突变转录过程中的2个重要转录因子——ETS2和c-Myc的表达，并导致NIS表达水平下降，可能参与了碘抵抗的发生。本项目通过对BRAFV600E及TERTC228T共突变的细胞株MDA-T32及其对照组细胞株体外及体内研究发现：1. 在MDA-T32细胞系中瞬时转染miR-145 inhibitor 48h后碘转运蛋白表达降低，瞬时转染miR-145 mimics 48h后碘转运蛋白表达升高；2.COIP证实转录因子c-myc与ETS2存在相互作用；3.荧光素酶报告基因证实miR-145与ETS2及c-Myc均存在相互作用；4.在MDA-T32细胞系中CHIP证实ETS2及c-Myc均与TERT突变后的启动子区相结合；5.动物水平验证miR-145稳定敲低后的瘤组织对碘-131治疗不敏感，瘤体缩小不明显；miR-145稳定过表达后的瘤组织则对碘-131治疗敏感，瘤体缩小明显。初步证实miR-145可通过靶向调控转录因子ETS2及c-Myc参与TERT启动子突变导致的碘抵抗的发生。明确了miR-145/ETS2/c-Myc参与该过程的机理，为提高碘-131治疗疗效提供分子依据。