miR-155在甲状腺乳头状癌中调控机制的研究

Thyroid papillary thyroid carcinoma（PTC） is the most common malignant tumor in thyroid. Patients with highly invasive and metastatic PTC are refractory to conventional therapy. The abnormal expression on microRNAs in PTC cell is one of the important causes. Therefore, it is essential to identify the target molecule of microRNAs for drugs treatment. Our early experiments have shown that miR-155 promotes PTC cell migration and invasion, and further indicated that APC is the target gene. Meanwhile the expression of miR-155 was high in the tissue samples and PTC cells. In this experiment, we plan to use gene silencing and loss-of-function experiments to investigate the effect and mechanism by which the invasion and metastasis can be efficiently prevented by downregulating the miR-155 at the levels of molecule, cell, animal model and histopathology. Our research project aims to establish that endogenous miR-155 can be used as a therapeutic target for invasive and metastatic PTC, and to provide a theoretical basis for developing a novel therapy in refractory PTC and improve the clinical treatment effect.

甲状腺乳头状癌（PTC）是甲状腺最为常见的恶性肿瘤，现有治疗方案疗效差，其重要原因之一是PTC细胞内microRNAs表达异常。因此，探索microRNAs的药物治疗靶点具有重要意义。我们的前期实验提示：miR-155可促进细胞增殖、侵袭迁移，发现并证实APC基因为靶基因，且miR-155在PTC的组织和细胞中高表达。本研究拟通过基因沉默和功能缺失实验，进一步从分子、细胞、动物模型、组织病理水平上验证下调miR-155是否能阻止PTC细胞的侵袭转移并且阐明其调控机制，明确内源性miR-155作为侵袭转移性PTC治疗靶点的价值，为寻找PTC新的诊断治疗方式及其抗microRNAs治疗的临床转化提供理论依据，以及显著改善高侵袭转移性PTC的预后。

PTC是甲状腺最常见的恶性肿瘤。MicroRNAs (miRNAs)参与各种癌症进程，包括甲状腺乳头状癌（PTC）。miR-155最近被证明在脂肪肉瘤和乳腺癌中扮演重要角色，但其在PTC中的功能还不清楚。. 为调查miR-155在PTC中的潜在作用，本研究利用real-time PCR分析比较了20对甲状腺癌乳头状癌（PTC）及癌旁组织标本和人PTC细胞系中miR-155的表达，利用慢病毒载体，转染甲状腺癌细胞株TPC-1和CGTH-W3，构建了稳定表达miR-155的PTC细胞模型，检测miR-155对细胞生长的效应。软件预测并验证miR-155靶基因，体内体外实验验证 miR-155可能通过靶标APC基因，激活Wnt/β-catenin通路，促进PTC肿瘤生长。. 结果显示PTC癌组织和细胞系中miR-155表达显著增加，体外miR-155过表达显著增加PTC细胞活性和克隆形成，而miR-155干扰减少细胞活性和克隆形成。而APC表达对显著减少，两者具有显著负相关性；荧光素酶报告基因试验显示miR-155直接靶标APC 3ˊ-UTR区域，下调APC mRNA和蛋白表达。APC下调促进PTC细胞生长，APC过表达可消除miR-155的促生长效应。miR-155过表达激活Wnt/β-catenin通路，诱导其下游基因c-Myc，cyclin D1, TCF-1和LEF-1的表达。β-catenin干扰可部分抑制miR-155诱导的肿瘤细胞生长和克隆形成。体内裸鼠成瘤实验证明miR-155促进PTC细胞的体内生长。. 上述结果表明miR-155在PTC中作为一个原癌基因，靶标APC基因调控Wnt/β-catenin通路的活性。miR-155可能是PTC诊断和治疗的潜在靶点。