胃癌是我国发病率最高的恶性肿瘤之一，易转移，预后差，其转移机制尚不明确。环状RNA是一类新发现的非编码RNA，与肿瘤的发病密切相关。课题组前期鉴定出一个新的环状RNA： Circ-TNPO3，在胃癌中表达显著下调，且能抑制胃癌生长和转移。我们初步证实，Circ-TNPO3可同时结合miR-199a-5p和HuR蛋白，调控EMT相关分子（E-cadherin、Snail等）。本项目拟利用慢病毒、siRNA、pull-down、RIP、荧光素酶等方法，进一步阐明Circ-TNPO3与miR-199a-5p和HuR的竞争结合作用，并鉴定其下游信号通路和成环机制，以验证假说“Circ-TNPO3具有结合miRNA和蛋白的双重功能，通过调控miR-199a-E-cadherin/Smad4和HuR-Snail/MMP-9通路，影响EMT进程，调控胃癌转移”。这为进一步阐明胃癌的转移机制提供新思路。

Gastric cancer is one of the most common malignant tumors in China, however the molecular mechanism underlying the development and metastasis of gastric cancer remains unclear. circRNAs are novel non-coding RNAs with important regulatory role, growing evidence has shown that aberrant circRNAs expression correlates with various human cancers. Our previous study identified a novel circRNA named as Circ-TNPO3. We found Circ-TNPO3 was significantly down-regulated in gastric cancer tissues, and Circ-TNPO3 was able to suppress the proliferation and metastasis of gastric cancer cells in vitro and in vivo. We then preliminarily confirmed that Circ-TNPO3 could competitively bind miR-199a-5p and HuR, and regulate EMT related molecules such as E-cadherin, Snail1, et al. In current project, we plan to further clarify the competitively binding interaction between Circ-TNPO3 and miR-199a-5p or HuR, and identify its downstream signaling pathways, and study the biogenesis mechanism of Circ-TNPO3 by using overexpression or knock-down of Circ-TNPO3 expression, pull-down assay, RNA immunoprecipitation(RIP), luciferase report system. We will verify our hypothesis that Circ-TNPO3 can competitive bind miR-199a-5p and HuR protein, and regulate EMT process and metastasis of gastric cancer through mediating miR-199a-E-cadherin/Smad4 and HuR-Snail1/MMP-9 axis. Our study will provide new clues to elucidate the mechanism of metastasis of gastric cancer.