丙型肝炎病毒核心蛋白与Snail协同调控E-cadherin表达及参与肝癌转移的分子机制

Hepatocelluar carcinoma (HCC) is the fifth most common cancer worldwide and ranks as the third leading cause of cancer-related death in humans. One of the most important risk factors for the development of HCC is chronic hepatitis C virus (HCV) infection. The oncogenic role of HCV core and its molecular mechanisms in HCV-induced hepatocarcinogenesis have not been clearly elucidated. Down-regulation of E-cadherin by transcriptional repressor Snail is associated with acquisition of metastatic potential. Although hepatitis C virus (HCV) core protein has been implicated in hepatocarcinogenesis, it is unclear if Snail involves in the dysregulation of E-cadherin induced by HCV core.. .Our preliminary data indicate that 1) HCV core effectively induced epithelial-mesenchymal transition (EMT) in hepatoma cells by repressing E-cadherin; 2) HCV core was shown to interact with Snail and enhanced its binding to E-box in the promoter region of E-cadherin, leading to the decreased E-cadherin promoter activity; 3) HCV core activates the Akt/GSK3β pathway to regulate Snail-dependent EMT...Based on our preliminary data, we hypothesized that HCV core could repress E-cadherin through the formation of the core-Snail-histone deacetylases (HDACs) transcriptional corepressor complex, resulting in EMT induction, leading to hepatoma cell metastasis. In this study, the effect of HCV core protein on the morphology and migration capacity of hepatoma cells was examined. HCV-infected primary human hepatocyte, HCV Core-transduced cells and HCV-related HCC tissue samples were used to investigate the molecular mechanism that HCV core induces E-cadherin repression and the role of Snail in HCV core-mediated invasiveness. Luciferase reporter and chromatin immunoprecipitation assays were used to assess the effect of Snail on transcriptional repression induced by HCV core. Xenograft tumor model was to determine the effect of Snail on HCV core-mediated invasiveness and metastasis. Our studies will provide new insights into the molecular mechanism underlying tumor invasion and metastasis in HCV-related HCC, and could potentially lead to novel therapeutic approaches for the treatment of metastatic HCC in patients with chronic HCV infection.

HCV感染是肝癌发生的重要危险因素，HCV与EMT（上皮样细胞向间质样细胞转化）的发生并参与HCC的转移和侵袭，是当前研究热点。课题组前期研究发现：HCV Core过表达细胞侵袭力增强，E-cadherin启动子区Snail结合增强，启动子活性受抑制、其表达下调，PI3K/Akt信号通路活化。由此我们提出“HCV Core协同 Snail调控E-cadherin表达，参与HCC转移”的科学假说。本研究拟通过HCV感染和Core过表达细胞模型、裸鼠肝癌转移模型及临床组织病理分析，检测HCV Core、Snail和 E-cadherin表达相关性，解析Core与Snail或组蛋白修饰酶形成复合物，调控E-cadherin表达；研究PI3K/Akt信号通路如何参与HCV Core诱导的EMT。本研究旨在探讨Core调控E-cadherin并参与HCC转移的机制，并为优化肝癌的防治策略提供新手段。

HCV感染是原发性肝癌发生的重要危险因素，HCV与EMT（上皮样细胞向间质样细胞转化）的发生并参与HCC的转移和侵袭，是目前国内外的研究热点。课题组前期研究发现：HCV Core过表达细胞侵袭能力增强，E-cadherin启动子活性受抑制、表达下调，由此我们提出“HCV Core协同 Snail调控E-cadherin表达，参与HCC转移”的科学假说。我们首先在HCV体外复制细胞模型、HCV Core过表达细胞模型以及HCV感染的临床肝癌组织标本中，发现HCV Core可以增强肝癌细胞迁移、侵袭能力，HCV体外复制及HCV Core过表达细胞模型中E-cadherin的表达下调、Vimentin表达上调，提示HCV Core可以促进肝癌细胞的EMT进程。免疫荧光和IP实验证实：HCV Core可以和转录因子Snail-C端153-264位氨基酸编码蛋白结合形成抑制性复合物，进一步的机制研究表明：HCV core通过Snail招募HDAC1/2，增强其与CDH1启动子区E-box的结合，负性调控E-cadherin的表达，转录因子Snail在复合物形成过程中起到桥梁作用。此外还发现， HCV Core激活Akt/GSK-3β信号通路，诱导GSK-3β磷酸化，上调Snail稳定性，抑制上皮细胞标志物E-cadherin的表达，诱导EMT进程。上述研究从一个全新的角度阐释了HCV感染和病毒基因产物参与肝癌恶性转移的发生机制，并为临床优化肝癌的预防与治疗策略提供了新的手段。

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