Hepatology：乙型肝炎病毒蛋白促进肝癌细胞生长

来自南开大学生命科学学院的研究人员在新研究中证实：乙型肝炎病毒X蛋白（hepatitis B virus X protein，HBx）通过CREB介导YAP癌基因促进了肝癌细胞生长。相关论文发表在12月的国际著名肝脏疾病杂志Hepatology上（最新影响因子11.665）上。

南开大学生命科学学院的张晓东（Xiaodong Zhang）教授和叶丽虹（Lihong Ye）为这篇论文的共同通讯作者。前者的主要研究领域为肿瘤分子生物学，开展乙肝病毒致癌分子机制和乳腺癌转移分子机制研究，筛选抗肿瘤药物。后者的研究方向是肿瘤发生、发展和转移的分子机制；抗肿瘤药物筛选。

乙型肝炎病毒(HBV)慢性感染是我国肝细胞肝癌(HCC)发生的主要原因之一. 一些体内外研究发现, HBx可诱导肝细胞的恶性转化及癌变, 成为目前研究乙肝相关性肝细胞癌生机制的热点. 近来在HBx与抑癌基因, 如p53的新成员p73以及p16,  p21等之间的相互作用及其对肝细胞恶性转化与癌变的影响等方面的研究也取得初步成果, 但其关系错综复杂, 这方面不断的深入研究将有助于进一步揭示HBx致肝细胞癌发生的分子机制, 对探寻乙肝相关性肝癌新的防治策略具有重要意义.

在这篇文章中，研究人员证实HBx介导YAP参与了肝癌形成。研究人员发现临床肝癌样本、乙肝病毒感染肝癌HepG2.2.15细胞系及HBx转基因小鼠的肝癌组织中的YAP表达均显着增高。同时，他们发现HBx过表达导致了HBx稳定转染的HepG2/H7402肝癌细胞系中YAP表达上调，而在上述细胞系中采用HBx RNA干扰则以剂量依赖性的方式减少了YAP的表达，这表明HBx可以正调控YAP。

随后，研究人员解析了HBx上调YAP的潜在分子机制。荧光素酶报告基因检测揭示HBx对YAP nt ?232/+115这一包含cAMP反应元件结合蛋白(CREB)元件的启动子区域进行了调控。通过染色质免疫沉淀法(ChIP)，研究人员证实HBx能够结合到YAP的启动子上，但当CREB沉默时它不能发挥作用。此外，借助于电泳迁移率实验（EMSA）和荧光素酶报告基因检测，他们也证实HBx激活了YAP启动子。在体内外实验中，研究人员还证实YAP短干扰RNA（short interfering RNA）能够显着阻断HBx增进肝癌细胞生长的效应。

这些结果表明YAP是HBx诱导肝癌形成中的一个关键驱动基因，其或可作为一种治疗乙肝病毒相关肝癌的新靶点。

DOI: 10.1002/hep.25899
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Hepatitis B virus X protein modulates oncogene yes-associated protein by CREB to promote growth of hepatoma cells

Tao Zhang1, Junping Zhang1, Xiaona You1, Qian Liu2, Yumei Du1, Yuen Gao1, Changliang Shan1, Guangyao Kong1, Youliang Wang3, Xiao Yang3, Lihong Ye2,‡,*, Xiaodong Zhang1,§,*

Hepatitis B virus X protein (HBx) plays critical roles in the development of hepatocellular carcinogenesis (HCC). Yes-associated protein (YAP), a downstream effector of the Hippo-signaling pathway, is an important human oncogene. In the present article, we report that YAP is involved in the hepatocarcinogenesis mediated by HBx. We demonstrated that the expression of YAP was dramatically elevated in clinical HCC samples, hepatitis B virus (HBV)-infected hepatoma HepG2.2.15 cell line, and liver cancer tissues of HBx-transgenic mice. Meanwhile, we found that overexpression of HBx resulted in the up-regulation of YAP in stably HBx-transfected HepG2/H7402 hepatoma cell lines, whereas HBx RNA interference reduced YAP expression in a dose-dependent manner in the above-mentioned cell lines, suggesting that HBx up-regulates YAP. Then, we investigated the mechanism underlying the up-regulation of YAP by HBx. Luciferase reporter gene assays revealed that the promoter region of YAP regulated by HBx was located at nt −232/+115 containing cyclic adenosine monophosphate response element-binding protein (CREB) element. Chromatin immunoprecipitation (ChIP) demonstrated that HBx was able to bind to the promoter of YAP, whereas it failed to work when CREB was silenced. Moreover, we confirmed that HBx activated the YAP promoter through CREB by electrophoretic mobility shift assay and luciferase reporter gene assays. Surprisingly, we found that YAP short interfering RNA was able to remarkably block the HBx-enhanced growth of hepatoma cells in vivo and in vitro. Conclusion: YAP is a key driver gene in HBx-induced hepatocarcinogenesis in a CREB-dependent manner. YAP may serve as a novel target in HBV-associated HCC therapy.