來自南開大學(xué)生命科學(xué)學(xué)院的研究人員在新研究中證實(shí)：乙型肝炎病毒X蛋白（hepatitisBvirusXprotein，HBx）通過CREB介導(dǎo)YAP癌基因促進(jìn)了肝癌細(xì)胞生長。相關(guān)論文發(fā)表在12月的國際著名肝臟疾病雜志Hepatology上（最新影響因子11.665）上。

　　南開大學(xué)生命科學(xué)學(xué)院的張曉東（XiaodongZhang）教授和葉麗虹（LihongYe）為這篇論文的共同通訊作者。前者的主要研究領(lǐng)域?yàn)槟[瘤分子生物學(xué)，開展乙肝病毒致癌分子機(jī)制和乳腺癌轉(zhuǎn)移分子機(jī)制研究，篩選抗腫瘤藥物。后者的研究方向是腫瘤發(fā)生、發(fā)展和轉(zhuǎn)移的分子機(jī)制；抗腫瘤藥物篩選。

　　乙型肝炎病毒(HBV)慢性感染是我國肝細(xì)胞肝癌(HCC)發(fā)生的主要原因之一。一些體內(nèi)外研究發(fā)現(xiàn)，HBx可誘導(dǎo)肝細(xì)胞的惡性轉(zhuǎn)化及癌變，成為目前研究乙肝相關(guān)性肝細(xì)胞癌生機(jī)制的熱點(diǎn)。近來在HBx與抑癌基因，如p53的新成員p73以及p16，p21等之間的相互作用及其對肝細(xì)胞惡性轉(zhuǎn)化與癌變的影響等方面的研究也取得初步成果，但其關(guān)系錯(cuò)綜復(fù)雜，這方面不斷的深入研究將有助于進(jìn)一步揭示HBx致肝細(xì)胞癌發(fā)生的分子機(jī)制，對探尋乙肝相關(guān)性肝癌新的防止策略具有重要意義。

　　在這篇文章中，研究人員證實(shí)HBx介導(dǎo)YAP參與了肝癌形成。研究人員發(fā)現(xiàn)臨床肝癌樣本、乙肝病毒感染肝癌HepG2.2.15細(xì)胞系及HBx轉(zhuǎn)基因小鼠的肝癌組織中的YAP表達(dá)均顯著增高。同時(shí)，他們發(fā)現(xiàn)HBx過表達(dá)導(dǎo)致了HBx穩(wěn)定轉(zhuǎn)染的HepG2/H7402肝癌細(xì)胞系中YAP表達(dá)上調(diào)，而在上述細(xì)胞系中采用HBxRNA干擾則以劑量依賴性的方式減少了YAP的表達(dá)，這表明HBx可以正調(diào)控YAP。

　　隨后，研究人員解析了HBx上調(diào)YAP的潛在分子機(jī)制。熒光素酶報(bào)告基因檢測揭示HBx對YAPnt-232/+115這一包含cAMP反應(yīng)元件結(jié)合蛋白(CREB)元件的啟動(dòng)子區(qū)域進(jìn)行了調(diào)控。通過染色質(zhì)免疫沉淀法(ChIP)，研究人員證實(shí)HBx能夠結(jié)合到Y(jié)AP的啟動(dòng)子上，但當(dāng)CREB沉默時(shí)它不能發(fā)揮作用。此外，借助于電泳遷移率實(shí)驗(yàn)（EMSA）和熒光素酶報(bào)告基因檢測，他們也證實(shí)HBx激活了YAP啟動(dòng)子。在體內(nèi)外實(shí)驗(yàn)中，研究人員還證實(shí)YAP短干擾RNA（shortinterfering RNA）能夠顯著阻斷HBx增進(jìn)肝癌細(xì)胞生長的效應(yīng)。

　　這些結(jié)果表明YAP是HBx誘導(dǎo)肝癌形成中的一個(gè)關(guān)鍵驅(qū)動(dòng)基因，其或可作為一種治療乙肝病毒相關(guān)肝癌的新靶點(diǎn)。

 　　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, XiaoYang3, 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.