肝癌中HBx、GSK-3β和Nur77交互作用与调控

Hepatitis B virus X protein (HBx) is critical for the development of hepatocellular carcinoma. It is suggested that the biological function of HBx is largely dependent on its interaction with cellular proteins, accompanied by changes in intracellular signaling pathways. Identification of novel HBx-interacting proteins will be very useful for disclosing the underlying mechanism by which HBx contributes to tumor growth. In our pilot study, we found that HBx could interact with Nur77 orphan nuclear receptor resulting in decreased Nur77 stability. Nur77, an early response gene induced by stress stimuli, is implicated in regulation of both cell survival and death. It is demonstrated that Nur77 may serve as a potential and promising drug target in tumors. However, Nur77-based therapeutic approaches may be impaired by HBx through physiological interaction, a possible cause for drug resistance and tumor development. It is interesting to note that HBx interaction with Nur77 is closely associated with GSK-3β expression. The objective of this proposal is to dissect the interaction and regulation of HBx, GSK-3β and Nur77, exploring their roles in liver cancer cells. This study will help to disclose a novel action of HBx in hepatocellular carcinoma and provide basis for developing new anticancer strategies.

乙型肝炎病毒（Hepatitis B virus，HBV）的X蛋白（HBx）是肝癌的一种关键致病因子，主要通过靶向细胞内不同蛋白质和影响众多细胞信号转导通路起作用，发现其相互作用蛋白将有助于揭示肝癌发病机制。我们最近发现，HBx可与孤儿核受体Nur77相互作用，并显著影响Nur77的蛋白稳定性。Nur77是细胞应答应激反应的重要功能基因，调控细胞生存与死亡，是肿瘤中一个理想的药物靶点，HBx与Nur77相互作用可能影响Nur77作为药物靶点的活性，并与肝癌进展和耐药性可能有密切关系。有趣的是，HBx与Nur77的相互作用，与肿瘤中糖原合成激酶-3β（GSK-3β）的表达有关。本项目将深入研究HBx、GSK-3β和Nur77的交互作用方式、信号通路，阐述其在肝癌中的作用，揭示HBx新的致癌机制，为发展新的肝癌治疗方法提供理论依据。

通过本项目的实施，阐述了Nur77是HBx的下游基因，HBx通过与Nur77的直接相互作用，影响Nur77的转录激活功能，诱导MMP-2和整合素a3/b1的表达，从而促进肝癌细胞的增殖和迁移。GSK-3b在其中的作用表现在，HBx可促进入核，GSK-3b入核后可诱导具有完整N-端结构域的Nur77的降解，而对于缺失N-端的DEF突变体无作用，另一方面，GSK-3b还可显著影响Nur77的异源二聚体伴侣RXRa的磷酸化，HBx、Nur77、RXRa和GSK-3b之间的关系较为复杂，有关课题仍在进一步进行中。有关成果发表了1篇Sci二区文章（Br J Cancer 2014; 110:935-945，影响因子5.05），培养了2名研究生。综上，我们已完成了项目所规定的任务和预期目标，并在开展课题过程中有新的发现和进展。