乙肝病毒X蛋白调控生物钟基因Cry2促进肝癌转移的机制研究

The abnormal expressions of clock-controlled genes stemming from the disturbance of internal body clock are closely associated with metastases. Cry2 is one of the core members of the circadian clock gene family. Our team found that, circadian clock gene Cry2 had a low expression in hepatocellular carcinoma (HCC) tissue and was closely related to metastasis of HCC, but the metastasis remain unknown. Our team carried out further research and found that hepatitis B virus X protein (HBx) can downregulate the expression of circadian clock gene Cry2 and thus upregulate the expression of metastasis-associated gene 1 (MTA1). Moreover, HBx can upregulate the expression of DNA methyltransferase 1 (DNMT1), which results in an upregulation of Cry2. We infer that HBx may inhibit its expression by inducing the methylation of Cry2 gene promotor in liver cancer, which further induces the upregulation of MTA1 and mediates the metastasis of liver cancer. This study attempted to clarify the relationship and underlying mechanism between HBx, methylation and expression of Cry2, as well as the relationship between Cry2 and MTA1, metastasis of liver cancer by cell experiments, animal experiments and using clinical samples, so as to find new treatment strategies for metastatic liver cancer.

生物钟紊乱引起的钟控基因的表达异常和肿瘤转移密切相关。Cry2是生物钟基因家族核心成员之一。本团队发现：在肝癌中Cry2表达降低，并与肝癌转移密切相关，但其具体机制目前尚不清楚。我们进一步研究发现：1、乙肝病毒X蛋白（HBx）可下调生物钟基因Cry2的表达，进而上调钟控基因转移相关蛋白1（MTA1）的表达。2、HBx可上调DNA甲基转移酶1的表达，而干扰该酶的表达后Cry2表达增加。因此，我们推测HBx可能通过诱导肝癌中Cry2启动子甲基化抑制其表达，导致MTA1表达上调，进而介导肝癌转移。本项目将分别通过细胞实验、动物实验及临床样本检测研究HBx、甲基化和Cry2表达的关系，观察Cry2与MTA1及肝癌转移的关系，探讨相关机制，寻找预防和治疗转移性肝癌的新的治疗方法。

生物钟紊乱引起的钟控基因的表达异常和肿瘤转移密切相关。Cry2是生物钟基因家族核心成员之一。本团队通过生信分析和免疫组化检测发现Cry2在肝癌组织中呈低表达状态，肝癌组织中Cry2的表达和肿瘤大小、结节个数、血管侵犯呈负相关。HBx蛋白的表达和肿瘤分化程度及血管侵犯相关，HBx高表达和Cry2低表达是肝癌患者预后不良的独立危险因素。进一步研究发现Cry2的低表达状态和HBV以及HBx相关。HBx可以上调DNA甲基转移酶1的表达，进而诱导包括Cry2在内的多个生物钟启动子的甲基化，临床标本检测也发现肝癌组织中Cry2启动子甲基化水平高于癌旁组织。Cry2表达下调后钟控基因转移相关蛋白1（MTA1）的表达上调，从而导致了肝癌细胞侵袭和转移能力增强。本研究丰富了肝癌发生、发展的机制。也为肝癌的一级预防和肝癌抗病毒治疗提供了理论依据。