HHV-6b感染/活化/整合在CHB相关肝硬化HVEM高表达时促发HCC的机制研究

It is well known that the occurrence of HCC in China is closely related to CHB associated cirrhosis, aflatoxin and Pond-ditch water. With rapid urbanization, the latter two factors have been well controlled while the incidence of HCC is still high, which indicating that there must be other unknown inducing factors. But, what’s it? Or, what are they? Patients with CHB associated cirrhosis are in a status of declined immune function with high expression of HVEM gene in liver cells, resulting in T-cell immune dysfunction and forming an immunosuppressive microenvironment in local tissue. Our previous study has found the high positive rates of HHV-6b in both peritumoral liver tissue and HCC tissue samples. FISH experiments further confirmed that HHV-6b sequence was presented in the nuclei and integrated in telomeres of human chromosomes. Therefore, we propose that the CHB associated cirrhosis would promote the expression of HVEM gene, resulting in T-cell immune dysfunction and forming an immunosuppressive microenvironment, leading to HHV-6b infection in liver tissue and finally induces the malignant transformation of hepatocytes. The main aim of this project is to identify that HHV-6b is an important pathogen in the carcinogenesis of HCC through RT-PCR, FISH technology, tree shrew animal model, and so on. By elucidating the new mechanism of HCC promoted by HHV-6b, we believe this project would provide solid evidences that HHV-6b is an important pathogen of carcinogenesis for preventing and controlling the development of HCC.

已知我国HCC的发生与CHB肝硬化、黄曲霉毒素、饮用沟塘水密切相关。随着城镇化高速推进，后两个致HCC因素已获较好控制，但HCC发病率仍居高不下，提示HCC的发生存在其他促发因素。这个未知的促发因素是什么？CHB肝硬化时机体免疫功能下降，此时肝组织存在HVEM高表达，形成局部“免疫抑制微环境”。我们的实验显示此时HCC癌周肝组织、癌细胞中均存在HHV-6b高感染。进一步的FISH实验显示HHV-6b可存在于细胞核内，并在染色体端粒位置整合。由此，我们首次提出：HHV-6b是CHB肝硬化HVEM高表达时HCC发生的重要促发病原体，免疫抑制微环境是重要基础。本项目拟进一步采用定量PCR、FISH技术和树鼩等展开研究，旨在获得HHV-6b是癌变重要促发病原体的可靠证据。本项目将阐明HHV-6b参与HCC发生的机制和影响因素，为确立HHV-6b作为防控HCC发生的重要病原体提供更充分的科学依据。

我国肝细胞癌（HCC）的发病率和病死率均在恶性肿瘤中居前三位，其5年生存率仅有11%左右，严重威胁人民生命健康。本课题围绕我国HCC与慢性乙型肝炎肝硬化（CHB-Cir）和人疱疹病毒6B（HHV-6b）感染时形成的免疫抑制微环境及其相互作用展开；CHB-Cir通过驱动免疫抑制相关基因表达促进肝组织局部的T细胞免疫功能低下，形成“免疫抑制微环境”，导致易于感染HHV-6b。HHV6b感染后协同HBV抑制p53表达，通过对AFP基因表观遗传修饰驱动AFP表达，使免疫抑制微环境恶化，此免疫抑制的微环境的恶化被认为是HCC发生的重要促发机制。本项目按照原计划，结合国内外研究进展和年度报告批准的调整计划，对此进行了深入研究，发现：.1）HHV-6B感染在慢性乙型病毒性肝炎、乙肝肝硬化及肝细胞癌在疾病发生发展过程中均有不同程度的影响，同时在HCC中表达率最高，且与HCC预后相关；.2）HHV-6b感染，特别是其表达的ORF-1蛋白可促进PI3K/AKT信号通路的激活，促进AFP基因启动子区域去甲基化和组蛋白乙酰化，抑制p53蛋白，促进免疫抑制微环境下肝细胞的恶性转化；.3）对肝细胞癌发生的早期识别，是最重要的临床问题，本研究基于人工智能技术，建立B超识别肝脏占位性病变性质的智能工具，具有较大的临床应用潜力；.4）基于单细胞转录组测序技术，绘制了病毒感染后肝脏的“炎症再生结节－肝硬化－肝癌”多步骤癌变过程的单细胞图谱。本项目结果不仅发现了新的促肝癌发生发展的潜在病原体，同时也结合了大数据时代的单细胞转录组测序技术和人工智能技术，为肝癌的早期诊断、个体化精准治疗提供了基础理论依据。