肝细胞肝癌中抑癌基因DLC1表达沉默的遗传学与表观遗传学机制

DLC1 (Deleted in Liver Cancer 1) is an important tumor suppressor gene, which is closely related with proliferation, relapse and metastasis in various malignant tumor especially in hepatocellular carcinoma.But the exact mechanism of DLC1 unexpression or underexpression is still unknown.We found that genetic and epigentic mechanism was involved in DLC1 silencing.Based on our previously ChIP-on-chip data, we will thoroughly study the exact mechanism of the negative epigenetic modification,such as DNA methylation and H3K27me3, in silent DLC1 expression. Through the genome chromosome sequencing,we will analyze DLC1 mutant function, especially focus on the new mutants such as L81V. Through the Co-IP, protein stability test etc, we will discuss the molecular mechanism of DLC1 mutant which loses the tumor suppressor function. Combining with clinical information,we will analyze the correlation between DLC1 unexpression or underexpression and prognosis.We will screen and identify the key molecules which regulate DLC1 expression in HCC,and clarify biological significance. All of those will help us reveal the key mechanism of DLC1 silencing in HCC, which might be important for early diagnosis,treatment and prognosis prediction of hepatocellar carcinoma.

DLC1（Deleted in Liver Cancer 1）是与多种恶性肿瘤尤其是肝癌的增殖、复发转移密切相关的重要抑癌基因，但目前尚缺乏肝癌中DLC1表达沉默机制的完整认识。我们发现，遗传学和表观遗传学机制可能共同参与肝癌中DLC1基因表达沉默。本研究拟通过整合已有的ChIP-on-chip组学数据，深入探讨DNA甲基化、H3K27me3等负性表观遗传学修饰在抑制DLC1转录过程中的关键协同作用；深入整理和分析通过基因组染色体测序已获得的DLC1突变体信息，尤其聚焦于L81V等新发现的突变体，通过免疫共沉淀、蛋白质稳定性等试验，进一步深入探讨DLC1突变体丧失抑癌功能的分子基础；结合临床资料分析DLC1失活或表达沉默与预后的相关性；筛选和鉴定肝癌中受DLC1调控的关键分子及其生物学意义。将有助于揭示DLC1在肝癌中表达下调的关键机制，对肝癌早期诊断、治疗及预后判定具有重要指导意义。

DLC1是与多种恶性肿瘤的增殖、复发转移密切相关的重要抑癌基因，但目前尚缺乏肝癌中DLC1表达沉默及抑癌机制的完整认识。本研究采用外显子测序、ChIP、荧光素酶报告基因等关键技术，探讨了DLC1的遗传变异及其临床意义；明确了生长因子IGF1沉默DLC1表达的表观遗传学机制；阐明了肝癌组织DLC1的表达水平及其临床意义；阐明了DLC1抑制肝癌发生发展的机制。结果显示，DLC1的SNP基因型与肝癌的易感性以及肿瘤大小相关，而与预后无关；生长因子IGF1通过激活AKT通路，抑制DNA甲基转移酶DNMT1的泛素化降解，从而上调DLC1基因启动子CpG岛甲基化水平，最终抑制DLC1表达；肝癌组织低表达DLC1与肝癌血管侵犯、肿瘤分化程度、不良预后显著相关，DLC1通过负性调控Wnt通路、RhoA-ROCK1通路抑制肝癌细胞增殖、迁移侵袭和细胞自噬。本研究为以DLC1为靶点的肝癌的早期诊断及预后评估提供了理论基础。