ZNF191调控Wnt信号通路促进肝癌细胞增殖分子机制研究

Hepatocellular carcinoma (HCC) is a primary cancer of the liver and one of the most common diagnosed cancers in Chinese population. Various risk factors have been associated with HCC, The pathogenesis of the development and progression of HCC is far from being clear presently, and several cellular signal transduction pathways are involved in HCC. In our previous research, ZNF191 can directly bind to the CTNNB1 promoter and activate the expression of β-catenin and its downstream target genes such as cyclin D1 in hepatoma cell lines and we demonstrated that the key binding sequence of ZNF191 in vivo is ATTAATT. The findings suggest a possible role of ZNF191 in association with cell proliferation of HCC. In this study, we identified the expression of Wnt8B, one of Wnt family members which can activate canonical Wnt signaling cascades, maybe closely associated with ZNF191 in HCC cells, and ZNF191 can activates the 2Kbps Wnt8B promoter. The findings suggest that ZNF191 may function through up-regulating Wnt8B, in addition to β-catenin, to promote tumor cell proliferation in vivo. The expression level of Wnt8B and the molecular mechanism of transcription regulation of the Wnt8B gene remains unknown.In this research we will investigate: (1)the relationship between ZNF191 and Wnt8B mRNA and protein expression in human HCCs and heptoma cell lines; (2) the molecular mechanism of ZNF191 in regulation of Wnt8B expression. We hope the research can elucidate the role of ZNF191 in regulating Wnt pathway in the development and progression of HCC more completely.

肝癌是一种在我国人群中高发的恶性肿瘤。作为多基因病其发病的分子机制尚不明确，但已发现多条信号通路与肝癌发生相关。前期研究发现人锌指蛋白ZNF191直接靶向上调经典Wnt通路关键基因β-Catenin的转录，促进β-Catenin及下游基因Cyclin D1的mRNA及蛋白水平，促进肝癌细胞增殖。本研究中我们发现Wnt通路激活蛋白Wnt8B可能和ZNF191密切相关，且ZNF191能促进Wnt8B启动子的转录。结果提示ZNF191不仅通过调节β-Catenin，也可能通过调节上游基因Wnt8B来激活Wnt通路，从而促进肝癌细胞增殖。Wnt8B在人肝癌内的表达情况及调控尚未见报道。本课题以Wnt8B为切入点，进一步完善肝癌发生发展中ZNF191对Wnt信号通路的调控作用，回答：(1)Wnt8B在肝癌内的表达及其与ZNF191的相关性；(2)ZNF191对Wnt8B调控的分子机制。

ZNF191在肝癌中发病机制目前尚未明确。本项目主要从以下两方面进行展开：1）ZNF191通过靶向调控Wnt8B促进肝癌细胞增殖的机制研究；2）ZNF191抑制肝细胞肝癌转移机制研究。研究结果：i) 在肝癌标本和肝癌细胞系内ZNF191对Wnt8B的mRNA和蛋白水平有调控作用，ZNF191/Wnt8B途径对经典Wnt通路有激活作用。ZNF191蛋白能直接结合Wnt8B基因的启动子，ZNF191结合Wnt8B基因的启动子的调控元件为-1491位ATTAATT，以及-1178位ATTCATT。ii）ZNF191的下调表达与肝癌转移相关。ZNF191能抑制肝癌细胞的迁移和转移，抑制肝癌细胞在裸鼠体内的转移。ZNF191可以通过转录激活DLG1抑制与YAP1相关的肝癌转移。综上结果，ZNF191在肝癌发病中发挥着双重作用：在肝癌发生早期，ZNF191通过靶向激活Wnt通路基因如β-catenin, Wnt8B促进肝癌细胞增殖；在肝癌晚期时通过靶向激活DLG1抑制YAP1活性发挥抑制肝癌转移作用。ZNF191是促进肝癌形成发展演变的重要转录因子，我们的研究结果为ZNF191可能作为潜在的肝癌预后分子标志物提供理论依据。