Hippo信号通路在胆汁酸代谢调控中的作用机制及其与肝癌产生的相关性研究

Almost all liver cancer are accompanied with bile acid deregulation, and studies have shown that bile acid disorders may be one of the main incentives of liver cancer, but the specific mechanism of bile acids maintaining liver homeostasis remains unclear. Recent studies have found that Hippo pathway is crucial in maintaining liver homeostasis, the absence of the key kinase Mst1/2 in liver leads to activation the downstream transcriptional coactivator Yap, promoting liver cell proliferation, liver enlargement, and 100% tumorigenesis in 3-month. Most human liver cancer samples showed increased expression and activity of Yap. Recently, we found that Mst1/2 deletion mice shows bile acids disorders. And Deoxycholic acid promotes Yap activation in hepatic cells, while ursodeoxycholic acid inhibits the expression and activation of Yap. This suggests Hippo pathway may maintain liver homeostasis by regulating the the bile acid homeostasis , and thus regulates the expression and activity of oncogenic Yap. This grant will clarify the mechanism of Hippo signaling pathway regulates bile acids homeostasis and correlation with liver cancer, and to explore the feasibility of ursodeoxycholic acid for the prevention and treatment of liver cancer at the molecular , cellular and whole animal level , which will further elucidate the pathogenesis of liver cancer and establish theoretical basis of liver cancer drug design.

几乎所有的肝癌都伴随着胆汁酸代谢紊乱，研究表明胆汁酸紊乱可能是肝癌产生的主要诱因之一，但胆汁酸调控肝脏稳态的具体机制仍不清楚。最近研究发现Hippo通路是维持肝脏稳态的关键通路，该通路蛋白激酶Mst1/2的缺失会激活下游的转录活化因子Yap，促进肝脏细胞增殖，肝脏肿大，3个月后100%发生肝癌。多数人类肝癌样品显示Yap的表达和活性升高。我们前期研究发现Mst1/2缺失会引起胆汁酸代谢紊乱；同时脱氧胆酸促进肝细胞中Yap的活化；相反熊脱氧胆酸，可有效抑制Yap的表达和活性。这表明Hippo通路可能通过调节胆汁酸代谢的平衡，进而调控癌基因Yap的表达和活性来维持肝脏稳态。本课题将在分子、细胞及整体动物水平上阐明Hippo信号通路调节胆汁酸代谢的机制及其与肝癌发生的相关性并探索熊脱氧胆酸用于预防与治疗肝癌的可行性，这将为深入阐明肝癌的发病机制和肝癌药物的研发奠定理论基础。

几乎所有的肝癌都伴随着胆汁酸代谢紊乱，研究表明胆汁酸紊乱可能是肝癌产生的主要诱因之一，但胆汁酸调控肝脏稳态的具体机制仍不清楚。Hippo通路是维持肝脏稳态的关键通路，该通路蛋白激酶Mst1/2的缺失会激活下游的转录活化因子Yap，促进肝脏肿大和肿瘤生成，且多数人类肝癌样品显示Yap的表达和活性升高。通过比较野生型和Mst1/2 缺失小鼠胆汁酸水平我们发现Hippo通路的缺失会造成小鼠胆汁酸水平升高，Hippo通路通过影响胆汁酸合成限速酶Cyp7a1的表达来影响胆汁酸的合成； Mst2可以磷酸化Cyp7a1的负调控因子SHP第28位丝氨酸来影响SHP的泛素化及其稳定性从而调控肝脏大小。此外，我们鉴定到Mst1/2缺失小鼠的胆汁酸组分中TCA显著升高，而TCA可以通过S1PR2激活Yap并促进Hippo通路介导肝脏肿大的发生。明确了不同胆汁酸组分对Yap活性的影响，即多数疏水性胆汁酸促进Yap入核，而大多亲水性胆汁酸促进Yap出核。最后在小鼠水平上，疏水性胆汁酸处理和降低总胆汁酸水平，均可抑制Mst1/2缺失造成的肝脏肿大和肿瘤生成。这也提示我们，未来干预胆汁酸代谢可能是预防和资料肝脏的一种新思路。. 在本项目的资助下，共发表SCI论文7篇，并发表专著中的一章一篇。并培养博士研究生一名，硕士研究生四名，上述成果均超过预期研究目标。综上所述，我们良好地完成了项目申请书中所列的研究内容和目标。