Fbxw7通过泛素化蛋白酶解YAP蛋白诱导肝癌细胞凋亡和生长阻滞

Hepatocellular carcinoma (HCC) is one of the most common malignant tumor in China. Since our previous study indicates that Fbxw7 is an independent prognostic marker in HCC and Fbxw7 inhibits cell proliferation and induces apoptosis in HCC cells, but the mechanisms is still unclear. The abnormal activation and accumulation of YAP protein in the nucleus by inactivation of Hippo signaling pathway is a key factor for promoting development and progression of HCC, but the mechanisms is still unknown. Our previous research shown that Fbxw7 was negatively correlated with YAP protein in HCC tissues and Fbxw7 inversely regulated the expression of YAP protein in HCC cells. We found that there was interaction between Fbxw7 and YAP by using co-immunoprecipitation and a canonical phosphodegron recognized by Fbxw7 in YAP protein by using mass spectrometric analysis. In the present project, we try to determine whether Fbxw7 functions as a tumor suppressor via regulating Hippo/YAP signaling pathway by ubiquitination and proteasomal degradation YAP protein. Furthermore, we attempt to verify the mechanisms involved in ubiquitination and regulation of YAP protein by Fbxw7 through gene mutagenesis. The aim of this project is to investigate the molecular mechanisms of both the anti-HCC effect of Fbxw7 and abnormal activation and accumulation of YAP protein in the nucleus, in order to provide the scientific basis to exploit novel targeting agents and predictive biomarkers for HCC clinically.

肝细胞癌（HCC）是我国最常见的恶性肿瘤之一。我们前期证实Fbxw7是一个独立的HCC患者预后标志物，Fbxw7具有抑制HCC细胞增殖和诱导凋亡的作用，但分子机制不明。Hippo通路失活导致YAP蛋白异常活化和核内蓄积是促进HCC发生发展的关键，但机制仍不清。我们前期研究发现HCC组织中Fbxw7与YAP蛋白表达负相关，HCC细胞中Fbxw7负向调控YAP蛋白，免疫共沉淀发现Fbxw7与YAP存在相互作用，进一步质谱分析发现YAP蛋白存在Fbxw7结合的经典磷酸决定子。本项目是既往工作的深入，拟通过体内外实验证实Fbxw7通过泛素化降解YAP蛋白调控Hippo/YAP通路发挥抑癌作用，进而通过基因突变等技术探索Fbxw7泛素化调控YAP蛋白的分子机制。本项目旨在阐明Fbxw7抗HCC作用的分子机制以及YAP蛋白异常活化和核内蓄积机制，为临床上开发新的HCC靶向治疗药物和预后标志物提供依据。

肝细胞癌（HCC）是世界上最常见的恶性肿瘤之一。我们前期证实Fbxw7是一个独立的HCC患者预后标志物，Fbxw7具有抑制HCC细胞增殖和诱导凋亡的作用，但分子机制不明。Hippo通路失活导致YAP蛋白异常活化和核内蓄积是促进HCC发生发展的关键，但机制仍不清。我们前期研究发现HCC组织中Fbxw7与YAP蛋白表达负相关，HCC细胞中Fbxw7负向调控YAP蛋白，免疫共沉淀发现Fbxw7与YAP存在相互作用，进一步质谱分析发现YAP蛋白存在Fbxw7结合的经典磷酸决定子。现有研究发现，Fbxw7在多种肿瘤细胞中均发挥着抑癌基因的作用，其可以接受miRNA和lncRNA的调控来调节肿瘤的发生发展，但是Fbxw7在HCC细胞中与miRNA和lncRNA的调控关系及潜在机制都有待进一步探究。本项目通过一系列体内外实验证实Fbxw7通过泛素化降解YAP蛋白调控Hippo/YAP通路发挥抑癌作用，并应用基因突变等技术探索Fbxw7泛素化调控YAP蛋白的分子机制。另一方面，我们发现miR-92a能够通过靶向作用于Fbxw7发挥促癌作用，而lncRNA CASC2能够通过CASC2/miR-367/ Fbxw7通路发挥抑癌作用。本项目研究结果不仅明确了Fbxw7的抑癌作用，而且对Fbxw7的上下游调控因子及其作用机制进行了深入探究，为临床上开发新的HCC靶向治疗药物和预后标志物提供依据。