长链非编码RNA YWHAEP7抑制非经典Hippo信号通路的分子机制及其在结肠癌转移中的作用研究

Colon cancer metastasis is the major cause of colon cancer-related deaths. Inactivation of Hippo signaling pathway promotes colon cancer metastasis, but the mechanism underlying the inactivation remains unclear. Our previous study screened and identified a novel lncRNA YWHAEP7, the pseudogene 7 of 14-3-3ε, whose overexpression was correlated with colon cancer metastasis. Bio-function study revealed that YWHAEP7 promoted colon cancer cell metastasis by regulating YAP/TAZ. Mechanismly, we found that YWHAEP7 might interact with miR-125a and 14-3-3 protein using RIP, Mass spectrum and qRT-PCR experiments, and 14-3-3 protein was showed to be able to form a complex with α-catenin and p-YAP, leading the dephosphorylation of p-YAP followed by transporting into nucleus, and this is a key mechanism of non-canonical Hippo signaling pathway. Moreover, several literatures showed that TAZ is a direct target of miR-125a. Thus, we hypothesized that YWHAEP7 might interact with 14-3-3 protein to increase the nuclear location of YAP, and the existence of YWHAEP7-miR-125a-TAZ axis might increase the nuclear location of TAZ. We will illuminate the mechanism by which YWHAEP7 inhibits the non-canonical Hippo signaling pathway and expound the role of this mechanism in colon cancer metastasis, to provide a theoretical basis for the diagnosis and treatment of colon cancer.

结肠癌转移是患者死亡的主要原因，Hippo信号通路失活促进结肠癌转移，但其失活机制不清楚。课题组采用芯片筛选并鉴定出结肠癌转移中高表达的长链非编码RNA YWHAEP7，是14-3-3ε的假基因7。功能研究表明YWHAEP7通过调控YAP/TAZ促进结肠癌细胞转移。机制上，采用RIP、蛋白质谱、qRT-PCR等发现YWHAEP7可能与miR-125a、14-3-3蛋白结合，后者与α-catenin、p-YAP形成复合物，阻碍p-YAP去磷酸化而入核，是非经典Hippo信号通路的关键机制，文献表明TAZ是miR-125a的靶基因。因此，课题组推测YWHAEP7可能与14-3-3结合促进YAP核转位，且存在YWHAEP7-miR-125a-TAZ轴促进TAZ核转位。课题组拟采用一系列实验阐明YWHAEP7抑制非经典Hippo信号通路的分子机制及其在结肠癌转移中的作用，为结肠癌诊治提供理论依据。

结直肠癌肝转移(CRLM)是结直肠癌相关死亡的主要原因，目前仍是一个临床挑战。研究表明葡糖摄取的增加与CRLM有关。然而，长链非编码RNA (lncRNA)是否参与这些分子事件仍不清楚。本项目发现了一种lncRNA, GAL(GLUTI1 associated lncRNA)，与原发性结直肠癌(CRC)组织或匹配的正常组织相比，它在CRLM组织中上调，并与CRLM患者的总生存率相关。在功能上，GAL在体外促进CRC细胞迁移和侵袭，在裸鼠模型中增强CRC细胞从肠向肝转移的能力，因此作为一个促癌基因。在机制上，GAL与GLUT1蛋白相互作用，增加GLUT1的苏木化，抑制泛素-蛋白酶体系统对GLUT1蛋白的降解作用。GLUT1敲除(-/+)在体外抑制GAL介导的CRC细胞对葡萄糖摄取、迁移、入侵的增加，在体内抑制GAL介导的CRC细胞从肠向肝脏的转移，GLUT1的强制表达恢复了GAL敲除诱导的CRC细胞的相关生物学功能。综上所述，我们的研究结果表明GAL通过稳定GLUT1促进CRLM，提示GAL-GLUT1复合体可能作为CRLM潜在的治疗靶点。