mTORC2/Akt信号在β-catenin突变诱导的肝癌形成中的作用研究

Liver cancer is one of the most common malignant tumors. β-catenin mutation is an important driven factor in the occurrence of liver cancer. Mammalian rapamycin target complex (mTOR) can be assembled into two different complexes, mTORC1 and mTORC2. AKT is generally considered as the prominent kinase of mTORC2 and can regulate mTORC1 signaling. Furthermore, two kinds of AKT isoforms called AKT1 and AKT2 expressed in liver. Recent evidence showed that mTORC1 played a key role in the formation of liver cancers induced by β-catenin mutation. However, the role of mTORC2 during the formation of liver cancers induced by β-catenin mutation remains unknown. In our recent studies, we found the formation of liver cancers induced by c-Met/β-cateninΔN90 or YapS127A/β-cateninΔN90 significantly delayed by deletion of Rictor, the unique subunit of mTORC2 in mice liver. Moreover, deletion of Akt1 in mice liver did not affect c-Met/β-cateninΔN90 or YapS127A/β-cateninΔN90 induced liver cancers development. Hence, we hypothesize that the formation of liver cancer induced by β-catenin mutation requires the activation and participation of mTORC2 signaling, and AKT2 is likely to play a key role in this process. In this project, we will systematically characterize the role of mTORC2/Akt signaling in β-catenin-driven liver cancer development based on mice models via hydrodynamic tail vein injection and cell experiments. The study will provide novel mechanistic insight into the functional role of mTORC2 signaling in β-catenin-driven liver cancer development. It will also provide strong evidence for the development of novel and effective molecular targeted therapy for liver cancer.

肝癌是最常见的恶性肿瘤之一。哺乳动物雷帕霉素靶点复合物(mTOR)包括mTORC1和mTORC2两种复合物，在功能上与AKT紧密关联，并且AKT在肝脏中存在AKT1和AKT2两种表达形式。研究表明mTORC1在β-catenin突变诱导的肝癌形成中具有重要作用，然而mTORC2在其中的作用尚不清楚。我们前期实验结果表明，在小鼠肝脏中敲除mTORC2特异性亚基Rictor后，显著延缓了β-catenin突变诱导的肝癌形成，而在小鼠肝脏内敲除Akt1后对上述肝癌的形成并不产生影响。因此，我们提出假设：β-catenin突变诱导的肝癌形成需要mTORC2信号的激活和参与，并且AKT2在其中具有关键性的作用。本课题拟结合动物模型和细胞实验等方法，以mTORC2和AKT为主要研究对象，阐明mTORC2信号在β-catenin突变诱导的肝癌形成中的作用及机制，为探索开发新型治疗肝癌的方法提供理论依据。

背景与目的：肝癌是最常见的消化系统恶性肿瘤之一。哺乳动物雷帕霉素靶点复合物(mTOR)包括mTORC1和mTORC2两种复合物，在功能上与AKT紧密关联，并且AKT在肝脏中存在AKT1和AKT2两种表达形式。研究表明mTORC1在β-catenin突变诱导的肝癌进展中具有重要作用，然而mTORC2在其中的作用尚不清楚。哺乳动物雷帕霉素复合物2靶点(mTORC2)通过调节多种AGC激酶，特别是AKT蛋白，与多种肿瘤进展有关。在肝脏中，AKT1和AKT2广泛表达。而Rictor是mTORC2的独特亚基。本项目旨在验证 mTORC2/Akt信号是否与β-catenin突变诱导的致癌作用有关，以及肝脏中哪种形式的Akt在β-catenin突变诱导的肝癌发生发展中是必需的。.方法：我们通过在小鼠肝脏内过表达N端缺失突变形式的β-catenin（β-cateninΔN90）和c-Met或点突变形式的Yap（YapS127A）协同诱导小鼠β-catenin突变诱导的肝癌形成。我们在过表达β-cateninΔN90的肝癌细胞中分别单独或联合抑制Rictor、Akt1及Akt2，并在Rictor、Akt1及Akt2转基因小鼠中进行肝细胞性单独或联合敲除，观察Rictor、Akt1及Akt2对β-catenin突变诱导的肝癌的影响。此外，我们还在体内外实验中使用同时靶向 mTORC1和mTORC2的药物MLN0128，评估该药物对β-catenin突变诱导的肝癌的抑制效果。.重要结果：我们发现mTORC2信号在β-catenin突变诱导的肝癌中被激活，并且Akt的磷酸化/激活水平明显升高。体内外实验证实Rictor的敲除显著抑制了β-catenin突变诱导的肝癌生成。我们单独抑制Akt1或Akt2都无法完全阻止β-catenin突变诱导的肝癌生成，而联合抑制Akt1及Akt2可以显著抑制β-catenin突变诱导的肝癌生长。此外，使用MLN0128可以明显抑制β-catenin突变诱导的肝癌生长。.结论：我们发现β-catenin突变诱导的肝癌形成需要mTORC2信号的激活和参与，AKT1与AKT2协同作用参与β-catenin突变诱导的肿瘤发生发展过程。同时靶向于mTORC1和mTORC2的药物对β-catenin突变诱导的肝癌形成具有抑制作用。