A20 抑制肝癌细胞迁移的分子机制的研究

HCC is one of the most common malignancies globally, ranking fifth in incidence and third in cancer-related deaths. Despite the recent advance in diagnosis and treatment of HCC, it remains a highly lethal disease due to metastasis and consequent recurrence after curative therapies. Understanding the metastatic mechanisms is a prerequisite for developing targeted molecular therapy to improve patients’ survival. . Both Lab of Professor Hongyang Wang and our lab find that A20, a critical immune negative regulator, inhibits the metastasis of HCC. But the mechanism is largely unknown. . The cell motility is the basis of cancer metastasis and controlled tightly by RhoGTPase family. RAC1 is the important member of RhoGTPase family responsible for lamellipodia formation occurring at the first step of tumor cell migration in the mode of mesenchamal movement. Our preliminary research suggested that A20 inhibited the formation of ruffling lamellipodia and the activation of RAC1 in HCC cells. However, what is the direct target of A20? How does A20 modify the RAC1 modulator since it is an ubiquitin editor? Both of the questions are intriguing. . The RAC1 activation is due to RAS activation in most cancer cells. RAS can be activated either by its gene mutation or by stimulation from environmental signals , such as EGF, PDGF and HGF. The activated RAS leads to activation of PI3K/AKT, which interacts with RAC1 modulators , including GEFs, GAPs and GDIs. These RAC1 modulators directly control the RAC1 activity. Our preliminary data suggested that A20 overexpression did not influenced the activation of PI3K/AKT. In addition, our immunoprecipitation experiment showed that A20 seemed not to combine with RAC1. Therefore, the target of A20 should be located between PI3K/AKT and RAC1. That is, it may be the RAC1 modulators. . Based on all these preliminary data, we propose the hypothesis that A20 modifies certain RAC1 modulators as an ubiquitin-editor so as to inhibit the RAC1 activity and HCC cell motility.. In the present project, we will confirm that A20 restrain HCC cell motility by its inhibiting RAC1 activity. The specific RAC1 modulators will be identified and the way for A20 to modify the RAC1 modulators will be clarified.

肝癌的转移和复发是肝癌临床治疗的瓶颈问题，其分子机制的阐释是分子靶向治疗的前提和基础。我们课题组和王红阳院士课题组都研究发现：免疫负调控因子A20可以抑制肝癌转移，但是作用机制不清楚。细胞迁移是肿瘤转移的基础，其动态过程由RhoGTP酶家族严密调控，RAC1是其中重要成员。我们前期研究提示A20通过抑制RAC1活化抑制肝癌细胞的迁移，但是A20直接作用的靶分子是什么？生化实质为泛素编辑酶的A20如何对靶分子发挥作用？具体的分子机制仍然不明确。依据RAC1活化的信号通路：活化的RAS—导致PI3K/AKT活化—作用于RAC1调控因子—导致RAC1活化，我们前期研究初步锁定A20的直接作用靶点可能是RAC1调控因子。就此提出假说：A20通过泛素编辑特定的RAC1调控因子，抑制RAC1活化，进而抑制肝癌细胞迁移。本项目将阐释A20抑制肝癌转移的分子机制，为临床肝癌防治提供新的思路和理论依据。

肝癌的转移和复发是肝癌临床治疗的瓶颈问题，其分子机制的阐释是分子靶向治疗的前提和基础。既往研究发现：免疫负调控因子A20可以抑制肝癌转移，但是作用机制不清楚。我们提出研究假说：A20通过泛素编辑特定的RAC1调控因子，抑制RAC1活化，进而抑制肝癌细胞迁移。在本项目中我们研究了A20对肝癌细胞骨架运动的调控作用，研究了A20对RAC1活性的抑制作用，我们分析了A20在HGF/PI3K/AKT/RAC1信号途径中所起的调控作用，并确定A20抑制RAC1活化的靶点分子是mTORC2复合物。除此之外，我们还研究了A20调控肝癌细胞对巨噬细胞吞噬的敏感性及其机制，以及活化的巨噬细胞诱导肝癌细胞休眠的作用，并延伸研究了去泛素化酶UCHL1对非小细胞肺癌表达免疫检查点分子PD-L1的调控作用及机制。. 本项目的重要研究结果：（1）揭示A20抑制肝癌细胞迁移的分子机制：通过抑制mTORC2进而抑制RAC1活性和细胞的运动；（2）A20通过抑制肝癌细胞表达CD47分子进而抑制巨噬细胞对肝癌细胞的吞噬作用；（3）M1巨噬细胞可诱导肝癌细胞发生休眠；（3）非小细胞肺癌中UCHL1可通过AKT/NF-κB信号轴促进PD-L1的表达，进而增强肿瘤的免疫逃逸。. 总之，本研究基本阐释A20抑制肝癌转移的分子机制，为临床肝癌防治提供新的思路和理论依据。.