肝癌细胞在信号传递过程中对exosomes和自噬的选择与调控

Hepatocellular carcinoma (HCC) cells can shuttle a variety of signals by an autocrine or paracrine manner to promote their proliferation and metastasis. Our previous study found that exosomes are important vectors in signal transmission in HCC cells, and HCC cell-derived exosomes can deliver miRNAs and other signal molecules to recipient cells. Further study found that Vps4A, a crucial regulator of exosomes, can function as a tumor suppressor in regulating the expression of exosomal miRNAs, which lead to the inactivation of the downstream PI3K-Akt signaling pathway. Overexpression of Vps4A can cause an up-regulation of Beclin1, and promote autophagy formation. These results suggest that the HCC cells may utilize exosomes secretion and autophagy to regulate the intercellular signal transduction. To elucidate the mechanism, we plan to carry out following researches. First, we propose to analyze the difference and significance of signals transmitted by exosomes and autophagy in HCC cells, and to study the effects on signal transduction by intervention of exosomes and/or autophagy. Next, in different tumor microenvironment, we will further explore the selection manner and significance on exosomes and autophagy in the signal transmission of HCC cells. Ultimately, the key regulators will be sorted and filtered to clarify the modulation mechanism. This project will lay a foundation for a new treatment of HCC by targeting the intercellular signal transduction.

肝癌细胞可通过自分泌或旁分泌的方式相互传递信号以促进其增殖和转移。我们前期研究发现，exosomes是肝癌细胞信号传递的重要载体，肝癌源性exosomes可携带miRNAs等信号分子至受体细胞内；进一步研究发现，exosomes关键调控分子Vps4A可作为抑癌基因调控exosomes中miRNAs的表达，并引起下游PI3K-Akt信号通路失活；过表达Vps4A，可引起Beclin 1上调，促进自噬形成。提示肝癌细胞可能通过exosomes分泌和自噬共同调控细胞间信号传递。为进一步揭示该作用机制，本课题拟开展下列研究：①分析肝癌细胞中exosomes和自噬所传递信号的差异和意义，研究干预exosomes和/或自噬对信号传递的影响；②不同肿瘤微环境中，肝癌细胞信号传递时对exosomes和自噬的选择方式和意义，筛选出关键调控分子，阐明其调节机制。为研究靶向细胞间信号传递的肝癌治疗方法奠定基础。

Exosomes是肝癌细胞信号传递的重要载体，可通过自分泌或旁分泌的方式相互传递信号以促进肝癌增殖和转移。前期研究发现，exosomes关键调控分子Vps4A参与调控exosomes中miRNAs的分泌和摄取。本研究发现Vps4A与p62存在相互作用，表明exosomes分泌和自噬之间存在相互作用。血管生成相关蛋白Angpt2参与exosomes分泌和自噬的调控，下调Angpt2，可引起自噬标志物LC3-Ⅱ和exosomes分泌相关蛋白Rab-27a的上调；自噬还可调控Angpt2经由exosomes分泌。由于β-catenin在肝癌的发生发展中扮演着重要角色，我们进一步研究发现，Vps4A能够通过与CHMP4B以及β-catenin结合而参与调节β-catenin的细胞膜分布以及外泌体分泌，并进一步通过影响β-catenin的活性调节肝癌细胞的EMT以及迁移、侵袭等过程。另外，我们确定了肝癌细胞能够分泌含有β-catenin的外泌体，而且合并转移的肝癌患者血清外泌体中β-catenin的蛋白水平显著下调。这提示了外泌体中β-catenin的表达水平可以作为预测肝癌患者转移和预后的生物标志物。所以，本研究进一步揭示了 Vps4A 在肝癌中发挥抑癌作用的机制，为预测肝癌患者复发转移提供了潜在方法和理论依据。