AMPK对TGF-β信号的靶向调控在抑制胃癌转移中的作用

TGF-β play an important role in the regulation on EMT/CSC. In gastric cancer cells, TGF-β signaling is overexpressed, and it has been domonstrated to be closely associated with the invasion and metastasis. AMPK is emerging as an interesting metabolic tumor suppressor, and it has attracted considerable attention as a target for anticancer. However, the relationship between these two signaling pathway remains unclear, and their role in the development of tumor is elucidated. According to our preliminary data, the activity of AMPK is declined in gastric cancer cell comparing to adjacent mmucosa, and AMPK activation can attenuate the phosphorylation and activity of Smad3 mediated by TGF-β. It is appeared that the activation of TGF-β signaling pathway is connected wtih AMPK activation. Therefore, we have a hypothesis that the change of AMPK activity can be used as a control valve to regulate TGF-βsignal flow, to stop the pregression of gastric carcinoma. But in the development of gastric cancer, decreased AMPK activity could leads to the emerging TGF-β activity, strengthen the cancer cell invasion and metastasis ability. in this study, in order to identify the possibility that AMPK inactivation and TGF-β signaling is involved in the invasion and metastasis of gastric cancer, we proposed clinical pathology study, vitro cell experiment and tumor formation in nude mice. Hence, we attempt to assess the direct relationship between TGF-β signal and the activity of AMPK, and to explore the mechanism by which TGF-β signaling can be regulated by AMPK activity. Therefore, our study will be helpful to clarify the mechanism of tumorgenesis and metastasis in gastric cancer, and offer a new target for the treatment of advanced gastric cancer.

TGF-β信号作为EMT/CSC的关键调节因子，在胃癌中异常活跃，与胃癌的高侵袭、高转移有密切关系，而AMPK作为肿瘤抑制因子，日益受到重视。但这两条重要信号通路之间的相互作用，及对肿瘤发展的影响，尚未见报道。我们前期研究显示AMPK活性在胃癌细胞中下降；当胃癌细胞中AMPK被激活后，TGF-β所诱导的下游分子Smad3磷酸化及活化明显下降。因此，我们假设AMPK的活性变化可以作为一种阀门，控制TGF-β信号流量，以阻遏胃癌进展；但胃癌发展中，AMPK的活性下降导致TGF-β信号异常活跃，使癌细胞的侵润转移能力加强。据此，我们拟通过临床病理、体外细胞实验和裸鼠成瘤实验探讨胃癌的侵润转移是否与AMPK活性受抑、TGF-β信号上升有关性，确立TGF-β信号与AMPK活性的关系；并研究AMPK调节TGF-β信号转导的可能机制。本研究将有助于阐明胃癌发展和转移的分子机制，为胃癌治疗提供新靶点。

癌症细胞的侵袭和转移是肿瘤向恶性方向变化的重要标志，大部分癌症患者死亡并非死于原发性癌而是转移性癌。上皮间充质转化（epithelial-mesenchymal transition, EMT）在肿瘤侵袭转移过程中起着至关重要的作用，TGF-β信号是 EMT 的主要诱导因子之一。AMPK（单磷酸腺苷活化激酶，AMP-activited Protein Kinase）是细胞内能量感受器，调控生物体内能量平衡，目前关于 AMPK 对 TGF-β诱导的 EMT 及肿瘤侵袭迁移调节的的系统性研究尚未见报道。因此，本课题研究了胃癌临床标本中，检测了p-AMPK与EMT相关蛋白的表达及其相关性。同时利用胃癌细胞模型，深入研究了AMPK激活后抑制肿瘤的EMT过程及其TGF-β自诱导过程的机制。我们的研究结果显示，AMPK激活后，不仅可以抑制由TGF-β调节的胃癌细胞的EMT过程，同时可以抑制TGF-β的产生。并且在这两个过程中，我们发现smad3是其中起着关键作用的蛋白，AMPK可以抑制其磷酸化，而抑制smad3蛋白的核内转位与启动TGF-β启动子的功能。因此，抑制smad3的磷酸化可能作为新的肿瘤治疗靶点。本课题的研究成果将为肿瘤的预后提供新的预测marker，同时smad3作为调节TGF-β转录的关键蛋白，smad3有可能在未来作为新的肿瘤转移治疗靶点。