慢性应激状态下肿瘤组织内上皮-间充质转化的机制研究

The epithelial-mesenchymal transition (EMT) plays a critical role in the initiation of tumor metastasis. Frequently, cancer exposes patients to chronic psychological stressful situations, which causes the elevated levels of stress-related hormones like norepinephrine (NE) in the body. In our previous study, it was observed that NE could directly induce EMT of tumor cells in vitro through promoting expression of transforming growth factor beta (TGF-β). However, it has not been confirmed how chronic stress affects EMT in vivo. NE facilitates the expression of Lysyl oxidase (LOX) by up-regulating hypoxia-inducible factor 1α (HIF-1α). It was reported that LOX could induce the remodeling of extracellular matrix thus promoting the EMT of tumor cell. Therefore, we speculate that under the state of chronic stress in vivo, NE could directely promote the occurence of EMT through TGF-β. This is the one hand. On the other hand, NE could promote extracellular matrix remodeling through up-regulating LOX, which would further facilitate the process of EMT. In this project, we intend to establish tumor-bearing mice models to mimic the chronic stress state of cancer patients, to explore the effects and the underlying mechanisms of chronic stress on EMT in vivo. So far as we know, there is no literature reported regarding EMT from this perspective.

上皮-间充质转化（EMT）是肿瘤细胞转移过程的启动环节。肿瘤患者常处于慢性心理应激状态，体内以去甲肾上腺素（NE）为代表的压力相关激素水平升高。我们前期研究发现，NE能通过促进肿瘤细胞表达TGF-β，直接诱导体外肿瘤细胞发生EMT。然而体内环境中慢性应激对EMT的作用及机制，目前尚未见报道。NE可通过上调乏氧诱导因子HIF-1α促进赖氨酰氧化酶（LOX）的表达。文献报道，LOX可诱导细胞外基质重塑，继而促使肿瘤细胞发生EMT。因此，我们完全有理由推测，在体内慢性应激环境下NE可通过TGF-β直接促进肿瘤细胞发生EMT；另一方面通过上调LOX促进细胞外基质重塑，进一步促进EMT的发生。本项目拟模拟肿瘤患者所处的“慢性应激状态”构建荷瘤小鼠模型，观察慢性应激对体内肿瘤细胞EMT的作用，并探讨其可能的机制。据我们所知，目前国内外尚未见从这一角度研究EMT的报道。

上皮-间充质转化（EMT）是肿瘤细胞转移过程的启动环节。肿瘤患者常处于慢性心理应激状态，体内以去甲肾上腺素（NE）为代表的压力相关激素水平升高。我们前期研究发现，NE能通过促进肿瘤细胞表达TGF-β，直接诱导体外肿瘤细胞发生EMT。然而体内环境中慢性应激对EMT的作用及机制，目前尚不清楚。本项目探讨了细胞外基质重塑和microRNA在慢性应激促进肿瘤细胞EMT过程中的作用。我们发现，慢性应激可下调肿瘤微环境中miR-337-3p的表达，从而激活STAT3信号通路促进肿瘤细胞EMT的发生，增强肿瘤细胞的迁移和转移的能力。然而，赖氨酰氧化酶介导的细胞外基质重塑可能并非其中的关键机制。普萘洛尔作为βAR阻滞剂，不仅可以拮抗慢性应激作用，其本身就具有抑制EMT的作用，具体机制为：普萘洛尔通过下调肿瘤细胞miRNA-499-5p的表达，增加SOX6的表达，削弱肿瘤细胞迁移、侵袭和转移能力。此外，我们还发现NE激活β-肾上腺素能信号通路上调乏氧诱导因子-1α、丙酮酸脱氢酶激酶、乳酸脱氢酶A、葡萄糖转运体-1等糖酵解相关蛋白的表达，诱导肿瘤细胞的葡萄糖代谢重编程，导致化疗耐药。慢性应激还可产生免疫抑制性肿瘤微环境，削弱抗肿瘤免疫。总之，本项目的开展从三个方面进一步揭示了慢性应激及应激相关激素与肿瘤进展的关系。普萘洛尔可拮抗慢性应激促肿瘤进展的作用，将为临床转化和肿瘤联合治疗提供了重要的基础证据支撑。