肿瘤细胞表达不同Notch配体对肿瘤血管的作用、意义及机制

It is generally believed that tumor angiogenesis is driven by hypoxic microenvironment - the expression of hypoxia inducible factor-VEGF signaling axis. Tumor vascular is structural abnormalities, which suggests that tumor cells could affect tumor angiogenesis and structure through other signaling pathways after they are influenced by tumor microenvironment change. Notch signal is a key signaling pathway in vascular development. Previous reports and our study suggest that tumor cells feel O2 and cytokine changes in the microenvironment, and then could regulate angiogenesis through expressing different Notch ligands. This project intends to first observe the expression of Notch ligand in different tumor cell lines to different tumor microenvironment factors. Clinical specimens are combined to determine the correlation between Notch ligand differential expression and tumor angiogenesis; Then the expressions of different Notch ligands are up-regulated or knocked down in different tumor cell lines to observe its effect on tumor angiogenesis and vascular structures; On this basis, in-depth study is carried out to explore the cellular and molecular mechanisms of different Notch ligands expressed by tumor cells affecting tumor angiogenesis and structure. The project can reveal that tumor cells could regulate tumor angiogenesis and structure through different mechanism as the microenvironment changes, and it has important theoretical significance and application value to find a new target of interfering with tumor angiogenesis.

一般认为肿瘤新生血管形成受缺氧微环境- HIF-1a表达-VEGF信号轴驱动。但肿瘤血管高度不均一并存在大量结构异常，提示肿瘤细胞自身或在感受微环境变化后，还可能通过其他途径影响肿瘤血管的形成。Notch信号是血管发育的关键途径。文献报道和我们研究提示，肿瘤细胞感受微环境的变化后，可能通过表达不同的Notch配体调控新生血管的形成。本课题拟首先观察不同肿瘤细胞系对不同微环境因素应答时，Notch配体的表达谱，结合临床标本检测，判断Notch配体差异表达与肿瘤血管形成的相关性；然后在肿瘤细胞系过表达/敲低表达不同的Notch配体，观察对新生血管形成和血管结构的影响；在此基础上，深入探讨由肿瘤细胞表达的不同Notch配体影响新生血管形成的细胞和分子机制。本课题可以揭示肿瘤细胞随着微环境变化通过不同的机制调控肿瘤新生血管形成和结构，发现干预肿瘤血管形成的新靶点，具有重要的理论意义和潜在应用价值。

DLL3是Notch配体的一种，在胚胎发育中起到了重要作用。尽管肿瘤细胞内表达的DLL3可以促进细胞增殖、抑制凋亡，但DLL3在肿瘤细胞中具体的功能与机制尚不明确。肿瘤常见的微环境包括缺氧及炎性因子的浸润。本次研究证实：路易斯肺癌（Lewis lung carcinoma，LLC）在缺氧及肿瘤坏死因子-α（tumor necrosis factor –α，TNF-α）作用下，DLL3的表达均下调。DLL3 在人非小细胞肺癌标本中高表达，在癌旁组织中不表达。LLC过表达DLL3后导致肿瘤细胞在体外增殖增加、凋亡减少，在小鼠体内成瘤速度增快。DLL3干扰自身Notch信号通路的活化，从而导致Akt磷酸化的增加，最终促进肿瘤细胞的增殖。本实验深入探讨DLL3在肿瘤细胞内的作用与机制，为我们更好的研究DLL3奠定了基础，同时为Notch信号通路的干预提供新的靶点，具有重要的理论意义和潜在应用价值。