Regeneron Pharmaceuticals Inc., Tarrytown, New York.
Cancer Res. 2018 May 1;78(9):2370-2382. doi: 10.1158/0008-5472.CAN-17-2728. Epub 2018 Feb 15.
Angiogenesis involves dynamic interactions between specialized endothelial tip and stalk cells that are believed to be regulated in part by VEGF and Dll4-Notch signaling. However, our understanding of this process is hampered by limited knowledge of the heterogeneity of endothelial cells and the role of different signaling pathways in specifying endothelial phenotypes. Here, we characterized by single-cell transcriptomics the heterogeneity of mouse endothelial cells and other stromal cells during active angiogenesis in xenograft tumors as well as from adult normal heart, following pharmacologic inhibition of VEGF and Dll4-Notch signaling. We classified tumor endothelial cells into three subpopulations that appeared to correspond with tip-like, transition, and stalk-like cells. Previously identified markers for tip and stalk cells were confirmed and several novel ones discovered. Blockade of VEGF rapidly inhibited cell-cycle genes and strongly reduced the proportion of endothelial tip cells in tumors. In contrast, blockade of Dll4 promoted endothelial proliferation as well as tip cell markers; blockade of both pathways inhibited endothelial proliferation but preserved some tip cells. We also phenotypically classified other tumor stromal cells and found that tumor-associated fibroblasts responded to antiangiogenic drug treatments by upregulating hypoxia-associated genes and producing secreted factors involved in angiogenesis. Overall, our findings better define the heterogeneity of tumor endothelial and other stromal cells and reveal the roles of VEGF and Dll4-Notch in specifying tumor endothelial phenotype, highlighting the response of stromal cells to antiangiogenic therapies. These findings provide a framework for defining subpopulations of endothelial cells and tumor-associated fibroblasts and their rapid changes in gene expression following antiangiogenic treatment. .
血管生成涉及专门的内皮尖端和茎细胞之间的动态相互作用，据信这些相互作用部分受到 VEGF 和 Dll4-Notch 信号的调节。然而，我们对这个过程的理解受到内皮细胞异质性和不同信号通路在指定内皮表型中的作用的知识有限的限制。在这里，我们通过单细胞转录组学对在异种移植肿瘤中活跃血管生成期间以及在成年正常心脏中，通过 VEGF 和 Dll4-Notch 信号的药理学抑制后，小鼠内皮细胞和其他基质细胞的异质性进行了特征描述。我们将肿瘤内皮细胞分为三个亚群，这些亚群似乎与尖端样、过渡样和茎样细胞相对应。先前鉴定的尖端和茎细胞标记物得到了证实，并发现了几个新的标记物。VEGF 的阻断迅速抑制了细胞周期基因，并强烈降低了肿瘤中内皮尖端细胞的比例。相比之下，Dll4 的阻断促进了内皮细胞的增殖以及尖端细胞标记物的表达；两种途径的阻断抑制了内皮细胞的增殖，但保留了一些尖端细胞。我们还对其他肿瘤基质细胞进行了表型分类，发现肿瘤相关成纤维细胞通过上调与缺氧相关的基因和产生参与血管生成的分泌因子来对血管生成抑制药物治疗做出反应。总体而言，我们的研究结果更好地定义了肿瘤内皮细胞和其他基质细胞的异质性，并揭示了 VEGF 和 Dll4-Notch 在指定肿瘤内皮表型中的作用，突出了基质细胞对血管生成抑制治疗的反应。这些发现为定义内皮细胞和肿瘤相关成纤维细胞的亚群以及在抗血管生成治疗后它们的基因表达的快速变化提供了一个框架。
