Case Cardiovascular Research Institute and Harrington Heart & Vascular Institute, University Hospitals Case Medical Center, Cleveland, Ohio 44106; Department of Medicine, Case Western Reserve University School of Medicine and University Hospitals Case Medical Center, Cleveland, Ohio 44106.
Case Cardiovascular Research Institute and Harrington Heart & Vascular Institute, University Hospitals Case Medical Center, Cleveland, Ohio 44106.
J Biol Chem. 2014 Apr 25;289(17):12016-12028. doi: 10.1074/jbc.M113.530956. Epub 2014 Mar 5.
Regulation of endothelial cell biology by the Notch signaling pathway (Notch) is essential to vascular development, homeostasis, and sprouting angiogenesis. Although Notch determines cell fate and differentiation in a wide variety of cells, the molecular basis of upstream regulation of Notch remains poorly understood. Our group and others have implicated the Krüppel-like factor family of transcription factors as critical regulators of endothelial function. Here, we show that Krüppel-like factor 4 (KLF4) is a central regulator of sprouting angiogenesis via regulating Notch. Using a murine model in which KLF4 is overexpressed exclusively in the endothelium, we found that sustained expression of KLF4 promotes ineffective angiogenesis leading to diminished tumor growth independent of endothelial cell proliferation or cell cycling effects. These tumors feature increased vessel density yet are hypoperfused, leading to tumor hypoxia. Mechanistically, we show that KLF4 differentially regulates expression of Notch receptors, ligands, and target genes. We also demonstrate that KLF4 limits cleavage-mediated activation of Notch1. Finally, we rescue Notch target gene expression and the KLF4 sprouting angiogenesis phenotype by supplementation of DLL4 recombinant protein. Identification of this hitherto undiscovered role of KLF4 implicates this transcription factor as a critical regulator of Notch, tumor angiogenesis, and sprouting angiogenesis.
Notch 信号通路（Notch）对血管发育、稳态和出芽血管生成的内皮细胞生物学的调节对于血管生成至关重要。尽管 Notch 在各种细胞中决定细胞命运和分化，但 Notch 的上游调节的分子基础仍知之甚少。我们的研究小组和其他研究小组已经表明，Krüppel 样因子家族转录因子是内皮功能的关键调节因子。在这里，我们表明 Krüppel 样因子 4（KLF4）通过调节 Notch 来调节出芽血管生成。使用一种在血管内皮细胞中特异性过表达 KLF4 的小鼠模型，我们发现持续表达 KLF4 促进无效的血管生成，导致肿瘤生长减少，而不影响内皮细胞增殖或细胞周期效应。这些肿瘤具有增加的血管密度，但灌注不足，导致肿瘤缺氧。从机制上讲，我们表明 KLF4 差异调节 Notch 受体、配体和靶基因的表达。我们还证明 KLF4 限制 Notch1 的切割介导的激活。最后，我们通过补充 DLL4 重组蛋白来挽救 Notch 靶基因表达和 KLF4 出芽血管生成表型。该研究发现了 KLF4 的这一迄今为止尚未被发现的作用，表明该转录因子是 Notch、肿瘤血管生成和出芽血管生成的关键调节因子。
