Abstract
In vascular sprouting, tip endothelial cells (ECs) express delta-like 4 (DLL4), and stalk ECs express neurogenic locus notch homolog protein 1 (NOTCH1). The DLL4/NOTCH1 signaling regulates EC migration and proliferation in angiogenesis. Steppogenin (2), a flavanone isolated from Morus alba L., has a significant inhibitory property against DLL4 in ECs. This study aimed to identify natural compounds that can inhibit the DLL4/NOTCH1 signaling pathway in the presence of VEGF in ECs. Ten natural compounds including flavanone derivatives were screened. 2 inhibited DLL4 and NOTCH1 activities. However, sanggenon F (4) only suppressed DLL4 activity, and dehydrovomifoliol (9) inhibited NOTCH1 activity alone. The inhibitory effects of sanggenon F (4) and steppogenin (2) against EC migration was better than those of dehydrovomifoliol (9). However, EC proliferation was suppressed by steppogenin (2), sanggenon F (4), and dehydrovomifoliol (9). Therefore, DLL4 had a better regulatory effect on EC migration than NOTCH1. Dehydrovomifoliol inhibited EC sprouting by 60% compared with VEGF alone. Compared to 9, 2 and 4 showed more inhibitory activity on 3D sprouting ability, thereby indicating that DLL4 activity strongly mediates EC sprouting in angiogenesis. DLL4 and NOTCH1 inhibition by steppogenin significantly enhanced antiangiogenic activity. Further, DLL4 and NOTCH1 inhibition might be more efficient than DLL4 or NOTCH1 inhibition alone for treating angiogenic diseases, such as cancer.