DLL4 and glioblastoma: In addition to the inhibition of VEGF, downregulation of a series of other key signaling factors implicated in multiple stages of angiogenesis, including the nuclear factor-κB (NF-κB), matrix metalloproteinases (MMPs) such as MMP-2 and MMP-9, and delta-like canonical Notch ligand 4(Dll4)/Notch-1, has been demonstrated to contribute to the anti-angiogenesis effect of As2O3 in several cancer cell lines derived from various types of tumors, including GBM [88,90,91], although further studies still be needed to provide concrete evidence of the anti-angiogenesis effect of As2O3 in GBM.