DLL4 and neoplasm: Notably, arsenic compounds have also been considered due to their abilities to target numerous signaling molecules, including embryonic stem cell transcription factors such as Oct4, and SOX2, vascular endothelial growth factor (VEGF), hypoxia-inducible factor-1 alpha (HIF-1α), VEGF receptor 2 (VEGFR-2), Dll4, Notch-1, GS-X pumps and ABC transporters that not only regulate the growth/activities of tumor cells, including cell cycle disruption and angiogenesis, but also involved in reduced efficacy of therapeutic agents[47–49].