The localization of GSCs in close proximity to blood vessels, in perivascular niches, is crucial, as GSCs can establish a bidirectional and supportive interaction with vascular system, especially with endothelial cells, through several mechanisms that include coopting preexisting vessels and inducing angiogenesis, in order to ensure their maintenance [77] In fact, it was demonstrated that CD133+ GSCs may produce vascular endothelial growth factor (VEGF), promoting endothelial cell growth, migration and formation of vascular tubular structure in culture, and so their tumor initiating capacity. Here, VEGFA is linked to neoplasm.