VEGFA and neuroblastoma: A hypoxia-driven VEGF/Flt-1 autocrine loop acts together with hypoxia inducible factor-1 alpha (HIF-1α) through a mitogen-activated protein kinase and extracellular signal-regulated kinase-1/2-mediated pathway in neuroblastoma SK-N-BE2 cell line resulting in tumor cell survivability, multiple drug resistance, and neuroblastoma vascularity [13].