FGF2 and neoplasm: Cells in the GSCs microenvironment can secret a variety of cytokines, such as vascular endothelial growth factor (VEGF), hypoxia-inducing factor (HIF), and fibroblast growth factor 2 (FGF2), to stimulate GSCs to self-renew, induce angiogenesis, recruit immune cells, and promote tumor cell invasion and metastasis (Hambardzumyan and Bergers, 2015).