PGF and glioblastoma: Given that VEGF plays a pivotal role in tumor angiogenesis in GBM, other angiogenic factors, including fibroblast growth factor 2 (FGF2; also known as basic fibroblast growth factor, bFGF) [7], placental growth factor (PLGF) [8], platelet-derived growth factor (PDGF) [9], angiopoietin-1 (ANGPT1) [10–13], angiopoietin-2 (ANGPT2) [14–17], and Ephrin A2 (EphA2) [18–20] are also involved.