PGF and neoplasm: Under the conditions of tumor angiogenesis, the process of new vessel formation is augmented by the preponderance of pro-angiogenic factors such as vascular endothelial growth factor (VEGF), placental growth factor (PlGF), and fibroblast growth factor (FGF), compared to anti-angiogenic factors such thrombospondin, angiostatin, endostatin, canstatin, and tumstatin [4].