PF4 and cancer: Prior to cancer becoming metastatic, its spread is initiated by pro-angiogenic factors consisting of vascular endothelial growth factor (VEGF) receptors, fibroblast growth factor (FGF), platelet derived growth factors (PDGF), epidermal growth factor (EGF), thymidine phosphorylase (TP), neuropeptide Y4 (NY4), and platelet factor 4 (PF4), etc. [8,9].