THBS1 and neoplasm: Emerging evidence implicates a key role for platelets in site-specific neovascularization at ischemic tissues and the tumor microenvironment as they are major storage and delivery vehicles for pro- and antiangiogenic growth factors including vascular endothelial growth factor (VEGF), endostatin, and thrombospondin-1 (TSP-1), and cytokines and chemokines, such as stromal-derived factor 1 α (SDF-1α) and IL-8 among others.