PROK2 and neoplasm: Many factors present in the TME, including transforming growth factor beta (TGF-β), cytokines (IL-10 and IL-1β), members of the VEGF, plateled-derived growth factor (PDGF), FGF, angiopoietin families, Bv8/PROK2, and hypoxia-inducible factor (HIF)-1α, provide molecular support to tumor growth and progression [27,28,29,30].