GAS6 and neoplasm: Growth factors that are enriched in the tumor microenvironment (TME) include TGF-β, Ca2+, hematopoietin, bone morphogenic proteins (BMPs), CXCL12, annexin A2 (ANXA2), and insulin-like growth factor (IGF) [2,82,84,85], among which TGF-β and BMPs play central roles in holding PCa cells in dormancy via the tyrosine-protein kinase receptor, UFO (Axl)/growth arrest specific 6 (Gas6) axis [86,87].