GAS6 and neoplasm: This may help explain why osteoblasts can both promote tumor cell growth (through the action of interleukin-1-beta: IL-1β and tumor necrosis factor-alpha: TNF-α) and induce tumor cell dormancy (by secreting factors such as leukemia inhibitory factor (LIF), CXC chemokine: CXCL12, and growth-arrest-specific protein 6 (Gas6)) in the bone marrow [36,37,38,39,40].