GAS6 and neoplasm: The GAS6/AXL axis regulates many tumor immune-related biomolecules, e.g., major histocompatibility complex I (MHC-I) and programmed death ligand-1 (PD-L1) in tumor cells (24), and the levels of secreted anti-inflammatory cytokines such as IL-4, CCL3-5 and granulocyte colony-stimulating factor (G-CSF) (81).