AXL and neoplasm: The PtdSer, GAS6/AXL, and GAS6/MERTK signaling have been extensively studied both as a tumor survival, chemoresistance factor in the tumor cell itself where the RTKs are often overexpressed and as stimulating immunosuppression mechanisms from the normal myeloid cells infiltrating the tumor microenvironment (see refs. 31,32,58–60 for reviews).