AXL Receptor Tyrosine Kinase is also known as Tyrosine-protein kinase receptor UFO, which belongs to the protein kinase superfamily, Tyr protein kinase family and AXL/UFO subfamily. AXL contains two fibronectin type-III domains, two Ig-like C2-type (immunoglobulin-like) domains and one protein kinase domain. AXL is highly expressed in metastatic colon tumors. AXL is activated by GAS6-binding and subsequent autophosphorylation. AXL is involved in signal transduction from the extracellular matrix into the cytoplasm by binding growth factors, and thus implicated in the stimulation of cell proliferation.