MMP9 and neoplasm: AXL has been shown to act through several signaling pathways: activation of NF-κB and JAK/STAT leads to the regulation of immune response and suppression of inflammation [12]; in contrast, the activation of transcriptional factors SNAI1/2, ZEB2, or TWIST stimulates EMT [20, 21]; moreover, AXL mediates tumor invasion by the regulation of matrix metalloproteinase-9 (MMP9) expression [22].