AXL and small cell lung carcinoma: These studies have identified several mechanisms of acquired resistance, including EGFR T790M mutation [6], [7], MET amplification [8], [9], hepatocyte growth factor (HGF) overexpression [10], loss of PTEN [11], transformation to a small cell lung cancer (SCLC) phenotype [12]–[14], epithelial-to-mesenchymal transition (EMT) [15]–[17], activation of the NFkB pathway [18], alteration of microRNA [19], and Gas6-Axl axis activation [20].