AXL and acute lymphoblastic leukemia: MerTK, a receptor tyrosine kinase of the TAM (TYRO3, AXL, and MERTK) family, is over-expressed or ectopically expressed in a wide variety of cancers [1,2], including acute lymphoblastic leukemia (ALL) [3], non-small cell lung cancer (NSCLC) [4], melanoma [5], prostate cancer [6], glioblastoma [7], etc. In fact, MerTK mediates the activation of several canonical oncogenic signaling pathways in cancer cells [8,9].