AXL and cancer: The aberrant activation of receptor tyrosine kinases MET and AXL, or MET amplification, is a major cause of the poor prognosis of RCC, as they are potent activators of cell proliferation and survival pathways and the development of bone metastases; most importantly, their activity helps cancer cells to bypass the growth-inhibitory effect of VEGFR-TKI sunitinib [41,42,43,44,45].