AXL and breast cancer: Among all those mechanisms, activation of alternative signaling pathways are the major focus and AXL, along with c-MET, were identified as important mechanisms of resistance of multiple tumors to TKIs [35, 36], such as non-small cell lung cancer to Gefitinib or Erlotinib [37], gastrointestinal stromal tumors to Imatinib [38], and HER2-positive breast cancer to Lapatinib [39].