HGF and nonpapillary renal cell carcinoma: The c-MET RTK is a proto-oncogene known to derive the invasion and metastasis of various cancers.215,217 In clear cell renal cell carcinoma (ccRCC), GAS6/AXL signaling enhances cellular invasion through lateral stimulation of c-MET, mediated by another proto-oncogene, SRC.57 AXL and c-MET crosstalk has been observed in triple-negative breast cancer (TNBC), where exposure to hepatocyte growth factor (HGF) leads to phosphorylation of both c-MET and AXL.