EGFR and nonpapillary renal cell carcinoma: Other contributors to the development of ccRCC include key signal transduction pathway PI3K/Akt/mTOR, HIF-1α, HIF-2α, VEGF, EGFR, carbonic anhydrase-IX (CA-IX), GLUT transporters, transforming growth factor-(TGF)-α, TGF-β, and Notch [94,95].