EGFR and melanoma: Upregulation of various RTKs or their ligands have been reported in MAPK-inhibitor resistant melanoma, including PDGFRβ, IGF-R1, HGF, FGFR2, NRG1 and the EGFR family (EGFR, ERBB2, ERBB3, ERBB4) [112,113,114,115,116].