ERBB3 and melanoma: Not only are MAPK and PI3K pathways upregulated in resistant melanoma cells, but so are their upstream receptor tyrosine kinases (RTKs), such as the Erb-B2 receptor tyrosine kinase 3 (ERBB3), the insulin-like growth factor (IGF)-1 receptor, the hepatocyte growth factor receptor (c-MET), the epidermal growth factor receptor (EGFR), and the platelet-derived growth factor receptor α (PDGFR α) [21,22,23,24,25,26].