EGFR and cancer: Various mechanisms which are responsible for the development of acquired resistance in cancer cells have been described, including EGFR gene mutations [6, 7], activation of other Receptors Tyrosine Kinases (RTKs), such as HER2 or MET [8–10], mutation in genes encoding key EGFR-dependent intracellular signaling transducers, such as KRAS, NRAS, BRAF, PIK3CA, MEK or ERK [11–18].