EGFR and cancer: Mutations to and overexpression of EGFR commonly occurs in cancer and leads to the upregulation of the downstream PI3K/Akt/mammalian target of rapamycin (mTOR) and Raf/mitogen-activated protein kinase (Mek)/extracellular signal-regulated kinase (ERK) pathways, which promote cancer cell proliferation [43,44,45].