EGFR and lung adenocarcinoma: A signaling pathway involving EGFR, ErbB2, ErbB3, phosphatidylinositol 3-kinase (PI3K), Akt, glycogen synthase kinase 3- β (GSK3-β), and cyclin D1 is essential for the maintenance of survival, mitosis, and invasiveness of human lung adenocarcinoma cell lines as well as to evade apoptosis [47].