MTOR and non-small cell lung carcinoma: Nicotine enhances proliferation, angiogenesis and metastasis and inhibits apoptosis/autophagy in NSCLC cells by activating nicotinic acetylcholine receptors (nAChRs), especially the α7 subunit, and its downstream signaling pathways including the proto-oncogene serine/threonine kinase (Rb-RAF1), the phosphatidylinositol-3 kinase/serine/threonine kinase (PI3K/Akt), the mammalian target of rapamycin (mTOR), the nonreceptor tyrosine/kinase focal adhesion/protein kinase (Src/FAK/PKC) and the extracellular signal-regulated kinase/mitogen-activated protein kinase (ERK/MAPK) [12].