CHRNA7 and lung carcinoma: The protein kinase C (PKC), mitogen-activated protein kinase (MEK)/extracellular signal-regulated kinase (ERK), and phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT)/mammalian target of rapamycin (mTOR) pathways are the main intracellular mediators of the α7-nAChR signaling responsible for growth, migration, and invasion of lung cancer cells (Tsurutani et al., 2005; Arredondo et al., 2006b; Carlisle et al., 2007; Chernyavsky et al., 2009; Davis et al., 2009; Mucchietto et al., 2018).