CHRNA7 and non-small cell lung carcinoma: Nicotine and NNK increase the NSCLC risk by upregulating a network of signaling pathways facilitating proliferation, metastasis, and angiogenesis, and inhibiting apoptosis through activation of the nicotinic acetylcholine receptor (α7nAChRs) and beta-adrenergic receptor (β-AdrR) [6,7,8].