The tobacco carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) was also found to upregulate the expression of CNTN1, leading to enhanced lung cancer cells invasion via the activation of α7 nicotinic acetylcholine receptor (α7 nAChR) downstream of the AKT and extracellular signal-regulated kinase (ERK) signaling pathway [56]. This evidence concerns the gene CHRNA7 and lung carcinoma.