Moreover, a genome-wide association study reported that the chromosome 15q25.1 region, which includes three nicotinic cholinergic receptor genes (CHRNA5, CHRNB4, CHRN) and cell proliferation gene (PSMA4), is associated with lung cancer risk in Caucasian individuals irrespective of smoking status or propensity to smoke tobacco (14). Here, CHRNB4 is linked to lung cancer.