CHRNA5 and lung carcinoma: This region, spanning the nicotinic acetylcholine receptors, CHRNA5, and CHRNA3, and CHRNB4 and was also identified in a recent GWAS of dichotomized smoking intensity [45], and in two genome-wide association scans of lung cancer [46], [47], It was unclear whether the association between SNPs in this region and lung cancer was due to a genetic effect on smoking behavior, an independent effect on lung carcinogenesis, or both [48].