Contribution of nicotine acetylcholine receptor polymorphisms to lung cancer risk in a smoking-independent manner in the Japanese

Recent genome wide association (GWA) studies on European and American populations revealed association with lung cancer risk of single-nucleotide polymorphisms (SNPs) in the locus containing two nicotine acetylcholine receptor (CHRNA) genes, whose involvement in tobacco addiction had been indicated. Association with lung cancer risk in smokers was consistently, but that in non-smokers as well as that with smoking behavior was inconsistently, observed in these studies. To obtain further information on the significance of CHRNA SNPs in lung cancer risk, association of seven SNPs in this locus with lung cancer risk as well as smoking status was examined in a Japanese population by a case-control study of 1250 cases (562 adenocarcinoma, 391 squamous cell carcinoma and 297 small cell carcinoma) and 936 controls. The frequency of the haplotype consisting of minor alleles for three SNPs, rs8034190, rs16969968 and rs1051730, which had been defined as a susceptible haplotype in the GWA studies, was much lower in the Japanese population (0.013) than in European and American populations (0.3-0.4). However, this haplotype was significantly associated with lung cancer risk also in Japanese (odds ratio = 2.3, 95% confidence interval = 1.5-3.7, P = 0.00028, respectively). The association was observed both in smokers and non-smokers and in all histological types of lung cancers. Individuals with this haplotype showed higher smoking doses than those without; however, the difference was not statistically significant. These results strongly indicate that CHRNA SNPs confer lung cancer susceptibility in a small subset of Japanese in a smoking-independent manner.