Association of CYP2A6 gene deletion with cigarette smoking status in Japanese adults.

backgroundGenetic variation of CYP2A6 is shown to alter nicotine metabolism. This study was developed to investigate the genetic influence of the whole deletion-allele of CYP2A6 on active and passive smoking behavior.

methodsTwo hundred and forty Japanese adults, who visited Aichi Cancer Center as outpatients, were genotyped for the wild-type (CYP2A6*1A, CYP2A6*1B) and the whole deletion-type (CYP2A6*4C) polymorphism of CYP2A6. Information about active and passive smoking status was obtained by a self-administered questionnaire. Genetic influence of CYP2A6 polymorphism on smoking behavior was evaluated using the Mantel extension test.

resultsThe frequency of the deletion allele was 18%. All 8 subjects carrying two deletion alleles had no smoking habit, and the homozygous deletion genotype showed a tendency to correlate with active smoking status after adjustment for sex and age (p = 0.054). However, the proportion of never smokers among heterozygous subjects was almost the same as among subjects carrying no deletion allele (54% and 58%, respectively). Furthermore, CYP2A6 genotypes were correlated neither with the number of cigarettes smoked per day nor with the age at starting smoking (p = 0.364 and 0.880, respectively). Among never smokers, CYP2A6 genotypes were not correlated with exposure to passive smoking at home or in the workplace (p = 0.623 and 0.484, respectively).

conclusionDespite the possible protection against active smoking behavior in subjects homozygous for the deletion allele, the CYP2A6 polymorphism has only a limited impact on public health because no protective effect was found in heterozygous subjects.