title: Genetic polymorphism of CYP2A6 as one of the potential determinants of tobacco-related cancer risk.
abstract: Analyzing the CYP2A6 gene of subjects who showed a poor metabolic phenotype toward SM-12502, we discovered a novel mutant allele (CYP2A6*4C) lacking the whole CYP2A6 gene. Using genetically engineered Salmonella typhimurium expressing a human CYP, we found that CYP2A6 was involved in the metabolic activation of a variety of nitrosamines such as 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) contained in tobacco smoke. Taking these results into consideration, we hypothesized that the subjects carrying the CYP2A6*4C allele had lower risk of tobacco-related lung cancer. In accordance with our hypothesis, our epidemiological studies indicated that smokers homozygous for the CYP2A6*4C allele showed much lower odds ratios toward cancer risk. Other mutant alleles reducing the CYP2A6 activity, besides CYP2A6*4C, also reduced the risk of lung cancer in smokers, particularly of squamous-cell carcinoma and small-cell carcinoma, both smoking-related cancers. 8-Methoxypsoralen, an inhibitor of CYP2A6, efficiently prevented the occurrence of adenoma caused by NNK in A/J mice.
authors.affiliation: Graduate School of Pharmaceutical Sciences, Hokkaido University, Sapporo 060-0812, Japan. SNC78123@nifty.com
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Kamataki
authors.forename: Masaki
authors.initials: M
authors.lastname: Fujieda
authors.forename: Kazuma
authors.initials: K
authors.lastname: Kiyotani
authors.forename: Shunsuke
authors.initials: S
authors.lastname: Iwano
authors.forename: Hideo
authors.initials: H
authors.lastname: Kunitoh
mesh_terms: D000818:Animals; D001189:Aryl Hydrocarbon Hydroxylases / Q000037:antagonists & inhibitors / Q000235:genetics*; D065637:Cytochrome P-450 CYP2A6; D006801:Humans; D008175:Lung Neoplasms / Q000188:drug therapy / Q000201:enzymology* / Q000453:epidemiology / Q000235:genetics*; D051379:Mice; D008805:Mice, Inbred A; D006899:Mixed Function Oxygenases / Q000037:antagonists & inhibitors / Q000235:genetics*; D011110:Polymorphism, Genetic; D012307:Risk Factors; D012907:Smoking / Q000009:adverse effects / Q000235:genetics*
chemical_list: D006899:Mixed Function Oxygenases; D001189:Aryl Hydrocarbon Hydroxylases; C585710:CYP2A6 protein, human; D065637:Cytochrome P-450 CYP2A6