title: Lung cancer susceptibility in relation to combined polymorphisms of microsomal epoxide hydrolase and glutathione S-transferase P1.
abstract: Human microsomal epoxide hydrolase (mEH) catalyzes a key step in the biotransformation of benzo[a]pyrene that yields the highly mutagenic (+)-anti-7,8-diol-9,10 epoxide (BPDE). Two polymorphisms have been described in the coding region of the mEH gene (EPHX1) that produce two protein variants: 113Tyr-->113His (exon 3) and 139His-->139Arg (exon 4). We performed a case-control study among Northwestern Mediterranean Caucasians to investigate a possible association between these EPHX1 variants and lung cancer risk. Both EPHX1 polymorphisms were analyzed in a group of lung cancer patients (n=176) and in a control group of healthy smokers (n=187). The results showed a significantly decreased risk for the rare homozygous 113His/113His (adjusted odds ratio (OR): 0.44, 95% confidence interval (CI): 0.27-0.71) and 139Arg/139Arg (adjusted OR: 0.55, 95% CI: 0.33-0.91) compared with the major wild-types 113Tyr/113Tyr and 139His/139His, respectively, as the references. Thereafter, we analyzed the EPHX1 variants in combination with three glutathione S-transferase polymorphic genes (GSTM1, GSTT1, and GSTP1) and we found a significant overepresentation of cancer patients with a combination of exon 3 113Tyr/113Tyr EPHX1 and exon 5 105Ile/105Ile GSTP1 (adjusted OR: 2.34, 95% CI: 1.21-4.52). The polymorphic site within the exon 5 of GSTP1 results in a Ile-->Val substitution, and the isoleucine GSTpi isoform has been found in vitro to be less active than the valine isoform towards the conjugation of BPDE. The 113 Tyr/Tyr EPHX1 encodes for a high-activity mEH. Our results agree with these observations in vitro and suggest that a genetically determined combination of a high-activity mEH and a low-activity GSTpi may increase lung cancer risk among smokers.
authors.affiliation: Toxicology Unit, Hospital Clínic, IDIBAPS, Departament de Salut Pública, Universitat de Barcelona, Villarroel 170, 08036, Barcelona, Spain. jtofigue@medicina.ub.es
authors.forename: J
authors.initials: J
authors.lastname: To-Figueras
authors.forename: M
authors.initials: M
authors.lastname: Gené
authors.forename: J
authors.initials: J
authors.lastname: Gómez-Catalán
authors.forename: E
authors.initials: E
authors.lastname: Piqué
authors.forename: N
authors.initials: N
authors.lastname: Borrego
authors.forename: J
authors.initials: J
authors.lastname: Corbella
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D004851:Epoxide Hydrolases / Q000235:genetics; D005091:Exons; D005260:Female; D020022:Genetic Predisposition to Disease; D005838:Genotype; D005982:Glutathione Transferase / Q000378:metabolism; D006639:Histidine / Q000737:chemistry; D006720:Homozygote; D006801:Humans; D008175:Lung Neoplasms / Q000235:genetics*; D008297:Male; D008861:Microsomes / Q000378:metabolism; D008875:Middle Aged; D016017:Odds Ratio; D010641:Phenotype; D011110:Polymorphism, Genetic; D020033:Protein Isoforms; D012907:Smoking; D014443:Tyrosine / Q000737:chemistry
chemical_list: D020033:Protein Isoforms; D014443:Tyrosine; D006639:Histidine; D005982:Glutathione Transferase; D004851:Epoxide Hydrolases