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Clinical Trial of 2-Phenethyl Isothiocyanate as an Inhibitor of Metabolic Activation of a Tobacco-Specific Lung Carcinogen in Cigarette Smokers.

ABSTRACT: 2-Phenethyl isothiocyanate (PEITC), a natural product found as a conjugate in watercress and other cruciferous vegetables, is an inhibitor of the metabolic activation and lung carcinogenicity of the tobacco carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) in F344 rats and A/J mice. We carried out a clinical trial to determine whether PEITC also inhibits the metabolic activation of NNK in smokers. Cigarette smokers were recruited and asked to smoke cigarettes containing deuterium-labeled [pyridine-D4]NNK for an acclimation period of at least 1 week. Then subjects were randomly assigned to one of two arms: PEITC followed by placebo, or placebo followed by PEITC. During the 1-week treatment period, each subject took PEITC (10 mg in 1 mL of olive oil, 4 times per day). There was a 1-week washout period between the PEITC and placebo periods. The NNK metabolic activation ratio [pyridine-D4]hydroxy acid/total [pyridine-D4]NNAL was measured in urine samples to test the hypothesis that PEITC treatment modified NNK metabolism. Eighty-two smokers completed the study and were included in the analysis. Overall, the NNK metabolic activation ratio was reduced by 7.7% with PEITC treatment (P = 0.023). The results of this trial, while modest in effect size, provide a basis for further investigation of PEITC as an inhibitor of lung carcinogenesis by NNK in smokers. Cancer Prev Res; 9(5); 396-405. ©2016 AACR.

SUBMITTER: Yuan JM

PROVIDER: S-EPMC4854759 | biostudies-literature | 2016 May

REPOSITORIES: biostudies-literature

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Clinical Trial of 2-Phenethyl Isothiocyanate as an Inhibitor of Metabolic Activation of a Tobacco-Specific Lung Carcinogen in Cigarette Smokers.

Yuan Jian-Min JM Stepanov Irina I Murphy Sharon E SE Wang Renwei R Allen Sharon S Jensen Joni J Strayer Lori L Adams-Haduch Jennifer J Upadhyaya Pramod P Le Chap C Kurzer Mindy S MS Nelson Heather H HH Yu Mimi C MC Hatsukami Dorothy D Hecht Stephen S SS

Cancer prevention research (Philadelphia, Pa.) 20160307 5

2-Phenethyl isothiocyanate (PEITC), a natural product found as a conjugate in watercress and other cruciferous vegetables, is an inhibitor of the metabolic activation and lung carcinogenicity of the tobacco carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) in F344 rats and A/J mice. We carried out a clinical trial to determine whether PEITC also inhibits the metabolic activation of NNK in smokers. Cigarette smokers were recruited and asked to smoke cigarettes containing deuterium-l ...[more]

PMID: 26951845

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Project description:2-Amino-9H-pyrido[2,3-b]indole (A?C) is a carcinogenic heterocyclic aromatic amine (HAA) that arises in tobacco smoke. UDP-glucuronosyltransferases (UGTs) are important enzymes that detoxicate many procarcinogens, including HAAs. UGTs compete with P450 enzymes, which bioactivate HAAs by N-hydroxylation of the exocyclic amine group; the resultant N-hydroxy-HAA metabolites form covalent adducts with DNA. We have characterized the UGT-catalyzed metabolic products of A?C and the genotoxic metabolite 2-hydroxyamino-9H-pyrido[2,3-b]indole (HONH-A?C) formed with human liver microsomes, recombinant human UGT isoforms, and human hepatocytes. The structures of the metabolites were elucidated by (1)H NMR and mass spectrometry. A?C and HONH-A?C underwent glucuronidation by UGTs to form, respectively, N(2)-(?-D-glucosidurony1)-2-amino-9H-pyrido[2,3-b]indole (A?C-N(2)-Gl) and N(2)-(?-D-glucosidurony1)-2-hydroxyamino-9H-pyrido[2,3-b]indole (A?C-HON(2)-Gl). HONH-A?C also underwent glucuronidation to form a novel O-linked glucuronide conjugate, O-(?-D-glucosidurony1)-2-hydroxyamino-9H-pyrido[2,3-b]indole (A?C-HN(2)-O-Gl). A?C-HN(2)-O-Gl is a biologically reactive metabolite and binds to calf thymus DNA (pH 5.0 or 7.0) to form the N-(deoxyguanosin-8-yl)-A?C adduct at 20-50-fold higher levels than the adduct levels formed with HONH-A?C. Major UGT isoforms were examined for their capacity to metabolize A?C and HONH-A?C. UGT1A4 was the most catalytically efficient enzyme (V(max)/K(m)) at forming A?C-N(2)-Gl (0.67 ?l·min(-1)·mg of protein(-1)), and UGT1A9 was most catalytically efficient at forming A?C-HN-O-Gl (77.1 ?l·min(-1)·mg of protein(-1)), whereas UGT1A1 was most efficient at forming A?C-HON(2)-Gl (5.0 ?l·min(-1)·mg of protein(-1)). Human hepatocytes produced A?C-N(2)-Gl and A?C-HN(2)-O-Gl in abundant quantities, but A?C-HON(2)-Gl was a minor product. Thus, UGTs, usually important enzymes in the detoxication of many procarcinogens, serve as a mechanism of bioactivation of HONH-A?C.

Dataset Information

Clinical Trial of 2-Phenethyl Isothiocyanate as an Inhibitor of Metabolic Activation of a Tobacco-Specific Lung Carcinogen in Cigarette Smokers.

Publications

Clinical Trial of 2-Phenethyl Isothiocyanate as an Inhibitor of Metabolic Activation of a Tobacco-Specific Lung Carcinogen in Cigarette Smokers.

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