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S S Hecht

Publications and source records attributed to S S Hecht.

At least 91 records · Page 5Linked to original sources
PubMed1997

Differences in the urinary metabolites of the tobacco-specific lung carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone in black and white smokers.

Incidence and mortality rates for lung cancer in the United States are significantly greater in blacks than in whites. This disparity cannot be explained by differences in smoking behavior. We hypothesize that the observed racial differences in risk may be due to differences in the metabolic activation or detoxification of the tobacco-specific lung carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK). To test this, different biomarkers of NNK exposure and metabolism, including the urinary metabolite 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) and the presumed detoxification product [4-(methylnitrosamino)-1-(3-pyridyl)but-1-yl]-beta-O-D-glucosiduronic acid (NNAL-Gluc), were examined along with questionnaire data on lifestyle habits and diet in a metabolic epidemiological study of 34 black and 27 white healthy smokers. Results demonstrated that urinary NNAL-Gluc:NNAL ratios, a likely indicator of NNAL glucuronidation and detoxification, were significantly greater in whites than in blacks (P < 0.02). In addition, two phenotypes were apparent by probit analysis representing poor (ratio < 6) and extensive (ratio > or = 6) glucuronidation groups. The proportion of blacks falling into the former, potentially high-risk group was significantly greater than that of whites (P < 0.05). The absolute levels of urinary NNAL, NNAL-Gluc, and cotinine were also greater in blacks than in whites when adjusted for the number of cigarettes smoked. None of the observed racial differences could be explained by dissimilarities in exposure or other sociodemographic or dietary factors. Also, it is unlikely that the dissimilarities are due to racial differences in preference for mentholated cigarettes, because chronic administration of menthol to NNK-treated rats did not result in either increases in urinary total NNAL or decreases in NNAL-Gluc:NNAL ratios. Altogether, these results suggest that racial differences in NNAL glucuronidation, a putative detoxification pathway for NNK, may explain in part the observed differences in cancer risk.

Adult↗
PubMed1997

Gas chromatographic-mass spectrometric determination of benzo[a]pyrene and chrysene diol epoxide globin adducts in humans.

The efficacy of a newly developed gas chromatography-negative ion chemical ionization-mass spectrometry-selected ion monitoring (GC-NICI-MS-SIM) assay for measuring globin adducts of benzo[a]pyrene (B[a]P) and chrysene diol epoxides in human was evaluated. In this pilot study, smokers and nonsmokers were selected as exposed and nonexposed groups. Using [2H12]r-7,t-8,9,c-10-tetrahydroxy-7,8,9,10-tetrahydrobenzo[a]pyren e ([2H12]trans,anti-B[a]P-tetraol) as an internal standard, B[a]P-tetraols released from globin after hydrolysis and derivatization were quantified by GC-NICI-MS-SIM. Levels of trans-1,2-dihydroxy-3,4-epoxy-1,2,3,4-tetrahydrochrysene (chrysene-DE)-globin adducts were estimated by assuming that the recovery and the MS response of the perdeuterated B[a]P-tetraol internal standard reflected the recovery and MS response of chrysene tetraols. The assay was found to be reproducible and sensitive enough to detect both analytes in all samples. The mean levels of B[a]P-tetraols released from the corresponding benzo[a]pyrene diol epoxide (BPDE) globin adducts in smokers were significantly higher than those in nonsmokers, i.e., 2.6 +/- 0.6 SE fmol/mg globin (ranging from 1.2 to 7.8 fmol/mg globin) in smokers and 0.97 +/- 0.05 SE fmol/mg globin (ranging from 0.7 to 1.3 fmol/mg globin) in nonsmokers (P < 0.01). Interestingly, estimated levels of chrysene-DE-globin adducts in the same subjects were about two orders of magnitude higher than those of the globin adducts of BPDE. The mean of the chrysene-DE adducts in smokers was estimated to be 310 +/- 30 SE fmol/mg globin (ranging from 190 to 460 fmol/mg globin) and that in nonsmokers was 250 +/- 25 SE fmol/mg globin (ranging from 110 to 380 fmol/mg). Although the estimated mean of chrysene-DE adducts with globin in smokers appeared to be about 25% higher than in nonsmokers, the difference was not significant (P = 0.06). The results of this study demonstrate the feasibility of the GC-NICI-MS-SIM method for measurement of BPDE globin adducts in humans.

Benzopyrenes↗
PubMed1996

Mammary carcinogenicity of diol epoxide metabolites of benzo[j]fluoranthene in female CD rats.

The mammary carcinogenicity of two diol epoxide metabolites of the commonly occurring environmental carcinogen benzo[j]fluoranthene (BjF) was investigated by direct application to the tissue beneath the mammary glands of female CD rats. The compounds tested were trans-4,5-dihydroxy-anti-6,6a.epoxy-4,5,6,6a-tetrahydroBjF (BjF-4,5-DE) and trans-9,10-dihydroxy-anti-11, 12-epoxy-9,10,11,12-tetrahydroBjF (BjF-9,10-DE). The positive control was trans-3,4-dihydroxy-anti-1,2-epoxy-1,2,3,4-tetrahydrobenzo[c]phenanthren e (BcPDE). Groups of 20 female CD rats were maintained on AIN-76A-based high fat diet (23.5% corn oil) and at age 30 days were given three injections of 0.2 mumol of each compound in 0.1 ml dimethyl sulfoxide (DMSO), or DMSO alone, in the tissue underlying each of the three left thoracic nipples. The three right nipple areas were injected with DMSO alone. On the next day, each rat received three injections of 0.2 mumol of each compound in 0.1 ml DMSO, or DMSO alone, under each of the three left inguinal nipples, and DMSO alone under the three right nipples. The experiment was terminated after 44 weeks. BjF-9,10-DE, mean latent period 21.0 +/- 8.8 weeks, was more active than BjF-4,5-DE, mean latent period 36.2 +/- 8.0 weeks. BjF-9,10-DE induced tumors in 70% of the rats; a total of 38 fibroadenomas and eight adenocarcinomas was observed. BjF-4,5-DE induced tumors in 55% of the rats. These included 17 fibroadenomas, seven dysplastic fibroadenomas, and two adenocarcinomas. BcPDE induced tumors rapidly, with a mean latent period of 9.7 +/- 4.0 weeks. All BcPDE-treated rats had mammary tumors. A total of 46 adenocarcinomas, as well as other tumors, were observed. In the DMSO-treated rats, mammary tumor incidence was 15%. The results of this study demonstrate that BjF-9,10-DE is more carcinogenic in the rat mammary gland than BjF-4,5-DE and that low doses of both diol epoxide metabolites of BjF are effective mammary tumorigens in female CD rats maintained on a high fat diet.

Animals↗
PubMed1996

Expression of a 32 kDa protein in rat mammary tumors induced by anti-benzo[c]phenanthrene-3,4-diol-1,2-epoxide.

Racemic anti-benzo[c]phenanthrene-3,4-diol-1,2-epoxide (BcPDE) is a powerful rat mammary carcinogen and a metabolite of benzo[c]phenanthrene, a polynuclear aromatic hydrocarbon found in the environment. In elucidating potential molecular mechanisms that may play a role in the development of BcPDE-induced rat mammary tumors, we have identified a 32 kDa protein in 16 of 26 tumors analyzed but in only 1 of the 15 normal mammary tissues that were examined. The 32 kDa protein was identified with antibodies to Ets, which also recognized the 55 kDa Ets-1 protein that was expressed at similar levels in normal mammary tissues. The expression of the 32 kDa protein was also observed in mammary tumor-derived cell lines of both rat and human origin and in human melanoma, but not in normal human keratinocytes or rat fibroblast cell lines. Further characterization via 2D gels revealed that the protein exhibits a PI of 5.5. Southwestern analysis using Ets-1 target sequence revealed binding of the 55 kDa Ets-1 but not of the newly identified 32 kDa protein. Overall, the preferential expression of the 32 kDa protein in mammary tumor tissues may serve as a biomarker to follow the development of this tumor type.

Animals↗
PubMed1996

Activation of chemically diverse procarcinogens by human cytochrome P-450 1B1.

A human cytochrome P-450 (P450) 1B1 cDNA was expressed in Saccharomyces cerevisiae and the microsomes containing P450 1B1 were used to examine the selectivity of this enzyme in the activation of a variety of environmental carcinogens and mutagens in Salmonella typhimurium TA1535/pSK1002 or NM2009 tester strains, using the SOS response as an end point of DNA damage. We also determined and compared these activities of P450 1B1 with those catalyzed by recombinant human P450s 1A1 and 1A2, which were purified from membranes of Escherichia coli. The carcinogenic chemicals tested included 27 polycyclic aromatic hydrocarbons and their dihydrodiol derivatives, 17 heterocyclic and aryl amines and aminoazo dyes, three mycotoxins, two nitroaromatic hydrocarbons, N-nitrosodimethylamine, vinyl carbamate, and acrylonitrile. Among the three P450 enzymes examined here, P450 lB1 was found to have the highest catalytic activities for the activation of 11,12-dihydroxy-11,12-dihydrodibenzo[a,l]pyrene, 1,2-dihydroxy-1,2-dihydro-5-methylchrysene, (+)-7,8-dihydroxy-7,8-dihydrobenzo[a]pyrene, 11,12-dihydroxy-11,12-dihydrobenzo[g]chrysene, 3,4-dihydroxy-3,4-dihydrobenzo[c]phenanthrene, 3-amino-1,4-dimethyl-5H-pyrido[4,3-b]indole, 2-aminoanthracene, 3-methoxy-4-aminoazobenzene, and 2-nitropyrene. P450 1B1 also catalyzed the activation of 2-amino-3,5-dimethylimidazo[4,5-f]quinoline, 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline, 2-amino-3-methylimidazo[4,5-f]quinoline, 2-aminofluorene, 6-aminochrysene and its 1,2-dihydrodiol, (-)-7,8-dihydroxy-7,8-dihydrobenzo[a]pyrene, 1,2-dihydroxy-1,2-dihydrochrysene, 1,2-dihydroxy-1,2-dihydro-5,6-dimethylchrysene, 2,3-dihydroxy-2,3-dihydrofluoranthene, 3,4-dihydroxy-3,4-dihydro-7,12-dimethylbenz[a]anthracene, and 6-nitrochrysene to appreciable extents. However, P450 1B1 did not produce genotoxic products from benzo[a]pyrene, trans- 3,4-dihydroxy-3,4-dihydrobenzo[a]anthracene, trans-8,9-dihydroxy-8,9-dihydrobenzo[a]anthracene, 7,12-dimethylbenz[a]anthracene and its cis-5,6-dihydrodiol, 5-methylchrysene, 11,12-dihydroxy-11,12-dihydro-3-methylcholanthrene, 1,2-dihydroxy-1,2-dihydro-6-methylchrysene, benzo[c]phenanthrene, 2-amino-6-methyldipyridol[1,2-a:3',2'-d]imidazole, 2-acetylaminofluorene, benzidine, 2-naphthylamine, aflatoxin B1, aflatoxin G1, sterigmatocystin, N-nitrosodimethylamine, vinyl carbamate, or acrylonitrile in this assay system. P450 1B1 is expressed constitutively in extrahepatic organs, including fetal tissue samples, and is highly inducible in various organs by 2,3,7,8-tetrachlorodibenzo-p-dioxin and related compounds in experimental animal models. Thus, activation of procarcinogens by P450 lB1 may contribute to human tumors of extrahepatic origin.

Adult↗
PubMed1996

Lack of tumorigenicity of cholesterol epoxides and estrone-3,4-quinone in the rat mammary gland.

The purpose of this study is to test the long-standing hypothesis that endogenous agents found in human breast fluid and in plasma are potential initiators of breast cancer. Therefore, we evaluated the tumorigenicity in the mammary glands of female CD rats of cholestan-5 alpha,6 alpha-epoxy-3 beta-ol (cholesterol-alpha-epoxide), cholestan-5 beta,6 beta-epoxy-3 beta-ol (cholesterol-beta-epoxide), and 1,5(10)estradiene-3,14,17-trione (estrone-3,4-quinone). As a positive control, trans-3,4-dihydroxy-anti-1,2-epoxy-1,2,3,4-tetrahydrobenzo[c]phenanthren e (BcPDE) was used. Rats were fed a high-fat AIN-76A diet (23.5% corn oil) to mimic the Western dietary composition. Because literature data suggest that the endogenous agents tested in this study are weak electrophiles, the total doses of cholesterol epoxides (12.3 mumol/rat) and of estrone-3,4-quinone (30 mumol/rat)were 10- and 25- fold higher, respectively, than that of BcPDE (1.2 mumol/rat). Each agent was dissolved in DMSO, and one-sixth of the total dose was injected under each of six nipples on the right side. The thoracic glands of the rat were treated at 30 days of age, and those located in the inguinal area were treated on the following day. The experiment was terminated at 44 weeks after treatment. Consistent with our previous study, BcPDE was a strong mammary carcinogen. However, there were no differences between rats treated with DMSO alone or those receiving DMSO containing cholesterol-alpha-epoxide, cholesterol-beta-epoxide, or estrone-3,4-quinone. The results of this study clearly indicate, for the first time, that metabolites derived from cholesterol and estrone lack tumorigenic activity in the rat mammary gland, at least under the conditions of the present protocol.

Animals↗
PubMed1996

Metabolism of 5-methylchrysene and 6-methylchrysene by human hepatic and pulmonary cytochrome P450 enzymes.

The metabolism of environmentally occurring methylated polynuclear aromatic hydrocarbons by human cytochrome P450 (P450) enzymes has not been examined previously. We compared the metabolism of the tobacco smoke constituents 5-methylchrysene (5-MeC), a strong carcinogen, and 6-MeC, a weak carcinogen, in 18 hepatic and 11 pulmonary human microsomes. Major metabolites of 5-MeC were its proximate carcinogen trans-1,2-dihydroxy-1,2-dihydro-5-methylchrysene (5-MeC-1,2-diol), as well as 5-MeC-7,8-diol, bay region dihydrodiols, and phenols. 5-MeC-1,2-diol and 5-MeC-7,8-diol were formed stereoselectively, with the R,R enantiomers predominating. Major metabolites of 6-MeC were 6-MeC-1,2-diol, bay region dihydrodiols, phenols, and 6-(hydroxymethyl)chrysene. 6-MeC-1,2-diol was also formed stereoselectively in the 1R,2R configuration. All human liver samples formed the proximate carcinogenic 1,2-diols (0.2-2.3 pmol/mg protein/min for 5-MeC and 0.3-3.1 pmol/mg protein/min for 6-MeC). Comparable results were obtained in pulmonary microsomes, but the extent of metabolism was less than in the hepatic samples, and only 4 of 11 samples showed activity. Catalytic activities known to be associated with specific P450s were analyzed in each hepatic sample and correlated with levels of 5-MeC and 6-MeC metabolites in the same samples. The results of the correlation analysis indicated that P450s 1A1 and 1A2 were active in the formation of 5-MeC-1,2-diol and 6-MeC-1,2-diol, as well as several other metabolites resulting from ring oxidation. The formation of the hydroxymethyl metabolites was catalyzed by P450 3A4 (for 5-MeC) or P450s 3A4 and 1A2 (for 6-MeC). Experiments with chemical inhibitors and antibodies supported these results. The metabolism of 5-MeC and 6-MeC was also investigated using purified recombinant human P450s 1A1, 1A2, 2C10, 2D6, 2E1, 3A4, and 3A5. P450s 1A1, 1A2, and 2C10 had higher activities than the other enzymes for ring oxidation of 5-MeC and 6-MeC, whereas P450s 1A2 and 3A4 were more active than the other enzymes for methyl hydroxylation of 6-MeC. Only P450 3A4 showed substantial catalytic activity for methyl hydroxylation of 5-MeC. Collectively, the results of these studies demonstrate that P450s 1A2 and 2C10 are important catalysts of the metabolic activation of 5-MeC and 6-MeC in human liver, whereas P450 1A1 plays a major role in the metabolic activation of these compounds in human lung.

Antibodies↗
PubMed1996

Chemoprevention of lung cancer by isothiocyanates.

Naturally occurring and synthetic isothiocyanates are among the most effective chemopreventive agents known. A wide variety of isothiocyanates prevent cancer of various tissues including the rat lung, mammary gland, esophagus, liver, small intestine, colon, and bladder. Mechanistic studies have shown that the chemopreventive activity of isothiocyanates is due to favorable modification of Phase I and Phase II carcinogen metabolism, resulting in increased carcinogen excretion or detoxification and decreased carcinogen DNA interactions. In the majority of studies reported, the isothiocyanate must be present at the time of carcinogen exposure in order to observe inhibition of tumorigenesis. Our studies have focused on the naturally occurring isothiocyanates phenethyl isothiocyanate (PEITC) and benzyl isothiocyanate (BITC) as inhibitors of lung cancer. The carcinogens employed in these studies have been the major lung carcinogens in tobacco smoke- 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) and benzo[a]pyrene (BaP). Combinations of chemopreventive agents that inhibit tumorigenesis by NNK and BaP in rodents may be effective in addicted smokers. PEITC is an effective inhibitor of lung tumor induction by NNK in F-344 rats and A/J mice. BITC but not PEITC inhibits BaP induced lung tumorigenesis in A/J mice. PEITC is a selective inhibitor of the metabolic activation of NNK in the rodent lung, and studies in smokers who consumed watercress, a source of PEITC, indicate that the metabolic activation of NNK is also inhibited by PEITC in humans. Combinations of chemopreventive agents active against different carcinogens in tobacco smoke may be useful in the chemoprevention of lung cancer.

Animals↗
PubMed1996

Detection of DNA and globin adducts of polynuclear aromatic hydrocarbon diol epoxides by gas chromatography-mass spectrometry and -3H-CH3I postlabeling of released tetraols.

Gas chromatography-negative ion chemical ionization mass spectrometry--selected ion monitoring (GC-NICI-MS-SIM) was employed to detect tetramethyl ether derivatives of tetraols formed upon hydrolysis of DNA and globin adducts derived from diol epoxides of benzo[a]-pyrene (BP) and other polynuclear aromatic hydrocarbons (PAH). The tetramethyl ether derivatives could also be detected by [3H]CH3I postlabeling. The methodology involves the following steps: (1) isolation of DNA or globin; (2) mild acid hydrolysis under vacuum; (3) isolation of the resulting tetraols and derivatization to the corresponding tetramethyl ethers using methyl sulfinyl carbanion and unlabeled or 3H-labeled CH3I; (4) analysis by GC-NICI-MS-SIM or HPLC with radioflow detection. The optimum conditions for hydrolysis of adducts and derivatization of the resulting tetraols as well as the feasibility of this approach for detecting PAH adducts in mice and humans were explored. Using the set of four BP-tetraols that can be formed upon hydrolysis of adducts formed from r-7,t-8-dihydroxy-t-9,10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (anti-BPDE) or r-7,t-8-dihydroxy-c-9,10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (syn-BPDE) as models, the stability of the tetraols under the hydrolysis conditions was investigated. Adducts derived from anti-BPDE yield predominantly the stable r-7,t-8,9-c-10-tetrahydroxy-7,8,9,10-tetrahydrobenzo[a]pyrene (trans-anti-BP-tetraol), while adducts derived from syn-BPDE released cis-syn-BP-tetraol as a major hydrolysis product. Hydrolysis under vacuum significantly increased the recovery of tetraols. Conditions for derivatization of the BP-tetraols as well as tetraols derived from several other PAH anti-diol epoxides were investigated. Tetramethyl ethers proved to be superior derivatives that were stable, easy to prepare in high yields, and detectable with high sensitivity by GC-NICI-MS-SIM (1-50 fmol per injection). Alternatively, these derivatives could be detected by HPLC with radioflow detection if [3H]CH3I were employed for derivatization. The methodology was tested by comparing levels of DNA and globin adducts in mice treated with either unlabeled or 3H-labeled BP. Good agreement was obtained among the GC-NICI-MS-SIM, [3H]CH3I postlabeling, and conventional radiometric methods. Moreover, analysis of human hemoglobin by GC-NICI-MS-SIM resulted in detection of adducts derived from anti-BPDE and r-1,t-2-dihydroxy-t-3,4-epoxy-1,2,3,4-tetrahydrochrysene. The results of this study demonstrate that GC-NICI-MS-SIM of tetramethyl ethers of tetraols formed by hydrolysis of PAH diol epoxide DNA and globin adducts is a promising approach for detection and quantitation of adducts derived from a broad range of PAH.

7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide↗
PubMed1996

Liquid chromatography--electrospray ionization mass spectrometric detection of an ethenodeoxyguanosine adduct and its hemiaminal precursors in DNA reacted with alpha-acetoxy-N-nitrosopiperidine and cis-4-Oxo-2-pentenal.

N-Nitrosopiperidine, a carcinogenic cyclic nitrosamine that occurs in the diet and may be formed endogenously, is believed to be metabolically activated by alpha-hydroxylation. The DNA reactive compounds that could be formed in this process have been studied using alpha-acetoxy-N-nitrosopiperidine as a model. Previous studies have shown that 4-oxo-2-pentenal is one product of the hydrolysis of alpha-acetoxyNPIP and that it reacts with deoxyguanosine to produce 7-(2-oxopropyl)-5,9-dihydro-9-oxo-3-beta-D-deoxyribofuranosylimidazo+ ++ [1,2-a]purine (7-(2-oxopropyl)-1,N2-ethenodG). Several other products were formed in that reaction, and these have now been identified as diastereomers of 7-(2-oxopropyl)-5-hydroxy-5,6,7,9-tetrahydro-9-oxo-3-beta-D- deoxyribofuranosylimidazo[1,2-a]purine, the hemiaminal precursors to 7-(2-oxopropyl-1,N2-ethenodG. Their structures were characterized by electrospray ionization mass spectrometry (ESI-MS), and by reduction with NaBH4 followed by hydrolysis to 7-(2-hydroxypropyl)-5,6,7,9-tetrahydro-9-oxoimidazol [1,2-a]purine, which was characterized by 1H-NMR, MS, and UV. The presence of 7-(2-oxopropyl)-1,N2-ethenodG and its hemiaminal precursors in DNA reacted with either alpha-acetoxy-N-nitrosopiperidine or cis-4-oxo-2-pentenal was confirmed by LC-ESI-MS/MS. The results of this study demonstrate that ethenodG adducts and their precursors are present in DNA reacted with alpha-acetoxy-N-nitrosopiperidine, which suggests a possible basis for the unique carcinogenic properties of nitrosamine.

Acrolein↗
PubMed1996

Inhibitory effects of 6-phenylhexyl isothiocyanate on 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone metabolic activation and lung tumorigenesis in rats.

This study examined the effects of 6-phenylhexyl isothiocyanate (PHITC) on lung tumorigenesis in F344 rats induced by the tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK). Two biomarkers of NNK metabolism, 4-hydroxy-1-(3-pyridyl)-1-butanone (HPB)-releasing hemoglobin adducts and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) and its glucuronide (NNAL-Gluc) in urine, were also quantified during the course of the tumor induction experiment. Rats were divided into groups as follows: (1) NNK, 2 p.p.m. in drinking water, 60 rats; (2) NNK, 2 p.p.m. in drinking water and PHITC, 1 micromol/g NIH-07 diet, 60 rats; (3) PHITC, 1 micromol/g NIH-07 diet, 20 rats; (4) control, 20 rats. PHITC was added to the diet for 1 week prior to and during 111 weeks of NNK treatment. There were no effects of PHITC on body weight, mortality, blood chemistry or hematology. Seventy percent of the rats treated with NNK had adenoma or adenocarcinoma of the lung. In the rats treated with NNK plus PHITC, the total percent incidence of lung tumors was 26% (P < 0.01 compared with NNK). PHITC had no effect on the total incidence of exocrine pancreatic tumors induced by NNK. The rats treated with PHITC and NNK had significantly lower levels of HPB-releasing hemoglobin adducts throughout the course of the bioassay than did those treated with NNK alone and significantly higher levels of NNAL plus NNAL-Gluc excreted in urine at two time points during the bioassay. These results demonstrate that near lifetime administration of PHITC to rats strongly inhibits the metabolic activation and lung tumorigenicity of NNK.

Animals↗
PubMed1996

Synthesis of tobacco-specific N-nitrosamines and their metabolites and results of related bioassays.

Tobacco-specific N-nitrosamines (TSNA) are the most abundant, strong carcinogens in tobacco smoke. Seven TSNA have been identified in tobacco products: N'-nitrosonornicotine (NNN), N'-nitrosoanabasine (NAB), N'-nitrosoanatabine (NAT), 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL), 4-(methylnitrosamino)-4-(3-pyridyl)-1-butanol (iso-NNAL), and 4-(methylnitrosamino)-4-3-pyridyl)butyric acid (iso-NNAC). The syntheses of these compounds are reviewed. The syntheses of 14C- and 3H-labeled NNK as well as metabolites of NNK and NNN are also discussed. Comparative assays for lung tumorigenesis in female A/J mice were carried out for six of the TSNA and for two related compounds, N-nitrosodimethylamine (NDMA) and N-nitrosopyrrolidine (NPYR). They yielded the following ranking of potency: NDMA > NNK > NNAL > NPYR > NNN > NAB. Iso-NNAL and iso-NNAC were inactive. These results are also compared with previous assays of TSNA carcinogenicity in rats and hamsters.

Adenoma↗
PubMed1996

Recent studies on mechanisms of bioactivation and detoxification of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), a tobacco-specific lung carcinogen.

This article reviews recent advances in the biochemistry and molecular biology of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), a tobacco-specific pulmonary carcinogen believed to be involved in the induction of lung cancer in smokers. Several aspects of NNK bioactivation are addressed, including identification of its metabolites in laboratory animals and humans, cytochrome P450 enzyme involvement in its metabolic activation, DNA and protein adduct formation, biological significance of the major DNA adducts formed, and mutations in oncogenes from tumors induced by NNK. Collectively, the presently available data provide a reasonably clear picture of NNK bioactivation in rodents, although there are still important gaps in our mechanistic understanding of NNK-induced tumorigenesis. The studies in rodents and primates have facilitated development of methods to assess NNK bioactivation in humans, which will be applicable to studies of lung cancer susceptibility and prevention.

Animals↗
PubMed1996

The biological significance of tobacco-specific N-nitrosamines: smoking and adenocarcinoma of the lung.

In the U.S., there has been a steeper rise of the incidence of lung adenocarcinoma than of squamous cell carcinoma of the lung among cigarette smokers. Since 1950, the percentage of all cigarettes sold that had filter tips increased from 0.56 to 92% in 1980 and to 97% in 1990. The tobacco of the filter cigarettes is richer in nitrate than that of the nonfilter cigarettes manufactured in past decades. Because the smoker of cigarettes with lower nicotine yield tends to smoke more intensely and to inhale the smoke more deeply than the smoker of plain cigarettes, the peripheral lung is exposed to higher amounts of nitrogen oxides, nitrosated compounds, and lung-specific smoke carcinogens. It is our working hypothesis that more intense smoking, deeper inhalation of the smoke, and higher smoke delivery of the organ-specific lung carcinogen NNK to the peripheral lung are major contributors to the increased risk of cigarette smokers for lung adenocarcinoma. Bioassay data and biochemical studies in support of this concept are discussed.

Adenocarcinoma↗
PubMed1996

Complete inhibition of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone-induced rat lung tumorigenesis and favorable modification of biomarkers by phenethyl isothiocyanate.

Phenethyl isothiocyanate (PEITC), which occurs in certain cruciferous vegetables, was tested for its ability to inhibit lung tumorigenesis in rats induced by the tobacco-specific nitrosamine 4-(methylnitrosamino-1-(3-pyridyl)-1-butanone (NNK) in a study involving virtually lifelong administration of both compounds. In addition, two biomarkers of NNK metabolism [4-hydroxy-1-(3-pyridyl)-1-butanone-releasing hemoglobin adducts and 4-(methylnitrosamino-1-3-pyridyl-1-butanol and its glucuronide in urine] were quantified in randomly selected rats during the course of the study. The rats were assigned to groups as follows: NNK, 2 ppm in drinking water, 60 rats; NNK, 2 ppm in drinking water and PEITC, 3 micromol/g NIH-07 diet, 60 rats; PEITC, 3 micromol/g NIH-07 diet, 20 rats; and untreated controls, 20 rats. NNK was added to the drinking water for 111 weeks and PEITC to the diet for 1 prior to NNK administration and then throughout the 111-week course of treatment. There were no significant differences in body weights or survival among the groups. There were no significant effects of PEITC on blood chemistry or hematology. NNK induced lung tumors (adenoma and/or adenocarcinoma) in 70% of the rats. In the group treated with NNK plus PEITC, 5% of the rats had lung tumors, which was not different from that of control rats. PEITC also appeared to inhibit progression of benign to malignant pancreatic tumors. At intervals during the study, blood was withdrawn from selected rats, and 4-hydroxy-1-(3-pyridyl)-1-butanone-releasing hemoglobin adducts, which are formed upon metabolic activation of NNK, were quantified. The hemoglobin adducts were significantly repressed throughout the study in the rats treated with NNK plus PEITC compared to those treated with NNK. The 24-h urine sample of several rats was analyzed for 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol glucuronide. A 4-6-fold increase in the sum of these metabolites was observed in the rats treated with NNK plus PEITC compared to those treated with NNK. This is also consistent with inhibition of metabolic activation of NNK by PEITC. Collectively, the results of this study provide strong evidence for the efficacy of PEITC as a chemopreventive agent against NNK-induced pulmonary carcinogenesis in rats and indicate that two biomarkers of NNK metabolism, measurable in tobacco consumers, can be modulated in a predictable way by PEITC administration.

Animals↗
PubMed1996

Metabolites of a tobacco-specific nitrosamine, 4-(methylnitrosamino)- 1-(3-pyridyl)-1-butanone (NNK), in the urine of smokeless tobacco users: relationship between urinary biomarkers and oral leukoplakia.

Two metabolites of the carcinogenic tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone were quantified in the urine of smokeless tobacco users. The metabolites are 4-(methylnitrosamino) -1-(3-pyridyl)-1-butanol (NNAL) and [4-(methylnitrosamino)-1-(3-pyridyl) but-1-yl]-beta-O-D-glucosiduronic acid (NNAL-Gluc). The study population consisted of 47 male nonsmokers, of whom 23 were snuff dippers, 13 were tobacco chewers, 3 were users of both products, and 8 were nonusers. The levels of NNAL-Gluc in urine ranged from 0.14-30.3 pmol/mg creatinine with a mean +/- SD of 3.47 +/- 5.86, whereas the levels of NNAL ranged from 0.02-8.73 pmol/mg creatinine with a mean +/- SD of 0.92 +/- 1.59. The mean levels of NNAL-Gluc and NNAL were not significantly different from those measured in a previous study of smokers. The levels of NNAL-Gluc were significantly higher in snuff dippers than in tobacco chewers. The ratio of NNAL-Gluc:NNAL was higher in snuff dippers than in tobacco chewers or smokers. There was no indication of two phenotypes of the NNAL-Gluc:NNAL ratio in smokeless tobacco users, in contrast to previous observations in smokers. Of the 39 smokeless tobacco users in this study, 16 presented with oral leukoplakia. When the total levels of NNAL-Gluc, NNAL, or NNAL-Gluc + NNAL were divided into tertiles, there was a significant association between the presence of leukoplakia and increasing levels of these metabolites; a similar relationship was found between urinary cotinine and leukoplakia. The results of this study demonstrate that there is significant uptake of carcinogenic nitrosamines in smokeless tobacco users, and that such products are not harmless alternatives to cigarettes. Moreover, the urinary biomarkers NNAL-Gluc, NNAL, and cotinine were associated with the presence of leukoplakia, which provides biochemical support for the role of smokeless tobacco products as a cause of oral leukoplakia.

Adult↗
PubMed1995

Effects of phenethyl isothiocyanate on the tissue distribution of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone and metabolites in F344 rats.

Phenethyl isothiocyanate (PEITC), a naturally occurring chemopreventive agent, inhibits lung tumor induction in rats by the tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK). In this study, we examined the mechanism of tumor inhibition by determining the effects of dietary PEITC on levels of NNK and its metabolites in various tissues of NNK-treated F344 rats. F344 rats were fed control or PEITC-containing diets (3 mumol/g diet) before and throughout NNK treatment. To study NNK metabolism and distribution under both short-term and chronic NNK/NNK+PEITC treatments, control and PEITC-treated groups were divided into four subgroups. Subgroups were treated with either a single injection of [5-3H]NNK (1.76 mg/kg) or a total of 12, 24, and 36 doses of NNK administered three times/week. After a final injection of [5-3H]NNK in each subgroup, the rats were sacrificed at various time intervals, and NNK and its metabolites in lung, liver, nasal mucosa, pancreas, kidney, stomach, and serum were measured. Time-course curves for the tissue metabolites were generated, and the areas-under-the-curves were compared. We observed that lung, liver, and nasal mucosa, target tissues of NNK carcinogenesis in F344 rats, were also the tissues that had the highest levels of alpha-hydroxylation metabolites relative to NNK and its carbonyl reduction metabolite, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL). The most pronounced effect of PEITC was a reduction in levels of alpha-hydroxylation metabolites in most tissues examined (except nasal mucosa). The ratio of alpha-hydroxylation products to NNK + NNAL in most tissues was decreased by PEITC, indicating that alpha-hydroxylation of NNK/NNAL was inhibited. PEITC did not significantly affect the total levels of NNK and its metabolites in the lung and most tissues examined, indicating that PEITC does not alter the amount of NNK reaching the lung. These results support the hypothesis that inhibition of NNK-induced lung tumorigenesis by PEITC is a result of decreased metabolic activation of NNK.

Animals↗