Studies in tobacco carcinogenesis.

The vapour phase of freshly generated cigarette mainstream smoke, of sidestream smoke and of environmental tobacco smoke was analysed for such tumorigenic agents as benzene, 1,3-butadiene and acrolein with a newly developed, highly sensitive gas chromatography-mass selective detection method. The major carcinogen in tobacco smoke, catechol, was studied in regard to its specific action on the metabolism of benzo[a]pyrene in mouse lung and mouse skin. The major tobacco-specific carcinogens in tobacco and its smoke are the nicotine-derived N-nitrosamines, N'-nitrosonornicotine and 4-(nitroso-methylamino)-1-(3-pyridyl)-1-butanone.

Analysis and pyrolysis of some N-nitrosamino acids in tobacco and tobacco smoke.

A new tobacco-specific nitrosamine, 4-(N-nitrosomethylamino)-4-(3-pyridyl)butyric acid (iso-NNAC), has been identified in tobacco, and its structure was confirmed by gas chromatography-mass spectrometry following enrichment of a tobacco extract. The levels of iso-NNAC ranged from 0.01 to 0.

Lung cancer and the changing cigarette.

Epidemiological studies have shown that the long-term smoker of low-yield cigarettes has a 20-50% lower risk of lung cancer than the smoker of high-yield cigarettes. This risk reduction is attributed to changes in the make-up of cigarettes and especially to the introduction of filter tips. Other changes relate to the use of tobaccos that produce lower smoke yields, including reconstituted and expanded tobaccos, as well as utilization of porous cigarette paper and perforated filter tips.

Effect of dietary benzylselenocyanate on azoxymethane-induced colon carcinogenesis in male F344 rats.

The effect of dietary benzylselenocyanate (BSC) and its analogue, benzylthiocyanate (BTC), and sodium selenite during the initiation and postinitiation phases of azoxymethane (AOM)-induced intestinal carcinogenesis was studied in male F344 rats. Animals intended for initiation study were fed the high-fat (23.5% corn oil) diets containing 25, 50, and 100 ppm BSC (10, 20, and 40 ppm selenium, respectively) and 100 ppm BTC and 4 ppm selenium (as sodium selenite in drinking water); those intended for postinitiation study were fed the high-fat control diet.

Analysis of 1,3-butadiene and other selected gas-phase components in cigarette mainstream and sidestream smoke by gas chromatography-mass selective detection.

An analytical procedure was developed for the analysis of 1,3-butadiene, acrolein, isoprene, benzene and toluene in the gas phase of cigarette smoke and environmental tobacco smoke (ETS) utilizing cryogenic gas chromatography-mass selective detection (GC-MSD). The MSD was operated in the selective ion monitoring (SIM) mode. The compounds of interest eluted in less than 15 min.

Characterization of a glucuronide metabolite of 4-(methyl-nitrosamino)-1-(3-pyridyl)-1-butanone (NNK) and its dose-dependent excretion in the urine of mice and rats.

Following analysis by reversed-phase HPLC, a previously uncharacterized metabolite of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) was found in the urine of A/J mice treated with NNK. Treatment with beta-glucuronidase converted the metabolite to a peak that co-eluted with 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL). Treatment with sulfatase or beta-glucuronidase plus saccharic acid 1,4-lactone did not change the retention time of the metabolite.

Effect of different levels of calorie restriction on azoxymethane-induced colon carcinogenesis in male F344 rats.

Epidemiological and animal model studies indicate that increased calorie intake increases the risk for colon cancer development. Previous studies in animal models restricted the calorie intake severely, and none of these studies have investigated a dose-response effect of different levels of calorie restriction on colon carcinogenesis. The present study was designed to investigate the effect of various levels of calorie restriction on colon carcinogenesis in male F344 rats fed the low and high fat diets and the effect of these diets on the activities of colonic mucosal and tumor ornithine decarboxylase (ODC) and protein tyrosine kinase.

Effect of nicotine and tobacco-specific nitrosamines on the metabolism of N'-nitrosonornicotine and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone by rat oral tissue.

The effect of N'-nitrosoanatabine (NAT) and nicotine on the metabolism of N'-nitrosonornicotine (NNN) and 4-(methyl-nitrosamino)-1-(3- pyridyl)-1-butanone (NNK) by cultured rat oral tissue was investigated. The effect of NNN on NNK metabolism and the effect of NNK on NNN metabolism was also determined. NNK inhibited NNN metabolism more than NNN inhibited NNK metabolism.

Comparative metabolism of N'-nitrosonornicotine and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone by cultured F344 rat oral tissue and esophagus.

The metabolism and DNA binding of N'-nitrosonornicotine (NNN) and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) by cultured F344 rat oral tissue and esophagus were investigated over a range of concentrations. The metabolites present in the culture media were separated by high performance liquid chromatography and were identified by comparison to standards. alpha-Hydroxylation of NNN, an esophageal carcinogen, was the major pathway for metabolism of this nitrosamine in both tissues.

Effects of indole-3-carbinol on lung tumorigenesis and DNA methylation induced by 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) and on the metabolism and disposition of NNK in A/J mice.

The effects of indole-3-carbinol (I3C) on lung neoplasia induced by the tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) were assessed in an A/J mouse pulmonary adenoma bioassay. Mice were administered corn oil or I3C (25 or 125 mumol/mouse/day) by gavage for 4 consecutive days. Two h after the final pretreatment, mice were administered a single dose of NNK (10 mumol/mouse) i.

Chemoprevention of colon carcinogenesis by concurrent administration of piroxicam, a nonsteroidal antiinflammatory drug with D,L-alpha-difluoromethylornithine, an ornithine decarboxylase inhibitor, in diet.

The effect of three levels of piroxicam and three levels of D,L-alpha-difluoromethylornithine (DFMO) fed individually and in combination during the postinitiation phase of carcinogenesis was studied in male F344 rats to generate a data base on the efficacy and synergistic and additive effects of these compounds as inhibitors of colon carcinogenesis. The maximum tolerated dose of DFMO was determined in male F344 rats and found to be 5000 ppm in the AIN-76A diet. Piroxicam at levels of 25, 75, and 150 ppm and DFMO at concentrations of 400, 1000, and 4000 ppm (20, 50, and 80% maximum tolerated dose) in AIN-76 diet were tested individually and in combinations.

Effect of dietary aromatic isothiocyanates fed subsequent to the administration of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone on lung tumorigenicity in mice.

Naturally-occurring aromatic isothiocyanates, benzyl isothiocyanate (BITC) and phenethyl isothiocyanate (PEITC), were tested for their post-treatment effects on lung tumorigenicity by the tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) in A/J mice. Mice at 7 weeks of age were administered a single i.p.

Modulation of benzo[a]pyrene-DNA adducts in hamster cheek pouch by chronic ethanol consumption.

The effects of chronic ethanol consumption by hamsters on the binding of [3H]benzo[a]pyrene (BaP) metabolites to the DNA of cheek pouch and liver have been examined. Thirty hamsters were fed control liquid diet, and another 30 hamsters were given 6.6% v/v, 190 proof ethanol-containing diet for 28 days.

Synthesis and mutagenicity of trans-dihydrodiol metabolites of benzo[b]naphtho[2,1-d]thiophene.

The syntheses of potentially important metabolites of benzo[b]naphtho[2,1-d]thiophene ([2,1]BNT)--trans-1,2-dihydroxy-1,2-dihydrobenzo[b]naphtho[2,1- d]thiophene ([2,1]BNT-1,2-diol) and trans-3,4-dihydroxy-3,4-dihydrobenzo[b]naphtho[2,1-d]thiophene ([2,1]BNT-3,4-diol)--are described. The syntheses involved preparation of the appropriate 1-(3-benzo[b]-thiopheneyl)-2-(methoxyphenyl)ethylenes followed by photocyclization to methoxy-[2,1]BNTs, hydrolysis to hydroxy-[2,1]BNTs, oxidation to [2,1]BNT-diones, and NaBH4 reduction. The dihydrodiols were tested for mutagenicity in Salmonella typhimurium TA 100 with activation; [2,1]BNT-3,4-diol, which can form a bay region diol epoxide, was as mutagenic as [2,1]BNT whereas [2,1]BNT-1,2-diol was inactive.

Production of epidermal growth factor and transforming growth factor-alpha by the androgen-responsive LNCaP human prostate cancer cell line.

Epidermal growth factor (EGF)-related polypeptides may be involved in the growth of human prostate cancer cells, and in the androgen stimulation of hormone-responsive prostatic carcinomas. We have shown that androgen-responsive LNCaP cells, like the autonomous DU 145 human prostate cancer cell line, synthesize and secrete EGF and related polypeptides, including immunoreactive transforming growth factor-alpha (TGF-alpha). As determined by radioimmunoassay, intracellular EGF levels were approximately 100 times those of TGF-alpha, but together these accounted for less than half of the total EGF-like polypeptides detected in a radioreceptor assay.

Inducible cellular responses to ultraviolet light irradiation and other mediators of DNA damage in mammalian cells.

Both naturally occurring and carcinogen-induced tumors display not only point mutations in cellular oncogenes but also more complex changes in cellular oncogenes and other cellular genes. For this and other reasons, it seems likely that DNA damage in mammalian cells can induce alterations in gene expression that may have both short and long term consequences in the target cell. The purpose of this review is to summarize current available information on inducible responses to UV-irradiation and other mediators of DNA damage in mammalian cells, and to provide some working hypotheses.

Inhibition by dietary benzylselenocyanate of hepatocarcinogenesis induced by azoxymethane in Fischer 344 rats.

The effect of dietary benzylselenocyanate (BSC), a novel organoselenium compound and its sulfur analog, benzylthiocyanate (BTC), on hepatocarcinogenesis induced by azoxymethane (AOM) was investigated in male F344 rats. Eighty-one weanling rats were divided into 3 groups and were raised on a semipurified diet (control diet). Starting from 5 weeks of age, groups of animals consuming the control diet were fed one of the experimental diets containing 25 ppm BSC or BTC.

Effects of catechol on the induction of tumors in mouse skin by 7,8-dihydroxy-7,8-dihydrobenzo[a]pyrenes.

Catechol (1,2-dihydroxybenzene) is a major phenolic compound present in the co-carcinogenic fraction of cigarette tar. It has been shown to be a potent co-carcinogen with benzo[a]pyrene (BaP) in mouse skin. In this study we have examined the co-carcinogenic and co-initiating activities of catechol with racemic and enantiomeric 7,8-dihydroxy-7,8-dihydrobenzo[a]pyrenes (BaP-7,8-diols) in mouse skin.

Catechol-induced alterations in metabolic activation and binding of enantiomeric and racemic 7,8-dihydroxy-7,8-dihydrobenzo[a]pyrenes to DNA in mouse skin.

Catechol (1,2-dihydroxybenzene) is a potent co-carcinogen with benzo[a]pyrene (BaP) and with (+/-)-7,8-dihydroxy-7,8- dihydrobenzo[a]pyrene (BaP-7,8-diol) in mouse skin. The effects of catechol on the metabolic activation of (+)- and (-)-[3H]BaP-7,8-diols and on epidermal DNA adduct formation of racemic and enantiomeric [3H]BaP-7,8-diols were examined by applying the tritiated diols to mouse skin. The major metabolite of the (+)-[3H]BaP-7,8-diol was the hydrolysis product of (-)-[3H]-7 alpha, 8 beta-dihydroxy-9 beta, 10 beta-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (anti-BPDE).

Effects of alkyl chain length on the inhibition of NNK-induced lung neoplasia in A/J mice by arylalkyl isothiocyanates.

Six homologous arylakyl isothiocyanates were evaluated for their abilities to inhibit pulmonary adenomas induced by the tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) in A/J mice. Four consecutive daily doses (5 mumol/mouse) of phenyl isothiocyanate (PITC), benzyl isothiocyanate (BITC), phenethyl isothiocyanate (PEITC), 3-phenylpropyl isothiocyanate (PPITC), 4-phenylbutyl isothiocyanate (PBITC), 4-oxo-4-(3-pyridyl)-butyl isothiocyanate (OPBITC) and corn oil were administered to mice by gavage. Two hours following the final dosing, mice were administered saline or 10 mumol of NNK in saline i.

Identification and analysis of a nicotine-derived N-nitrosamino acid and other nitrosamino acids in tobacco.

Research on carcinogenic, tobacco-specific N-nitrosamines (TSNA) led to the identification and analysis of 4-(methylnitrosamino)-4-(3-pyridyl)butyric acid (iso-NNAC) in tobacco and tobacco smoke. In order to isolate iso-NNAC, an aqueous tobacco extract at pH 4 was partitioned with ethyl acetate after the other N-nitrosamino acids and TSNA were removed at pH 2 and pH 9 respectively. The structure of iso-NNAC was confirmed by GC-MS after enrichment of the methylated pH 4 fraction by chromatography on an alumina column.

Identification of sulfate and glucuronic acid conjugates of the 5-hydroxy derivative as major metabolites of 2-amino-3-methylimidazo[4,5-f]quinoline in rats.

New metabolites of 2-amino-3-methylimidazo[4,5-f]quinoline (IQ), a potent mutagen and carcinogen formed during cooking of meat or fish, have been identified and quantitated in the urine and bile of rats. Administration was either by a pulse gavage dose of 40 mg/kg [2-14C]IQ or by dietary intake of 300 ppm IQ for 6 weeks. The metabolites were isolated by high-performance liquid chromatography and quantitated by radioactivity.

DNA isolation from small tissue samples using anion-exchange HPLC.

A new method for isolating high purity DNA from small amounts of tissue is described. Tissue homogenates were treated with protease and extracted once with chloroform:isoamyl alcohol. The aqueous layer was injected onto a Waters Protein Pak anion-exchange HPLC column.

Effects of aromatic isothiocyanates on tumorigenicity, O6-methylguanine formation, and metabolism of the tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone in A/J mouse lung.

Phenethyl isothiocyanate (PEITC), benzyl isothiocyanate (BITC), and phenyl isothiocyanate (PITC) were tested for their abilities to inhibit lung tumorigenesis and O6-methylguanine formation in lung DNA induced by the tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) in A/J mice. Pretreatment with PEITC for 4 consecutive days at daily doses of 5 or 25 mumol inhibited tumor multiplicity induced by a single 10-mumol dose of NNK by approximately 70% or 97%, respectively. The 25-mumol daily dose of PEITC also reduced the percentage of animals that developed tumors by 70%.

Chemoprevention of experimental mammary carcinogenesis by the synthetic organoselenium compound, benzylselenocyanate, in rats.

The effect of the dietary organoselenium compound, benzylselenocyanate (BSC) along with its sulphur analogue, benzylthiocynanate (BTC) and sodium selenite (Na2SeO3), on 7,12-dimethylbenz[a]anthracene (DMBA)-induced mammary carcinogenesis was examined in female Sprague-Dawley rats during the initiation phase of carcinogenesis. Semipurified diets containing 25 p.p.