Polymorphisms in CYP1A1, GSTM1, GSTT1 and lung cancer below the age of 45 years.

BACKGROUND: A genetic component of early-onset lung cancer has been suggested. The role of metabolic gene polymorphisms has never been studied in young lung cancer cases. Phase 1 and Phase 2 gene polymorphisms are involved in tobacco carcinogens' metabolism and therefore in lung cancer risk. METHODS: The effect of metabolic gene polymorphisms on lung cancer at young ages was studied by pooling data from the Genetic Susceptibility to Environmental Carcinogens (GSEC) database. All primary lung cancer cases of both sexes who were Caucasian and

Impact of metabolic genotypes on levels of biomarkers of genotoxic exposure.

Phase I and Phase II xenobiotic-metabolising enzyme families are involved in the metabolic activation and detoxification of various classes of environmental carcinogens. Particular genetic polymorphisms of these enzymes have been shown to influence individual cancer risk. A brief overview is presented about recent research of the relationship between metabolic genotypes and internal dose, biologically effective dose and cytogenetic effects of complex and specific genotoxic exposures of human study populations, and we report our new results from two molecular epidemiological studies. We investigated the effects of multiple interactions among CYP1A1 Ile462Val, CYP1A1 MspI, CYP1B1 Leu432Val, CYP2C9 Arg144Cys, CYP2C9 Ile359Leu, NQO1 Pro189Ser, GSTM1 gene deletion and GSTP1 Ile105Val genotypes on the levels of carcinogen-DNA adducts determined by (32)P-postlabelling and PAH-DNA immunoassay in peripheral blood lymphocytes from workers occupationally exposed to polycyclic aromatic hydrocarbons in aluminium plants, and in bronchial tissue from smoking lung patients. A statistically significant positive linear correlation was observed between white blood cell aromatic DNA adduct and urinary 1-hydroxypyrene (1-OHPY) levels from potroom workers with GSTM1 null genotype (P=0.011). Our results suggest interactions between GSTM1 and GSTP1 alleles in modulation of urinary 1-OHPY levels and white blood cell DNA adduct levels in the PAH-exposed workers. Interactions between GSTM1 and GSTP1 alleles, in association with particular genotype combinations of CYPs, were also recognised in bronchial aromatic DNA adduct levels of smoking lung patients. The impact of single metabolic genotypes and their combinations on biomarkers of exposure was usually weak, if any, in both our studies and reports of the literature. The effect of special metabolic gene interactions may be better recognised if the compared groups of individuals are stratified for multiple potential modulators of the observable biomarker end-point, and/or if chemical structure-specific biomarker methods are applied.

Biomonitoring of human genotoxicity induced by complex occupational exposures.

Sensitivity, specificity and correlations among several biomarkers for monitoring occupational exposure to complex mixtures of genotoxic agents were assessed in occupational environments in Hungarian study populations. The studies have been focused on DNA adduct formation, urinary metabolites, mutations and micronuclei induced by exposures to complex organic mixtures. In two Hungarian aluminium plants, increased DNA adduct and 1-hydroxypyrene (1-OH-PY) levels were observed in workers as compared to controls. However, no association between the biomarker levels was evident on an individual basis. In Hungarian garage mechanics, DNA adduct determinations did not show increased genotoxic exposure as compared to the controls. However, ambient air measurements, significantly enhanced 1-OH-PY levels, and slightly enhanced frequency of micronuclei indicated increased polycyclic aromatic hydrocarbon (PAH) exposure in the garages, as compared to the general environment. In a Hungarian vulcanizing plant, DNA adduct determinations and 1-OH-PY did not show significantly elevated exposure levels as compared to controls. The glycophorin A (GPA) somatic mutation assay was also negative for this occupational exposure. The results support previous observations of a lack of correlation between DNA adducts detectable by 32P-postlabelling and those measured by the PAH-DNA immunoassay in the same DNA sample. These studies also demonstrate a lack of close correlation between levels of DNA adducts and urinary 1-OH-PY in the same individual.

Analyses of bronchial bulky DNA adduct levels and CYP2C9, GSTP1 and NQO1 genotypes in a Hungarian study population with pulmonary diseases.

Carcinogen-DNA adducts may represent an intermediate end-point in the carcinogenic cascade and may reflect exposure to chemical carcinogens, as well as susceptibility and, ultimately, cancer risk. Interindividual variability in activity of enzymes involved in the metabolism of polycyclic aromatic hydrocarbons to mutagenic diol epoxides may predict adduct levels and, indirectly, lung cancer risk. Using 32P-postlabeling methods, the levels of bulky DNA adducts were determined in macroscopically normal bronchial tissues obtained from resected lobes of 143 Hungarian patients with lung malignancy and other pulmonary conditions. DNA from normal tissue was also evaluated for polymorphisms in cytochrome P450 2C9 (CYP2C9) at two sites, codons 144 (Arg/Cys) and 359 (Ile/Leu), for glutathione S-transferase P1 (GSTP1) at codon 105 and for NAD(P)H:quinone oxidoreductase (NQO1) at codon 187 (Pro/Ser). Using the Mann-Whitney U-test and analysis of variance, levels of adducts were evaluated in relation to variant genotypes, separately for smokers and non-smokers. As previously reported, bulky DNA adduct levels in smokers (n = 104) were estimated to be 54% higher than in non-smokers (n = 39) (8.6 +/- 4.2 versus 5.6 +/- 3.3 per 10(8) nucleotides, respectively, P < 0.01). Adduct levels were 16-29% higher in individuals with the homozygous Ile359/Ile359 CYP2C9 allele than in those heterozygous for the variant allele (Ile359/Leu359) [8.8 +/- 4.3 (n = 84) versus 7.6 +/- 3.5 (n = 20) for smokers and 5.8 +/- 3.5 (n = 32) versus 4.5 +/- 1.3 (n = 7) for non-smokers], although differences were not statistically significant. There were no clear differences in adduct levels in relation to genotypes of NQO1 or GSTP1. Although numbers of patients in this study are large in relation to many studies of carcinogen-DNA adducts, it is still possible that significant differences were not noted for polymorphisms in xenobiotic metabolizing enzymes due to relatively small numbers in stratified data.

DNA damage in humans exposed to environmental and dietary polycyclic aromatic hydrocarbons.

The paper describes recent research on human DNA damage related to environmental and dietary polycyclic aromatic hydrocarbon (PAH) exposures. The study populations either represent general populations of large geographical regions, or their exposure situation may have relevance to the general population. In Silesia, Poland, and Northern Bohemia, Czech Republic, where coal-based industry and domestic heating are the major sources of PAHs, significant differences have been observed in white blood cell DNA adducts and cytogenetic biomarkers between environmentally exposed and rural control populations, and significant seasonal variations of DNA damage have been detected. Bus drivers, traffic policemen and local residents have been involved in biomarker studies in Copenhagen, Athens, Genoa and Cairo, and differences have been measured in the level of DNA damage of urban and rural populations. Burning of smoky coal in unvented homes in Xuan Wei region, China, causes high PAH exposure of residents, which has been reflected in DNA adduct levels in different tissues. Indoor wood burning in open fireplaces did not increase human DNA adduct levels. Oil-well fires left burning in Kuwait after the Persian Gulf war created an unprecedented environmental pollution. However, insignificant environmental PAH levels were measured several miles from these fires. Aromatic and PAH-DNA adduct levels in white blood cells of US Army soldiers were lower during their deployment in Kuwait, than in Fulda, Germany, where they were stationed before and after serving in Kuwait. The contribution of dietary PAH exposure to blood cell DNA adduct levels had been demonstrated in studies in which volunteers consumed heavily charbroiled beef. Environmental tobacco smoke did not cause detectable changes, as measured by 32P-postlabelling, in DNA adduct levels in non-smokers. In the reviewed studies, observed DNA adduct levels were generally in the range of 1 to 10 adducts, and not higher than 40 adducts in 108 nucleotides. Typically, 1.5 to 3-fold differences have been detected in DNA adduct levels between the exposed and control groups.

Synthesis, characterization, and quantitation of a 4-aminobiphenyl-DNA adduct standard.

32P-Postlabeling is a powerful technique for the detection of DNA adducts; however, quantitation of DNA adducts by this method can result in errors due to differences in hydrolysis and labeling efficiencies between adducted and normal nucleotides. We have synthesized a DNA sample modified with 4-aminobiphenyl to serve as a quantitation standard for 32P-postlabeling and other DNA adduct detection methodologies. [2,2'-3H]-N-Hydroxy-4-aminobiphenyl was reacted with calf thymus DNA at pH 5 to give 62 +/- 0.8 adducts/10(8) nucleotides (mean +/- SD) on the basis of 3H content. HPLC analyses following enzymatic hydrolysis to nucleosides indicated one major adduct, N-(deoxyguanosin-8-yl)-4-aminobiphenyl (dG-C8-4-ABP). The adduct identity was confirmed by HPLC/electrospray ionization mass spectrometry, which indicated a modification level of 19 +/- 1.7 dG-C8-4-ABP/10(8) nucleotides. 32P-Postlabeling analysis gave a value of 0.84 dG-C8-4-ABP/10(8) nucleotides, while a dissociation-enhanced lanthanide fluoroimmunoassay (DELFIA) indicated levels of 82 +/- 26 and 63 +/- 20 dG-C8-4-ABP/10(8) nucleotides after enzymatic hydrolysis to nucleotides and nucleosides, respectively. The utility of the DNA adduct standard was determined by assessing the level of dG-C8-4-ABP in liver DNA from mice treated with [2,2'-3H]-4-aminobiphenyl. 32P-Postlabeling analyses, based upon measuring the extent of the 32P incorporation, underestimated the levels of dG-C8-4-ABP, while DELFIA, using a G-C8-4-ABP quantitation standard, overestimated the adduct levels. The adduct levels determined by HPLC/electrospray ionization mass spectrometry best reflected those obtained from 3H incorporation. When the 32P-postlabeling analyses and the DELFIA were conducted using the DNA modified in vitro with dG-C8-4-ABP as a quantitation standard, accurate estimations of the extent of in vivo formation of dG-C8-4-ABP were obtained.

Smoking-associated bulky DNA adducts in bronchial tissue related to CYP1A1 MspI and GSTM1 genotypes in lung patients.

Relationships between smoking status and levels of bulky DNA adducts were investigated in bronchial tissue of lung patients in relation to their GSTM1 and CYP1A1 MspI genotypes. A total of 150 Hungarian patients undergoing pulmonary surgery were included in the study, 124 with lung malignancies and 26 with non-malignant lung conditions. There were significant relationships between smoking status and bulky DNA adduct levels, as determined by 32P-post-labelling analysis, in macroscopically normal bronchial tissues. There was a highly significant difference in the adduct levels of a combined group consisting of current smokers and short-term ex-smokers (< or = 1 year abstinence) compared with life-time non-smokers and long-term ex-smokers (> 1 year abstinence) (P = 0.0001). The apparent half-life was estimated to be 1.7 years for bulky DNA adducts in the bronchial tissue from ex-smokers. There were no statistically significant correlations between (i) daily cigarette dose and DNA adduct levels in current smokers, (ii) DNA adduct level and histological type of lung cancer, or (iii) GSTM1 and CYP1A1 MspI genotypes and DNA adduct levels after adjustment for either smoking status or malignancy. By multiple logistic regression analysis, smoking and GSTM1 null genotype were found to be risk factors for squamous cell carcinoma. However, bulky DNA adduct levels in bronchial tissue did not appear to be a statistically-significant risk factor for the major histological types of lung cancer.

Biomonitoring of United States Army soldiers serving in Kuwait in 1991.

Biomarkers of polycyclic aromatic hydrocarbon (PAH) exposure and genetic biomarkers of potential cancer susceptibility were determined in a group of United States Army soldiers who were deployed to Kuwait and Saudi Arabia in 1991 in the aftermath of the Persian Gulf War. Because hundreds of oil well fires were still burning, there was concern that ground troops stationed in Kuwait might be exposed to high levels of PAHs and other toxicants. The United States Army Environmental Hygiene Agency monitored air and soil for ambient PAHs. In addition, a group of 61 soldiers was involved in the biomonitoring study reported here. These soldiers kept diaries of daily activities and provided blood and urine samples in Germany (June) before deployment to Kuwait, after 8 weeks in Kuwait (August), and 1 month after the return to Germany (October). Here we present data for PAH-DNA adducts measured by immunoassay in blood cell DNA samples obtained at all three sampling times from 22 soldiers and bulky aromatic adducts measured by 32P-postlabeling in blood cell DNA samples from 20 of the same soldiers. Urinary 1-hydroxypyrene-glucuronide levels were determined by synchronous fluorescence spectrometry in a matched set of samples from 33 soldiers. Contrary to expectations, environmental monitoring showed low ambient PAH levels in the areas where these soldiers were working in Kuwait. For both DNA adduct assays, levels were the lowest in Kuwait in August and increased significantly after the soldiers returned to Germany (October). Urinary 1-hydroxypyrene-glucuronide levels were also lowest in Kuwait and highest in Germany, but the differences were not statistically significant. The PAH-exposure biomarker levels were not significantly influenced by polymorphic variations of CYP1A1 (MspI) and glutathione S-transferases M1 and T1. Overall, the data suggest that this group of soldiers was not exposed to elevated levels of PAHs while deployed in Kuwait.

Biomonitoring of genotoxic exposure in aluminium plant workers by determination of DNA adducts in human peripheral blood lymphocytes.

A longitudinal human biomonitoring study has been performed in two Hungarian primary aluminium production plants that operated Söderberg cells. Carcinogen-DNA adducts have been determined by 32P-postlabelling and competitive enzyme-linked immunosorbent assay in peripheral blood lymphocytes from potroom workers and occupationally unexposed control individuals. Blood samples were collected on three occasions; the first two occasions were 1 year apart during normal operation, and the last samples were taken 6 months after close-down of aluminium production. Assays of the first set of samples demonstrated no significant difference between the control group and workers in Plant I. Workers in Plant II had significantly higher DNA adduct levels than individuals in the control group and workers in Plant I. One year later a significant elevation of DNA adducts was detected in Plant I so that values approached those seen in Plant II, which remained unchanged. In the last sample set there was no difference between former potroom workers and occupationally unexposed individuals. The results suggest that carcinogen-DNA adducts are a useful biomarker for monitoring occupational genotoxic exposure to polycyclic aromatic hydrocarbons, and that the findings can contribute to improved health risk assessment.

Detection of polycyclic aromatic hydrocarbon exposure damage using different methods in laboratory animals.

Benzo[a]pyrene, benzo[b]fluoroanthene and dibenzo[a,h]anthracene dissolved in a 1:2 mixture of dimethylsulphoxide (DMSO) and water were administered to two groups of female mice, each group containing 15 mice. The doses were administered orally (via gavage) at the respective rates of 1 and 100 micrograms kg-1 body weight five times per week for a period of 9 weeks. The influence of the polycyclic aromatic hydrocarbons (PAHs) was determined using the following methods: determination of DNA-PAH adducts, of chromosome injuries (micronucleus test), of induction of repair using the unscheduled DNA synthesis (UDS) test, and by examination of the DNA structure after nucleoid sedimentation. All the methods investigated provided evidence of a significant effect resulting from exposure to PAHs on the parameters examined. Following chronic exposure to PAHs, the formation of DNA-PAH adducts and injury to the genetic material, as well as the appearance of micronuclei (micronucleus test), the induction of unscheduled DNA synthesis (UDS test) and mutation of the DNA structure (nucleoid sedimentation), were demonstrated. The described methods therefore provide a means for the detection of genetic damage caused by PAH exposure in humans.

Smoking-related increase in O6-alkylguanine-DNA alkyltransferase activity in human lung tissue.

O6-Alkylguanine-DNA alkyltransferase (AGAT) activity was determined in macroscopically normal peripheral lung tissues from 122 patients undergoing lung surgery. AGAT activity of smokers was 1.4-fold higher than that of lifetime non-smokers (P = 0.030). Less than one year of abstinence from smoking did not cause a significant decrease in AGAT activity in former smokers, however, longer abstinence resulted in a decrease in AGAT activity to the level detected in lifetime non-smokers. There was no significant difference between levels of AGAT activity in lung cancer and noncancer patients. The results demonstrate that the level of AGAT activity in human peripheral lung tissue is influenced by smoking habits but does not have a diagnostic correlation to lung cancer.

Increased sensitivity for determination of polycyclic aromatic hydrocarbon-DNA adducts in human DNA samples by dissociation-enhanced lanthanide fluoroimmunoassay (DELFIA).

A competitive enzyme-linked immunosorbent assay (ELISA), the most frequently used immunoassay for the determination of polycyclic aromatic hydrocarbon-DNA adducts in human tissues, has been modified to achieve approximately a 6-fold increase in sensitivity. The new assay, a competitive dissociation-enhanced lanthanide fluoroimmunoassay (DELFIA) has utilized the same rabbit antiserum as the ELISA, antiserum elicited against DNA modified with benzo[a]pyrene. However, the alkaline phosphatase conjugate has been replaced with a biotin-europium-labeled streptavidin signal amplification system, and the release of europium into the solution forms a highly fluorescent chelate complex that is measured by time-resolved fluorometry. The DELFIA has achieved a 5- to 6-fold increase in sensitivity for measurement of DNA samples modified in vitro with benzo[a]pyrene, for cultured cells exposed to radiolabeled benzo[a]pyrene, and for human samples from occupationally exposed workers. The assay has been validated by comparison of adduct levels determined by DELFIA, ELISA, and radioactivity in DNA from mouse keratinocytes exposed to radiolabeled benzo[a]pyrene. Human lymphocyte DNA samples from 104 Hungarian aluminum plant workers were assayed by ELISA and compared to blood cell DNA samples from 69 Italian coke oven workers assayed by DELFIA. The standard curves demonstrated that the limit of detection of 4.0 adducts in 10(8) nucleotides for polycyclic aromatic hydrocarbon-DNA adducts by ELISA, using 35 micrograms of DNA/microtiter plate well, has been decreased to 1.3 adducts in 10(8) nucleotides by DELFIA, using 20 micrograms of DNA/microtiter well. If 35 micrograms of DNA were used in the DELFIA, the calculated detection limit would be 0.7 adducts in 10(8) nucleotides.(ABSTRACT TRUNCATED AT 250 WORDS)

DNA adducts in peripheral blood lymphocytes from aluminum production plant workers determined by 32P-postlabeling and enzyme-linked immunosorbent assay.

32P-Postlabeling analysis and enzyme-linked immunosorbent assay (ELISA) have been used to detect DNA adducts in peripheral blood lymphocytes from primary aluminum production plant workers who were exposed occupationally to a mixture of polycyclic aromatic hydrocarbons (PAHs). Preliminary results reported here are from a comparative study being performed in two aluminum plants. The levels of aromatic DNA adducts have been determined by the 32P-postlabeling assay in samples collected on two occasions, 1 year apart. PAH-DNA adduct levels have also been determined by competitive ELISA in the second set of DNA samples. The results show the necessity of follow-up biomonitoring studies to detect possible alterations in biological effect induced by changing exposures. The comparison of the results obtained by 32P-postlabeling and ELISA may lead to a better understanding of the power and weaknesses of the two methods applied in these studies.

Biomarkers of carcinogen exposure and cancer risk in a coke plant.

To evaluate the association between an indicator of carcinogen exposure (peripheral blood leukocyte DNA adducts of polycyclic aromatic hydrocarbons) and an early indicator of neoplastic transformation (sputum epithelial cell membrane antigens binding by monoclonal antibodies against small cell lung cancer and against nonsmall cell lung cancer), a survey of 350 coke-oven workers and 100 unexposed workers was planned. This paper reports a pilot investigation on a subgroup of 23 coke-oven workers and 8 unexposed controls. A "gas regulator" worker with positive tumor antigen binding was identified. Results show that smokers, subjects with decreased pulmonary function (forced expiratory volume in 1 sec/forced vital capacity% < 80), and those with morphological dysplasia of sputum cells have higher levels of DNA adducts. The gas regulators showed the highest values for adducts; however, no significant difference of adduct levels was found between the coke-oven group and unexposed controls.

Determination of smoking-related DNA adducts in lung-cancer and non-cancer patients.

Aromatic DNA adduct levels were determined in macroscopically normal bronchial tissues from 98 patients undergoing pulmonary surgery. The mean DNA adduct level for the 45 current smokers was significantly higher than that of the 16 life-time non-smokers. There was a weak association between adduct levels and daily cigarette consumption above 10 cigarettes per day. DNA adduct levels in the 37 former smokers suggested an exponential form of adduct elimination with a rapid initial and a slower later phase after cessation of smoking. There was no quantitative association between bronchial DNA adduct levels and lung cancer.

Monitoring occupational exposure to carcinogens.

32P-Postlabelling has been used for biomonitoring occupational exposure to complex mixtures of polycyclic aromatic hydrocarbons in iron foundries, coke oven and aluminium plants and among roofers and surface-coating workers. Enhanced levels of aromatic DNA adducts have been detected in exposed populations in comparison to controls. Dose-related adduct formation has been found in iron foundry and coke-oven workers and roofers. The importance of longitudinal biomonitoring has been shown in two aluminium plants. Comparison between 32P-postlabelling and immunoassays revealed wide variations. DNA adduct levels obtained by the current methods should thus be regarded as relative values between individuals and control and exposure groups.

Smoking-related DNA adducts: 32P-postlabeling analysis of 7-methylguanine in human bronchial and lymphocyte DNA.

7-methylguanine DNA adducts were determined in macroscopically normal bronchial specimens and peripheral blood lymphocytes of 20 patients undergoing pulmonary surgery. A recently developed 32P-postlabeling assay was applied with anion exchange chromatography as an adduct enrichment method. The material consisted of 13 smokers and 7 non-smokers. The mean bronchial 7-methylguanine levels of 11 smokers and 6 non-smokers were 17.3 and 4.7 adducts/10(7) nucleotides. In lymphocyte DNA, the respective mean levels were 11.5 and 2.3 adducts/10(7) nucleotides. The bronchial DNA adduct levels in smokers were statistically higher than those in non-smokers. Among 5 smokers, for whom both bronchial and lymphocyte DNA was available, 7-methylguanine levels correlated in the two tissues (r = 0.77).

32P-postlabelling detection of aromatic DNA adducts in peripheral blood lymphocytes from aluminium production plant workers.

Aluminium production plant workers are exposed to a great number of airborne polycyclic aromatic hydrocarbons and epidemiological studies suggest that these workers are at increased risk of lung and bladder cancer. Blood samples from 46 workers at 2 primary aluminium plants and from 29 occupationally unexposed control individuals were analysed. DNA was isolated from the peripheral blood lymphocytes and aromatic DNA adducts were detected by 32P-postlabelling assay using the nuclease P1 digestion procedure for the enrichment of the adducts. The total levels of DNA adducts of exposed individuals varied from the detection limit of about 0.5 adducts/10(8) nucleotides up to 7.1 adducts/10(8) nucleotides and control adduct levels were up to 2.42 adducts/10(8) nucleotides. There was no significant difference between the mean adduct levels of the control group and of the individuals of one plant. However, the mean DNA adduct level obtained from workers of the second plant was significantly higher than that of the controls (p less than 0.001) and of the first plant (p less than 0.01), respectively. This difference can be attributed to differences in the design of technology and different levels of exposure at the 2 plants. The results of this study encourage further investigations of the use of peripheral white blood cells as marker cells and of 32P-postlabelling analysis for monitoring occupational exposure to mixtures of environmental carcinogenic pollutants.

Influence of cigarette smoking on the levels of DNA adducts in human bronchial epithelium and white blood cells.

The presence of carcinogen-DNA adducts in human tissues is evidence of exposure to carcinogens and may be an indicator of cancer risk. DNA was isolated from non-tumorous bronchial tissue of 37 cigarette smokers, 8 former smokers and 8 non-smokers and analyzed for the presence of aromatic and/or hydrophobic DNA adducts in the 32P-post-labelling assay. Adducts were detected as bands of radioactive material when 5'-32P-labelled deoxyribonucleoside 3',5'-bisphosphates were chromatographed on polyethyleneimine-cellulose tlc plates, and the patterns indicated the formation of adducts by a large number of compounds. Adduct levels detected in DNA from non-smokers, former smokers and current smokers were 3.45 +/- 1.62, 3.93 +/- 1.92 and 5.53 +/- 2.13 adducts/10(8) nucleotides, respectively. The differences in adduct levels between smokers and former and non-smokers were statistically significant (p less than 0.01); and among the smokers, significant correlations were found between adduct levels and both daily cigarette consumption and total cigarette consumption (daily consumption X number of years smoked). DNA was also isolated from the peripheral-blood leukocytes of 31 heavy smokers (greater than 20 cigarettes/day) and 20 non-smokers and analyzed by 32P-post-labelling. Adduct levels in the smokers' samples were not significantly different from levels in the non-smokers' samples (2.53 +/- 1.31 and 2.12 +/- 1.44 adducts/10(8) nucleotides, respectively). Thus, evidence for carcinogen exposure was found in human bronchial epithelium, a target tissue for tobacco-induced tumour formation, but not in peripheral-blood cells, indicating possible limitations in the use of the latter as a surrogate, non-target tissue source of DNA for monitoring human exposure to inhaled carcinogens.

Formation of DNA adducts in the skin of psoriasis patients, in human skin in organ culture, and in mouse skin and lung following topical application of coal-tar and juniper tar.

Preparations of coal-tar and juniper tar (cade oil) that are used in the treatment of psoriasis are known to contain numerous potentially carcinogenic polycyclic aromatic hydrocarbons (PAH). Evidence of covalent binding to DNA by components of these mixtures was sought in a) human skin biopsy samples from 12 psoriasis patients receiving therapy with these agents, b) human skin explants maintained in organ culture and treated topically with the tars, and c) the skin and lungs of mice treated with repeated doses of the formulations following the regimen used in the clinic. DNA was isolated from the human and mouse tissues and digested enzymically to mononucleotides. 32P-Post-labeling analysis revealed the presence of aromatic DNA adducts in the biopsy samples at levels of up to 0.4 fmol total adducts/microgram DNA. Treatment of human skin in organ culture produced similar levels of adducts, while treatment with dithranol, a non-mutagenic therapeutic agent, resulted in chromatograms indistinguishable from those from untreated controls. In mouse skin, coal-tar ointment and juniper tar gave similar DNA adduct levels, with a similar time-course of removal: maximum levels (0.5 fmol/microgram DNA) at 24 h after the final treatment declined rapidly to 0.05 fmol/microgram at 7 d, thereafter declining slowly over the succeeding 25 d. However, while coal-tar ointment produced only very low levels of adducts in mouse lung (less than 0.03 fmol/microgram DNA), juniper tar produced adducts at a high level (0.7 fmol/microgram DNA) that were persistent in this tissue. These results provide direct evidence for the formation of potentially carcinogenic DNA damage in human and mouse tissue by components of these therapeutic tar preparations.