Analysis of pesticide exposure and DNA damage in immigrant farmworkers.

In the last decade, the Comet assay has been used increasingly in studies of workers potentially exposed to genotoxic substances in the workplace or environment. Significant increases in DNA damage measured with the Comet assay has been reported in lymphocytes of agricultural workers; however, less intrusive means of biomonitoring are needed in epidemiological investigations. This study was designed to use the Comet assay to describe the association of markers of DNA damage in oral leukocytes with biomarkers of pesticide exposure in 134 farmworkers working in berry crops in Oregon compared to control populations. The authors also examined the extent of DNA damage in young workers compared to adults and the effect of work histories, lifestyle factors, and diet on markers of DNA damage. Urinary levels of organophosphate pesticides were low at the time of sampling; however, mean levels of the Captan metabolite tetrahydrophthalimide (THPI) were found to be shifted significantly higher in the farmworkers (0.14 microg/ml) compared to controls (0.078 microg/ml) (one-sided p value=.01). Likewise, the combined molar equivalent of all dialkylphosphate metabolites was marginally higher in farmworkers (p value=.05). The mean tail intensity was significantly greater for agricultural workers compared to controls (one-sided p value<.001), indicating more DNA damage in the oral leukocytes. On average, the mean tail intensity was 10.9 units greater for agricultural workers (95% CI: 6-16 units greater). Tail moment was also significantly greater for agricultural workers compared to nonagricultural workers (one-sided p value<.001). No Comet parameter was significantly associated with years spent working in agriculture, age, sex, body mass index, diet, and alcohol or tobacco use. The results of this study demonstrate the feasibility for using the Comet assay in biomonitoring studies of farmworkers. Additional studies are needed to examine the effects of different pesticide types on DNA damage and to capture the temporal relationship between exposure to agricultural chemicals and changes in Comet parameters.

Case-control study of oral and oropharyngeal cancer in whites and genetic variation in eight metabolic enzymes.

BACKGROUND: Genetic variation in xenobiotic metabolizing enzymes may explain differing susceptibilities to the cancer causing effects of tobacco and alcohol. METHODS: We compared 203 oral squamous cell carcinoma cases and 416 controls for single nucleotide polymorphisms (SNPs) in 8 genes (CYP1A1, CYP2E1, MPO, mEH, GSTM1, GSTT1, GSTP1, and NAT2). Except for NAT2, genotype frequencies were similar in the 2 groups. We classified subjects as fast or slow NAT2 acetylators genotyping 13 NAT2 SNPs. RESULTS: Fast acetylators were overrepresented in cases (53.7%) compared with controls (43.9%; odds ratio (OR) 1.55, 95% confidence interval (CI) 1.08-2.20; p value = .03). Gene-gene interaction testing suggested several cancer-NAT2 associations, with association strongest among persons without a CYP1A1 variant (*2C or *4) allele (OR 1.77, 95% CI 1.20-2.60, p value = .03) or with a variant MPO (463A) allele (OR 2.38, 95% CI 1.34-4.21, p value = .05). CONCLUSION: These results implicate fast NAT2 acetylation as a risk factor for oral cancer.

Biomarkers of oxidative stress and DNA damage in agricultural workers: a pilot study.

Oxidative stress and DNA damage have been proposed as mechanisms linking pesticide exposure to health effects such as cancer and neurological diseases. A study of pesticide applicators and farmworkers was conducted to examine the relationship between organophosphate pesticide exposure and biomarkers of oxidative stress and DNA damage. Urine samples were analyzed for OP metabolites and 8-hydroxy-2'-deoxyguanosine (8-OH-dG). Lymphocytes were analyzed for oxidative DNA repair activity and DNA damage (Comet assay), and serum was analyzed for lipid peroxides (i.e., malondialdehyde, MDA). Cellular damage in agricultural workers was validated using lymphocyte cell cultures. Urinary OP metabolites were significantly higher in farmworkers and applicators (p<0.001) when compared to controls. 8-OH-dG levels were 8.5 times and 2.3 times higher in farmworkers or applicators (respectively) than in controls. Serum MDA levels were 4.9 times and 24 times higher in farmworkers or applicators (respectively) than in controls. DNA damage (Comet assay) and oxidative DNA repair were significantly greater in lymphocytes from applicators and farmworkers when compared with controls. Markers of oxidative stress (i.e., increased reactive oxygen species and reduced glutathione levels) and DNA damage were also observed in lymphocyte cell cultures treated with an OP. The findings from these in vivo and in vitro studies indicate that organophosphate pesticides induce oxidative stress and DNA damage in agricultural workers. These biomarkers may be useful for increasing our understanding of the link between pesticides and a number of health effects.

Association of metabolic gene polymorphisms with tobacco consumption in healthy controls.

Polymorphisms in genes that encode for metabolic enzymes have been associated with variations in enzyme activity between individuals. Such variations could be associated with differences in individual exposure to carcinogens that are metabolized by these genes. In this study, we examine the association between polymorphisms in several metabolic genes and the consumption of tobacco in a large sample of healthy individuals. The database of the International Collaborative Study on Genetic Susceptibility to Environmental Carcinogens was used. All the individuals who were controls from the case-control studies included in the data set with information on smoking habits and on genetic polymorphisms were selected (n = 20938). Sufficient information was available on the following genes that are involved in the metabolism of tobacco smoke constituents: CYP1A1, GSTM1, GSTT1, NAT2 and GSTP1. None of the tested genes was clearly associated with smoking behavior. Information on smoking dose, available for a subset of subjects, showed no effect of metabolic gene polymorphisms on the amount of smoking. No association between polymorphisms in the genes studied and tobacco consumption was observed; therefore, no effect of these genes on smoking behavior should be expected.

Glutathione S-transferase M1, T1, and P1 polymorphisms and survival among lung cancer patients.

Glutathione S-transferase (GST) enzymes detoxify therapeutic drugs and reactive oxidants, so GST polymorphisms may influence survival after diagnosis of cancer. We evaluated survival according to GST polymorphisms in a population-based series of lung cancer patients. The study subjects (n = 274) were men diagnosed with lung cancer from 1993 through 1996 who participated in a case control study and provided a blood sample for genotyping. The presence of the GSTM1 and GSTT1 genes were assayed by multiplex PCR. Genotype at the GSTP1 Ile(105)Val substitution was determined by PCR and oligonucleotide ligation assay. The study subjects were followed for vital status through 2000, and overall survival was evaluated in Kaplan-Meier survival functions and Cox proportional hazards models. Subjects with the GSTM1 null genotype had shorter survival; the proportion of GSTM1 null subjects surviving at 5 years was 0.20 [95% confidence interval (CI) 0.14-0.27], compared with 0.29 (95% CI 0.22-0.37) for GSTM1 present subjects. The relative risk of death associated with GSTM1 null genotype, adjusted for stage at diagnosis and histology, was 1.36, 95% CI 1.04-1.80. There was no association between GSTT1 or GSTP1 genotype and survival in the overall study population, nor in a subgroup of patients treated with chemotherapy (n = 130). For GSTM1, our results are consistent with a previous study, which also observed that the GSTM1-null genotype, which confers susceptibility to lung cancer, was associated with shorter survival. Future studies of lung cancer survival should take into account GSTM1 genotype as well as investigate underlying mechanisms.

A population-based study of glutathione S-transferase M1, T1 and P1 genotypes and risk for lung cancer.

A deletion polymorphism for glutathione S-transferase M1 (GSTM1) has been related to risk for lung cancer among smokers in some studies but not in others. We examined GSTM1, a GSTT1 deletion polymorphism and a common GSTP1 gene variant (iso-->val), as risk factors for lung cancer in a population-based case-control study of men. Cases (N=274) were males identified from 1993 to 1996 through the Fred Hutchinson Cancer Research Center Cancer Surveillance System registry for western Washington State. Male age-matched controls (N=501) were selected by random-digit dialing. Subjects participated in a telephone interview and blood draw. GSTM1 and GSTT1 were genotyped with a multiplex PCR assay using beta-globin as a positive control, and GSTP1 single nucleotide variant determined with PCR-based oligonucleotide ligation assays. GSTM1 absence was associated with a modest elevation in risk among all cases (odds ratio=1.27, 95% CI 0.91-1.77) and among non-small cell cancers (adenocarcinoma OR=1.58, 95% CI 0.99-2.52; squamous cell OR=1.40, 95% CI 0.83-2.34). Risk associated with GSTM1 null was increased two to sixfold among heavy smokers. GSTT1 was not associated with lung cancer risk and GSTP1 val was non-significantly associated with a modest reduction in risk, particularly among heavy smokers. No specific combination of GST genotypes was particularly associated with risk. These results support previous reports that the GSTM1 null genotype is associated with a modest increase in risk for lung cancer, particularly among heavy smokers, suggest no role for GSTT1 and the need for further study of GSTP1.

Angiotensin II type 1 receptor polymorphisms in the cardiovascular health study: relation to blood pressure, ethnicity, and cardiovascular events.

BACKGROUND: The angiotensin II type 1 receptor A1166C polymorphism has been associated with increased risks of hypertension and myocardial infarction in several small studies. We examined the association between this polymorphism and new-onset hypertension, blood pressure (BP) control, and incident cardiovascular events in a large population-based cohort of older adults. METHODS: Eight hundred self-identified African Americans and 1,371 randomly selected white participants in the Cardiovascular Health Study were genotyped. The median duration of follow-up was 8.1 years. RESULTS: The A1166C polymorphism was not associated with new-onset hypertension, with BP control, or with incident cardiovascular events in the overall population. In white participants, the CC genotype was associated with higher baseline systolic BP and pulse pressure, compared to the AC or AA genotype. In whites with treated hypertension at baseline, compared to the AA genotype, the CC genotype was associated with increased risks of incident congestive heart failure (hazard ratio = 2.5, 95% confidence interval [CI] 1.3-4.9) and incident ischemic stroke (hazard ratio = 2.6, 95% CI 1.1-6.0). These associations were not observed among white participants without treated hypertension, but the interaction of genotype with treated hypertension on ischemic stroke and heart failure was only marginally significant. CONCLUSIONS: On the whole, in this large cohort of older adults, the A1166C polymorphism was not associated with BP control or incident cardiovascular events. The subgroup findings in treated hypertensives need to be confirmed in additional studies.

Meta- and pooled analyses of the effects of glutathione S-transferase M1 polymorphisms and smoking on lung cancer risk.

Susceptibility to lung cancer may in part be attributable to inter-individual variability in metabolic activation or detoxification of tobacco carcinogens. The glutathione S-transferase M1 (GSTM1) genetic polymorphism has been extensively studied in this context; two recent meta-analyses of case-control studies suggested an association between GSTM1 deletion and lung cancer. At least 15 studies have been published after these overviews. We undertook a new meta-analysis to summarize the results of 43 published case-control studies including >18 000 individuals. A slight excess of risk of lung cancer for individuals with the GSTM1 null genotype was found (odds ratio (OR) = 1.17, 95% confidence interval (CI) 1.07-1.27). No evidence of publication bias was found (P = 0.4), however, it is not easy to estimate the extent of such bias and we cannot rule out some degree of publication bias in our results. A pooled analysis of the original data of about 9500 subjects involved in 21 case-control studies from the International Collaborative Study on Genetic Susceptibility to Environmental Carcinogens (GSEC) data set was performed to assess the role of GSTM1 genotype as a modifier of the effect of smoking on lung cancer risk with adequate power. Analyses revealed no evidence of increased risk of lung cancer among carriers of the GSTM1 null genotype (age-, gender- and center-adjusted OR = 1.08, 95% CI 0.98-1.18) and no evidence of interaction between GSTM1 genotype and either smoking status or cumulative tobacco consumption.