Synergistic effects of NAT2 slow and GSTM1 null genotypes on carcinogen DNA damage in the lung

Single-nucleotide polymorphisms as important risk factors of diabetes among Middle East population

Diabetes is a chronic metabolic disorder that leads to the dysfunction of various tissues and organs, including eyes, kidneys, and cardiovascular system. According to the World Health Organization, diabetes prevalence is 8.8% globally among whom about 90% of cases are type 2 diabetes. There are not any significant clinical manifestations in the primary stages of diabetes. Therefore, screening can be an efficient way to reduce the diabetic complications. Over the recent decades, the prevalence of diabetes has increased alarmingly among the Middle East population, which has imposed exorbitant costs on the health care system in this region. Given that the genetic changes are among the important risk factors associated with predisposing people to diabetes, we examined the role of single-nucleotide polymorphisms (SNPs) in the pathogenesis of diabetes among Middle East population. In the present review, we assessed the molecular pathology of diabetes in the Middle East population that paves the way for introducing an efficient SNP-based diagnostic panel for diabetes screening among the Middle East population. Since, the Middle East has a population of 370 million people; the current review can be a reliable model for the introduction of SNP-based diagnostic panels in other populations and countries around the world.

Genetic Polymorphisms of Xenobiotic Metabolizing Genes (GSTM1, GSTT1, GSTP1), Gene-Gene Interaction with Association to Lung Cancer Risk in North India; A Case Control Study

Aim: In this case control study involving, 220 human subjects; polymorphisms in xenobiotic metabolizing genes (GST-M1, -T1 and -P1) and their association to lung cancer risk is being analysed among smokers and nonsmokers. GSTM1 or GSTT1 gene polymorphism and amino acid changes in GSTP1 have been correlated and may be associated to lung cancer risk. Other factor includes exposure to environmental pollutants and life style choices. We have explored gene-gene and gene-environment interaction in the aetiology of lung cancer risk among north Indian population. Patients and Methods: For the study we have collected 120 lung cancer patient blood samples from Kamala Nehru Memorial Cancer Hospital, Allahabad, Uttar Pradesh and 100 matched controls. DNA was isolated and GST-M1 and - T1 genotyping were assessed by multiplex PCR whereas the GSTP1 polymorphism was analysed using restriction fragment length polymorphism. The risk of lung carcinogenesis was assessed using logistic regression analysis calculating the odd ratio (OR) with 95% confidence interval (CI). Results: The risk of lung carcinogenesis was three fold higher for null GSTT1 (OR=3.045, 95%CI=1.750-5.301, p-value <0.001) genotype; whereas other two types; GSTM1 (OR= 1.342, 95% CI=0.788-2.284, p-value=0.270) and GSTP1 (OR=0.806, 95% CI=0.526-1.236, p-value=0.323) showed no association to lung cancer susceptibility respectively. Smokers diagnosed with lung cancer had more null genotypes for GSTT1 (OR=4.773, 95%CI=1.939-11.751, p<0.001). The ‘at risk’ genotype combination GSTM1 (null) /GSTT1 (null) (OR=1.76, 95%CI; 0.920-3.370, p-value=0.03) showed increased susceptibility to lung cancer risk. The genotype combination of GSTT1 (null)/GSTP1 (Ile/Ile) (p=0.009) was associated with increased lung cancer risk. Conclusion: The results of this study suggest that; GSTT1 null genotype were more susceptible for lung cancer risk and smoking increases the susceptibility for lung cancer several folds among the North Indian population. Gene-gene interaction for null genotypes of GSTM1 and GSTT1 were correlated with higher risk of having lung cancer.

Association between the PINX1 and NAT2 polymorphisms and serum lipid levels

Jing nationality is a relatively conservative and isolated minority in China. Little is known about the association of the PIN2/TERF1-interacting telomerase inhibitor 1 (PINX1) and N-acetyltransferase 2 (NAT2) single nucleotide polymorphisms (SNPs) and serum lipid levels in the Chinese populations. This study aimed to clarify the association of 6 SNPs of the PINX1 and NAT2 and serum lipid levels in two Chinese populations. Genotyping of the SNPs was performed in 1236 Han subjects and 1248 Jing participants. Allelic and genotypic frequencies of these variants (except NAT2 rs1799931) were different between the two ethnic groups. The minor allele carriers had higher triglyceride (TG, rs11776767, rs1495743 and rs1799930), low-density lipoprotein cholesterol (rs6601530) levels and the apolipoprotein (Apo)A1/ApoB ratio (rs1495743) in Han nationality; and higher total cholesterol (rs1961456), TG (rs11776767, rs6601530 and rs1495743) and lower ApoA1 (rs6601530 and rs1799931) levels in Jing minority than the minor allele non-carriers. The SNPs were not statistically independent by the multiple-locus linkage disequilibrium analyses. The integrative haplotypes and gene-by-gene (G × G) interactions on serum lipid traits were also observed in the two populations. Association analysis based on haplotypes and G × G interactions might be powerful than single-locus tests. Differences in serum lipid profiles between the two populations might partially be attributed to these SNPs, their haplotypes and G × G interactions.

Bulky DNA Adducts, Tobacco Smoking, Genetic Susceptibility, and Lung Cancer Risk

The generation of bulky DNA adducts consists of conjugates formed between large reactive electrophiles and DNA-binding sites. The term "bulky DNA adducts" comes from early experiments that employed a ³²P-DNA postlabeling approach. This technique has long been used to elucidate the association between adducts and carcinogen exposure in tobacco smoke studies and assess the predictive value of adducts in cancer risk. Molecular data showed increased DNA adducts in respiratory tracts of smokers vs nonsmokers. Experimental studies and meta-analysis demonstrated that the relationship between adducts and carcinogens was linear at low doses, but reached steady state at high exposure, possibly due to metabolic and DNA repair pathway saturation and increased apoptosis. Polymorphisms of metabolic and DNA repair genes can increase the effects of environmental factors and confer greater likelihood of adduct formation. Nevertheless, the central question remains as to whether bulky adducts cause human cancer. If so, lowering them would reduce cancer incidence. Pooled and meta-analysis has shown that smokers with increased adducts have increased risk of lung cancer. Adduct excess in smokers, especially in prospective longitudinal studies, supports their use as biomarkers predictive of lung cancer.

Genetic polymorphisms in biotransformation enzymes for benzo[a]pyrene and related levels of benzo[a]pyrene-7,8-diol-9,10-epoxide-DNA adducts in Goeckerman therapy

Goeckerman therapy (GT) for psoriasis combines the therapeutic effect of crude coal tar (CCT) and ultraviolet radiation (UVR). CCT contains polycyclic aromatic hydrocarbons, some of which can form DNA adducts that may induce mutations and contribute to carcinogenesis. The aim of our work was to evaluate the relationship between concentrations of benzo[a]pyrene-7,8-diol-9,10-epoxide-DNA adducts (BPDE-DNA adducts) and rs4646903 (CYP1A1 gene), rs1048943 (CYP1A1), rs1056836 (CYP1B1), rs1051740 (EPHX1), rs2234922 (EPHX1) and rs8175347 (UGT1A1) polymorphic sites, and GSTM1 null polymorphism in 46 patients with chronic stable plaque psoriasis who underwent GT. The level of BPDE-DNA adducts was determined using the OxiSelect BPDE-DNA Adduct ELISA Kit. Polymerase chain reaction (PCR) and restriction fragment length polymorphism analysis (rs4646903, rs1048943, rs1051740, and rs2234922), fragment analysis (rs8175347), real-time PCR (rs1056836), and digital droplet PCR polymorphism (GSTM1) were used. CYP1B1*1/*1 wild-type subjects and CYP1B1*3/*1 heterozygotes for rs1056836 formed significantly higher amounts of BPDE-DNA adducts than CYP1B1*3/*3 homozygotes (p=0.031 and p=0.005, respectively). Regarding rs1051740, individuals with EPHX1*3/*1 heterozygosity revealed fewer adducts than EPHX1*1/*1 wild-type subjects (p=0.026). Our data suggest that CYP1B1/EPHX1 genotyping could help to predict the risk of DNA damage and to optimize doses of coal tar and UVR exposure in psoriatic patients in whom GT was applied.

Polymorphisms in ERCC1 and ERCC2/XPD genes and carcinogen DNA adducts in human lung

OBJECTIVES

In this exploratory study, we aimed to investigate whether polymorphisms in excision repair cross-complementing group 1 (ERCC1) and excision repair cross-complementing group 2/xeroderma pigmentosum group D (ERCC2/XPD) in the nucleotide excision repair (NER) pathways associated with DNA adducts in human lung tissue. We also analyzed the association stratified by the major histologic subtypes of non-small cell lung cancer (NSCLC): adenocarcinoma (ADC) and squamous cell carcinoma (SQCC).

METHODS

The study population consisted of 107 early stage NSCLC patients from the Massachusetts General Hospital (MGH) in Boston who underwent curative surgical resection. Genotyping was completed for SNPs in ERCC1 [C8092A (rs3212986) and C118T (rs11615)] and ERCC2/XPD [Asp312Asn (rs1799793) and Lys751Gln (rs1052559)] using a PCR-RFLP method and the PCR with fluorescent allele-specific oligonucleotide probes (Taqman). DNA adduct levels were measured as relative adduct levels per 10(10) nucleotides by (32)P-postlabeling in non-tumor lung tissue.

RESULTS

After adjusting for potential confounders, lung DNA adduct levels increased by 103.2% [95% confidence interval (CI), -11.5 to 366.6] for ERCC2/XPD rs1799793AA genotype compared with their corresponding wild type homozygous genotypes in overall NSCLC, but the difference did not reach statistical significance. When we stratified by the subtypes of NSCLC, we found that DNA adducts levels in lung increased by 204.9% (95% CI, 0.8 to 822.2, P=0.059) for ERCC2/XPD rs1799793AA genotype in subjects with SQCC and the trend was statistically significant (P for trend=0.0489).

CONCLUSIONS

Polymorphisms in ERCC2/XPD Asp312Asn may be associated with increased DNA adduct levels in the lung, especially among subjects with SQCC. Further large scale studies are needed to confirm our findings.

N-acetyltransferase 1 and 2 polymorphisms and risk of diabetes mellitus type 2 in a Saudi population

BACKGROUND AND OBJECTIVES

There have been inconsistent reports on N-acetyltransferase (NAT) gene polymorphism in type 2 diabetes mellitus (T2DM), and data is particularly limited in the Arab population. Therefore, the main objective of this study was to identify whether the genetic polymorphisms of NAT1 and NAT2 play a role in susceptibility to T2DM in the Saudi population.

DESIGN AND SETTINGS

A population-based, prospective genetic association case-control study on a Saudi population.

PATIENTS AND METHODS

Whole blood, anthropometric measurements and biochemistry data were collected from 369 Saudi individuals (186 T2DM patients and 183 healthy controls). DNA was isolated from the blood. Polymorphism of NAT1 and NAT2 SNPs [NAT2*7B, rs1041983(C > T); NAT2*7, rs1799931(G > A); NAT2*6A, rs1799930(G > A); NAT2*5A, rs1799929(C > T); and NAT1*11A, rs4986988(C > T)] were evaluated by allelic discrimination using real-time PCR.

RESULTS

Subjects with T2DM had a significantly increased body mass index (BMI), waist circumference, sys.tolic and diastolic blood pressure, glucose, triglycerides, and LDL-cholesterol compared with healthy controls (P < .05). The rs1799931(G > A) genotype was detected in the control population but not in the T2DM population (P < .001). The wild type (G) allele frequency was higher in T2DM than controls (P=.038). The mutant allele (A) in rs1799931(G > A) had a protective effect for T2DM (OR 0.32, 95% CI 0.16-0.62; P=.001). Regression analysis showed that BMI, systolic BP and triglycerides are potential risk factors for T2DM.

CONCLUSION

The genotypes as well as the individual alleles of rs1799931(G > A) differed significantly be.tween the case and control populations. The variation in the data reported so far suggest that polymorphism of the NAT gene may vary among different geographical areas. Environmental or dietary factors may also contribute to disease manifestation.

NAT2 genetic variations among South Indian populations

The N-acetyltransferases (NATs) are xenobiotic-metabolizing enzymes involved in the metabolism of drugs, environmental toxins and the aromatic amine carcinogens present in cigarette smoke. Genetic variations in NAT2 have long been recognized as the cause of variable enzymatic activity or stability, leading to slow or rapid acetylation. In the present study, we genotyped three single-nucleotide polymorphisms (SNPs) from the NAT2 gene (rs1799929, rs1799930 and rs1799931), using TaqMan allelic discrimination, among 212 individuals from six major South Indian populations and compared the results with other available Indian and worldwide data. All three of the markers followed Hardy-Weinberg equilibrium and were highly polymorphic in the studied populations. The constructed haplotypes showed a high level of heterozygosity. All of the populations in the present study commonly shared only four haplotypes out of the eight possible three-site haplotypes. The haplotypes exhibited fairly high frequencies across multiple populations, where three haplotypes were shared by all six populations with a cumulative frequency ranging from 88.2% (Madiga) to 97.0% (Balija). We also observed a tribal-specific haplotype. A strong linkage disequilibrium (LD) between rs1799929 and rs1799930 was consistent in all of the studied populations, with the exception of the Madiga. A comparison of the genomic regions 20-kb up- and downstream of rs1799930 in a large number of worldwide samples showed a strong LD of this SNP with another NAT2 SNP, rs1112005, among the majority of the populations. Moreover, our lifestyle test (hunter-gatherer versus agriculturist) in comparison with the NAT2 variant suggested that two of the studied populations (Balija and Madiga) have likely shifted their diet more recently.

Variation in PAH-related DNA adduct levels among non-smokers: the role of multiple genetic polymorphisms and nucleotide excision repair phenotype

Polycyclic aromatic hydrocarbons (PAHs) likely play a role in many cancers even in never-smokers. We tried to find a model to explain the relationship between variation in PAH-related DNA adduct levels among people with similar exposures, multiple genetic polymorphisms in genes related to metabolic and repair pathways, and nucleotide excision repair (NER) capacity. In 111 randomly selected female never-smokers from the Golestan Cohort Study in Iran, we evaluated 21 SNPs in 14 genes related to xenobiotic metabolism and 12 SNPs in eight DNA repair genes. NER capacity was evaluated by a modified comet assay, and aromatic DNA adduct levels were measured in blood by32P-postlabeling. Multivariable regression models were compared by Akaike's information criterion (AIC). Aromatic DNA adduct levels ranged between 1.7 and 18.6 per 10(8) nucleotides (mean: 5.8 ± 3.1). DNA adduct level was significantly lower in homozygotes for NAT2 slow alleles and ERCC5 non-risk-allele genotype, and was higher in the MPO homozygote risk-allele genotype. The sum of risk alleles in these genes significantly correlated with the log-adduct level (r = 0.4, p < 0.001). Compared with the environmental model, adding Phase I SNPs and NER capacity provided the best fit, and could explain 17% more of the variation in adduct levels. NER capacity was affected by polymorphisms in the MTHFR and ERCC1 genes. Female non-smokers in this population had PAH-related DNA adduct levels three to four times higher than smokers and occupationally-exposed groups in previous studies, with large inter-individual variation which could best be explained by a combination of Phase I genes and NER capacity.

Genetic susceptibility to lung cancer--light at the end of the tunnel?

Lung cancer is one of the most common and deadliest cancers in the world. The major socio-environmental risk factor involved in the development of lung cancer is cigarette smoking. Additionally, there are multiple genetic factors, which may also play a role in lung cancer risk. Early work focused on the presence of relatively prevalent but low-penetrance alterations in candidate genes leading to increased risk of lung cancer. Development of new technologies such as genomic profiling and genome-wide association studies has been helpful in the detection of new genetic variants likely involved in lung cancer risk. In this review, we discuss the role of multiple genetic variants and review their putative role in the risk of lung cancer. Identifying genetic biomarkers and patterns of genetic risk may be useful in the earlier detection and treatment of lung cancer patients.

Molecular medicine and the development of cancer chemopreventive agents

Chemoprevention is effective in inhibiting the onset of cancer in experimental animal models, but the transferability of similar results to humans is questionable. Therefore, reliable intermediate molecular biomarkers are needed to evaluate the efficacy of chemopreventive agents before the onset of cancer. The use of genomic biomarkers is limited by their poor predictive value. Although post-genomic biomarkers (i.e., gene-expression analyses) are useful for evaluating the safety, efficacy, and mechanistic basis of chemopreventive agents, the biomarkers are often poorly related to the phenotype, due to posttranscriptional regulation. Proteome analyses can evaluate preclinical phenotype alterations, but only at low protein counts. MicroRNA alterations, which are essential for the development of cancer, may be modulated by chemopreventive agents. Furthermore, microRNA delivery may be used to counteract carcinogenesis. Exposure to cigarette smoke induces microRNA let-7 downregulation and cell proliferation that can be converted to cell growth arrest and apoptosis upon let-7a transfection. Therefore, microRNAs are reliable biomarkers for evaluating chemoprevention efficacy and may be used to counteract carcinogenesis.

MTHFR polymorphisms, folate intake and carcinogen DNA adducts in the lung

The methylenetetrahydrofolate reductase (MTHFR) genes and folate in one-carbon metabolism are essential for DNA methylation and synthesis. However, their role in carcinogen DNA damage in target lung tissue, a dosimeter for cancer risk, is not known. Our study aimed to investigate the association between genetic and nutritional one-carbon metabolism factors and DNA adducts in target lung. Data on 135 lung cancer cases from the Massachusetts General Hospital were studied. Genotyping was completed for MTHFR C677T (rs1801133) and A1298C (rs1801131). Information on dietary intake for one-carbon related micronutrients, folate and other B vitamin was derived from a validated food frequency questionnaire. DNA adducts in lung were measured by (32) P-postlabeling. After adjusting for potential confounders, DNA adduct levels in lung significantly increased by 69.2% [95% confidence interval (CI), 5.5% to 171.5%] for the MTHFR 1298AC+CC genotype. The high risk group, combining the A1298C (AC+CC) plus C677T (CT+TT) genotypes, had significantly enhanced levels of lung adducts by 210.7% (95% CI, 21.4% to 695.2%) in contrast to the A1298C (AA) plus C677T (CC) genotypes. Elevation of DNA adduct was pronounced-111.3% (95% CI, -3.0 to 360.5%) among 1298AC+CC patients, who consumed the lowest level of folate intake as compared to 1298AA individuals with highest tertile of intake. These results indicate that DNA adducts levels are influenced by MTHFR polymorphisms and low folate consumption, suggesting an important role of genetic and nutritional factors in protecting DNA damage from lung carcinogen in at-risk populations.

Influence of CYP2C9, GSTM1, GSTT1 and NAT2 genetic polymorphisms on DNA damage in workers occupationally exposed to organophosphate pesticides

Previous studies have revealed that organophosphate pesticides (OPs) are primarily metabolized by xenobiotic metabolizing enzymes (XMEs). Very few studies have explored genetic polymorphisms of XMEs and their association with DNA damage in pesticides-exposed workers. Present study was designed to determine the influence of CYP2C9, GSTM1, GSTT1 and NAT2 genetic polymorphisms on DNA damage in workers occupationally exposed to OPs. We examined 268 subjects including 134 workers occupationally exposed to OPs and an equal number of normal healthy controls. The DNA damage was evaluated using alkaline comet assay and genotyping was done using individual polymerase chain reaction (PCR) or polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). Acetylcholinesterase and paraoxonase activity were found to be significantly lowered in workers as compared to control subjects which were analyzed as biomarkers of toxicity due to OPs exposure (p<0.001). Workers showed significantly higher DNA tail moment (TM) compared to control subjects (14.32±2.17 vs. 6.24±1.37 tail % DNA, p<0.001). GSTM1 null genotype was found to influence DNA TM in workers (p<0.05). DNA TM was also found to be increased with concomitant presence of NAT2 slow acetylation and CYP2C9*3/*3 or GSTM1 null genotypes (p<0.05). DNA TM was found increased in NAT2 slow acetylators with mild and heavy smoking habits in control subjects and workers, respectively (p<0.05). The results of this study suggest that GSTM1 null genotypes, and an association of NAT2 slow acetylation genotypes with CYP2C9*3/*3 or GSTM1 null genotypes may modulate DNA damage in workers occupationally exposed to OPs.

GSTM1 null genotype in COPD and lung cancer: evidence of a modifier or confounding effect?

Background

Studies over the past two decades have reported associations between GSTM1 (glutathione S-transferase mu 1) null genotype and chronic obstructive pulmonary disease (COPD) or lung cancer. However, a modifier or confounding effect from COPD mediating the GSTM1 association with lung cancer has not been previously explored.

Aim and methods

This variant was examined in a case-control study of current or former smokers with COPD (n = 669), lung cancer (n = 454), or normal lung function (n = 488). Sex, age, and smoking history were comparable between groups.

Results

The GSTM1 null genotype was found to be more frequent in smokers with COPD alone (odds ratio [OR] 1.30, 95% confidence interval [CI] 1.02–1.66, P = 0.031) and lung cancer (OR 1.26, 95% CI 0.96–1.65, P = 0.083) than in matched smokers with normal lung function (62%, 61%, and 56%, respectively). However, when smokers with lung cancer were subgrouped according to the presence of COPD, then the association with all COPD subjects (OR 1.34, 95% CI 1.07–1.70, P = 0.010) and with COPD and lung cancer (OR 1.50, 95% CI 1.06–2.12, P = 0.018) continued to be significant while that with lung cancer only was reduced (OR 1.11, 95% CI 0.78–1.56, P = 0.55). These associations were independent of age, sex, height, lung function, and smoking history.

Conclusion

Findings suggest that COPD is an important subphenotype of lung cancer and may underlie previously reported associations with the GSTM1 null genotype.

Role of genetic polymorphisms of CYP1A1, CYP3A5, CYP2C9, CYP2D6, and PON1 in the modulation of DNA damage in workers occupationally exposed to organophosphate pesticides

Organophosphate pesticides (OPs) are primarily metabolized by several xenobiotic metabolizing enzymes (XMEs). Very few studies have explored genetic polymorphisms of XMEs and their association with DNA damage in pesticide-exposed workers. The present study was designed to determine the role of genetic polymorphisms of CYP1A1, CYP3A5, CYP2C9, CYP2D6, and PON1 in the modulation of DNA damage in workers occupationally exposed to OPs. We examined 284 subjects including 150 workers occupationally exposed to OPs and 134 normal healthy controls. The DNA damage was evaluated using the alkaline comet assay and genotyping was done using PCR-RFLP. The results revealed that the PONase activity toward paraoxonase and AChE activity was found significantly lowered in workers as compared to control subjects (p<0.001). Workers showed significantly higher DNA damage compared to control subjects (14.37±2.15 vs. 6.24±1.37 tail% DNA, p<0.001). Further, the workers with CYP2D6*3PM and PON1 (QQ and MM) genotypes were found to have significantly higher DNA damage when compared to other genotypes (p<0.05). In addition, significant increase in DNA damage was also observed in workers with concomitant presence of certain CYP2D6 and PON1 (Q192R and L55M) genotypes which need further extensive studies. In conclusion, the results indicate that the PON1 and CYP2D6 genotypes can modulate DNA damage elicited by some OPs possibly through gene-environment interactions.

Seasonal variations in the levels of PAH-DNA adducts in young adults living in Mexico City

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous components of polluted air. The Mexico City Metropolitan Area (MCMA), one of the most densely populated areas in the world, is 2240 m above sea level. At this altitude, less oxygen is available, making combustion less efficient and therefore producing more PAH pollutants. According to the Automatic Monitoring Network in Mexico City (RAMA, for its Spanish initials; http://www.sma.df.gob.mx/simat2/informaciontecnica/index.php?opcion=5&opciondifusion_bd=90), which performs environmental monitoring, the critical air pollutants in Mexico City are ozone and particulate matter (PM). PM emissions increase during the dry season (winter to spring) and decrease during the rainy season (summer to autumn). The bioactivation of some PAHs produces reactive metabolites that bind to DNA, and the presence of elevated levels of PAH-DNA adducts in tissues such as blood lymphocytes represents an elevated risk for the development of cancer. We have compared the levels of PAH-DNA adducts and the percentage of cells with chromosomal aberrations (CWAs) using a matched set of peripheral blood lymphocytes obtained on two separate occasions from young non-smoking inhabitants of the MCMA (n = 92) during the 2006 dry season and the following rainy season. PAH-DNA adducts were analysed using the r7, t8-dihydroxy-t-9, 10-oxy-7,8,9,10-tetrahydrobenzo[a]pyrene (BPDE)-DNA chemiluminescence immunoassay (CIA). The percentages of CWA were determined in cultured lymphocytes from the same individuals. Both DNA adduct levels and chromosomal aberrations were tested for correlation with lifestyle and the polymorphisms of cytochromes P450 CYP1A1 and CYP1B1 as well as glutathione-S-transferases GSTM1 and GSTT1. The levels of PAH-DNA adducts were significantly higher (P < 0.001) in the dry season (10.66 ± 3.05 per 10(9) nt, n = 92) than during the rainy season (9.50 ± 2.85 per 10(9) nt, n = 92) and correlated with the seasonal levels of particulate matter with a diameter of ≤ 10 μm (PM(10)). The percentage of CWA was not seasonally related; however, significant associations between the number of risk alleles and adduct levels in the dry (R = 0.298, P = 0.048) and in the wet seasons (R = 0.473, P = 0.001) were observed.

Genetic modifiers of carcinogen DNA adducts in target lung and peripheral blood mononuclear cells

Measurement of carcinogen DNA adducts in blood has been used as a surrogate for the target lung tissue. We aimed to examine whether genetic polymorphisms in several metabolic pathway genes modify the relation between DNA adducts in target lung and blood. One hundred and thirty-five early-stage lung cancer patients from the Massachusetts General Hospital were studied. DNA adducts were measured by the (32)P-postlabeling assay in lung and blood mononuclear cells (MNCs) in a subset of 53 who had paired blood samples. Single-nucleotide polymorphisms (SNPs) were assessed in genes involved in phase II (GSTs, NAT2, EPHX and NQO1), DNA repair (ERCC1, ERCC2 and XRCC1) and DNA methylation (MTHFR C677T and A1298C) pathways. There was a significant correlation between DNA adduct levels in lung and blood within the different genotypes, with one exception. Significant modifications in adducts were found by variants in genes for phase II metabolism [NAT2 (1.51 for rapid versus 0.76 for slow, P = 0.022)], DNA repair [ERCC1 C118T (P = 0.014), ERCC2 (P = 0.003) and XRCC1 (P = 0.025)] and MTHFR [C677T (P = 0.005) and A1298C (P = 0.005)]. The relation between DNA adducts in blood MNCs and target lung tissue was significantly modified by the single-nucleotide polymorphisms in the three main pathways. Despite the relatively small sample size, our results suggest that genetic factors may need to be considered when assessing the association of DNA adducts using surrogate tissue in studies of lung cancer. Further studies are needed to better understand their role and the mechanisms.