Effects of occupation, lifestyle and genetic polymorphisms of CYP1A1, CYP2E1, GSTM1 and GSTT1 on urinary 1-hydroxypyrene and 2-naphthol concentrations

This study was undertaken to determine the effects of occupation, lifestyle and the genetic polymorphisms of cytochrome P450 1A1 (CYP1A1), cytochrome P450 2E1 (CYP2E1) and glutathione S-transferases micro1 (GSTM1) and 1 (GSTT1) on the concentrations of urinary 1-hydroxypyrene (1-OHP) and 2-naphthol among Korean coke oven workers and university students. The study subjects included 90 coke oven workers and 128 university students. A questionnaire was used to obtain detailed data about the work area, smoking habits and food intake of subjects. Associations between urinary polycyclic aromatic hydrocarbon (PAH) concentrations and occupation, smoking status, total airborne PAH level and genetic polymorphisms were tested. Urinary 1-OHP and 2-naphthol concentrations were higher in coke oven workers than in students and correlated significantly with work area. Urinary 2-naphthol concentrations increased with an increase in the level of cigarette smoking in students. Total airborne PAH level correlated with urinary 1-OHP concentration in coke oven workers. Urinary 1-OHP and 2-naphthol concentrations were higher in coke oven workers with the c1/c2 or c2/c2 genotype of CYP2E1 than in those with the c1/c1 genotype. Urinary 2-naphthol concentrations were higher in GSTM1-null workers than in GSTM1-positive workers. In multiple regression analysis CYP2E1 was a significant factor determining urinary 1-OHP concentrations in coke oven workers. CYP2E1 and GSTM1 were significant determinants for urinary 2-naphthol concentrations in coke oven workers and GSTM1 and smoking were prognosticators among university students. Urinary 1-OHP is a better indicator of occupational exposure to PAH in coke oven workers than 2-naphthol, whereas urinary 2-naphthol may be more sensitive for non-occupational inhalation exposure to PAH. In occupationally exposed populations CYP2E1 and GSTM1 appear to play an important role in the metabolism of pyrene and naphthalene. In individuals not occupationally exposed to PAHs GSTM1 and smoking seem to influence the urinary concentration of 2-naphthol.     

CYP1A1 and GSTM1 polymorphisms affect urinary 1-hydroxypyrene levels after PAH exposure

Certain human biotransformation enzymes have been implicated in the formation and scavenging of the ultimate reactive metabolites, the diolepoxides, from polycyclic aromatic hydrocarbons (PAHs). In the present study, performed on aluminum smelter workers, we have analyzed airborne PAH, the pyrene metabolite 1-hydroxypyrene (1-OHP) in urine, and genotypes for biotransformation enzymes involved in PAH metabolism. The aim was to evaluate the correlation between external exposure and biomarkers of exposure and to investigate to what extent genetic polymorphism in metabolic enzymes can explain interindividual variation in urinary 1-OHP levels. DNA was prepared from blood samples from 98 potroom workers and 55 controls and altogether eight polymorphisms in the CYP1A1, mEH, GSTM1, GSTP1 and GSTT1 genes were analyzed. The 1-OHP excretion was found to correlate significantly (P 100-fold) and univariate and multivariate regression analyses were used to find the variables that could determine differences in excretion. The variation could, to some degree, be explained by differences in exposure to airborne particulate-associated PAHs, the use of personal respiratory protection devices, smoking habits and genetic polymorphisms in the cytochrome P450 1A1, GSTM1 and GSTT1 enzymes. The part of the variance that could be explained by differences in biotransformation genotypes seemed to be of the same order of magnitude as the variance explained by differences in exposure. In the control group as well as in the occupationally exposed group, the highest 1-OHP levels were observed in individuals carrying the CYP1A1 Ile/Val genotype who were also of the GSTM1 null genotype. The results show that urinary 1-OHP is a sensitive indicator of recent human exposure to PAHs and that it may also to some extent reflect the interindividual variation in susceptibility to PAHs.     

Polymorphisms of glutathione-S-transferase genes (GSTP1, GSTM1 and GSTT1) and prostate-cancer risk

Several polymorphic glutathione-S-transferase (GST) enzymes are involved in the metabolism of a number of potential prostate carcinogens and are thought to engage in the transport of steroid hormones. A case-control study was conducted to determine the association of the GSTP1, GSTM1 and GSTT1 polymorphisms and prostate-cancer risk. The study population consisted of 166 patients with previously untreated, histologically proven prostate cancer and 166 age-matched control patients with benign prostatic hyperplasia (BPH), all of them Caucasians. In the GSTP1 gene, 2 polymorphic alleles, GSTP1*B and GSTP1*C, have been described in addition to the wild-type allele, GSTP1*A. Both polymorphic GSTP1 alleles have an A-to-G transition in exon 5, causing an isoleucine-to-valine change. The GSTP1*C allele has an additional transition from C to T. For GSTM1 as well as GSTT1, the polymorphic allele is a deletion of the gene. The proportion of individuals homozygous for the GSTP1 variant alleles (GSTP1*B/*B, GSTP1*B/*C and GSTP1*C/*C) was significantly lower in prostate-cancer patients (4.8%) than in BPH controls (14.5%), and the odds ratio (OR) was 0.24 [95% confidence interval (CI) = 0.09-0.61). The heterozygous genotypes (GSTP1*A/*B and GSTP1*A/*C) were also lower in the cancer group, though this was not significant. On the contrary, no significant effect on prostate-cancer risk was detectable for either GSTM1 (OR = 0.86, 95% CI = 0.55-1.36) or GSTT1 (OR = 0.78, 95% CI = 0.43-1.42). Of the polymorphic GSTs, GSTP1 is the most interesting candidate as a biomarker for prostate-cancer risk as we found a 76% reduced risk in men homozygous for the polymorphic GSTP1 alleles compared to those with wild-type GSTP1.     

GSTM1, GSTT1, and GSTP1 polymorphism and lung cancer risk in relation to tobacco smoking

The impact of genetic polymorphisms in GSTM1, GSTP1 or GSTT1 on susceptibility to lung cancer has received particular interest since these enzymes play a central role in detoxification of major classes of tobacco carcinogens. In the current German study we investigated the role of GSTM1, GSTT1 and GSTP1 polymorphisms as a genetic modifier of risk for individuals with lung cancer as susceptible genotypes especially in relation to tobacco smoking. The GSTM1, the GSTP1 as well as GSTT1-polymorphism were determined by real time PCR analysis in 446 lung cancer patients and 622 controls. The observed allele frequencies of the GSTP1 polymorphism in the population were within the range described for Caucasians. Multivariate analyses of lung cancer patients, who carried at least one mutant variant allele of GSTP1 (OR=1.03; 95%-CI: 0.76-1.39) did not show any elevated risks. GSTM1 or GSTT1 null-genotypes were found in 47.3% resp. 18.5% of the controls and in 52.5% resp. 16.8% of the cancer patients. The estimated risk of the GSTM1 null genotype for lung cancer was OR=1.34 (95%-CI: 0.99-1.81) and for the GSTT1 null genotype OR=0.88 (95%-CI: 0.59-1.32). When analyzed by histology no individual subtype of lung cancer was strongly associated with the polymorphisms. Lung cancer risk rose significantly with higher cumulative cigarette consumption confirming the association with smoking-related lung cancer risk. Stratified analysis between tobacco smoking and variant genotypes revealed for heavy smokers (>60 pack-years) increasing risks at the presence for at least one copy of the GSTP1 variant allele OR=50.56 (95%-CI: 15.52-164.79). The corresponding risks for GSTM1 null genotypes were OR=112.08 (95%-CI: 23.02-545.71) and for the GSTT1 null-genotype OR=158.49 (95%-CI: 17.75-1415.06) in smokers >60 pack-years. Analysing the interaction between tobacco smoking and the genotypes, combined smoking and having the susceptible genotypes did not show a joint effect. In this study polymorphisms of the GSTM1, GSTT1 or GSTP1 had no relevant modifying effect on lung cancer risk and cumulative smoking dose.     

Genetic effects on urinary 1-hydroxypyrene levels in a Korean population

Urinary 1-hydroxypyrene (1-OHP) has been used as a biomarker for assessing the level of exposure to environmental carcinogenic polycyclic aromatic hydrocarbons (PAHs). In order to perform the appropriate biological monitoring for examining the level of exposure to PAHs, this study investigated whether or not genetic polymorphisms of the metabolic enzymes, which might be involved in the metabolism of pyrene, affected the urinary 1-OHP levels in a population of 661 Koreans (male, 63%; female, 37%; mean age, 36.5 +/- 11.1 years) who were not occupationally exposed to PAHs. Urinary 1-OHP was detected in 76% of the subjects (range 0.001-3.8 micro g/l). Among the physical and lifestyle factors, cigarette-smoking was found to be associated with the urinary 1-OHP levels (P < 0.05). After adjusting for these factors, we found that the GSTT1 genotypes affected the urinary 1-OHP levels, i.e. the GSTT1 present subjects had approximately 1.5 times the urinary 1-OHP level than the GSTT1 null subjects (P < 0.05). In the case of the subjects who were also GSTM1 null, this trend became stronger, i.e. the GSTT1 present subjects had approximately 2 times the urinary 1-OHP level (P < 0.01). However, the genetic polymorphism of the other metabolic enzymes, cytochrome P-450 (CYP)1A1, CYP1B1 and GSTM1 alone, did not affect the urinary 1-OHP level. Therefore, this study suggests that the GSTT1 genetic polymorphism has the potential to affect the biological monitoring of PAHs with urinary 1-OHP, and might act as a genetic factor in PAH-related toxicity.     

Influence of CYP1A1, GSTM1, GSTT1, and NQO1 genotypes and cumulative smoking dose on lung cancer risk in a Swedish population.

The major identified risk factor for lung cancer is tobacco smoking. We identified previously the possible modifying influence of CYP1A1 and GSTM1 polymorphisms on lung cancer risk in a Swedish population. The present study, extended by several study subjects and with analyses for polymorphisms in GSTT1 and NQO1, includes 524 lung cancer cases and 530 control subjects. No evidence for an influence of genetic polymorphisms in CYP1A1, GSTM1, GSTT1, and NQO1 on lung cancer risk overall was found. In smokers, there was, however, a suggestion that the variant CYP1A1 and NQO1 genotypes may confer an increased risk for squamous cell carcinoma. In ever smokers, the homozygously deleted GSTM1 (GSTM1*O/*O) genotype was significantly associated with increased risk of small cell carcinoma (adjusted odds ratio 2.72, 95% confidence interval 1.32-5.90). The risks noted for the variant CYP1A1 genotypes and the GSTM1*O/*O genotype seemed to be restricted to light smokers. The GSTT1*O/*O genotype also appeared to be a possible risk factor in light smokers, whereas, in heavy smokers, this genotype was associated with decreased risk for lung cancer overall (odds ratio 0.36, 95% confidence interval 0.13-0.99). Due to the multiple comparisons made, we cannot exclude the possibility that some of these associations may represent chance findings.     

Benzo(a)pyrene diolepoxide (BPDE)-DNA adduct levels in leukocytes of smokers in relation to polymorphism of CYP1A1, GSTM1, GSTP1, GSTT1, and mEH.

Benzo(a)pyrene [B(a)P] diolepoxide (BPDE)-DNA adducts were measured in the leukocytes of 41 healthy smokers using high-performance liquid chromatography coupled with a fluorimetric detector. The correlation between exposure to B(a)P through smoking and BPDE-DNA adduct levels was poor (r = 0.31), although subjects in the high exposure group [B(a)P > 50 ng/d] had a slightly higher level of adducts compared with the less exposed group (mean +/- SE, 1.70 +/- 0.3 versus 1.09 +/- 0.1; P = 0.057). We studied the effect on BPDE-DNA adducts of individual variations in genes controlling B(a)P metabolism, classifying subjects in "low-risk" and "high-risk" genotypes for smoking-related B(a)P DNA damage. The high-risk group included subjects characterized by a combination of increased B(a)P activation [cytochrome P450 1A1 (CYP1A1) MspI and/or exon 7 Ile462Val allele variants and microsomal epoxide hydrolase (mEH) fast activity] and decreased deactivation ability [presence of glutathione S-transferase M1 (GSTM1) null allele and wild-type glutathione S-transferase P1 (GSTP1)]. The low-risk group included smokers with lower B(a)P activation (wild-type CYP1A1, low or intermediate mEH activity) and higher deactivation capacity (active GSTM1, GSTP1 Ile105Val allele). Subjects in the low-risk group had lower levels of BPDE-DNA adducts compared with subjects in the high-risk genotype group; this difference was significant using two markers (CYP1A1 and GSTM1, median +/- SD, 0.77 +/- 1.16 versus 1.89 +/- 0.39; P = 0.03) or three markers (CYP1A1, GSTM1, and GSTP1, median +/- SD, 0.66 +/- 0.93 versus 1.43 +/- 1.17; P = 0.013). The discrimination between groups was reduced when including mEH as an additional marker (P = 0.085). In conclusion, CYP1A1, GSTM1, and GSTP1 genotyping seems to be a risk predictor of BPDE-DNA adduct formation in leukocytes.     

Human lung microsomal cytochrome P4501A1 (CYP1A1) activities: impact of smoking status and CYP1A1, aryl hydrocarbon receptor, and glutathione S-transferase M1 genetic polymorphisms.

There are numerous conflicting epidemiological studies addressing correlations between cytochrome P450 1A1 (CYP1A1) genetic polymorphisms and lung cancer susceptibility, with associations plausibly linked to alterations in carcinogen bioactivation. Similarly, correlations between aryl hydrocarbon receptor gene (AHR) codon 554 genotype and CYP1A1 inducibility are controversial. The objective of this study was to determine whether smoking status, and CYP1A1, AHR, and glutathione S-transferase M1 gene (GSTM1) polymorphisms correlate with altered CYP1A1 activities. Lung microsomal CYP1A1-catalyzed 7-ethoxyresorufin O-dealkylation (EROD) activities were much higher in tissues from current smokers (n = 46) than in those from non-/former smokers (n = 24; 12.11 +/- 13.46 and 0.77 +/- 1.74 pmol/min/mg protein, respectively, mean +/- SD; P < 0.05). However, EROD activities in lung microsomes from current smokers CYP1A1*1/1 (n = 33) and heterozygous MspI variant CYP1A1*1/2A (n = 10) were not significantly different (12.23 +/- 13.48 and 8.23 +/- 9.76 pmol/min/mg protein, respectively, P > 0.05). Three current smokers were heterozygous variant CYP1A1*1/2B (possessing both *2A and *2C alleles), and exhibited activities similar to individuals CYP1A*1/1. One current smoker was heterozygous variant CYP1A1*4 and exhibited activities comparable with individuals CYP1A1*1/1 at that locus. EROD activities in microsomes from current smokers AHR(554)Arg/Arg (n = 41) and heterozygous variant AHR(554)Arg/Lys (n = 5) were not significantly different (12.13 +/- 13.56 and 12.01 +/- 14.23 pmol/min/mg protein, respectively; P > 0.05). Furthermore, microsomal EROD activities from current smokers with the GSTM1-null genotype (n = 28) were not significantly different from those (n = 18) carrying at least one copy of GSTM1 (12.61 +/- 14.24 and 11.34 +/- 12.53 pmol/min/mg protein, respectively; P > 0.05). Additionally, when genotypic combinations of CYP1A1, AHR, and GSTM1 were assessed, there were no significant effects on EROD activity. On the basis of microsomal enzyme activities from heterozygotes, CYP1A1*1/2A, CYP1A1*1/2B, CYP1A1*1/4, and AHR(554) Arg/Lys variants do not appear to significantly affect CYP1A1 activities in human lung, and we observed no association between CYP1A1 activity and the GSTM1-null polymorphism.     

Colorectal cancer and genetic polymorphisms of CYP1A1, GSTM1 and GSTT1: a case-control study in the Grampian region of Scotland

Cytochrome P-450 CYP1A1 is involved in the metabolism of polycyclic aromatic hydrocarbons (PAHs) that are derived from meat intake and tobacco smoking. Expression of the CYP1A1 gene is induced by compounds present in cruciferous vegetables. The glutathione S-transferases play a central role in the detoxification of carcinogens, including PAHs. We investigated the association between colorectal cancer and three variants (CYP1A1*2A, CYP1A1*2C, CYP1A1*4) of the CYP1A1 gene, and homozygosity for the null deletion of the GSTM1 and GSTT1 genes, and the joint effects of these genotypes and smoking, meat intake and intake of green leafy vegetables in a population-based study of 264 cases and 408 controls in Northeast Scotland. There was an inverse association with the CYP1A1*4 (m4) variant (OR 0.3, 95% CI 0.13-0.70). The OR for the CYP1A1*2C (m2) variant was 1.3 (95% CI 0.59-2.91), which is similar to a combined estimate for previous studies (OR 1.2, 95% CI 0.95-1.41). We observed no association with the CYP1A1*2A (m1) variant, or the GSTM1 and GSTT1 polymorphisms. Significant interactions between all 3 CYP1A1 variants and meat intake, and between the m1 and m2 variants and intake of green leafy vegetables, were observed. There was no evidence of interaction between CYP1A1 and smoking, and no evidence of interaction between the GSTM1 or GSTT1 polymorphisms and smoking, meat intake, green leafy vegetable intake, CYP1A1 variants or each other.     

Meta- and pooled analyses of GSTM1, GSTT1, GSTP1, and CYP1A1 genotypes and risk of head and neck cancer.

Sequence variation in the GSTM1, GSTT1, GSTP1, and CYP1A1 genes may potentially alter susceptibility to head and neck cancers, although evidence from previous studies has not been consistent. To explore these associations, we conducted a meta-analysis of 31 published case-control studies (4635 cases and 5770 controls) and a pooled analysis of original data from nine published and two unpublished case-control studies (2334 cases and 2766 controls). In the meta-analysis, the summary odds ratios (ORs) for head and neck cancer were 1.23 [95% confidence interval (95% CI), 1.06-1.42] for the GSTM1 null genotype, 1.17 (95% CI, 0.98-1.40) for the GSTT1 null genotype, 1.10 (95% CI, 0.92-1.31) for carrying the GSTP1 Val105 allele, and 1.35 (95% CI, 0.95-1.82) for carrying the CYP1A1 Val462 allele. The pooled analysis ORs were 1.32 (95% CI, 1.07-1.62) for the GSTM1 null genotype, 1.25 (95% CI, 1.00-1.57) for the GSTT1 null genotype, 1.15 (95% CI, 0.86-1.53) for carrying the GSTP1 Val105 allele, and 0.98 (95% CI, 0.75-1.29) for carrying the CYP1A1 Val462 allele. Increasing risk of head and neck cancer was observed with inheritance of increasing numbers of modest risk genotypes at the three GST loci (P for trend = 0.04), with the combination of carrying the GSTM1 null, GSTT1 null, and GSTP1 Val105 alleles conferring an OR of 2.06 (95% CI, 1.11-3.81). In conclusion, both the meta- and pooled analysis support modest associations of GSTM1 and GSTT1 genotypes with head and neck cancer risk, and our pooled analysis supports the notion of greater risk when genotypes at multiple GST loci are considered in a multigenic model.     

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.     

Genetic polymorphism of xenobiotic metabolizing enzymes among Chinese lung cancer patients

Polymorphisms in xenobiotic metabolizing enzymes have been implicated in inter-individual and inter-ethnic differences in cancer susceptibilty. Several studies have indicated an association between variant alleles of the human CYP1A1, CYP2E1 and GSTM1 genes and lung cancer. Activity of microsomal epoxide hydrolase (HYL1) has also been associated with lung cancer, and 2 variant alleles causing amino acid substitutions have been described. We have investigated genetic polymorphisms of the CYP1A1, CYP2E1, GSTM1 and HYL1 genes in 76 Chinese lung cancer patients and 122 healthy Chinese subjects. The allele frequency of the CYP1A1*2B allele was 0.21 among lung cancer patients and 0.20 in the reference group, whereas the corresponding values for the CYP1A1*2A allele were 0.34 and 0.36. The CYP2E1*5B and CYP2E1*6 alleles were less frequent among the cancer patients (0.20 and 0.22) compared with healthy subjects (0.25 and 0.26). The frequency distribution of the HYL1*2 allele was 0.49 among lung cancer patients and 0.42 in the reference group, and the corresponding frequencies for the HYL1*3 allele were 0.13 and 0.10. The homozygous GSTM1*0 genotype was found in 64% of lung cancer patients and in 66% of healthy subjects. Among heavy smokers, the frequency was 73%. The differences in the distribution of variant CYP1A1, CYP2E1 and GSTM1 alleles in lung cancer patients and healthy controls were not statistically significant. Our results indicate that the polymorphisms investigated are of minor importance as genetic susceptibility markers for lung cancer in this population. An increased risk for lung cancer in subjects carrying the HYL*3 allele was observed and suggests that polymorphism in this gene might possibly be a susceptibility factor in the Chinese population.     

Influence of GSTM1, GSTT1, GSTP1 and NAT2 genotypes on the p53 mutational spectrum in bladder tumours

Genetic polymorphisms affecting expression or activity of the corresponding enzymes can influence the risk of acquiring gene mutations and various cancers. We have studied 327 bladder cancer patients with regard to the functionally related polymorphisms of GSTM1, GSTT1, GSTP1 and NAT2 and analysed the p53 mutational status of their tumours. Fifty p53 mutations, 26% transversions and 74% transitions, were detected in 44 patients. P53 mutation frequency was significantly higher in higher-grade tumours than in low-grade tumours (OR = 2.09, 95% CI 1.44-3.02, adjusted for age and sex). Also, a significant association was found between tumour stage (Tis and T2+ vs. Ta and T1) and presence of the GSTP1 val allele (adjusted OR = 2.00, CI 1.14-3.52). Overall, there was no significant difference in frequency of p53 mutation among patients with different genotypes. Among patients with p53 mutation, transversions were significantly more frequent in GSTM1-negative as compared to GSTM1-positive individuals (OR = 5.18, CI 1.07-25.02, adjusted for age, sex and tumour stage). With one exception, all tumours with the most common type of transversion, G:C-C:G, occurred in GSTM1-negative patients. Among smokers, all transversions (3 of 3), but only 2 of 13 transitions, were found among carriers of the GSTP1 variant allele, and samples carrying at least 1 variant GSTP1 allele had more transitions at CpG sites than wild-type samples (adjusted OR = 4.61, CI 0.82-26.04). No significant associations were found for the NAT2 gene. Our results suggest that impaired glutathione conjugation may affect the mutation spectrum in critical target genes.     

CYP1A1, CYP2E1 and GSTM1 genetic polymorphisms. The effect of single and combined genotypes on lung cancer susceptibility in Chilean people.

CYP1A1, CYP2E1 and GSTM1 polymorphisms were evaluated in Chilean healthy controls and lung cancer patients. In the Chilean healthy group, frequencies of CYP1A1 variant alleles for MspI (m2 or CYP1A1*2A) and ile/val (val or CYP1A1*2B) polymorphisms were 0.25 and 0.33, respectively. Frequencies of variant alleles C (CYP2E1*6) and c2 (CYP2E1*5B) for CYP2E1 were 0.21 and 0.16, respectively and frequency for GSTM1(-) was 0.24. The presence of variant alleles for GSTM1, MspI and Ile/val polymorphisms was more frequent in cases than in controls. However, frequencies for the c2 and C alleles were not significantly different in controls and in cases. The estimated relative risk for lung cancer associated to a single mutated allele in CYP1A1, CYP2E1 or GSTM1 was 2.41 for m2, 1.69 for val, 1.16 for C, 0.71 for c2 and 2.46 for GSTM1(-). The estimated relative risk was higher for individuals carrying combined CYP1A1 and GSTM1 mutated alleles (m2/val, OR=6.28; m2/GSTM1(-), OR=3.56) and lower in individuals carrying CYP1A1 and CYP2E1 mutated alleles (m2/C, OR=1.39; m2/c2, OR=2.00; val/C, OR=1.45; val/c2, OR=0.48; not significant). The OR values considering smoking were 4.37 for m2, 4.05 for val, 3.47 for GSTM1(-), 7.38 for m2/val and 3.68 for m2/GSTM1(-), higher values than those observed without any stratification by smoking. Taken together, these findings suggest that Chilean people carrying single or combined GSTM1 and CYP1A1 polymorphisms could be more susceptible to lung cancer induced by environmental pollutants such as polycyclic aromatic hydrocarbons.     

Association of GSTM1, CYP1A1 and CYP2E1 genetic polymorphisms with susceptibility to lung adenocarcinoma: a case-control study in Chinese population

A case-control study of 164 lung adenocarcinoma (AC) patients with 181 age- and gender-matched healthy controls was conducted in order to assess any associations between glutathione- S -transferase M1 (GSTM1), cytochrome P4501A1 (CYP1A1) and cyto-chrome P4502E1 (CYP2E1) polymorphisms and susceptibility to lung AC in Chinese. The presence of CYP2E1 variant allele was significantly less frequent in cases than in controls, while the distribution of GSTM1 null genotype and variant CYP1A1 Msp 1 allele did not vary between cases and controls. After adjustment for age, gender, smoking and all other genotypes, the CYP2E1 Rsa1 variant allele was significantly associated with decreased risk of lung AC [odds ratio 0.534 (95% confidence interval, 0.340–0.837)]. Furthermore, 3.0-fold increased risk was found in individuals with combined GSTM1 null genotype and CYP2E1 Rsa 1 wild type versus those with combined GSTM1 non-null type and CYP2E1 variant allele. Our results suggest that CYP2E1 Rsa 1 variant allele is associated with a decreased risk of lung AC, and combined GSTM1 null genotype and CYP2E1 Rsa1 wild type has a promoting effect on susceptibility to lung AC. (Cancer Sci 2003; 94: 448–452)     

Oral cancer susceptibility associated with the CYP1A1 and GSTM1 genotypes in Chilean individuals

Polycyclic aromatic hydrocarbons (PAHs) contained in tobacco smoke acquire carcinogenicity following their activation by xenobiotic-metabolizing enzymes to highly reactive metabolites. The cytochrome P4501A1 (CYP1A1) enzyme is central to the metabolic activation of these PAHs, and GSTM1 is the main enzyme responsible for its detoxification. CYP1A1 and GSTM1 polymorphisms were evaluated in 124 Chilean healthy controls and 48 oral cancer patients through PCR-based restriction fragment length polymorphism. In the healthy controls, frequencies of the CYP1A1 variant alleles for m1 (CYP1A1(*)2A) and the GSTM1null genotype were found to be 0.25 and 0.19, respectively. In the oral cancer patients, these frequencies were 0.33 and 0.50, respectively. Thus, the GSTM1 and m1 rare alleles were significantly more frequent in the oral cancer patients compared to the controls. The estimated relative risk for oral cancer associated with the single genotype CYP1A1 or GSTM1 was 2.08 for wt/m1, 1.04 for m1/m1 and 4.16 for the GSTM1null genotype. For smokers, the estimated relative risk (adjusted by age and gender) was higher in the individuals carrying the m1 allele of CYP1A1 [wt/m1: odds ratio (OR)=5.68, P=0.0080; m1/m1: OR=7.77, P=0.0420] or GSTM1null genotype (OR=20.81, P<0.0001). Combined genotypes CYP1A1 and GSTM1 increased the risk significantly (wt/m1/GSTM1null: OR=19.14, P=0.0030; m1/m1/GSTM1null: OR=21.39, P=0.0130). Taken together, these findings suggest that Chilean individuals carrying single or combined GSTM1 and CYP1A1 polymorphisms may be more susceptible to oral cancer induced by environmental tobacco smoking.     

Modulation of benzo[a]pyrene diolepoxide-DNA adduct levels in human white blood cells by CYP1A1, GSTM1 and GSTT1 polymorphism

The modulation of benzo[a]pyrene diolepoxide (BPDE)-DNA adduct levels by polymorphisms in the CYP1A1, GSTM1 and GSTT1 genes was assessed in leukocytes of Caucasian males. Eighty-nine coke oven workers (35 smokers, 36 ex-smokers and 18 non-smokers) were recruited from job categories with different exposure levels to polycyclic aromatic hydrocarbons (PAH), together with 44 power plant workers (all smokers) not exposed to PAH. BPDE-DNA adducts were detected in 69 of 133 (52%) DNA samples with a 100-fold variation (range 0.2-44 adducts/10(8) nt) and a median of 1.6 adducts/10(8) nt. All samples with the GSTM1 active genotype (n = 59) and five out of 74 samples with GSTM1*0/*0 (7%) showed non-detectable adducts (<0.2 adducts/10(8) nt) and 69 of 74 subjects with GSTM1*0/*0 (93%) had detectable adducts (>0.2 adducts/10(8) nt). The difference in adduct level between the GSTM1*0/*0 and GSTM1 active genotypes was highly significant (P < 0.0001). No significant difference in adduct level between the GSTT1*0/*0 and GSTT1 active genotypes was seen. All heterozygotes (CYP1A1*1/*2) from subjects of GSTM1 active type did not have detectable adducts. Among the GSTM1-deficient individuals (n = 69), 42 with the CYP1A1*1/*1 genotype showed a lower adduct level (median 1.3, range 0.2-4.1 adducts/10(8) nt) compared with 26 individuals with heterozygous mutated CYP1A1*1/*2 genotypes (median 2.5, range 0.4-6.1 adducts/10(8) nt, P < 0.015). One individual with low PAH exposure and the rare combination CYP1A1*2A/*2A-GSTM1*0/*0 showed an extremely high level of 44 adducts/10(8) nt. Significant differences in detectable adduct levels were found between the CYP1A1*1/*1 and CYP1A1*1/*2 genotypes in the exposed group low + medium (P = 0.01) and for all adduct levels, detectable and non-detectable (set at a fixed value), in highly exposed individuals and in ex-smokers (P = 0.03), whereas no such differences were observed in the control group. Mutated CYP1A1*1/*2 increased the adduct level in non-smokers from the exposed group (1.4 versus 2.2 adducts/10(8) nt), but had no effect on the smokers from the exposed group (2.3 versus 2.8 adducts/10(8) nt). When all variables were dichotomized, statistical evaluation showed that CYP1A1 status (P = 0.015), PAH exposure (P = 0.003) and smoking (P = 0.006) had significant effects on adduct levels which increased in the order: CYP1A1*1/*1 < CYP1A1(*1/*2 or *2A/*2A); environmental exposure < occupational exposure; non-smokers < smokers, whereby adducts increased with cigarette dose and the duration of smoking. Higher levels of BPDE-DNA adducts in individuals with the combined CYP1A1(1/*2 or *2A/*2A)-GSTM1*0/*0 genotype suggest that these genotype combinations are at increased risk for contracting lung cancer when exposed to PAH.     

Influence of p53 codon 72 exon 4, GSTM1, GSTT1 and GSTP1*B polymorphisms in lung cancer risk in a Brazilian population

PURPOSE: Glutathione S-transferases (GST) modulates the effects of various cytotoxic and genotoxic agents, particularly those derived from benzo[a]pyrene, which is one of the main tobacco carcinogens. Both the mu 1 (GSTM1) and theta 1 (GSTT1) genes have a null variant allele in which the entire gene is absent. The GSTP1*B allele has an A to G transition at nucleotide 313 (codon 105) in exon 5, causing a change of isoleucine (Ile) to valine (Val), which affects the electrophile binding site of GSTP1 and results in an enzyme with reduced activity. Polymorphisms in these metabolizing enzymes may alter the response to benzo[a]pirene-induced DNA damage. Polymorphisms in p53 may also modulate the risk of lung cancer (LC) carcinogenesis. The aim of our study was to measure the frequency of GSTM1, GSTT1, GSTP1*B and p53 gene polymorphisms in a Brazilian population and determine the possible contribution of these genetic variations to LC risk. PATIENTS AND METHODS: Genomic DNA was obtained from 200 Brazilian patients with LC and 264 blood donors (control group). All samples were analyzed by PCR and PCR-RFLP to determine GSTM1, GSTT1, GSTP1*B and p53 codon 72 genotypes. Multiple logistic regressions were used to adjust for confounding factors in this case-control study. RESULTS: No statistical significance was observed between GSTM1, GSTT1 and GSTP1*B genetic polymorphisms, either isolated or combined, with LC incidence in the studied population. However, our data showed a higher frequency of p53 codon 72 A/P plus P/P genotype in African-Brazilian than Caucasian-Brazilian patients with LC, and we also found a higher frequency of the P/P genotype of the p53 gene in non-smokers compared to smokers with LC. CONCLUSIONS: Genetic polymorphisms of GST and p53 codon 72 did not increase the risk of LC in Brazilian patients. The A/P plus P/P genotype of p53 codon 72 is more common in LC patients with African ethnical background and the P/P genotype more prevalent in non-smoking related LC.     

Childhood leukaemia, polymorphisms of metabolism enzyme genes, and interactions with maternal tobacco, coffee and alcohol consumption during pregnancy.

Metabolic polymorphisms may influence the risk of childhood leukaemia related to maternal tobacco, coffee or alcohol consumption. The data were extracted from a case-control study including 280 cases of acute leukaemia and 288 controls. Blood sampling was obtained for a representative subset of 219 cases and 105 controls. Gene-environment interactions were estimated using both case-control and case-only analyses. The polymorphisms of CYP1A1, GSTM1, GSTP1, GSTT1 and NQO1 were not associated with the risk of leukaemia. The slow EPHX1 allele was negatively associated with childhood leukaemia while an inverse non-significant association was observed with the fast EPHX1 allele. Maternal smoking during pregnancy was not related to leukaemia, but an interaction was observed in the case-only analysis with CYP1A1*2A variant allele (odds ratio (OR) 2.2 [1.0-4.9]) and with GSTM1 deletion (OR 2.3 [1.2-4.4]). Conversely, coffee drinking interacted negatively with NQO1 polymorphism in the case-only analysis (OR 0.6 [0.3-1.2] and 0.4 [0.1-1.0] for light and heavy coffee consumptions, respectively). This study suggests that maternal smoking may be a risk factor for leukaemia in children who carry CYP1A1 or GSTM1 genotypes, which might increase reactive metabolites of polycyclic aromatic hydrocarbons.     

Effects of the ADH3, CYP2E1, and GSTP1 genetic polymorphisms on their expressions in Caucasian lung tissue

Individual differences in lung cancer susceptibility should be considered for effective lung cancer prevention. We investigated the CYP2E1, ADH3, and GSTP1 genetic polymorphisms that biotransform xenobiotic carcinogens, and variations of their enzyme activity in Caucasian lung tissues (N=28), and found a variant distribution in pulmonary ADH and CYP2E1 activity. The ADH3*1/*1 subjects (N=8) showed significantly higher ADH activity than ADH3*2/*2 (N=3) subjects (P<0.01). On the other hand, we found a 5-fold variation in the pulmonary CYP2E1 activity using a sensitive HLPC/EC based technique. A subject with the CYP2E1-c/t allele showed 2-fold higher CYP2E1 activity than subjects with the c/c allele (N=14). GSTP1 expression comprised 83% of the total pulmonary GSTs. However, neither the GSTP1 polymorphism, nor other lifestyle factors, such as age, gender, smoking status, were found to be associated with pulmonary GST expression. In conclusion, subjects with the ADH3*1 allele showed higher ADH activity and acetaldehyde-DNA adducts in lung than other subjects; thus, the ADH3*1 allele could be considered a risk factor for lung cancer.