Assessment of interactions between PAH exposure and genetic polymorphisms on PAH-DNA adducts in African American, Dominican, and Caucasian mothers and newborns.

Polycyclic aromatic hydrocarbons (PAH) are widespread pollutants commonly found in air, food, and drinking water. Benzo[a]pyrene is a well-studied representative PAH found in air from fossil fuel combustion and a transplacental carcinogen experimentally. PAHs bind covalently to DNA to form DNA adducts, an indicator of DNA damage, and an informative biomarker of potential cancer risk. Associations between PAH-DNA adduct levels and both cancer risk and developmental deficits have been seen in previous experimental and epidemiologic studies. Several genes have been shown to play an important role in the metabolic activation or detoxification of PAHs, including the cytochrome P450 genes CYP1A1 and CYP1B1 and the glutathione S-transferase (GST) genes GSTM1, and GSTT2. Genetic variation in these genes could influence susceptibility to adverse effects of PAHs in polluted air. Here, we have explored interactions between prenatal PAH exposure and 17 polymorphisms in these genes (rs2198843, rs1456432, rs4646903, rs4646421, rs2606345, rs7495708, rs2472299, rs162549, rs1056837, rs1056836, rs162560, rs10012, rs2617266, rs2719, rs1622002, rs140194, and gene deletion GSTM1-02) and haplotypes on PAH-DNA adducts in cord blood of 547 newborns and in maternal blood of 806 mothers from three different self-described ethnic groups: African Americans, Dominicans, and Caucasians. PAHs were measured by personal air monitoring of mothers during pregnancy. Significant interactions (p < 0.05) were observed between certain genetic polymorphisms and CYP1A1 haplotype and PAHs in mothers and their newborns in the three ethnic groups. However, with our limited sample size, the current findings are suggestive only, warranting further study.     

CYP1B1 variants are associated with prostate cancer in non-Hispanic and Hispanic Caucasians

Cytochrome P450 1B1 (CYP1B1) is involved in the activation of many carcinogens and in the metabolism of steroid hormones. We compared allele, genotype and haplotype frequencies of six single-nucleotide polymorphisms (SNPs) within CYP1B1 among non-Hispanic Caucasians (496 cases and 498 controls) and Hispanic Caucasians (153 cases and 240 controls). In the Hispanic Caucasians, the GG genotype for rs1056836 decreased the risk for prostate cancer (PCa) when compared with the CC genotype [odds ratio (OR) = 0.31, P = 0.04, 95% confidence interval (CI) = 0.10-0.96]. Among non-Hispanic Caucasian men with more aggressive PCa, the prevalence of several SNPs (rs2567206, rs2551188, rs2617266, rs10012 and rs1056836) was significantly associated with the disease status. A common C-G-C-C-G-A haplotype for rs2567206-rs2551188-rs2617266-rs10012-rs1056836-rs1800440 showed an inverse association with PCa risk in Hispanic Caucasians (OR = 0.19, P = 0.04, 95% CI = 0.04-0.95) and with aggressive disease status (i.e. Gleason score >or=7) in non-Hispanic Caucasian cases (OR = 0.64, P = 0.008, 95% CI = 0.47-0.89). In the non-Hispanic Caucasian cases, a second major haplotype T-A-T-G-C-A was positively associated with the high-grade disease status (OR = 1.77, P = 0.002, 95% CI = 1.24-2.53). Our findings suggest that genetic polymorphisms in CYP1B1 may modify the risk for PCa and support the role of CYP1B1 as a candidate gene for PCa.     

Estimating exposure to polycyclic aromatic hydrocarbons: a comparison of survey, biological monitoring, and geographic information system-based methods.

Our objective was to compare polycyclic aromatic hydrocarbon (PAH) exposure estimates based on survey, biological monitoring, and geographic information system (GIS) methods. The 304 participants in this study supplied a urine sample and completed questionnaires about exposure to potential PAH sources. We assayed urine samples for 1-hydroxypyrene-O-glucuronide (1-OHPG), the major metabolite of pyrene, a common PAH. We used a GIS to estimate traffic exhaust exposure using vehicle count data at the residence and workplace. The five subjects who reported smoking during the 48-hour period had median 1-OHPG concentrations 10-fold that of nonsmokers (1.6 versus 0.16 pmol/mL; P = 0.01). Among nonsmokers, those who reported eating grilled, roasted, or broiled meat had significantly higher 1-OHPG concentrations than those who did not reported eating meat prepared by these methods (0.25 versus 0.06 pmol/mL; P = 0.02). Nonsmokers who reported traveling on roads for > or =3 hours during the 48-hour period also had significantly higher 1-OHPG levels than those who traveled <3 hours (0.23 versus 0.11 pmol/mL; P = 0.03). 1-OHPG levels were also correlated with hours of secondhand smoke exposure among nonsmokers (P = 0.04). In this study, 1-OHPG urine concentrations were not associated with self-reported exposures to cooking smoke, wood burning, or traffic levels near the home or to traffic density or urban/rural status determined using a GIS. Self-reported indicators of residential proximity to high traffic volume were, however, associated with GIS traffic density measures.     

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.     

Interactions between CYP1A1 polymorphisms and exposure to environmental tobacco smoke in the modulation of lymphocyte bulky DNA adducts and chromosomal aberrations

CYP1A1 plays an important role in the metabolic activation of polycyclic aromatic hydrocarbons (PAH), carcinogenic components of air pollution. The influence of CYP1A1 genotype (*2A, *2B and *4) on the levels of lymphocyte bulky DNA adducts and the frequency of cells with aberrant chromosomes was assessed in 194 non-smoking subjects in whom recent exposure to environmental tobacco smoke (ETS) and airborne particulate-associated PAH were measured during two consecutive seasons (winter and summer). While CYP1A1*4 had no consistent effect on either biomarker of genetic damage, the levels of both biomarkers responded in a parallel fashion to changes in exposure/CYP1A1*2A genotype combinations during both seasons. Specifically, the levels of both biomarkers were increased in carriers of at least one CYP1A1*2A allele, as compared with CYP1A1*1 homozygotes, in subjects with ETS exposures >0.8 h/day during the previous 4 days and mean personal exposure to benzo[a]pyrene <0.9 ng/m3 during the previous 24 h (all P < 0.05). Outside these exposure limits the differential effect in CYP1A1*2A variants was lost. Although the numbers of subjects with the CYP1A1*2B polymorphism was small, the same trend appeared to be followed in this case. These effects are interpreted as resulting from differential induction of CYP1A1 expression in CYP1A1*2A and CYP1A1*2A/*2B carriers by components of ETS-polluted air at levels of exposure readily suffered by large segments of the general population and suggest that subjects with these genotypes may have increased susceptibility to the genotoxic effects of ETS.     

Association of CYP1B1 codon 432 mutant allele in head and neck squamous cell cancer is reflected by somatic mutations of p53 in tumor tissue

Tobacco use is causally associated with head and neck squamous cell cancer (HNSCC). Here, we present the results of a case-control study that investigated the effects that the genetic variants of the cytochrome (CYP)1A1, CYP1B1, glutathione-S-transferase (GST)M1, GSTT1, and GSTP1 genes have on modifying the risk of smoking-related HNSCC. Allelisms of the CYP1A1, GSTT1, GSTM1, and GSTT1 genes alone were not associated with an increased risk. CYP1B1 codon 432 polymorphism was found to be a putative susceptibility factor in smoking-related HNSCC. The frequency of CYP1B1 polymorphism was significantly higher (P < 0.001) in the group of smoking cases when compared with smoking controls. Additionally, an odds ratio (OR) of 4.53 (2.62-7.98) was discovered when investigating smoking and nonsmoking cases for the susceptible genotype CYP1B1*2/*2, when compared with the presence of the genotype wild type. In combination with polymorphic variants of the GST genes, a synergistic-effect OR was observed. The calculated OR for the combined genotype CYP1B1*2/*2 and GSTM1*2/*2 was 12.8 (4.09-49.7). The calculated OR for the combined genotype was 13.4 (2.92-97.7) for CYP1B1*2/*2 and GSTT1*2/*2, and 24.1 (9.36-70.5) for the combination of CYP1B1*2/*2 and GSTT1-expressors. The impact of the polymorphic variants of the CYP1B1 gene on HNSCC risk is reflected by the strong association with the frequency of somatic mutations of the p53 gene. Smokers with susceptible genotype CYP1B1*2/*2 were 20 times more likely to show evidence of p53 mutations than were those with CYP1B1 wild type. Combined genotype analysis of CYP1B1 and GSTM1 or GSTT1 revealed interactive effects on the occurrence of p53 gene mutations. The results of the present study indicate that polymorphic variants of CYP1B1 relate significantly to the individual susceptibility of smokers to HNSCC.     

Impact of AhR,CYP1A1 and GSTM1 Genetic Polymorphisms on TP53 R273G Mutations in Individuals Exposed to Polycyclic Aromatic Hydrocarbons

This study was to undertaken to investigate the impacts of AhR, CYP1A1, GSTM1 genetic polymorphisms onthe R273G mutation in exon 8 of the tumor suppressor p53 gene (TP53) among polycyclic aromatic hydrocarbons(PAHs) exposed to coke-oven workers. One hundred thirteen workers exposed to PAH and 82 control workerswere recruited. We genotyped for polymorphisms in the AhR, CYP1A1, GSTM1, and TP53 R273G mutation inblood by PCR methods, and determined the levels of 1-hydroxypyrene as PAH exposure marker in urine usingthe high pressure liquid chromatography assay. We found that the distribution of alcohol users and the urinaryexcretion of 1-OHP in the exposed workers were significantly higher than that of the control workers (p=0.004,p<0.001, respectively). Significant differences were observed in the p53 genotype distributions of smokingsubjects (p=0.01, 95%CI: 1.23-6.01) and PAH exposure (p=0.008, 95%CI: 1.24-4.48), respectively. Further,significant differences were observed in the p53 exon 8 mutations for the genetic polymorphisms of Lys/Argfor AhR (p=0.02, 95%CI: 0.70-15.86), Val/Val for CYP1A1 (p=0.04, 95%CI: 0.98-19.09) and null for GSTM1(p=0.02, 95%CI: 1.19-6.26), respectively. Our findings indicated that polymorphisms of PAH metabolic genes,such as AhR, CYP1A1, GSTM1 polymorphisms may interact with p53 genetic variants and may contribute toPAH related cancers.     

CYP2W1, CYP4F11 and CYP8A1 polymorphisms and interaction of CYP2W1 genotypes with risk factors in Mexican women with breast cancer

Breast cancer (BCa) is the leading type of cancer in Mexican women. Genetic factors, such as single nucleotide polymorphisms (SNP) of P450 system, have been reported in BCa. In this report, and for the first time in the literature, we analyzed the rs3735684 (7021 G>A), rs11553651 (15016 G>T) and rs56195291 (60020 C>G) polymorphisms in the CYP2W1, 4F11 and 8A1 genes in patients with BCa and in healthy Mexican women to identify a potential association between these polymorphisms and BCa risk. Patients and controls were used for polymorphism analysis using an allelic discrimination assay with TaqMan probes and confirmed by DNA sequencing. Links with clinic-pathological characteristics were also analyzed. Statistical analysis was performed using the standard χ2 or Fisher exact test statistic. No significant differences were observed in the distributions of CYP2W1 (OR 8.6, 95%CI 0.43-172.5 P>0.05; OR 2.0, 95%CI 0.76-5.4, P>0.05) and CYP4F11 (OR 0.3, 95%CI 0.01-8.4 P>0.05) genotypes between the patients and controls. Only the CYP8A1 CC genotype was detected in patients with BCa and the controls. All polymorphism frequencies were in Hardy-Weinberg Equilibrium (HWE) in the controls (P>0.05). We found a significant association between BCa risk and smoking, use of oral contraceptives or hormonal replacement therapy (HRT), obesity, hyperglycemia, chronic diseases, family history of cancer and menopausal status in the population studied (P<0.05). Tobacco, oral contraceptive or HRT, chronic diseases and obesity or overweight were strongly associated with almost eight, thirty-five, nine and five-fold increased risk for BCa. Tobaco, obesity and hyperglycemia significantly increased the risk of BCa in the patients carrying variant genotypes of CYP2W1 (P<0.05). These results indicate that the CYP2W1 rs3735684, CYP4F11 rs11553651 and CYP8A1 rs56195291 SNPs are not a key risk factor for BCa in Mexican women. This study did not detect an association between the CYP2W1, 4F11 and 8A1 genes polymorphisms and BCa risk in a Mexican population. However, some clinico-pathological risk factors interact with CYP2W1 genotypes and modifies susceptibility to BCa.     

CYP1A1 Gene Polymorphisms: Modulator of Genetic Damage in Coal-Tar Workers

Aim: It is well known that polycyclic aromatic hydrocarbons (PAHs) such as benzo (a) pyrene have carcinogenicproperties and may cause many types of cancers in human populations. Genetic susceptibility might be due tovariation in genes encoding for carcinogen metabolizing enzymes, such as cytochrome P-450 (CYP450). Our studyaimed to investigate the effect of genetic polymorphisms of CYP1A1 (m1 and m2) on genetic damage in 115 coaltarworkers exposed to PAHs at their work place. Methods: Genetic polymorphisms of CYP1A1 were determinedby the PCR-RFLP method. Comet and buccal micronucleus assays were used to evaluate genetic damageamong 115 coal tar workers and 105 control subjects. Results: Both CYP1A1 m1 and CYP1A1 m2 heterozygousand homozygous (wt/mt+mt/mt) variants individually as well as synergistically showed significant association(P<0.05) with genetic damage as measured by tail moment (TM) and buccal micronuclei (BMN) frequencies incontrol and exposed subjects. Conclusion: In our study we found significant association of CYP1A1 m1 and m2heterozygous (wt/mt)+homozygous (mt/mt) variants with genetic damage suggesting that these polymorphismsmay modulate the effects of PAH exposure in occupational settings.     

A variant in CYP26B1 associated with esophageal squamous cell carcinoma risk by affecting retinoic acid metabolism

All-trans retinoic acid (ATRA) is the natural and synthetic analogue of vitamin A, playing an essential tumor suppressive role in multiple cancers including the esophageal squamous cell carcinoma (ESCC). Cytochrome P450 family 26 subfamily B member 1 (CYP26B1) exerts a critical regulator of ATRA levels through specific inactivation of ATRA to hydroxylated forms. Our previous exome-wide analyses revealed a rare missense variant in CYP26B1 significantly associated with ESCC risk in the Chinese population. However, it is still unclear whether there are common variants in CYP26B1 affect the susceptibility of ESCC and the tumor promotion role of CYP26B1 in vivo. In this research, we conducted a two-stage case-control study comprised of 5057 ESCC cases and 5397 controls, followed by a series of biochemical experiments to explore the function of CYP26B1 and its common variants in the tumorigenesis of ESCC. Intriguingly, we identified a missense variant rs2241057[A>G] in the fourth exon of CYP26B1 significantly associated with the ESCC risk (combined odds ratio = 1.28; 95% confidence interval = 1.15–1.42; p = 2.96 × 10⁻⁶). Through further functional analysis, we demonstrated that ESCC cells with the overexpression of rs2241057[G] had a significant lower level of retinoic acid, compared with the overexpression of rs2241057[A] or the control vector. In addition, the CYP26B1 overexpression and knock-out ESCC cells affected cell proliferation rate both in vitro and in vivo. These results highlighted the carcinogenicity of CYP26B1 related to the ATRA metabolism in ESCC risk.     

Comprehensive association analysis of the vitamin D pathway genes, VDR, CYP27B1, and CYP24A1, in prostate cancer.

Genetic variation in vitamin D-related genes has not been investigated comprehensively and findings are equivocal. We studied the association between polymorphisms across the entire vitamin D receptor (VDR) gene and genes encoding for vitamin D activating enzyme 1-alpha-hydroxylase (CYP27B1) and deactivating enzyme 24-hyroxylase (CYP24A1) and prostate cancer risk among middle-aged men using a population-based case-control study design. DNA samples and survey data were obtained from incident cases (n = 630), 40 to 64 years old, identified through the Seattle-Puget Sound Surveillance, Epidemiology, and End Results cancer registry from 1993 to 1996 and from random controls (n = 565) of similar age without a history of prostate cancer. We selected and genotyped tag single-nucleotide polymorphisms to predict common variants across VDR (n = 22), CYP27B1 (n = 2), and CYP24A1 (n = 14). Haplotypes of VDR and CYP24A1 were not associated with prostate cancer risk. In the genotype analysis, homozygotes at two VDR loci (rs2107301 and rs2238135) were associated with a 2- to 2.5-fold higher risk of prostate cancer compared with the homozygote common allele [odds ratio, 2.47 (95% confidence interval, 1.52-4.00; P = 0.002) and 1.95 (95% confidence interval, 1.17-3.26; P = 0.007), respectively; P value corrected for multiple comparisons for VDR = 0.002]. We found no evidence that the two associated VDR single-nucleotide polymorphisms were modified by age at diagnosis, prostate cancer aggressiveness, first-degree family history of prostate cancer, or vitamin D intake. Genotypes of CYP27B1 and CYP24A1 were not associated with prostate cancer risk. Our findings suggest that polymorphisms in the VDR gene may be associated with prostate cancer risk and, therefore, that the vitamin D pathway might have an etiologic role in the development of prostate cancer.     

Competitive inhibition of carcinogen-activating CYP1A1 and CYP1B1 enzymes by a standardized complex mixture of PAH extracted from coal tar

A complex mixture of polycyclic aromatic hydrocarbons (PAH) extracted from coal tar, the Standard Reference Material (SRM) 1597, was recently shown to decrease the levels of DNA binding of the 2 strong carcinogens benzo[a]pyrene (BP) and dibenzo[a,l]pyrene (DBP) in the human mammary carcinoma-derived cell line MCF-7 (Mahadevan et al., Chem Res Toxicol 2005;18:224-231). The present study was designed to further elucidate the biochemical mechanisms involved in this inhibition process. We examined the effects of SRM 1597 on the metabolic activation of BP and DBP toward DNA-binding derivatives in Chinese hamster cells expressing either human cytochrome P450 (CYP) 1A1 or CYP1B1. SRM 1597 inhibited BP-DNA adduct formation through the entire exposure time in cells expressing human CYP1A1, while it significantly inhibited adduct formation only up to 48 hr when co-treated with DBP. Conversely, human CYP1B1-expressing cells were unable to catalyze PAH-DNA adduct formation on treatment with SRM 1597 alone, and on co-treatment with BP or DBP. The data obtained from biochemical experiments revealed that SRM 1597 competitively inhibited the activity of both human enzymes as analyzed by 7-ethoxyresorufin O-deethylation assays. While the Michaelis-Menten constant (K(M)) was <0.4 microM in the absence of SRM 1597, this value increased up to 1.12 (CYP1A1) or 4.45 microM (CYP1B1) in the presence of 0.1 microg/ml SRM 1597. Hence the inhibitory effects of the complex mixture on human CYP1B1 were much stronger when compared to human CYP1A1. Taken together, the decreases in PAH-DNA adduct formation on co-treatment with SRM 1597 revealed inhibitory effects on the CYP enzymes that convert carcinogenic PAH into DNA-binding metabolites. The implications for the tumorigenicity of complex environmental PAH mixtures are discussed.     

CYP2C9、GSTM1基因多态性与肺癌易感性的关系

目的探讨细胞色素P4502C9(CYP2C9)基因、谷胱甘肽硫转移酶M1(GST M1)基因多态性与肺癌易感性的关系。方法用PCR-RFLP法分析56例肺癌(简称肺癌组)和42例健康对照组NsiⅠ识别的CYP2C9基因型;用PCR法分析其GST M1基因型。结果突变型CYP2C9*3型基因发生频率在肺癌组中为8.93%,高于对照组的4.76%,其差异无显著性(P>0.05)。肺癌组GST M1基因缺失型〔GST M1(-)〕发生率为71.43%,高于对照组的45.24%,其差异有显著性(P<0.01);GST M1(-)型与肺癌呈高度联系强度,OR=3.09(95%CI=1.32~6.94);GST(-)基因型在吸烟的肺癌组(81.08%)与对照组(52.18%)之间的频率差异有显著性(P<0.05)。结论突变型CYP2C9*3型基因与肺癌无显著性联系;GST M1(-)基因型是肺癌发生的遗传易患性因素;吸烟可显著提高GST(-)基因型个体患肺癌的危险性。     

CYP19A1基因多态性与晚期乳腺癌阿那曲唑治疗疗效相关性研究

[目的]研究CYP1 9A 1基因的rs4646和rs 10046位点多态性与晚期乳腺癌阿那曲唑治疗疗效的相关性.[方法]本研究共纳入272例激素受体阳性晚期乳腺癌患者,接受阿那曲唑治疗后抽取患者外周静脉血,提取DNA,多重PCR获取目的基因片段后,采用直接测序法分析CYP19A1基因多态性.对比等位基因分布频率在突变型和野生型两组患者中的差异.[结果]被检测的rs4646和rs 10046符合Hardy-Weinberg平衡检验;比较rs4646突变型和野生型两组阿那曲唑疗效,32例完全缓解的患者中24例是rs4646突变型,76例疾病进展者中有60例是rs4646野生型,P＜0.005,经过Bonferroni矫正P值仍有统计学意义.与rS4646野生型相比,携带rs4646突变型患者的中位生存期(median survival time,MST)显著延长(Log-rank检验P=0.007).携带rs4646突变型患者的疾病进展时间(time to progression,TTP)显著延长(Log-rank检验P=0.049).[结论]rs4646多态性位点可能会成为预测晚期乳腺癌阿那曲唑治疗疗效和预后的预测因子.     

GST, NAT, SULT1A1, CYP1B1 genetic polymorphisms, interactions with environmental exposures and bladder cancer risk in a high-risk population

Tobacco smoking and occupation are major risk factors of bladder cancer via exposure to polycyclic aromatic hydrocarbons (PAHs) and aromatic amines. Glutathione S-transferase (GST) M1, T1 and P1 are involved in the detoxification of PAH reactive metabolites. Two N-acetyltransferase isozymes, NAT2 and NAT1, have major roles in catalyzing the N-acetylation and O-acetylation of aromatic amines. Cytochrome p450 1B1 (CYP1B1) and sulfotransferase 1A1 (SULT1A1) are also involved in the metabolism of PAHs and aromatic amines. It is hypothesized that the genetic polymorphisms of these metabolic enzymes have an effect on the individual susceptibility to bladder cancer in particular by interacting with relevant environmental exposures. A hospital-based case-control study among men in Brescia, Northern Italy recruited 201 incidence cases and 214 controls from 1997-2000. Occupational exposures were blindly coded by occupational physicians. Genotyping of polymorphisms were carried out with PCR-RFLP method. Unconditional multivariate logistic regression was applied to model the association between genetic polymorphisms and bladder cancer risk. Effect modifications by age of onset, smoking and occupational exposures to PAHs and aromatic amines were evaluated. We also conducted an analysis of interaction between genetic factors. GSTM1 and GSTT1 null genotype were associated with an increased risk of bladder cancer with an odds ratio (OR) of 1.69 (95% confidence interval [CI] = 1.11-2.56) and 1.74 (95% CI = 1.02-2.95), respectively. The effect of GSTM1 null was seen particularly in heavy smokers, and there was a combined effect with occupational exposure of aromatic amines (OR = 2.77, 95% CI = 1.08-7.10). We observed a trend (p-value < 0.01) of increasing cancer risk comparing subjects with normal GSTM1 and T1 activity to subjects with one (OR = 1.82, 95% CI = 1.16-2.85) or both null genotypes (OR = 2.58, 95% CI = 1.27-5.23). NAT2 slow acetylator was associated with marginally increased risk of bladder cancer (OR = 1.50, 95% CI = 0.99-2.27), and the OR for the joint effect with occupational exposure of aromatic amines was 3.26 (95% CI = 1.06-9.95). SULT1A1 Arg213His polymorphism showed a marginal protective effect. These findings suggest that individual susceptibility to bladder cancer may be modulated by GSTM1, GSTT1 and NAT2 polymorphisms.     

CYP1A1 (Ile462Val), CYP1B1 (Ala119Ser and Val432Leu), GSTM1 (null), and GSTT1 (null) Polymorphisms and Bladder Cancer Risk in a Turkish Population

We aimed to investigate bladder cancer risk with reference to polymorphic variants of cytochrome p450 (CYP)1A1, CYP1B1, glutathione S-transferase (GST) M1, and GSTT1 genes in a case control study. Polymorphismswere examined in 114 bladder cancer patients and 114 age and sex-matched cancer-free subjects. Genotypes weredetermined using allele specific PCR for CYP1A1 and CYP1B1 genes, and by multiplex PCR and melting curveanalysis for GSTM1 and GSTT1 genes. Our results revealed a statistically significant increased bladder cancerrisk for GSTT1 null genotype carriers with an odds ratio of 3.06 (95% confidence interval=1.39-6.74, p=0.006).Differences of CYP1A1, CYP1B1 and GSTM1 genotype frequencies were not statistically significant betweenpatients and controls. However, the specific combination of GSTM1 null, GSTT1 null, and CYP1B1 codon 119risk allele carriers and specific combination of GSTM1 present, GSTT1 null, and CYP1B1 432 risk allele carriersexhibited increased cancer risk in the combined analysis. We did not observe any association between differentgenotype groups and prognostic tumor characteristics of bladder cancer. Our results indicate that inheritedabsence of GSTT1 gene may be associated with bladder cancer susceptibility, and specific combinations ofGSTM1, GSTT1 and CYP1B1 gene polymorphisms may modify bladder cancer risk in the Turkish population,without any association being observed for CYP1A1 gene polymorphism and bladder cancer risk.     

Differential metabolism of benzo[a]pyrene and benzo[a]pyrene-7,8-dihydrodiol by human CYP1A1 variants

Cytochrome P450 1A1 (CYP1A1) plays a key role in the metabolism of carcinogens, such as benzo[a]pyrene (B[a]P) and metabolites to ultimate carcinogens. Three human allelic variants, namely wild-type (CYP1A1.1), CYP1A1.2 (I462V) and CYP1A1.4 (T461N), were coexpressed by coinfection of baculovirus-infected insect cells with human NADPH-P450 reductase. These recombinant enzymes (in microsomal membranes) were used to analyze whether CYP1A1 polymorphisms affect catalytic activities towards B[a]P and B[a]P-7,8-dihydrodiol. The complete spectrum of phase I metabolites, including the tetrahydrotetrols resulting from hydrolysis of the ultimate carcinogen, B[a]P-7,8-dihydrodiol-9,10-epoxide, was examined by HPLC. Wild-type enzyme showed the highest total metabolism of B[a]P, CYP1A1.2 was approximately 50%, and CYP1A1.4 approximately 70%. Km values for all metabolites with CYP1A1.2 were generally significantly lower than with wild-type enzyme (e.g. B[a]P-7,8-diol formation: 13.8 microM for wild-type, 3.5 microM for CYP1A1.2 and 7.7 microM for CYP1A1.4). Addition of epoxide hydrolase markedly increases the relative diol-to-phenol activities by all three variants. However, CYP1A1.4 exhibits the greatest efficiency to produce diol species. Each variant produced the diol epoxides from B[a]P-7,8-dihydrodiol. CYP1A1.1 exhibited with 10.4 pmol/min/pmol CYP1A1 the greatest total rate for 7,8-diol metabolites followed by CYP1A1.2 (7.2 pmol/min/pmol CYP1A1) and CYP1A1.4 (5.5 pmol/min/pmol CYP1A1). All enzyme variants produced about three times more diol epoxide 2-derived metabolites than diol epoxide 1-derived ones, whereby both rare allelic variants exhibited statistically significantly increased formation of diol epoxide 2. This study showed that the three CYP1A1 variants had different enzyme kinetics properties to produce both the diol metabolites from B[a]P and the ultimate mutagenic species diol epoxide 2 from B[a]P-7,8-dihydrodiol, which must be considered in the evaluation of individual susceptibility to cancer.     

CYP1B1, CYP1A1, MPO, and GSTP1 polymorphisms and lung cancer risk in never-smoking Korean women

Polymorphisms in metabolic genes encoding phase I and phase II enzymes are thought to modulate the risk of lung cancer via changes in enzymatic activity. Recently, the effect of these metabolic enzymes and their interaction with environmental factors has been studied in both smokers and also never-smokers, since never-smokers are a good model in which to study genetic susceptibility at low-dose carcinogen exposure. Here, we investigated the association of CYP1A1 Ile462Val, CYP1B1 Leu432Val, GSTP1 Ile105Val, MPO G-463A polymorphisms and lung cancer risk in never-smoking Korean women. In this case-control study of 213 lung cancer patients and 213 age-matched healthy controls, we found that carrying one variant allele of the CYP1A1 Ile462Val polymorphism was associated with a significantly decreased risk of lung adenocarcinoma (adjusted odds ratio (OR)=0.63; 95% confidence interval (CI), 0.41-0.99). Furthermore, the combination of risk genotypes of CYP1B1 Leu432Val with CYP1A1 Ile462Val was associated with the risk of lung adenocarcinoma (adjusted OR=2.16; 95% CI, 1.02-4.57) as well as overall lung cancer (adjusted OR=2.23; 95% CI 1.01-4.89). The polymorphisms of GSTP1 Ile105Val and MPO G-463A showed no significant association with lung cancer. Theses results suggest that the CYP1A1 Ile462Val polymorphism is associated with a reduced risk of lung adenocarcinoma in never-smoking Korean women, whereas specific combinations of variant genotypes for metabolic enzymes increase lung cancer risk considerably.