[Show abstract][Hide abstract] ABSTRACT: Genetically determined factors that alter the metabolism of tobacco carcinogens can influence an individual’s susceptibility
to bladder cancer. The associations between the genotypes of glutathione S-transferase (GST) M1, GSTP1, GSTT1 and N-acetyltransferase (NAT) 1 and the phenotypes of NAT2 and cytochrome P450 (CYP) 1A2 and bladder cancer risk were examined in a case–control study involving
731 bladder cancer patients and 740 control subjects in Los Angeles County, California. Individual null/low-activity genotypes
of GSTM1, GSTT1 and GSTP1 were associated with a 19–48% increase in odds ratio (OR) of bladder cancer. The strongest association was noted for GSTM1 [OR for the null genotype = 1.48, 95% confidence interval (CI) = 1.19–1.83]. When the three GST genes were examined together, there was a monotonic, statistically significant association between increasing number of null/low-activity
genotypes and risk (P for trend = 0.002). OR (95% CI) for one and two or more null/low-activity GST genotypes was 1.42 (1.12–1.81) and 1.71 (1.25–2.34), respectively, relative to the absence of null/low-activity GST genotype. NAT2 slow acetylation was associated with doubled risk of bladder cancer among individuals with known high exposures
to carcinogenic arylamines (OR = 2.03, 95% CI = 1.12–3.69, P = 0.02). The effect of NAT2 slow acetylation was even stronger in the presence of two or more null/low-activity GST genotypes. There were no associations between bladder cancer risk and NAT1 genotype or CYP1A2 phenotype.
[Show abstract][Hide abstract] ABSTRACT: Discovery and functional evaluation of biologically significant regulatory single nucleotide polymorphisms (SNP) in carcinogen metabolism genes is a difficult challenge because the phenotypic consequences may be both transient and subtle. We have used a gene expression screening approach to identify a functional regulatory SNP in glutathione S-transferase M3 (GSTM3). Anttila et al. proposed that variation in GSTM3 expression was affected by exposure to cigarette smoke and inheritance of the GSTM1-null genotype. To investigate the mechanism of GSTM3 expression was affected by exposure to cigarette smoke and inheritance of the GSTM1-null genotype. To investigate the mechanism of GSTM3 expression variation, we measured GSTM3 expression in lymphoblast cells from a human Centre d'Etude du Polymorphisme Humain family and observed a low expression phenotype. Promoter sequencing revealed two novel GSTM3 promoter SNPs: A/C and A/G SNPs, 63 and 783 bp upstream of the codon 1 start site, respectively. In this pedigree, the two children homozygous for the -63C/C genotype had 8-fold lower GSTM3 expression relative to the two children with the -63A/A genotype, with no association between A-783G SNP and GSTM3 expression. Further evaluation using genotyped glioma cell lines and with luciferase reporter constructs showed that the -63C allele was associated with lower GSTM3 expression (P < 0.0001 and P < 0.003). RNA pol II chromatin immunoprecipitation was combined with quantitative probed-based allelic discrimination genotyping to provide direct evidence of a 9-fold reduced RNA pol II binding capacity for the -63C allele. These results show that the GSTM3 -63C allele strongly affects gene expression in human cell lines and suggests that individuals who carry the low expression allele may be deficient in glutathione transferase catalyzed biological functions.
[Show abstract][Hide abstract] ABSTRACT: Previous epidemiological studies of fruit and vegetable intake and bladder cancer risk have yielded inconsistent results, especially with respect to the role of cigarette smoking as a possible modifier of the diet-bladder cancer association. A population-based case-control study was conducted in nonAsians of Los Angeles, California, which included 1,592 bladder cancer patients and an equal number of neighborhood controls matched to the index cases by sex, date of birth (within 5 years) and race between January 1, 1987 and April 30, 1996. Information on smoking, medical and medication history, and intake frequencies of food groups rich in preformed nitrosamines, vitamins A and C and various carotenoids, were collected through in-person, structured interviews. Beginning in January 1992, all case patients and their matched control subjects were asked for a blood sample donation at the end of the in-person interviews for measurements of 3- and 4-aminobiphenyl (ABP) hemoglobin adducts, and glutathione S-transferases M1/T1/P1 (GSTM1/T1/P1) and N-acetyltransferase-1 (NAT1) genotypes. Seven hundred seventy-one (74%) case patients and 775 (79%) control subjects consented to the blood donation requests. In addition, all case patients and matched control subjects were asked to donate an overnight urine specimen following caffeine consumption for measurements of cytochrome P4501A2 (CYP1A2) and N-acetyltransferase-2 (NAT2) phenotypes. Urine specimens were collected from 724 (69%) case patients and 689 (70%) control subjects. After adjustment for nondietary risk factors including cigarette smoking, there were strong inverse associations between bladder cancer risk and intake of dark-green vegetables [p value for linear trend (p) = 0.01], yellow-orange vegetables (p = 0.01), citrus fruits/juices (p = 0.002) and tomato products (p = 0.03). In terms of nutrients, bladder cancer risk was inversely associated with intake of both total carotenoids (p = 0.004) and vitamin C (p = 0.02). There was a close correlation (r = 0.58, p = 0.0001) between intakes of total carotenoids and vitamin C in study subjects. When both nutrients were included in a multivariate logistic regression model, only total carotenoids exhibited a residual effect that was of borderline statistical significance (p = 0.07 and p = 0.40 for total carotenoids and vitamin C, respectively). Cigarette smoking was a strong modifier of the observed dietary effects; these protective effects were confined largely to ever smokers and were stronger in current than ex-smokers. Smokers showed a statistically significant or borderline statistically significant decrease in 3- and 4-aminobiphenyl (ABP)-hemoglobin adduct level with increasing intake of carotenoids (p = 0.04 and 0.05, respectively). The protective effect of carotenoids on bladder cancer seemed to be influenced by NAT1 genotype, NAT2 phenotype and CYP1A2 phenotype; the association was mainly confined to subjects possessing the putative NAT1-rapid, NAT2-rapid and CYP1A2-rapid genotype/phenotype. The carotenoid-bladder cancer association was not affected by the GSTM1, GSTT1 and GSTP1 genotypes.
Full-text · Article · Jun 2004 · International Journal of Cancer
[Show abstract][Hide abstract] ABSTRACT: Meat cooked at high temperatures contains potential carcinogenic compounds, such as heterocyclic amines (HCAs) and polycyclic aromatic hydrocarbons (PAHs). Samples from a 2-week controlled feeding study were used to examine the relationship between the intake of mutagenicity from meat fried at different temperatures and the levels of mutagenicity subsequently detected in urine, as well as the influence of the genotype of drug metabolizing enzymes on urinary mutagenicity. Sixty subjects consumed ground beef patties fried at low temperature (100 degrees C) for 1 week, followed by ground beef patties fried at high temperature (250 degrees C) the second week. Mutagenicity in the meat was assayed in Salmonella typhimurium TA98 (+S9), and urinary mutagenicity was determined using Salmonella YG1024 (+S9). Genotypes for NAT1, NAT2, GSTM1, and UGT1A1 were analyzed using blood samples from the subjects. Meat fried at 100 degrees C was not mutagenic, whereas meat fried at 250 degrees C was mutagenic (1023 rev/g). Unhydrolyzed and hydrolyzed urine samples were 22x and 131x more mutagenic, respectively, when subjects consumed red meat fried at 250 degrees C compared with red meat fried at 100 degrees C. We found that hydrolyzed urine was approximately 8x more mutagenic than unhydrolyzed urine, likely due to the deconjugation of mutagens from glucuronide. The intake of meat cooked at high temperature correlated with the mutagenicity of unhydrolyzed urine (r = 0.32, P = 0.01) and hydrolyzed urine (r = 0.34, P = 0.008). Mutagenicity in unhydrolyzed urine was not influenced by NAT1, NAT2, or GSTM1 genotypes. However, a UGT1A1*28 polymorphism that reduced UGT1A1 expression and conjugation modified the effect of intake of meat cooked at high temperature on mutagenicity of unhydrolyzed urine (P for interaction = 0.04). These mutagenicity data were also compared with previously determined levels of HCAs (measured as MeIQx, DiMeIQx, and PhIP) and polycyclic aromatic hydrocarbons (PAHs) in the meat, levels of HCAs in the urine, and CYP1A2 and NAT2 phenotypes. The levels of mutagenicity in the meat fried at low and high temperatures correlated with levels of HCAs, but not levels of PAHs, in the meat. Also, levels of mutagenicity in unhydrolyzed urine correlated with levels of MeIQx in unhydrolyzed urine (r = 0.36; P = 0.01), and the levels of mutagenicity of hydrolyzed urine correlated with levels of MeIQx (r = 0.34; P = 0.01) and PhIP (r = 0.43; P = 0.001) of hydrolyzed urine. Mutagenicity in unhydrolyzed urine was not influenced by either the CYP1A2 or NAT2 phenotype. The data from this study indicate that urinary mutagenicity correlates with mutagenic exposure from cooked meat and can potentially be used as a marker in etiological studies on cancer.
No preview · Article · Jan 2004 · Environmental and Molecular Mutagenesis
[Show abstract][Hide abstract] ABSTRACT: We have previously reported permanent hair dye use to be a significant risk factor for bladder cancer in US women. We also have examined N-acetyltransferase-2 (NAT2) phenotype in relation to the hair dye-bladder cancer relationship, and found that the association is principally confined to NAT2 slow acetylators. In the present study, we assessed the possible modifying effects of a series of potential arylamine-metabolizing genotypes/phenotypes (GSTM1, GSTT1, GSTP1, NAT1, NAT2, CYP1A2) on the permanent hair dye-bladder cancer association, among female participants (159 cases, 164 controls) of the Los Angeles Bladder Cancer Study. Among NAT2 slow acetylators, exclusive permanent hair dye use was associated with a 2.9-fold increased risk of bladder cancer (95% CI = 1.2-7.5). The corresponding relative risk in NAT2 rapid acetylators was 1.3 (95% CI = 0.6-2.8). Frequency- and duration-related dose-response relationships confined to NAT2 slow acetylators were all positive and statistically significant. No such associations were noted among NAT2 rapid acetylators. Among CYP1A2 'slow' individuals, exclusive permanent hair dye use was associated with a 2.5-fold increased risk of bladder cancer (95% CI = 1.04-6.1). The corresponding risk in CYP1A2 'rapid' individuals was 1.3 (95% CI = 0.6-2.7). Frequency- and duration-related dose-response relationships confined to CYP1A2 'slow' individuals were all positive and statistically significant. No such associations were noted among CYP1A2 'rapid' individuals. Among lifelong non-smoking women, individuals exhibiting the non-NAT1*10 genotype showed a statistically significant increase in bladder cancer risk associated with exclusive permanent hair dye use (OR = 6.8, 95% CI = 1.7-27.4). The comparable OR in individuals with the NAT1*10 genotype was 1.0 (95%CI = 0.2-4.3). Similarly, all frequency- and duration-related dose-response relationships confined to individuals possessing the non-NAT1*10 genotype were positive and statistically significant. On the other hand, individuals of NAT1*10 genotype exhibited no such associations.
[Show abstract][Hide abstract] ABSTRACT: Inter-individual differences in DNA repair capacity have been demonstrated using a variety of phenotypic assays, including reduced repair among patients with squamous cell carcinoma of the head and neck (SCCHN). The XRCC1 DNA repair gene may facilitate DNA strand break and base excision repair. A recent case-control study of SCCHN reported associations with two polymorphisms of the XRCC1 including the exon 6, 194Arg/Arg genotype and the exon 10, 399 Gln/Gln genotype. We conducted an analysis of these two XRCC1 polymorphisms using data from a case-control study of SCCHN. Among white subjects, we found a weak elevation in risk associated with the Arg194Trp polymorphism [odds ratio (OR)=1.3; 95% confidence interval (CI)=0.6-2.9] and a decreased risk for the Arg399Gln polymorphism (OR=0.6; CI=0.4-1.1). We found a markedly decreased odds ratio for the Gln/Gln genotype among whites (OR=0.1; CI=0.04-0.6) and blacks (OR=0.01; CI=0.0004-0.3). We also found a suggestion of an interaction between the Arg194Trp and Arg399Gln polymorphisms and tobacco use. Additional epidemiologic and functional studies are needed to resolve the importance of these XRCC1 polymorphisms in SCCHN.
[Show abstract][Hide abstract] ABSTRACT: Squamous cell carcinoma of the head and neck (SCCHN), including the oral cavity, pharynx, and larynx, provides an ideal tumor model to investigate gene-environment interaction. We conducted a hospital-based case-control study including 182 cases with newly diagnosed SCCHN and 202 controls with nonneoplastic conditions of the head and neck that required surgery. Lifetime tobacco use and risk of SCCHN were evaluated in relation to the polymorphisms of GSTM1, GSTT1, GSTP1, CYP1A1, and NAT1. The main effects of genotype were associated with a slightly increased risk of SCCHN for GSTP1 [age-, race-, and sex-adjusted odds ratio (OR), 1.2; confidence interval (CI), 0.8-1.9], GSTT1 (OR, 1.2; CI, 0.7-2.3), and NAT1 (OR, 1.1; CI, 0.7-1.7). The joint effects of genotype combinations showed some excess risk for the combination of the GSTM1 null genotype and the CYP1A1 Ile/Val polymorphism (OR, 2.6; CI, 0.7-10.3). The analysis of the joint effects (interaction) of the "at-risk" genotypes and tobacco use did not reveal any interaction on either the multiplicative or additive scale for GSTM1, GSTP1, or CYP1A1. However, there was a suggestion of an interaction on the additive scale between the pack-years of tobacco use and the GSTT1 null genotype. The combined heterozygote and homozygote NAT1*10 genotypes also had a suggestive interaction with tobacco smoking history. The results of this study suggest a possible gene-environment interaction for certain carcinogen metabolizing enzymes, but larger studies that fully evaluate the interaction are needed.
No preview · Article · Mar 2000 · Cancer Epidemiology Biomarkers & Prevention
[Show abstract][Hide abstract] ABSTRACT: Mounting evidence suggests that catechol metabolites of estradiol may contribute to the development of estrogen-induced cancers. O-Methylation, catalyzed by catechol-O-methyltransferase (COMT), inactivates catechol estrogens. COMT is polymorphic in the human population, with 25% of Caucasians being homozygous for a low activity allele of the enzyme (COMT(LL)). We hypothesized that low activity COMT may be a risk factor for human breast cancer and designed a PCR-based RFLP assay to determine COMT genotype in a cohort of 112 matched, nested case-control samples. In the total study population, the odds ratios for the association of breast cancer risk with COMT(HL) and COMT(LL) genotypes were 1.30 [confidence interval (CI), 0.66-2.58] and 1.45 (CI, 0.69-3.07), respectively. Postmenopausal COMT(LL) women had a greater than 2-fold increased risk of developing breast cancer [odds ratio (OR), 2.18; CI, 0.93-5.11]. The association of COMT(LL) with the development of postmenopausal breast cancer was stronger and statistically significant in those women with a body mass index >24.47 kg/m2 (OR, 3.58; CI, 1.07-11.98). When COMT(LL) was combined with either glutathione S-transferase (GST) M1 null or with GSTP1 Ile-105-Val/Val-105-Val (intermediate/low activity, respectively) genotypes, the risk for developing postmenopausal breast cancer was also significantly increased. Our findings suggest that the allele encoding low activity COMT may be an important contributor to the postmenopausal development of breast cancer in certain women.
[Show abstract][Hide abstract] ABSTRACT: Epidemiological and experimental evidence indicates that consumption of fried meats in conjunction with certain genotypes of phase I and II metabolism genes poses an elevated risk for colorectal cancer. Parallel to this, the consumption of cruciferous vegetables is associated with a reduced risk of colon cancer. Therefore, we designed a 6-week pilot feeding study to evaluate the effect of these variables on urinary mutagenicity, which is a biomarker associated with fried-meat consumption. Eight subjects were fed fried meats daily for six weeks; four ate cruciferous vegetables, and four ate non-cruciferous vegetables. Urinary mutagenicity was evaluated in the presence of S9 in strain YG1024 of Salmonella, which is a frameshift strain that overproduces acetyltransferase. C18/methanol extracts of 24-h urines collected once each week were tested unhydrolyzed (free mutagenicity) and hydrolyzed (total mutagenicity); the difference between the two was the conjugated mutagenicity. Although not significant, the levels of conjugated urinary mutagenicity doubled among crucifera consumers and decreased to 30% of the initial levels among non-crucifera consumers, suggesting the possibility that crucifera may enhance the level of conjugated urinary mutagenicity resulting from consumption of fried meats. Such an effect would be consistent with the documented ability of cruciferous vegetables to induce phase II enzymes. The NAT2 rapid phenotype was significantly associated with approximately 2-fold increases in conjugated (p = 0.05) and total (p = 0.004) urinary mutagenicity relative to NAT2 slow subjects, consistent with the elevated risk confirmed by the NAT2 rapid phenotype for colorectal cancer among meat consumers. An approximately 2-fold increase in urinary mutagenicity among the GSTM1- subjects relative to the GSTM1+ subjects approached significance for free (p = 0.18) and total (p = 0.13) urinary mutagenicity. This is the first report on (a) the mutagenicity of hydrolyzed urine, which was consistently more mutagenic than unhydrolyzed urine; (b) the potential enhancement of conjugated urinary mutagenicity by crucifera; and (c) the association of the rapid NAT2 and possibly the GSTM1- phenotype with elevated levels of fried meat-associated urinary mutagenicity.
No preview · Article · Dec 1997 · Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis
[Show abstract][Hide abstract] ABSTRACT: The extent to which N-acetylbenzidine and N,N'-diacetylbenzidine are formed may influence benzidine-induced carcinogenesis. This study compared the formation of these metabolites by rat and human liver slices. The relationship between the NAT2 genotype and the formation of these acetylated products was also evaluated in humans. In rat liver slices incubated with 0.05 mM [3H]benzidine for 1 h (n = 3), N-acetylbenzidine and N,N'-diacetylbenzidine represented 8.8 +/- 3.6 and 73 +/- 2.5% respectively of the total radioactivity recovered by HPLC. No unmetabolized benzidine was observed. This suggests that an equilibrium exists between benzidine, N-acetylbenzidine and N,N'-diacetylbenzidine in rat liver slice incubations which favors N,N'-diacetylbenzidine formation. In the presence of 0.1 mM paraoxon, a deacetylase inhibitor, N-acetylbenzidine and N,N'-diacetylbenzidine increased to 13 +/- 0.6 and 79 +/- 0.3% respectively. Within 2 h after incubating human liver slices with 0.014 mM [3H]benzidine (n = 8), benzidine, N-acetylbenzidine and N,N'-diacetylbenzidine represented 19 +/- 5, 34 +/- 4 and 1.6 +/- 0.5%, respectively, of the total radioactivity recovered by HPLC. Thus in the human, conditions in liver slices favor N-acetylbenzidine rather than N,N'-diacetylbenzidine formation. With paraoxon, benzidine, N-acetylbenzidine and N,N'-diacetylbenzidine represented 2 +/- 0.4, 24 +/- 4 and 51 +/- 3%, respectively. This resulted in a 32-fold increase in N,N'-diacetylbenzidine formation. Individuals with rapid NAT2 genotypes formed 1.4-fold more N-acetylbenzidine than slow acetylators. However, this increase was not significant. There was no apparent correlation of N,N'-diacetylbenzidine formation with NAT2 genotype. Similar results were observed when human slices were incubated with 0.09 mM [3H]benzidine. Deacetylase, perhaps more than N-acetyltransferase, influences hepatic metabolism and subsequent carcinogenesis of benzidine in man. These results help explain the species and organ specificity of benzidine carcinogenesis.