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Departments of Epidemiology [C. S., D. C. F., S. M. S., H. C., T. L. V.] and Environmental Health [D. L. E., H. C.], School of Public Health and Community Medicine, University of Washington, Seattle, Washington 98195, and Division of Public Health Sciences, Fred Hutchinson Cancer Research Center, Seattle, Washington 98109 [D. C. F., S. M. S., T. L. V.]
| Abstract |
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| Introduction |
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GST enzymes catalyze conjugation of electrophilic substrates with
glutathione, usually resulting in detoxification of reactive
intermediates (3)
. Common polymorphisms occur in three
human GSTs and seem to influence cancer risk (4, 5, 6)
.
Polymorphisms in which the gene is deleted and no active enzyme is
expressed occur for GSTM1 and GSTT1
(4)
. A single-nucleotide variant in exon 5 of
GSTP1 results in an amino acid substitution,
Ile104Val, and altered enzyme activity (7
, 8)
. GSTM1 and GSTP1 are active in the detoxification of
activated forms of polycyclic aromatic hydrocarbon compounds.
Substrates for GSTT1 include halogenated solvents, such as
dichloromethane, and ethylene oxide, formed endogenously from ethene,
which is present at high levels in cigarette smoke (3)
.
GSTT1 and GSTM1 enzymes also have catalytic activity toward
phospholipid hydroperoxide (9)
, evidence that GSTs may
prevent DNA damage from lipid peroxides formed endogenously as a result
of oxidative stress. Not all reactions catalyzed by GST enzymes result
in detoxification; reactions of certain halogenated compounds catalyzed
by
-class GSTs produce mutagenic species (3)
.
The altered GST activity associated with the polymorphisms is expected to affect cancer risk through decreased protection against DNA damage from reactive electrophiles. GSTs are expressed and have significant activity in the kidney (10, 11, 12) , but few studies have considered GSTs in susceptibility to RCC. Published reports include a case-control study nested within a cohort of German workers occupationally exposed to TCE (13) and a hospital-based case-control study in France (14) . Reduced risk of RCC associated with GSTT1 null genotype was reported in the TCE-exposed cohort. The hospital-based study found no association between GSTM1, GSTT1, or GSTP1 polymorphisms and RCC risk. Thus, previous data on associations between these candidate susceptibility genes and RCC are limited. We investigated GST polymorphisms in a population-based case-control study of RCC.
| Subjects and Methods |
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Paraffin blocks containing fixed tissue from surgery or biopsy were the source of DNA for cases. Blocks containing only normal kidney were used if available. Multiple sections, 10 microns in thickness, were cut from each block and deparaffinized using 1200 ml of xylene, followed by ethanol wash. DNA was extracted using a commercial kit (QIAGEN, Inc.), a method similar to published procedures (16 , 17) . For nine case subjects with no suitable pathology specimen available, a buccal cell sample was collected for genotyping. Buccal cells were obtained using a cytology brush, which was rubbed on the inside of the subjects cheek. Samples were kept on ice during transportation, then frozen at -70°C. DNA was extracted by incubation for 5 min at 95°C with 60 ml of 500 mM NaOH, followed by neutralization with 60 ml of 1 M Tris (pH 8). For controls, DNA was obtained from blood samples, which were kept on ice during transportation, then the buffy coats were isolated and frozen at -70°C until processed for DNA extraction.
GSTM1 and GSTT1 genotypes were determined by multiplexed PCR using three sets of primers to amplify a 215-bp sequence of the GSTM1 gene (18) , a 268-bp sequence of the ß-globin gene (18) , and a 480-bp segment of the GSTT1 gene (19) . Presence or absence of the ß-globin band was used to determine failed PCR. The A/G polymorphism of the GSTP1 gene (20) responsible for the Ile104Val substitution was detected using an oligonucleotide ligation assay, a modification of previously described methods (21) . GSTP1 DNA sequences were amplified by PCR, followed by allele-specific ligation reaction and colorimetric detection. The PCR primers were: forward primer, 5'-GACTGTGTGTTGATCAGGCG-3', and reverse primer 5'-TGCACCCTGACCCAAGAAGG-3'. The oligomer probes for the A/G polymorphism were: wild-type probe, 5'-biotin-AGGACCTCCGCTGCAAATACA-3'; mutant probe, 5'-biotin-AGGACCTCCGCTGCAAATACG-3'; and common reporter probe, 5'-phosphorylated- TCTCCCTCATCTACACCAACT-digoxigenin-3'. The GSTP1 oligonucleotide ligation assay had been verified in the same laboratory by DNA sequencing of PCR products from samples from 60 subjects, with 100% concordance of results. For all genotyping assays, several quality control samples (DNA from volunteers with known genotype) were included with each batch of study samples.
Of 173 case subjects interviewed, tissue was obtained for 132 (85 from tissue blocks containing normal kidney preserved from surgery, 23 from tissue blocks from surgery containing all or part tumor tissue, 15 from tissue blocks from biopsy, and 9 from buccal cell samples). No DNA samples were obtained for 18 interviewed cases who did not return consent forms for access to tissue and for 23 cases for whom tissue was unavailable from the hospitals. The number of cases with interpretable genotype results was 126 for GSTM1, 126 for GSTT1, and 130 for GSTP1. DNA from blood samples was obtained for 505 control subjects, with genotype results available for 505 for GSTM1, 504 for GSTT1, and 491 for GSTP1.
ORs were calculated using unconditional logistic regression. Effect modification among GST genotypes and between genotypes and age, sex, cigarette smoking, and BMI was evaluated using logistic models including interaction terms between categories of the variables of interest, with statistical significance determined by likelihood ratio tests comparing models with and without the interaction term(s). Stata software (Stata Corporation, College Station, TX) was used for statistical analysis.
| Results |
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Frequencies of GSTM1, GSTT1, and GSTP1
genotypes were similar between the two different study groups that
formed the control group (data not shown). Among controls, genotype
frequencies were similar by gender and across age categories (Table 2)
. Hispanic controls had a higher frequency of GSTP1 AG or GG
genotypes than non-Hispanic controls (P = 0.08). No
other important differences were detected by race, ethnicity, or
country of birth. The numbers of non-white and Hispanic subjects were
small. The distribution of GSTT1 genotypes varied by county
of residence (P = 0.01) among controls. When control
subjects who were non-white, Hispanic, or born outside the United
States were excluded from the comparison, the differences in genotypes
across counties persisted. Among cases, the frequency of
GSTM1, GSTT1, and GSTP1 genotypes did
not differ significantly by source of DNA (normal tissue block, tumor
tissue block, biopsy, or buccal cells) or by stage at diagnosis.
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| Discussion |
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Associations between recognized risk factors for RCC, smoking, high blood pressure, and BMI in this population-based case-control study were consistent with what has been reported in previous literature (1 , 22 , 23) . Adjustment for these exposures did not affect the relationship between GSTT1 null genotype and RCC. The major selection factor that differed between participating and nonparticipating cases in our study was stage at diagnosis, which was unrelated to GSTT1 genotype among participating cases and, thus, seems unlikely to bias the observed association between RCC and GSTT1 null. For GSTM1 and GSTP1, the distribution of genotypes among the distant stage cases who were genotyped were similar enough to local and regional stage cases that bias, if any, related to lower participation by distant stage cases would be small. Although association between BMI and prognosis has been reported (24) in RCC cases, BMI was not associated with stage at diagnosis among cases in the present study, so stage bias is unlikely to have influenced the relationships among GSTM1, BMI, and case-control status.
The frequencies of the GSTM1, GSTT1, and GSTP1 genotypes among controls were comparable with what has previously been reported for study populations drawn from Caucasians in North America and Europe (4 , 20 , 25 , 26) . Evidence from other studies indicates that frequencies of the GSTM1 null and possibly the GSTT1 null genotypes vary by race (4) . In our multivariate model, race-adjusted ORs for GST genotypes were similar to crude ORs, and the associations based on all subjects were qualitatively similar to results of models limited to non-Hispanic white subjects. The variation in the frequencies of GSTT1 genotypes among controls by county of residence was not explained by race, and is most likely attributable to chance.
The use of different tissue sources to obtain DNA for cases and controls is a potential limitation of these data. Pathological material was the source of DNA for most cases, whereas blood was used for controls. However, it is unlikely that the source of DNA introduced bias in measurement of genotypes. Tissue blocks containing only normal tissue were used for the majority of case subjects. In a study comparing sources of DNA for PCR-based genotyping, genotypes for GSTM1 and several other genes determined from fixed, paraffin-embedded tissue were 97100% concordant with genotypes determined from fresh frozen tissue from the same subject (27) .
Our finding of an increased frequency of GSTT1 null genotypes among cases suggests that activity of the GSTT1 enzyme protects against development of RCC. Because GST enzymes are active in detoxifying chemicals from cigarette smoke, researchers have hypothesized that the role of the polymorphisms in human cancer would be to modulate the effect of exposures to cigarette smoke. However, in this study the association between GSTT1 and RCC was similar for smokers and nonsmokers. GST enzymes catalyze conjugation of glutathione with a broad range of substrates (3) , including lipid peroxides formed endogenously as a result of oxidative stress (9) . Kidney tissue has high metabolic activity and oxygen demand, a situation in which enhanced endogenous formation of reactive oxidants is possible; a high level of somatic mutations in kidney compared with other tissues has been reported (28) . The association between GSTT1 null genotype and increased RCC risk may be due to reduced protection against endogenous reactive oxidants.
The association between GSTT1 null genotype and RCC risk
seemed to vary by BMI, with the strongest association among subjects in
the lowest tertile of BMI who are otherwise at low risk of RCC. The
association between GSTT1 and RCC among low-BMI subjects may
indicate that different etiological pathways are involved in
development of RCC in low-BMI versus high-BMI individuals.
The mechanism for the association between high BMI and RCC is not well
understood. If this mechanism involves reactive oxidants, a possible
interpretation of our results is that protection by GSTT1 is important
among individuals with low levels of exposure, but becomes overwhelmed
and does not affect risk among the highly exposed. We assessed
potential interaction between GSTT1 genotype and several
exposure variables, so it is possible that the GSTT1-BMI
interaction is a chance finding. Statistical power to detect the
GSTT1-BMI interaction in the present study was 70% at
= 0.05.
The present study is the only report of increased risk of RCC associated with GSTT1 null. The inconsistent results compared with other studies may reflect chance variation, but it is possible that the role of GSTT1 is different in the presence of different patterns of exposures to environmental risk factors for RCC. The case-control study in France (14) , which reported no association with GSTT1, provided no information on the subjects exposures to risk factors for RCC. In the study of solvent-exposed workers in Germany (13) , GSTT1 null genoype was associated with reduced risk of RCC (OR, 0.2; 95% CI, 0.10.9), based on a small number of cases. The authors note that their result is consistent with a model of TCE toxicity to the kidney through GST-catalyzed formation of glutathione conjugates, which are further metabolized in the kidney to toxic compounds, a mechanism that may not be relevant in individuals without occupational solvent exposure. The decreased risk of RCC associated with GSTT1 null genotype among TCE-exposed workers contrasts markedly with the increased risk observed in the present population-based study, in which we would expect that few subjects would have been exposed to TCE. The contrasting results may imply different effects of GSTT1 enzymes according to the presence of specific chemical exposures.
| Acknowledgments |
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| Footnotes |
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1 Supported by the National Institute for
Environmental Health Sciences Center for Ecogenetics and
Environmental Health at the University of Washington (Grant
P30-ES07033) and National Institute for Environmental Health Sciences
Training Grant (T32-ES-07262) in Molecular and Environmental
Epidemiology. The Cancer Surveillance System registry is supported by
National Cancer Institute Contract NO1-VN-67009. ![]()
2 To whom requests for reprints should be
addressed, at Arkansas Cancer Research Center, Slot 795, 4301 West
Markham Street, Little Rock, AR 72205. Phone: (501) 296-1248, ext. 9;
Fax: (501) 686-8297; E-mail: sweeneycarol{at}exchange.uams.edu ![]()
3 The abbreviations used are: RCC, renal cell
carcinoma; GST, glutathione S-transferase; BMI, body
mass index; OR, odds ratio; CI, confidence interval; TCE,
trichloroethene. ![]()
4 T. L. Vaughan, principal investigator
(National Cancer Institute Grant 1RO1-CA53392), and V. Nazar-Stewart,
principal investigator (National Cancer Institute Grant
1RO1-CA62082). ![]()
Received 7/28/99; revised 1/20/00; accepted 1/31/00.
| References |
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activity in liver and kidney of four species. Arch. Toxicol. Suppl., 20: 471-474, 1998.[Medline]
: correlation with induced genetic damage and potential role in endogenous mutagenesis. Cancer Epidemiol. Biomark. Prev., 4: 253-259, 1995.[Abstract]
locus and association with susceptibility to bladder, testicular, and prostate cancer. Carcinogenesis (Lond.), 18: 641-644, 1997.This article has been cited by other articles:
![]() |
S. Karami, P. Boffetta, N. Rothman, R. J. Hung, T. Stewart, D. Zaridze, M. Navritalova, D. Mates, V. Janout, H. Kollarova, et al. Renal cell carcinoma, occupational pesticide exposure and modification by glutathione S-transferase polymorphisms Carcinogenesis, August 1, 2008; 29(8): 1567 - 1571. [Abstract] [Full Text] [PDF] |
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![]() |
J. Shao, P. L. Stapleton, Y. S. Lin, and E. P. Gallagher Cytochrome P450 and Glutathione S-Transferase mRNA Expression in Human Fetal Liver Hematopoietic Stem Cells Drug Metab. Dispos., January 1, 2007; 35(1): 168 - 175. [Abstract] [Full Text] [PDF] |
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![]() |
N. K. Proia, G. M. Paszkiewicz, M. A. Sullivan Nasca, G. E. Franke, and J. L. Pauly Smoking and smokeless tobacco-associated human buccal cell mutations and their association with oral cancer--a review. Cancer Epidemiol. Biomarkers Prev., June 1, 2006; 15(6): 1061 - 1077. [Abstract] [Full Text] [PDF] |
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![]() |
B Yucesoy, V J Johnson, M L Kashon, K Fluharty, V Vallyathan, and M I Luster Lack of association between antioxidant gene polymorphisms and progressive massive fibrosis in coal miners Thorax, June 1, 2005; 60(6): 492 - 495. [Abstract] [Full Text] [PDF] |
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![]() |
L Buzio, G De Palma, P Mozzoni, M Tondel, C Buzio, I Franchini, O Axelson, and A Mutti Glutathione S-transferases M1-1 and T1-1 as risk modifiers for renal cell cancer associated with occupational exposure to chemicals Occup. Environ. Med., October 1, 2003; 60(10): 789 - 793. [Abstract] [Full Text] [PDF] |
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![]() |
C. Sweeney, V. Nazar-Stewart, P. L. Stapleton, D. L. Eaton, and T. L. Vaughan Glutathione S-transferase M1, T1, and P1 Polymorphisms and Survival among Lung Cancer Patients Cancer Epidemiol. Biomarkers Prev., June 1, 2003; 12(6): 527 - 533. [Abstract] [Full Text] [PDF] |
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![]() |
J.-Q. He, J. Ruan, J. E. Connett, N. R. Anthonisen, P. D. Pare, and A. J. Sandford Antioxidant Gene Polymorphisms and Susceptibility to a Rapid Decline in Lung Function in Smokers Am. J. Respir. Crit. Care Med., August 1, 2002; 166(3): 323 - 328. [Abstract] [Full Text] [PDF] |
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![]() |
S. Garte Metabolic Susceptibility Genes As Cancer Risk Factors: Time for a Reassessment? Cancer Epidemiol. Biomarkers Prev., December 1, 2001; 10(12): 1233 - 1237. [Abstract] [Full Text] [PDF] |
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