This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Ulrich, C. M. Articles by Potter, J. D. Search for Related Content PubMed PubMed Citation Articles by Ulrich, C. M. Articles by Potter, J. D.

Lack of Association between the C677T MTHFR Polymorphism and Colorectal Hyperplastic Polyps¹

Cancer Prevention Research Program [C. M. U., S. A. A. B., Y. Y., J. D. P.] and Programs in Cancer Biology [J. B., C. C.] and Epidemiology [ S. M. S.], Fred Hutchinson Cancer Research Center, Seattle, Washington 98109; Department of Epidemiology, University of Washington, Seattle, Washington 98195 [C. M. U., S. M. S., S. A. A. B., J. D. P.]; Wageningen Agricultural University, 6703 HA Wageningen, the Netherlands [E. K.]; South Carolina Cancer Center, University of South Carolina, Columbia, South Carolina 29203 [R. B.]; and University of Minnesota, Minneapolis, Minnesota 55454 [L. F.]

	Abstract

Top Abstract Introduction Materials and Methods Results Discussion References

 
Colorectal hyperplastic polyps are benign lesions that share many risk factors with colorectal adenomas and cancers. Low folate intakes are associated with an increased risk of colon cancer. The enzyme 5,10-methylene-tetrahydrofolate reductase (MTHFR) may be linked to DNA methylation and nucleotide synthesis and thus play a role in the etiology of colorectal neoplasia. We investigated an association between the common MTHFR polymorphism (C677T) and colorectal hyperplastic polyps within the Minnesota Cancer Prevention Research Unit case-control study. Cases (n = 200) were diagnosed with colonoscopically confirmed hyperplastic polyps; controls (n = 645) were derived from the same gastroenterology practice and were polyp-free at colonoscopy. Dietary intakes were estimated from a self-administered food-frequency questionnaire prior to colonoscopy. Multivariate adjusted odds ratios (ORs) and 95% confidence intervals for MTHFR status were 0.8 (0.6–1.2; CT versus CC wild-type) and 0.9 (0.5–1.6; TT versus CC). In subgroup analyses stratified on dietary intakes of folate, vitamin B₁₂, vitamin B₆, or methionine, those with the TT genotype and either low intakes of folate or vitamin B₆ were at increased risk relative to those with normal or high vitamin intake. However, most 95% confidence intervals included 1.0, and no consistent trends were observed. In contrast to our findings on colorectal adenomas, increasing alcohol consumption was associated with an elevated risk of colorectal hyperplastic polyps, regardless of genotype. The MTHFR (C677T) variant genotype does not appear to be related to risk of colorectal hyperplastic polyps, and there is no convincing evidence that MTHFR shows a different relation to risk, dependent on dietary intakes of nutrients related to its pathway.

	Introduction

Top Abstract Introduction Materials and Methods Results Discussion References

 
Colorectal carcinogenesis is a multistage process involving alterations in DNA methylation, hyperproliferation, adenoma formation, and growth, specific somatic genetic changes, and malignant transformation (1) . The role of hyperplastic polyps in this carcinogenic process is uncertain. Whereas these polyps are often considered as benign lesions without carcinogenic potential, mixed polyps showing histological characteristics of both hyperplastic polyps and adenomas have been encountered (2, 3, 4) . However, the frequency of the mixed polyp is not established because pathologists usually describe polyps by their most abnormal feature. Little research on the role of hyperplastic polyps in colon carcinogenesis is available. Many studies have focused on the possibility that rectal hyperplastic polyps are indicator lesions for the presence of more proximal adenomas or carcinomas but have reported disparate findings (5, 6, 7, 8, 9) .

Hyperplastic polyps have molecular features indicative of neoplastic change that are intermediate between normal mucosa and adenomas or carcinomas (10, 11, 12, 13, 14, 15, 16, 17, 18) . Furthermore, they share a number of common risk factors with colorectal adenomas and carcinomas: high alcohol intake, cigarette smoking, and a high body mass index have been found to be associated with an increased risk of hyperplastic polyps; use of aspirin or NSAIDs³ and fiber intake are inversely associated (19 , 20) . Unlike adenomatous polyps, the number and size of hyperplastic polyps does not appear to increase with age (21 , 22) . Overall, it is reasonable to hypothesize that hyperplastic polyps may constitute an early event during colon carcinogenesis, and, if so, that only a small proportion progress to malignant lesions.

In epidemiological observational studies, low-folate diets have been found to increase the risk of adenomatous polyps and colon cancer (23, 24, 25, 26, 27) and the recurrence of adenoma (28) . Other dietary factors, including the vitamins B₁₂ and B₆, as well as methionine, play a role in folate metabolism (29 , 30) . Furthermore, alcohol intake may be related to folate availability, and some investigators have reported that a combination of low-folate, low-methionine, and high-alcohol intake resulted in a greater increase in risk (31 , 32) . The extent to which these dietary factors are related to the risk of hyperplastic polyps is largely unexplored.

The enzyme MTHFR is a central enzyme in folate metabolism (30) . MTHFR plays a key role in the provision of methyl groups by reducing THF to 5-methyl-THF. As substrate for the remethylation of homocysteine to methionine, 5-methyl-THF is linked to the production of S-adenosyl-methionine. S-Adenosyl-methionine is the universal methyl donor in humans and required for DNA methylation. The methylation of homocysteine is catalyzed by the enzyme methionine synthase (requiring vitamin B₁₂ as a cofactor). Through its links to the production of dTMP via thymidylate synthase and to purine synthesis, MTHFR also plays a role in the provision of nucleotides essential for DNA synthesis.

We hypothesized that a defect in MTHFR could impact both DNA methylation and DNA synthesis and predicted interactions between such a defect, the nutritional cofactors vitamin B₁₂, vitamin B₆, and the substrate folate, and colorectal carcinogenesis. There is substantial experimental evidence that deficiencies in folate or vitamin B₁₂ can affect DNA methylation (33 , 34) , result in deoxynucleotide pool disturbances (35, 36, 37) , in uracil misincorporation into human DNA, and in genomic DNA strand breaks (38, 39, 40) . Chromosome breaks are characteristic of nearly all human cancers, including colorectal cancer (41) .

A common polymorphism in the MTHFR gene (C677T) has been identified. Individuals with the variant MTHFR TT genotype show 30% of the enzyme activity found among those with the wild-type (CC) enzyme (42) . Individuals who are heterozygous for the mutation (CT) have 65% of wild-type enzyme activity (42) . Individuals with the TT genotype, particularly if combined with a diet low in folate, have elevated plasma homocysteine levels, thus illustrating the physiological importance of this genotype (43, 44, 45, 46, 47, 48, 49) .

Previous studies of colorectal cancer (50 , 51) found a significantly decreased risk of colorectal cancer associated with the variant TT genotype that was not observed among those with low folate intakes or serum levels. Our own study of adenomas (52) showed an increased risk with TT genotype and low intakes of nutrients in the MTHFR pathway. We report here on the association between the MTHFR genotype and colorectal hyperplastic polyps within a clinic-based case-control study and explore possible modifications in risk with differing levels of intakes of folate, vitamin B₁₂, vitamin B₆, methionine, and alcohol.

	Materials and Methods

Top Abstract Introduction Materials and Methods Results Discussion References

 
Study Subjects.
Subject recruitment for this case-control study has been described elsewhere (53) . In brief, cases and controls were recruited through a large multiclinic private gastroenterology practice, Digestive Healthcare, which conducts colonoscopies in 10 hospitals, and, at the time of this study, undertook 60% of all colonoscopies in metropolitan Minneapolis. All patients of ages 30–74 years who were scheduled for colonoscopy at all 10 Digestive Healthcare clinics between April 1991 and April 1994 were screened for the eligibility criteria described below and recruited prior to colonoscopy. Recruitment was initiated at the time of scheduling of the colonoscopy. The intent was to recruit subjects with both patient and recruiter blind to the final diagnosis. Indications for colonoscopy included bleeding, follow-up to sigmoidoscopy or barium enema, family history, and screening; indications by case/control status have been described previously (52) .

Eligibility criteria for all participants were: resident of Twin Cities metropolitan area; age 30–74 years; English speaking; no known genetic syndromes associated with predisposition to colonic neoplasia; no individual history of cancer (except nonmelanoma skin cancer); and no history of inflammatory bowel disease. In addition, cases were eligible if their visit resulted in the diagnosis of colon or rectal hyperplastic polyps; carcinoma patients were excluded; controls were defined as being free of all polyps (hyperplastic or adenomatous) at colonoscopy.

The questionnaires used were self-administered, and patients received all study material (including food frequency questionnaires) before their clinic visit. At colonoscopy, the signed consent form and completed questionnaires were collected, and blood was drawn. The colonoscopy findings were recorded on standardized forms. Polyp size was measured in vivo by comparison of the polyp with a fully opened standard-sized flexible colonoscopy forceps. Upon removal, polyps were examined histologically by the study pathologist. Only participants with a complete colonoscopy reaching the cecum were eligible. The presence or absence of pathology was determined and, based on colonoscopy and pathology findings, participants were assigned to one of the following three groups: (a) adenomatous polyp group (defined as either adenomatous or mixed pathology, n = 575); (b) hyperplastic polyp-only group (n = 219); and (c) colonoscopy-negative group (controls, n = 708). The adenomatous polyp group was considered as a separate group and is not discussed further in this report (52) . The participation rate for all colonoscoped patients was 68%.

Questionnaire.
Questionnaires included information on dietary intake, physical activity, smoking habits, anthropometric measurements, medical information, demographic information, reproductive history (women), and family history of polyps and cancer (especially history of colon, breast, endometrial, or ovarian cancers). Study staff followed up with the participants when data were incomplete.

The dietary questionnaire was adapted from the Willett semiquantitative food frequency questionnaire, which has been evaluated for validity and repeatability within this study (54 , 55) , as well as the Nurses’ Health Study cohort (56) , the Iowa Women’s Health Study cohort (57) , and the Health Professionals Follow-up Study cohort (58) . Participants were asked to recount their average consumption, over the past year, of 127 food items. For each food, a commonly used portion size was defined and participants selected one of nine categories ranging from "never or less than once per month" to "6 or more per day" to describe their frequency of consumption. Data on the brand of breakfast cereal and the brand and frequency of multivitamin and individual vitamin supplement use were collected. Daily intakes of nutrients were computed using composition values from United States Department of Agriculture sources (59) , which are continually supplemented by other published sources and personal communications from laboratories and manufacturers. Among a similar study population, correlation coefficients of this instrument on repeat administration were r = 0.62 for dietary folate, r = 0.67 for vitamin B₁₂ intake, and r = 0.99 for alcohol consumption (57) . Giovannucci et al. (31) compared Willett questionnaire values with RBC folate levels (an indicator of long-term folate status) and reported correlations between folate intake and erythrocyte folate levels of r = 0.55 for women and r = 0.56 for men.

Blood Collection and Processing.
Venous blood was collected from each participant in two 20-ml ACD vacutainer tubes. White cells, red cells, and plasma were separated according to a standardized protocol. White cells were stored, in appropriate cell culture medium, as multiple 0.5-ml aliquots at -70°C for DNA extraction or preparation of cell lines. White cells were shipped in frequent batches to the University of Utah for extraction of DNA. DNA was extracted using the PureGene DNA isolation kit (Gentra Systems, Inc., Minneapolis, MN). DNA was quantitated and examined for purity by UV absorption at 260 and 280 nm (60) , and extracted DNA was shipped to Seattle for genotyping analyses.

MTHFR Genotyping.
The MTHFR polymorphism at bp 677 was determined using the PCR/RFLP method of Frosst et al. (42) . PCR reactions were done on a Deltacycler II thermal cycler in 96-well plates (Ericomp, San Diego, CA). Primers (5'-TGA AGG AGA AGG TGT CTG CGG GA-3') and (5'-AGG ACG GTG CGG TGA GAG TG-3') were used to amplify a portion of the MTHFR sequence from 100 ng of genomic DNA in a 30-µl reaction containing 3 µl of 10x PCR buffer [100 mM Tris-HCl (pH 8.3) at 25°C, 500 mM KCl, 15 mM MgCl₂, and 0.01% (w/v) gelatin; Perkin-Elmer], 50 µg/ml BSA, 0.2 mM deoxynucleotide triphosphates, 0.2 µM each primer, and 1 unit of Taq DNA polymerase. Cycling conditions were: initial melting at 93°C for 5 min, then 30 amplification cycles of 93°C for 60 s, 58°C for 60 s, and 72°C for 60 s. Upon amplification, the 198-bp MTHFR fragment was digested with HinfI in a 20-µl reaction containing 10 µl of PCR fragment, 2 µl of 10x buffer H (Amersham Life Science; supplied by the manufacturer), and 4 units of HinfI at 37°C for 1 h. The resulting digestion products were separated on a 3% NuSieve agarose gel (FHC Corp.), and the ethidium bromide-stained bands were photographed on a UV transilluminator.

Wild-type (CC) individuals were characterized by a 198-bp fragment only, heterozygotes (CT) by fragments of 198, 175, and 23 bp, and homozygote variants (TT) by fragments of 175 and 23 bp. Blinded repeat genotyping was undertaken for 20 DNA samples. Reproducibility of the genotype was 100%. DNA quality or quantity was insufficient for MTHFR genotyping in 19 cases and 63 controls, which resulted in a final sample size of 200 cases and 645 controls.

Statistical Data Analysis.
Standard techniques for unmatched case-control studies were used. Odds ratios and 95% confidence intervals were estimated by logistic regression analysis. The association between MTHFR genotype and hyperplastic polyps was estimated first in the entire study population and then in subsets based on sex, age, polyp characteristics, and dietary intakes. We also undertook a polytomous regression analysis with four possible outcomes: clean colon; hyperplastic polyp(s) only; hyperplastic plus adenomatous polyps; and adenoma only.

Effect modification was evaluated by stratification on the variable of interest, and ORs in each stratum were compared. Potential confounders were evaluated in the following manner. An age- and sex-adjusted OR was computed for each association. Subsequently, a full multivariate model with all potential confounders was fitted, and the log likelihood and the ORs were compared with the age-sex-adjusted model. Then all factors were eliminated separately from the model to evaluate its effect on the OR of interest. Only covariates that altered any OR of interest by at least 10% were maintained in the model. The following potential confounding factors were evaluated: age, sex, race/ethnicity, HRT (ever/never), BMI, waist:hip ratio, pack-years of smoking, regular use of aspirin (at least 1 per week), regular use of NSAIDs (at least 1 per week), hours of physical activity, and the dietary intake variables kilocalories, dietary fiber, percentage of kilocalories from fat, vitamin B₆, vitamin B₁₂, folate, and alcohol.

The subset of these variables maintained for multivariate adjustment was: age, sex, BMI, percentage of kilocalories from fat, dietary fiber intake (g), HRT use (ever/never), pack-years of smoking, and dietary intakes of folate, vitamin B₁₂, vitamin B₆, methionine, and alcohol. All adjustment variables were included in the model as continuous variables, with the exception of HRT use and sex. In general, the confounding effects were small and often only apparent in the analyses stratified by dietary intakes. With the exception of number of pack years and folate intake (both greater among those with TT genotype), confounding factors were related more to diet than the MTHFR genotype. For consistency, we report the multivariate-adjusted estimates throughout.

Tertiles of consumption of nutrients were determined based on the distribution in the controls. Alcohol intake was divided into three groups by separating nondrinkers from drinkers and dividing those who drank alcohol by their median intake.

Statistical significance testing was conducted on multiple levels. Differences in nutrient intakes and other population characteristics between cases and controls were assessed with t tests and ² tests. Nutrient intakes that were not normally distributed were log transformed (square root transformed for alcohol intake). To evaluate the dose-response relationship between nutrient intakes or other variables and colorectal hyperplastic polyps within each of the three genotypes, a test for trend was used. Effect modification of the relation between nutrients and other variables and risk of polyps by genotype was assessed by testing for different slopes with nutrient intake across genotype. All tests of statistical significance were two-sided.

	Results

Top Abstract Introduction Materials and Methods Results Discussion References

 
Characteristics of the study population are shown in Table 1 . Cases and controls were similar with respect to race/ethnicity and age. They also did not differ on use of aspirin, NSAIDs, and HRT (data not shown). Cases were more likely to be male and to be current smokers. Prevalences of the MTHFR genotype did not differ between cases and controls; however, among cases, the MTHFR genotype was not distributed according to a Hardy-Weinberg Equilibrium. The CT genotype was relatively underrepresented. With respect to dietary intakes, there were few differences between cases and controls. A larger proportion of the cases reported consuming alcohol, and the average alcohol intake was higher in cases than in controls.

Associations between the MTHFR genotype and risk of hyperplastic polyps are shown in Table 2 . Overall, there was no significant association between the MTHFR genotype and risk of hyperplastic polyps, and multivariate adjustment did not change these results. There were also no consistent trends in risk across genotypes within subgroups, e.g., based on sex.

	Discussion

Top Abstract Introduction Materials and Methods Results Discussion References

 
To our knowledge, this is the first study to report on the risk of colorectal hyperplastic polyps associated with the MTHFR genotype. The results presented here on hyperplastic polyps differ from those obtained on adenomatous polyps in the same population (52) , as well as those obtained from other studies of colon cancer and adenoma (50 , 51 , 61 , 62) . In the study of adenomatous polyps, we observed elevated risks associated with the variant MTHFR genotype (TT) among those with low intakes of folate, vitamin B₁₂, and vitamin B₆. These increases in risk were particularly pronounced among the elderly (>60 years of age). However, in this study of hyperplastic polyps and MTHFR genotype, little association with the MTHFR genotype and no consistent trends across nutrient intakes were seen. Furthermore, increasing alcohol consumption was associated with an increased risk of hyperplastic polyps, irrespective of genotype. In contrast, for adenomatous polyps we previously observed a significant gene-environment interaction between alcohol intake and MTHFR genotype; surprisingly, in that study, lower risks were found among those with the TT genotype who drank any alcohol.

Hyperplastic polyps appear to be subject to fewer mutagenic events than colorectal adenomas or carcinomas. For example, mutations in the p53 tumor suppressor gene occur frequently in carcinoma and in some adenomas but have not been observed in hyperplastic polyps (16 , 17) . A similar relationship has been reported for adenomatous polyposis coli mutations (18) . In contrast, K-ras activation appears to occur quite frequently (about 12–50%) in hyperplastic polyps, comparable, perhaps, with that seen in adenomas (37–56%; Refs. 16 and 18 ). On the basis of our study of adenomas, we hypothesized that the MTHFR TT genotype in combination with low intakes of folate or vitamins B₁₂ and B₆ will result in mutagenesis, both because of disturbances in DNA synthesis and DNA methylation changes. Disturbances in DNA synthesis can result in misincorporation of uracil instead of thymidine into DNA, resulting in DNA strand breaks. Because hyperplastic polyps show fewer mutagenic events than adenomas and carcinomas, it is plausible that there would be no increase in risk of hyperplastic polyps in those with a variant MTHFR genotype. Reduced DNA methylation could alter gene expression, but its effects on mutagenesis are less well understood.

Cases with hyperplastic polyps were significantly younger (mean age, 53.7 years) than those with adenomatous polyps (mean age, 58.1 years). Among the latter, most of the associations between MTHFR genotype and adenomas associated with low dietary intakes of B vitamins were evident among older individuals (>60 years of age; Ref. 52 ). This may be explained by a decline in the ability to absorb certain vitamins with increasing age, thus exacerbating risks associated particularly with low intakes. Consistently, the relative risk for hyperplastic polyps associated with the TT genotype was higher among individuals >60 years (Table 2) , yet the number of cases in this age group was small. The younger age of the hyperplastic polyp patients and the different biology, therefore, may both contribute to the difference in findings compared with adenomatous polyps.

Another possible explanation for the absence of an association in this study may be study size. The number of cases in this study was smaller (n = 200) than in the adenoma study, and only 26 cases were carriers of the variant TT genotype. Within such small strata, chance plays a larger role, and the statistical power to detect a gene-environment interaction is small. Our ability to evaluate low B vitamin intakes, which comprised the strata at greatest risk in the adenoma study, was therefore restricted, and our results should be considered exploratory. Another limitation of this study was the reliance on dietary data from questionnaires. Strengths of this study are its specific focus on hyperplastic polyps, its design (patients were drawn from the same clinic, and both cases and controls had complete colonoscopies), and the comprehensive information obtained on dietary intakes.

In conclusion, in contrast to previous findings on adenomatous polyps, our data do not provide evidence of associations between the MTHFR genotype, nutrients involved in folate metabolism, and colorectal hyperplastic polyps. These observations add to the accumulating evidence of the differing biology of adenomatous and hyperplastic polyps.

	Acknowledgments

 
We thank Dale McLarren for assistance with the data management.

	Footnotes

 
The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

¹ Supported by National Cancer Institute research Grants CA 72859-01 and P01 CA50405.

² To whom requests for reprints should be addressed, at Cancer Prevention Research Program, Fred Hutchinson Cancer Research Center, 1100 Fairview Avenue N, MP-900, P. O. Box 19024, Seattle, WA 98109-1024. Phone: (206) 667-4683; Fax: (206) 667-597; E-mail: jpotter{at}fhcrc.org

³ The abbreviations used are: NSAID, nonsteroidal anti-inflammatory drug; MTHFR, 5,10-methylene-tetrahydrofolate reductase; THF, 5,10-methylene tetrahydrofolate; HRT, hormone replacement therapy; BMI, body mass index.

Received 1/ 4/99; accepted 1/14/00.

	References

Top Abstract Introduction Materials and Methods Results Discussion References

 

1. Fearon E. R., Vogelstein B. A genetic model for colorectal tumorigenesis. Cell, 61: 759-767, 1990.[Medline]
2. Veress B., Gabrielsson N., Granqvist S., Billing H. Mixed colorectal polyps. An immunohistologic and mucin-histochemical study. Scand. J. Gastroenterol., 26: 1049-1056, 1991.[Medline]
3. Longacre T. A., Fenoglio-Preiser C. M. Mixed hyperplastic adenomatous polyps/serrated adenomas. A distinct form of colorectal neoplasia. Am. J. Surg. Pathol., 14: 524-537, 1990.[Medline]
4. Teoh H. H., Delahunt B., Isbister W. H. Dysplastic and malignant areas in hyperplastic polyps of the large intestine. Pathology, 21: 138-142, 1989.[Medline]
5. Provenzale D., Garrett J. W., Condon S. E., Sandler R. S. Risk for colon adenomas in patients with rectosigmoid hyperplastic polyps [see comments]. Ann. Intern. Med., 113: 760-763, 1990.
6. Foutch P. G., DiSario J. A., Pardy K., Mai H. D., Manne R. K. The sentinel hyperplastic polyp: a marker for synchronous neoplasia in the proximal colon. Am. J. Gastroenterol., 86: 1482-1485, 1991.[Medline]
7. Blue M. G., Sivak M. V., Jr., Achkar E., Matzen R., Stahl R. R. Hyperplastic polyps seen at sigmoidoscopy are markers for additional adenomas seen at colonoscopy [see comments]. Gastroenterology, 100: 564-566, 1991.[Medline]
8. Brady P. G., Straker R. J., McClave S. A., Nord H. J., Pinkas M., Robinson B. E. Are hyperplastic rectosigmoid polyps associated with an increased risk of proximal colonic neoplasms? [see comments]. Gastrointest. Endosc., 39: 481-485, 1993.[Medline]
9. Sciallero S., Costantini M., Bertinelli E., Castiglione G., Onofri P., Aste H., Casetti T., Mantellini P., Bucchi L., Parri R., Boni L., Bonelli L., Gatteschi B., Lanzanova G., Rinaldi P., Giannini A., Naldoni C., Bruzzi P. Distal hyperplastic polyps do not predict proximal adenomas: results from a multicentric study of colorectal adenomas. Gastrointest. Endosc., 46: 124-130, 1997.[Medline]
10. Polyak K., Hamilton S. R., Vogelstein B., Kinzler K. W. Early alteration of cell-cycle-regulated gene expression in colorectal neoplasia. Am. J. Pathol., 149: 381-387, 1996.[Abstract]
11. Kang M., Mitomi H., Sada M., Tokumitsu Y., Takahashi Y., Igarashi M., Katsumata T., Okayasu I. Ki-67, p53, and Bcl-2 expression of serrated adenomas of the colon. Am. J. Surg. Pathol., 21: 417-423, 1997.[Medline]
12. Risio M., Coverlizza S., Ferrari A., Candelaresi G. L., Rossini F. P. Immunohistochemical study of epithelial cell proliferation in hyperplastic polyps, adenomas, and adenocarcinomas of the large bowel. Gastroenterology, 94: 899-906, 1988.[Medline]
13. Bosari S., Moneghini L., Graziani D., Lee A. K., Murray J. J., Coggi G., Viale G. bcl-2 oncoprotein in colorectal hyperplastic polyps, adenomas, and adenocarcinomas. Hum. Pathol., 26: 534-540, 1995.[Medline]
14. Sinicrope F. A., Ruan S. B., Cleary K. R., Stephens L. C., Lee J. J., Levin B. bcl-2 and p53 oncoprotein expression during colorectal tumorigenesis. Cancer Res., 55: 237-241, 1995.[Abstract/Free Full Text]
15. Kaklamanis L., Savage A., Mortensen N., Tsiotos P., Doussis-Anagnostopoulou I., Biddolph S., Whitehouse R., Harris A. L., Gatter K. C. Early expression of bcl-2 protein in the adenoma-carcinoma sequence of colorectal neoplasia. J. Pathol., 179: 10-14, 1996.[Medline]
16. Otori K., Oda Y., Sugiyama K., Hasebe T., Mukai K., Fujii T., Tajiri H., Yoshida S., Fukushima S., Esumi H. High frequency of K-ras mutations in human colorectal hyperplastic polyps. Gut, 40: 660-663, 1997.[Abstract/Free Full Text]
17. Kikuchi Y., Dinjens W. N., Bosman F. T. Proliferation and apoptosis in proliferative lesions of the colon and rectum. Virchows Arch., 431: 111-117, 1997.[Medline]
18. Uchida H., Ando H., Maruyama K., Kobayashi H., Toda H., Ogawa H., Ozawa T., Matsuda Y., Sugimura H., Kanno T., Baba S. Genetic alterations of mixed hyperplastic adenomatous polyps in the colon and rectum. Jpn. J. Cancer Res., 89: 299-306, 1998.[Medline]
19. Kearney J., Giovannucci E., Rimm E. B., Stampfer M. J., Colditz G. A., Ascherio A., Bleday R., Willett W. C. Diet, alcohol, and smoking and the occurrence of hyperplastic polyps of the colon and rectum (United States). Cancer Causes Control, 6: 45-56, 1995.[Medline]
20. Martinez M. E., McPherson R. S., Levin B., Glober G. A. A case-control study of dietary intake and other lifestyle risk factors for hyperplastic polyps. Gastroenterology, 113: 423-429, 1997.[Medline]
21. Clark J. C., Collan Y., Eide T. J., Esteve J., Ewen S., Gibbs N. M., Jensen O. M., Koskela E., MacLennan R., Simpson J. G., et al Prevalence of polyps in an autopsy series from areas with varying incidence of large-bowel cancer. Int. J. Cancer, 36: 179-186, 1985.[Medline]
22. Cannon-Albright L. A., Bishop D. T., Samowitz W., DiSario J. A., Lee R., Burt R. W. Colonic polyps in an unselected population: prevalence, characteristics, and associations [see comments]. Am. J. Gastroenterol., 89: 827-831, 1994.[Medline]
23. Freudenheim J. L., Graham S., Marshall J. R., Haughey B. P., Cholewinski S., Wilkinson G. Folate intake and carcinogenesis of the colon and rectum. Int. J. Epidemiol., 20: 368-374, 1991.[Abstract/Free Full Text]
24. Benito E., Obrador A., Stiggelbout A., Bosch F. X., Mulet M., Munoz N., Kaldor J. A population-based case-control study of colorectal cancer in Majorca. I. Dietary factors. Int. J. Cancer, 45: 69-76, 1990.[Medline]
25. Meyer F., White E. Alcohol and nutrients in relation to colon cancer in middle-aged adults. Am. J. Epidemiol., 138: 225-236, 1993.[Abstract/Free Full Text]
26. Paspatis G. A., Kalafatis E., Oros L., Xourgias V., Koutsioumpa P., Karamanolis D. G. Folate status and adenomatous colonic polyps. A colonoscopically controlled study. Dis. Colon Rectum, 38: 64-67, 1995.[Medline]
27. Glynn S. A., Albanes D., Pietinen P., Brown C. C., Rautalahti M., Tangrea J. A., Gunter E. W., Barrett M. J., Virtamo J., Taylor P. R. Colorectal cancer and folate status: a nested case-control study among male smokers. Cancer Epidemiol. Biomark. Prev., 5: 487-494, 1996.[Abstract]
28. Baron J. A., Sandler R. S., Haile R. W., Mandel J. S., Mott L. A., Greenberg E. R. Folate intake, alcohol consumption, cigarette smoking, and risk of colorectal adenomas. J. Natl. Cancer Inst., 90: 57-62, 1998.[Abstract/Free Full Text]
29. Selhub J., Miller J. W. The pathogenesis of homocysteinemia: interruption of the coordinate regulation by S-adenosylmethionine of the remethylation and transsulfuration of homocysteine. Am. J. Clin. Nutr., 55: 131-138, 1992.[Abstract/Free Full Text]
30. Wagner C. . Biochemical Role of Folate in Cellular Metabolism. Folate in Health and Disease, 23-42, Marcel Dekker New York 1995.
31. Giovannucci E., Stampfer M. J., Colditz G. A., Rimm E. B., Trichopoulos D., Rosner B. A., Speizer F. E., Willett W. C. Folate, methionine, and alcohol intake and risk of colorectal adenoma. J. Natl. Cancer Inst., 85: 875-884, 1993.[Abstract/Free Full Text]
32. Giovannucci E., Rimm E. B., Ascherio A., Stampfer M. J., Colditz G. A., Willett W. C. Alcohol, low-methionine-low-folate diets, and risk of colon cancer in men [see comments]. J. Natl. Cancer Inst., 87: 265-273, 1995.[Abstract/Free Full Text]
33. Miller J. W., Nadeau M. R., Smith J., Smith D., Selhub J. Folate-deficiency-induced homocysteinaemia in rats: disruption of S-adenosylmethionine’s co-ordinate regulation of homocysteine metabolism. Biochem. J., 298: 415-419, 1994.
34. Kim Y. I., Pogribny I. P., Basnakian A. G., Miller J. W., Selhub J., James S. J., Mason J. B. Folate deficiency in rats induces DNA strand breaks and hypomethylation within the p53 tumor suppressor gene. Am. J. Clin. Nutr., 65: 46-52, 1997.[Abstract/Free Full Text]
35. James S. J., Yin L. Diet-induced DNA damage and altered nucleotide metabolism in lymphocytes from methyl-donor-deficient rats. Carcinogenesis (Lond.), 10: 1209-1214, 1989.[Abstract/Free Full Text]
36. James S. J., Miller B. J., Basnakian A. G., Pogribny I. P., Pogribna M., Muskhelishvili L. Apoptosis and proliferation under conditions of deoxynucleotide pool imbalance in liver of folate/methyl deficient rats. Carcinogenesis (Lond.), 18: 287-293, 1997.[Abstract/Free Full Text]
37. James S. J., Cross D. R., Miller B. J. Alterations in nucleotide pools in rats fed diets deficient in choline, methionine and/or folic acid. Carcinogenesis (Lond.), 13: 2471-2474, 1992.[Abstract/Free Full Text]
38. Blount B. C., Mack M. M., Wehr C. M., MacGregor J. T., Hiatt R. A., Wang G., Wickramasinghe S. N., Everson R. B., Ames B. N. Folate deficiency causes uracil misincorporation into human DNA and chromosome breakage: implications for cancer and neuronal damage. Proc. Natl. Acad. Sci. USA, 94: 3290-3295, 1997.[Abstract/Free Full Text]
39. James S. J., Yin L., Swendseid M. E. DNA strand break accumulation, thymidylate synthesis and NAD levels in lymphocytes from methyl donor-deficient rats. J. Nutr., 119: 661-664, 1989.
40. Pogribny I. P., Basnakian A. G., Miller B. J., Lopatina N. G., Poirier L. A., James S. J. Breaks in genomic DNA and within the p53 gene are associated with hypomethylation in livers of folate/methyl-deficient rats. Cancer Res., 55: 1894-1901, [published erratum appears in Cancer Res., 55: 2711, 1995]. 1995.[Abstract/Free Full Text]
41. Vogelstein B., Fearon E. R., Kern S. E., Hamilton S. R., Preisinger A. C., Nakamura Y., White R. Allelotype of colorectal carcinomas. Science (Washington DC), 244: 207-211, 1989.[Abstract/Free Full Text]
42. Frosst P., Blom H. J., Milos R., Goyette P., Sheppard C. A., Matthews R. G., Boers G. J., den Heijer M., Kluijtmans L. A., van den Heuvel L. P., Rozen R. A candidate genetic risk factor for vascular disease: a common mutation in methylenetetrahydrofolate reductase [letter]. Nat. Genet., 10: 111-113, 1995.[Medline]
43. Deloughery T. G., Evans A., Sadeghi A., McWilliams J., Henner W. D., Taylor L. M., Jr., Press R. D. Common mutation in methylenetetrahydrofolate reductase. Correlation with homocysteine metabolism and late-onset vascular disease. Circulation, 94: 3074-3078, 1996.[Abstract/Free Full Text]
44. Ma J., Stampfer M. J., Hennekens C. H., Frosst P., Selhub J., Horsford J., Malinow M. R., Willett W. C., Rozen R. Methylenetetrahydrofolate reductase polymorphism, plasma folate, homocysteine, and risk of myocardial infarction in US physicians. Circulation, 94: 2410-2416, 1996.[Abstract/Free Full Text]
45. Harmon D. L., Woodside J. V., Yarnell J. W., McMaster D., Young I. S., McCrum E. E., Gey K. F., Whitehead A. S., Evans A. E. The common "thermolabile" variant of methylene tetrahydrofolate reductase is a major determinant of mild hyperhomocysteinaemia. Q. J. Med., 89: 571-577, 1996.[Abstract]
46. Malinow M. R., Nieto F. J., Kruger W. D., Duell P. B., Hess D. L., Gluckman R. A., Block P. C., Holzgang C. R., Anderson P. H., Seltzer D., Upson B., Lin Q. R. The effects of folic acid supplementation on plasma total homocysteine are modulated by multivitamin use and methylenetetrahydrofolate reductase genotypes. Arterioscler. Thromb. Vasc. Biol., 17: 1157-1162, 1997.[Abstract/Free Full Text]
47. Jacques P. F., Bostom A. G., Williams R. R., Ellison R. C., Eckfeldt J. H., Rosenberg I. H., Selhub J., Rozen R. Relation between folate status, a common mutation in methylenetetrahydrofolate reductase, and plasma homocysteine concentrations. Circulation, 93: 7-9, 1996.[Abstract/Free Full Text]
48. Verhoef P., Kok F. J., Kluijtmans L. A., Blom H. J., Refsum H., Ueland P. M., Kruyssen D. A. The 677CT mutation in the methylenetetrahydrofolate reductase gene: associations with plasma total homocysteine levels and risk of coronary atherosclerotic disease. Atherosclerosis, 132: 105-113, 1997.[Medline]
49. Schwartz S. M., Siscovick D. S., Malinow M. R., Rosendaal F. R., Beverly R. K., Hess D. L., Psaty B. M., Longstreth W. T., Jr., Koepsell T. D., Raghunathan T. E., Reitsma P. H. Myocardial infarction in young women in relation to plasma total homocysteine, folate, and a common variant in the methylenetetrahydrofolate reductase gene. Circulation, 96: 412-417, 1997.[Abstract/Free Full Text]
50. Ma J., Stampfer M. J., Giovannucci E., Artigas C., Hunter D. J., Fuchs C., Willett W. C., Selhub J., Hennekens C. H., Rozen R. Methylenetetrahydrofolate reductase polymorphism, dietary interactions, and risk of colorectal cancer. Cancer Res., 57: 1098-1102, 1997.[Abstract/Free Full Text]
51. Chen J., Giovannucci E., Kelsey K., Rimm E. B., Stampfer M. J., Colditz G. A., Spiegelman D., Willett W. C., Hunter D. J. A methylenetetrahydrofolate reductase polymorphism and the risk of colorectal cancer. Cancer Res., 56: 4862-4864, 1996.[Abstract/Free Full Text]
52. Ulrich C., Kampman E., Bigler J., Schwartz S., Chen C., Bostick R., Fosdick L., Beresford S., Yasui Y., Potter J. Colorectal adenomas and the C677T MTHFR polymorphism: evidence for gene-environment interaction?. Cancer Epidemiol. Biomark. Prev., 8: 659-668, 1999.[Abstract/Free Full Text]
53. Potter J. D., Bostick R. M., Grandits G. A., Fosdick L., Elmer P., Wood J., Grambsch P., Louis T. A. Hormone replacement therapy is associated with lower risk of adenomatous polyps of the large bowel: the Minnesota Cancer Prevention Research Unit Case-Control Study. Cancer Epidemiol. Biomark. Prev., 5: 779-784, 1996.[Abstract]
54. Smith-Warner S. A., Elmer P. J., Fosdick L., Tharp T. M., Randall B. Reliability and comparability of three dietary assessment methods for estimating fruit and vegetable intakes. Epidemiology, 8: 196-201, 1997.[Medline]
55. Elmer P., Fosdick L., Smith S., Tharp T. Reliability and validity for nutrients, foods, and food groups of an expanded Willett food frequency questionnaire for cancer-prevention studies. Am. J. Clin. Nutr., 65: 1299S 1997.
56. Willett W. C., Sampson L., Stampfer M. J., Rosner B., Bain C., Witschi J., Hennekens C. H., Speizer F. E. Reproducibility and validity of a semiquantitative food frequency questionnaire. Am. J. Epidemiol., 122: 51-65, 1985.[Abstract/Free Full Text]
57. Munger R. G., Folsom A. R., Kushi L. H., Kaye S. A., Sellers T. A. Dietary assessment of older Iowa women with a food frequency questionnaire: nutrient intake, reproducibility, and comparison with 24-hour dietary recall interviews. Am. J. Epidemiol., 136: 192-200, 1992.[Abstract/Free Full Text]
58. Rimm E. B., Giovannucci E. L., Stampfer M. J., Colditz G. A., Litin L. B., Willett W. C. Reproducibility and validity of an expanded self-administered semiquantitative food frequency questionnaire among male health professionals. Am. J. Epidemiol., 135: 1114-1126, 1992.[Abstract/Free Full Text]
59. U. S. Dept. of Agriculture . Composition of Foods–Raw, Processed, and Prepared. Agricultural Handbook., 1963–1988 United States Government Printing Office Washington
60. Sambrook J., Fritsch E. F., Maniatis T. . Molecular Cloning: A Laboratory Manual, Cold Spring Harbor Laboratory Press New York 1989.
61. Slattery M. L., Potter J. D., Samowitz W., Schaffer D., Leppert M. Methylenetetrahydrofolate reductase, diet, and risk of colon cancer. Cancer Epidemiol. Biomark. Prev., 8: 513-518, 1999.[Abstract/Free Full Text]
62. Chen J., Giovannucci E., Hankinson S. E., Ma J., Willett W. C., Spiegelman D., Kelsey K. T., Hunter D. J. A prospective study of methylenetetrahydrofolate reductase and methionine synthase gene polymorphisms and risk of colorectal adenoma. Carcinogenesis (Lond.), 19: 2129-2132, 1998.[Abstract/Free Full Text]
63. Institute of Medicine . Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline, National Academy Press Washington 1998.

This article has been cited by other articles:

				T. J. Lightfoot, J. H. Barrett, T. Bishop, E. L. Northwood, G. Smith, M. J.V. Wilkie, R. J.C. Steele, F. A. Carey, T. J. Key, R. Wolf, et al. Methylene Tetrahydrofolate Reductase Genotype Modifies the Chemopreventive Effect of Folate in Colorectal Adenoma, but not Colorectal Cancer Cancer Epidemiol. Biomarkers Prev., September 1, 2008; 17(9): 2421 - 2430. [Abstract] [Full Text] [PDF]

				L. Rosenberg, D. Boggs, L. A. Wise, J. R. Palmer, M. H. Roltsch, K. H. Makambi, and L. L. Adams-Campbell A Follow-up Study of Physical Activity and Incidence of Colorectal Polyps in African-American Women. Cancer Epidemiol. Biomarkers Prev., August 1, 2006; 15(8): 1438 - 1442. [Abstract] [Full Text] [PDF]

				M. S. Cicek, N. L. Nock, L. Li, D. V. Conti, G. Casey, and J. S. Witte Relationship between Methylenetetrahydrofolate Reductase C677T and A1298C Genotypes and Haplotypes and Prostate Cancer Risk and Aggressiveness Cancer Epidemiol. Biomarkers Prev., August 1, 2004; 13(8): 1331 - 1336. [Abstract] [Full Text] [PDF]

				Y. Zhu, M. R. Spitz, C. I. Amos, J. Lin, M. B. Schabath, and X. Wu An Evolutionary Perspective on Single-Nucleotide Polymorphism Screening in Molecular Cancer Epidemiology Cancer Res., March 15, 2004; 64(6): 2251 - 2257. [Abstract] [Full Text] [PDF]

				L. Sharp and J. Little Polymorphisms in Genes Involved in Folate Metabolism and Colorectal Neoplasia: A HuGE Review Am. J. Epidemiol., March 1, 2004; 159(5): 423 - 443. [Abstract] [Full Text] [PDF]

				C. Sachse, G. Smith, M. J.V. Wilkie, J. H. Barrett, R. Waxman, F. Sullivan, D. Forman, D. T. Bishop, and C.R. Wolf A pharmacogenetic study to investigate the role of dietary carcinogens in the etiology of colorectal cancer Carcinogenesis, November 1, 2002; 23(11): 1839 - 1850. [Abstract] [Full Text] [PDF]

				S. Friso and S.-W. Choi Gene-Nutrient Interactions and DNA Methylation J. Nutr., August 1, 2002; 132(8): 2382S - 2387. [Abstract] [Full Text] [PDF]

				S. J. Weinstein, G. Gridley, L. C. Harty, S. R. Diehl, L. M. Brown, D. M. Winn, E. Bravo-Otero, and R. B. Hayes Folate Intake, Serum Homocysteine and Methylenetetrahydrofolate Reductase (MTHFR) C677T Genotype Are Not Associated with Oral Cancer Risk in Puerto Rico J. Nutr., April 1, 2002; 132(4): 762 - 767. [Abstract] [Full Text] [PDF]

				M. T. Goodman, K. McDuffie, B. Hernandez, L. R. Wilkens, C. C. Bertram, J. Killeen, L. Le Marchand, J. Selhub, S. Murphy, and T. A. Donlon Association of Methylenetetrahydrofolate Reductase Polymorphism C677T and Dietary Folate with the Risk of Cervical Dysplasia Cancer Epidemiol. Biomarkers Prev., December 1, 2001; 10(12): 1275 - 1280. [Abstract] [Full Text] [PDF]

				C. M. Ulrich, J. Bigler, J. A. Whitton, R. Bostick, L. Fosdick, and J. D. Potter Epoxide Hydrolase Tyr113His Polymorphism Is Associated with Elevated Risk of Colorectal Polyps in the Presence of Smoking and High Meat Intake Cancer Epidemiol. Biomarkers Prev., August 1, 2001; 10(8): 875 - 882. [Abstract] [Full Text] [PDF]

				H. Shen, M. R. Spitz, L.-E Wang, W. K. Hong, and Q. Wei Polymorphisms of Methylene-tetrahydrofolate Reductase and Risk of Lung Cancer: A Case-Control Study Cancer Epidemiol. Biomarkers Prev., April 1, 2001; 10(4): 397 - 401. [Abstract] [Full Text]

This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Ulrich, C. M. Articles by Potter, J. D. Search for Related Content PubMed PubMed Citation Articles by Ulrich, C. M. Articles by Potter, J. D.