Research article
MTHFR C677T and postmenopausal breast cancer risk by intakes of one-carbon metabolism nutrients: a nested case-control study
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* Corresponding author: Sonia S Maruti ssmaruti@gmail.com
1 Public Health Sciences Division, Fred Hutchinson Cancer Research Center, Seattle, WA, 98109-1024 USA
2 Department of Epidemiology, University of Washington, Seattle, WA, 98195 USA
3 Biometrics, Hoffmann-La Roche, Inc., 340 Kingsland Street, Nutley, NJ 07110-1199, USA
4 Research & Development, InterGenetics Incorporated, 655 Research Parkway, Suite 300, Oklahoma City, OK 73104, USA
Breast Cancer Research 2009, 11:R91 doi:10.1186/bcr2462
Published: 23 December 2009Abstract
Introduction
The C677T polymorphism of the methylenetetrahydrofolate reductase (MTHFR) gene has been hypothesized to increase breast cancer risk. However, results have been inconsistent, and few studies have reported the association by menopausal status or by intakes of nutrients participating in one-carbon metabolism. Our aims were to investigate whether MTHFR C677T was associated with postmenopausal breast cancer risk and whether this relation was modified by intakes of folate, methionine, vitamins B2, B6, and B12, and alcohol.
Methods
We studied 318 incident breast cancer cases and 647 age- and race-matched controls participating in a nested case-control study of postmenopausal women within the VITamins And Lifestyle (VITAL) cohort. Genotyping was conducted for MTHFR C677T and dietary and supplemental intakes were ascertained from a validated questionnaire. Adjusted odds ratios (OR) and 95% confidence intervals (CI) were calculated using unconditional logistic regression.
Results
We observed a 62% increased risk of breast cancer among postmenopausal women with the TT genotype (OR = 1.62; 95% CI: 1.05 to 2.48). Women with a higher number of variant T alleles had higher risk of breast cancer (P for trend = 0.04). Evidence of effect-modification by intakes of some B vitamins was observed. The most pronounced MTHFR-breast cancer risks were observed among women with the lowest intakes of dietary folate (P for interaction = 0.02) and total (diet plus supplemental) vitamin B6 (P for interaction = 0.01), with no significant increased risks among women with higher intakes.
Conclusions
This study provides support that the MTHFR 677TT genotype is associated with a moderate increase in risk of postmenopausal breast cancer and that this risk may be attenuated with high intakes of some one-carbon associated nutrients.