Genetic polymorphisms in folate and alcohol metabolism and breast cancer risk: a case-control study in Thai women

Dietary folate as well as polymorphic variants in one-carbon metabolism genes may modulate risk of breast cancer through aberrant DNA methylation and altered nucleotide synthesis and repair. Alcohol is well recognized as a risk factor for breast cancer, and interactions with one-carbon metabolism has also been suggested. The purpose of this study is to test the hypothesis that genetic polymorphisms in the folate and alcohol metabolic pathway are associated with breast cancer risk. Twenty-seven single nucleotide polymorphisms (SNPs) in the MTR, MTRR, MTHFR, TYMS, ADH1C, ALDH2, GSTP1, NAT1, NAT2, CYP2E1 DRD2, DRD3, and SLC6A4 were genotyped. Five hundred and seventy patients with histopathogically confirmed breast cancer and 497 controls were included in the present study. Association of genotypes with breast cancer risk was evaluated using multivariate logistic regression to estimate odds ratios (OR) and their 95% confidence intervals (95% CI). Increased risk was observed for homozygotes at the MTR SNPs (rs1770449 and rs1050993) with the OR = 2.21 (95% CI 1.18-4.16) and OR = 2.24 (95% CI 1.19-4.22), respectively. A stratified analysis by menopausal status indicated the association between the NAT2 SNP (rs1799930) and breast cancer was mainly evident in premenopausal women (OR 2.70, 95% CI 1.20-6.07), while the MTRR SNP (rs162049) was significant in postmenopausal women (OR 1.61, 95% CI 1.07-2.44). Furthermore, SNPs of the genes that contribute to alcohol behavior, DRD3 (rs167770), DRD2 (rs10891556), and SLC6A4 (rs140701), were also associated with an increased risk of breast cancer. No gene-gene or gene-environment interactions were observed in this study. Our results suggest that genetic polymorphisms in folate and alcohol metabolic pathway influence the risk of breast cancer in Thai population.