Vitamin D-related gene polymorphisms, plasma 25-hydroxyvitamin D, and breast cancer risk

PURPOSE: Studies of vitamin D pathway genetic variants in relation to cancer risk have been inconsistent. We examined associations between vitamin D-related genetic polymorphisms, plasma 25-hydroxyvitamin D [25(OH)D], and breast cancer risk. METHODS: In a population-based case-control study of 967 incident breast cancer cases and 993 controls, we genotyped 25 polymorphisms encoding the vitamin D receptor (VDR) gene, 1α-hydroxylase (CYP27B1), 24-hydroxylase (CYP24A1), and vitamin D binding protein (GC) and measured plasma 25(OH)D. We used multivariable logistic regression to estimate adjusted odds ratios (ORs) and 95% confidence intervals (CI). RESULTS: Among CYP24A1 polymorphisms, rs6068816 was associated with a 72% reduction in breast cancer risk (TT vs. CC, OR: 0.28, 95%CI: 0.10–0.76; p(trend)=0.01), but for rs13038432, the 46% decrease included the null value (GG vs. AA, OR: 0.54, 95%CI: 0.17–1.67; p(trend)=0.03). Increased risk that included the null value was noted for CYP24A1 rs3787557 (CC vs. TT, OR: 1.34, 95% CI: 0.92–1.89). The VDR polymorphism, TaqI (rs731236), was associated with a 26% risk reduction (TT vs. CC, OR: 0.74, 95%CI: 0.56–0.98; p(trend)=0.01). For other polymorphisms, ORs were weak and included the null value. The inverse association for plasma 25(OH)D with breast cancer was more pronounced (OR: 0.43, 95%CI: 0.27–0.68) among women with the common allele for CYP24A, rs927650 (p for interaction on a multiplicative scale=0.01). CONCLUSION: Breast cancer risk may be associated with specific vitamin D-related polymorphisms, particularly CYP24A1. Genetic variation in the vitamin D pathway should be considered when designing potential intervention strategies with vitamin D supplementation