Effect of vitamin D receptor polymorphisms on plasma oxidative stress and apoptotic biomarkers among breast cancer survivors supplemented vitamin D3.

We investigated whether plasma oxidative stress and apoptotic biomarkers were associated with the VDR polymorphisms in breast cancer survivors supplemented with vitamin D3. Two hundred fourteen breast cancer survivors received 4000 IU of vitamin D3 daily for 12 weeks. Linear regression was used to analyze whether the effect of vitamin D3 supplementation on response variables was associated with the selected VDR single nucleotide polymorphisms executing by 'association' function in the R package 'SNPassoc'. Linear regression analyses adjusted for age, BMI and on-study plasma 25(OH)D changes indicated that the aa genotype of the ApaI [codominant model (aa vs. AA): -0.21 (-0.39 to -0.03); recessive model (aa vs. AA and Aa): -0.20 (-0.37 to -0.03)] and bb genotypes of the BsmI [recessive model (bb vs. BB and Bb): -0.20 (-0.39 to -0.01)] on VDR were associated with greater decrease in plasma Bcl2. Our findings indicated that, the Ff genotype of FokI was accompanied by higher increase in plasma MDA levels [codominant model (Ff vs. FF): 0.64 (0.18-1.11); dominant model (ff and Ff vs. FF): 0.52 (0.09-0.05)]. This observed association was not remained statistically significant after correction for multiple testing. Haplotype score analyses revealed statistically significant association between the FokI BsmI ApaI haplotype and circulating MDA changes (P-value for global score = 0.001) after false-discovery rate correction. Our study suggests that genetic variations in the VDR do not powerfully modify the effects of vitamin D3 intake on biomarkers associated with antioxidant activity, oxidative stress and apoptosis in breast cancer survivors.