Association between Vitamin D receptor (Cdx2, Fok1, Bsm1, Apa1, Bgl1, Taq1, and Poly (A)) gene polymorphism and breast cancer: A systematic review and meta-analysis

The purpose of this systemic review and meta-analysis was to examine the relationship between VDR gene polymorphisms and breast cancer. Literature was searched through PubMed database, Google scholar, and the web of knowledge from December 2015 to January 2017 and consists of 34 studies (26,372 cases and 32,883 controls). All statistical measures were done using STATA version 11.2. The heterogeneity among studies was tested using I2 statistics. Mantel–Haenszel method and DerSimonian–Laird method were used to combine data from studies using both random-effect model and fixed-effect model, respectively. Potential publication bias was evaluated by Egger’s test. Sensitivity analysis was also performed to evaluate the quality and consistency in results. The results of this meta-analysis revealed that VDR gene polymorphisms (Bsm1 bb vs BB; SOR = 1.18, 95% CI = 1.054–1.322, Apa1 aa vs AA; SOR = 1.18, 95% CI = 0.87–1.59, Poly (A) LL vs SS; SOR = 1.41, 95% CI = 1.06–1.88, Fok1 ff + Ff vs FF; SOR = 1.25, 95% CI = 0.896–1.759, Apa1 aa+Aa vs AA; SOR = 1.13, 95% CI = 0.95–1.35, Poly (A) LL + LS vs SS; SOR = 1.19, 95% CI = 1.00–1.43, Poly (A) L vs S; SOR = 1.18, 95% CI = 1.03–1.35) are associated with the breast cancer. Cdx2, Bgl1, and Taq1 do not show association with breast cancer. Thus, the finding of this meta-analysis concluded that VDR Bsm1, Apa1, Fok1, and Poly (A) gene polymorphisms may be susceptible for breast cancer development.