Vitamin D receptor polymorphisms and cancer.
It was suggested that vitamin D levels influence cancer development. The vitamin D receptor (VDR) is a crucial mediator for the cellular effects of vitamin D. In fact It has been hypothesized that polymorphisms in the VDR gene affect cancer risk and the relevance of VDR gene restriction fragment length polymorphisms for various types of cancer has been investigated by a great number of studies. However, results from previous studies on the association of VDR polymorphisms with different cancer types are somewhat contradictory, and the role of VDR in the etiology of cancer is still equivocal. We have performed a systematic review of the literature to analyze the relevance of more VDR polymorphisms (Fok1, Bsm1, Taq1, Apa1, and Cdx2) for individual malignancies, including cancer of the skin (melanoma and nonmelanoma skin cancer), ovarian cancer, renal cell carcinoma, bladder cancer, non-Hodgkin lymphoma, leukemia, thyroid carcinoma, esophageal adenocarcinoma, hepatocellular carcinoma, sarcoma, head and neck and oral squamous cell carcinoma. Up to June 2012, we identified 79 independent studies for a total of 52427 cases and 62225 controls. Significant associations with VDR polymorphisms have been reported for prostate (Fok1, Bsm1, Taq1), breast (Fok1, Bsm1, Apa1), colon-rectum (Fok1, Bsm1, Taq1) and skin cancer (Fok1, Bsm1, Taq1). Very few studies reported risk estimates for the other cancer sites. Conflicting data have been reported for most malignancies and at present it is still not possible to make any definitive statements about the importance of the VDR genotype for cancer risk. It seems probable that interactions with other factors such as calcium and vitamin D intake, 25(OH)D plasma levels and UV radiation exposure play a decisive role in cancer risk. To conclude, there is some indication that VDR polymorphisms may modulate the risk of some cancer sites and in future studies VDR genetic variation should be integrated also with prediagnostic indicator of vitamin D status.