VDR

Abstract

Vitamin D is a steroid hormone which binds to the vitamin D receptor (VDR) and has been implicated in carcinogenesis. Pre-clinical data on the VDR demonstrates a direct correlation between the vitamin and cell growth, differentiation, and apoptosis. Through nuclear transcription as well as cytoplasmic pathway induction, binding of the active form of vitamin D, calcitriol, to the VDR has been shown to mechanistically affect multiple carcinogenic cell lines. Mouse models have been further utilized to demonstrate the in vivo effects of calcitriol and the VDR on tumorogenesis. While pre-clinical data supporting the potential of calcitriol as a cancer therapeutic agent abounds, evidence from clinical trials remains sparse. Most studies thus far do not clearly demonstrate a correlation between intermittent doses of calcitriol and decreased rates of development or recurrence of malignancy. However, few large clinical trials have been performed, and some of the smaller studies that have been done demonstrate decreases in cancer markers, fewer rates of progression, and rarely complete remissions. The inconsistent results suggest that our understanding of the potential anti-tumor effects of vitamin D is limited, and further clinical investigation is necessary.