Vitamin D is involved in mineral and bone homeostasis, immune responses, anti-inflammation, anti-infection, and cancer prevention. Vitamin D deficiency is a critical factor in the pathology of at least 17 varieties of cancer, as well as autoimmune diseases, diabetes, osteoarthritis, periodontal disease, and more. Vitamin D receptor (VDR) is a nuclear receptor (Nuclear, Class 1, Thyroid Hormone Receptor-like) that mediates most biological functions of 1,25(OH)2D3 or vitamin D3, the active form of vitamin D. VDR is highly expressed in metabolic tissues, such as intestine, kidney, skin, and thyroid gland, and moderately expressed in nearly all tissues. Activation of VDR signaling affects many processes, including calcium metabolism, apoptosis, immunity, and autophagy. Upon activation, the VDR binds to vitamin D response elements (VDREs) located in promoter regions of target genes, thereby controlling the transcription of at least 913 genes in human SCC25 cells[1].