Vitamin D is synthesized within skin followed by the peripheral maturation in liver and kidneys. Vitamin D is most essential secosteroid produced its systemic functions via complex with steroid/thyroid nuclear receptor called vitamin D receptor (VDR). The binding of the vitamin D3 to VDR causes conformational changes that permit VDR-RXR heterodimer formation and VDR/ SRC-1 (transcriptional co-activator proteins) interactions. Functional expression and nuclear activation of VDR is necessary to produce its effects upon binding with vitamin D response element (VDRE) on target gene where it causes transcriptional activation resulting in the prevention of breast cancer by inhibiting proliferation, impeding differentiation and stimulating pro-apoptosis. Season, latitude, pigmentation of skin, aging, sunscreen use, obesity, and smoking all affect the production of vitamin D. In case of vitamin D deficiency or VDR gene polymorphisms, vitamin D responses are altered and probably are involved in the risk of breast cancer. Since many epidemiological, observational and interventional studies have been done to illustrate the role of vitamin D and its receptor gene polymorphism in breast cancer development but controversial findings have been observed. Therefore, the role of vitamin D and its receptor gene polymorphisms in development of breast cancer are still a matter of discussion.
Part of the book: A Critical Evaluation of Vitamin D