Vitamin D status and breast cancer risk.

Background: Local synthesis of 1·,25(OH)D3 in breast tissue may contribute to maintenance of normal cell function and could be impaired with low circulating levels of the precursor 25hydroxyvitamin D. The aims of this study were to: i) assess the association between breast cancer risk and plasma 25OHD3 concentration and ii) define the significance of expression of the 25OHD activating enzyme CYP27b1 in non-malignant and malignant models of breast epithelial cells. Materials and Methods: Breast cancer patients and control women were recruited and their 25OHD levels measured by enzyme-linked immunosorbent assay (ELISA). MRNA expression of CYP271b and the 1,25(OH)2D3 inactivating enzyme CYP24 were measured in breast cancer cell lines by RT-PCR and correlated with immunoblotting approaches to the translated proteins. Results: For women with 25OHD 50 nM was 3.54 (CI 1.89-6.61, p<0.001). CYP271b and CYP24 were detected in non-malignant and malignant cell models. Protein levels of 24OHase but not 1·OHase were decreased at confluence in the cell lines. Conclusion: Impaired local generation of 1,25OHD3 may contribute to the