Vitamin D Status and Breast Cancer Risk

Abstract

Background: Local synthesis of 1α,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 the odds ratio for breast cancer compared with 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 1αOHase were decreased at confluence in the cell lines. Conclusion: Impaired local generation of 1,25OHD₃ may contribute to the development of breast cancer.