Characterization of Vitamin D Receptor Expression in Breast Cancer Cells Lines

Background/objectives: In recent years, preclinical and clinical studies suggested that optimal vitamin D status has a protective effect against development of breast cancer. Vitamin D exerts its activity by binding to the vitamin D receptor (VDR). In addition to steroid hormones receptors (eg estrogen and progesterone receptors), other nuclear receptors, such as VDR, are expressed in normal breast tissue and breast tumors. VDR expression can become a new prognosis biomarkers of breast cancer and the balance of vitamin D levels may improve patient prognosis and therapy efficiency. The goal of this research is the evaluation of VDR expression in circulating tumor cells (CTC) in breast cancers patients. For this, we present here an innovative triple fluorescence technique to screen the VDR status of epithelial tumor cells. Material & Methods: We developed the fluorescent immunostaining of each individual cell testing cytokeratin positivity (green) CD45 negativity (blue) and VDR status (red). We then tested the expression in 9 breast cancer cell lines, with various estrogen and progesterone receptors, HER2 and BrCa1 status. Results: The results clearly demonstrate various levels of VDR expression including low, average or high levels according to each cell line. Beside, it clearly appears that within one cell line, cells can express different levels of VDR. This technique allows now the analysis of CTC from blood samples of metastatic breast cancer patients, with an individual assessment for each single isolated tumor cell (CK positive and CD45 negative) and of VDR expressions. Conclusion: We will test CTC from metastatic breast cancer patients to explore if VDR expression relates to breast cancer subtypes classification (according to ER/PR/HER2), eventually as independant prognostic factor of breast cancer.