1Alpha,25-dihydroxyvitamin D3 Induces de novo E-cadherin Expression in Triple-negative Breast Cancer Cells by CDH1-promoter Demethylation

Background: The triple-negative subgroup of breast cancer includes a cluster of tumors exhibiting low E-cadherin expression (metaplastic carcinomas). In several cancer models, 1alpha,25-dihydroxyvitamin D 3 (1α,25(OH) 2 D 3 ) induces differentiation by increasing E-cadherin expression. The Vitamin D receptor (VDR) was evaluated as a possible therapeutic target for metaplastic carcinomas and 1α,25(OH) 2 D 3 effects as a differentiating agent in triple- negative breast cancer cells were assessed. Materials and Methods: Metaplastic carcinomas were assessed for VDR expression by immunohistochemistry; differences in E-cadherin expression in triple-negative breast cancer cells were evaluated by real-time PCR, western blotting and Cadherin 1 (CDH1) methylation status. Results: Most of the metaplastic carcinomas were positive for VDR expression. Furthermore, 1α,25(OH) 2 D 3 promoted differentiation of MDA-MB-231 cells by inducing de novo E-cadherin expression, an effect that was time- and dose- dependent. Also, E-cadherin expression was due to promoter demethylation. Conclusion: Metaplastic carcinomas may respond to 1α,25(OH) 2 D 3 , since they express VDR and 1α,25(OH) 2 D 3 induces de novo E-cadherin expression in breast cancer cells by promoter demethylation. Breast cancer is a heterogeneous disease, comprised of diverse molecular subtypes associated with different biological behaviours and clinical outcomes (1, 2). Among all breast cancer subgroups, the triple-negative basal-like type is the most aggressive, presents poor patient outcome (2) and comprises a rare cluster of carcinomas entitled metaplastic tumors (3-5). Our group and others have demonstrated that metaplastic carcinomas are distinguished by high levels of expression of classical basal-like markers, such as cytokeratin (CK) 5/6, CK14, epidermal growth factor receptor (EGFR), vimentin and P-cadherin, as well as E- cadherin down-regulation (5-7). Furthermore, patients harbouring metaplastic tumors display a worse prognosis, exhibiting lower rates of disease-free survival than those with invasive ductal carcinomas (8, 9). Due to their triple-negative phenotype, metaplastic carcinomas do not have a directed therapy. Since radiation and chemotherapy remain the only options to treat these carcinomas, intensive research on alternative therapeutic strategies is mandatory.