IL-6 Impairs the Activity of Vitamin D3 in the Regulation of Epithelial-Mesenchymal Transition in Triple Negative Breast Cancer

Abstract

Objective: The present study aimed to investigate the possible role of IL-6 and 1α,25-dihydroxyvitamin D3 (1,25D)<br />signaling in epithelial-mesenchymal transition (EMT) and stemness in triple-negative breast cancer (TNBC) cell line.<br />Methods: TNBC cell line, HCC 1806, was treated with IL-6 and 1,25D for three and six days. Also, the role of vitamin<br />D receptor (VDR) was studied by transfection of TNBC cell line with VDR gene and transfection efficiency was assessed<br />using Human VDR enzyme-linked immunosorbent assay (ELISA). Changes in E-cadherin gene expression were<br />analyzed by quantitative real-time PCR (qRT-PCR). Also, changes in CD44+ cells were analyzed by flow cytometry.<br />Finally, morphological changes were investigated by light microscopy after 6 days. Results: Treatment of HCC1806<br />cells with IL-6 has no significant effect either on E-cadherin gene expression or CD44+ cells, (p > 0.05). However,<br />E-cadherin gene expression was significantly up-regulated after treatment with 1,25D for 6 days, (p < 0.05). Also, CD44+<br />cells were significantly reduced after treatment with 1,25D either for 3 or 6 days, (p < 0.05). Transfection of TNBC<br />cell line with VDR gene significantly up-regulated VDR protein expression, (p < 0.05). In addition, overexpression of<br />VDR in TNBC cells and treatment with 1,25D significantly up-regulated E-cadherin gene expression, (p < 0.05) and<br />reduced CD44+ cells, (p < 0.05). Moreover, transfection with VDR and treatment with a combination of 1,25D and<br />IL-6 significantly down-regulated E-cadherin gene expression and increased CD44+ cells compared with transfected<br />cells with VDR treated with 1,25D alone, (p < 0.05). No significant morphological changes were observed in treated<br />cells, 6 days post-treatment. Conclusion: The presence of IL-6 in the breast tumor microenvironment may impair the<br />activity of vitamin D3 signaling, limiting its anti-tumor effects in TNBC.