miRNA-148a regulates the expression of the estrogen receptor through DNMT1-mediated DNA methylation in breast cancer cells.

Breast cancer remains the most prevalent cancer among women worldwide. The expression of estrogen receptor-alpha (ER-alpha) is an important marker for prognosis. ER-alpha status may be positive or negative in breast cancer cells, although the cause of negative or positive status is not yet fully characterized. In the present study, the expression of ER-alpha and miRNA-148a was assessed in two breast cancer cell lines, HCC1937 and MCF7. An association between ER-alpha and miRNA-148a expression was identified. It was then demonstrated that DNA methyltransferase 1 (DNMT1) is a target of miRNA-148a, which may suppress the expression of ER-alpha via DNA methylation. Finally, an miRNA-148a mimic or inhibitor was transfected into MCF7 cells; the miRNA-148a mimic increased ER-alpha expression whereas the miRNA-148a inhibitor decreased ER-alpha expression. In conclusion, it was identified that miRNA-148a regulates ER-alpha expression through DNMT1-mediated DNA methylation in breast cancer cells. This may represent a potential miRNA-based strategy to modulate the expression of ER-alpha and provide a novel perspective for investigating the role of miRNAs in treating breast cancer.