To test whether E2 inhibits miR-124 expression through the function of ER, the ER-positive and ER-negative BC cells MCF7 and MDA-MB-231 were treated with E2 or Eth at different time points and the results showed that miR-124 expression was downregulated at 6, 12 and 24 h post E2 treatment in MCF7 cells (Figure 1B), but not in MDA-MB-231 cells (Figure 1C), suggesting that ER is necessary for E2 to inhibit miR-124 expression. The gene discussed is ESR1; the disease is breast cancer.