ESR1 and breast cancer: Herein we address several important questions: i) what is(are) the change(s) of miR-196a expression upon estrogen treatment in BC cells; ii) what is underlying mechanism of the estrogen-regulated miR-196a expression in ER+ BC cells; iii) what is/are functional target(s) of the miRNA-196a that may be associated with estrogen-induced BC progression.