ESR1 and breast cancer: Furthermore, studies comparing miRNA profiles in breast cancer with different ER/progesterone (PR)/HER2 levels showed that specific miRNA expression levels could be correlated to different ER/PR status (miR-142-5p, miR-200a, miR-205 and miR-25) and HER2 status (let-7f, let-7g, miR-107, miR-10b, miR-126, miR-154 and miR-195) [14].