ESR1 and neoplasm: For instance, down regulation of miR-27b-3p enhances TamR in breast cancer by increasing NR5A2 and CREB1 expression [27]; deep sequencing analysis of the breast cancer cell line MCF7 over-expressing miR-335-5p and miR-335-3p revealed that this miRNA duplex represses gene expressions of factors involved in the ERα signaling pathway; thus, enhancing TamR in MCF7 cells [28]; miR-29b-1 has tumor suppressor activity in TamR cells [29]; and miR-221/222 is involved in cell cycle deregulation in breast cancer drug resistance [30].