Through miRDB prediction and WIKIPathway enrichment analysis, four ESR1-targeting miRNAs were enriched in breast cancer pathway (hsa-miR-22, -181a, −152), DNA damage response (has-miR-152, 148a) and PI3K-Akt signaling pathway (has-miR-152), with hsa-miR-22, -181a and -148a upregulated and hsa-miR-152 downregulated in breast cancer. The gene discussed is PIK3CA; the disease is breast cancer.