CircPVT1 is elevated in ERα-positive breast cancer and could promote resistance to endocrine therapy by sponging miR-181a-2-3p to stabilize the expression of ESR1 and promote the activity of estrogen/ERα target genes, while targeting circPVT1 could resensitize breast cancer cells to tamoxifen treatment [58]. This evidence concerns the gene ESR1 and breast cancer.