Stable expression of IGFBP-3 in MCF-7 breast cancer elicited resistance to the selective estrogen receptor degrader (SERD) fulvestrant (Ful), and MCF-7 cells with acquired resistance to Ful (MCF-7FulR) have higher IGFBP-3 expression than parental cells. This evidence concerns the gene ESR1 and breast carcinoma.