Furthermore, Boudot and his colleagues found that in estrogen receptor (ER) positive breast cancer, estradiol can promote the growth of ER positive breast cancer cells by producing a large number of CXCL12 and regulating CXCR4 and CXCR7 receptors of CXCL12, and the chemokine receptor CXCR4 can enhance the response of cells to estradiol.30 This evidence concerns the gene CXCR4 and breast cancer.