By silencing OPN in MDA-MB-231 triple-negative breast cancer cell line (estrogen receptor (ER), progesterone receptor (PR) and receptor tyrosine-protein kinase erbB-2 (HER2) negative), a decrease in the production of hydroxyapatite crystals in an osteogenic medium and a decrease of cell migration were observed [135]. The gene discussed is ESR1; the disease is triple-negative breast carcinoma.