Expression profiling was obtained for a panel of breast cancer derived cell lines, including non-tumorigenic MCF10A (ATCC®: CRL-10317TM; ER−/PR−/AR−/HER2−) and MCF12A (ATCC®: CRL-10782TM; ER−/PR−/AR+/HER2−), estrogen-positive MCF-7 (ATCC® HTB-22TM; ER+/PR+/AR+/HER2−) and ZR-75-1 (ATCC® CRL-1500TM; ER+/PR+/AR+/HER2+), and estrogen-negative SK-BR-3 (ATCC® HTB-30TM; ER−/PR−/AR+/HER2+), MDA-MB-231 (ATCC® HTB-26TM; ER−/PR−/AR+/HER2−) and Hs578T (ATCC® HTB-126TM; ER−/PR−/AR+/HER2−). The gene discussed is ESR1; the disease is breast carcinoma.