To determine whether estrogen can modulate SELENBP1 expression in ER+ (MCF7 and T47D cells) and ER– (SKBR3 and MB453 cells) breast cancer cells, we treated the cells with 17β-estrodial (E2) in complete media containing charcoal-stripped FBS for different length of times. The gene discussed is ESR1; the disease is breast carcinoma.