To determine antiestrogen sensitivity in parental ER+ MCF7 and T47D breast cancer cells and their respective LTED variants, MCF7-LTED and T47D-LTED cells, we measured cell proliferation over 6-days (media with respective treatment was replenished 72 h) with vehicle alone or increasing concentrations of 17beta-estradiol (E2), fulvestrant or tamoxifen (4-hydroxytamoxifen) (Figures 1A–F). The gene discussed is ESR1; the disease is breast cancer.