MCF-7 cells were treated with 5 μM of each of the agents alone and/or in the presence of 10 nM estradiol, and cell viability was measured as described in the experimental section. Estradiol (E2), 4-hydroxytamoxifen (4OHT), and genistein (Gen) were used as controls. The results were normalized against a control treatment with vehicle (DMSO). *, P < 0.0001 vs. control by unpaired t test, n = 6.