Figure 2
Effect of buthionine sulfoximine (BSO) plus estradiol on the growth of wild-type MCF-7 cells and antihormone-resistant MCF-7:2A cells. (a) MCF-7 cells were grown in estrogen-free media for 3 days prior to the start of the growth assay. On the day of the experiment, 30,000 cells were seeded in 24-well plates and after 24 h were treated with < 0.1% ethanol vehicle (control), 1 nM 17β-estradiol (E2), 100 μM BSO, or 100 μM BSO plus 1 nM E2 for 7 days. At the indicated time points, cells were harvested and total DNA (ng/well) was quantitated as described in Materials and methods. The data represent the mean of three independent experiments; bars, ± standard error of the mean (SEM). **, p < 0.001 compared with control cells. (b) MCF-7:2A cells were seeded at the same density as MCF-7 cells and were treated similarly. The data represent the mean of three independent experiments; bars, ± SEM. **, p < 0.001 compared with control cells; ##, p < 0.001 compared with estradiol-treated cells. (c) The effect of BSO plus estradiol on cell proliferation was also determined by cell counting using a hemocytometer. For experiment, 0.5 × 106 MCF-7 (top) and MCF-7:2A (bottom) cells were seeded in 15-cm dishes and after 24 h were treated with 1 nM estradiol, 100 μM BSO, or E2 plus BSO combination for 7 days. Data shown represents the mean of three independent experiments; bars, ± SEM. **, p < 0.001 compared with control cells; ##, p < 0.001 compared with estradiol-treated cells.