Figure 3
Buthionine sulfoximine (BSO) plus estradiol induce apoptosis in MCF-7:2A cells. (a) Terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL) staining for apoptosis in MCF-7:2A cells following BSO plus 17β-estradiol (E2) treatment for 96 h were performed as described in Materials and methods. Slides were photographed through a brightfield microscope under 100 × magnification. TUNEL-positive cells were stained black (white arrows). Columns (right), mean percentage of apoptotic cells (annexin V-positive cells) from three independent experiments performed in triplicate; bars, ± standard error of the mean (SEM). *, p < 0.001 compared with control cells; #, p < 0.001 compared with estradiol-treated cells. (b) Annexin V staining for apoptosis. Cells were seeded in 100 mm plates at a density of 1 × 106 per plate and after 24 h were treated with ethanol vehicle (control), 1 nM E2, or BSO plus E2 for 72 h and then stained with fluorescein isothiocyanate (FITC)-annexin V and propidium iodide (PI) and analyzed by flow cytometry. PI was used as a cell viability marker. Representative cytograms are shown for each group. Quantitation of apoptosis (percentage of control) in the different treatment groups is shown on the right. bars, ± SEM. *, p < 0.05 compared with control cells; #, p < 0.01 compared with estradiol-treated cells.