Quercetin exerts apoptotic effects on MCF-7 breast cancer cells. MCF-7 cells were treated with quercetin (25, 50, 100, 200, or 400 µM) for 6 h, and the cell viability was determined by MTT assay as described in Methods. Data are expressed as the percent relative to control (A). Cells were treated with quercetin (50, 100 or 200 µM) for 24 h, and harvested cells were fixed with 70% ethanol, and stained with 10 µg/ml propidium iodide. The cell cycle was then examined using flowcytometry (B). Cells were exposed to quercetin (25, 50, 100 or 200 µM) for 24 h, total RNA was extracted with Tri-Zol reagent, and RT-PCR was performed using specific primers for p-53, p-21, VEGF, and β-actin (C). Cells were treated with 100 µM quercetin for 12 h, and stained with 10 µM Hoechst33342 dye for 30 min, and chromatin condensation representing apoptotic cell death was examined using fluorescence microscope (D).