Antiproliferative effect of metformin was associated with oxidative stress and apoptosis.

<p>(<b>A–C</b>) MCF-7 cells were treated with metformin (10 mM) for 48 and 72 hours and ROS was determined by the CM-H₂DCFDA assay, and measured by flow cytometry. (<b>D</b>) MCF-7 cells were treated with metformin (10 mM) for 48 hours, and then treated with H₂O₂, (1 mM) for an additional 4 hours and cell viability was analyzed. (<b>E</b>) Production of H₂O₂ by MCF-7 cells after treatment with metformin for 24 hours (10 mM) or metformin (10 mM) + catalase (20 µg mL⁻¹). * p<0.05 vs. control; *** p<0.0001 vs. control; ^# p<0.001 vs. H₂O₂ and ^& p<0.0001 vs. metformin.