3. MTT assay

MDA-MB-231 and HCC1937 cells were counted and seeded at a density of 1.6 × 10⁴ per well in 48-well plates. After 24 hours of incubation, the cells were treated with various concentrations of genistein (10, 25, 50, or 100 μM). Cell viability was measured at 72 hours. Thiazolyl blue tetrazolium bromide (Sigma-Aldrich, St. Louis, MO, USA) was added at a concentration of 0.5 mg/mL. After 3 hours of incubation, dimethyl sulfoxide was added to solubilize the formazan crystals formed. The absorbance was measured at 570 nm using a micro-plate reader (Bio-Rad Laboratories, Hercules, California, USA).