Cell Viability Assay with MTT and WST-1

Cell viability was determined by the MTT-based assay using Cell Proliferation Reagent WST-1 (Roche, Basel, Switzerland) according to the manufacturer’s instruction. Cells (5000 cells/well) were plated in 96-well culture plates, and various concentrations of (-)-gossypol or docetaxel were added to the cells in triplicates. Four days later, WST-1 was added to each well and incubated for 1.5 hours at 37°C. Absorbance was measured with a plate reader at 450 nm with correction at 650 nm. The results are expressed as the % of absorbance of treated wells versus that of vehicle control. IC₅₀, the drug concentration causing 50% growth inhibition, was calculated via sigmoid curve fitting using GraphPad Prism 5.0 (GraphPad, Inc.).