3. MTT assay

Cell viability was monitored by MTT assay. A2780, A2780/DDP, SKOV3, and SKOV3/DDP cells were seeded in 96-well plates 24 hours prior to treatment. Cells were then treated with different doses (0, 5, 10, 20, 40, and 80 μM) of cisplatin for 24 hours. A total of 20 μL MTT was added into each well and incubated for 4 hours at 37°C. One hundred fifty microliters of dimethyl sulfoxide was then added into each well to resolve MTT formazan crystals. Absorbance was measured at a wavelength of 490 nm using Model 680 micro-plate reader (Bio-Rad Laboratories, Hercules, CA).