Cell viability assay

To test the sensitivity of cells to cisplatin under various culture conditions, cells were plated in 96-well plates (5,000 cells/well) in medium containing 5% serum and incubated at 37°C under a 5% CO₂ atmosphere. After 24 h, the medium was replaced with medium containing the indicated concentration of cisplatin (Fujifilm Wako Chemical Corporation), and the cells were incubated for an additional 48 h. Cell viability was then assessed using a Cell Proliferation Kit II (XTT; Roche Diagnostics). Following the incubation period, 50 µl of XTT labeling mixture was added to each well, and the cells were incubated for 4 h, after which the absorbance at 492 nm was recorded using an ELISA plate reader.