Cell Counting Kit-8 (CCK-8) assay and determination of the half maximal inhibitory concentration (IC50) of DDP

Cell viability was analyzed using the CCK-8 assay (Beyotime Institute of Biotechnology) according to the manufacturer's protocol. For the determination of the IC₅₀ value of DDP, MGC803 and MGC803/DDP cells (3,000 cells/well) were seeded into 96-well plates and treated with a DDP concentration gradient of 0, 0.5, 1, 2, 4, 6, 8 and 10 µg/ml for 24 h. After cultivation in RPMI-1640 medium (Thermo Fisher Scientific, Inc.) with 10% FBS (cat. no. 26140079; Gibco; Thermo Fisher Scientific, Inc.) at 37°C in a humidified incubator with 5% CO₂ for 24 h, CCK-8 solution was added to each well and subsequently incubated at the same culture conditions for 3 h. The absorbance of each well at 450 nm (OD₄₅₀) was measured with a microplate reader, and SPSS software (version 18.0; SPSS Inc.) was used to calculate the IC₅₀ value. In order to assess the influence of DDP on cell viability, MGC803 and MGC803/DDP cells were treated with 2 µg/ml DDP for 24, 48 and 72 h, respectively, after which their viability was assessed using the aforementioned CCK-8 method.