4.8. Viability Assay for Drug Resistance

Cells (1 × 10⁴) were seeded in 96-well plates and cultured in full growth medium overnight. Then, the medium was removed and replaced with 200 µL complete medium containing cisplatin 30 µM or 5-fluorouracil 80 µM. The plates were incubated at 37 °C, 5% CO₂ for 72 h. After the treatment, cells were incubated with 20 µL of MTS reagent (CellTiter 96 AQueous One Solution Cell Proliferation Assay, Promega, Fitchburg, WI, USA) for 3 h at 37 °C. Then, the spectrophotometric absorbance of the samples was detected by using a Biotek Epoch plate reader (Agilent Technologies) at 490 nm.