IC50 determination

Cell viability was determined by the using of the CellTieter-Glo luminescent cell viability assay (#7570, Promega) according to the manufacturer’s instructions. In brief, AGS cells were grown in 96-well plates and then treated with 5-FU at serial concentrations of 0, 0.5, 1, 5, 10, 50, 100, 200 and 500 ug/ml for 48 h. After 48-h treatment, the cells were incubated with CellTiter-Glo reagent for 10 min at room temperature. The luminescence value was measured using luminometer. The 50% inhibitory concentration (IC50) for 5-FU, which is defined as the 5-FU concentration which causes a 50% reduction in luminescence relative to the untreated control, is determined directly from semilogarithmic dose–response curves.