MAPK1 is important in 5-FU resistance in SGC7901/5-FU cells. (A) MAPK1 protein levels in the SGC7901/5-FU cells following treatment with MAPK1 siRNA or a scrambled siRNA. (B) SGC7901/5-FU cells were treated with various doses of 5-FU (0.5, 1.0 and 2.0 µmol/l) following 48 h of transfection. The cell growth inhibition rate was determined using an MTT assay. (C) Apoptosis detected by flow cytometry. SGC-7901/5-FU cells were untreated, transfected with miR-197 mimics or transfected with siRNA MAPK1 for 48 h, and apoptotic cells were detected by flow cytometry. Values are expressed as the mean ± standard deviation (n=3). *P<0.05 vs. control. MAPK1, mitogen-activated protein kinase 1; 5-FU, fluorouracil; SGC7901/5-FU, SGC7901 cells resistant to 5-FU; siR/siRNA, small interfering RNA; PI, propidium iodide.