MELK is associated with resistance of gastric cancer cells to 5-FU. A and B, Effect of 5-FU on MELK expression level (**P < 0.01). NCI-N87 and SGC7901 cells were treated with 0, 1, 2, 4, 8, 16 μg/ml of 5-FU, and MELK expression was examined by qPCR and Western blotting 48 h later. C and D, qPCR and immunoblotting analysis of the efficacy of MELK knockdown and overexpression (**P < 0.01). pGPU6/GFP/Neo was used for shRNA plasmid construction. Plasmids were transfected into gastric cancer cells using Lipofectamine 2000. MELK cDNA ORF was cloned into pL/ERES/GFP plasmid for lentivirus production. E and F, Effect of MELK knockdown and overexpression on apoptosis induced by 5-FU. Cells were treated with 0, 2, 4, 8 μg/ml of 5-FU, apoptosis was examined by flow cytometry (*P < 0.05, **P < 0.01).