CQ enhanced the cytotoxicity of 5-FU through inhibiting autophagy. (A) The contribution of autophagy to SGC-996 and GBC-SD cells after treatment with 5-FU was examined by ATG5 and ATG7 with siRNA. The mRNA expression of each gene were significantly reduced by siRNA treatment (upper), in parallel with the protein levels after the transfection (lower). GAPDH was used as a loading control. (B) GBC cells transiently transfected with negative control siRNA, Atg-5 or Atg-7 siRNA were treated with 5 μM 5-FU for 48 hours. Cell proliferation and mortality rates were measured by CCk-8 assay and the trypan blue exclusion staining (*,p < 0.05 vs. control, n = 3).