Fig. 1
Effect of mTOR overexpression and Evr treatment on the Warburg effect in GEMsen and GEMres cells. The transfection efficiency of mTOR overexpression (ov-mTOR) vectors was evaluated by measuring a the relative mRNA expression of mTOR and b the percentage of positive fluorescence signal (transfected cells) in GEMsen and GEMres cells. The transfection efficiency was determined to be approximately 37%. c Effect of ov-mTOR on the viability of GEMsen and GEMres cells, with or without Evr treatment. d Glucose uptake, e ATP production, and f lactic acid generation in GEMsen and GEMres cells with or without ov-mTOR transfection or/and Evr treatment. mTOR overexpression promoted glucose uptake, ATP production, and lactic acid generation in both cell types, but its effect appeared to be less pronounced in GEMres cells than that in GEMsen cells. g Western blot of proteins associated with the Warburg effect. Quantification of the protein expression of h GLUT1, i LDHB, j HK2, and k PKM2 in GEMsen and GEMres cells with or without ov-mTOR transfection or/and Evr treatment, normalized to that of GAPDH as an internal control. From h to k, the numbers in the arrows represent the difference (increase or decrease) in protein expression between ov-mTOR and ov-mTOR + Evr. In ov-mTOR-transfected GEMres cells, the suppressive effect of Evr on the expression of GLUT1 and LDHB was weaker than that in ov-mTOR-transfected GEMsen cells. Conversely, the suppressive effect of Evr on the expression of HK2 and PKM2 was stronger in ov-mTOR-transfected GEMres cells than that in ov-mTOR-transfected GEMsen cells. The data are expressed as the mean ± standard deviation of three replicates (n = 3). *P < 0.05; #P < 0.05 compared with the same treatment in GEMsen cells. GEM: gemcitabine, Evr: everolimus; EV: empty vector (negative control); GEMsen: GEM-sensitive pancreatic cancer cells; GEMres: GEM-resistant pancreatic cancer cells; au: arbitrary units