Figure 6.

PDK3 mediates HIF-1α–induced drug resistance in colon cancer cells. A: Colo320DM cells were cultured under normoxic (Nor) or hypoxic (Hypo) condition with different doses of cisplatin, paclitaxel, or oxaliplatin as indicated for 24 hours. Cell numbers were determined by crystal violet staining. Data show means and SEM of three independent experiments. *P < 0.05; **P < 0.01; ***P < 0.001. B: HCT116 and HT29 cells were cultured under normoxic (Nor) or hypoxic (Hypo) condition and treated with different doses of oxaliplatin for 24 hours as described in panel A. *P < 0.05, **P < 0.01. C: Representative Western blot shows the knockdown effect of siRNA against PDK3. Levels of PDK1 and β-actin were also detected to demonstrate the specificity of siRNA. sr: GC content–matched scramble siRNA. hypoxia, H; N, normoxia. D and E: Colo320DM cells were transiently transfected with siPDK3 or GC content–matched scramble siRNA (Sr) and followed by treatment with 40 μmol/L cisplatin, 0.4 μmol/L paclitaxel, or 40 μg/mL oxaliplatin under normoxic or hypoxic condition for 24 hours. Representative figures of TUNEL assay results were shown in panel D and the percentages of apoptotic cells in each treatment were shown in panel E. *P < 0.05 compared to normoxia, scramble RNAi, and vehicle-treated groups; ^†P < 0.05 compared to normoxia, scramble RNAi, and drug-treated groups; ^‡P < 0.05 compared to hypoxia, scramble RNAi, and drug-treated groups.