Effect of PEG-SOD and PEG-catalase on 2DG toxicity in FaDu cells. Cells were treated with 18 μmol/L PEG, 100 units/mL PEG-SOD, 100 units/mL PEG-catalase (PEG-CAT), or 50 units/mL PEG-SOD + 50 units/mL PEG-catalase for 1 h before and during treatment with 20 mmol/L 2DG for 24 h. Clonogenic cell survival data were normalized to control. Columns, mean of N = 3 experiments done on different days with at least four cloning dishes taken from one treatment dish; bars, SD. *, P < 0.01, versus control; ¥, P < 0.01, versus 2DG.