Hypoxia upregulates POX expression in vitro. POX promoter activity (A) and mRNA expression (B) were measured in various cancer cells as indicated after 24 hrs of hypoxia (0.05% O2) treatment. The results represent the fold change in relative luciferase activity and POX mRNA levels of cells exposed to hypoxia over those exposed to normoxia. C, oxygen concentration- and time-dependent response of POX mRNA expression in HT29 colorectal cancer cells. D, time-dependent effect of 0.05% O2 on POX protein expression in HT29 cells. E, the effect of hypoxia and/or low-glucose (1mM) on POX mRNA expression in HT29 cells. F, POX protein expression in HT29 cells exposed to hypoxia (Hy) and/or low-glucose (LG) (1mM) for 24 hrs. *, P <0.05, **, P <0.001 compared with normoxic control (Ctr).