Effect of HIF-1 expression on COX-2 transcriptional activation. PC-3 prostate cancer cells were seeded into 6 well plates a day before the transfection. a) To determine whether HIF-1 activity is required for COX-2 transcriptional activation, the cells were co-transfected with COX-2 promoter luciferase reporter (PXP4/COX-2), pCMV-β-gal, and pcDNA3 vector or pcDNA3-HIF-1 dominant negative plasmid. b) To determine whether HIF-1 expression is sufficient to induce COX-2 transcriptional activation, the cells were co-transfected with the COX-2 promoter reporter, pCMV-β-gal, and pcDNA3 vector or pcDNA3-HIF-1α wild type expression plasmid. The cells were cultured for 36 h after transfection. The relative luciferase activity was determined by the ratio of luciferase/β-gal activity, and normalized to the vector control (100%). *Indicates the significant difference when the value is compared to the control (p < 0.01).