Figure 6.

Effects of HIF-1α siRNA on PGE₂-induced COX-2 expression in high density cultured HCA-7 cells. Cells were cultured at low (L; 3 × 10⁴ cells/each 6 well), middle (M; 1 × 10⁵ cells/each 6 well), and high (H; 3 × 10⁵ cells/each 6 well) densities. Cells were transfected with HIF-1α siRNA for 48 h, treated with either vehicle or 1 μmol/L PGE₂ for 6 h at 37°C, and then subjected to immunoblot analysis with an antibody against COX-2, as described in the Materials and Methods. The blots were stripped and re-probed with an antibody against β-tubulin. The bar graphs represent the ratio of COX-2 to β-tubulin as assessed with pooled densitometric data (mean ± SD) from more than three independent experiments. Data were normalized to the ratio of COX-2 to β-tubulin of PGE₂-treated controls at the low cellular density (c) as 100%. *P < 0.05, t-test, significantly different from d (without HIF-1α siRNA at the middle cellular density) to g (with siRNA at the middle cellular density) and/or e (without HIF-1α siRNA at the high cellular density) to h (with siRNA at the high cellular density), respectively.