HIF-1α has no effect on the activation of MAPK at physiological oxygen tensions.

<p>(<b>A</b>) Western blot showing the protein levels of HIF-1α, p53, phosphorylated ERK 1/2 (P-MAPK) and ERK 1/2 (MAPK) in HCT116 cells transfected with 200 pmol of siRNA against HIF-1α and treated with doxorubicin (0.4 µg/ml). Control cells were transfected with a luciferase siRNA instead. Cells treated with 500 µM CoCl₂ for 16 hours were used as a positive control for the induction of HIF-1α (H). (<b>B</b>) Western blot showing the protein levels of HIF-1α, phosphorylated ERK 1/2 (P-MAPK) and ERK 1/2 (MAPK) in HCT116 treated with 40 µM YC-1 and/or 0.4 µg/ml doxorubicin and cultured at 20% or 5% O₂ for 24 hours. Cells treated with 500 µM CoCl₂ for 16 hours were used as a positive control for the induction of HIF-1α (H). (<b>C</b>) Representative FACS plots of HCT116 cells stained with PI. Cells were transfected with 50 pmol of siRNA against HIF-1α and treated with 0.4 µg/ml doxorubicin. Cells were cultured at 20% or 5% O₂ for 24 hours. Percentages indicate number of subG₁ events (dead cells).