Figure 4. Inhibition of HIF-1α expression by DNA damaging agents.

(A) Western blot showing the protein levels of HIF-1α, phosphorylated ERK 1/2 (P-MAPK) and ERK 1/2 (MAPK) in HCT116 cells treated with 1.25 µM U0126 and 0.4 µg/ml doxorubicin, and cultured at 20% or 5% O₂ for 2 days. Cells treated with 500 µM CoCl₂ for 16 hours were used as a positive control for the induction of HIF-1α (H). (B) Western blot showing the protein levels of HIF-1α in HCT116 and HCT116 p53^−/− in lysates collected 24 hours after treatment with 1 µg/ml Actinomicyn D (ActD) or 200 µM tert-Butyl Hydroperoxyde (tBH) for 2hours (C) Western blot showing the protein levels of HIF-1α, p53 and p21 in HCT116 and MCF-7 cells treated with 0.4 µg/ml doxorubicin or 10 Gy γ-radiation for 24 hours at 20% or <1% O₂ (hypoxia).