The role of HIF-1 in the regulation of NDRG1 gene expression. A) HIF-1 proficient (HIF-1α+/+) and deficient (HIF-1α-/-) cells were exposed to 0.5 mM NiCl2, 300 μM CoCl2, and hypoxia (0.5% O2) for 20 hrs. 15 μg of total RNA was isolated and subjected to a Northern blot analysis using NDRG1 probe (top panel). Ethidium bromide staining was used to adjust loading (bottom panel). B) HIF-1α+/+ and HIF-1α-/- cells were exposed to 0.5 mM NiCl2, 300 μM CoCl2, and hypoxia (0.5% O2) for 20 hrs. 40 μg of protein extracts were subjected to Western blot analysis using antibody against Ndrg1 protein (top panel). Actin bands in the bottom panel show loading. C) Cells were first incubated for 24 hours under normoxic conditions for attachment (Day 0) and then exposed to hypoxia for up to three days. Western blot analysis with antibody against Ndrg1 was carried out in 25 μg of whole cell protein extracts (top panel). Actin bands in the bottom panel show loading.