The up-regulation of Ndrg1 mRNA occurs by a HIF-1α-independent mechanism in cells deficient in the expression of the latter molecule. Wild-type (HIF-1α^+/+) and HIF-1α-knockout (KO; HIF-1α^-/-) murine embryo fibroblasts (MEFs) were incubated with either DFO (250 μM), 311 (25 μM), or hypoxia (0.5% O₂) for 8 hours at 37°C, and their RNA was extracted for the analysis of (A) Ndrg1, (B) HIF-1α, or (C) VEGF-1 by using semiquantitative RT-PCR (described in “Materials and methods”). Densitometry was performed, and gene expression was then calculated relative to the β-actin control. Results are a typical experiment from 3 performed.