Activation of reporter gene expression in HRCHO5 cells by hypoxia, transition metals, and iron chelation.

(A) Reporter gene construct used to generate the hypoxia-reporter cell line HRCHO5. TfHRE, hypoxia-response element derived from the transferrin 5′ enhancer12; SV40, simian virus 40 early promoter. (B) Luciferase activities in HRCHO5 cells following stimulation with CoCl₂, NiCl₂, and DFX for 18 hours under normoxic (20% oxygen) or hypoxic (1% oxygen) conditions. After preparation of cell extracts, determination of the luciferase activities, and normalization to the protein contents, the results were expressed as fold increases over the untreated normoxic controls. Means ± SD of 3 independent experiments.