Figure 1.

A. HRE-bla ME-180 cells express β-lactamase in response to hypoxia. Cells were incubated with indicated amount of DFO or CoCl₂ for 17 hrs before β-lactamase assay was performed. B. HIF1α, but not HIF2 α, mediates the expression of β-lactamase in response to hypoxia. Cells were incubated with indicated Stealth RNAi™ duplexes for 55 hrs, and then treated with 125 μM CoCl₂ for 17 hrs before β-lactamase assay was performed. C. Western blot analysis for DFO-induced HIFα accumulation and RNAi knockdown. Cells were incubated with indicated Stealth RNAi™ duplexes for 55 hrs, and then treated with 250 μM DFO for 5 hrs before HIF1α western blot was performed as described in Materials and Methods.