P3155 specifically inhibits hypoxic induction of luciferase expression in U251-HRE but not in U251-pGL3. U251-HRE and U251-pGL3 were seeded in 96-well optiplates and incubated under normoxic or hypoxic conditions in the presence or absence of the indicated concentrations (μmol/L) of P3155. Cells were treated for 24 h and then tested for luciferase expression. Results are expressed as percentage inhibition of luciferase levels induced under hypoxic conditions (equal to 100%). Data presented as the average ± SE of three independent experiments.