Effect of hypoxia and/or etoposide on the transcription activity of 6 transcription factors, measured with a reporter assay. Cells were cotransfected with the corresponding reporter plasmid encoding the firefly luciferase and the pCMVβ normalization plasmid before being incubated 16 hours under normoxia (N) or hypoxia (H) in the presence or absence of etoposide (e) at 50 μM. Results are expressed as means of the ratio between firefly luciferase activity and the β-galactosidase activity ± 1 SD (n = 3). Results are expressed in induction levels by comparison with the reference condition, normoxia. *, **, *** : p < 0.05, p < 0.01, p < 0.001 vs. normoxia ; §§, §§§: p < 0.01, p < 0.001 vs. normoxia+etoposide.