Detection of apoptosis by TUNEL: graphical format. TUNEL staining was performed on cells as described above. Shown is a graphical representation of the staining shown in Fig. 9. $, P < 0.05 compared to normoxic mock transfected and HIF-1α siRNA; *, P < 0.05 compared to hypoxic HIF-1α siRNA and HIF-1α expression vector with HEPES; #, P < 0.05 compared to hypoxic HIF-1α expression vector with or without 2-DG. siRNA: A549 cells transfected HIF-1α siRNA vector, Mock: mock-transfected, HIF: A549 cells transfected with HIF-1α expression plasmid, HIF+2-DG: Cells transfected with HIF-1α expression plasmid and cultured with 2-DG, HIF+HEPES: Cells transfected with HIF-1α expression plasmid and cultured with medium containing HEPES.