Figure 4

Effect of HIF-1α silencing on the protective role of hypoxia on the paclitaxel-induced apoptosis. 8 h post transfection with anti-HIF-1α siRNA (siRNA) or RISC-free control siRNA (RF) (50 nM, 24 h), MDA-MB-231 cells were incubated under normoxic (N) or hypoxic (H) conditions with or without paclitaxel (tax, 50 μM) or epirubicin (epi, 10 μM) for 16 hours. After transfection and incubation, the caspase 3 activity was assayed by measuring free AFC released from the cleavage of the caspase 3 specific substrate Ac-DEVD-AFC. Results are expressed in fluorescence intensity, as mean ± 1 SD (n = 3). Statistical analysis were determined independently for the 3 subgroups without siRNA, with anti-HIF-1α siRNA (siRNA) and with RISC-free control siRNA (RF) ; N.S. = non significantly different from control (N, N siRNA or N RF), * = significantly different from control (p < 0.05), *** = significantly different from control (p < 0.001); N.S. (1) = no significant difference between N epi and H epi, ### = significant difference between N tax and H tax (p < 0.001), # = significant difference between N epi and H epi (p < 0.05). N.S. = no significant difference between (2) N tax and N tax RF or (3) H tax and H tax RF, • = significant difference between H tax and H tax siRNA (p < 0.05), ••• = significant difference between N tax and N tax siRNA (p < 0.001).