Figure 4
HIF-1α is involved in apoptotic resistant phenotype in the mAb-long cells and VEGF-KO cells. (A, B) Expression levels of HIF-1α mRNA in the mAb-long cells or VEGF-KO cells. Cells were untransfected (none) or transfected with control siRNA (si-control) or HIF-1α-targeting siRNA (si-HIF-1α) in HCT116 (A) or RKO cells (B), then they were exposed to hypoxia (~0.1% O2) for 36 h (n=6, means ± S.D.). *P < 0.01., compared with the respective untransfected cells (none) between IgG- and mAb-cells, or between parental and VEGF-KO cells. # P < 0.01., compared with the respective untransfected cells (none) in each group. (C, D) Transcriptional activity of HIF-1α under hypoxic conditions in the mAb-long cells or VEGF-KO cells. Cells were transfected with a HIF-1α-dependent reporter (LucF) construct and a internal control reporter (LucR), then they were exposed to hypoxia (~0.1% O2) for 36 h in HCT116 (C) or RKO cells (D). The transcriptional activity of HIF-1α was determined by a dual luciferase assay (n=5, means ± S.D.). *P < 0.01., # P < 0.05. (E, F) The levels of hypoxia-induced apoptosis in the mAb-long cells or VEGF-KO cells. Cells were untransfected (none) or transfected with si-control or si-HIF-1α in HCT116 (E) or RKO cells (F), then they were exposed to hypoxia (~0.1% O2) for 3 days. Apoptotic cells were measured by TUNEL assay (n=6, means ± S.D.). *P < 0.01., # P < 0.05.