FIGURE 4.

PI3K/AKT pathway regulates HIF1α-induced transcription of target genes. A and B, serum-starved U87 and LN229-HRE-AP cells treated with 25 μm SF1126; 500 nm PF4691502, BEZ, and BKM120; and 100 nm GDC0941 and TGX221 were exposed to hypoxia for 24 h, followed by RNA isolation and real time PCR for VEGF, GLUT1, and PGK in U87 (A) and LN229-HRE-AP (B) cell lines. C, serum-starved LN229-HRE-AP cells treated with 25 μm SF1126 and 500 nm PF4691502, BEZ, and BKM120 for 30 min followed by IGF stimulation and then placed under normoxic (21% O₂) or hypoxic conditions (1% O₂) for 24 h. HRE-mediated AP activity was read at 405 nm using p-nitrophenyl phosphate as a substrate in the presence of different pan-PI3K inhibitors. D, LN229-HRE-AP cell lines transfected with 10 μg of Myr AKT or control plasmid were exposed to hypoxia (1% O₂) for 24 h followed by alkaline phosphatase activity read at 405 nm as described before. Graphs present means ± S.E. *, p < 0.05; **, p < 0.01; ***, p < 0.001 versus control (A–D) in hypoxic conditions as determined using pair wise two-sided Student's t test. Please note that the expression values of all genes (A–D) in hypoxic conditions are significant, compared with normoxic conditions. Abs, absorbance.