FIGURE 5.

Hypoxic degradation of HIF1α by PTEN-PI3K pathway occurs via the 26 S proteosome. A and B, serum-starved (4 h) muristerone-induced U87 PTEN, G129E, or G129R cell lines (A) or GFAP V12 Ras PTEN^fl/fl and GFAP V12 Ras PTEN^fl/fl cre+ (B) cell lines were treated with the proteosome inhibitor 10 μm MG132 for 30 min before exposure to hypoxia (1% O₂) for 4 h, followed by nuclear extract and WCE preparation. C and D, serum-starved U87 and LN229-HRE-AP cell lines were treated with the proteosome inhibitor 10 μm MG132 for 5 min before being pulsed for 30 min with, the pan-PI3K inhibitors, 25 μm SF1126, and 500 nm PF4691502, followed by IGF stimulation and hypoxia for 4 h. Nuclear extracts were prepared for HIF1α Western blots as described before. E, serum-starved LN229-HRE-AP cell lines were treated with 10 μm MG132 (as indicated) for 5 min before being pulsed for 30 min with 100 nm GDC0941 and TGX221, followed by IGF stimulation and hypoxia for 4 h.