Fig. 3. PI3K signaling mediates specific expression of HIF-1 induced by EGF. PC-3 (A) and DU145 (B) cells were cultured in serum-free medium for 24 h. The PI3K inhibitors LY294002 and wortmannin were added at the indicated concentration 30 min before the addition of 20 ng/ml EGF. The cells were incubated in the presence (+) or absence (-) of EGF for 6 h. HIF-1 and HIF-1ß protein expression was analyzed as described above. The exposure times for immunoblots A and B were different, and the signals on these two blots are not comparable.