Figure 3.

Stimulation of AKT phosphorylation by dmPGE₂ is dependent on src activity and transactivation of the EGFR. (A) Treatment of HCT-116 cells with dmPGE₂ results in phosphorylation of the EGFR at Tyr 1068. EGFR expression and phospho-EGFR (P-EGFR; Tyr 1068) expression in cell lysates treated for the indicated times with 1 μM dmPGE₂ were determined by Western analysis using specific antibodies. Upper panel: Phospho-EGFR expression corrected to total EGFR expression. Lower panel: Representative Western blot. Data are representative of 3 separate experiments. (B) Inhibition of src or EGFR kinase activity inhibits phosphorylation of AKT in response to dmPGE₂. HCT-116 cells were pretreated 1 hour with either 10 μM PP2 (src inhibitor) or 1 μM PD153035 (EGFR kinase inhibitor) and then irradiated at 6 Gy in the presence (black bars) or absence (white bars) of 10 μM dmPGE₂. Duplicate cell lysates were combined, and Western blot analysis was used to determine the amounts of phospho-AKT and AKT. Upper panel: Densitometry of phospho-AKT corrected for total AKT expression. Lower panel: Representative Western blot.