ERK and Src, but not p38, are required for EGFR-mediated induction of COX-2.

<p>A) IEC-6 cells were treated with LPS (2 µg/mL) for 15 minutes or with EGF (10 ng/mL) for 5 minutes in the presence or absence of the EGFR kinase inhibitor AG1478 (1 µM). Western blot analysis of P-p38 MAPK showed no significant difference in p38 activation in the presence of EGFR inhibition. B) IEC-6 cells stimulated with LPS (2 µg/mL) for 15 minutes or with EGF (10 ng/mL) for 5 minutes in the presence or absence of AG1478 (1 µM). C) IEC-6 cells were treated with LPS (2 µg/mL) for 24 hours or with EGF (10 ng/mL) for 5 minutes in the presence or absence of the ERK1/2 inhibitor U0126 (10 µM) or the p38 inhibitor SB202190 (10 µM) as shown, and COX-2 expression was determined using Western blot analysis. D) IEC-6 cells were treated with EGF (10 ng/mL) for 5 minutes in the presence or absence of the Src family kinase inhibitor CGP77675 (2 µM) and analyzed for P-ERK activation using Western blot analysis. Src inhibition had no effect on EGF-induced P-ERK (p = 0.7). IEC-6 cells were also treated with EGF (10 ng/mL) for 5 minutes in the presence or absence of the ERK kinase inhibitor U1026 (10 µM) and analyzed for P-Src activation using Western blot analysis. ERK inhibition had no effect on EGF-induced P-Src activation (p = 0.17). Single asterisks indicate significant differences from control. Double asterisks indicate significant differences between two bracketed conditions.