Figure 2: EGFR tyrosine phosphorylation is inhibited by the EGF receptor tyrosine kinase inhibitor AG1478 (10 μM) but not the PDGF receptor inhibitor AG1298 (5 μM) (a). In contrast, only a modest decrease in Erk1/2 phosphorylation was noted in response to pretreatment of HT-29 cells with either of these agents (b). Serum-starved cells were pretreated for 30 mins prior to stimulation with TNF-α for 15 mins, and EGFR tyrosine phosphorylation and ERK phosphorylation were assessed as described in Materials and Methods. Transactivation of the EGFR in response to TNF-α was also observed in the rat intestinal epithelial cell line IEC-6 (c). IEC-6 cells were treated with 10 ng/mL TNF-α for 15 mins in the presence or absence of 1 μM AG1478. Data are representative of at least three experiments.