FIGURE 3.

ERK and STAT3 pathways are differentially sensitive to EGF receptor activity. A, cells were stimulated with increasing concentrations of EGF for 5 min (left panel) or treated with increasing concentrations of Tarceva (erlotinib) before stimulating with 100 ng/ml EGF for 5 min (right panel). Lysates were immunoblotted with indicated antibodies. MEK1 is included as a control for equal protein loading. B, human bronchial epithelial cell line (HBEC) and H1819 (lung adenocarcinoma cell line) cells were stimulated for 5 min with increasing concentrations of EGF and probed for pERK and pSTAT3. An A431 lysate of equivalent total protein concentration from 100 ng/ml EGF stimulation is included for comparison.