Figure 3. Mig6 upregulation is associated with erlotinib resistance.

Head and neck (with PC-3 as prostate), bladder, and lung were treated with indicated doses of erlotinib for 72 hrs and then viable cells were evaluated (A). Value was set at 100% for each vehicle-treated cell line. They were evaluated for total and tyrosine phosphorylated forms of EGFR and Mig6 by immunoblot analysis. β-actin or GAPDH were used as internal loading controls (B). The exposure density of both EGFR and Mig6 blotted on the same membrane were quantified by densitometry and the values of Mig6/EGFR were plotted against IC50 (C). Bladder (D) and lung cancer cell lines (E) were stripped in serum-free medium overnight and treated with vehicle or 10 ng/ml EGF for 10 min, following pretreatment with vehicle or 0.1 µM erlotinib for 3 hrs. Cells were then subjected to immunoblot analysis for phospho-EGFR and total EGFR. β-actin was used as a loading control. Both shorter (p-EGFR-shorter) and longer (p-EGFR-longer) exposure times for phospho-EGFR are shown to provide more detail for each cell line.