Figure 5

Effects of combining gefitinib with trastuzumab or LY294002 on HRGβ1-driven signalling in tamoxifen-resistant MCF-7 cells. Western analysis of total and phosphorylated epidermal growth factor receptor (EGFR), erbB2, AKT and ERK1/2 protein expression in tamoxifen-resistant MCF-7 (Tam-R) cells prior to and following incubation with either (a) trastuzumab (100 nM) or vehicle control for 7 days, (b) LY294002 (10 μM) or vehicle control for 1 hour, (c) gefitinib (1 μM), gefitinib in combination with trastuzumab or vehicle control for 7 days, and (d) gefitinib, gefitinib in combination with LY294002 or vehicle control for 1 hour, all followed by either HRGβ1 (10 ng/ml) or vehicle control for 5 minutes. Tamoxifen was also present in all studies. Data are representative of at least three separate experiments.