Figure 9: Ligand-activated EGFR increases sensitivity to virus- and chemotherapy-mediated cell death.

(a) U251 and U87EGFR cells were infected with adenovirus-GFP at an MOI of 10. Cells were examined with immunofluorescence microscopy after 24 h. EGF (50 ng ml⁻¹) or control vehicle were added at the time of adenovirus infection. (b,c) U251EGFR or U87EGFR cells were infected with adenovirus following by an Annexin-FACS assay for detecting cell death. EGF (50 ng ml⁻¹) was added at the time of infection for 24 h and leads to a statistically significant increase in Annexin and PI positive cells compared to cells exposed to adenovirus alone. (d) U251EGFR cells were exposed to EGF or control vehicle and temozolomide (50 μM) for 24 h and an Annexin-FACS assay was performed. In ‘Control’ cells are treated with control vehicle (PBS). Temozolomide alone induces cell death in these cells. The cell death is strikingly amplified when cells are pretreated with EGF (P≤0.001). (e) A similar experiment was conducted in U87EGFR cells with a similar result (P≤0.001). Data were analysed by one-way ANOVA followed by Tukey’s Multiple Comparison test. Cells were serum starved and cultured in serum-free DMEM overnight for all experiments. The EGF concentration used was 50 ng ml⁻¹. Error bars represent the means±standard deviations of three independent experiments. Data were analysed by one-way ANOVA followed by Tukey’s multiple comparison test. *P≤0.05,**P≤0.01, ***P≤0.001.