Expression of the <i>EGFR</i>-GS and—DEL mutant proteins enhances MCF10A EGF-independent growth and sensitivity to gefitinib.

<p><b>A.</b> Cells were cultured in the presence (+ EGF) or absence (- EGF) of EGF and their proliferation assessed using MTS assay by measuring absorbance at 490 nm over a period of 8 days. <b>B.</b> The doubling times of the cell lines were calculated from the rates of proliferation. As neither MCF10A nor MCF10A-WT cell proliferated in the absence of EGF, a doubling time could not be calculated. <b>C.</b> Cells were treated with varying concentrations of gefitinib in the absence of EGF for 72 hours and cell viability measured using the MTS assay. The IC₅₀ was calculated and the differences compared using the unpaired t-Test (* p<0.05). <b>D.</b> Cells were treated with varying concentrations of gefitinib in the presence of EGF for 72 hours and cell viability measured using the MTS assay. The IC₅₀ was calculated and the differences compared using the unpaired t-Test (**** p<0.0001). 10A: MCF10A-EV, WT: MCF10A-<i>EGFR</i>-WT, GS: MCF10A-<i>EGFR</i>-GS, DEL: MCF10A-<i>EGFR</i>-DEL. Data from duplicate experiments.