FIGURE 1.

EGF signaling inhibits α5β1 integrin-dependent A431 cell adhesion to fibronectin. A, A431 cells were allowed to adhere to fibronectin (10 μg/ml)-coated wells in the presence of the indicated concentrations of EGF. B, cell suspensions were pretreated for 1 h with either control mouse IgG or anti-α5 integrin blocking antibody P1D6 at the indicated concentrations prior to addition to fibronectin-coated wells for 1 h. C and D, cells were pretreated for 1 h with the indicated amounts of either the EGFR kinase inhibitor AG1478 (C) or the MEK inhibitors PD184352 and U0126 (D) prior to the addition of 3 nm EGF and allowed to adhere to fibronectin-coated wells for 1 h. Cells were then fixed in formaldehyde, and cell adhesion was assessed by staining with toluidine blue. The dye was extracted with 10% acetic acid, and its optical density was measured at 650 nm. Error bars indicate S.D. of triplicate samples for one of three representative experiments.