Fig. 8.

Receptor tyrosine kinases and integrins engage in cooperative signaling to stimulate FAK phosphorylation at tyrosines 576/577 in N18TG2 cells. (A,B) Cells were pretreated for 15 min with the integrin antagonist RGDS peptide (100 μM), the Flk-1 VEGFR inhibitor SU5416 (1 μM), or EGFR inhibitor AG 1478 (2 μM) prior to treatment with 40 ng/mL VEGF or 100 ng/mL EGF for 1 or 2 min at 37°C. Immunoblot analysis was performed and data are reported as mean ± SEM of the % change over basal pFAK tyrosine 576/577 levels (normalized to total FAK at each time point) from three separate experiments. Growth factor-stimulated values are expressed as 100%, and inhibitor-treated values are expressed as a percent of growth factor-stimulated pFAK/FAK levels. * p < 0.001 indicates significantly different from growth factor-stimulated at the same time point using Student's t-test.