Figure 3.

Radiation-induced activation of MAPK in EGFR-antisense cells is blocked by expression of antisense EGFR mRNA, tyrphostin AG1478, dominant negative Ras N17, or incubation of cells with a neutralizing antibody to TGFα. EGFR-antisense cells were cultured and were treated with doxycycline or neutralizing antibody or infected with adenovirus as described in MATERIALS AND METHODS. Cells were irradiated (2 Gy), and MAPK activity was determined over 0–300 min as in MATERIALS AND METHODS. Cells were lysed, and portions (∼100 μg) from each plate were used to immunoprecipitate MAPK followed by immune complex kinase assays as in MATERIALS AND METHODS. MAPK activity data are shown as fold increases in ³²P incorporation into MBP substrate and are normalized to activity at time = 0 from the means ± SEM of four independent experiments.