Figure 1.

Radiation-induced activation of MAPK in A431-TR25-EGFR-AS cells is blocked by expression of antisense EGFR or incubation of cells with MEK1/2 inhibitors PD98059 or U0126. A431-TR25-EGFR-AS cells were treated with doxycycline 24 h before irradiation, EGFR inhibitor tyrphostin AG1478 (100 nM) 30 min before irradiation, or MEK1/2 inhibitors (U0126, 2 μM; PD98059, 10 μM) 30 min before irradiation. Cells were irradiated (2 Gy), and MAPK activity was determined from 0 to 300 min. Cells were lysed, and portions (∼100 μg) from each plate were used to immunoprecipitate MAPK, followed by immune complex kinase assays. MAPK activity data are shown as -fold increases in ³²P incorporation into MBP substrate and are normalized to activity at 0 min from the means ± SEM of three independent experiments.