Figure 6.

Radiation-induced secondary activation of MAPK and JNK is dose dependent and is mediated by TGFα. EGFR-antisense cells were treated 30 min before irradiation with either control antibody (A, MAPK; B, JNK) or anti-TGFα-neutralizing antibody (C, MAPK; D, JNK) as described in MATERIALS AND METHODS. Cells were exposed to increasing doses of radiation (1–20 Gy). At the indicated times after radiation exposure, plates were snap frozen. Cells were lysed, and identical portions (∼100 μg) from each plate were used to immunoprecipitate either MAPK (A and C) or JNK (B and D) for activity assessment as in MATERIALS AND METHODS. Data are shown as fold increases in ³²P incorporation into MBP (MAPK) or GST-c-Jun (JNK) substrates and are normalized to activity at time = 0. Data are from a representative of three independent experiments.