Epidermal growth factor receptor dependence of radiation-induced transcription factor activation in human breast carcinoma cells.
Ionizing radiation (1-5 Gy) activates the epidermal growth factor receptor (EGFR), a major effector of the p42/44 mitogen-activated protein kinase (MAPK) pathway. MAPK and its downstream effector, p90 ribosomal S6 kinase (p90RSK), phosphorylate transcription factors involved in cell proliferation. To establish the role of the EGFR/MAPK pathway in radiation-induced transcription factor activation, MDA-MB-231 human breast carcinoma cells were examined using specific inhibitors of signaling pathways. Gel-shift analysis revealed three different profile groups: 1) transcription factors that responded to both radiation (2 Gy) and epidermal growth factor (EGF) (CREB, Egr, Ets, and Stat3); 2) factors that responded to radiation, but not EGF (C/EBP and Stat1); and 3) those that did not respond significantly to either radiation or EGF (AP-1 and Myc). Within groups 1 and 2, a two- to fivefold maximum stimulation of binding activity was observed at 30-60 min after irradiation. Interestingly, only transcription factors that responded to EGF had radiation responses significantly inhibited by the EGFR tyrosine kinase inhibitor, AG1478; these responses were also abrogated by farnesyltransferase inhibitor (FTI) or PD98059, inhibitors of Ras and MEK1/2, respectively. Moreover, radiation-induced increases in CREB and p90RSK phosphorylation and activation of Stat3 and Egr-1 reporter constructs by radiation were all abolished by AG1478. These data demonstrate a distinct radiation response profile at the transcriptional level that is dependent on enhanced EGFR/Ras/MAPK signaling.
Department of Radiation Oncology, Medical College of Virginia, Virginia Commonwealth University, Richmond, Virginia 23298, USA.
George P
GP
Amorino
Virginia M
VM
Hamilton
Kristoffer
K
Valerie
Paul
P
Dent
Guido
G
Lammering
Rupert K
RK
Schmidt-Ullrich
D001665:Binding Sites; D001943:Breast Neoplasms / Q000378:metabolism*; D002458:Cell Fractionation; D004791:Enzyme Inhibitors / Q000378:metabolism; D004815:Epidermal Growth Factor / Q000378:metabolism; D066246:ErbB Receptors / Q000378:metabolism*; D005260:Female; D017930:Genes, Reporter; D006801:Humans; D020935:MAP Kinase Signaling System / Q000502:physiology / Q000528:radiation effects*; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D009687:Nuclear Proteins / Q000378:metabolism; D010766:Phosphorylation; D011839:Radiation, Ionizing; D038744:Ribosomal Protein S6 Kinases, 90-kDa / Q000378:metabolism; D013997:Time Factors; D014157:Transcription Factors / Q000037:antagonists & inhibitors / Q000378:metabolism*; D014158:Transcription, Genetic / Q000528:radiation effects; D014407:Tumor Cells, Cultured; D018631:ras Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism
D004791:Enzyme Inhibitors; D009687:Nuclear Proteins; D014157:Transcription Factors; D004815:Epidermal Growth Factor; D066246:ErbB Receptors; D038744:Ribosomal Protein S6 Kinases, 90-kDa; D020928:Mitogen-Activated Protein Kinases; D018631:ras Proteins