Expression of ErbB2 enhances radiation-induced NF-kappaB activation.
Her-2/neu (ErbB2) oncogene, the second member of the epidermal growth factor receptor (EGFR) family, encodes a transmembrane tyrosine kinase receptor in Her-2-positive tumors. Accumulating evidences demonstrate that signaling networks activated by EGFR and transcription factor NF-kappaB are associated with cell response to ionizing radiation (IR). The present study shows that overexpression of ErbB2 enhanced NF-kappaB activation induced by IR in human breast carcinoma MCF-7 cells transfected with ErbB2 genes (MCF-7/ErbB2). Stable transfection of dominant-negative mutant IkappaB (MCF-7/ErbB2/mIkappaB) or treatment with anti-ErbB2 antibody, Herceptin, inhibited NF-kappaB activation and radiosensitized MCF-7/ErbB2 cells. Consistent with NF-kappaB regulation, basal and IR-induced Akt, a kinase downstream of ErbB2, was activated in MCF-7/ErbB2 cells and inhibited by Herceptin. To identify specific genes affected by ErbB2-mediated NF-kappaB activation, a group of IR-responsive elements Cyclin B1, Cyclin D1, Bcl-2, Bcl/XL, BAD and BAX were evaluated. Basal levels of prosurvival elements Cyclin B1, Cyclin D1, Bcl-2 and Bcl/XL but not apoptotic BAD and BAX were upregulated in MCF-7/ErbB2 cells with striking enhancements in Bcl-2 and Bcl/XL. IR further induced Cyclin B1 and Cyclin D1 expression that was reduced by Herceptin. Bcl-2 kept a high steady level after Herceptin+IR treatment and, in contrast to control MCF-7/Vector cells, Bcl/XL was inhibited in MCF-7/ErbB2 cells by Herceptin+IR treatment. However, all four prosurvival proteins were downregulated by inhibition of NF-kappaB in MCF-7/ErbB2/mIkappaB cells. These results thus provide evidence suggesting that overexpression of ErbB2 is able to enhance NF-kappaB response to IR, and that a specific prosurvival network downstream of NF-kappaB is triggered by treatments using anti-ErbB2 antibody combined with radiation.
Guo
Guozheng
G
Division of Radiation Oncology, Beckman Research Institute, City of Hope National Medical Center, Duarte, CA 91010, USA.
Wang
Tieli
T
Gao
Qian
Q
Tamae
Daniel
D
Wong
Patty
P
Chen
Tammy
T
Chen
Wei-Chung
WC
Shively
John E
JE
Wong
Jeffery Y C
JY
Li
Jian Jian
JJ
D000911:Antibodies, Monoclonal / Q000494:pharmacology; D061067:Antibodies, Monoclonal, Humanized; D017209:Apoptosis / Q000187:drug effects / Q000528:radiation effects; D002352:Carrier Proteins / Q000378:metabolism; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects / Q000528:radiation effects; D019926:Cyclin B / Q000378:metabolism; D056744:Cyclin B1; D019938:Cyclin D1 / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects / Q000528:radiation effects; D006801:Humans; D016328:NF-kappa B / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D011839:Radiation, Ionizing; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000235:genetics / Q000378:metabolism*; D000068878:Trastuzumab; D051028:bcl-2-Associated X Protein; D051025:bcl-Associated Death Protein; D051020:bcl-X Protein
D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D002352:Carrier Proteins; D019926:Cyclin B; D056744:Cyclin B1; D019938:Cyclin D1; D016328:NF-kappa B; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D019253:Proto-Oncogene Proteins c-bcl-2; D018719:Erb-b2 Receptor Tyrosine Kinases; D000068878:Trastuzumab; D051028:bcl-2-Associated X Protein; D051025:bcl-Associated Death Protein; D051020:bcl-X Protein; C494819:BAD protein, human; C494826:BAX protein, human; C494811:BCL2L1 protein, human; C534699:CCNB1 protein, human; C494918:AKT1 protein, human