Abstract |
Epidermal growth factor receptor (EGFR) inhibition with small molecule tyrosine kinase inhibitors results in antitumor activity in only a minority of patients whose tumors express EGFR. One hypothesis to explain this suboptimal clinical activity is that multiple growth regulatory pathways are abnormal in most EGFR-expressing cancers. Given the importance of Stat-3 signaling pathway in epidermoid tumors, we hypothesized that blocking complementary pathways in an epidermal growth factor ( EGF)-driven model of proliferation in the A431 cell line would demonstrate improved antiproliferative activity. Exposure of A431 cells to the EGF results in a significant increase in EGFR and Stat-3 phosphorylation. However, inhibition of EGFR by AG1478 fails to decrease EGF-induced Stat-3 phosphorylation. This suggests that EGF continues to drive Stat-3 phosphorylation through other receptors. Our study suggests that residual ErbB2 activation by EGF, despite EGFR blockade, is responsible for persistent downstream activation of Stat-3. In this setting, combined exposure to an EGFR blocker and Stat-3 blocker ( AG490) results in significantly greater tumor growth inhibition than either agent alone. We conclude that targeting multiple pathways (EGFR and JAK/STAT pathways) in EGF-driven tumors may result in greater antiproliferative activity than blocking EGFR alone.
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Authors | Afshin Dowlati, David Nethery, Jeffrey A Kern |
Journal | Molecular cancer therapeutics
(Mol Cancer Ther)
Vol. 3
Issue 4
Pg. 459-63
(Apr 2004)
ISSN: 1535-7163 [Print] United States |
PMID | 15078989
(Publication Type: Journal Article, Research Support, U.S. Gov't, P.H.S.)
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Chemical References |
- 2C4 antibody
- Antibodies, Monoclonal
- DNA-Binding Proteins
- Enzyme Inhibitors
- Quinazolines
- STAT3 Transcription Factor
- STAT3 protein, human
- Trans-Activators
- Tyrphostins
- alpha-cyano-(3,4-dihydroxy)-N-benzylcinnamide
- RTKI cpd
- Epidermal Growth Factor
- ErbB Receptors
- Receptor, ErbB-2
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Topics |
- Antibodies, Monoclonal
(pharmacology)
- Cell Division
(drug effects)
- Cell Line, Tumor
- DNA-Binding Proteins
(antagonists & inhibitors, metabolism)
- Drug Synergism
- Enzyme Activation
(drug effects)
- Enzyme Inhibitors
(pharmacology)
- Epidermal Growth Factor
(pharmacology)
- ErbB Receptors
(antagonists & inhibitors, metabolism)
- Humans
- Inhibitory Concentration 50
- Phosphorylation
(drug effects)
- Quinazolines
- Receptor, ErbB-2
(antagonists & inhibitors, metabolism)
- STAT3 Transcription Factor
- Signal Transduction
(drug effects)
- Trans-Activators
(antagonists & inhibitors, metabolism)
- Tyrphostins
(pharmacology)
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