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Interruption of NFkappaB-STAT1 signaling mediates EGF-induced cell-cycle arrest
M Ohtsubo1, A Takayanagi, S Gamou
1Department of Molecular Biology, Keio University School of Medicine, Tokyo, Japan.
Abstract:
It is known that EGF induces the cell-cycle arrest in A431 cells that possess high numbers of EGF receptors and it was previously suggested that p21/WAF1 protein was a major effector molecule of the EGF-mediated cell-cycle arrest of A431 cells. Here, we further investigate this phenomenon using the decoy double-strand oligonucleotides for STAT-binding sequence (STAT decoy) and IkappaB, an inhibitor of the nuclear factor kappa B (NFkappaB). Addition of STAT decoy restored EGF-induced A431 cell-growth arrest. Interestingly, infection of adenovirus vectors to express IkappaB (AxIkappaBalphaDeltaN) as the inhibitor of NFkappaB also reversed the A431 cell-growth inhibition. The individual treatment of two inhibitors partially inhibited the WAF1 gene expression, whereas simultaneous treatment of two inhibitors exhibited more efficient inhibition. These observations suggest the activation of NFkappaB via IkappaB degradation and STAT1 via specific receptor kinase activity synergistically induce WAF1 gene expression in A431 cells. Thus, NFkappaB and STAT1 pathways mutually interact to play an important role in the EGF-induced intracellular reaction.
Insights
Epidermal Growth Factor (EGF) triggers cell-cycle arrest in A431 cells by activating both NF-kappaB and STAT1 pathways. These pathways synergistically induce WAF1 gene expression, crucial for EGF-mediated cell growth inhibition.
Area of Science:
- Cell Biology
- Molecular Biology
- Cancer Research
Background:
- Epidermal Growth Factor (EGF) is known to induce cell-cycle arrest in A431 cells, which have abundant EGF receptors.
- p21/WAF1 protein was previously implicated as a key mediator of EGF-induced cell-cycle arrest in these cells.
Purpose of the Study:
- To investigate the specific molecular pathways involved in EGF-mediated cell-cycle arrest in A431 cells.
- To elucidate the roles of Nuclear Factor kappa B (NF-kappaB) and STAT1 in regulating WAF1 gene expression.
Main Methods:
- Utilized decoy double-strand oligonucleotides targeting STAT-binding sequences (STAT decoy).
- Employed adenovirus vectors to express IkappaB (AxIkappaBalphaDeltaN), an inhibitor of NF-kappaB.
- Assessed the effects of these inhibitors on EGF-induced cell-cycle arrest and WAF1 gene expression.
Main Results:
- STAT decoy treatment restored EGF-induced A431 cell-growth arrest.
- Expression of IkappaB also reversed EGF-mediated cell growth inhibition.
- Individual inhibition partially reduced WAF1 gene expression, while combined inhibition showed a more significant reduction.
- NF-kappaB and STAT1 pathways were found to synergistically induce WAF1 gene expression.
Conclusions:
- The activation of NF-kappaB (via IkappaB degradation) and STAT1 (via receptor kinase activity) synergistically drives WAF1 gene expression in A431 cells.
- NF-kappaB and STAT1 pathways exhibit mutual interaction, playing a critical role in EGF-induced intracellular responses.
- This interaction is essential for the EGF-mediated cell-cycle arrest observed in A431 cells.