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Hypoglycemia-induced AP-1 transcription factor and basic fibroblast growth factor gene expression in multidrug
S S Galoforo1, C M Berns, G Erdos
1Department of Radiation Oncology, William Beaumont Hospital, Royal Oak, MI 48073, USA.
Abstract:
We investigated the effect of hypoglycemic treatment on the activation of the AP-1 transcription factors and the regulation of basic fibroblast growth factor (bFGF) gene expression in multidrug resistant human breast carcinoma MCF-7/ADR cells. Northern blot and gel mobility shift assays showed that hypoglycemic treatment induced c-jun and c-fos gene expression, AP-1 binding activity, as well as bFGF gene expression. Moreover, transfected cells expressing high levels of abnormal c-Jun protein exhibited a reduction in the bFGF protein levels compared to parental cells. A potent protein kinase C (PKC) inhibitor, H-7 (60 micrograms/ml) suppressed the stress-induced bFGF gene expression. Our study also demonstrated that H-7 did not facilitate the decay of bFGF mRNA. Thus, the suppression of bFGF gene expression by treatment with H-7 was due to the effect of the drug on the synthesis of bFGF mRNA rather than the stability of bFGF mRNA. Our data suggest that hypoglycemia-induced bFGF gene expression is mediated through the activation of PKC and the AP-1 transcription factors.
Insights
Hypoglycemic treatment activates AP-1 transcription factors and basic fibroblast growth factor (bFGF) gene expression in breast cancer cells. This process involves protein kinase C (PKC) activation and AP-1 transcription factor mediation.
Area of Science:
- Molecular Biology
- Cancer Research
- Biochemistry
Background:
- Multidrug resistant human breast carcinoma MCF-7/ADR cells are a model for studying cancer progression.
- Basic fibroblast growth factor (bFGF) plays a role in cell growth and survival.
- Transcription factors, such as AP-1, regulate gene expression.
Purpose of the Study:
- To investigate the effect of hypoglycemic treatment on AP-1 transcription factor activation.
- To examine the regulation of basic fibroblast growth factor (bFGF) gene expression under hypoglycemic conditions.
- To elucidate the role of protein kinase C (PKC) in hypoglycemia-induced bFGF expression.
Main Methods:
- Northern blot analysis to assess gene expression.
- Gel mobility shift assays to evaluate transcription factor binding activity.
- Transfection studies to investigate protein expression and function.
Main Results:
- Hypoglycemic treatment induced c-jun and c-fos gene expression, AP-1 binding activity, and bFGF gene expression.
- High levels of abnormal c-Jun protein reduced bFGF protein levels.
- A protein kinase C (PKC) inhibitor, H-7, suppressed stress-induced bFGF gene expression by affecting mRNA synthesis, not stability.
Conclusions:
- Hypoglycemia-induced bFGF gene expression in MCF-7/ADR cells is mediated by the activation of protein kinase C (PKC).
- The AP-1 transcription factors are key players in the regulation of bFGF gene expression during hypoglycemia.
- These findings provide insights into the molecular mechanisms underlying breast cancer progression and potential therapeutic targets.