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Published on: June 13, 2014
Tumor suppressor ARF inhibits HER-2/neu-mediated oncogenic growth
Yujiang Zhang1, Heng-Yin Yang, Xiao-Chun Zhang
1Department of Molecular and Cellular Oncology, The University of Texas M.D. Anderson Cancer Center, Houston, TX 77030, USA.
Abstract:
HER2/neu, a receptor tyrosine kinase oncogene, promotes mitogenic growth and antiapoptotic activity in cancer cells. Strong expression of HER2/neu in cancers has been associated with poor prognosis. Alternative reading frame protein (ARF), a tumor suppressor protein encoded by a gene located in the Ink4a/ARF gene locus, is frequently inactivated in human cancers. Little is known about the tumor suppressor role of ARF in HER2/neu-overexpressing cancers. Here, we applied the ARF gene as a tumor-suppressive agent for HER2/neu-overexpressing cells under the control of a tetracycline (tet)-regulated gene expression system. We found that ARF antagonized protein kinase B (PKB)/Akt-mediated p27Kip1 phosphorylation and increased p27 stability in HER2/neu-overexpressing cells. ARF expression also led to decreased levels of Cul1 and Skp2, two proteins involved in p27 degradation. We also found that ARF caused apoptosis in HER2/neu-overexpressing cells, and sensitized cells to apoptosis induced by the chemotherapeutic agents taxol and 2-methoxyestradiol. Most significantly for clinical application, we found that ARF inhibited HER2/neu-mediated cell growth, transformation, and tumorigenesis. These findings indicate that modulation of ARF activity may be a useful therapeutic intervention in HER2-overexpressing cancers.
Insights
Alternative reading frame protein (ARF) suppresses tumor growth in HER2-overexpressing cancers by enhancing p27 stability and promoting apoptosis. ARF acts as a tumor suppressor, offering a potential therapeutic strategy for HER2-positive cancers.
Area of Science:
- Oncology
- Molecular Biology
- Cancer Genetics
Background:
- HER2/neu overexpression drives cancer growth and survival, correlating with poor prognosis.
- Alternative reading frame protein (ARF) is a tumor suppressor frequently inactivated in cancers.
- The role of ARF in HER2/neu-overexpressing cancers remains largely unexplored.
Purpose of the Study:
- To investigate the tumor suppressor function of ARF in HER2/neu-overexpressing cancer cells.
- To elucidate the molecular mechanisms by which ARF exerts its effects.
- To assess the therapeutic potential of ARF in HER2-overexpressing cancers.
Main Methods:
- Utilized a tetracycline-regulated gene expression system to control ARF expression in HER2/neu-overexpressing cells.
- Assessed the impact of ARF on p27Kip1 stability and phosphorylation.
- Quantified levels of Cul1 and Skp2, proteins involved in p27 degradation.
- Evaluated ARF's effect on apoptosis induction, both spontaneously and in response to chemotherapeutics (taxol, 2-methoxyestradiol).
- Assessed ARF's inhibition of HER2/neu-mediated cell growth, transformation, and tumorigenesis.
Main Results:
- ARF expression antagonized PKB/Akt-mediated p27Kip1 phosphorylation, increasing p27 stability.
- ARF expression decreased levels of Cul1 and Skp2, key regulators of p27 degradation.
- ARF induced apoptosis in HER2/neu-overexpressing cells and sensitized them to chemotherapy.
- ARF significantly inhibited HER2/neu-driven cell growth, transformation, and tumorigenesis.
Conclusions:
- ARF functions as a potent tumor suppressor in HER2/neu-overexpressing cancers.
- ARF modulates p27 stability and promotes apoptosis, counteracting HER2/neu oncogenic signaling.
- Targeting ARF represents a promising therapeutic strategy for HER2-overexpressing malignancies.
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