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K-ras modulates the cell cycle via both positive and negative regulatory pathways
1Program for Molecular Pharmacology and Therapeutics, Memorial Sloan-Kettering Cancer Center, New York, NY 10021, USA.
Oncogene
|May 29, 1997
Summary
Activated Kirsten ras (K-ras) accelerates cell growth by influencing cell cycle proteins. It upregulates cyclins and E2F factors while modulating inhibitors like p53 and p27Kip1.
Area of Science:
- Molecular Biology
- Cell Biology
- Oncology
Background:
- Kirsten ras (K-ras) is a proto-oncogene frequently mutated in human cancers.
- Understanding K-ras signaling is crucial for developing targeted cancer therapies.
- The precise mechanisms by which activated K-ras influences cell cycle progression remain incompletely understood.
Purpose of the Study:
- To investigate the effects of activated human K-ras on cell cycle regulatory proteins.
- To elucidate the molecular mechanisms underlying K-ras-driven cell cycle modulation.
Main Methods:
- Utilized a stable MCF-7 cell line with a tetracycline (Tet)-inducible activated K-ras expression system.
- Analyzed the expression levels of key cell cycle stimulatory and inhibitory proteins.
- Assessed the functional activity of transcription factors and associated kinase activities.
Main Results:
- Inducible activated K-ras expression accelerated cell growth and S-phase entry.
- Upregulation of cyclins A, D3, E, and E2F transcription factors, with increased cyclin A-associated kinase and E2F activity.
- Downregulation of p27Kip1 and upregulation of p53, p21Waf1, and Gadd 45, indicating modulation of negative regulators.
- Activated K-ras upregulated bcl-2 expression but did not affect bax or bcl-x.
Conclusions:
- Activated K-ras significantly impacts cell cycle progression by altering the balance of positive and negative regulatory pathways.
- These findings provide insights into K-ras-mediated oncogenesis and potential therapeutic targets.