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The normal response to RAS: senescence or transformation?
Jennifer A Benanti1, Denise A Galloway
1Program in Cancer Biology, Fred Hutchinson Cancer Research Center, Seattle, Washington 98109-1024, USA.
Cell Cycle (Georgetown, Tex.)
|May 22, 2004
Summary
Normal cells resist RAS-induced senescence, but aging (extended passaging) increases p16 levels, sensitizing them. This suggests external stress is crucial for RAS-induced cell cycle arrest and transformation.
Area of Science:
- Cell Biology
- Oncology
- Molecular Biology
Background:
- Normal cells typically undergo cellular senescence to prevent transformation.
- Cellular senescence is a permanent cell cycle arrest triggered by oncogene expression, like RAS.
- Neonatal human fibroblasts are resistant to RAS-induced senescence.
Purpose of the Study:
- To investigate the factors influencing RAS-induced senescence in normal fibroblasts.
- To determine the role of fibroblast passaging and p16 in RAS-induced senescence.
- To understand the relationship between exogenous stress and oncogene-induced transformation.
Main Methods:
- Culturing and passaging of neonatal human fibroblasts.
- Introduction of activated RAS oncogene expression.
- Assessment of cell cycle arrest (senescence) and p16 protein levels.
Main Results:
- Freshly established neonatal human fibroblasts were resistant to RAS-induced senescence.
- Extended passaging of fibroblasts led to increased p16 levels.
- Increased p16 levels sensitized fibroblasts to RAS-induced senescence.
Conclusions:
- Exogenous stress, such as extended passaging, acts as a necessary cofactor in RAS-induced senescence.
- RAS expression can promote transformation-like characteristics even without other genetic alterations, provided senescence is overcome.
- Cellular senescence is a complex process influenced by both oncogenic signaling and cellular aging.