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Mutant H-ras overexpression inhibits drug and U.V. induced apoptosis
R S Fernandes1, A J McGowan, T G Cotter
1Department of Biochemistry, University College Cork, Ireland.
Abstract:
Various studies have shown that oncogene and oncosuppressor gene activity can enhance or suppress programmed cell death (apoptosis) in various cell systems. Recent data indicates that overexpression of activated H-ras could influence that onset of apoptosis. We investigated the role of activated H-ras in the apoptotic cell death of rat fibroblast lines. We found that forced overexpression of H-ras induced resistance to U.V. and drug induced apoptosis. We examined possible mechanisms for the action of H-ras in resistance to apoptosis. It was found that both ras transfected and ras untransfected lines displayed similar endonuclease activities. In addition, it was found that the irradiated ras transfected line showed inhibited production of peroxides compared to the irradiated ras untransfected line. Drug induced apoptosis did not appear to involve peroxide production. In addition the antioxidant compound PDTC, was found to inhibit U.V. induced apoptosis but not drug induced apoptosis. In addition, we found the ras transfected line to possess elevated levels of catalase compared to the parent untransfected line. Thus we suggest that an anti-oxidant mechanism, possibly mediated by forced overexpression of activated H-ras could protect cells from apoptosis.
Insights
Overexpression of activated H-ras confers resistance to apoptosis by inhibiting peroxide production, suggesting an antioxidant mechanism protects cells. This finding is crucial for understanding cancer development and potential therapeutic targets.
Area of Science:
- Molecular Biology
- Cell Biology
- Oncology
Background:
- Oncogene and oncosuppressor gene activity modulate programmed cell death (apoptosis).
- Activated H-ras overexpression is implicated in influencing apoptosis onset.
- Rat fibroblast lines were used to investigate H-ras's role in apoptosis.
Purpose of the Study:
- To investigate the role of activated H-ras in apoptotic cell death.
- To determine if H-ras overexpression affects resistance to apoptosis.
- To elucidate the mechanisms underlying H-ras-mediated apoptosis resistance.
Main Methods:
- Forced overexpression of activated H-ras in rat fibroblast lines.
- Induction of apoptosis using UV radiation and drugs.
- Assay of endonuclease activity.
- Measurement of peroxide production.
- Assessment of antioxidant compound (PDTC) effects.
- Quantification of catalase levels.
Main Results:
- Forced H-ras overexpression induced resistance to UV and drug-induced apoptosis.
- Ras-transfected and untransfected lines showed similar endonuclease activities.
- Irradiated ras-transfected cells exhibited inhibited peroxide production compared to controls.
- UV-induced apoptosis was inhibited by the antioxidant PDTC, but drug-induced apoptosis was not.
- Ras-transfected lines displayed elevated catalase levels.
Conclusions:
- Activated H-ras overexpression confers resistance to apoptosis, particularly UV-induced apoptosis.
- An antioxidant mechanism, potentially involving elevated catalase and inhibited peroxide production, mediates H-ras's protective effect against apoptosis.
- These findings suggest a role for antioxidant pathways in oncogene-driven cell survival and resistance to apoptosis.