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Ceramide triggers p53-dependent apoptosis in genetically defined fibrosarcoma tumour cells
1Department of Radiation Oncology, University Hospital Zurich, Switzerland.
Abstract:
p53 mutations are among the most common genetic alterations in human cancer and are frequently described in intrinsic or acquired radio- and chemotherapy resistance. Radiation-induced cell kill is not only mediated by DNA damage but also by the activation of signal transduction cascades generated at the plasma membrane like the sphingomyelin pathway. We used genetically defined wild-type p53 or p53-deficient mouse fibrosarcoma cells to investigate the p53-dependence of tumour response upon activation of the sphingomyelin pathway. Treatment of the tumour cells with neutral sphingomyelinase drastically reduced the amount of wild-type p53 fibrosarcoma cell proliferation over 72 h in a clear dose-response (0.2-1.0 U ml(-1) nSMase). Sphingomyelinase had no effect on cell proliferation in tumour cells lacking p53. Similarly, cell proliferation was abolished by C2-ceramide (5-20 microM) only in wild-type p53 cells. FACS-analysis revealed that C2-ceramide induced massive p53-dependent apoptosis (40-50% after 12-24 h) and cell cycle analysis showed a transient G1 arrest in p53-deficient tumour cells 12-24 h after C2-ceramide exposure. These results suggest that ceramide-induced apoptosis in tumour cells can be dependent on the status of p53 and imply that p53 is also important for stress-induced apoptotic signal transduction cascades generated at the plasma membrane.
Insights
The tumor suppressor protein p53 is crucial for ceramide-induced apoptosis in cancer cells. This study shows p53-dependent cell death and proliferation reduction upon sphingomyelin pathway activation.
Area of Science:
- Cancer biology
- Molecular oncology
- Cell signaling
Background:
- p53 mutations are common in human cancers and linked to therapy resistance.
- Cancer cell death can be induced by DNA damage or plasma membrane signaling pathways, such as the sphingomyelin pathway.
- The role of p53 in sphingomyelin pathway-induced apoptosis is not fully understood.
Purpose of the Study:
- To investigate the p53-dependence of tumor response to sphingomyelin pathway activation.
- To determine if p53 status influences ceramide-induced apoptosis and cell cycle arrest.
Main Methods:
- Utilized genetically defined wild-type p53 and p53-deficient mouse fibrosarcoma cells.
- Treated cells with neutral sphingomyelinase and C2-ceramide.
- Performed FACS analysis for apoptosis and cell cycle analysis.
Main Results:
- Neutral sphingomyelinase and C2-ceramide significantly reduced proliferation in wild-type p53 cells but not in p53-deficient cells.
- C2-ceramide induced massive p53-dependent apoptosis (40-50%) in wild-type p53 cells.
- A transient G1 arrest was observed in p53-deficient cells after C2-ceramide exposure.
Conclusions:
- Ceramide-induced apoptosis in tumor cells is dependent on the p53 status.
- p53 plays a significant role in stress-induced apoptotic signaling cascades originating from the plasma membrane.