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CD95-mediated apoptosis of human glioma cells: modulation by epidermal growth factor receptor activity
Joachim P Steinbach1, Petra Supra, H-J Su Huang
1Department of Neurology, University of Tübingen, School of Medicine, Germany. joachim.steinbach@uni-tuebingen.de
Abstract:
The death ligands CD95L and Apo2L/TRAIL are promising investigational agents for the treatment of malignant glioma. EGFR is overexpressed in a significant proportion of malignant gliomas in vivo. Here, we report that CD95L-induced cell death is enhanced by EGFR inhibition using tyrphostine AG1478 in 7 of 12 human malignant glioma cell lines. Conversely, CD95-mediated and Apo2L-induced cell death are both inhibited by overexpression of EGFR in LN-229 cells. CD95L-induced cell death augmented by AG1478 is accompanied by enhanced processing of caspase 8. LN-229 cells overexpressing the viral caspase inhibitor, crm-A, are not sensitized to CD95L-induced cell death by AG1478, indicating that EGFR exerts its antiapoptotic properties through a caspase 8-dependent pathway. These data define a modulatory effect of EGFR-activity on death ligand-induced apoptosis and indicate that EGFR inhibition is likely to improve the efficacy of death ligand-based cancer therapies. Furthermore, it is tempting to speculate that EGFR amplification protects tumor cells from death ligand-mediated host immune responses in vivo and that EGFR's effects on death receptor-mediated apoptosis may explain the anti-tumor effects of non-cytotoxic, unarmed anti-EGFR family antibodies.
Insights
Inhibiting Epidermal Growth Factor Receptor (EGFR) enhances cancer cell death induced by death ligands like CD95L. This suggests combining EGFR inhibitors with death ligand therapies could improve malignant glioma treatment.
Area of Science:
- Oncology
- Molecular Biology
- Cancer Research
Background:
- Malignant gliomas often overexpress Epidermal Growth Factor Receptor (EGFR).
- Death ligands, including CD95L and Apo2L/TRAIL, are investigated for cancer therapy.
- EGFR's role in regulating apoptosis in glioma cells is not fully understood.
Purpose of the Study:
- To investigate the interplay between EGFR signaling and death receptor-mediated apoptosis in malignant glioma.
- To determine if EGFR inhibition can sensitize glioma cells to death ligands.
- To elucidate the molecular mechanisms underlying EGFR's influence on apoptosis.
Main Methods:
- Utilized human malignant glioma cell lines.
- Administered EGFR inhibitor tyrphostine AG1478.
- Assessed cell death induction by CD95L and Apo2L/TRAIL.
- Overexpressed EGFR and viral caspase inhibitor crm-A in LN-229 cells.
- Analyzed caspase 8 processing.
Main Results:
- EGFR inhibition enhanced CD95L-induced cell death in 7/12 glioma cell lines.
- EGFR overexpression inhibited CD95-mediated and Apo2L-induced cell death.
- Enhanced cell death correlated with increased caspase 8 processing.
- EGFR's anti-apoptotic effect is dependent on caspase 8.
Conclusions:
- EGFR activity modulates sensitivity to death ligand-induced apoptosis.
- EGFR inhibition may improve the efficacy of death ligand-based cancer therapies.
- EGFR may protect tumor cells from immune responses and influence anti-EGFR antibody efficacy.