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Analysis of FasL and TRAIL induced apoptosis pathways in glioma cells
M J Knight1, C D Riffkin, A M Muscat
1Department of Haematology and Oncology, Royal Children's Hospital, Parkville, Victoria, Australia 3052.
Abstract:
FasL and TNF-related apoptosis-inducing ligand (TRAIL) belong to a subgroup of the TNF superfamily which induce apoptosis by binding to their death domain containing receptors. In the present study we have utilized a panel of seven cell lines derived from human malignant gliomas to characterize molecular pathways through which FasL and TRAIL induce apoptosis in sensitive glioma cells and the mechanisms of resistance in cell lines which survive the death stimuli. Our findings indicate that FADD and Caspase-8 are essential for FasL and TRAIL mediated apoptosis in glioma cells. One sensitive cell line (D270) can be protected from FasL and TRAIL induced death by anti-apoptotic Bcl-2 family members while another (D645) cannot, implying that these lines may represent glioma examples of type II and type I cells respectively. For the first time we demonstrate resistance to FasL but not to TRAIL within the one glioma cell line. Furthermore, we report distinct mechanisms of resistance within different glioma lines, including downregulation of Caspase-8 in U373MG. Cycloheximide sensitized four of the resistant cell lines suggesting the presence of labile inhibitors. None of the known apoptosis inhibitors examined accounted for the observed resistance, suggesting novel inhibitors may exist in glioma cells.
Insights
This study explores how FasL and TRAIL induce apoptosis in human malignant glioma cells. Researchers identified key molecular pathways and resistance mechanisms, revealing potential novel inhibitors for glioma treatment.
Area of Science:
- Molecular Biology
- Cancer Research
- Cell Death Signaling
Background:
- FasL and TRAIL are TNF superfamily members inducing apoptosis via death receptors.
- Malignant gliomas are aggressive brain tumors with complex cell death regulation.
Purpose of the Study:
- To characterize apoptosis pathways induced by FasL and TRAIL in human malignant glioma cells.
- To elucidate mechanisms of resistance to these death ligands in resistant glioma cell lines.
Main Methods:
- Utilized a panel of seven human malignant glioma cell lines.
- Investigated molecular pathways including FADD, Caspase-8, and Bcl-2 family members.
- Assessed resistance mechanisms using cycloheximide and known apoptosis inhibitors.
Main Results:
- FADD and Caspase-8 are essential for FasL/TRAIL-mediated apoptosis in sensitive glioma cells.
- Differential sensitivity observed, with some lines exhibiting Type I/II characteristics.
- Distinct resistance mechanisms identified, including Caspase-8 downregulation and potential novel inhibitors.
Conclusions:
- Glioma cells employ diverse strategies to resist FasL and TRAIL-induced apoptosis.
- Understanding these mechanisms is crucial for developing targeted therapies.
- Further research into novel apoptosis inhibitors is warranted for glioma treatment.