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Expression of TRAIL and its receptors in human brain tumors
S Frank1, U Köhler, G Schackert
1Department of Surgical Research, Technical University of Dresden, Dresden, Germany. stfrank@helix.nih.gov
Abstract:
Recently, TRAIL has been demonstrated to selectively induce apoptosis in transformed cell lines, and subsequently four receptors (TRAIL-R1-TRAIL-R4) have been identified. The ability to transduce death signals is restricted to TRAIL-R1/TRAIL-R2. In contrast, TRAIL-R3/TRAIL-R4 are unable to activate apoptotic pathways and have therefore been suggested to act as "decoys" protecting normal tissues from cell death. However, the biological role of the TRAIL system remains incompletely understood. We analyzed the expression of TRAIL and its receptors in a panel of human brain tumors (n = 34) and in four glioma cell lines in comparison to normal brain tissue. Constant co-expression of TRAIL and of receptors TRAIL-R1, TRAIL-R2, and TRAIL-R3 in different tumor entities as well as in normal brain indicates that additional mechanisms might modulate the previously proposed "decoy" model. Furthermore, in contrast to previous reports, we demonstrate TRAIL and TRAIL-R2 to be present on a transcriptional level in normal brain tissue. Exceptional expression of TRAIL-R4 transcripts does not suggest a significant regulatory role of this receptor in the human brain and its tumors.
Insights
The Tumor Necrosis Factor-Related Apoptosis-Inducing Ligand (TRAIL) system
Area of Science:
- Molecular Biology
- Cancer Research
- Neuro-Oncology
Background:
- The Tumor Necrosis Factor-Related Apoptosis-Inducing Ligand (TRAIL) system, including its receptors TRAIL-R1-TRAIL-R4, plays a role in programmed cell death.
- TRAIL-R1 and TRAIL-R2 transduce death signals, while TRAIL-R3 and TRAIL-R4 are considered decoy receptors protecting normal cells.
- The precise biological function of the TRAIL system in brain tumors and normal brain tissue requires further investigation.
Purpose of the Study:
- To investigate the expression patterns of TRAIL and its receptors in human brain tumors and glioma cell lines.
- To compare TRAIL system expression in neoplastic brain tissue with normal brain tissue.
- To clarify the functional roles of TRAIL receptors in the context of brain tumors and normal brain.
Main Methods:
- Analysis of TRAIL and TRAIL receptor expression in a cohort of 34 human brain tumors.
- Examination of four glioma cell lines for TRAIL system components.
- Comparison of gene expression profiles between tumor samples and normal brain tissue.
Main Results:
- Consistent co-expression of TRAIL, TRAIL-R1, TRAIL-R2, and TRAIL-R3 was observed in various brain tumor types and normal brain tissue.
- TRAIL and TRAIL-R2 were detected at the transcriptional level in normal brain tissue, contradicting previous reports.
- TRAIL-R4 transcripts showed minimal expression, suggesting a limited regulatory role in the human brain and its associated tumors.
Conclusions:
- The expression patterns of TRAIL and its receptors suggest that the 'decoy' model may be modulated by additional mechanisms.
- The presence of TRAIL and TRAIL-R2 in normal brain challenges previous assumptions about their restricted expression.
- TRAIL-R4 appears to have a negligible role in regulating cell death in the human brain and brain tumors.