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Simultaneous expression of Fas and nonfunctional Fas ligand in Ewing's sarcoma
H U Kontny1, T M Lehrnbecher, S J Chanock
1Pediatric Oncology Branch, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA.
Abstract:
Fas-Fas ligand interactions play a central role in the regulation of the immune response. Fas ligand expression by tumors has been implicated in the abrogation of the host antitumor response by killing of Fas-positive effector lymphocytes. We have studied the presence and functional status of Fas and Fas ligand in Ewing's sarcoma. All Ewing's sarcoma cell lines tested expressed Fas on their surface. Three of the cell lines were readily killed after ligation of the Fas receptor. Four additional cell lines exhibited Fas-mediated apoptosis after preincubation with IFN-gamma and/or cycloheximide, whereas two cell lines were resistant to Fas-mediated killing. With regard to Fas ligand, all cell lines examined were positive for protein by immunoblot, and specificity was confirmed by reverse transcription-PCR. However, using flow cytometric analysis, Fas ligand could only be detected in Ewing's sarcoma cells after permeabilization. Furthermore, the cell lines were not capable of inducing apoptosis of Fas-sensitive Jurkat cells. In addition, Ewing's sarcoma cell lines were able to serve as stimulators for the generation of cytotoxic effector lymphocytes and were susceptible to lysis by them. Therefore, Fas ligand is expressed in Ewing's sarcoma but is not functional, suggesting that Ewing's sarcoma is a potential target for immunotherapy.
Insights
Ewing's sarcoma cells express Fas ligand, but it is not functional. This suggests that Ewing's sarcoma is a potential target for immunotherapy, as the tumor cells are susceptible to immune attack.
Area of Science:
- Immunology
- Oncology
- Cell Biology
Background:
- Fas-Fas ligand interactions are crucial for immune response regulation.
- Tumor-expressed Fas ligand can suppress host anti-tumor immunity by eliminating effector lymphocytes.
Purpose of the Study:
- To investigate the expression and functional status of Fas and Fas ligand in Ewing's sarcoma.
- To determine if Ewing's sarcoma cells are susceptible to Fas-mediated apoptosis and if their expressed Fas ligand is functional.
Main Methods:
- Analysis of Fas and Fas ligand expression in Ewing's sarcoma cell lines using immunoblot, reverse transcription-PCR, and flow cytometry.
- Assessment of Fas-mediated apoptosis induction and effector lymphocyte generation/lysis.
- Treatment with interferon-gamma (IFN-gamma) and/or cycloheximide.
Main Results:
- All Ewing's sarcoma cell lines expressed Fas, with some sensitive to Fas-mediated apoptosis.
- Fas ligand protein was detected in all cell lines, but it was not functional, failing to induce apoptosis in sensitive cells.
- Ewing's sarcoma cells could stimulate effector lymphocytes and were susceptible to lysis by them.
Conclusions:
- Fas ligand is expressed but non-functional in Ewing's sarcoma.
- Ewing's sarcoma exhibits susceptibility to immune-mediated killing, indicating its potential as a target for immunotherapy.