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Fas-mediated apoptosis in tumor formation and defense
1Zentrum für Molekulare Biologie der Universität Heidelberg, Germany.
Abstract:
Survival of cells that usually die by apoptosis contributes to tumor formation. Fas ligand is a specific death factor that induces apoptosis by binding to its receptor Fas. Expression of Fas ligand in tumor cells resistant to Fas-mediated apoptosis helps the tumor to escape surveillance by the immune system. It induces killing of Fas expressing tissue cells as well as killing of lymphocytes that attack and remove tumor cells. Inducing apoptosis in the attacking lymphocytes resembles the mechanism of how Fas ligand contributes to the maintenance of immune privilege. Some cytostatic drugs used in chemotherapy kill their target cells by upregulating expression of Fas and inducing Fas ligand expression in the same cell by different mechanisms. The cells then undergo suicide or fratricide. Tumor cells which became resistant to Fas-mediated apoptosis should be insensitive to cytotoxic drugs that kill drug-sensitive cells by inducing the Fas system. Therefore, depending on the cell type, the Fas system plays complex roles in the origin, survival and killing of tumors.
Insights
Tumor cells can evade immune surveillance by expressing Fas ligand, a protein that induces cell death. Resistance to Fas-mediated apoptosis can impact chemotherapy effectiveness and tumor survival.
Area of Science:
- Molecular Biology
- Immunology
- Oncology
Background:
- Apoptosis, or programmed cell death, is crucial for preventing tumor formation.
- The Fas ligand/Fas receptor system is a key pathway for inducing apoptosis.
- Tumor cells can develop resistance to Fas-mediated apoptosis, aiding their survival and immune evasion.
Purpose of the Study:
- To explore the multifaceted role of the Fas ligand/Fas receptor system in tumor biology.
- To understand how Fas ligand expression in tumors affects immune surveillance and response to chemotherapy.
Main Methods:
- Analysis of Fas ligand and Fas receptor expression in tumor cells.
- Investigation of mechanisms by which tumor cells acquire resistance to Fas-mediated apoptosis.
- Evaluation of the impact of the Fas system on immune cell interactions with tumors.
Main Results:
- Fas ligand expression by resistant tumor cells promotes immune evasion by killing attacking lymphocytes.
- This mechanism contributes to immune privilege, similar to its role in other physiological contexts.
- Some chemotherapy drugs induce apoptosis via the Fas system, but resistance negates this effect.
Conclusions:
- The Fas system plays a complex role in tumor initiation, progression, and elimination.
- Tumor cell resistance to Fas-mediated apoptosis is a significant factor in treatment failure.
- Understanding these dynamics is critical for developing effective cancer therapies targeting the Fas pathway.