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Decreased Fas expression in advanced-stage bladder cancer is not related to p53 status
Simone Maas1, Ulrich Warskulat, Christine Steinhoff
1Department of Urology, Heinrich-Heine-University, Duesseldorf, Germany.
Objectives:
The Fas-Fas ligand system is an important regulator of apoptosis and is involved in tumor development. Invasive cancers downregulate Fas expression to evade antitumor immune responses. Fas is a transcriptional target of p53, which is often mutated in bladder cancers. Therefore, Fas expression and its relation to p53 mutation was investigated.
Methods:
Expression of Fas protein and p53 status was studied by immunohistochemistry in 83 bladder cancer specimens. In addition, mRNA levels for soluble (decoy) and membrane-bound forms of Fas were compared between 10 bladder cancer cell lines and primary uroepithelial cells by quantitative TaqMan polymerase chain reaction. Mutational analysis of the death domain of the Fas gene was performed in all cell lines.
Results:
Organ-confined tumors maintained specific Fas staining at the cell membrane and often also in the cytoplasm. In higher stage carcinomas, Fas expression became restricted to a smaller fraction of cells or was lacking entirely. The correlation of Fas staining with tumor stage was highly significant but no correlation to tumor grade or survival was found. Furthermore, no statistically significant relationship was observed with either the presence or lack of mutated p53 accumulation. Membrane-bound Fas mRNA was decreased in most, and soluble Fas was increased in all transitional cell carcinoma lines compared with primary uroepithelial cells. No mutations in the death domain were detected.
Conclusions:
Fas downregulation occurring in advanced bladder cancer is unrelated to p53 mutations. The results of immunohistochemistry and mRNA studies of soluble and membrane-bound Fas in transitional cell carcinoma lines support the hypothesis of immune evasion in advanced bladder cancer.
Insights
Fas expression decreases in advanced bladder cancer, unrelated to p53 mutations. This Fas downregulation in bladder tumors may facilitate immune evasion, impacting cancer progression.
Area of Science:
- Oncology
- Immunology
- Molecular Biology
Background:
- The Fas-Fas ligand system regulates apoptosis and is implicated in tumor development.
- Invasive cancers often downregulate Fas expression to evade antitumor immune responses.
- Fas is a transcriptional target of p53, frequently mutated in bladder cancers.
Purpose of the Study:
- To investigate Fas expression in bladder cancer.
- To determine the relationship between Fas expression and p53 mutation status.
- To explore the role of Fas in immune evasion in advanced bladder cancer.
Main Methods:
- Immunohistochemistry analyzed Fas protein expression and p53 status in 83 bladder cancer specimens.
- Quantitative TaqMan PCR compared Fas mRNA levels (soluble and membrane-bound) in bladder cancer cell lines and primary uroepithelial cells.
- Mutational analysis of the Fas gene's death domain was conducted in all cell lines.
Main Results:
- Fas staining decreased significantly with increasing tumor stage, being absent in higher-stage carcinomas.
- No significant correlation was found between Fas staining, tumor grade, survival, or p53 mutation status.
- Membrane-bound Fas mRNA was reduced, and soluble Fas mRNA increased in transitional cell carcinoma lines compared to normal cells.
Conclusions:
- Fas downregulation in advanced bladder cancer is independent of p53 mutations.
- Reduced Fas expression in bladder cancer supports the hypothesis of immune evasion.
- Findings highlight the role of Fas in advanced bladder cancer immune evasion mechanisms.
