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Detection of soluble Fas mRNA using in situ reverse transcription-polymerase chain reaction
1Department of Pathology and Cancer Research Institute, Catholic University Medical College, Seoul, Korea.
Abstract:
Fas protein (Fas) is known to induce cell death by apoptosis in susceptible cells. Alternative splicing of the Fas gene produces soluble Fas protein (sFas), which is considered to block the function of Fas. The serum level of sFas is elevated in patients with various malignancies in a manner reflective of disease stage and tumor burden, but the precise cellular origin of sFas in vivo has not yet been clarified. To identify the cells that synthesize sFas mRNA on histologic specimens, we applied in situ reverse transcription-polymerase chain reaction (in situ RT-PCR) in 11 cases of gastric adenocarcinoma/metastatic lymph node. Furthermore, we studied the distribution of Fas using immunohistochemistry and Fas mRNA using in situ RT-PCR. In all primary tumors and 10 of 11 metastatic tumors, tumor cells expressed both Fas- and sFas mRNA. Lymphocytes infiltrated in the tumor tissues and the lymph nodes also revealed both mRNA signals. A clear correlation between the tissue distribution for Fas and its mRNA was also observed. These observations demonstrated that solid tumors in vivo can synthesize sFas mRNA and suggest that tumor cells are responsible in part for elevated sFas in human malignancies. However, the additional expression of sFas mRNA in tissue lymphocytes indicates the complex regulatory mechanisms of Fas-mediated apoptosis pathway in tumor pathogenesis and host defense. We also demonstrated that in situ RT-PCR can be a suitable method for in situ detection of alternatively spliced mRNA.
Insights
Tumor cells in gastric cancer can produce soluble Fas (sFas) mRNA, contributing to elevated sFas levels in malignancies. In situ RT-PCR confirmed sFas mRNA synthesis in tumor cells and infiltrating lymphocytes.
Area of Science:
- Molecular Biology
- Oncology
- Immunology
Background:
- Fas protein induces apoptosis, while soluble Fas (sFas) may inhibit this function.
- Elevated serum sFas levels correlate with malignancy stage and tumor burden.
- The cellular origin of in vivo sFas in cancer remains unclear.
Purpose of the Study:
- To identify the specific cells synthesizing soluble Fas mRNA in gastric adenocarcinoma.
- To investigate the distribution of Fas protein and its mRNA in tumor tissues.
- To evaluate the utility of in situ RT-PCR for detecting alternatively spliced mRNA.
Main Methods:
- In situ reverse transcription-polymerase chain reaction (in situ RT-PCR) was performed on 11 gastric adenocarcinoma/metastatic lymph node specimens.
- Immunohistochemistry was used to study Fas protein distribution.
- In situ RT-PCR was employed to detect Fas and sFas mRNA.
Main Results:
- Tumor cells in primary and metastatic gastric adenocarcinomas expressed both Fas and sFas mRNA.
- Infiltrating lymphocytes within tumor tissues and lymph nodes also showed Fas and sFas mRNA signals.
- A strong correlation was observed between Fas protein and mRNA distribution in tissues.
Conclusions:
- Solid tumors, including gastric adenocarcinomas, can synthesize sFas mRNA in vivo.
- Tumor cells partially contribute to elevated serum sFas levels in malignancies.
- Lymphocyte expression of sFas mRNA suggests complex regulation of Fas-mediated apoptosis in cancer and host defense.