Background and objective: Epstein-Barr virus (EBV) has been detected in about 10% of gastric carcinomas. However, the pathogenetic role of EBV in gastric carcinoma is uncertain. This study was to explore the correlation of Fas/FasL expression to the apoptosis of tumor cells and tumor-infiltrating lymphocytes (TIL) in EBV-associated gastric carcinoma (EBVaGC).
Methods: Fas/FasL expression in 49 specimens of EBVaGC, 20 specimens of EBV-negative gastric carcinoma (EBVnGC) and 12 specimens of normal gastric mucosa was detected by immunohistochemistry. The apoptotic index (AI) of cells was determined by terminal deoxynucleotidyl transferase (TdT)-mediated dUTP-biotin nick end labeling (TUNEL).
Results: The positive rates of Fas were 91.7% in normal gastric mucosa and 76.8% in gastric carcinoma (P < 0.05); those of FasL were 16.7% in normal gastric mucosa and 58% in gastric carcinoma (P < 0.05). The positive rate of Fas was significantly lower in EBVaGC than in EBVnGC (71.4% vs. 90.0%, P < 0.05). The positive rate of FasL in EBVaGC was significantly higher than that in EBVnGC (63.2% vs. 45%, P < 0.05). The AI of EBVaGC cells was significantly lower than that of EBVnGC cells (P = 0.002). The number and AI of TIL in EBVaGC were higher than those in EBVnGC (P < 0.05). The AI of TIL was positively correlated with the level of FasL expression in tumor cells (r=0.237, P = 0.028).
Conclusion: Up-regulation of FasL expression and decrease of TIL apoptosis in EBVaGC may facilitate the escape of tumor cells from the host immunosurveillance, and it might contribute to the development and progression of carcinoma.