Fas/Fas ligand system and apoptosis induction in testicular carcinoma

BACKGROUND Tumor‐infiltrating, Fas ligand (FasL)‐expressing lymphocytes are able to eliminate Fas‐bearing tumor cells by apoptosis induction. Activated cytotoxic T‐cells that express Fas may enter apoptosis in the presence of FasL tumor cells. To date, no studies of patients with testicular carcinoma have correlated the differential expression of Fas and FasL in both cell types with the corresponding apoptotic index (AI). METHODS Fas and FasL were investigated immunohistochemically in paraffin embedded tissue sections from 25 patients with nonseminomatous testicular tumors. The percentages of positive cells and the ratios of Fas cells to FasL cells were correlated with the AI of tumor cells and lymphocytes, respectively, using Spearman correlations. RESULTS No association was found between the rate of FasL positive cells and AI of the other cell type or between the rate of Fas positive cells and the AI of the same cell type. Ratios between Fas positive cells and FasL positive cells were not correlated with the AI; however, a significant positive correlation was found between the AI of tumor cells and the AI of lymphocytes. CONCLUSIONS It seems unlikely that the Fas/FasL system is responsible for immune escape of the tumor in testicular carcinoma. Rather, the significant positive correlation between the AIs of tumor cells and lymphocytes implicate a previously unknown mechanism of apoptosis induction in both cell types. Cancer 2002;95:73–81. © 2002 American Cancer Society. DOI 10.1002/cncr.10649 In this study, the authors postulated that the interaction between tumor‐infiltrating lymphocytes and tumor cells in terms of apoptosis induction is mediated by the Fas/Fas ligand (FasL) system in many types of tumors. No correlation between the level of Fas or FasL expression and the apoptotic index (either in lymphocytes or in tumor cells) was found in tissue sections from patients with testicular nonseminomatous tumors.