Possible involvement of Fas system in the induction of apoptosis in human astrocytic brain tumors.

1. For a better understanding of the biological features of astrocytic tumors, we investigated apoptosis and its pathway, especially in the interaction between Fas and Fas ligand (FasL). 2. We examined the presence of apoptosis in human astrocytic brain tumors by terminal deoxynucleotidyl transferase (TdT)-mediated d-UTP-biotin nick end labeling (TUNEL) and then apoptotic index (AI) was calculated. We also examined the distribution of Fas and FasL-positive tumor cells immunohistochemically. Labeling index (LI) for Fas and FasL was calculated as Fas-LI and FasL-LI, respectively, and compared to AI. 3. Tumor cells expressing both Fas and FasL were TUNEL positive. Such cells were distributed sparsely in low-grade astrocytomas, but focally in glioblastomas. There was a close correlation among AI, Fas-LI, and FasL-LI, and astrocytic tumors with higher Al were associated with a longer survival time than that with lower Al. 4. It was concluded that the Fas system may be involved in the apoptosis of astrocytic tumors, and Al can be a useful parameter for assessing prognosis of astrocytic tumors.