Induction of apoptosis in glioma cells by recombinant human Fas ligand

OBJECTIVE: Fas ligand (FasL) belongs to the tumor necrosis factor family and has the ability to induce apoptosis in susceptible target cells by binding to its receptor, Fas. It has been demonstrated recently that the FasL/Fas system plays a pivotal role in the cytocidal activity of T lymphocytes in the immune system. Fast may act as a cytotoxic effector molecule to Fas-expressing malignant tumor cells. We reported previously that Fas is commonly expressed in human brain tumor cells. In this study, we examine the possible application of Fast to therapy for malignant brain tumors. METHODS: To develop an expression system yielding large amounts of Fast, we constructed a baculovirus vector containing complementary deoxyribonucleic acid of human Fast under the control of a polyhedrin promoter. We produced human Fast in Spodoptera frugiperda (Sf9) insect cells infected by the recombinant baculovirus carrying Fast complementary deoxyribonucleic acid and studied the cytocidal activity of Fast against the T98G human glioblastoma cell line. RESULTS: Fast expression in Sf9 cells was confirmed immunocytochemically with rabbit antibody raised against the cytoplasmic domain of human Fast. The Fast released into the supernatant of cultured Sf9 cells was also verified by Western blotting, and it specifically induced apoptosis in T98G cells. The induced apoptosis by recombinant human Fast was confirmed by annexin V-fluorescein isothiocyanate staining. CONCLUSION: The present results suggest that the induction of apoptosis by the Fas/FasL system could be a new strategy for the treatment of malignant brain tumors, which ave resistant to conventional therapies.