IFN­ß sensitizes TRAIL­induced apoptosis by upregulation of death receptor 5 in malignant glioma cells.

ABSTRACT

Tumor necrosis factor­related apoptosis­inducing ligand (TRAIL), a member of the tumor necrosis factor (TNF) family, induces apoptosis in cancer cells by binding to its receptors, death receptor 4 (DR4) and DR5, without affecting normal cells, and is therefore considered to be a promising antitumor agent for use in cancer treatment. However, several studies have indicated that most glioma cell lines display resistance to TRAIL­induced apoptosis. To overcome such resistance and to improve the efficacy of TRAIL­based therapies, identification of ideal agents for combinational treatment is important for achieving rational clinical treatment in glioblastoma patients. The main aim of this study was to investigate whether interferon­ß (IFN­ß) (with its pleiotropic antitumor activities) could sensitize malignant glioma cells to TRAIL­induced apoptosis using glioma cell lines. TRAIL exhibited a dose­dependent antitumor effect in all of the 7 types of malignant glioma cell lines, although the intensity of the effect varied among the cell lines. In addition, combined treatment with TRAIL (low clinical dose 1 ng/ml) and IFN­ß (clinically relevant concentration 10 IU/ml) in A­172, AM­38, T98G, U­138MG and U­251MG demonstrated a more marked antitumor effect than TRAIL alone. Furthermore, the antitumor effect of the combined treatment with TRAIL and IFN­ß may be enhanced via an extrinsic apoptotic system, and upregulation of DR5 was revealed to play an important role in this process in U­138MG cells. These findings provide an experimental basis to suggest that combined treatment with TRAIL and IFN­ß may offer a new therapeutic strategy for malignant gliomas.