IFN-γ enhances the anti-tumor effect of TRAIL against giant cell tumor of bone in vitro

Objective:To explore the anti-tumor effect of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) against giant cell tumor of bone (GCT), and to study the influence of IFN-γ on the anti-tumor effects of TRAIL and the possible mechanisms. Methods:Fresh specimens were obtained from 9 patients who were pathologically diagnosed as having GCT in the orthopaedics department of No. 301 Hospital PLA from 2003 to 2006. The GCT cells from specimens were divided into 4 groups: control group, TRAIL group, IFN-γ group and IFN-γ plus TRAIL group. The cell inhibition was examined by CCK-8 assay. Cell apoptosis was detected by flow cytometric analysis and TUNEL assays. RT-PCR was applied to semi-quantitatively assay the mRNA expression of TRAIL, DR4 and DR5 in GCT cells before and after the treatment with IFN-γ (500 U/ml). Results: The GCT cell survival rate was (98.64±0.31)% in the control group. TRAIL alone (100, 500,1 000 μg/L) had no obvious effect on tumor cell proliferation. After treatment with IFN-γ at 500 and 1 000 U/ml, the tumor cell survival rates were (94.05±1.89) % and (90.47±2.66) %, respectively. After treatement with IFN-γ(500 U /ml) and TRAIL (100,200 μg/L), the tumor cell survival rates were (84.65±2.46)% and (77.65±3.14)%, respectively; and FCM showed that their apoptosis rates were (27.94±2.88)% and (38.65±2.46)%, respectively; the apoptosis rate was (1.77±0.49)% in the control group. TUNEL revealed that the apoptosis rates were (19.63±3.51)% and (29.28±4.80)% , respectively; and the rate was (1.1±0.17)% in the control group. RT-PCR showed that the expression levels of TRAIL, DR4 and DR5 in tumor cells were up-regulated after treatment with IFN-γ (500 U /ml) for 24 h. Conclusion: GCT cells are not sensitive to TRAIL. IFN-γ can up-regulate the apoptosis rate of GCT cells induced by TRAIL, which might be associated with the up-regulation of TRAIL,DR4 and DR5 mRNA expression by IFN-γ.