| Tumor necrosis factor-related apoptosis inducing ligand (TRAIL) is a member of the super family of tumor necrosis factor(TNF), which can induce apoptosis for tumor cells but cause no significant side effects for the normal cells. So great expectations have been put on the perspective for its role in cancer treatment. However during recent years, some documents reported that some tumors were not sensitive or even tolerant to TRAIL. So how to increase the anti-tumor activity or overcome the drug resistance for TRAIL still remains to be a hot spot in research works. In our investigation, we observed both the synergetic anti-tumor effect and the toxicity for the normal fibroblast by using TRAIL combined with IFN- γ.Also we tried to elucidate the mechanism for this synergetic effect preliminarily.We hoped our work could provide someopinions for future research on the tolerance for TRAIL and the reversion or sensitization for this tolerance.Material and MethodsThe MG~63 cell line and the NHF was respectively offered by Cancer Research Institution of Zhejiang university and the Central Laboratory of Sir Run Run Shaw Hospital .The equipment used in this task was provided by the Lab.The reagent was purchased through the Lab. The morphology was observed with inverted phase contrast microscope and electronic microscope after MG-63 was treated by TRATL (0, 50, 100, 500, 1000, 2000 ng/ml for 24 hours), IFN-Y500u/ml (for 0, 6, 12, 24, 48, 72 hour), and after IFN-y500u/ml (for 0, 6, 12, 24, 48, 72 hour) combined with TRAIL lOOOng/ml. Respectively inhibition rate and apoptosis rate was observed by MTT assay and FCM. After MG-63 was intervented by IFN- Y, TRAIL receptor expression was detected by RT-PCR. The toxicity of IFN-Ycombined with TRAIL in NHF was observed by MTT assay.ResultThe growth activity of MG-63 was declined when it was intervented by TRAIL, observeing by inverted phase contrast microscope. The higher the concentration of TRAIL was, the lower the activity was. When the tumor cells was treated by IFN- Y for 24 hours, then combined with TRAIL lOOOng/ml for 24 hours, it showedthe lowest activity. The Electronic microscope could reveal the apoptosis characteristic change. The inhibition rate of MG-63 increased from 2.1% to 89. 2% as the concentration of TRAIL increased. When the concentration was lOOOng/ml, the inhibition rate was 57.4%. The kill power of IFN-ywas not strong , the maximum inhibition rate was 26.6%. However, the inhibition rate increased obviously by combinating IFN-yand TRAIL while compared with administration of TRAIL or IFN-y alone, the difference was statistically significant (P< 0. 01). The apoptosis rate of MG-63 observed with FCM was 3. 350+1. 08, 49. 367 ±5.45, 14.386 + 2.14, 73. 867+2. 01, when it was treated without any reagent, TRAIL lOOOng/mlfor 24 hours, IFN- y 500u/ml for 24 hours, and after IFN-y 500u/ml for 24 hours combined with TRAIL lOOOng/ml 24 hours respectively .The expression of Death receptor (DR4) detected by quantitive RT-PCR was increased significantly (P<0. 01) when MG-63 was treated with IFN- y for 24 hours. But the expression of DcR2 and DR5 did not increase obviously (P>0. 05). The toxicity of IFN-y combined with TRAIL in normal fibroblast was not increased notably (P >0. 05), compared with TRAIL administration alone.ConclusionIn our investigation, IFN-y could enhance the apoptosis inducing effect of tumor necrosis factor-related apoptosis inducing ligand (TRAIL) inosteosarcoma cell line. Upregulating DR4 might be one of the reasons for synergetic antitumor activity. The risk of toxicity was not raised in NHF when combinating IFN- y with TRAIL.
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