Effect And Mechanism Of IL-15Rα Expressed By Gastric Caninoma Cells On Cell Biological Behavior

Background and objectiveIL-15Rα is a specific receptor of IL-15.IL-15 binds to IL-15Rα which is expressed on cell surface to form IL-15/IL-15Rα complex.IL-15/IL-15Rα complex forms heteropolymer with IL-2Rβ and IL-2Rγ.IL-15 shows the same characteristics as IL-2 in receptor binding,signal transduction and biological effects.While IL-2 has been used in clinical treatment of renal cell carcinoma and melanoma,IL-15 has attracted much attention in immunotherapy of tumor.Except expressing on the surface of monocytes and dendritic cells,IL-15Rα is also detected in many non-lymphoid tissues,such as liver,heart,spleen,lung,skeletal muscle and endothelial cells.Gastric carcinoma is an important malignancy with high incidence and mortality in China.The analysis of TCGA database has shown that the expression of IL-15Rα in cancer lesion is significantly higher than paracancerous tissues.In addition,it has been reported that the expression of IL-15Rα in cells infected with EBV(AGS-EBV)is suppressed because of hypermethylated state.It is supposed that IL-15Rα may play an important role in gastric cancer.The purpose of this study is to understand the effect of IL-15Rα on the occurrence and development of gastric cancer and immunosuppressive therapy of gastric cancerthrough IL15/IL-15Rα signaling pathway.Methods1.The transcription level of IL-15Rα in gastric cancer lesionand adjacent tissue was analyzed by using TCGA profiling.The expression of IL-15Rα in gastric cancer cells was analyzed by RT-PCR and Western Blotting.2.The effects of IL-15Rα on the proliferation,invasion and migration of gastric cancer cells were detected by MTT cell proliferation test,cloning formation test,scratch test and transwell chamber test.3.RT-PCR and Western Blotting were used to detect mRNA and protein expression of IL-15Rα gene in gastric cancer cells which were treated with demethylation drug 5-Aza-CdR.MTT cell proliferation test and scratch test were used to detect the proliferation and migration of gastric cancer cells which were treated by5-Aza-CdR.4.MTT cell proliferation assay and cloning formation assay were used to detect the proliferation of gastric cancer cell streated with rhIL-15.Flow cytometry analysis examined the apoptosis rate of gastric cancer cells treated with rhIL-15,and the level of p-STAT5 inPBMC co-cultured with gastric cancer cells.Results1.The analysis of TCGA database showed that the mRNA level ofIL-15Rα in gastric cancer lesion was higher than adjacent tissue(P< 0.05).2.The protein expression level of IL-15Rα in gastric cancer AGS cells was significantly higher than that in AGS-EBV cells(P< 0.05).The proliferation,migration as well as invasion ability of AGS cells were higher than those of AGS-EBV cells(P< 0.05).3.Methyltransferase inhibitor 5-Aza-CdR inhibited the expression of IL-15Rαgene in gastric cancer cells and decreased the proliferation and migration ability of gastric cancer cells(P< 0.05).4.RhIL-15(100ng/mL)increased the proliferation ability and inhibited apoptosis of gastric cancer cells(P< 0.05).5.RhIL-15(100ng/mL)increased the activation of PBMC which was co-cultured with gastric cancer cells through IL-15/IL-15Rα signaling pathway(P<0.05).Conclusion1.The results of TCGA database suggest that IL-15Rα is highly expressed in gastric cancer tissues.IL-15Rα may be involved in the occurrence and development of gastric cancer.2.Proliferation,migration and invasion ability of AGS cells with higher expression of IL-15Rα is significantly higher than AGS-EBV cells with lower expression of IL-15Rα.Methyltransferase inhibitor 5-Aza-CdR inhibits the expression of IL-15Rα and decreases the proliferation as well as the migration ability of gastric3.cancer cells.It is suggested that the better prognosis of EBVaGC in clinicopathology may be related to the lower IL-15Rα expression.4.RhIL15 promotes proliferation of gastric cancer cells,it infers that the expression of IL-15Rα on tumor cells exhibits the potential to promote tumor progression in the absence of immune cell infiltration.While with immune cells infiltratration,exogenous IL-15 can activate PBMC co-cultured with gastric cancer cells by binding on IL-15Rα expressed by gastric cancer cells.It may be beneficial to IL-15 mediated immunosuppressive therapy.