Abstract: Objective To investigate the effect of renal cancer cell exosome on CD8⁺T cell tumor killing fuction. Methods HK-2 exo,786-O exo,SN12-PM6 exo,and an equal volume of PBS were co-cultured with CD8⁺T cells,cytotoxicity assay was used to detect the killing function of CD8⁺T cells.ELISA was used to detect the secretion of IFN-γ,IL-2 and TNF-α.Western blotting was used to detect the expression level of PD-1 in CD8⁺T cells.CD8⁺T cell transfected PD-1 siRNA(si-PD-1)and siRNA Negative Control(si-NC)were co-incubated with 786-O exo and SN12-PM6 exo for 24 hours,respectively.Cytotoxicity experiments were conducted to detect the cytotoxicity of CD8⁺T cells against 786-O and SN12-PM6 cells after transfection. Results Compared with those in the PBS group,the secretion of IFN-γ,IL-2 and TNF-α in the 786-O exo group and SN12-PM6 exo group were significantly downregulated(P<0.05).The ability to kill 786-O and SN12-PM6 was significantly reduced(P<0.05),and PD-1 protein expression level was significantly upregulated(P<0.05).After co-incubation with 786-O exo and SN12-PM6 exo,the the secretion of IFN-γ,IL-2 and TNF-α,as well as the ability to kill 786-O and SN12-PM6 were significantly increased when compared with those in the CD8⁺T cells transfected with si-NC(P<0.05). Conclusion Renal cancer exosome can induce the expression of PD-1 of CD8⁺T cells to inhibit the tumor killing function.

Key words: renal cancer, exosome, CD8⁺T cells, programmed death-1