The Study Of The Anti-tumor Effects And Mechanisms Of Murine Interleukin-21-Tumor Vaccine In Mice

Objective: To construct tumor vaccine expressed murine interleukin(IL)-21 stably and evaluate its anti-tumor effects and possible mechanisms in mice.Methods: The identified recombinant plasmid (pcDNA3.1/mIL-21) is transfected into SP2/0 cells via lipofectamine. The expression of mIL-21 is detected by RT-PCR. The molecules of MHC-Ⅰ, CD80 on the tumor vaccine surface and the proliferation of tumor cells in vitro reflected the cell cycle in vitro were respectively detected by flow cytometry(FCM). The anti-tumor effects were evaluated from surveying the tumor growth state after the tumor vaccine was inoculated into s.c Balb/c mice. We use a flow cytometric CFSE-7-AAD cytotoxicity assay to detect the cytotoxic activities of NK and CTLs. The I-TAC, one of CXC-chemokine family, its expression in the tumor tissue was tested by RT-PCR.The levels of serum IFN-γand IL-4 in mice are measured by ELISA. The mice without growth tumor were rechallenged with SP2/0 cells. The anti-tumor mechanisms were investigated according to above methods and index.Results: The SP2/0-mIL-21 tumor vaccine expressing mIL- 21 is successfully constructed. The expression of the MHC-Ⅰmolecule on its surface is up-regulated obviously. The tumors develop slowly in Balb/c mice injected with tumor vaccine compared with the control mice injected with SP2/0 and SP2/0-pcDNA cells. Some of those mice immunized with SP2/0-mIL-21 tumor vaccine even live for a long time without tumors. The mice without tumor are rechallenged with SP2/0 cells. After 4 weeks, there is still no tumor growth in 75% of those mice. The cytotoxic activities of NK and CTLs are enhanced in mice immunized with tumor vaccine. The expression of I-TAC in the tumor tissue is detectable by RT-PCR. The level of IFN-γis higher in mice inoculated with tumor vaccine than that of control mice, but no difference is found in the levels of IL-4 between the mice inoculated with tumor vaccine and the control mice.Conclusion: The SP2/0 mIL-21-tumor vaccine is successfully constructed. It can induce strong cell-mediated immune response to tumor cells and play an important anti-tumor effect after it was inoculated s.c into mice. The results suggest that the SP2/0mIL-21 tumor vaccine has a higher immunogenicity and lower tumorigenesis than that of the SP2/0 cells and that the tumor vaccine modified with mIL-21 gene has more wide useful prospect in anti-tumor immunotherapy.