Allogeneic Tumor Vaccine Produced by Electrofusion between Osteosarcoma Cell Line and Dendritic Cells in the Induction of Antitumor Immunity

Objective: Fusion of dendritic cells, DCs, with tumor cells is an effective approach for delivering tumor antigens to DCs, and DC-tumor fusion cells are potent stimulators of T cells. However, the integration of allogeneic DC-osteosarcoma fusion cells has not been fully examined. This study was designed to investigate the antitumor effects of tumor vaccine produced by electrofusion between rat osteosarcoma cells and allogeneic DCs. Methods: In the present study, we eletrofused Wistar rat bone marrow-derived DCs to SD rat osteosarcoma cells (UMR106) and purified them by monoclonal antibody OX62 and magnetic beads. Coculture of SD or Wistar bone marrow derived T lymphocytes with DC-tumor fusion cells resulted in activation of T cells, and the proportion of CD8+, CD4+ cells was determined using flow cytometry. Then cytotoxic T lymphocytes, CTLs, assay was assessed according to results of MTT assay. Results: After T cells were cultured with allogeneic DC-osteosarcoma fusion cells, DOF, and effective activation of T cells was observed. The proportion of CD8+ cells in the SD T cell group increases from 34.16% before induction to 74.85%, while that of CD4+ cells is from 63.35% to 71.75% in Wistar T cell group. The immunization using allogeneic DC-osteosarcoma vaccine induced UMR106-spcific CTL responses which were statistically significant (P < 0.05) and the cytotoxic activity was inhibited by the treatment with anti-CD8 and anti-MHC-class I monoclonal antibodies but not with anti-CD4 and anti-MHC-class II antibodies. Conclusion: The present study provided valid evidence of integration of rat allogeneic DCs electrofused with tumor cells and analyzed their properties in T cell activation. The fusion cells may thus represent a promising strategy for DC-based immunotherapy of patients with osteosarcoma.