OBJECTIVE To observe enhancement of anti-tumor immunity by gene vaccine using nucleofection technologyMETHODS The technique of nucleofection was used to transfer effectively plasmid DNA into immature dendritic cells (iDCs); we studied immune responses regulated by DNA vaccine using real-time quantitative polymerase chain reaction (PCR) and western-blotting to optimize the follow-up lymphocyte activation. The anti-tumor capacity of lymphocytes primed by DCs was analyzed using lactate dehydrogenase with a non-radioactive cytotoxicity assay.RESULTS Human monocyte-derived dendritic cells (hMoDCs) were induced by interleukin (IL)-4 and granulocyte-macrophage colonystimulating factor (GM-CSF) in vitro from human monocytes for 5 or 6 days. DNA vaccine was transfected to iDCs with high transfection (35.73%) using nucleofection. Compared with the iDC group, the expression of Th1 cell cytokine IL-12, IL-18 and Th2 cell cytokine IL-4 increased after stimulation. CD86 and CD83 were upregulated compared with non-nucleofected groups 48 hours after nucleofection with DC-pVAX-PRA. The result of the cytotoxicity assay showed that DCs-pVAX-PRA primed non-adherent peripheral blood mononuclear cells (PBMCs) exhibit their highest cytotoxicity against target cells.CONCLUSION The results show that DNA vaccine was transfected to iDC with high transfection efficiency using nucleofection, priming autologous lymphocytes for anti-tumor immunity by upregulated expression of co-stimulatory molecules, adhesion molecules and cytokines. These results provided a basis to explore the molecular mechanism of DNA vaccine in vivo.