Enhanced transgene expression and effective in vivo antitumor immune responses initiated by dendritic progenitors transfected with a nonviral T7 vector expressing a model tumor antigen

Genetic education of dendritic cells (DCs) with tumor-associated antigens i s an encouraging development in DC-mediated tumor immunotherapy. In this st udy, to increase the transgene expression by DCs using nonviral vectors, a cytoplasmic T7 vector (T7T7/T7Luc) was used to transfect bone marrow-derive d DCs with the firefly luciferase gene as a reporter and as a model tumor a ntigen. As a result, the luciferase activity of T7T7/T7Luc-transfected DCs was more than four times greater than that of DCs transfected with pCMVLuc, a commonly used nonviral vector. Furthermore, the luciferase activity was increased three times more when dendritic progenitor cells rather than matu re DCs were transfected. In vivo tumor studies showed that T7T7/T7Luc-trans fected DCs, which express high levels of luciferase (model tumor antigen), stimulated a stronger immune response than did pCMVLuc-transfected DCs, whi ch express relatively low levels of luciferase, as indicated by the cytotox ic T lymphocyte assay. T7T7/T7Luc transfected DCs, when injected into recip ient mice, evoked an antigen-specific immune response that can effectively eradicate implanted metastasis and prevent new tumor development by murine melanoma cells genetically modified to express luciferase. Therefore, the T 7 system is a powerful nonviral vector that can be used to genetically educ ate DCs with tumor-associated antigens for tumor immunotherapy.