Delivery of DNA-based cancer vaccine with polyethylenimine.

DNA-based vaccine directed to tumor-specific antigens is an attractive strategy in cancer prevention and therapy. In view of the poor immunogenicity of most tumor-associated antigens, studies were carried out here to examine the adjuvant effect of polyethylenimine (PEI), a cationic polymer widely used in non-viral gene delivery, on the efficacy of cancer vaccine strategy. Treatment of animals with the DNA/PEI complexes resulted in antigen-specific cell lysis and activation of B3Z cells, an ovalbumin/K(b)-specific cytotoxic clone that recognizes the target cells through the class I major histocompatibility complex (MHC) molecules. Immunohistochemical examination showed that PEI-mediated DNA vaccination induced cell death and significant lymphocyte infiltration at the injection sites. Immunization of C57BL/6J mice with the DNA/PEI complexes either preceded or after tumor cell inoculation suppressed tumor growth and prolonged the survival rate of the animals. Results obtained in this study illustrated the potential use of PEI as an adjuvant in DNA-based cancer vaccination for induction of protective and therapeutic immunity.