Abstract B116: Adjuvant-mediated DNA immunotherapy for cancer

Abstract

Abstract B116 Cancer immunotherapy invokes immunity against cancerous cells by stimulating the immune response from the host. In an attempt to investigate the effect of adjuvant-mediated therapy, polyethyleneimine (PEI), a nonviral polycationic gene delivery vector, was employed in this study as an adjuvant to investigate the immunostimulatory effect on the murine bone marrow-derived dendritic cells (BMDCs) and in the tumor-bearing animals. The physicochemical properties of the DNA-PEI complexes was characterized by the size and surface potential measurements. Murine bone-marrow-derived dendritic cells (BMDCs) at day 6 were treated with DNA-PEI complexes at various DNA/PEI ratios, followed by flow cytometric analysis of the expression of costimulatory molecules, including CD40, CD80, and CD86, at 24 h post-treatment. The production of the reactive oxygen species (ROS) after treatment with the PEI in the BMDCs was assessed with 2',7'-dichlorofluorescein diacetate (DCFH-DA) and hydroethidine (HE), followed by flow cytometry. To determine the effect of adjuvant on immunotherapeutic response, approximately 2 x 105 B16F10 melanoma cells were inoculated s.c. on the back of C57BL/6. Control groups were injected with PBS. When the tumor sizes reached 100 mm3 on day 6 after inoculation of B16F10 cells, animals were treated with the PEI-DNA complexes, containing the IL2 or caspase (fusion of caspase-2 prodomain and amino-terminal truncated caspase-3) plasmid DNA. Tumor sizes were measured with a caliper, and the volumes were determined using the formula of (length x width2)/2. Each group contained 4 animals. Results obtained in this study demonstrated that treatment of BMDCs with PEI or LPS impaired the endocytic activity of BMDCs, and upregulated the expression of the costimulatory molecules, such as CD40 and CD86, suggesting the induction of maturation by PEI on the BMDCs. Treatment of BMDCs with the DNA-PEI complexes also lead to a concentration-dependent production of the reactive oxygen species (ROS), implicating the adjuvant function of PEI on immunostimulation. Injection of the animals with IL-2 or caspase plasmid DNA, complexed with PEI, was able to induce significant inhibition of the growth of tumors in the tumor-bearing animals. These results demonstrated the prevention and therapeutic effect of adjuvant-mediated DNA immunotherapy in the murine melanoma model. Citation Information: Cancer Prev Res 2008;1(7 Suppl):B116.