Anti-tumoral capabilities of effector cells after IFN-alpha or CpG-motif treatment of cocultured dendritic cells.

INTRODUCTION: Ex vivo expansion of monocyte-derived dendritic cells (mDCs) and subsequent coculture with autologous cytokine-induced killer (CIK) cells is an established system to create specific and non-specific anti-tumoral immunity. mDCs constitute the most frequently applied DC subset in clinical studies. One recently published approach to optimize the immunological functions of the DC/CIK cell system is the replacement of interleukin (IL)-4 by interferon (IFN)-alpha in the maturation process of the DCs. MATERIALS AND METHODS: The expressions of relevant surface antigens of IL-4-DCs and IFNalpha-DCs by flow cytometry and the anti-tumoral activation of effector cells cocultured with both types of DCs using cytotoxicity assays were compared. In addition, short-term coculture experiments with both types of DCs and IFNgamma-LAK effector cells were performed and compared with standard CIK cell coculture experiments. RESULTS: Regarding the expressions of functionally relevant surface markers, no differences could be detected for CD80, CD83, and HLA-DR between IFNalpha-DCs and IL-4-DCs, whereas the mean fluorescence intensities of CD40, CD86, CD54, and HLA-ABC were decreased and the expression of CD14 was increased for IFNgamma-DCs. Moreover, no enhancement of cytotoxicity of cocultured CIK cells against tumor cell lines (A498 and SW480) was detected by the use of IFNalpha-DCs. Additionally, coculture experiments with IFNgamma-LAK cells were performed and unexpectedly higher lysis rates in comparison with the established IL-4-DC/CIK coculture model was observed. Early incubation of the mDCs with several CpG-ODNs failed to increase the anti-tumoral cytotoxicity of the cocultured IFNgamma-LAK cells. CONCLUSIONS: These results demonstrate that in the mDC/CIK cell system, IFNalpha-DCs are not superior in inducing anti-tumoral cytotoxicity and even moderately inferior regarding the expression of functionally relevant surface markers compared with IL-4-DCs.

Transfection of human monocyte-derived dendritic cells with CpG oligonucleotides.

Monocyte-derived dendritic cells (mDC), the most frequently applied DC subset in clinical studies, which can be obtained easily from peripheral blood monocytes after incubation with GM-CSF and IL-4, have not been clearly demonstrated to be activated by CpG oligodeoxynucleotides (ODN). The development of novel molecular strategies - such as the use of CpG-ODN - to increase immunological functions and thus improve the therapeutic efficiency of mDC vaccines in the treatment of malignant diseases is highly desirable. CpG-ODN need to be internalized into specific intracellular compartments to be active. Therefore, we applied electroporation and lipofection and compared these techniques with incubation to overcome possible defects in localization. Conditions of CpG-ODN transfection of these cells were optimized using fluorescein-marked ODN 2216. We were able to achieve high transfection efficiencies with various methods of delivery. However, we did not observe increased expression of maturation-associated and functionally relevant surface antigens (CD14, HLA-DR, CD40, CD83, CD80 and CD86), significant secretion of IL-12 and IFN-alpha in culture supernatant, or enhanced antitumour activation of cytokine-induced killer cells. In conclusion, our results show that non-viral transfection of CpG-ODN is not sufficient to overcome resistance of mDC to CpG activation.