Optimal culture conditions for the generation of natural killer cell-induced dendritic cells for cancer immunotherapy.

Dendritic cell (DC)-based vaccines continue to be considered an attractive tool for cancer immunotherapy. DCs require an additional signal from the environment or other immune cells to polarize the development of immune responses toward T helper 1 (Th1) or Th2 responses. DCs play a role in natural killer (NK) cell activation, and NK cells are also able to activate and induce the maturation of DCs. We investigated the types of NK cells that can induce the maturation and enhanced function of DCs and the conditions under which these interactions occur. DCs that were activated by resting NK cells in the presence of inflammatory cytokines exhibited increased expression of several costimulatory molecules and an enhanced ability to produce IL-12p70. NK cell-stimulated DCs potently induced Th1 polarization and exhibited the ability to generate tumor antigen-specific cytotoxic T lymphocyte responses. Our data demonstrate that functional DCs can be generated by coculturing immature DCs with freshly isolated resting NK cells in the presence of Toll-like receptor agonists and proinflammatory cytokines and that the resulting DCs effectively present antigens to induce tumor-specific T-cell responses, which suggests that these cells may be useful for cancer immunotherapy.

Induction of myeloma-specific cytotoxic T lymphocytes responses by natural killer cells stimulated-dendritic cells in patients with multiple myeloma.

The interaction between dendritic cells (DCs) and natural killer (NK) cells plays a key role in inducing DC maturation for subsequent T-cell priming. We investigated to generate potent DCs by stimulated with NK cells to induce myeloma-specific cytotoxic T lymphocytes (CTLs). NK cells-stimulated-DCs exhibited high expression of costimulatory molecules and high production of IL-12p70. These DCs induce high potency of Th1 polarization and exhibit a high ability to generate myeloma-specific CTLs responses. These results suggest that functionally potent DCs can be generated by stimulation with NK cells and may provide an effective source of DC-based immunotherapy in multiple myeloma.

Type I and II interferons enhance dendritic cell maturation and migration capacity by regulating CD38 and CD74 that have synergistic effects with TLR agonists.

The major limitation for the maturation of dendritic cells (DCs) using Toll-like receptor (TLR) agonists is their decreased ability to migrate into lymph nodes compared with conventional DCs. CD38 can be used as a multifunctional marker to modulate migration, survival and Th1 responses of DCs. CD74 has been shown to negatively regulate DC migration. The goal of this study was to investigate the combinations of TLR agonists and interferons (IFNs) that most effectively regulate CD38 and CD74 expression on DCs. Synergistic TLR agonist stimulation in combination with IFN-α and IFN-γ was the best method for regulating CD38 and CD74 expression and inducing the highest secretion of IL-12p70. An in vitro migration assay showed that DCs treated with this combination had significantly enhanced migratory ability, similar to that observed in cells expressing CD38, CD74 and CCR7. The results of this study suggest that an alternative maturation protocol in which two TLR ligands are combined with type I and II IFNs generates potent DCs that have both a high migratory capacity and high IL-12p70 production.

Enhancement of antitumor effect using dendritic cells activated with natural killer cells in the presence of Toll-like receptor agonist.

Dendritic cells (DCs) play a role in natural killer (NK) cell activation, while NK cells are also able to activate and mature DCs. Toll-like receptors (TLRs) on the surface of DCs and NK cells induce the maturation and activation of these cells when engaged with their cognate ligand. We investigated to generate potent DCs by maturation with NK cells in the presence of TLR agonist in vitro and tested the efficacy of these DC vaccinations in mouse colon cancer model. The optimal ratios of DCs versus NK cells were 1:1 to 1:2. Immature DCs were mature with NK cells in the presence of lipopolysaccharide, which is TLR4 agonist, and further addition of IL-2 induced phenotypically and functionally mature bone marrow-derived DCs. These potent DCs exhibited not only high expression of several costimulatory molecules and high production of IL-12p40 and IL-12p70, but also high allogeneic T cells stimulatory capacity, and the induction of the high activities to generate tumor-specific CTLs. Consistently, vaccination with these DCs efficiently inhibited CT-26 tumor growth in mouse colon cancer model when compared to other vaccination strategies. Interestingly, combination therapy of these DC-based vaccines and with low-dose cyclophosphamide showed dramatic inhibition effects of tumor growth. These results suggest that the DCs maturated with NK cells in the presence of TLR agonist are potent inducer of antitumor immune responses in mouse model and may provide a new source of DC-based vaccines for the development of immunotherapy against colon cancer.