Combined TLR stimulation with Pam3Cys and Poly I: C enhances Flt3-ligand dendritic cell activation for tumor immunotherapy

J Immunother. 2012 Nov-Dec;35(9):670-9. doi: 10.1097/CJI.0b013e318270e135.


The cytokines granulocyte macrophage colony-stimulating factor (GM-CSF) and interleukin (IL)-4 are frequently used for generating dendritic cells (DCs) for therapeutic vaccination against cancer. These in vitro DCs share several characteristics with inflammatory monocyte-derived DCs in vivo. In contrast, culture of bone marrow cells in Flt3-ligand (Flt3L) generates a heterogeneous population of DCs, which comprise conventional DCs (cDCs) and plasmacytoid DCs similar to the steady-state populations found in vivo. Although previous studies have identified combinations of toll-like receptor ligands (TLR-Ls) that induce optimal activation of GM-CSF/IL-4 DCs in vitro, the conditions for optimal activation of Flt3L-DCs have not been established. In this study, we show that various combinations of the TLR-Ls Pam3Cys, Poly I:C, lipopolysaccharide, and CpG all increased Flt3L-DC maturation, but only the combination of Pam3Cys/Poly I:C showed a trend to enhanced production of IL-12p70 and tumor necrosis factor-α by cDCs. Pam3Cys/Poly I:C-treated cDCs also displayed enhanced capacity to present antigen to CD4(+) T cells, and cross-present to CD8(+) T cells, increasing T-cell proliferation in vitro. Within a prophylactic vaccination setting, cDCs activated with Pam3Cys/Poly I:C conferred tumor protection in mice. However, the numbers of cDCs required for protection were higher than the numbers of optimally activated GM-CSF/IL-4 DCs required for a similar effect. Our results show that combined TLR stimulation can enhance both the phenotypic and functional properties of Flt3L-DCs, but even under conditions of optimal activation these cells are not superior in activity to GM-CSF/IL-4 DCs in vivo.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cancer Vaccines
  • Cytokines / metabolism
  • Dendritic Cells / drug effects
  • Dendritic Cells / immunology*
  • Dendritic Cells / metabolism*
  • Granulocyte-Macrophage Colony-Stimulating Factor / pharmacology
  • Immunotherapy*
  • Inflammation Mediators / metabolism
  • Interleukin-4 / pharmacology
  • Lipoproteins / pharmacology
  • Lymphocyte Activation / drug effects
  • Lymphocyte Activation / immunology
  • Membrane Proteins / metabolism*
  • Mice
  • Neoplasms / immunology*
  • Neoplasms / mortality
  • Neoplasms / therapy*
  • Poly I-C / pharmacology
  • T-Lymphocytes / drug effects
  • T-Lymphocytes / immunology
  • Toll-Like Receptors / agonists
  • Toll-Like Receptors / metabolism*


  • Cancer Vaccines
  • Cytokines
  • Inflammation Mediators
  • Lipoproteins
  • Membrane Proteins
  • Toll-Like Receptors
  • flt3 ligand protein
  • N-palmitoyl-S-(2,3-bis(palmitoyloxy)propyl)cysteinyl-seryl-lysyl-lysyl-lysyl-lysine
  • Interleukin-4
  • Granulocyte-Macrophage Colony-Stimulating Factor
  • Poly I-C