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Dual activation of Toll-like receptors 7 and 9 impairs the efficacy of antitumor vaccines in murine models of metastatic breast cancer



Since combination of Toll-like receptor (TLR) ligands could boost antitumor immunity, we evaluated the efficacy of dendritic cell (DC) vaccines upon dual activation of TLR9 and TLR7 in breast cancer models.


DCs were generated from mouse bone marrow or peripheral blood from healthy human donors and stimulated with CpG1826 (mouse TLR9 agonist), CpG2006 or IMT504 (human TLR9 agonists) and R848 (TLR7 agonist). Efficacy of antitumor vaccines was evaluated in BALB/c mice bearing metastatic mammary adenocarcinomas.


CpG-DCs improved the survival of tumor-bearing mice, reduced the development of lung metastases and generated immunological memory. However, dual activation of TLRs impaired the efficacy of DC vaccines. In vitro, we found that R848 inhibited CpG-mediated maturation of murine DCs. A positive feedback loop in TLR9 mRNA expression was observed upon CpG stimulation that was inhibited in the presence of R848. Impaired activation of NF-κB was detected when TLR9 and TLR7 were simultaneously activated. Blockade of nitric oxide synthase (NOS) and indoleamine-pyrrole-2,3-dioxygenase (IDO) improved the activation of CpG-DCs. When we evaluated the effect of combined activation of TLR9 and TLR7 in human DCs, we found that R848 induced robust DC activation that was inhibited by TLR9 agonists.


These observations provide insight in the biology of TLR9 and TLR7 crosstalk and suggest caution in the selection of agonists for multiple TLR stimulation. Blockade of NOS and IDO could improve the maturation of antitumor DC vaccines. R848 could prove a useful adjuvant for DC vaccines in human patients.

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This work was supported by Consejo Nacional de Investigaciones Científicas y Tecnológicas (CONICET PIP 114-201101-00353 to M.C.; PIP 11220120100261 to A.S.); Doctoral Fellowship to M.A.M.A. and M.F.G.); Agencia Nacional de Promoción Científica y Tecnológica (PICT-2012-0830; PICT-2013-0310, PICT-2015-3309 to M.C.; PICT 2014-0334 to A.S.); Fundación Bunge y Born (“Jorge Oster” fellowship to M.A.M.A) and Liga Argentina de Lucha contra el Cáncer (LALCEC, “Jorgelina Ortiz De Rozas De Alvarez” fellowship to M.A.M.A.). We wish to thank Dr Alejandro Montaner (Instituto Milsten, CONICET, Argentina) who kindly provided human TLR9 agonists.

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Correspondence to Marianela Candolfi.

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This study was funded by Consejo Nacional de Investigaciones Científicas y Tecnológicas (CONICET PIP 114-201101-00353 to M.C.; PIP 11220120100261 to A.S.); Doctoral Fellowship to M.A.M.A. and M.F.G.); Agencia Nacional de Promoción Científica y Tecnológica (PICT-2012-0830; PICT-2013-0310, PICT-2015-3309 to M.C.; PICT 2014-0334 to A.S.); Fundación Bunge y Born (“Jorge Oster” fellowship to M.A.M.A) and Liga Argentina de Lucha contra el Cáncer (LALCEC, “Jorgelina Ortiz De Rozas De Alvarez” fellowship to M.A.M.A.).

Conflict of interest

Author Mariela A. Moreno Ayala declares that she has no conflict of interest. Author María Florencia Gottardo declares that she has no conflict of interest. Author María Soledad Gori declares that she has no conflict of interest. Author Alejandro Nicola declares that he has no conflict of interest. Author Carla Caruso declares that she has no conflict of interest. Author Andrea De Laurentiis declares that she has no conflict of interest. Author Mercedes Imsen declares that she has no conflict of interest. Author Slobodanka Klein declares that she has no conflict of interest. Author Elisa Bal de Kier Joffé declares that she has no conflict of interest. Author Gabriela Salamone declares that she has no conflict of interest. Author Maria G. Castro declares that she has no conflict of interest. Author Adriana Seilicovich declares that she has no conflict of interest. Author Marianela Candolfi declares that she has no conflict of interest.

Ethical approval

All animal work was conducted according to the NIH guidelines and was approved by the Institutional Ethical Committee, Facultad de Medicina, Universidad de Buenos Aires (CD Res. Nº120/2011). The generation of human DCs has been approved by the Ethical Committee of the Academia Nacional de Medicina (Buenos Aires, Argentina, CEIANM 76/2015). All blood donors provided written informed consent for the collection of samples and subsequent analysis.

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Moreno Ayala, M.A., Gottardo, M.F., Gori, M.S. et al. Dual activation of Toll-like receptors 7 and 9 impairs the efficacy of antitumor vaccines in murine models of metastatic breast cancer. J Cancer Res Clin Oncol 143, 1713–1732 (2017). https://doi.org/10.1007/s00432-017-2421-7

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  • Dendritic cell vaccines
  • Toll-like receptors
  • CPG
  • R848
  • Breast cancer