title: Toll-like receptor 9 agonist enhances anti-tumor immunity and inhibits tumor-associated immunosuppressive cells numbers in a mouse cervical cancer model following recombinant lipoprotein therapy.
abstract: BACKGROUND
  Although cytotoxic T lymphocytes (CTLs) play a major role in eradicating cancer cells during immunotherapy, the cancer-associated immunosuppressive microenvironment often limits the success of such therapies. Therefore, the simultaneous induction of cancer-specific CTLs and reversal of the immunosuppressive tumor microenvironment may be more effectively achieved through a single therapeutic vaccine. A recombinant lipoprotein with intrinsic Toll-like receptor 2 (TLR2) agonist activity containing a mutant form of E7 (E7m) and a bacterial lipid moiety (rlipo-E7m) has been demonstrated to induce robust CTL responses against small tumors. This treatment in combination with other TLR agonists is able to eliminate large tumors.
  
  
  METHODS
  Mouse bone marrow-derived dendritic cells (DCs) were employed to determine the synergistic production of pro-inflammatory cytokines upon combination of rlipo-E7m and other TLR agonists. Antigen-specific CTL responses were investigated using immunospots or in vivo cytolytic assays after immunization in mice. Mice bearing various tumor sizes were used to evaluate the anti-tumor effects of the formulation. Specific subpopulations of immunosuppressive cells in the tumor infiltrate were quantitatively determined by flow cytometry.
  
  
  RESULTS
  We demonstrate that a TLR9 agonist (unmethylated CpG oligodeoxynucleotide, CpG ODN) enhances CTL responses and eradicates large tumors when combined with rlipo-E7m. Moreover, combined treatment with rlipo-E7m and CpG ODN effectively increases tumor infiltration by CTLs and reduces the numbers of myeloid-derived suppressor cells (MDSCs), tumor-associated macrophages (TAMs) and regulatory T cells (Tregs) in the tumor microenvironment.
  
  
  CONCLUSIONS
  These findings suggest that the dramatic anti-tumor effects of the recombinant lipoprotein together with CpG ODN may reflect the amplification of CTL responses and the repression of the immunosuppressive environment. This promising approach could be applied for the development of additional therapeutic cancer vaccines.
authors.forename: Li-Sheng
authors.initials: LS
authors.lastname: Chang
authors.forename: Chih-Hsiang
authors.initials: CH
authors.lastname: Leng
authors.forename: Yi-Chen
authors.initials: YC
authors.lastname: Yeh
authors.forename: Chiao-Chieh
authors.initials: CC
authors.lastname: Wu
authors.forename: Hsin-Wei
authors.initials: HW
authors.lastname: Chen
authors.affiliation: Institute of Biotechnology and Department of Life Science, National Tsing Hua University, Hsinchu, Taiwan. hmhuang@life.nthu.edu.tw.
authors.forename: Hai-Mei
authors.initials: HM
authors.lastname: Huang
authors.forename: Shih-Jen
authors.initials: SJ
authors.lastname: Liu
mesh_terms: D000818:Animals; D019496:Cancer Vaccines / Q000494:pharmacology*; D004195:Disease Models, Animal; D005260:Female; D005434:Flow Cytometry; D008074:Lipoproteins / Q000494:pharmacology*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009838:Oligodeoxyribonucleotides / Q000494:pharmacology*; D011994:Recombinant Proteins / Q000494:pharmacology; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology; D051217:Toll-Like Receptor 9 / Q000819:agonists; D059016:Tumor Microenvironment / Q000187:drug effects / Q000276:immunology*; D002583:Uterine Cervical Neoplasms / Q000276:immunology* / Q000378:metabolism
chemical_list: C408982:CPG-oligonucleotide; D019496:Cancer Vaccines; D008074:Lipoproteins; D009838:Oligodeoxyribonucleotides; D011994:Recombinant Proteins; C495370:Tlr9 protein, mouse; D051217:Toll-Like Receptor 9