title: Spirulina lipopolysaccharides inhibit tumor growth in a Toll-like receptor 4-dependent manner by altering the cytokine milieu from interleukin-17/interleukin-23 to interferon-γ.
abstract: Th17 cells and the cytokine they produce, interleukin (IL)-17, play an important role in tumor progression in humans and in mice. IL-6 and IL-23 are critical cytokines for the differentiation and propagation of Th17 cells, respectively. Bacterial lipopolysaccharides (LPS) are known to stimulate immune cells to produce such inflammatory cytokines. Contrary to Escherichia coli (E. coli) LPS, LPS from Spirulina has low toxicity and barely induces in vivo production of IL-6 and IL-23 in mice. We examined the antitumor effects of Spirulina LPS compared to E. coli LPS in an MH134 hepatoma model. Administration of Spirulina LPS suppressed tumor growth in C3H/HeN mice, but not in Toll-like receptor 4 (TLR4)-mutant C3H/HeJ mice, by reducing serum levels of IL-17 and IL-23, while increasing interferon (IFN)-γ levels. The antitumor activity and IFN-γ production were mediated by T cells. Moreover, in vitro experiments showed that Spirulina LPS impaired the antigen-presenting function that supports the generation of IL-17-producing cells in a toll-like receptor (TLR)4-dependent manner. Of note, injection of anti-IL-17 antibody in tumor-bearing C3H/HeN mice in the absence of Spirulina LPS markedly suppressed tumor growth and augmented IFN-γ responses. Thus, our results support the notion that IFN-γ and IL-17/IL-23 mutually regulate Th17 and Th1 responses in tumor-bearing hosts, and Spirulina LPS modulates the balance of the IFN-γ-IL-17/IL-23 axis towards IFN-γ production, which leads to tumor inhibition. Furthermore, Spirulina LPS effectively inhibited the spontaneous development of mammary tumors. This study has important implications for the exploitation of TLR-based immunomodulators for cancer immunotherapy.
authors.affiliation: Laboratory of Immunology, Faculty of Pharmacy, Osaka Ohtani University, Tondabayashi, Osaka 584-8540, Japan.
authors.forename: Hiromi
authors.initials: H
authors.lastname: Okuyama
authors.affiliation: Laboratory of Human Health and Medical Science, Graduate School of Kuroshio Science, and Department of Molecular Biology and Cellular Biology, Kochi Medical School, Kochi University, Nankoku, Kochi 783-8505, Japan.
authors.forename: Akira
authors.initials: A
authors.lastname: Tominaga
authors.affiliation: Health Technology Research Center, National Institute of Advanced Industrial Science and Technology (AIST), Takamatsu, Kagawa 761-0395, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Fukuoka
authors.affiliation: Laboratory of Human Health and Medical Science, Graduate School of Kuroshio Science, and Department of Molecular Biology and Cellular Biology, Kochi Medical School, Kochi University, Nankoku, Kochi 783-8505, Japan.
authors.forename: Takahiro
authors.initials: T
authors.lastname: Taguchi
authors.affiliation: Laboratory of Immunology, Faculty of Pharmacy, Osaka Ohtani University, Tondabayashi, Osaka 584-8540, Japan.
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Kusumoto
authors.affiliation: Laboratory of Immunology, Faculty of Pharmacy, Osaka Ohtani University, Tondabayashi, Osaka 584-8540, Japan.
authors.forename: Shiro
authors.initials: S
authors.lastname: Ono
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D006528:Carcinoma, Hepatocellular / Q000276:immunology / Q000378:metabolism / Q000517:prevention & control*; D049109:Cell Proliferation / Q000187:drug effects; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D007371:Interferon-gamma / Q000276:immunology* / Q000378:metabolism; D020381:Interleukin-17 / Q000276:immunology* / Q000378:metabolism; D053759:Interleukin-23 / Q000276:immunology* / Q000378:metabolism; D008070:Lipopolysaccharides / Q000494:pharmacology*; D008113:Liver Neoplasms / Q000276:immunology / Q000378:metabolism / Q000517:prevention & control; D008213:Lymphocyte Activation / Q000187:drug effects; D016399:Lymphoma, T-Cell / Q000276:immunology / Q000378:metabolism / Q000517:prevention & control; D051379:Mice; D008809:Mice, Inbred C3H; D053545:Spirulina / Q000737:chemistry*; D051197:Toll-Like Receptor 4 / Q000276:immunology / Q000378:metabolism*; D014407:Tumor Cells, Cultured; D023041:Xenograft Model Antitumor Assays
chemical_list: D020381:Interleukin-17; D053759:Interleukin-23; D008070:Lipopolysaccharides; D051197:Toll-Like Receptor 4; D007371:Interferon-gamma