Anti-Tumor Activities And Autoimmune Injury By Toll-Like Receptors (TLR3 And TLR11)

Toil-like receptors(TLRs),one of the pattern recognition receptors(PRRs), recognize a diverse range of pathogen associated molecular patterns.TLR signaling not only play a critical role in driving host immune system to defense infection and tumor,but also participate in the initiation and progression of autoimmune diseases. Although TLR agonists have been widely used as adjuvant therapy in clinical trials for different types of cancer,the mechanism which underlies involvement of TLR signal in overcoming immune tolerance to tumors is still obscure.On the other hand, as the largest organ for toxic elimination,the liver is continuously exposed to gut-derived pathogen products.TLRs and pathogen products are involved in the break of self-tolerance,acute inflammation,and the inflammatory liver injury.And the underlying mechanisms also need more investigation.The present study aims to further investigate the role of TLR signaling in breaking tumor immunological tolerance and liver self-tolerance.The major results are shown as follow:1.IFN-producing killer dendritic cells contribute to the inhibitory effect of poly I:C on the progression of murine melanomaTLR3 agonist polyinosinic-polycytidilic acid(poly I:C)has been widely used as a potent adjuvant in tumor immunotherapy.In the study,it was demonstrated that intraperitoneal injection of poly I:C could inhibit lung and liver metastasis of B16 melanoma cells in C57BL/6 mice in NK cells and IFN-γdependent manner,leading to prolonged survival of the mice.B220~+ CD11c~+ NK1.1~+ cells,recently defined as IFN-producing killer dendritic cells(IKDCs)were markedly increased in the spleen, lung and liver of poly I:C-treated tumor bearing mice,compared with the control group.IFN-γinduction by poly I:C in this unique NK cell subset indicated its critical contribution in tumor suppression in this model.Meanwhile,results of in vitro culture assay showed that poly I:C synergized with B16 cells could significantly promote IKDCs expansion in lymphocytes from different organs,as well as IFN-γproduction. Moreover,these ex vivo expanded IKDCs also exerted cytolytic activities against B16 cells and YAC-1 cells as conventional NK cells did.In conclusion,the findings of this study provide new insights into the role of IFN-γand IKDCs in the anti-tumor effect of poly I:C,and will possibly be helpful to the further study of this unique NK cell subset.2.Poly I:C enhances cycloheximide-induced apoptosis of tumor cells through TLR3 pathwayToll-like receptor 3(TLR3)is a critical component of the innate immune response to dsRNA viruses,which was considered to be mainly expressed in immune cells and some endothelial cells.In this study,we investigated the expression and proapoptotic activity of TLR3 in human and murine tumor cell lines.It's shown that TLR3 are widely expressed on human and murine tumor cell lines,and activation of TLR3 signaling in cancerous cells by poly I:C made Hela cells(human cervical cancer)and MCA38 cells(murine colon cancer)become dose-dependently sensitive to protein synthesis inhibitor cycloheximide(CHX)-induced apoptosis.Blockade of TLR3 recognition with anti-TLR3 antibody greatly attenuated the proapoptotic effects of poly I:C on tumor cells cultured with CHX.IFN-βproduction was induced after poly I:C/CHX treatment and neutralization of IFN-βslightly reduced poly I:C/CHX -induced apoptosis.Our study demonstrated the proapoptotic activity of TLR3 expressed by various tumor cells,which may open a new range of clinical applications for TLR3 agonists as an adjuvant of certain cancer chemotherapy.3.TLR11 ligand profilin induces cytokine-mediated acute liver injury in D-Galactosamine-sensitized miceAs one of the major organs serving synthetic function,liver can be invaded by many kinds of parasites.In this study,we aim to investigate the role of TLR11 pathway in triggering the anti-parasite inflammation response and the inflammatory liver injury. We found that profilin could notably induced lymphocytic infiltration and liver injury in D-GaIN -sensitized mice.The level of proinflammatory cytokine TNF-α,IFN-γ, IL-12 in the serum were significantly increased following administration of profilin and D-GaIN.Neutralization of these cytokine completely abolished profiling/GalN induced liver injury.The result of TLR11 expression analysis showed that it is mainly expressed by Kupffer cells and DCs.We also found that profilin/GalN treatment could induce DC maturation and NK cell activation in vivo.What's more,depletion of Kuppfer cells or NK cells also could protect mice from profilin/GalN induced liver injury,which suggested that these innate immune cells were the major sources of those proinflammatory cytokines.The study is the first to show the mechanism underlying the immune response induced by TLR11 signaling in liver injury,which may be helpful to the further study of liver diseases caused by parasite infection.Taken together,our study suggests that(1)In the microenvironment of the tumor, poly I:C could trigger TLR3 signaling both in immune cells and tumor cells.The mechanism of poly I:C induced tumor regression might be consisted of the induction of immune cells including IKDCs and the sensitization of tumor cells to the pressure. (2)TLR11 pathway is involved in the liver injury caused by anti-parasite immune response,including innate immune cells(DCs,kupffer,NK)activation and proinflammatory factor(TNF-α,IFN-γ,IL-12)release.The study supplemented valuable information for the further study on the cellular and molecular mechanism of tumor immunity and autoimmune liver injury,which is helpful to the clinic treatment and medicine exploration.