Role of toll-like receptors in tissue repair and tumorigenesis

Evaluating targeted therapies in older patients with TP53-mutated AML

Mutation of thetumor suppressor gene, TP53 (tumor protein 53), occurs in up to 15% of all patients with acute myeloid leukemia (AML) and is enriched within specific clinical subsets, most notably in older adults, and including secondary AML cases arising from preceding myeloproliferative neoplasm (MPN), myelodysplastic syndrome (MDS), patients exposed to prior DNA-damaging, cytotoxic therapies. In all cases, these tumors have remained difficult to effectively treat with conventional therapeutic regimens. Newer approaches fortreatmentofTP53-mutated AML have shifted to interventions that maymodulateTP53 function, target downstream molecular vulnerabilities, target non-p53 dependent molecular pathways, and/or elicit immunogenic responses. This review will describe the basic biology of TP53, the clinical and biological patterns of TP53 within myeloid neoplasms with a focus on elderly AML patients and will summarize newer therapeutic strategies and current clinical trials.

Differential Production of Midkine and Pleiotrophin by Innate APCs upon Stimulation through Nucleic Acid-Sensing TLRs

Midkine (MK) and pleiotrophin (PTN) belong to the same family of cytokines. They have similar sequences and functions. Both have important roles in cellular proliferation, tumors, and diseases. They regulate and are expressed by some immune cells. We have recently demonstrated MK production by some human innate antigen-presenting cells (iAPCs), i.e., monocyte-derived dendritic cells (MDDCs) and macrophages stimulated through Toll-like receptor (TLR)-4, and plasmacytoid dendritic cells (pDCs) stimulated through TLR 7. While PTN production was only documented in tissue macrophages. TLRs 3, 7, 8, and 9 are nucleic acid sensing (NAS) TLRs that detect nucleic acids from cell damage and infection and induce iAPC responses. We investigated whether NAS TLRs can induce MK and PTN production by human iAPCs, namely monocytes, macrophages, MDDCs, myeloid dendritic cells (mDCs), and pDCs. Our results demonstrated for the first time that PTN is produced by all iAPCs upon TLR triggering (p < 0.01). IAPCs produced more PTN than MK (p < 0.01). NAS TLRs and iAPCs had differential abilities to induce the production of MK, which was induced in monocytes and pDCs by all NAS TLRs (p < 0.05) and in MDDCs by TLRs 7/8 (p < 0.05). TLR4 induced a stronger MK production than NAS TLRs (p ≤ 0.05). Monocytes produced higher levels of PTN after differentiation to macrophages and MDDCs (p < 0.05). The production of MK and PTN differs among iAPCs, with a higher production of PTN and a selective induction of MK production by NAS TLR. This highlights the potentially important role of iAPCs in angiogenesis, tumors, infections, and autoimmunity through the differential production of MK and PTN upon TLR triggering.

p53, cancer and the immune response

The importance of cancer-cell-autonomous functions of the tumour suppressor p53 (encoded by TP53) has been established in many studies, but it is now clear that the p53 status of the cancer cell also has a profound impact on the immune response. Loss or mutation of p53 in cancers can affect the recruitment and activity of myeloid and T cells, allowing immune evasion and promoting cancer progression. p53 can also function in immune cells, resulting in various outcomes that can impede or support tumour development. Understanding the role of p53 in tumour and immune cells will help in the development of therapeutic approaches that can harness the differential p53 status of cancers compared with most normal tissue.

TLRs in pulmonary diseases

Toll-like receptors (TLRs) comprise a clan of proteins involved in identification and triggering a suitable response against pathogenic attacks. As lung is steadily exposed to multiple infectious agents, antigens and host-derived danger signals, the inhabiting stromal and myeloid cells of the lung express an aggregate of TLRs which perceive the endogenously derived damage-associated molecular patterns (DAMPs) along with pathogen associated molecular patterns (PAMPs) and trigger the TLR-associated signalling events involved in host defence. Thus, they form an imperative component of host defence activation in case of microbial infections as well as non-infectious pulmonary disorders such as interstitial lung disease, acute lung injury and airways disease, such as COPD and asthma. They also play an equally important role in lung cancer. Targeting the TLR signalling network would pave ways to the design of more reliable and effective vaccines against infectious agents and control deadly infections, desensitize allergens and reduce inflammation. Moreover, TLR agonists may act as adjuvants by increasing the efficiency of cancer vaccines, thereby contributing their role in treatment of lung cancer too. Overall, TLRs present a compelling and expeditiously bolstered area of research and addressing their signalling events would be of significant use in pulmonary diseases.

Dynamic Structural Differences between Human and Mouse STING Lead to Differing Sensitivity to DMXAA

The stimulator-of-interferon-genes (STING) protein is involved in innate immunity. It has recently been shown that modulation of STING can lead to an aggressive antitumor response. DMXAA is an antitumor agent that had shown great promise in murine models but failed in human clinical trials. The molecular target of DMXAA was subsequently shown to be murine STING (mSTING); however, human STING (hSTING) is insensitive to DMXAA. Molecular dynamics simulations were employed to investigate the differences between hSTING and mSTING that could influence DMXAA binding. An initial set of simulations was performed to investigate a single lid region mutation G230I in hSTING (corresponding residue in mSTING is an Ile), which rendered the protein sensitive to DMXAA. The simulations found that an Ile side chain was enough to form a steric barrier that prevents exit of DMXAA, whereas in WT hSTING, the Gly residue that lacks a side chain formed a porous lid region that allowed DMXAA to exit. A second set of molecular dynamics simulations compared the tendency of STING to be in an open-inactive conformation or a closed-active conformation. The results show that hSTING prefers to be in an open-inactive conformation even with cGAMP, the native ligand, bound. On the other hand, mSTING prefers a closed-active conformation even without a ligand bound. These results highlight the challenges in translating a mouse active STING compound into a human active compound, while also providing avenues to pursue for designing a small-molecule drug targeting human STING.

Breast Cancer Tumor Stroma: Cellular Components, Phenotypic Heterogeneity, Intercellular Communication, Prognostic Implications and Therapeutic Opportunities

Although the mechanisms underlying the genesis and progression of breast cancer are better understood than ever, it is still the most frequent malignant tumor in women and one of the leading causes of cancer death. Therefore, we need to establish new approaches that lead us to better understand the prognosis of this heterogeneous systemic disease and to propose new therapeutic strategies. Cancer is not only a malignant transformation of the epithelial cells merely based on their autonomous or acquired proliferative capacity. Today, data support the concept of cancer as an ecosystem based on a cellular sociology, with diverse components and complex interactions between them. Among the different cell types that make up the stroma, which have a relevant role in the dynamics of tumor/stromal cell interactions, the main ones are cancer associated fibroblasts, endothelial cells, immune cells and mesenchymal stromal cells. Several factors expressed by the stroma of breast carcinomas are associated with the development of metastasis, such as matrix metalloproteases, their tissular inhibitors or some of their regulators like integrins, cytokines or toll-like receptors. Based on the expression of these factors, two types of breast cancer stroma can be proposed with significantly different influence on the prognosis of patients. In addition, there is evidence about the existence of bi-directional signals between cancer cells and tumor stroma cells with prognostic implications, suggesting new therapeutic strategies in breast cancer.

Microbiota dysbiosis and barrier dysfunction in inflammatory bowel disease and colorectal cancers: exploring a common ground hypothesis

Inflammatory bowel disease (IBD) is a multifactorial disease which arises as a result of the interaction of genetic, environmental, barrier and microbial factors leading to chronic inflammation in the intestine. Patients with IBD had a higher risk of developing colorectal carcinoma (CRC), of which the subset was classified as colitis-associated cancers. Genetic polymorphism of innate immune receptors had long been considered a major risk factor for IBD, and the mutations were also recently observed in CRC. Altered microbial composition (termed microbiota dybiosis) and dysfunctional gut barrier manifested by epithelial hyperpermeability and high amount of mucosa-associated bacteria were observed in IBD and CRC patients. The findings suggested that aberrant immune responses to penetrating commensal microbes may play key roles in fueling disease progression. Accumulative evidence demonstrated that mucosa-associated bacteria harbored colitogenic and protumoral properties in experimental models, supporting an active role of bacteria as pathobionts (commensal-derived opportunistic pathogens). Nevertheless, the host factors involved in bacterial dysbiosis and conversion mechanisms from lumen-dwelling commensals to mucosal pathobionts remain unclear. Based on the observation of gut leakiness in patients and the evidence of epithelial hyperpermeability prior to the onset of mucosal histopathology in colitic animals, it was postulated that the epithelial barrier dysfunction associated with mucosal enrichment of specific bacterial strains may predispose the shift to disease-associated microbiota. The speculation of leaky gut as an initiating factor for microbiota dysbiosis that eventually led to pathological consequences was proposed as the "common ground hypothesis", which will be highlighted in this review. Overall, the understanding of the core interplay between gut microbiota and epithelial barriers at early subclinical phases will shed light to novel therapeutic strategies to manage chronic inflammatory disorders and colitis-associated cancers.

Toll-Like Receptor Agonists Modulate Wound Regeneration in Airway Epithelial Cells

Background: Impaired regeneration of airway epithelium may lead to persistence of inflammation and remodelling. Regeneration of injured epithelium is a complex phenomenon and the role of toll-like receptors (TLRs) in the stimulation of respiratory virus products in this process has not been established. Objective: This study was undertaken to test the hypothesis that the wound repair process in airway epithelium is modulated by microbial products via toll-like receptors. Methods: Injured and not-injured bronchial epithelial cells (ECs) (BEAS-2B line) were incubated with the TLR agonists poly(I:C), lipopolisacharide (LPS), allergen Der p1, and supernatants from virus-infected epithelial cells, either alone or in combination with TLR inhibitors. Regeneration and immune response in injured and not-injured cells were studied. Results: Addition of either poly(I:C) or LPS to ECs induced a marked inhibition of wound repair. Supernatants from RV1b-infected cells also decreased regeneration. Preincubation of injured and not-injured ECs with TLR inhibitors decreased LPS and poly(I:C)-induced repair inhibition. TGF-β and RANTES mRNA expression was higher in injured ECs and IFN-α, IFN-β, IL-8, and VEGF mRNA expression was lower in damaged epithelium as compared to not-injured. Stimulation with poly(I:C) increased IFN-α and IFN-β mRNA expression in injured cells, and LPS stimulation decreased interferons mRNA expression both in not-injured and injured ECs. Conclusion: Regeneration of the airway epithelium is modulated by microbial products via toll-like receptors.

BVDV Npro protein mediates the BVDV induced immunosuppression through interaction with cellular S100A9 protein

The innate immune response is a vital part of the body's antiviral defense system. The innate immune response is initiated by various receptor interactions, including danger associated molecular patterns (DAMPs). The S100A9 is a member of the DAMPs protein family and, is released by activated phagocytic cells such as neutrophils, monocytes, macrophages or endothelial cells, and S100A9 induces its effect through TLR4/MyD88 pathway.

Bovine viral diarrhea virus (BVDV) is one of the major devastating disease in the cattle industry worldwide. It shows its effect through immunosuppression and develops persistent infection in calves born from infected cows. The current study revealed that BVDV potentially induced immunosuppression by the interaction of BVDV Npro protein with cellular S100A9 protein. The Inhibition of S100A9 protein expression by small interfering RNA (siRNA) enhanced the virus replication in infected cells. Overexpression of bovine S100A9 enhanced the ncpBVDV2a 1373 mediated Type-I interferon production. A co-immunoprecipitation experiment demonstrated a strong interaction between ncp BVDV2a 1373 Npro protein and cellular S100A9 protein. This suggested that BVDV Npro reduced the S100A9 protein availability/activity in infected cells, resulting in reduced Type-I interferon production. A further study of S100A9-BVDV interaction will be need for better understanding of BVDV pathophysiology.

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The bovine viral diarrhea virus (BVDV) nonstructural protein, Npro, is responsible for immunosuppression.

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The mechanism of Npro immune immunosuppression is not well characterized.

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S100A9, a cell protein that contains danger associated molecular patterns (DAMP), is important in innate immunity.

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S100A9 protein and Npro protein associate while overexpression of S100A9 enhanced Type-I interferon production.

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Inhibition of S100A9 by siRNA aided BVDV replication. Npro interacting with S100A9 may result in immunosuppression.

Chronic kidney disease induces inflammation by increasing Toll-like receptor-4, cytokine and cathelicidin expression in neutrophils and monocytes

TLR expression in neutrophils and monocytes is associated with increased cytokine synthesis, resulting in increased inflammation. However, the inflammatory pathway related to TLR and cathelicidin expression in these cells from CKD patients is unclear. To evaluate TLR4, cathelicidin, TNF-α, IL-6, IL-10 and MCP-1 expression in neutrophils and monocytes from HD and CKD patients. Blood samples were drawn from 47 CKD and 43 HD patients and 71 age and gender-matched healthy volunteers (CONT). TLR4 was analyzed using flow cytometry. Cathelicidin, TNF-α, IL-6, IL-10 and MCP-1 were analyzed via ELISA.TLR4 expression in neutrophils was higher in HD patients than in stage 3 and 4 CKD patients. In these cells, we observed a positive correlation between TLR4 and cathelicidin, TNF-α, IL-6, IL-10 and MCP-1 levels. In monocytes, TLR4 expression was significantly higher in CKD 3 and 4 groups than in the control and HD groups and positively and negatively correlated with IL-6 and MCP-1 and cathelicidin, respectively. TNF-α, IL-6 and MCP-1 serum levels were higher in HD and CKD patients than in control. Cathelicidin and IL-10 levels were only higher in HD patients. IL-6 serum levels were positively correlated with all cytokines, and cathelicidin was negatively correlated with MCP-1 (r = - 0.35; p < 0.01) and positively correlated with IL-10 (r = 0.37; p = 0.001). These results suggest that a uremic environment induces high TLR4, cathelicidin and cytokine expression and may increase inflammation. Thus, future studies should be conducted to evaluate whether TLR4 and cathelicidin should be targets for anti-inflammatory therapeutic strategies.

Lack of Associations between TLR9 and MYD88 Gene Polymorphisms and Risk of Chronic Lymphocytic Leukemia

Background:

Genetic factors like single nucleotide polymorphisms (SNPs) may play an important role in the etiology of chronic lymphocytic leukemia (CLL). Mutations in Toll like receptor 9 (TLR9) and myeloid differentiation primary response 88 (MYD88) genes may lead to an abnormal immune response that may cause greater cell proliferation and thus alter an individual’s susceptibility to haematological malignancies including CLL.

Objective:

This work was designed to study any association of the TLR9 (rs2066807C/G and rs187084T/C) and MYD88 (L265P) single nucleotide polymorphism (SNPs) with risk of CLL in Egyptians.

Materials and methods:

One hundred patients with CLL and 100 healthy controls from the Egyptian population were genotyped by the polymerase chain reaction/restriction fragment length polymorphism (PCR/RFLP) method.

Results:

With TLR9 rs2066807C/G the CC genotype was more frequent in both control and patient groups while for TLR9 rs187084T/C the TT genotype was most common. There were no significant associations with CLL risk. With MYD88 (L265P) only the TT genotype was detected.

Conclusion:

Our preliminary data suggest that polymorphisms in the TLR9 and MYD88 genes may not contribute to CLL susceptibility. To the best of our knowledge, this study is the first dealing with TLR9 and MYD88 gene polymorphisms in CLL patients. Further studies with larger sample size should be conducted to validate these results in the Egyptian population.

Identification, molecular evolution of toll-like receptors in a Tibetan schizothoracine fish (Gymnocypris eckloni) and their expression profiles in response to acute hypoxia

Hypoxia plays an important role in regulating a variety of physiological responses as well as in pathological situations, but to date the roles of Toll-like receptors (TLRs) in fish in response to hypoxia are still poorly understood. Here, we sequenced the transcriptome of G. eckloni and identified the members of TLR family by scanning transcriptome, and then investigated the expression profiles of a complete set of TLRs in G. eckloni in response to acute hypoxia (4 h at DO = 0.3 ± 0.1 mg/L). The de novo-assembled transcriptome consisted of a total of 162,235 transcripts, further clustered into 110,231 unigenes. Based on the transcriptome, a total of 18 TLRs were identified in G. eckloni, and of them three TLRs (TLR5, TLR8 and TLR22) possessed two distinct paralogous genes. The duplicated genes of TLR22 were discovered for the first time in cyprinid fish, but did not origin from a recent duplication event. Of them TLR22b may be specific for schizothoracine fish, at least for G. eckloni. Phylogenetic analysis supported the classification of TLRs into six families as in other vertebrates but was partly different from the previous study. The sliding window analysis showed strong signals of positive selection in TLR2, TLR 4, TLR 5a, TLR 7, TLR 19, TLR 20, TLR 21, TLR 22a and TLR 22b, but most codons under positive selection were located in the putative LRR regions. The mRNA expression of most TLRs in head kidney, spleen and gill decreased significantly or remained unchanged under acute hypoxia, whereas acute hypoxia increased expressions of TLR2 and TLR3 in head kidney, of TLR8a, TLR12 and TLR19 in spleen, and of TLR1 in gill, suggesting tissues-specific expressions of TLRs play important roles in mediating innate immune responses for host defense against tissue damages or physiological changes induced by hypoxia.

Toll-like receptor expression patterns in the rat uterus during post partum involution

Toll-like receptors (TLRs) belong to a family of pathogen recognition receptors and play critical roles in detecting and responding to invading pathogens. TLR expression could be significant because, in the uterus, the reproductive tract is an important site of exposure to and infection by pathogens during the post partum involution period. To clarify the expression and localisation patterns of TLRs in the rat uterus on Days 1, 3, 5 and 10 post partum (PP1, PP3, PP5 and PP10 respectively), immunohistochemistry and western blotting were used to analyse TLR1-7, TLR9 and TLR10. The immunohistochemistry results indicated that TLR1-7, TLR9 and TLR10 were localised in both the cytoplasm and nuclei of luminal and glandular epithelium, stromal fibroblasts and myometrial cells in the rat uterus. In the luminal epithelium, TLR4-7 were also found in lateral membranes, whereas TLR10 was present in apical membranes. Western blot analysis revealed that the expression of TLR proteins increased with the number of days post partum, reaching a maximum on PP10, although levels did not differ significantly from those on PP1 (P>0.05). These findings confirm that TLR1-7, TLR9 and TLR10 are constitutively expressed in uterine cells and that localisation pattern of TLRs in the endometrium varies with structural changes in the uterus on different days of involution. These results suggest that TLRs may play a role in uterine repair and remodelling during physiological involution.

Toll-Like Receptor 4 Inhibition Improves Oxidative Stress and Mitochondrial Health in Isoproterenol-Induced Cardiac Hypertrophy in Rats

BACKGROUND

Inflammation remains a crucial factor for progression of cardiac diseases and cardiac hypertrophy remains an important cause of cardiac failure over all age groups. As a key regulator of inflammation, toll-like receptor 4 (TLR4) plays an important role in pathogenesis of cardiac diseases. Being an important regulator of innate immunity, the precise pathway of TLR4-mediated cardiac complications is yet to be established. Therefore, the primary objective of the present study was to find the role of TLR4 in cardiac hypertrophy and the molecular mechanism thereof.

METHODS

Cardiac hypertrophy was induced with administration of isoproterenol (5 mg/kg/day, sc). TLR4 receptor inhibitor RS-LPS (lipopolysaccharide from the photosynthetic bacterium Rhodobacter sphaeroides; 5 μg/day) and agonist lipopolysaccharide (LPS) (from Escherichia coli; 3.12 μg/day) were administered through osmotic pump along with isoproterenol. Cardiac hypertrophy as well as oxidative stress and mitochondrial parameters were evaluated.

RESULTS

Cardiac hypertrophy was confirmed with increased heart weight/body weight ratio as well as assessment of hypertrophic markers in heart. There was a marked increase in the TLR4 expression and oxidative stress along with mitochondrial dysfunction in ISO group. TLR4 inhibition significantly decreased heart weight/body weight ratio and ANP, collagen, and β-MHC expression and restored the disturbed cellular antioxidant flux. The mitochondrial perturbations that were observed in hypertrophy heart was normalized after administration of TLR4 inhibitor but not with the agonist. TLR4 agonism further exaggerated the oxidative stress in heart and hence accelerated the disease development and progression.

CONCLUSION

Our data show that increased TLR4 ligand pool in cardiac hypertrophy may exaggerate the disease progression. However, inhibition of TLR4 attenuated cardiac hypertrophy through reduced cardiac redox imbalance and mitochondrial dysfunction.

Types of Immune-Inflammatory Responses as a Reflection of Cell-Cell Interactions under Conditions of Tissue Regeneration and Tumor Growth

Inflammatory infiltration of tumor stroma is an integral reflection of reactions that develop in response to any damage to tumor cells including immune responses to antigens or necrosis caused by vascular disorders. In this review, we use the term "immune-inflammatory response" (IIR) that allows us to give an integral assessment of the cellular composition of the tumor microenvironment. Two main types of IIRs are discussed: type 1 and 2 T-helper reactions (Th1 and Th2), as well as their inducers: immunosuppressive responses and reactions mediated by Th22 and Th17 lymphocytes and capable of modifying the main types of IIRs. Cellular and molecular manifestations of each IIR type are analyzed and their general characteristics and roles in tissue regeneration and tumor growth are presented. Since inflammatory responses in a tumor can also be initiated by innate immunity mechanisms, special attention is given to inflammation based on them. We emphasize that processes accompanying tissue regeneration are prototypes of processes underlying cancer progression, and these processes have the same cellular and molecular substrates. We focus on evidence that tumor progression is mainly contributed by processes specific for the second phase of "wound healing" that are based on the Th2-type IIR. We emphasize that the effect of various types of immune and stroma cells on tumor progression is determined by the ability of the cells and their cytokines to promote or prevent the development of Th1- or Th2-type of IIR. Finally, we supposed that the nonspecific influence on the tumor caused by the cytokine context of the Th1- or Th2-type microenvironment should play a decisive role for suppression or stimulation of tumor growth and metastasis.

Toll Like Receptor 2, 4, and 9 Signaling Promotes Autoregulative Tumor Cell Growth and VEGF/PDGF Expression in Human Pancreatic Cancer

Toll like receptor (TLR) signaling has been suggested to play an important role in the inflammatory microenvironment of solid tumors and through this inflammation-mediated tumor growth. Here, we studied the role of tumor cells in their process of self-maintaining TLR expression independent of inflammatory cells and cytokine milieu for autoregulative tumor growth signaling in pancreatic cancer. We analyzed the expression of TLR2, -4, and -9 in primary human cancers and their impact on tumor growth via induced activation in several established pancreatic cancers. TLR-stimulated pancreatic cancer cells were specifically investigated for activated signaling pathways of VEGF/PDGF and anti-apoptotic Bcl-xL expression as well as tumor cell growth. The primary pancreatic cancers and cell lines expressed TLR2, -4, and -9. TLR-specific stimulation resulted in activated MAP-kinase signaling, most likely via autoregulative stimulation of demonstrated TLR-induced VEGF and PDGF expression. Moreover, TLR activation prompted the expression of Bcl-xL and has been demonstrated for the first time to induce tumor cell proliferation in pancreatic cancer. These findings strongly suggest that pancreatic cancer cells use specific Toll like receptor signaling to promote tumor cell proliferation and emphasize the particular role of TLR2, -4, and -9 in this autoregulative process of tumor cell activation and proliferation in pancreatic cancer.

Toll-like receptors in pathophysiology of liver diseases

Toll-like receptors (TLRs) are pattern recognition receptors that participate in host defense by recognizing pathogen-associated molecular patterns alongside inflammatory processes by recognizing damage associated molecular patterns. Given constant exposure to pathogens from gut, strict control of TLR-associated signaling pathways is essential in the liver, which otherwise may lead to inappropriate production of pro-inflammatory cytokines and interferons and may generate a predisposition to several autoimmune and chronic inflammatory diseases. The liver is considered to be a site of tolerance induction rather than immunity induction, with specificity in hepatic cell functions and distribution of TLR. Recent data emphasize significant contribution of TLR signaling in chronic liver diseases via complex immune responses mediating hepatocyte (i.e., hepatocellular injury and regeneration) or hepatic stellate cell (i.e., fibrosis and cirrhosis) inflammatory or immune pathologies. Herein, we review the available data on TLR signaling, hepatic expression of TLRs and associated ligands, as well as the contribution of TLRs to the pathophysiology of hepatic diseases.

TLR3 activation induces S100A7 to regulate keratinocyte differentiation after skin injury

Human S100A7 (psoriasin) is highly expressed in psoriasis and other inflammatory diseases; however, the function of S100A7 in wound repair remains largely unknown. Here we demonstrated that skin injury increased the expression of S100A7. Damaged cells from wounded skin induced the expression of S100A7 via the activation of Toll-like receptor 3 (TLR3) followed by the activation of p38 MAPK. S100A7, in turn, acted on keratinocytes to induce the expression of terminal differentiation marker gene loricrin through the activation of p38 MAPK and caspase-1. The differentiation of keratinocytes induced by S100A7 resulted in skin stratification, thus efficiently promoting wound closure. Taken together, our results demonstrate that the activation of TLR3 accelerates wound closure via the induction of S100A7 to induce keratinocyte differentiation. These findings also provide new insights into the development of different forms of treatment with skin wounds.

TLR9 re-expression in cancer cells extends the S-phase and stabilizes p16(INK4a) protein expression

Toll-like receptor 9 (TLR9) recognizes bacterial, viral or cell damage-associated DNA, which initiates innate immune responses. We have previously shown that TLR9 expression is downregulated in several viral induced cancers including HPV16-induced cervical neoplasia. Findings supported that downregulation of TLR9 expression is involved in loss of anti-viral innate immunity allowing an efficient viral replication. Here we investigated the role of TLR9 in altering the growth of transformed epithelial cells. Re-introducing TLR9 under the control of an exogenous promoter in cervical or head and neck cancer patient-derived cells reduced cell proliferation, colony formation and prevented independent growth of cells under soft agar. Neither TLR3, 7, nor the TLR adapter protein MyD88 expression had any effect on cell proliferation, indicating that TLR9 has a unique role in controlling cell growth. The reduction of cell growth was not due to apoptosis or necrosis, yet we observed that cells expressing TLR9 were slower in entering the S-phase of the cell cycle. Microarray-based gene expression profiling analysis highlighted a strong interferon (IFN) signature in TLR9-expressing head and neck cancer cells, with an increase in IFN-type I and IL-29 expression (IFN-type III), yet neither IFN-type I nor IL-29 production was responsible for the block in cell growth. We observed that the protein half-life of p16(INK4a) was increased in TLR9-expressing cells. Taken together, these data show for the first time that TLR9 affects the cell cycle by regulating p16(INK4a) post-translational modifications and highlights the role of TLR9 in the events that lead to carcinogenesis.

The interplay between the microbiome and the adaptive immune response in cancer development

The data from different studies suggest a bacterial role in cancer genesis/progression, often modulating the local immune response. This is particularly so at the mucosal level where the bacterial presence is strong and the immune system is highly reactive. The epithelial surfaces of the body, such as the skin and mucosa, are colonized by a vast number of microorganisms, which represent the so-called normal microbiome. Normally the microbiome does not cause a proinflammatory response because the immune system has developed different strategies for the tolerance of commensal bacteria, but when these mechanisms are impaired or new pathogenic bacteria are introduced into this balanced system, the immune system reacts to the microbiome and can trigger tumor growth in the intestine. In this review, we discuss the potential role of the bacterial microbiome in carcinogenesis, focusing on the direct and indirect immune adaptive mechanisms, that the bacteria can modulate in different ways.

Cross-talk between 4-1BB and TLR1-TLR2 Signaling in CD8+ T Cells Regulates TLR2's Costimulatory Effects

The activation of TLR-MyD88 (Toll-like receptor-myeloid differentiation factor 88) signaling within T cells functions as a potent costimulatory signal that boosts antitumor and antiviral responses. However, the molecular mechanisms underlying the costimulatory processes are poorly understood. We compared microarray gene analysis data between TLR1-TLR2-stimulated and unstimulated T-cell receptor transgenic "pmel" and MyD88(-/-) pmel CD8(+) T cells and identified changes in the expression of several TNF family members. In particular, TLR stimulation increased 4-1BB levels in pmel but not in MyD88(-/-)pmel T cells. A link between 4-1BB and TLR1-TLR2 signaling in CD8(+) T cells was highlighted by the suboptimal responses of 4-1BB(-/-) T cells to TLR1-TLR2 agonist, but their normal response to CD28 or OX40 costimulation. Blocking 4-1BB signaling with antibodies also hindered the costimulatory effects of the TLR1-TLR2 agonist. The elevated levels of 4-1BB transcripts in TLR1-TLR2-stimulated cells were not due to increased mRNA stability nor increased histone activation, but instead were associated with increased binding of p65 and c-Jun to two distinct 4-1BB promoter sites. Combining TLR1-TLR2 ligand with an agonistic antibody to 4-1BB enhanced the antitumor activity in mice with established melanoma tumors. These studies reveal that the costimulatory effects of TLR1-TLR2 signaling in CD8(+) T cells are in part mediated by 4-1BB and are important for mounting an effective antitumor immune response. Cancer Immunol Res; 4(8); 708-16. ©2016 AACR.

Clinically feasible approaches to potentiating cancer cell-based immunotherapies

The immune system exerts both tumor-destructive and tumor-protective functions. Mature dendritic cells (DCs), classically activated macrophages (M1), granulocytes, B lymphocytes, aβ and ɣδ T lymphocytes, natural killer T (NKT) cells, and natural killer (NK) cells may be implicated in antitumor immunoprotection. Conversely, tolerogenic DCs, alternatively activated macrophages (M2), myeloid-derived suppressor cells (MDSCs), and regulatory T (Tregs) and B cells (Bregs) are capable of suppressing antitumor immune responses. Anti-cancer vaccination is a useful strategy to elicit antitumor immune responses, while overcoming immunosuppressive mechanisms. Whole tumor cells or lysates derived thereof hold more promise as cancer vaccines than individual tumor-associated antigens (TAAs), because vaccinal cells can elicit immune responses to multiple TAAs. Cancer cell-based vaccines can be autologous, allogeneic or xenogeneic. Clinical use of xenogeneic vaccines is advantageous in that they can be most effective in breaking the preexisting immune tolerance to TAAs. To potentiate immunotherapy, vaccinations can be combined with other modalities that target different immune pathways. These modalities include 1) genetic or chemical modification of cell-based vaccines; 2) cross-priming TAAs to T cells by engaging dendritic cells; 3) T-cell adoptive therapy; 4) stimulation of cytotoxic inflammation by non-specific immunomodulators, toll-like receptor (TLR) agonists, cytokines, chemokines or hormones; 5) reduction of immunosuppression and/or stimulation of antitumor effector cells using antibodies, small molecules; and 6) various cytoreductive modalities. The authors envisage that combined immunotherapeutic strategies will allow for substantial improvements in clinical outcomes in the near future.

T-cell activation and early gene response in dogs

T-cells play a crucial role in canine immunoregulation and defence against invading pathogens. Proliferation is fundamental to T-cell differentiation, homeostasis and immune response. Initiation of proliferation following receptor mediated stimuli requires a temporally programmed gene response that can be identified as immediate-early, mid- and late phases. The immediate-early response genes in T-cell activation engage the cell cycle machinery and promote subsequent gene activation events. Genes involved in this immediate-early response in dogs are yet to be identified. The present study was undertaken to characterise the early T-cell gene response in dogs to improve understanding of the genetic mechanisms regulating immune function. Gene expression profiles were characterised using canine gene expression microarrays and quantitative reverse transcription PCR (qRT-PCR), and paired samples from eleven dogs. Significant functional annotation clusters were identified following stimulation with phytohemagluttinin (PHA) (5μg/ml), including the Toll-like receptor signaling pathway and phosphorylation pathways. Using strict statistical criteria, 13 individual genes were found to be differentially expressed, nine of which have ontologies that relate to proliferation and cell cycle control. These included, prostaglandin-endoperoxide synthase 2 (PTGS2/COX2), early growth response 1 (EGR1), growth arrest and DNA damage-inducible gene (GADD45B), phorbol-12-myristate-13-acetate-induced protein 1 (PMAIP1), V-FOS FBJ murine osteosarcoma viral oncogene homolog (FOS), early growth response 2 (EGR2), hemogen (HEMGN), polo-like kinase 2 (PLK2) and polo-like kinase 3 (PLK3). Differential gene expression was re-examined using qRT-PCR, which confirmed that EGR1, EGR2, PMAIP1, PTGS2, FOS and GADD45B were significantly upregulated in stimulated cells and ALAS2 downregulated. PTGS2 and EGR1 showed the highest levels of response in these dogs. Both of these genes are involved in cell cycle regulation. This study provides a comprehensive analysis of the early T-cell gene response to activation in dogs.

Interleukin-18 increases TLR4 and mannose receptor expression and modulates cytokine production in human monocytes

Interleukin-18 is a proinflammatory cytokine belonging to the interleukin-1 family of cytokines. This cytokine exerts many unique biological and immunological effects. To explore the role of IL-18 in inflammatory innate immune responses, we investigated its impact on expression of two toll-like receptors (TLR2 and TLR4) and mannose receptor (MR) by human peripheral blood monocytes and its effect on TNF-α, IL-12, IL-15, and IL-10 production. Monocytes from healthy donors were stimulated or not with IL-18 for 18 h, and then the TLR2, TLR4, and MR expression and intracellular TNF-α, IL-12, and IL-10 production were assessed by flow cytometry and the levels of TNF-α, IL-12, IL-15, and IL-10 in culture supernatants were measured by ELISA. IL-18 treatment was able to increase TLR4 and MR expression by monocytes. The production of TNF-α and IL-10 was also increased by cytokine treatment. However, IL-18 was unable to induce neither IL-12 nor IL-15 production by these cells. Taken together, these results show an important role of IL-18 on the early phase of inflammatory response by promoting the expression of some pattern recognition receptors (PRRs) that are important during the microbe recognition phase and by inducing some important cytokines such as TNF-α and IL-10.

Emerging role of Toll-like receptor 4 in hepatocellular carcinoma

Toll-like receptor (TLR) signaling has been implicated in inflammatory-related cancers. The upregulation of TLR signaling in hepatocellular carcinoma (HCC) suggests that it may play an essential role in the prognosis of chronic and inflammatory diseases that ultimately culminate in HCC. Here, we provide evidence about the involvement of the TLR pathway in the initiation, progression, and metastasis of HCC. The differential expression of TLR in epithelial cells has also been discussed. In particular, we emphasize the physiological role of TLR4 in the development and pathogenesis of HCC and propose novel and promising approaches for HCC therapeutics with the aid of TLR ligands.

LPS receptor subunits have antagonistic roles in epithelial apoptosis and colonic carcinogenesis

Colorectal carcinoma (CRC) is characterized by unlimited proliferation and suppression of apoptosis, selective advantages for tumor survival, and chemoresistance. Lipopolysaccharide (LPS) signaling is involved in both epithelial homeostasis and tumorigenesis, but the relative roles had by LPS receptor subunits CD14 and Toll-like receptor 4 (TLR4) are poorly understood. Our study showed that normal human colonocytes were CD14(+)TLR4(-), whereas cancerous tissues were CD14(+)TLR4(+), by immunofluorescent staining. Using a chemical-induced CRC model, increased epithelial apoptosis and decreased tumor multiplicity and sizes were observed in TLR4-mutant mice compared with wild-type (WT) mice with CD14(+)TLR4(+) colonocytes. WT mice intracolonically administered a TLR4 antagonist displayed tumor reduction associated with enhanced apoptosis in cancerous tissues. Mucosa-associated LPS content was elevated in response to CRC induction. Epithelial apoptosis induced by LPS hypersensitivity in TLR4-mutant mice was prevented by intracolonic administration of neutralizing anti-CD14. Moreover, LPS-induced apoptosis was observed in primary colonic organoid cultures derived from TLR4 mutant but not WT murine crypts. Gene silencing of TLR4 increased cell apoptosis in WT organoids, whereas knockdown of CD14 ablated cell death in TLR4-mutant organoids. In vitro studies showed that LPS challenge caused apoptosis in Caco-2 cells (CD14(+)TLR4(-)) in a CD14-, phosphatidylcholine-specific phospholipase C-, sphingomyelinase-, and protein kinase C-ζ-dependent manner. Conversely, expression of functional but not mutant TLR4 (Asp299Gly, Thr399Ile, and Pro714His) rescued cells from LPS/CD14-induced apoptosis. In summary, CD14-mediated lipid signaling induced epithelial apoptosis, whereas TLR4 antagonistically promoted cell survival and cancer development. Our findings indicate that dysfunction in the CD14/TLR4 antagonism may contribute to normal epithelial transition to carcinogenesis, and provide novel strategies for intervention against colorectal cancer.

Naturally occurring hydroxytyrosol derivatives: hydroxytyrosyl acetate and 3,4-dihydroxyphenylglycol modulate inflammatory response in murine peritoneal macrophages. Potential utility as new dietary supplements

This work evaluated the effects of extra virgin olive oil (EVOO) phenols, hydroxytyrosyl acetate (2) and 3,4-dihydroxyphenylglycol (3), as well as two new acyl derivatives of 3, 4-(1,2-di(butanoyloxy)ethyl)benzene-1,2-diol (7) and 4-(1,2-di(lauroyloxy)ethyl)benzene-1,2-diol (8), on LPS-stimulated murine peritoneal macrophages in comparison with hydroxytyrosol (HTy, 1). Compounds 2, 3, 7, and 8 showed a strong reactive oxygen species (ROS)-scavenging activity, reducing significantly nitrite levels with a significant decrease on iNOS expression [2 (50 μM, 0.44 ± 0.03; 100 μM, 0.44 ± 0.01; p < 0.01); 3 (50 μM, 0.37 ± 0.03; 100 μM, 0.37 ± 0.01; p < 0.001); 7 (50 μM, 0.45 ± 0.06; p < 0.01)] . However, only 2 and 3 down-regulated COX-2 expression [2 (50 μM, 0.72 ± 0.04, p < 0.05; 100 μM, 0.54 ± 0.06, p < 0.01); 3 (50 μM, 0.56 ± 0.05, p < 0.05; 100 μM, 0.37 ± 0.04; p < 0.001)] and prevented IKBα degradation [2 (100 μM, 1.63 ± 0.14, p < 0.01); 3 (100 μM, 1.82 ± 0.09; p < 0.01)] ; the diacylated compounds 7 and 8 showed worse anti-inflammatory activity than the parent 3. In conclusion, 2 and 3 phenolic derivatives could play an important role in the anti-inflammatory effect of EVOO. The implication of this study for the nutrition and general health of the population rests in the possible use of natural HTy derivatives with better hydrophilic/lipophilic balance, thus improving its pharmacodynamic and pharmacokinetic profiles, as new dietary supplements in foods.

Intestinal epithelial suppressor of cytokine signaling 3 enhances microbial-induced inflammatory tumor necrosis factor-α, contributing to epithelial barrier dysfunction

A single layer of intestinal epithelial cells (IEC) lines the entire gastrointestinal tract and provides the first line of defense and barrier against an abundance of microbial stimuli. IEC homeostasis and repair are mediated through microbe-sensing Toll-like receptor (TLR)-induced inflammatory pathways. Increasing evidence supports a role of suppressor of cytokine signaling 3 (SOCS3) as a modulator of IEC turnover, balancing controlled repair and replenishment with excessive IEC proliferation predisposing to dysplasia and cancer. Our data indicate that SOCS3 can limit microbial-induced IEC repair, potentially through promoting tumor necrosis factor-α (TNF-α) and limiting TNFR2 expression. Activation of TLR5 signaling pathways, compared with other TLR, increases TNF-α mRNA in a dose-dependent manner and SOCS3 enhances TLR5-induced TNF-α. We also show that flagellin promotes transcription of TNFR2 and that SOCS3 limits this expression, presenting a mechanism of SOCS3 action. Our data also support the role of microbial ligands in epithelial wound healing and suggest that a functional consequence of increased TNF-α is reduced wound healing. These results provide further evidence to support the regulatory role of epithelial SOCS3 in intestinal health and suggest that the increased expression of SOCS3 observed in IBD may serve to perpetuate "inflammation" by promoting TNF-α production and limiting epithelial repair in response to commensal microflora.

Toll-like receptors and cancer, particularly oral squamous cell carcinoma

It is becoming increasingly apparent that the tumor microenvironment plays an important role in the progression of cancer. The microenvironment may promote tumor cell survival and proliferation or, alternatively may induce tumor cell apoptosis. Toll-like receptors (TLRs) are transmembrane proteins, expressed on immune cells and epithelial cells, that recognize exogenous and endogenous macromolecules. Once activated, they initiate signaling pathways leading to the release of cytokines and chemokines, which recruit immune cells inducing further cytokine production, the production of angiogenic mediators and growth factors, all of which may influence tumor progression. This paper examines the actions of TLRs in carcinogenesis with particular emphasis on their role in oral squamous cell carcinoma.

An integrated omics analysis: impact of microgravity on host response to lipopolysaccharide in vitro

BACKGROUND

Microgravity facilitates the opportunistic infections by augmenting the pathogenic virulence and suppressing the host resistance. Hence the extraterrestrial infections may activate potentially novel bionetworks different from the terrestrial equivalent, which could only be probed by investigating the host-pathogen relationship with a minimum of terrestrial bias.

RESULTS

We customized a cell culture module to expose human endothelial cells to lipopolysaccharide (LPS). The assay was carried out onboard the STS-135 spaceflight, and a concurrent ground study constituted the baseline. Transcriptomic investigation revealed a possible immune blunting in microgravity suppressing in particular Lbp, MyD88 and MD-2, which encode proteins responsible for early LPS uptake. Certain cytokines, such as IL-6 and IL-8, surged in response to LPS insult in microgravity, as suggested by the proteomics study. Contrasting proteomic expressions of B2M, TIMP-1 and VEGRs suggested impaired pro-survival adaptation and healing mechanisms. Differential expression of miR-200a and miR-146b suggested the susceptibility of hosts in spaceflight to oxidative stress and further underscored the influence of microgravity on the immunity.

CONCLUSIONS

A molecular interpretation explaining the etiology of the microgravitational impact on the host-pathogen relationship elucidated comprehensive immune blunting of the host cells responding to LPS challenges. Longer LPS exposure prompted a delayed host response, potentially ineffectual in preventing pathogens from opportunistic invasion. Significant consequences include the subsequent failure in recruiting the growth factors and a debilitated apoptosis. Follow up studies with larger sample size are warranted.

Multiple roles of toll-like receptor 4 in colorectal cancer

Toll-like receptor (TLR) signaling has been implicated in the inflammatory responses in intestinal epithelial cells (IECs). Such inflammatory signals mediate complex interactions between commensal bacteria and TLRs and are required for IEC proliferation, immune response, repair, and homeostasis. The upregulation of certain TLRs in colorectal cancer (CRC) tissues suggests that TLRs may play an essential role in the prognosis of chronic and inflammatory diseases that ultimately culminate in CRC. Here, we provide a comprehensive review of the literature on the involvement of the TLR pathway in the initiation, progression, and metastasis of CRC, as well as inherited genetic variation and epigenetic regulation. The differential expression of TLRs in epithelial cells has also been discussed. In particular, we emphasize the physiological role of TLR4 in CRC development and pathogenesis, and propose novel and promising approaches for CRC therapeutics with the aid of TLR ligands.

Pattern recognition receptors and the inflammasome in kidney disease

Toll-like receptors (TLRs) and nucleotide-binding oligomerization domain receptors (NLRs) are families of pattern recognition receptors that, together with inflammasomes, sense and respond to highly conserved pathogen motifs and endogenous molecules released upon cell damage or stress. Evidence suggests that TLRs, NLRs and the NACHT, LRR and PYD domains-containing protein 3 (NLRP3) inflammasome have important roles in kidney diseases through regulation of inflammatory and tissue-repair responses to infection and injury. In this Review, we discuss the pathological mechanisms that are related to TLRs, NLRs and NLRP3 in various kidney diseases. In general, these receptors are protective in the host defence against urinary tract infection, but can sustain and self-perpetuate tissue damage in sterile inflammatory and immune-mediated kidney diseases. TLRs, NLRs and NLRP3, therefore, have become promising drug targets to enable specific modulation of kidney inflammation and suppression of immunopathology in kidney disease.

Mouse, but not human STING, binds and signals in response to the vascular disrupting agent 5,6-dimethylxanthenone-4-acetic acid

Vascular disrupting agents such as 5,6-dimethylxanthenone-4-acetic acid (DMXAA) represent a novel approach for cancer treatment. DMXAA has potent antitumor activity in mice and, despite significant preclinical promise, failed human clinical trials. The antitumor activity of DMXAA has been linked to its ability to induce type I IFNs in macrophages, although the molecular mechanisms involved are poorly understood. In this study, we identify stimulator of IFN gene (STING) as a direct receptor for DMXAA leading to TANK-binding kinase 1 and IFN regulatory factor 3 signaling. Remarkably, the ability to sense DMXAA was restricted to murine STING. Human STING failed to bind to or signal in response to DMXAA. Human STING also failed to signal in response to cyclic dinucleotides, conserved bacterial second messengers known to bind and activate murine STING signaling. Collectively, these findings detail an unexpected species-specific role for STING as a receptor for an anticancer drug and uncover important insights that may explain the failure of DMXAA in clinical trials for human cancer.

TLR agonists: our best frenemy in cancer immunotherapy

Various TLR agonists are currently under investigation in clinical trials for their ability to orchestrate antitumor immunity. The antitumor responses are largely attributed to their aptitude to stimulate APCs such as DCs which in turn, activate tumor-specific T cell responses. However, there is a potential for TLR signaling to occur on cells other than professional APCs that could negate antitumor responses or even worse, promote tumor growth. The impetus for this review is twofold. First, there is accumulating data demonstrating that the engagement of TLRs on different T cell subsets and different cancer types could promote tumor growth or conversely, contribute to antitumor responses. Second, the efficacy of TLR agonists as monotherapies to treat cancer patients has been limited. In this review, we discuss how TLR signaling within different T cell subsets and cancer cells can potentially impact the generation of antitumor responses. Based on evidence from preclinical models and clinical trials, we draw attention to several criteria that we believe must be considered when selecting TLR agonists for developing effective immunotherapeutic strategies against cancer.

Inflammation and colorectal cancer: colitis-associated neoplasia

Connection between inflammation and cancer is a rapidly developing field. Epidemiological data suggests that inflammation along with distinct arms of host immune system plays a very important role in the development and progression of many different cancers. Inflammatory bowel disease (IBD) is an important risk factor for the development of colon cancer, namely, colitis-associated cancer (CAC). The molecular mechanisms by which inflammation promotes cancer development are still being uncovered and may differ between CAC and other forms of colorectal cancer. Recent work has shed light on the role of distinct immune cells, cytokines, and other immune mediators in virtually all of the steps of colonic tumorigenesis, including tumor initiation and promotion as well as progression and metastasis. The close proximity of colonic tumors to the myriad of intestinal microbes, as well as instrumental role of microbiota in IBD, introduces microbes as new players capable of triggering inflammation and possibly promoting tumorigenesis. Various mechanisms of CAC tumorigenesis as well as new possible hints for the future approaches for prevention and therapy are discussed in this review.

Toll-like receptor 4 signaling is involved in PACAP-induced neuroprotection in BV2 microglial cells under OGD/reoxygenation

OBJECT

The neuroprotective effects of pituitary adenylate cyclise-activating polypeptide (PACAP) have been well documented in vivo and in vitro. However, the mechanisms by which PACAP protected microglia from ischemic/hypoxic injury via inhibition of microglia activation remain unclear. Toll-like receptor 4 (TLR4) plays a considerable role in the induction of innate immune and inflammatory responses. The purpose of this study is to investigate the effect of PACAP on the oxygen and glucose deprivation (OGD)/reoxygenation BV2 microglia and to explore the role of TLR4/myeloid differentiation protein 88 (MyD88)/nuclear factor-kappa B (NF-kappaB) pathway in the neuroprotective effects of PACAP.

METHODS

We conducted OGD/reoxygenation by placing BV2 microglia into an airtight chamber and in glucose-free medium. BV2 microglia cell viability was determined by MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazoliumbromide] assay. Western blot was utilized to detect TLR4, MyD88 expression, inhibitory protein of NF-kappaB (IkappaB) phosphorylation/degradation, NF-kappaB activation. Level of tumor necrosis factor-alpha (TNF-alpha) in culture medium was measured with enzyme-linked immunosorbent assay (ELISA). Apoptosis was determined by flow cytometry.

RESULTS

We found that pretreatment with PACAP to BV2 cells immediately before OGD/reoxygenation significantly alleviated microglia hypoxic injury. PACAP inhibited upregulation of TLR4, MyD88 and NF-kappaB in BV2 microglial cells exposed to OGD/reoxygenation. PACAP administration also significantly reduced the production of proinflammatory cytokines and apoptosis in BV2 microglia exposed to OGD/reoxygenation.

DISCUSSION

Pretreatment with PACAP inhibited activation of the TLR4/MyD88/NF-kappaB signaling pathway and decreased inflammatory cytokine levels, as well as apoptosis in microglia, thereby attenuating microglia hypoxic injury. Our results suggested that TLR4-mediated MyD88-dependent signaling pathway contributed to neuroprotection of PACAP to microglia against OGD/reoxygenation.

Receptor cross-talk spatially restricts p-ERK during TLR4 stimulation of autoreactive B cells

To maintain tolerance, autoreactive B cells must regulate signal transduction from the BCR and TLRs. We recently identified that dendritic cells and macrophages regulate autoreactive cells during TLR4 activation by releasing IL-6 and soluble CD40 ligand (sCD40L). These cytokines selectively repress Ab secretion from autoreactive, but not antigenically naive, B cells. How IL-6 and sCD40L repress autoantibody production is unknown. In this work, we show that IL-6 and sCD40L are required for low-affinity/avidity autoreactive B cells to maintain tolerance through a mechanism involving receptor cross-talk between the BCR, TLR4, and the IL-6R or CD40. We show that acute signaling through IL-6R or CD40 integrates with chronic BCR-mediated ERK activation to restrict p-ERK from the nucleus and represses TLR4-induced Blimp-1 and XBP-1 expression. Tolerance is disrupted in 2-12H/MRL/lpr mice where IL-6 and sCD40L fail to spatially restrict p-ERK and fail to repress TLR4-induced Ig secretion. In the case of CD40, acute signaling in B cells from 2-12H/MRL/lpr mice is intact, but the chronic activation of p-ERK emanating from the BCR is attenuated. Re-establishing chronically active ERK through retroviral expression of constitutively active MEK1 restores tolerance upon sCD40L, but not IL-6, stimulation, indicating that regulation by IL-6 requires another signaling effector. These data define the molecular basis for the regulation of low-affinity autoreactive B cells during TLR4 stimulation; they explain how autoreactive but not naive B cells are repressed by IL-6 and sCD40L; and they identify B cell defects in lupus-prone mice that lead to TLR4-induced autoantibody production.

[Biologic modulation of ionizing radiation by Toll-like receptors agonists: towards an increase in the therapeutic index of radiotherapy?]

Toll-like receptors are ubiquitous and very well conserved throughout evolution, with important functions mediating innate and adaptative immunological mechanisms. The importance of these receptors and their agonists has been recently pointed out in immunology and cancerology, although the accurate underlying mechanisms are still under investigation. The association of agonists of these receptors with ionizing radiation has been studied in preclinical experiments with promising results. Part of these compounds is flagellin, which seems to be able to modulate the radiosensitivity of both tumors and healthy tissues.

Autoreactive preplasma cells break tolerance in the absence of regulation by dendritic cells and macrophages

The ability to induce Ab responses to pathogens while maintaining the quiescence of autoreactive cells is an important aspect of immune tolerance. During activation of TLR4, dendritic cells (DCs) and macrophages (MFs) repress autoantibody production through their secretion of IL-6 and soluble CD40L (sCD40L). These soluble mediators selectively repress B cells chronically exposed to Ag, but not naive cells, suggesting a means to maintain tolerance during TLR4 stimulation, yet allow immunity. In this study, we identify TNF-α as a third repressive factor, which together with IL-6 and CD40L account for nearly all the repression conferred by DCs and MFs. Similar to IL-6 and sCD40L, TNF-α did not alter B cell proliferation or survival. Instead, it reduced the number of Ab-secreting cells. To address whether the soluble mediators secreted by DCs and MFs functioned in vivo, we generated mice lacking IL-6, CD40L, and TNF-α. Compared to wild-type mice, these mice showed prolonged anti-nuclear Ab responses following TLR4 stimulation. Furthermore, adoptive transfer of autoreactive B cells into chimeric IL-6(-/-) × CD40L(-/-) × TNF-α(-/-) mice showed that preplasma cells secreted autoantibodies independent of germinal center formation or extrafollicular foci. These data indicate that in the absence of genetic predisposition to autoimmunity, loss of endogenous IL-6, CD40L, and TNF-α promotes autoantibody secretion during TLR4 stimulation.

Association between C13ORF31, NOD2, RIPK2 and TLR10 polymorphisms and urothelial bladder cancer

Several evidences have been published linking polymorphism in genes involved in chronic or recurrent inflammation with increased tumor risk and progression. Nevertheless the influence of innate immune receptors in urothelial cancer risk and characteristics has not been sufficient explored. We studied the possible association of polymorphisms in genes encoding NOD2, RIPK2, TLR10 and C13ORF31 with the risk, clinical/pathological characteristics and outcomes of urothelial cancer. We have found association between RIPK2 (rs42490) and cancer risk (AA vs AT&TT, p=0042). In addition, we found statistical differences in TLR10 (rs4129009) gen between low and high tumor infiltration stage (p=0.033). NOD2 (rs9302752) and RIPK2 (rs42490) were found to be associated with development of lymph node metastasis (p=0.011 and p=0.015). Importantly we detect association of TLR10 (Log Rank=0.035) and RIPK2 (Log Rank=0040) with overall survival. Multivariate Cox analysis revealed that both SNPs were survival prognosis factor independent of tumor stage and grade. Our results indicate that innate immunity receptors play a role in modulating urothelial cancer risk and progression.

Inherited variation in pattern recognition receptors and cancer: dangerous liaisons?

The group of pattern recognition receptors includes families of Toll-like receptors, NOD-like receptors, C-type lectin receptors, and RIG-I-like receptors. They are key sensors for a number of infectious agents, some of which are carcinogenic, and they launch an immune response against them. Inherited structural variation in genes encoding these receptors and proteins of their signaling pathways may affect their function, modulating cancer risk and features of cancer progression. Relevant malignancies, valuable gene polymorphisms, prime questions about future directions, and answers to these questions are analyzed in this review. It is possible to suggest that polymorphisms of genes encoding pattern recognition receptors and proteins of their signaling pathways may be associated with almost all cancer types, particularly with those in which carcinogenic infectious agents are responsible for the substantial share of cases (namely gastric cancer, colorectal cancer, liver cancer, cervical cancer, and nasopharyngeal carcinoma). The concept of selection of polymorphisms for further oncogenomic investigation, based on a combination of results from basic and epidemiological studies, is proposed.

Contribution of gut microbiota to colonic and extracolonic cancer development

It is estimated that 20% of malignancies worldwide can be attributed to infections, i.e. about 1.2 million cases per year. A typical example of the association between bacterial infection and gastrointestinal malignancies is Helicobacter pylori infection with both gastric cancer and mucosa-associated lymphoid tissue lymphoma. Bacteria are an important component of the human body. The human intestine contains >500 different types of microorganisms, the 'gut microbiota', that play important functions such as energetic metabolism, proliferation and survival of epithelial cells, and protection against pathogens. Chronic alteration of intestinal microbiota homeostasis, 'dysbiosis', could promote many diseases, including cancer. The mechanisms by which bacteria may induce carcinogenesis include chronic inflammation, immune evasion, and immune suppression. There are three effector pathways of T helper (Th) cell differentiation: Th1 responses promoted by procarcinogenic signal transducer and activator of transcription (Stat)1 and Stat4 signaling, Th2 responses promoted by Stat6 signaling, and Th17 responses promoted by Stat3 signaling. Interestingly, Th1 responses, driven by IL-12 and characterized by IFN-γ production, are typically anticarcinogenic, whereas Th17 responses are activated in various cancers. Furthermore, a T regulatory response, driven by IL-10 and TGF-β, counterbalances the proinflammatory effect of Th17 responses. Elevated numbers of T regulatory cells suppress the innate and adaptive immune responses, thereby contributing to tumor progression. The emerging relationship between gut microbiota and cancer has prompted new ways of thinking about cancer prevention and has led to the development of noninvasive diagnostic tests and innovative treatments, such as with probiotics. However, although in vitro and animal model studies suggest a protective anticancer effect of probiotics, the results of human epidemiological studies are controversial.

Association of polymorphisms in TLR genes and in genes of the Toll-like receptor signaling pathway with cancer risk

Toll-like receptors (TLRs) constitute a family of receptors directly recognizing a wide spectrum of exogenous and endogenous ligands playing the key role in realization of innate and adaptive immune response, and participating in the processes of cell proliferation, survival, apoptosis, angiogenesis, tissue remodeling and repair. Polymorphisms in TLR genes may shift balance between pro- and anti-inflammatory cytokines, modulating the risk of infection, chronic inflammation and cancer. The short list of TLR polymorphisms perspective for oncogenomic investigations can include rs10008492, rs4833103, rs5743815, rs11466657, rs7696175 (TLR1-TLR6-TLR10 gene cluster); rs3804100, rs4696480, -196 - -174 del (Delta22), GT-microsatellite polymorphism (TLR2); 829A/C (TLR3); rs5743836, rs352140 (TLR9). The extended list can additionally include rs4833095 rs5743551, rs5743618 (TLR1); rs5743704, rs62323857, rs1219178642 (TLR2); rs5743305, rs3775291, rs121434431, rs5743316 (TLR3); rs5744168 (TLR5); rs179008 (TLR7); rs3764880, rs2407992 (TLR8); rs352139, rs187084, rs41308230, rs5743844 (TLR9); rs4129009 (TLR10). General reasons for discrepancies between studies are insufficiency of sample size, age/gender/BMI/ethnic/racial differences, differences in prevalence of infectious agent in case and control groups, differences in immune response caused by specific ligand, differences in stratification, methods of diagnostics of cancer or chronic inflammatory conditions, genotyping methods, and chance. Future well-designed studies on large samples should shed light on the significance of TLR polymorphisms for cancer prevention.

Endogenous toll-like receptor ligands and their biological significance

Toll-like receptors (TLRs), a family of pattern recognition receptors, recognize and respond to conserved components of microbes and play a crucial role in both innate and adaptive immunity. In addition to binding exogenous ligands derived from pathogens, TLRs interact with endogenous molecules released from damaged tissues or dead cells and regulate many sterile inflammation processes. Putative endogenous TLR ligands include proteins and peptides, polysaccharides and proteoglycan, nucleic acids and phospholipids, which are cellular components, particularly extracellular matrix degradation products. Accumulating evidence demonstrates that endogenous ligand-mediated TLR signalling is involved in pathological conditions such as tissue injury, repair and regeneration; autoimmune diseases and tumorigenesis. The ability of TLRs to recognize endogenous stimulators appears to be essential to their function in regulating non-infectious inflammation. In this review, we summarize current knowledge of endogenous TLR ligands and discuss the biological significance of TLR signalling triggered by endogenous ligands in several sterile inflammation conditions.

Toll-like receptors in acute liver injury and regeneration

Liver is the lymphoid organ with an overwhelming innate immune system, which functions as a filter organ at the first line between the digestive tract and the rest of the body, with receiving 80% of the blood supply through portal vein. TLRs are widely expressed on parenchymal and non-parenchymal cells in the liver, which play critical roles for the liver health. Recent studies indicate that TLR-medicated signals have been involved in almost all liver diseases such as acute and chronic hepatitis, liver fibrosis and cirrhosis, alcoholic and non-alcoholic liver disease, ischemia/reperfusion liver injury, liver regeneration and hepatocellular carcinoma. In this review, the expressions of TLRs in hepatic cell populations including hepatocytes, LSECs, Kupffer cells, lymphocytes, DCs, biliary epithelial cells and HSCs, and TLR ligands and signaling in the liver are summarized. Further, recent advances in the roles of TLRs in acute liver injury and regeneration as mediator and regulator, and their potential therapeutic targets are discussed.