Down-regulation of Toll-like receptor 7 expression in hepatitis-virus-related human hepatocellular carcinoma

Biphasic modulation of the TLR7 signaling pathway in bovine alphaherpesvirus (BoAHV) infection of neural cells

The study investigates the role of TLR7 in the modulation of the immune response during infection of neuronal cells by bovine alphaherpesvirus (BoAHV) types 1 and 5. TLR7 is essential for detecting viral RNA and activating immune pathways. In BoAHV-1 infection, TLR7 is upregulated early and persistently. In contrast, BoAHV-5 initially suppresses TLR7 expression, with a delayed upregulation at the end of the infectious cycle, reflecting the ability of the virus to evade early immune detection. Furthermore, BoAHV-1 induces a strong activation of MyD88 and NF-κB, leading to rapid viral replication, while BoAHV-5 triggers a weaker immune response, resulting in slower viral replication during the initial hours of infection. Additionally, BoAHV-1 progressively activates IRF-7 whereas BoAHV-5 shows delayed IRF-7 activation. Nevertheless, BoAHV-5 induces a strong IFNα/β response. The antiviral effect of the TLR7 agonist, Imiquimod was evident at the late phase of BoAHV-5 infection and it was mediated by IFN-β. These findings suggest that targeting TLR7 signaling could be a potential therapeutic approach to modulate immune responses and control viral replication. However, the effectiveness of TLR7 agonists like Imiquimod may vary depending on the virus type and its immune evasion strategies, highlighting the need for further research to explore other molecules in the TLR7 pathway.

Evaluation of immune-modulating drugs for use in drug-eluting microsphere transarterial embolization

Cancer immunotherapy has yet to reach its full potential due in part to limited response rates and side effects inherent to systemic delivery of immune-modulating drugs. Local administration of immunotherapy using drug-eluting embolic (DEE) microspheres as drug delivery vehicles for direct infusion into tumor-feeding arteries might increase and prolong tumor drug concentrations and reduce systemic drug exposure, potentially improving the risk-to-benefit ratio of these agents. The purpose of this study was to evaluate the ability of four immune modulators affecting two different immune pathways to potentiate replication of immune cells from a woodchuck model of hepatocellular carcinoma. DSR 6434, a Toll-like receptor agonist, and BMS-202, a PD-L1 checkpoint inhibitor, induced immune cell replication and were successfully loaded into radiopaque DEE microspheres in high concentrations. Release of DSR 6434 from the DEE microspheres was rapid (t99% = 0.4 h) upon submersion in a physiologic saline solution while BMS-202 demonstrated a more sustained release profile (t99% = 17.9 h). These findings demonstrate the feasibility of controlled delivery of immune-modulating drugs via a local DEE microsphere delivery paradigm.

Host Innate Immunity Against Hepatitis Viruses and Viral Immune Evasion

Hepatitis viruses are primary causative agents of hepatitis and represent a major source of public health problems in the world. The host innate immune system forms the first line of defense against hepatitis viruses. Hepatitis viruses are sensed by specific pathogen recognition receptors (PRRs) that subsequently trigger the innate immune response and interferon (IFN) production. However, hepatitis viruses evade host immune surveillance via multiple strategies, which help compromise the innate immune response and create a favorable environment for viral replication. Therefore, this article reviews published findings regarding host innate immune sensing and response against hepatitis viruses. Furthermore, we also focus on how hepatitis viruses abrogate the antiviral effects of the host innate immune system.

Nucleic Acid-Induced Signaling in Chronic Viral Liver Disease

A hallmark for the development and progression of chronic liver diseases is the persistent dysregulation of signaling pathways related to inflammatory responses, which eventually promotes the development of hepatic fibrosis, cirrhosis and hepatocellular carcinoma (HCC). The two major etiological agents associated with these complications in immunocompetent patients are hepatitis B virus (HBV) and hepatitis C virus (HCV), accounting for almost 1.4 million liver disease-associated deaths worldwide. Although both differ significantly from the point of their genomes and viral life cycles, they exert not only individual but also common strategies to divert innate antiviral defenses. Multiple virus-modulated pathways implicated in stress and inflammation illustrate how chronic viral hepatitis persistently tweaks host signaling processes with important consequences for liver pathogenesis. The following review aims to summarize the molecular events implicated in the sensing of viral nucleic acids, the mechanisms employed by HBV and HCV to counter these measures and how the dysregulation of these cellular pathways drives the development of chronic liver disease and the progression toward HCC.

Serum level and single-nucleotide polymorphisms of toll-like receptor-7 among urinary bladder cancer Iraqi patients

Background

Toll-like receptor 7 (TLR7), a member of TLR family, plays a pivotal role in pathogenesis of different malignancies. Among these is urinary bladder cancer (UBC), which has not been extensively studied. Therefore, it was aimed to determine TLR7 serum level in UBC patients and evaluate its association with some demographic and clinicopathological characteristics. In addition, four TLR7 single-nucleotide polymorphisms (SNPs: rs179018, rs179019, rs179020, and rs179021) were investigated to determine their susceptibility role in UBC and inspect SNP’s impact on TLR7 level. Sixty-six UBC Iraqi patients were enrolled in this case-control study. Two control samples were also involved, 40 urinary tract infection (UTI) patients, and 48 healthy control subjects.

Results

Male gender, older age, and cigarette-smoking are risk factors for UBC. TLR7 level showed a significant decreased median in UBC patients compared to UTI patients or control (1.4 vs. 8.1 and 9.5 ng/ml, respectively; p < 0.001). The decrease was more pronounced in males, age group ≥ 48 years, cigarette-smokers, alcohol non-consumers, clinical stages I–II, and superficial tumor, as well as patients with family history of cancer and untreated patients. Mitomycin C and Bacillus Calmette–Guérin therapies tended to increase TLR7 level. Among the four investigated SNPs, only rs179019 C allele showed significantly uncorrected increased frequency in UBC males compared to control males (p = 0.038), while among UTI females, C allele frequency maintained a significantly corrected decreased frequency compared to control females (p = 0.005). Some SNPs influenced serum level of TLR7, but a significant impact was recorded for rs179019 in UTI females (p = 0.006).

Conclusions

Downregulation of TLR7 is suggested to have a role in etiology and pathogenesis of UBC, especially the male, elderly and smoker patients. Mitomycin C and Bacillus Calmette–Guérin may enhance TLR7 production in the blood of UBC patients. TLR7 SNPs are suggested to influence susceptibility to develop UBC, and their potential in impacting TLR7 serum level is augmented.

Peripheral blood and hepatic Toll-like receptor 7 expression and interferon lambda 1 levels in chronic hepatitis C: Relation to virus replication and liver injury

BACKGROUND AND AIM

Toll-like receptor 7 (TLR7) can recognize single-stranded RNA viruses like hepatitis C virus (HCV) with subsequent induction of different interferon (IFN) types including IFN lambda (IFNL), which activate an immediate anti-viral response. However, the role of TLR7 in inflammation and fibrosis, characteristics of HCV-induced liver injury, is still controversial. The present work was designed to investigate the potential role of TLR7 and IFNL1 in chronic hepatitis C (CHC) in relation to viral replication and liver injury.

METHODS

Forty two treatment-naïve patients with CHC and 20 healthy subjects were enrolled in the study. TLR7 expression on peripheral blood CD14+ monocytes was studied by color flow cytometry and the frequency of TLR7+CD14+ cells was expressed as percentage of total monocyte count. Quantification of IFNL1 levels in serum was determined using enzyme-linked immunosorbant assay. Liver biopsies were examined for assessment of histological activity grade (A0-A3) and fibrosis stage (F0-F4) according to METAVIR scoring system as well as steatosis grade. Immunohistochemical staining was performed using human antibodies against TLR7 and IFNL1 and was scored semi-quantitatively (score 0-3). Hepatic expression of TLR7 and IFNL1 was further classified using a two-grade scale as low expression (score 0 or 1) and high expression (score 2 or 3).

RESULTS

Percentages of circulating TLR7+CD14+ monocytes and serum IFNL1 levels were significantly higher in patients with CHC than in healthy controls (P = 0.025 and P < 0.001 respectively) and were positively correlated with corresponding hepatic TLR7 and IFNL1 expression (P < 0.001 and P = 0.010 respectively). Significantly lower peripheral blood and hepatic TLR7 expression and IFNL1 levels were found in patients with viral loads between 200,000-600,000 IU/ml and >600,000 IU/ml than in those with viral load <200,000 IU/ml (P < 0.05), in patients with severe necroinflammation than in those with mild-to-moderate necroinflammation (P < 0.05) and in patients with advanced fibrosis than in those with early fibrosis (P < 0.01). Also, changes in TLR7 expression and IFNL1 production in peripheral blood and the liver were inversely correlated with serum levels of aspartate and alanine aminotransferases (P < 0.05) and HCV RNA (P < 0.01), histological activity grade (P < 0.01) and fibrosis stage (P < 0.01). By plotting receiver operating characteristics (ROC) curve, serum IFNL1 showed higher sensitivity and specificity than percentages of circulating TLR7+CD14+ monocytes in discriminating patients with CHC according to the severity of hepatic necroinflammation (area under the curve (AUC) = 0.901 vs. 0.816 respectively) and fibrosis (AUC = 0.971 vs. 0.825 respectively) at a cut-off value of 44.75 pg/ml and 10.25% respectively.

CONCLUSIONS

TLR7 activation and IFNL1 production in CHC may play an important role in controlling viral replication and limiting hepatic inflammation and fibrosis and their downregulation may result in viral persistence and disease progression. The immunoregulatory role of TLR7-IFNL1 pathway in the pathogenesis of chronic HCV infection should be further studied. Clinical trials with a large number of patients are needed to assess the usefulness of serum IFNL1 as a potential biomarker for severity of liver injury in chronic HCV infection and other liver diseases.

Modulation of the Immune System in Chronic Hepatitis C and During Antiviral Interferon-Free Therapy

The treatment of patients with chronic hepatitis C virus (HCV) infection has changed tremendously over the past 2 years, with an increasing variety of all-oral direct-acting antiviral (DAA) treatment regimens available for different HCV genotypes and distinct clinical settings. These treatments have significantly improved safety in patients with advanced liver disease compared with interferon (IFN)-based regimens. HCV modifies the human immune system to escape immunosurveillance via several mechanisms. One of the basic mechanisms of HCV is the ability to “switch” the immune response by reducing the activity of cells responsible for the elimination of virus-infected cells. IFN-free DAA treatment regimens provide a unique opportunity to assess the effect of HCV elimination on the immune system. Abrupt changes in the immune system can in some cases be responsible for two alarming processes: viral reactivation in patients with chronic hepatitis B and recurrence of hepatocellular carcinoma in patients with previous successful cancer treatment.

TLR7-let-7 Signaling Contributes to Ethanol-Induced Hepatic Inflammatory Response in Mice and in Alcoholic Hepatitis

BACKGROUND

Toll-like receptor 7 (TLR7) is an endosomal TLR that is activated by single-stranded RNA, including endogenous microRNAs (e.g., let-7b). Increased hepatic expression of TLRs, microRNAs, and inflammatory mediators is linked to ethanol (EtOH) exposure and to alcoholic liver disease (ALD). ALD invovles chronic hepatic inflammation that can progress to alcoholic hepatitis (AH), a particularly severe form of ALD. This study aimed to investigate TLR7 expression in patients with different liver disease phenotypes and in mouse liver following alcohol exposure.

METHODS

Hepatic mRNA expression was determined by RNA sequencing of liver tissue from patients with liver disease or normal liver tissue. Mice were exposed to subchronic EtOH followed by administration of the TLR7 agonist imiquimod. Primary human hepatocytes were exposed to EtOH or imiquimod in vitro.

RESULTS

RNAseq analysis revealed that hepatic expression of TLR7 and let-7b microRNA, an endogenous TLR7 ligand, was significantly increased in AH patients. Hepatic expression of TLR7 and let-7b positively correlated with hepatic IL-8 mRNA expression. In mice, EtOH increased hepatic TLR7 mRNA expression and enhanced imiquimod-induced expression of the pro-inflammatory mediators TNFα, MCP-1, and iNOS. In vitro, EtOH significantly increased hepatocyte TLR7 mRNA and the TLR7 agonist, imiquimod, induced hepatocyte expression of TNFα and IL-8 mRNA. EtOH also increased the release of let-7b in microvesicles from hepatocytes, suggesting that EtOH can increase the expression of both the receptor and its endogenous ligand.

CONCLUSIONS

These studies suggest that increased TLR7 signaling caused by increased expression of TLR7 and its endogenous ligand let-7b may contribute to the enhanced inflammatory response associated with AH.

Lipid rafts promote liver cancer cell proliferation and migration by up-regulation of TLR7 expression

Hepatocellular carcinoma (HCC) occurs predominantly in patients with underlying chronic liver disease and cirrhosis. Toll-like receptors (TLRs) play an important role in innate immune responses and TLR signaling has been associated with various chronic liver diseases. Lipid rafts provide the necessary microenvironment for certain specialized signaling events to take place, such as the innate immune recognition. The purpose of this study was to determine the pattern of TLR7 expression in HCC, how to recruit TLR7 into lipid rafts responded to ligands and whether targeting TLR7 might have beneficial effects. The study group was comprised of 130 human liver tissues: 23 chronic hepatitis B (CHB), 18 liver cirrhosis (LC), 68 HCC and 21 normal livers. The expression of TLR7 was evaluated using immunohistochemistry, western blotting, and flow cytometry. Proliferation and migration of human HepG2 cells were studied following stimulation of TLR7 using the agonist gardiquimod and inhibition with a specific antagonist 20S-protopanaxadiol (aPPD). The activation of lipid raft-associated TLR7 signaling was measured using western blotting, double immunohistochemistry and immunoprecipitation in liver tissues and HepG2 cells. TLR7 expression was up-regulated in human HCC tissues and hepatoma cell line. Proliferation and migration of HepG2 cells in vitro increased significantly in response to stimulation of TLR7. TLR7 inhibition using aPPD significantly reduced HepG2 cell migration in vitro. The lipid raft protein caveolin-1 and flotillin-1 were involved with enhanced TLR7 signaling in HCC.

Innate immunity related pathogen recognition receptors and chronic hepatitis B infection

Innate immunity consists of several kinds of pathogen recognition receptors (PRRs), which participate in the recognition of pathogens and consequently activation of innate immune system against pathogens. Recently, several investigations reported that PRRs may also play key roles in the induction/stimulation of immune system related complications in microbial infections. Hepatitis B virus (HBV), as the main cause of viral hepatitis in human, can induce several clinical forms of hepatitis B and also might be associated with hepatic complications such as cirrhosis and hepatocellular carcinoma (HCC). Based on the important roles of PRRs in the eradication of microbial infections including viral infections and their related complications, it appears that the molecules may be a main part of immune responses against viral infections including HBV and participate in the HBV related complications. Thus, this review article has brought together information regarding the roles of PRRs in immunity against HBV and its complications.

Immunotherapy of Dual-Function Vector with Both Immunostimulatory and B-Cell Lymphoma 2 (Bcl-2)-Silencing Effects on Gastric Carcinoma

BACKGROUND Tumorigenesis is a kind of pathology marked by infinite proliferation and restrained apoptosis compared with normal cells. The abnormal expression of some proto-oncogenes and apoptosis inhibition are essential for tumor growth, which has been confirmed by molecular biologic and immunologic studies. The hypofunction of the host immune system also drives the development and metastasis of malignant tumors. Bcl-2, which has a critical role in regulating apoptosis, is overexpressed in several cancers. MATERIAL AND METHODS In this study, we constructed a dual-function small hairpin RNA (shRNA) vector containing an Bcl-2-silencing shRNA and a TLR7-stimulating ssRNA and examined it effect on tumor cell growth and proliferation. RESULTS Stimulation with this bi-functional vector in vitro promoted significant apoptosis of MFC cells by regulating the expression of apoptosis-related proteins and induced secretion of type I IFNs. Most importantly, this bi-functional vector more effectively inhibited subcutaneous MFC cell growth than did single shRNA and ssRNA treatment in vivo. Natural killer (NK) and CD4+ T cells were required for effective tumor suppression, and TLR7 was shown to play a helper role in the activation of NK cells and CD4+ T cells, possibly by regulating the expression of receptors or secretion of cytokines. CONCLUSIONS This bi-functional vector that contained ssRNA and shRNA may represent a promising approach for tumor therapy.

Toll-like receptors in hepatocellular carcinoma: potential novel targets for pharmacological intervention

INTRODUCTION

Toll-like receptors (TLRs) are expressed by a wide variety of cell types including immune cells. They play a crucial role in the inflammatory and host defense response against microorganisms, and triggering TLRs can mediate the activation of innate immunity. Furthermore, research suggests that various TLRs may function differently on different tumor cells. The change in TLR activity may elicit an anti-tumor activity in hepatocellular carcinoma (HCC) cells and may serve as a novel therapeutic target for HCC therapy.

AREAS COVERED

This review discusses the role of the TLR family in HCC and the underlying signaling pathway of TLRs as a form of pattern recognition receptor in mediating inflammation and HCC immunity responses. Agonists and antagonists of TLRs, which render TLRs as potential therapeutic targets, activate downstream molecules, subsequently causing HCC cell survival. The proliferation or protection against the development of HCC is also described.

EXPERT OPINION

A series of studies have highlighted a crucial role of TLRs in HCC and consider TLR signaling pathways as potential therapeutic targets for HCC. However, the conclusions of these studies are in part paradoxical and controversial. Thus, it is necessary to extend further research to help determine the signaling pathways involved.

The link between TLR7 signaling and hepatitis B virus infection

Toll-Like Receptors (TLRs) play crucial roles in recognition and induction of appropriate immune responses against viral infections, including hepatitis B. TLR7 detects intracellular viral single strand RNA which leads to the activation of several pro-inflammatory transcription factors via the MYD88 dependent pathway. Patients with prolonged infectious forms of hepatitis B, including active and inactive chronic forms, are unable to clear HBV from hepatocytes completely. It is believed that the differences in genetic and immunological parameters of the patients and clearance subjects, who successfully clear HBV infections, are the main factors responsible for allowing the long term infections to persist. It appears that defective expression of TLR7 may result in impaired immune responses against HBV. The aim of this review is to address the recent information regarding the crucial roles played by TLR7 in hepatitis B infection and also the main mechanisms used by HBV to escape from recognition by TLR7 in prolonged HBV infected patients. Considering that chronic hepatitis B infection is not yet curable, it could be possible to activate TLR7-related immunological pathways as a therapy directed towards persistent HBV infection. Hence, another aim of this study is to present recent developments of TLR7 agonists as a therapeutic strategy for chronic hepatitis B.

Decreased expression of TLR7 in gastric cancer tissues and the effects of TLR7 activation on gastric cancer cells

The present study aimed to determine the expression of Toll-like receptor 7 (TLR7) in gastric cancer tissues and investigate the effects of its activation on gastric cancer cells. Patients with gastric cancer (n=30) and patients without gastric cancer (control; n=14) who underwent gastroscopy were enrolled in the study. Gastric cancer and cancer-adjacent tissues were obtained from the patients with gastric cancer, and normal gastric epithelial tissues were obtained from the control patients. The TLR7 mRNA and protein expressions in different tissues were investigated by reverse transcription-quantitative polymerase chain reaction, western blotting and immunohistochemistry. The present study also determined the effects of TLR7 activation by the agonist imiquimod on TLR7 protein expression, proinflammatory cytokine secretion and viability in SGC-7901 gastric cancer cells. The mRNA and protein expression levels of TLR7 were significantly downregulated in gastric cancer tissues compared with cancer-adjacent and normal gastric epithelial tissues (P<0.01). Imiquimod significantly increased TLR7 protein expression levels, and promoted the secretion of proinflammatory cytokines tumor necrosis factor-α and interleukin-6 in SGC-7901 cells. Furthermore, imiquimod inhibited the proliferation of SGC-7901 cells in a dose- and time-dependent manner. Thus, the present study identified that the expression of TLR7 was decreased in gastric cancer tissues, and TLR7 activation enhanced TLR7 expression, promoted the production of proinflammatory cytokines and inhibited the growth of gastric cancer cells.

Hepatocytes as Immunological Agents

Hepatocytes are targeted for infection by a number of major human pathogens, including hepatitis B virus, hepatitis C virus, and malaria. However, hepatocytes are also immunological agents in their own right. In systemic immunity, they are central in the acute-phase response, which floods the circulation with defensive proteins during diverse stresses, including ischemia, physical trauma, and sepsis. Hepatocytes express a variety of innate immune receptors and, when challenged with pathogen- or damage-associated molecular patterns, can deliver cell-autonomous innate immune responses that may result in host defense or in immunopathology. Important human pathogens have evolved mechanisms to subvert these responses. Finally, hepatocytes talk directly to T cells, resulting in a bias toward immune tolerance.

Immunotherapy for hepatoma using a dual-function vector with both immunostimulatory and pim-3-silencing effects

Tumorigenesis is an immortalization process in which the growth of normal cells is uncontrolled and programmed cell death is suppressed. Molecular biologic and immunologic studies have revealed that the aberrant expression of some proto-oncogenes boosts proliferation and inhibits apoptosis, which is vital for tumor development. The hypofunction of the host immune system also drives the development and metastasis of malignant tumors. Pim-3, a member of the Pim family, is aberrantly expressed in several cancers. Data suggest that Pim-3 inhibits apoptosis by phosphorylating the proapoptotic BH3-only protein Bad. Here, we constructed a dual-function small hairpin RNA (shRNA) vector containing an shRNA targeting Pim-3 and a TLR7-stimulating ssRNA. Stimulation with this bi-functional vector in vitro promoted significant apoptosis of Hepa1-6 cells by regulating the expression of apoptosis-related proteins and induced secretion of type I IFNs. Most importantly, this bi-functional vector more effectively inhibited subcutaneous Hepa1-6 cell growth than did single shRNA and ssRNA treatment in vivo. Natural killer (NK), CD4(+) T, and CD8(+) T cells and macrophages were required for effective tumor suppression, and CD4(+) T cells were shown to play a helper role in the activation of NK cells, possibly by regulating the secretion of Th1 or Th2 cytokines. This ssRNA-shRNA bi-functional vector may represent a promising approach for tumor therapy.