Trial Watch: Experimental Toll-like receptor agonists for cancer therapy

Advances in Bacterial Lysate Immunotherapy for Infectious Diseases and Cancer

Antigenic cell fragments, pathogen-associated molecular patterns, and other immunostimulants in bacterial lysates or extracts may induce local and systemic immune responses in specific and nonspecific paradigms. Based on current knowledge, this review aimed to determine whether bacterial lysate has comparable functions in infectious diseases and cancer treatment. In infectious diseases, including respiratory and urinary tract infections, immune system activation by bacterial lysate can identify and combat pathogens. Commercially available bacterial lysates, including OM-85, Ismigen, Lantigen B, and LW 50020, were effective in children and adults in treating respiratory tract infections, chronic obstructive pulmonary disease, rhinitis, and rhinosinusitis with varying degrees of success. Moreover, OM-89, Uromune, Urovac, Urivac, and ExPEC4V showed therapeutic benefits in controlling urinary tract infections in adults, especially women. Bacterial lysate-based therapeutics are safe, well-tolerated, and have few side effects, making them a good alternative for infectious disease management. Furthermore, a nonspecific immunomodulation by bacterial lysates may stimulate innate immunity, benefiting cancer treatment. "Coley's vaccine" has been used to treat sarcomas, carcinomas, lymphomas, melanomas, and myelomas with varying outcomes. Later, several similar bacterial lysate-based therapeutics have been developed to treat cancers, including bladder cancer, non-small cell lung cancer, and myeloma; among them, BCG for in situ bladder cancer is well-known. Proinflammatory cytokines, including IL-1, IL-6, IL-12, and TNF-α, may activate bacterial antigen-specific adaptive responses that could restore tumor antigen recognition and response by tumor-specific type 1 helper cells and cytotoxic T cells; therefore, bacterial lysates are worth investigating as a vaccination adjuvants or add-on therapies for several cancers.

Adjuvant-free parenterally injectable vaccine platform that harnesses previously induced IgG as an antigen delivery carrier

Subunit vaccines are among the most useful vaccine modalities; however, their low immunogenicity necessitates the addition of adjuvants. Although adjuvants improve immune responses induced by vaccines, they often cause adverse reactions. To address this, we developed an adjuvant-free subunit vaccine platform that uses pre-existing antibodies generated from past infections or vaccinations as carriers for the delivery of vaccine antigens. Although we have confirmed the usefulness of this platform for nasal vaccines, its suitability as a parenterally injectable vaccine remains uncertain. Here, we verified the potential of our vaccine platform to harness pre-existing immunity for parenterally injectable vaccines. We generated RBD-HA by combining the receptor binding domain (RBD) derived from SARS-CoV-2 as a vaccine antigen with hemagglutinin (HA) sourced from influenza viruses to serve as the carrier protein. We revealed that subcutaneous vaccination with RBD-HA effectively triggered strong RBD-specific IgG responses in mice previously infected with the influenza A virus, even in the absence of adjuvants, and conferred protection to mice against SARS-CoV-2 upon challenge. Furthermore, we revealed that vaccination with RBD-HA did not induce an inflammatory response, such as inflammatory cytokine production, swelling, and recruitment of inflammatory immune cells, whereas conventional vaccines combined with adjuvants induced these adverse reactions. In addition, we demonstrated the remarkable versatility of this platform using a vaccine antigen derived from Streptococcus pneumoniae. These findings indicate the potential of this adjuvant-free vaccine platform to enhance the efficacy of parenterally injectable subunit vaccines and reduce adverse reactions.

Clinical landscape of macrophage-reprogramming cancer immunotherapies

Tumour-associated macrophages (TAMs) sustain a tumour-supporting and immunosuppressive milieu and therefore aggravate cancer prognosis. To modify TAM behaviour and unlock their anti-tumoural potential, novel TAM-reprogramming immunotherapies are being developed at an accelerating rate. At the same time, scientific discoveries have highlighted more sophisticated TAM phenotypes with complex biological functions and contradictory prognostic associations. To understand the evolving clinical landscape, we reviewed current and past clinically evaluated TAM-reprogramming cancer therapeutics and summarised almost 200 TAM-reprogramming agents investigated in more than 700 clinical trials. Observable overall trends include a high frequency of overlapping strategies against the same therapeutic targets, development of more complex strategies to improve previously ineffective approaches and reliance on combinatory strategies for efficacy. However, strong anti-tumour efficacy is uncommon, which encourages re-directing efforts on identifying biomarkers for eligible patient populations and comparing similar treatments earlier. Future endeavours will benefit from considering the shortcomings of past treatment strategies and accommodating the emerging complexity of TAM biology.

The role of the microscopic world: Exploring the role and potential of intratumoral microbiota in cancer immunotherapy

Microorganisms, including bacteria, viruses, and fungi, coexist in the human body, forming a symbiotic microbiota that plays a vital role in human health and disease. Intratumoral microbial components have been discovered in various tumor tissues and are closely linked to the occurrence, progression, and treatment results of cancer. The intratumoral microbiota can enhance antitumor immunity through mechanisms such as activating the stimulator of interferon genes signaling pathway, stimulating T and NK cells, promoting the formation of TLS, and facilitating antigen presentation. Conversely, the intratumoral microbiota might suppress antitumor immune responses by increasing reactive oxygen species levels, creating an anti-inflammatory environment, inducing T cell inactivation, and enhancing immune suppression, thereby promoting cancer progression. The impact of intratumoral microbiota on antitumor immunity varies based on microbial composition, interactions with cancer cells, and the cancer's current state. A deep understanding of the complex interactions between intratumoral microbiota and antitumor immunity holds the potential to bring new therapeutic strategies and targets to cancer immunotherapy.

The HPV viral regulatory mechanism of TLRs and the related treatments for HPV-associated cancers

Infection with human papillomavirus (HPV) typically leads to cervical cancer, skin related cancers and many other tumors. HPV is mainly responsible for evading immune tumor monitoring in HPV related cancers. Toll like receptors (TLRs) are particular pattern recognition molecules. When the body is facing immune danger, it can lead to innate and direct adaptive immunity. TLR plays an important role in initiating antiviral immune responses. HPV can affect the expression level of TLR and interfere with TLR related signaling pathways, resulting in sustained viral infection and even carcinogenesis. This paper introduces the HPV virus and HPV related cancers. We discussed the present comprehension of TLR, its expression and signaling, as well as its role in HPV infection. We also provided a detailed introduction to immunotherapy methods for HPV related diseases based on TLR agonists. This will provide insights into methods that support the therapeutic method of HPV related conditions with TLR agonists.

Edge Length-Programmed Single-Stranded RNA Origami for Predictive Innate Immune Activation and Therapy

Ligands targeting nucleic acid-sensing receptors activate the innate immune system and play a critical role in antiviral and antitumoral therapy. However, ligand design for in situ stability, targeted delivery, and predictive immunogenicity is largely hampered by the sophisticated mechanism of the nucleic acid-sensing process. Here, we utilize single-stranded RNA (ssRNA) origami with precise structural designability as nucleic acid sensor-based ligands to achieve improved biostability, organelle-level targeting, and predictive immunogenicity. The natural ssRNAs self-fold into compact nanoparticles with defined shapes and morphologies and exhibit resistance against RNase digestion in vitro and prolonged retention in macrophage endolysosomes. We find that programming the edge length of ssRNA origami can precisely regulate the degree of macrophage activation via a toll-like receptor-dependent pathway. Further, we demonstrate that the ssRNA origami-based ligand elicits an anti-tumoral immune response of macrophages and neutrophils in the tumor microenvironment and retards tumor growth in the mouse pancreatic tumor model. Our ssRNA origami strategy utilizes structured RNA ligands to achieve predictive immune activation, providing a new solution for nucleic acid sensor-based ligand design and biomedical applications.

Functional immune boosters; the herb or its dead microbiome? Antigenic TLR4 agonist MAMPs found in 65 medicinal roots and algae's

Background

Humans have been consuming medicinal plants (as herbs/ spices) to combat illness for centuries while ascribing beneficial effects predominantly to the plant/phytochemical constituents, without recognizing the power of obligatory resident microorganism' communities (MOCs) (live/dead bacteria, fungus, yeast, molds etc.) which remain after industrial microbial reduction methods. Very little is known about the taxonomic identity of residual antigenic microbial associated molecular patterns (MAMPs) debris in our botanical over the counter (OTC) products, which if present would be recognized as foreign (non-self) antigenic matter by host pattern recognition receptors (PRRs) provoking a host immune response; this the basis of vaccine adjuvants. As of today, only few research groups have removed the herbal MAMP biomass from herbs, all suggesting that immune activation may not be from the plant but rather its microbial biomass; a hypothesis we corroborate.

Purpose

The purpose of this work was to conduct a high through put screening (HTPS) of over 2500 natural plants, OTC botanical supplements and phytochemicals to elucidate those with pro-inflammatory; toll like receptor 4 (TLR4) activating properties in macrophages.

Study Design

The HTPS was conducted on RAW 264.7 cells vs. lipopolysaccharide (LPS) E. coli 0111:B4, testing iNOS / nitric oxide production ( NO 2 - ) as a perimeter endpoint. The data show not a single drug/chemical/ phytochemical and approximately 98 % of botanicals to be immune idle (not effective) with only 65 pro-inflammatory (hits) in a potency range of LPS. Method validation studies eliminated the possibility of false artifact or contamination, and results were cross verified through multiple vendors/ manufacturers/lot numbers by botanical species. Lead botanicals were evaluated for plant concentration of LPS, 1,3:1,6-β-glucan, 1,3:1,4-β-D-glucan and α-glucans; where the former paralleled strength in vitro. LPS was then removed from plants using high-capacity endotoxin poly lysine columns, where bioactivity of LPS null "plant" extracts were lost. The stability of E.Coli 0111:B4 in an acid stomach mimetic model was confirmed. Last, we conducted a reverse culture on aerobic plate counts (APCs) from select hits, with subsequent isolation of gram-negative bacteria (MacConkey agar). Cultures were 1) heat destroyed (retested/ confirming bioactivity) and 2) subject to taxonomical identification by genetic sequencing 18S, ITS1, 5.8 s, ITS2 28S, and 16S.

Conclusion

The data show significant gram negative MAMP biomass dominance in A) roots (e.g. echinacea, yucca, burdock, stinging nettle, sarsaparilla, hydrangea, poke, madder, calamus, rhaponticum, pleurisy, aconite etc.) and B) oceanic plants / algae's (e.g. bladderwrack, chlorella, spirulina, kelp, and "OTC Seamoss-blends" (irish moss, bladderwrack, burdock root etc), as well as other random herbs (eg. corn silk, cleavers, watercress, cardamom seed, tribulus, duckweed, puffball, hordeum and pollen). The results show a dominance of gram negative microbes (e.g. Klebsilla aerogenes, Pantoae agglomerans, Cronobacter sakazakii), fungus (Glomeracaea, Ascomycota, Irpex lacteus, Aureobasidium pullulans, Fibroporia albicans, Chlorociboria clavula, Aspergillus_sp JUC-2), with black walnut hull, echinacea and burdock root also containing gram positive microbial strains (Fontibacillus, Paenibacillus, Enterococcus gallinarum, Bromate-reducing bacterium B6 and various strains of Clostridium).

Conclusion

This work brings attention to the existence of a functional immune bioactive herbal microbiome, independent from the plant. There is need to further this avenue of research, which should be carried out with consideration as to both positive or negative consequences arising from daily consumption of botanicals highly laden with bioactive MAMPS.

Targeting CXCL9/10/11-CXCR3 axis: an important component of tumor-promoting and antitumor immunity

Chemokines are chemotactic-competent molecules composed of a family of small cytokines, playing a key role in regulating tumor progression. The roles of chemokines in antitumor immune responses are of great interest. CXCL9, CXCL10, and CXCL11 are important members of chemokines. It has been widely investigated that these three chemokines can bind to their common receptor CXCR3 and regulate the differentiation, migration, and tumor infiltration of immune cells, directly or indirectly affecting tumor growth and metastasis. Here, we summarize the mechanism of how the CXCL9/10/11-CXCR3 axis affects the tumor microenvironment, and list the latest researches to find out how this axis predicts the prognosis of different cancers. In addition, immunotherapy improves the survival of tumor patients, but some patients show drug resistance. Studies have found that the regulation of CXCL9/10/11-CXCR3 on the tumor microenvironment is involved in the process of changing immunotherapy resistance. Here we also describe new approaches to restoring sensitivity to immune checkpoint inhibitors through the CXCL9/10/11-CXCR3 axis.

Plants against cancer: the immune-boosting herbal microbiome: not of the plant, but in the plant. Basic concepts, introduction, and future resource for vaccine adjuvant discovery

The presence of microorganism communities (MOCs) comprised of bacteria, fungi, archaea, algae, protozoa, viruses, and the like, are ubiquitous in all living tissue, including plant and animal. MOCs play a significant role in establishing innate and acquired immunity, thereby influencing susceptibility and resistance to disease. This understanding has fostered substantial advancements in several fields such as agriculture, food science/safety, and the development of vaccines/adjuvants, which rely on administering inactivated-attenuated MOC pathogens. Historical evidence dating back to the 1800s, including reports by Drs Busch, Coley, and Fehleisen, suggested that acute febrile infection in response to "specific microbes" could trigger spontaneous tumor remission in humans. This discovery led to the purposeful administration of the same attenuated strains, known as "Coley's toxin," marking the onset of the first microbial (pathogen) associated molecular pattern (MAMPs or PAMPs)-based tumor immunotherapy, used clinically for over four decades. Today, these same MAMPS are consumed orally by billions of consumers around the globe, through "specific" mediums (immune boosting "herbal supplements") as carriers of highly concentrated MOCs accrued in roots, barks, hulls, sea algae, and seeds. The American Herbal Products Association (AHPA) mandates microbial reduction in botanical product processing but does not necessitate the removal of dead MAMP laden microbial debris, which we ingest. Moreover, while existing research has focused on the immune-modulating role of plant phytochemicals, the actual immune-boosting properties might instead reside solely in the plant's MOC MAMP laden biomass. This assertion is logical, considering that antigenic immune-provoking epitopes, not phytochemicals, are known to stimulate immune response. This review explores a neglected area of research regarding the immune-boosting effects of the herbal microbiome - a presence which is indirectly corroborated by various peripheral fields of study and poses a fundamental question: Given that food safety focuses on the elimination of harmful pathogens and crop science acknowledges the existence of plant microbiomes, what precisely are the immune effects of ingesting MAMPs of diverse structural composition and concentration, and where are these distributed in our botanicals? We will discuss the topic of concentrated edible MAMPs as acid and thermally stable motifs found in specific herbs and how these would activate cognate pattern recognition receptors (PPRs) in the upper gut-associated lymphoid tissue (GALT), including Peyer's patches and the lamina propria, to boost antibody titers, CD8+ and CD4+ T cells, NK activity, hematopoiesis, and facilitating M2 to M1 macrophage phenotype transition in a similar manner as vaccines. This new knowledge could pave the way for developing bioreactor-grown/heat-inactivated MOC therapies to boost human immunity against infections and improve tumor surveillance.

Intratumoral microbiota: roles in cancer initiation, development and therapeutic efficacy

Microorganisms, including bacteria, viruses, fungi, and other eukaryotes, play critical roles in human health. An altered microbiome can be associated with complex diseases. Intratumoral microbial components are found in multiple tumor tissues and are closely correlated with cancer initiation and development and therapy efficacy. The intratumoral microbiota may contribute to promotion of the initiation and progression of cancers by DNA mutations, activating carcinogenic pathways, promoting chronic inflammation, complement system, and initiating metastasis. Moreover, the intratumoral microbiota may not only enhance antitumor immunity via mechanisms including STING signaling activation, T and NK cell activation, TLS production, and intratumoral microbiota-derived antigen presenting, but also decrease antitumor immune responses and promote cancer progression through pathways including upregulation of ROS, promoting an anti-inflammatory environment, T cell inactivation, and immunosuppression. The effect of intratumoral microbiota on antitumor immunity is dependent on microbiota composition, crosstalk between microbiota and the cancer, and status of cancers. The intratumoral microbiota may regulate cancer cell physiology and the immune response by different signaling pathways, including ROS, β-catenin, TLR, ERK, NF-κB, and STING, among others. These viewpoints may help identify the microbiota as diagnosis or prognosis evaluation of cancers, and as new therapeutic strategy and potential therapeutic targets for cancer therapy.

Toll-like receptor-targeted anti-tumor therapies: Advances and challenges

Toll-like receptors (TLRs) are pattern recognition receptors, originally discovered to stimulate innate immune reactions against microbial infection. TLRs also play essential roles in bridging the innate and adaptive immune system, playing multiple roles in inflammation, autoimmune diseases, and cancer. Thanks to the immune stimulatory potential of TLRs, TLR-targeted strategies in cancer treatment have proved to be able to regulate the tumor microenvironment towards tumoricidal phenotypes. Quantities of pre-clinical studies and clinical trials using TLR-targeted strategies in treating cancer have been initiated, with some drugs already becoming part of standard care. Here we review the structure, ligand, signaling pathways, and expression of TLRs; we then provide an overview of the pre-clinical studies and an updated clinical trial watch targeting each TLR in cancer treatment; and finally, we discuss the challenges and prospects of TLR-targeted therapy.

BCG therapy downregulates HLA-I on malignant cells to subvert antitumor immune responses in bladder cancer

Patients with high-risk non muscle-invasive bladder cancer (NMIBC) frequently relapse after standard intravesical BCG therapy and may have a dismal outcome. Resistance mechanisms to such immunotherapy remain misunderstood. Here, using cancer cell lines, freshly resected human bladder tumors and cohorts of bladder cancer patients pre- and post-BCG therapy, we demonstrate two distinct patterns of immune subversion upon BCG relapse. In the first pattern, intracellular BCG infection of cancer cells induced a post-transcriptional downregulation of HLA-I membrane expression via an inhibition of the autophagy flux. Patients with HLA-I deficient cancer cells post-BCG therapy displayed a myeloid immunosuppressive tumor microenvironment with epithelial-to-mesenchymal transition (EMT) characteristics and dismal outcomes. Conversely, patients with HLA-I proficient cancer cells post-BCG therapy presented with CD8+ T cell tumor infiltrates, upregulation of inflammatory cytokines and inhibitory immune checkpoint molecules. Those patients had a very favorable outcome. We surmise that HLA-I expression in bladder cancers at relapse post-BCG does not result from immunoediting but rather from an immune subversion process directly induced by BCG on cancer cells, which predicts dismal prognosis. Cancer cells HLA-I scoring by immunohistochemistry (IHC) staining can be easily implemented by pathologists in routine practice in order to stratify future urothelial cancer patient treatment strategies.

A pH-/Enzyme-Responsive Nanoparticle Selectively Targets Endosomal Toll-like Receptors to Potentiate Robust Cancer Vaccination

Toll-like receptor (TLR) agonists are potent immune-stimulators that hold great potential in vaccine adjuvants as well as cancer immunotherapy. However, TLR agonists in free form are prone to be eliminated quickly by the circulatory system and cause systemic inflammation side effects. It remains a challenge to achieve precise release of TLR7/8 agonist in the native form at the receptor site in the endosomal compartments while keeping stable encapsulation and inactive in nontarget environment. Here, we report a pH-/enzyme-responsive TLR7/8 agonist-conjugated nanovaccine (TNV), which responds intelligently to the acidic environment and cathepsin B in the endosome, precisely releases TLR7/8 agonist to activate its receptor signaling at the endosomal membrane, stimulates DCs maturation, and provokes specific cellular immunity. In vivo experiments demonstrate outstanding prophylactic and therapeutic efficacy of TNV in mouse melanoma and colon cancer. The endosome-targeted responsive nanoparticle strategy provides a potential delivery toolbox of adjuvants to advance the development of tumor nanovaccines.

HTLV-1 Tax-specific memory cytotoxic T lymphocytes in long-term survivors of aggressive-type adult T-cell leukemia/lymphoma

Purpose

Adult T‐cell leukemia/lymphoma (ATLL) is a relatively refractory peripheral T‐cell lymphoma caused by human T‐cell lymphotropic virus type 1 (HTLV‐1). The objective of this study was to investigate the characteristics of long‐term survivors with ATLL.

Methods

We conducted an observational study of 75 aggressive‐type ATLL patients. Flow cytometry was conducted to analyze HTLV‐1 Tax‐specific cytotoxic T‐lymphocytes (CTLs) and T‐cell receptor Vβ gene repertoire.

Results

We first evaluated six long‐term survivors among 37 patients who were newly diagnosed with ATLL and then treated with intensive chemotherapy without mogamulizumab, a monoclonal antibody for C‐C chemokine receptor four antigen. Reversal of the CD4‐to‐CD8 ratio (CD4/CD8) in peripheral mononuclear cells was observed in all six patients. Three of these six patients showed reversed CD4/CD8 immediately after herpes virus infection. Four of these six patients who could be examined demonstrated long‐term maintenance of HTLV‐1 Tax‐specific CTLs. We subsequently identified four long‐term survivors among 38 patients who were newly diagnosed with ATLL and then treated with intensive chemotherapy plus mogamulizumab. All four patients showed reversed CD4/CD8, and three of the four patients contracted herpes virus infection during immunochemotherapy. Six of the total 10 patients were subjected to CTL analyses. Tax‐specific CTLs were observed, and the CTLs that were almost entirely composed of memory CTLs in all patients were recorded. HTLV‐1 provirus was also detected in all six patients.

Conclusions

These data suggest that Tax‐specific memory CTLs probably, together with anticancer agents, eradicate ATLL cells and exhibit long‐term preventive effects from relapse ATLL. Thus, the strong activation of cellular immunity, such as herpes virus infection, seems to be necessary to induce such a potent number of Tax‐specific CTLs.

A Novel Multiepitope Vaccine Against Bladder Cancer Based on CTL and HTL Epitopes for Induction of Strong Immune Using Immunoinformatics Approaches

Bladder cancer is well-known cancer in two forms of muscle-invasive and non-muscle-invasive bladder cancer which is responsible for annual deaths worldwide. Common therapies methods are somewhat successful; however, these methods have the limitations such as the side effects of chemotherapy which necessitate the requirement for new preventive methods against bladder cancer. Hence, we explain a novel designed multi-epitope vaccine against bladder cancer using the immunoinformatics tool. Three well-known BLCAP, PRAM, and BAGE4 antigens were evaluated due to most repetitive CTL and HTL epitopes binding. IFNγ and IL10 inducer potential of selected epitopes were investigated, as well as liner and conformational B-cell epitopes. Human beta-defensin 3 and PADRE sequence were added to construct as adjuvants, along with EAAAK, AAY, and GGGS linkers to fuse CTL and HTL epitopes. Results showed this construct encodes a soluble, non-toxic, and non-allergic protein with 70 kDa molecular weight. Modeled 3D structure of vaccine was docked whit Toll-Like Receptors (TLR) of 7/8. Docking, molecular dynamics simulation and MMBPSA analysis confirmed stability of vaccine-TLR complexes. The immunogenicity showed this construct could elicit humoral and cellular immune responses. In silico and immunoinformatics evaluations suggest that this construct is a recombinant candidate vaccine against bladder cancer.

Engineering Therapeutic Strategies in Cancer Immunotherapy via Exogenous Delivery of Toll-like Receptor Agonists

As a currently spotlighted method for cancer treatment, cancer immunotherapy has made a lot of progress in recent years. Among tremendous cancer immunotherapy boosters available nowadays, Toll-like receptor (TLR) agonists were specifically selected, because of their effective activation of innate and adaptive immune cells, such as dendritic cells (DCs), T cells, and macrophages. TLR agonists can activate signaling pathways of DCs to express CD80 and CD86 molecules, and secrete various cytokines and chemokines. The maturation of DCs stimulates naïve T cells to differentiate into functional cells, and induces B cell activation. Although TLR agonists have anti-tumor ability by activating the immune system of the host, their drawbacks, which include poor efficiency and remarkably short retention time in the body, must be overcome. In this review, we classify and summarize the recently reported delivery strategies using (1) exogenous TLR agonists to maintain the biological and physiological signaling activities of cargo agonists, (2) usage of multiple TLR agonists for synergistic immune responses, and (3) co-delivery using the combination with other immunomodulators or stimulants. In contrast to naked TLR agonists, these exogenous TLR delivery strategies successfully facilitated immune responses and subsequently mediated anti-tumor efficacy.

Inflammation and tumor progression: signaling pathways and targeted intervention

Cancer development and its response to therapy are regulated by inflammation, which either promotes or suppresses tumor progression, potentially displaying opposing effects on therapeutic outcomes. Chronic inflammation facilitates tumor progression and treatment resistance, whereas induction of acute inflammatory reactions often stimulates the maturation of dendritic cells (DCs) and antigen presentation, leading to anti-tumor immune responses. In addition, multiple signaling pathways, such as nuclear factor kappa B (NF-kB), Janus kinase/signal transducers and activators of transcription (JAK-STAT), toll-like receptor (TLR) pathways, cGAS/STING, and mitogen-activated protein kinase (MAPK); inflammatory factors, including cytokines (e.g., interleukin (IL), interferon (IFN), and tumor necrosis factor (TNF)-α), chemokines (e.g., C-C motif chemokine ligands (CCLs) and C-X-C motif chemokine ligands (CXCLs)), growth factors (e.g., vascular endothelial growth factor (VEGF), transforming growth factor (TGF)-β), and inflammasome; as well as inflammatory metabolites including prostaglandins, leukotrienes, thromboxane, and specialized proresolving mediators (SPM), have been identified as pivotal regulators of the initiation and resolution of inflammation. Nowadays, local irradiation, recombinant cytokines, neutralizing antibodies, small-molecule inhibitors, DC vaccines, oncolytic viruses, TLR agonists, and SPM have been developed to specifically modulate inflammation in cancer therapy, with some of these factors already undergoing clinical trials. Herein, we discuss the initiation and resolution of inflammation, the crosstalk between tumor development and inflammatory processes. We also highlight potential targets for harnessing inflammation in the treatment of cancer.

TLR3 agonists: RGC100, ARNAX, and poly-IC: a comparative review

Toll-like receptors 3 (TLR3) have been broadly studied among all TLRs over the last few decades together with its agonists due to their contribution to cancer regression. These agonists undeniably have some shared characteristics such as mimicking dsRNA but pathways through which they exhibit antitumor properties are relatively diverse. In this review, three widely studied agonists RGC100, ARNAX, and poly-IC are discussed along with their structural and physiochemical differences including the signaling cascades through which they exert their actions. Comparison has been made to identify the finest agonist with maximum effectivity and the least side effect profile.

PLGA-particle vaccine carrying TLR3/RIG-I ligand Riboxxim synergizes with immune checkpoint blockade for effective anti-cancer immunotherapy

With emerging supremacy, cancer immunotherapy has evolved as a promising therapeutic modality compared to conventional antitumor therapies. Cancer immunotherapy composed of biodegradable poly(lactic-co-glycolic acid) (PLGA) particles containing antigens and toll-like receptor ligands induces vigorous antitumor immune responses in vivo. Here, we demonstrate the supreme adjuvant effect of the recently developed and pharmaceutically defined double-stranded (ds)RNA adjuvant Riboxxim especially when incorporated into PLGA particles. Encapsulation of Riboxxim together with antigens potently activates murine and human dendritic cells, and elevated tumor-specific CD8+ T cell responses are superior to those obtained using classical dsRNA analogues. This PLGA particle vaccine affords primary tumor growth retardation, prevention of metastases, and prolonged survival in preclinical tumor models. Its advantageous therapeutic potency was further enhanced by immune checkpoint blockade that resulted in reinvigoration of cytotoxic T lymphocyte responses and tumor ablation. Thus, combining immune checkpoint blockade with immunotherapy based on Riboxxim-bearing PLGA particles strongly increases its efficacy.

Signal-transducing innate receptors in tumor immunity

The signal‐transducing innate receptors represent classes of pattern recognition receptors (PRRs) that play crucial roles in the first line of the host defense against infections by the recognition of pathogen‐derived molecules. Because of their poorly discriminative nature compared with antigen receptors of the adaptive immune system, they also recognize endogenous molecules and evoke immune responses without infection, resulting in the regulation of tumor immunity. Therefore, PRRs may be promising targets for effective cancer immunotherapy, either by activating or inhibiting them. Here, we summarize our current knowledge of signal‐transducing PRRs in the regulation of tumor immunity.

Gene expression profiling of morphologic subtypes of pancreatic ductal adenocarcinoma using surgical and EUS-FNB specimens

BACKGROUND/OBJECTIVES

Various classifications of pancreatic ductal adenocarcinoma (PDAC) based on RNA profiling resulted in two main subtypes. Kalimuthu and coworkers proposed a morphology-based classification that concurred with these subtypes. Immune therapy approaches in PDAC were so far disappointing. Morphologic PDAC subtypes may differ regarding key immune-oncology pathways. We aimed to examine the reproducibility and prognostic value of Kalimuthu's morphologic classification, and to evaluate differences between subtypes regarding gene expression related to tumor biology and immune-oncology.

METHODS

PDAC specimens from 196 patients were included, 108 consecutive chemotherapy-naïve surgical specimens and 88 endoscopic ultrasound-guided fine needle biopsies (EUS-FNBs). The specimens were evaluated as per Kalimuthu by two pancreatic pathologists, resulting in Group A and Group B tumors. Digital mRNA expression profiling was performed, on the surgical specimens using the NanoString IO360 panel of 770 key tumor biology related and 30 custom-genes, and on the EUS-FNBs using a targeted panel of 123 genes.

RESULTS

Morphologic subtyping reached substantial interobserver agreement between the two pathologists. In the surgical and EUS-FNB cohorts, 44.4% and 38.6% were Group A tumors, which were associated with improved survival. Group A showed higher expression of immune-related genes and cytokine/chemokine/interleukin signaling and Group B of genes related to cancer cell proliferation and cell cycle regulation. Hierarchical clustering based on significant differences in gene expression levels between Groups A and B revealed clusters with prognostic value.

CONCLUSIONS

Morphologic subtyping according to Kalimuthu is reproducible and holds prognostic value, in surgical as well as EUS-FNB specimens. As upregulation of immune-related genes was found in Group A, future studies should evaluate the potential of immune therapy approaches with special emphasis on this subtype of PDAC.

Trial watch: FDA-approved Toll-like receptor agonists for cancer therapy

Toll-like receptors (TLRs) have first been characterized for their capacity to detect conserved microbial components like lipopolysaccharide (LPS) and double-stranded RNA, resulting in the elicitation of potent (innate) immune responses against invading pathogens. More recently, TLRs have also been shown to promote the activation of the cognate immune system against cancer cells. Today, only three TLR agonists are approved by FDA for use in humans: the bacillus Calmette-Guérin (BCG), monophosphoryl lipid A (MPL) and imiquimod. BCG (an attenuated strain of Mycobacterium bovis) is mainly used as a vaccine against tuberculosis, but also for the immunotherapy of in situ bladder carcinoma. MPL (derived from the LPS of Salmonella minnesota) is included in the formulation of Cervarix®, a vaccine against human papillomavirus-16 and -18. Imiquimod (a synthetic imidazoquinoline) is routinely employed for actinic keratosis, superficial basal cell carcinoma, and external genital warts (condylomata acuminata). In this Trial Watch, we will summarize the results of recently completed clinical trials and discuss the progress of ongoing studies that have evaluated/are evaluating FDA-approved TLR agonists as off-label medications for cancer therapy.

Trial Watch: Tumor-targeting monoclonal antibodies in cancer therapy

In 1997, for the first time in history, a monoclonal antibody (mAb), i.e., the chimeric anti-CD20 molecule rituximab, was approved by the US Food and Drug Administration for use in cancer patients. Since then, the panel of mAbs that are approved by international regulatory agencies for the treatment of hematopoietic and solid malignancies has not stopped to expand, nowadays encompassing a stunning amount of 15 distinct molecules. This therapeutic armamentarium includes mAbs that target tumor-associated antigens, as well as molecules that interfere with tumor-stroma interactions or exert direct immunostimulatory effects. These three classes of mAbs exert antineoplastic activity via distinct mechanisms, which may or may not involve immune effectors other than the mAbs themselves. In previous issues of OncoImmunology, we provided a brief scientific background to the use of mAbs, all types confounded, in cancer therapy, and discussed the results of recent clinical trials investigating the safety and efficacy of this approach. Here, we focus on mAbs that primarily target malignant cells or their interactions with stromal components, as opposed to mAbs that mediate antineoplastic effects by activating the immune system. In particular, we discuss relevant clinical findings that have been published during the last 13 months as well as clinical trials that have been launched in the same period to investigate the therapeutic profile of hitherto investigational tumor-targeting mAbs.

TLR3/TICAM-1 signaling in tumor cell RIP3-dependent necroptosis

The engagement of Toll-like receptor 3 (TLR3) leads to the oligomerization of the adaptor TICAM-1 (TRIF), which can induces either of three acute cellular responses, namely, cell survival coupled to Type I interferon production, or cell death, via apoptosis or necrosis. The specific response elicited by TLR3 determines the fate of affected cells, although the switching mechanism between the two cell death pathways in TLR3-stimulated cells remains molecularly unknown. Tumor necrosis factor α (TNFα)-mediated cell death can proceed via apoptosis or via a non-apoptotic pathway, termed necroptosis or programmed necrosis, which have been described in detail. Interestingly, death domain-containing kinases called receptor-interacting protein kinases (RIPs) are involved in the signaling pathways leading to these two cell death pathways. Formation of the RIP1/RIP3 complex (called necrosome) in the absence of caspase 8 activity is crucial for the induction of necroptosis in response to TNFα signaling. On the other hand, RIP1 is known to interact with the C-terminal domain of TICAM-1 and to modulate TLR3 signaling. In macrophages and perhaps tumor cell lines, RIP1/RIP3-mediated necroptotic cell death can ensue the administration of the TLR agonist polyI:C. If this involved the TLR3/TICAM-1 pathway, the innate sensing of viral dsRNA would be linked to cytopathic effects and to persistent inflammation, in turn favoring the release of damage-associated molecular patterns (DAMPs) in the microenvironment. Here, we review accumulating evidence pointing to the involvement of the TLR3/TICAM-1 axis in tumor cell necroptosis and the subsequent release of DAMPs.

Trial watch: Peptide vaccines in cancer therapy

Prophylactic vaccination constitutes one of the most prominent medical achievements of history. This concept was first demonstrated by the pioneer work of Edward Jenner, dating back to the late 1790s, after which an array of preparations that confer life-long protective immunity against several infectious agents has been developed. The ensuing implementation of nation-wide vaccination programs has de facto abated the incidence of dreadful diseases including rabies, typhoid, cholera and many others. Among all, the most impressive result of vaccination campaigns is surely represented by the eradication of natural smallpox infection, which was definitively certified by the WHO in 1980. The idea of employing vaccines as anticancer interventions was first theorized in the 1890s by Paul Ehrlich and William Coley. However, it soon became clear that while vaccination could be efficiently employed as a preventive measure against infectious agents, anticancer vaccines would have to (1) operate as therapeutic, rather than preventive, interventions (at least in the vast majority of settings), and (2) circumvent the fact that tumor cells often fail to elicit immune responses. During the past 30 y, along with the recognition that the immune system is not irresponsive to tumors (as it was initially thought) and that malignant cells express tumor-associated antigens whereby they can be discriminated from normal cells, considerable efforts have been dedicated to the development of anticancer vaccines. Some of these approaches, encompassing cell-based, DNA-based and purified component-based preparations, have already been shown to exert conspicuous anticancer effects in cohorts of patients affected by both hematological and solid malignancies. In this Trial Watch, we will summarize the results of recent clinical trials that have evaluated/are evaluating purified peptides or full-length proteins as therapeutic interventions against cancer.

Trial watch: Prognostic and predictive value of the immune infiltrate in cancer

Solid tumors are constituted of a variety of cellular components, including bona fide malignant cells as well as endothelial, structural and immune cells. On one hand, the tumor stroma exerts major pro-tumorigenic and immunosuppressive functions, reflecting the capacity of cancer cells to shape the microenvironment to satisfy their own metabolic and immunological needs. On the other hand, there is a component of tumor-infiltrating leucocytes (TILs) that has been specifically recruited in the attempt to control tumor growth. Along with the recognition of the critical role played by the immune system in oncogenesis, tumor progression and response to therapy, increasing attention has been attracted by the potential prognostic and/or predictive role of the immune infiltrate in this setting. Data from large clinical studies demonstrate indeed that a robust infiltration of neoplastic lesions by specific immune cell populations, including (but not limited to) CD8⁺ cytotoxic T lymphocytes, Th1 and Th17 CD4⁺ T cells, natural killer cells, dendritic cells, and M1 macrophages constitutes an independent prognostic indicator in several types of cancer. Conversely, high levels of intratumoral CD4⁺CD25⁺FOXP3⁺ regulatory T cells, Th2 CD4⁺ T cells, myeloid-derived suppressor cells, M2 macrophages and neutrophils have frequently been associated with dismal prognosis. So far, only a few studies have addressed the true predictive potential of TILs in cancer patients, generally comforting the notion that—at least in some clinical settings—the immune infiltrate can reliably predict if a specific patient will respond to therapy or not. In this Trial Watch, we will summarize the results of clinical trials that have evaluated/are evaluating the prognostic and predictive value of the immune infiltrate in the context of solid malignancies.

TLRs as a Promise Target Along With Immune Checkpoint Against Gastric Cancer

Gastric cancer (GC) is one of the most common cancers in the world, and the incidence of gastric cancer in Asia appears to increase in recent years. Although there is a lot of improvement in treatment approaches, the prognosis of GC is poor. So it is urgent to search for a novel and more effective treatment to improve the survival rate of patients. Both innate immunity and adaptive immunity are important in cancer. In the innate immune system, pattern recognition receptors (PRRs) activate immune responses by recognizing pathogen-associated molecular patterns (PAMPs) and damage-associated molecular patterns (DAMPs). Toll-like receptors (TLRs) are a class of pattern recognition receptors (PRRs). Many studies have reported that TLRs are involved in the occurrence, development, and treatment of GC. Therefore, TLRs are potential targets for immunotherapy to gastric cancer. However, gastric cancer is a heterogeneous disorder, and TLRs function in GC is complex. TLRs agonists can be potentially used not only as therapeutic agents to treat gastric cancer but also as adjuvants in conjunction with other immunotherapies. They might provide a promising new target for GC treatment. In the review, we sort out the mechanism of TLRs involved in tumor immunity and summarize the current progress in TLRs-based therapeutic approaches and other immunotherapies in the treatment of GC.

Lipid Nanoparticle Acts as a Potential Adjuvant for Influenza Split Vaccine without Inducing Inflammatory Responses

Vaccination is a critical and reliable strategy for controlling the spread of influenza viruses in populations. Conventional seasonal split vaccines (SVs) for influenza evoke weaker immune responses than other types of vaccines, such as inactivated whole-virion vaccines, although SVs are highly safe compared to other types. Here, we assessed the potential of the lipid nanoparticle (LNP) we developed as an adjuvant for conventional influenza SV as an antigen in mice. The LNP did not induce the production of cytokines such as interleukin-6 (IL-6) and IL-12 p40 by dendritic cells or the expression of co-stimulatory molecules on these cells in vitro. In contrast, an SV adjuvanted with LNP improved SV-specific IgG1 and IgG2 responses and the Th1 response compared to the SV alone in mice. In addition, SV adjuvanted with an LNP gave superior protection against the influenza virus challenge over the SV alone and was as effective as SV adjuvanted with aluminum salts in mice. The LNP did not provoke inflammatory responses such as inflammatory cytokine production and inflammatory immune cell infiltration in mice, whereas aluminum salts induced inflammatory responses. These results suggest the potential of the LNP as an adjuvant without inflammatory responses for influenza SVs. Our strategy should be useful for developing influenza vaccines with enhanced efficacy and safety.

Trial watch: IDO inhibitors in cancer therapy

Indoleamine 2,3-dioxygenase 1 (IDO1) catalyzes the first, rate-limiting step of the so-called “kynurenine pathway”, which converts the essential amino acid L-tryptophan (Trp) into the immunosuppressive metabolite L-kynurenine (Kyn). While expressed constitutively by some tissues, IDO1 can also be induced in specific subsets of antigen-presenting cells that ultimately favor the establishment of immune tolerance to tumor antigens. At least in part, the immunomodulatory functions of IDO1 can be explained by depletion of Trp and accumulation of Kyn and its derivatives. In animal tumor models, genetic or pharmacological IDO1 inhibition can cause the (re)activation of anticancer immune responses. Similarly, neoplasms expressing high levels of IDO1 may elude anticancer immunosurveillance. Therefore, IDO1 inhibitors represent promising therapeutic candidates for cancer therapy, and some of them have already entered clinical evaluation. Here, we summarize preclinical and clinical studies testing IDO1-targeting interventions for oncologic indications.

Senescence and Cancer: Role of Nitric Oxide (NO) in SASP

Cellular senescence is a cell state involved in both physiological and pathological processes such as age-related diseases and cancer. While the mechanism of senescence is now well known, its role in tumorigenesis still remains very controversial. The positive and negative effects of senescence on tumorigenesis depend largely on the diversity of the senescent phenotypes and, more precisely, on the senescence-associated secretory phenotype (SASP). In this review, we discuss the modulatory effect of nitric oxide (NO) in SASP and the possible benefits of the use of NO donors or iNOS inducers in combination with senotherapy in cancer treatment.

A novel TLR7 agonist as adjuvant to stimulate high quality HBsAg-specific immune responses in an HBV mouse model

Background

The global burden of hepatitis B virus (HBV) infection in terms of morbidity and mortality is immense. Novel treatments that can induce a protective immune response are urgently needed to effectively control the HBV epidemic and eventually eradicate chronic HBV infection.

Methods

We designed and evaluated an HBV therapeutic vaccine consisting of a novel Toll-like receptor 7 (TLR7) agonist T7-EA, an Alum adjuvant and a recombinant HBsAg protein. We used RNA-seq, ELISA and hTLR7/8 reporting assays to characterize T7-EA in vitro and real-time PCR to evaluate the tissue-retention characteristics in vivo. To evaluate the adjuvant potential, we administrated T7-EA intraperitoneally in a formulation with an Alum adjuvant and HBsAg in normal and HBV mice, then, we evaluated the HBsAg-specific immune responses by ELISA and Elispot assays.

Results

T7-EA acted as an hTLR7-specific agonist and induced a similar gene expression pattern as an unmodified TLR7 ligand when Raw 264.7 cells were exposed to T7-EA; however, T7-EA was more potent than the unmodified TLR7 ligand. In vivo studies showed that T7-EA had tissue-retaining activity with stimulating local cytokine and chemokine expression for up to 7 days. T7-EA could induce Th1-type immune responses, as evidenced by an increased HBsAg-specific IgG2a titer and a T-cell response in normal mice compared to mice received traditional Alum-adjuvant HBV vaccine. Importantly, T7-EA could break immune tolerance and induce persistent HBsAg-specific antibody and T-cell responses in an HBV mouse model.

Conclusions

T7-EA might be a candidate adjuvant in a prophylactic and therapeutic HBV vaccine.

Toll-like Receptors from the Perspective of Cancer Treatment

Toll-like receptors (TLRs) represent a family of pattern recognition receptors that recognize certain pathogen-associated molecular patterns and damage-associated molecular patterns. TLRs are highly interesting to researchers including immunologists because of the involvement in various diseases including cancers, allergies, autoimmunity, infections, and inflammation. After ligand engagement, TLRs trigger multiple signaling pathways involving nuclear factor-κB (NF-κB), interferon-regulatory factors (IRFs), and mitogen-activated protein kinases (MAPKs) for the production of various cytokines that play an important role in diseases like cancer. TLR activation in immune as well as cancer cells may prevent the formation and growth of a tumor. Nonetheless, under certain conditions, either hyperactivation or hypoactivation of TLRs supports the survival and metastasis of a tumor. Therefore, the design of TLR-targeting agonists as well as antagonists is a promising immunotherapeutic approach to cancer. In this review, we mainly describe TLRs, their involvement in cancer, and their promising properties for anticancer drug discovery.

CCL22 Signaling in the Tumor Environment

T cell-mediated elimination of malignant cells is one cornerstone of endogenous and therapeutically induced antitumor immunity. Tumors exploit numerous regulatory mechanisms to suppress T cell immunity. Regulatory T cells (T regs) play a crucial role in this process due to their ability to inhibit antitumoral immune responses and they are known to accumulate in various cancer entities. The chemokine CCL22, predominately produced by dendritic cells (DCs), regulates T reg migration via binding to its receptor CCR4. CCL22 controls T cell immunity, both by recruiting T regs to the tumor tissue and by promoting the formation of DC-T reg contacts in the lymph node. Here, we review the current knowledge on the role of CCL22 in cancer immunity. After revising the principal mechanisms of CCL22-induced immune suppression, we address the factors leading to CCL22 expression and ways of targeting this chemokine therapeutically. Therapeutic interventions to the CCL22-CCR4 axis may represent a promising strategy in cancer immunotherapy.

Targeting Cellular and Tissue HIV Reservoirs With Toll-Like Receptor Agonists

The elimination of both cellular and tissue latent reservoirs is a challenge toward a successful HIV cure. "Shock and Kill" are among the therapeutic strategies that have been more extensively studied to target these reservoirs. These strategies are aimed toward the reactivation of the latent reservoir using a latency-reversal agent (LRA) with the subsequent killing of the reactivated cell either by the cytotoxic arm of the immune system, including NK and CD8 T cells, or by viral cytopathic mechanisms. Numerous LRAs are currently being investigated in vitro, ex vivo as well as in vivo for their ability to reactivate and reduce latent reservoirs. Among those, several toll-like receptor (TLR) agonists have been shown to reactivate latent HIV. In humans, there are 10 TLRs that recognize different pathogen-associated molecular patterns. TLRs are present in several cell types, including CD4 T cells, the cell compartment that harbors the majority of the latent reservoir. Besides their ability to reactivate latent HIV, TLR agonists also increase immune activation and promote an antiviral response. These combined properties make TLR agonists unique among the different LRAs characterized to date. Additionally, some of these agonists have shown promise toward finding an HIV cure in animal models. When in combination with broadly neutralizing antibodies, TLR-7 agonists have shown to impact the SIV latent reservoir and delay viral rebound. Moreover, there are FDA-approved TLR agonists that are currently being investigated for cancer therapy and other diseases. All these has prompted clinical trials using TLR agonists either alone or in combination toward HIV eradication approaches. In this review, we provide an extensive characterization of the state-of-the-art of the use of TLR agonists toward HIV eradication strategies and the mechanism behind how TLR agonists target both cellular and tissue HIV reservoirs.

Beneficial modulation of the tumor microenvironment and generation of anti-tumor responses by TLR9 agonist lefitolimod alone and in combination with checkpoint inhibitors

Activation of Toll-like receptor 9 (TLR9) is known to foster innate and adaptive immune responses and thus improve immune-mediated control of malignant disease. Lefitolimod is a potent TLR9 agonist without chemical modification developed for immunotherapeutic strategies. Modulation of the tumor microenvironment (TME) is a crucial requirement for the response to various immunotherapies: Immunogenic (“hot”) tumors, characterized by their T cell-infiltrated TME, respond better compared to non-immunogenic (“cold”) tumors. It has been speculated that the mode-of-action of lefitolimod provides the necessary signals for activation of immune cells, their differentiation into anti-tumor effector cells and their recruitment into the TME. We investigated the effect of lefitolimod on TME, and its potency to induce synergistic anti-tumor effects when combined with immune checkpoint inhibitory antibodies (CPI) in a murine model. Indeed, we could show that treatment with single-agent lefitolimod beneficially modulated the TME, via infiltration of activated CD8+ cells and a shift in the macrophage population toward M1 phenotype. The result was a pronounced anti-tumor effect correlated with the magnitude of infiltrated immune cells and tumor-specific T cell responses. In line with this, lefitolimod led to persistent anti-tumor memory in the EMT-6 model after tumor re-challenge. This was accompanied by an increase of tumor-specific T cell responses and cross-reactivity against different tumor cells. Lefitolimod clearly augmented the limited anti-tumor effect of the CPI anti-PD1 in an A20 and anti-PD-L1 in a CT26 model. These properties of potent immune surveillance reactivation render lefitolimod an ideal candidate as therapeutic agent for immuno-oncology, e.g. improving CPI strategies.

MEK1/2 Inhibitors Unlock the Constrained Interferon Response in Macrophages Through IRF1 Signaling

Macrophages are immune sentinels essential for pathogen recognition and immune defense. Nucleic acid-sensing toll-like receptors like TLR7 activate tailored proinflammatory and interferon responses in macrophages. Here we found that TLR7 activation constrained itself and other TLRs from inducing interferon response genes in macrophages through MAPK kinase 1/2 (MEK1/2)-dependent IRF1 inhibition. Downstream of the MEK1/2-ERK pathway, TLR7-activated macrophages induced interleukin-10 (IL-10), a signal transducer and activator of transcription 3 (STAT3) signaling axis, which constrained the expression of interferon response genes, immunomodulatory cytokines, and chemokines. Nevertheless, MEK1/2 inhibitors unlocked an IRF1-interferon signature response in an NF-κB-dependent manner. Deficiency in interferon regulatory factor 1 (Irf1) completely abrogated the interferon response and prevented the reprogramming of macrophages into an immunostimulatory phenotype. As a proof of concept, combination treatment with a TLR7 agonist and MEK1/2 inhibitor synergistically extended the survival of wild-type but not Irf1-deficient melanoma-bearing mice. In a retrospective study, higher expression of Irf1 and interferon response genes correlated with more favorable prognosis in patients with cutaneous melanoma. Our findings demonstrated how MEK1/2 inhibitor unlocks IRF1-mediated interferon signature response in macrophages, and the therapeutic potentials of combination therapy with MEK1/2 inhibitor and TLR7 agonist.

The Impact of Intratumoral and Gastrointestinal Microbiota on Systemic Cancer Therapy

The human microbiome is a complex aggregate of microorganisms, and their genomes exert a number of influences crucial to the metabolic, immunologic, hormonal, and homeostatic function of the host. Recent work, both in preclinical mouse models and human studies, has shed light on the impact of gut and tumor microbiota on responses to systemic anticancer therapeutics. In light of this, strategies to target the microbiome to improve therapeutic responses are underway, including efforts to target gut and intratumoral microbes. Here, we discuss mechanisms by which microbiota may impact systemic and antitumor immunity, in addition to outstanding questions in the field. A deeper understanding of these is critical as we devise putative strategies to target the microbiome.

The immunostimulatory effects and pro-apoptotic activity of rhCNB against Lewis lung cancer is mediated by Toll-like receptor 4

Background

Recombinant human calcineurin B subunit (rhCNB) has been shown to be an immune‐stimulatory protein promoting cytokine production and inducing phenotypic maturation of Dendritic cells (DCs). In vivo, it has good antitumor efficacy, and has potential as an antitumor drug. Exogenous rhCNB was found to be internalized into tumor cells via the Toll‐like receptor 4 (TLR4) complex, but it was not known whether its immuno‐modulatory and antitumor functions involved entry by this same route.

Methods

The production and secretion of the cytokines and chemokines in innate immune cells induced by rhCNB were determined by ELISA, and the expression of CD40, CD80, CD86, and MHCII was analyzed by FACs. Experimental Lewis lung cancer (LLC) model was prepared in C57 BL/6 wild‐type (WT) mice, TLR4^−/− mice or their littermates by the inoculation of LLCs in their right armpit, and then administrated daily intraperitoneal injections (0.2 mL) of normal saline, rhCNB 20 mg/kg, and rhCNB 40 mg/kg, respectively.

Results

Recombinant human calcineurin B subunit promoted the production of antitumor cytokines by innate immune cells, and culture supernatants of rhCNB‐stimulated immune cells induced apoptosis of LLCs. In addition, rhCNB up‐regulated CD40, CD80, CD86, and MHCII expression in macrophages and DCs in TLR4⁺ cells but failed to do so in TLR4 deficient cells. rhCNB also induced the formation of CD4⁺ and CD8⁺T cells in splenocytes from WT mice, but not from TLR4‐deficient littermates. Intraperitoneal administration of WT C57BL/6 mice with rhCNB resulted in a 50% reduction in LLC tumor growth, but failed to inhibit tumor growth in TLR4^−/− littermates.

Conclusions

The in vivo antitumor and immunomodulatory effects of rhCNB are mediated by the TLR4. This conclusion is important for the further understanding and development of rhCNB as an antitumor drug.

Type I interferons and dendritic cells in cancer immunotherapy

Type I interferons (IFNs) facilitate cancer immunosurveillance, antitumor immunity and antitumor efficacy of conventional cell death-inducing therapies (chemotherapy/radiotherapy) as well as immunotherapy. Moreover, it is clear that dendritic cells (DCs) play a significant role in aiding type I IFN-driven immunity. Owing to these antitumor properties several immunotherapies involving, or inducing, type I IFNs have received considerable clinical attention, e.g., recombinant IFNα2 or agonists targeting pattern recognition receptor (PRR) pathways like Toll-like receptors (TLRs), cGAS-STING or RIG-I/MDA5/MAVS. A series of preclinical and clinical evidence concurs that the success of anticancer therapy hinges on responsiveness of both cancer cells and DCs to type I IFNs. In this article, we discuss this link between type I IFNs and DCs in the context of cancer biology, with particular attention to mechanisms behind type I IFN production, their impact on DC driven anticancer immunity, and the implications of this for cancer immunotherapy, including DC-based vaccines.

Potential Roles of Innate Immune Chemokine and Cytokine Network on Lipopolysaccharide-Based Therapeutic Approach in Ovarian Cancer

Ovarian cancer (OC), the deadliest gynecological cancer, results in poor overall survival, urgently requiring a novel therapeutic approach. As cumulative exposures to endotoxins decreased OC risk epidemiologically, we evaluated if LPS, a Toll-like receptor 4 agonist known as active component of endotoxins, could increase survival in the murine peritoneal dissemination model of SKOV-3 OC cells. LPS significantly increased the mean survival time of more than 116 days compared with 63 days in the control. Furthermore, no tumor burden was present in three mice among eight LPS-treated mice. SKOV-3 cells were not responsive to LPS and showed unaltered chemokine signature. Rather than direct effects to OC cells, LPS was found to increase proinflammatory chemokines and cytokines, such as CXCL1, CXCL8, TNF, and IL-1B, in innate immune system. Taken together, LPS is likely to potentiate the cytotoxic-related innate immunogenicity via proinflammatory chemokines and cytokines, which attenuates the peritoneal dissemination of OC.

Devil Facial Tumours: Towards a Vaccine

The Tasmanian devil is the only mammalian species to harbour two independent lineages of contagious cancer. Devil facial tumour 1 (DFT1) emerged in the 1990s and has caused significant population declines. Devil facial tumour 2 (DFT2) was identified in 2014, and evidence indicates that this new tumour has emerged independently of DFT1. While DFT1 is widespread across Tasmania, DFT2 is currently found only on the Channel Peninsula in south east Tasmania. Allograft transmission of cancer cells should be prevented by major histocompatibility complex (MHC) molecules. DFT1 avoids immune detection by downregulating MHC class I expression, which can be reversed by treatment with interferon-gamma (IFNγ), while DFT2 currently circulates in hosts with a similar MHC class I genotype to the tumour. Wild Tasmanian devil numbers have not recovered from the emergence of DFT1, and it is feared that widespread transmission of DFT2 will be devastating to the remaining wild population. A preventative solution for the management of the disease is needed. Here, we review the current research on immune responses to devil facial tumours and vaccine strategies against DFT1 and outline our plans moving forward to develop a specific, effective vaccine to support the wild Tasmanian devil population against the threat of these two transmissible tumours.

Toll-Like Receptor 4 as an Immune Receptor Against Mycobacterium tuberculosis: A Systematic Review

OBJECTIVE

To review the main Mycobacterium tuberculosis (Mtb) pathogen-associated molecular patterns (PAMPs) and the roles played by toll-like receptor (TLR)4 in determination of Mtb infection outcome.

METHODS

Several scientific databases, including Scopus, PubMed, and Google Scholar, were used for searching appropriate research articles from the literature for information on our topic.

RESULTS

TLR4 plays positive roles in induction of immune responses against Mtb and participates in eradication of the infection. Some limited investigations approved the roles of TLR4 in induction of apoptosis in macrophages during tuberculosis (TB) and attenuation of immune responses in some situations.

CONCLUSIONS

TB outcome appears to be dependent on TLR4/Mtb interaction and several factors, including bacterial load and immune or nonimmune cells, as hosts. Also, other TLR/Mtb interactions can affect TLR4 responses.

Innate sensors that regulate vaccine responses

Pattern recognition receptors (PRRs) control elemental functions of antigen presenting cells (APCs) and critically shape adaptive immune responses. Wielding a natural adjuvanticity, live attenuated vaccines elicit exceptionally efficient and durable immunity. Commonly used vaccine adjuvants target individual PRRs or bolster the immunogenicity of vaccines via indirect mechanisms of inflammation. Here, we review the impact of innate sensors on immune responses to live attenuated vaccines and commonly used vaccine adjuvants, with a focus on human vaccine responses. We discuss the unique potential of microbial nucleic acids and their corresponding sensing receptors to mimic live attenuated vaccines and promote protective immunity.

Therapeutic potential of toll-like receptors in treatment of gynecological cancers

Toll-like receptors (TLRs) play an important role in the innate and adaptive immune system. They are expressed in various regions of the female reproductive tract, and their regulation may be involved in the pathogenesis of gynecological lesions. There is growing evidence that ligands for several TLRs are potentially anticancer agents, some of which have already been approved by the FDA, and these compounds are now undergoing clinical evaluation. There is a rationale for using these ligands as adjuvants in the treatment or prevention of gynecological cancer. Some TLR agonists that are of potential interest in the treatment of gynecological lesions include imiquimod, motolimod, cervarix, and CpG-oligodeoxynucleotides (ODNs). In this review, we outline the different functions of TLRs in gynecological cancer with particular emphasis on the value of TLR agonists as a potential therapeutic target in the treatment of gynecological cancer. © 2019 IUBMB Life, 71(5):549-564, 2019.

EnanDIM - a novel family of L-nucleotide-protected TLR9 agonists for cancer immunotherapy

Background

Toll-like receptor 9 agonists are potent activators of the immune system. Their clinical potential in immunotherapy against metastatic cancers is being evaluated across a number of clinical trials. TLR9 agonists are DNA-based molecules that contain several non-methylated CG-motifs for TLR9 recognition. Chemical modifications of DNA backbones are usually employed to prevent degradation by nucleases. These, however, can promote undesirable off-target effects and therapeutic restrictions.

Methods

Within the EnanDIM® family members of TLR9 agonists described here, D-deoxyribose nucleotides at the nuclease-accessible 3′-ends are replaced by nuclease-resistant L-deoxyribose nucleotides. EnanDIM® molecules with varying sequences were screened for their activation of human peripheral blood mononuclear cells based on secretion of IFN-alpha and IP-10 as well as activation of immune cells. Selected molecules were evaluated in mice in a maximum feasible dose study and for analysis of immune activation. The ability to modulate the tumor-microenvironment and anti-tumor responses after EnanDIM® administration was analyzed in syngeneic murine tumor models.

Results

The presence of L-deoxyribose containing nucleotides at their 3′-ends is sufficient to prevent EnanDIM® molecules from nucleolytic degradation. EnanDIM® molecules show broad immune activation targeting specific components of both the innate and adaptive immune systems. Activation was strictly dependent on the presence of CG-motifs, known to be recognized by TLR9. The absence of off-target effects may enable a wide therapeutic window. This advantageous anti-tumoral immune profile also promotes increased T cell infiltration into CT26 colon carcinoma tumors, which translates into reduced tumor growth. EnanDIM® molecules also drove regression of multiple other murine syngeneic tumors including MC38 colon carcinoma, B16 melanoma, A20 lymphoma, and EMT-6 breast cancer. In A20 and EMT-6, EnanDIM® immunotherapy cured a majority of mice and established persistent anti-tumor immune memory as evidenced by the complete immunity of these mice to subsequent tumor re-challenge.

Conclusions

In summary, EnanDIM® comprise a novel family of TLR9 agonists that facilitate an efficacious activation of both innate and adaptive immunity. Their proven potential in onco-immunotherapy, as shown by cytotoxic activity, beneficial modulation of the tumor microenvironment, inhibition of tumor growth, and induction of long-lasting, tumor-specific memory, supports EnanDIM® molecules for further preclinical and clinical development.

Electronic supplementary material

The online version of this article (10.1186/s40425-018-0470-3) contains supplementary material, which is available to authorized users.

Activation of viral defense signaling in cancer

A coordinated action of innate and adaptive immune responses is required to efficiently combat a microbial infection. It has now become clear that cancer therapies also largely benefit when both arms of the immune response are engaged. In this review, we will briefly describe the current knowledge of innate immunity and how this can be utilized to prime tumors for a better response to immune checkpoint inhibitors. Comments on compounds in development and ongoing clinical trials will be provided.

Imiquimod enhances the potency of an exogenous BM-DC based vaccine against mouse melanoma

Dendritic cell (DC) vaccine is a potent immunotherapeutic approach for cancer treatment, but the clinical efficacy needs to be improved. In this study, we evaluated the combinational effect of Toll-like receptor 7 (TLR7) agonist Imiquimod and BM-DC vaccine against mouse melanoma and explored the potential mechanisms. We found that topical application of Imiquimod cream caused skin inflammation and enhanced exogenous BM-DC homing to draining lymph nodes. Imiquimod treatment enhanced DC vaccine efficacy against B16-OVA melanoma. The combinational modality enhanced cytotoxicity of splenic lymphocyte to tumor cells and inhibited CD4⁺FOXP3⁺Treg cell production. TLR7 mRNA expression was confirmed in both MC/9 mast cells and DCs. MC/9 cells treated by R837 (soluble form of Imiquimod) enhanced CD80, CD86, MHC-II and CCR7 expression on DCs. R837 inhibited B16-OVA cell growth in vitro. Our findings suggest that Imiquimod can be used as a potent adjuvant in the formulation of a DC-based tumor fighting vaccine. The mechanisms underlying these effects of Imiquimod are related with enhanced DC homing to DLNs, inhibition of Treg's production, direct tumor cell toxicity and synergistic function with mast cell in enhancing DC activation.

The Role of Toll-Like Receptor in Inflammation and Tumor Immunity

Toll-like receptors (TLRs) activation enables host to recognize a large number of pathogen-associated molecule patterns (PAMPs), ignite immune cells to discriminate between self and non-self, and then promote the following innate and adaptive immune responses. Accumulated clinical/preclinical evidences have proven TLRs to be critical role in the autoimmune diseases, including inflammatory and tumor-associated diseases. Activation of TLRs is becoming or has been a target for cancer treatment. It is shown that TLRs can induce preferable anti-tumor effect by eliciting inflammatory cytokines expression and cytotoxic T lymphocytes (CTLs) response. As adjuvant, TLRs agonists can launch a strong immune response to assist cancer radiotherapy and bio-chemotherapy. On the other hand, tumor-associated antigens acting as PAMPs, can also activate TLRs and induce tumor gene-related programmed cell death, including apoptosis, autophagy and programmed necrosis. While there are also arguments that the excessive TLRs expression will promote tumor deterioration in various organisms, as the TLR-induced inflammation will accelerate the cancer cells boost in the tumor microenvironment (TME). However, the effect of TLRs acting on cancers is still not quite clear today. In this review, we will summarize the recent researches of TLRs in cancer treatment and their role in TME, giving a brief overview on future expectation.