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

HSV-1 as a gene delivery platform for cancer gene therapy

Herpes simplex virus type 1 (HSV-1) is a DNA virus with strong replication capabilities, a large genomic payload (≥30 kb), and low toxicity, making it a prominent vector in cancer gene therapy. Clinically approved oncolytic HSV-1 (oHSV-1) variants, such as T-VEC and G47Δ, demonstrate safety and efficacy in localized tumors, but face challenges in treating metastatic disease. To address this issue, next-generation oHSV-1 designs focus on precision targeting and immune remodeling through the delivery of multiple exogenous genes. In this review, we provide an overview of the inherent characteristics of oHSV-1 as a gene delivery platform, focusing on its genetic modification strategies, safety challenges in clinical applications, and future directions to maximize its therapeutic potential.

Paclitaxel resistance in breast cancer: Current challenges and recent advanced therapeutic strategies

Breast cancer (BC) is one of the leading causes of cancer-related deaths among women worldwide. Paclitaxel (PTX), a chemotherapeutic agent derived from the taxane family, is commonly used in treating BC due to its ability to disrupt microtubule dynamics and induce cell death. However, resistance to PTX presents a significant challenge, as it diminishes the drug's effectiveness and can lead to treatment failure. This review explores the mechanisms by which PTX exerts its effects and the various factors contributing to resistance. These factors include genetic mutations that affect tubulin dynamics, the role of non-coding RNAs, molecular pathways involved in chemoresistance, epigenetic changes, post-transcriptional modifications, increased activity of ABC transporters that promote drug efflux, immunosuppressive interactions within the tumor microenvironment, and resistance mediated by autophagy. This review also explores strategies to overcome PTX resistance, including molecular and genetic innovations, combination therapies, and nanotechnology-based approaches. These strategies may improve PTX efficacy and enhance treatment outcomes for BC patients.

Role of TLRs as signaling cascades to combat infectious diseases: a review

Investigating innate immunity and its signaling transduction is essential to understand inflammation and host defence mechanisms. Toll-like receptors (TLRs), an evolutionarily ancient group of pattern recognition receptors, are crucial for detecting microbial components and initiating immune responses. This review summarizes the mechanisms and outcomes of TLR-mediated signaling, focusing on motifs shared with other immunological pathways, which enhances our understanding of the innate immune system. TLRs recognize molecular patterns in microbial invaders, activate innate immunity and promote antigen-specific adaptive immunity, and each of them triggers unique downstream signaling patterns. Recent advances have highlighted the importance of supramolecular organizing centers (SMOCs) in TLR signaling, ensuring precise cellular responses and pathogen detection. Furthermore, this review illuminates how TLR pathways coordinate metabolism and gene regulation, contributing to adaptive immunity and providing novel insights for next-generation therapeutic strategies. Ongoing studies hold promise for novel treatments against infectious diseases, autoimmune conditions, and cancers.

The Recruitment and Immune Suppression Mechanisms of Myeloid-Derived Suppressor Cells and Their Impact on Bone Metastatic Cancer

BACKGROUND

MDSCs are immature neutrophils and monocytes with immunosuppressive potentials, involving mononuclear MDSCs (M-MDSCs) and polymorphonuclear MDSCs (PMN-MDSCs).

RECENT FINDINGS

They are significant components of the tumor microenvironment (TME). Besides, recent studies also verified that MDSCs also facilitated the progression of bone metastasis by regulating the network of cytokines and the function of immune cells.

CONCLUSION

It is necessary to summarize the mechanisms of MDSC recruitment and immunosuppression, and their impact on bone metastasis.

Normalization of tumor vasculature by imiquimod: proposal for a new anticancer therapeutic indication for a TLR7 agonist

Imiquimod (IMQ), a drug from aminoquinoline group, is the toll-like receptor 7 (TLR7) agonist. It acts as an immunostimulant and radio-sensitizing agent. IMQ stimulates both innate and adaptive immune response. Despite studies conducted, there are no unambiguous data showing how IMQ affects the condition of tumor blood vessels. Tumor vasculature plays the main role in tumor progression. Formation of abnormal blood vessels increases area of hypoxia which recruits suppressor cells, blocks tumor infiltration by CD8+ T lymphocytes, inhibits efficacy of chemoterapeutic drug and leads to cancer relapse. Normalization is a type of therapy targeted at abnormal tumor blood vessels. Here, we demonstrated that 50 µg of IMQ inhibits the growth of melanoma tumors more efficiently, compared to other tested doses and the control group. Dose escalation did not improve the therapeutic antitumor potential of TLR7 agonist. A dose of 50 µg of IMQ most effectively reduced tumor blood vessel density. Imiquimod normalized tumor vasculature both structurally (by reducing vessel tortuosity and increasing pericyte coverage) and functionally (by improving tumor perfusion) in a dose-dependent manner. Hypoxia regions in tumors of treated mice were significantly reduced after IMQ administration. A dose of 50 µg of IMQ had also the greatest impact on the changes in tumor-infiltrating T lymphocytes levels. TLR7 agonist inhibited angiogenesis in treated mice. Functional vascular normalization by IMQ increases the effectiveness of low dose of doxorubicin. Higher dose of IMQ showed worse effects than lower doses including decreased tumor perfusion, increased tumor hypoxia and immunosuppression. This knowledge may help to optimize the combination of the selected IMQ dose with e.g. chemotherapy or radiotherapy to elicit synergistic effect in cancer treatment. To conclude, we outline IMQ repurposing as a vascular normalizing agent. Our research results may contribute to expanding the therapeutic indications for the use of IMQ in anticancer therapy in the future.

The mechanism of baicalin in improving pulmonary inflammatory response and injury and regulating intestinal flora in Mycoplasma pneumoniae pneumonia mice

OBJECTIVE

Mycoplasma pneumoniae (MP) is a common pathogen that can cause respiratory infections. We explored the mechanisms of baicalin (BIA) affecting pulmonary inflammation and injury and regulated their intestinal flora through the TLR4/NF-κB pathway in MP pneumonia (MPP) mice with intestinal dysbiosis.

METHODS

The intestinal dysbiosis and the MPP mouse models with intestinal dysbiosis were established and treated with different doses of BIA, with lung wet-to-dry weight (W/D) ratio weighed. Kits were conducted to detect MP expression and serum C-reactive protein (CRP)/INF-γ/TNF-α/IL-1β/IL-8 levels, and RT-qPCR and Western blot to determine TLR4/MyD88/NF-κBp65 levels. Lung injury was assessed using HE staining, and intestinal flora structure using 16S rDNA sequencing. Gas chromatography-mass spectrometry determined fecal short-chain fatty acid (SFCA) content.

RESULTS

The broad-spectrum antibiotic mixture caused enlarged cecum, increased contents, darker color, weight loss, decreased intestinal flora abundance and diversity, and intestinal flora structure imbalance in mice. The MP-infected intestinal dysbiosis mice exhibited elevated MP expression, reduced body weight, increased W/D ratio, elevated serum CRP/INF-γ/TNFα/IL-1β/IL-8 levels, as well as interstitial pneumonitis in lungs. TLR4/MyD88/NF-κB p65 were elevated in lung tissues of MPP mice with intestinal dysbiosis. BIA partially reversed pulmonary inflammation and injury, and restored the flora diversity and SCFAs in MPP mice with intestinal dysbiosis.

CONCLUSION

BIA attenuated pulmonary inflammation and injury and modulated their intestinal flora imbalance by inhibiting the TLR4/NF-κB pathway in MPP mice with intestinal dysbiosis.

Examination of the potential clinical application of 5DEX-0509R, the tumor macrophage-targeting nanomedicine

Toll-like receptors (TLRs) are crucial for the detection of infections and activation of downstream signaling pathways that lead to the production of pro-inflammatory cytokines and interferons. Because of their strong immunostimulatory activity, TLRs are thought to be a "double-edged sword" for systemic treatment, even in the cancer field. To solve this, we have developed dextran-based TAM targeting activator conjugate (D-TAC) technology which successfully uses tumor-associated macrophages (TAMs) to deliver the TLR7 agonist DSP-0509. We have demonstrated that the anti-tumor effect of our best drug candidate 5DEX-0509R is dependent on the abundance of TAMs, which is consistent with their mechanism of action. In this study, we compared the anti-tumor effects of EIK1001 and 5DEX-0509R, and analyzed its unique immune reaction against tumors to evaluate whether 5DEX-0509R is suitable for further clinical study. 5DEX-0509R showed superior anti-tumor activity compared to EIK1001, an R848 sulfate currently in phase 2 trials, with comparable systemic cytokine profiles. 5DEX-0509R elicited unique CD4 T cell and B cell-dependent anti-tumor effects. We also found that 5DEX-0509R synergistically suppresses tumors with oxaliplatin by changing M2 macrophages that cause oxaliplatin to become resistant to antitumor M1 macrophages. In addition, 5DEX-0509R caused a rapid but not sustained cytokine elevation in both rats and dogs. We believe 5DEX-0509R is worth pursuing for clinical trials.

Toll-like receptor agonists as cancer vaccine adjuvants

Cancer immunotherapy has emerged as a promising strategy to treat cancer patients. Among the wide range of immunological approaches, cancer vaccines have been investigated to activate and expand tumor-reactive T cells. However, most cancer vaccines have not shown significant clinical benefit as monotherapies. This is likely due to the antigen targets of vaccines, "self" proteins to which there is tolerance, as well as to the immunosuppressive tumor microenvironment. To help circumvent immune tolerance and generate effective immune responses, adjuvants for cancer vaccines are necessary. One representative adjuvant family is Toll-Like receptor (TLR) agonists, synthetic molecules that stimulate TLRs. TLRs are the largest family of pattern recognition receptors (PRRs) that serve as the sensors of pathogens or cellular damage. They recognize conserved foreign molecules from pathogens or internal molecules from cellular damage and propel innate immune responses. When used with vaccines, activation of TLRs signals an innate damage response that can facilitate the development of a strong adaptive immune response against the target antigen. The ability of TLR agonists to modulate innate immune responses has positioned them to serve as adjuvants for vaccines targeting infectious diseases and cancers. This review provides a summary of various TLRs, including their expression patterns, their functions in the immune system, as well as their ligands and synthetic molecules developed as TLR agonists. In addition, it presents a comprehensive overview of recent strategies employing different TLR agonists as adjuvants in cancer vaccine development, both in pre-clinical models and ongoing clinical trials.

Peptidoglycan induces CXCL10 production and inhibits esophageal squamous cell carcinoma proliferation

Poor oral health is an independent risk factor for upper-aerodigestive tract cancers, including esophageal squamous cell carcinoma (ESCC); thus, good oral health may reduce the risk of ESCC. We previously reported that high expression of Toll-like receptor (TLR) 6, which recognizes peptidoglycan (PGN) from Gram-positive bacteria correlates with a good prognosis after esophagectomy for ESCC. Most beneficial bacteria in the mouth are Gram-positive. We therefore hypothesized that PGN affects cancer cell proliferation and disease progression in ESCC. To test that idea, we assessed the expression of cytokine and chemokine mRNA and protein in eight ESCC cell lines. We also employed a mouse xenograft model to investigate the effect of PGN on ESCC tumor progression in vivo. We then investigated the relationship between the combined expression profiles of TLR6 and C-X-C motif chemokine ligand 10 (CXCL10) in clinical samples and 5-year overall survival (OS) and disease-specific survival (DSS) in ESCC patients after curative esophagectomy. We found that PGN significantly inhibited cell proliferation in six of eight ESCC lines and upregulated CXCL10 production via NF-κB2. In vivo, subcutaneous PGN administration tended to decrease ESCC tumor volume in mice. Combined high expression of TLR6 and CXCL10 correlated with a better prognosis in ESCC patients. This suggests that PGN reduces cell proliferation and tumor progression through a PGN-TLR-CXCL10 cascade, thereby influencing prognosis after esophagectomy for ESCC, and that improving the oral environment could potentially improve the prognosis of ESCC patients after esophagectomy.

Pirarubicin combined with TLR3 or TLR4 agonists enhances anti-tumor efficiency

BACKGROUND

Triple-negative breast cancer (TNBC) is prone to relapse due to the lack of effective therapeutic targets. Macrophages are the most abundant immune cells in the tumor microenvironment (TME) of breast cancer. Targeting the cross-talk between macrophages and cancer cells provides a more efficient strategy for anti-tumor therapy. Toll-like receptors (TLRs) are important players involved in macrophage activation, and TLR agonists are known to play roles in cancer therapy. However, the combination strategy of TLR agonists with chemotherapy drugs is still not well characterized.

METHODS

RT-PCR and Western blot were used to detect the expression of TLRs. The communication between breast cancer cells and macrophages were determined by co-culture in vitro. Tumor cells proliferation and migration were investigated by MTT assay and scratch wound assay. The effects of drug combinations and toxic side effects were assessed by immunohistochemistry and Hematoxylin & Eosin staining.

RESULTS

Expression of TLR3 and TLR4 were lower in breast tumor tissues compared with adjacent normal tissues. Patients with higher TLR3 or TLR4 expression levels had a better prognosis than those with lower expression levels. TLR3/4 expression was significantly inhibited when breast cancer cells MDA-MB-231 and E0771 were conditioned-cultured with macrophages in vitro and was also inhibited by pirarubicin (THP). However, the combination of TLR agonists and THP could reverse this response and inhibit the proliferation and migration of breast cancer cells. Additionally, this combination significantly reduced the tumor volume and weight in the murine model, increased the expression of TLR3/4 in mouse breast tumors.

CONCLUSIONS

Our results provide new ideas for the combination strategy of THP with TLR agonists which improves prognosis of breast cancer.

Nanomaterial-assisted delivery of CpG oligodeoxynucleotides for boosting cancer immunotherapy

Cancer immunotherapy aims to improve immunity to not only eliminate the primary tumor but also inhibit metastasis and recurrence. It is considered an extremely promising therapeutic approach that breaks free from the traditional paradigm of oncological treatment. As the medical community learns more about the immune system's mechanisms that "turn off the brake" and "step on the throttle", there is increasingly successful research on immunomodulators. However, there are still more restrictions than countermeasures with immunotherapy related to immunomodulators, such as low responsiveness and immune-related adverse events that cause multiple adverse reactions. Therefore, medical experts and materials scientists attempted to the efficacy of immunomodulatory treatments through various methods, especially nanomaterial-assisted strategies. CpG oligodeoxynucleotides (CpG) not only act as an adjuvant to promote immune responses, but also induce autophagy. In this review, the enhancement of immunotherapy using nanomaterial-based CpG formulations is systematically elaborated, with a focus on the delivery, protection, synergistic promotion of CpG efficacy by nanomaterials, and selection of the timing of treatment. In addition, we also discuss and prospect the existing problems and future directions of research on nanomaterials in auxiliary CpG therapy.

Invention and characterization of a systemically administered, attenuated and killed bacteria-based multiple immune receptor agonist for anti-tumor immunotherapy

Activation of immune receptors, such as Toll-like (TLR), NOD-like (NLR) and Stimulator of Interferon Genes (STING) is critical for efficient innate and adaptive immunity. Gram-negative bacteria (G-NB) contain multiple TLR, NOD and STING agonists. Potential utility of G-NB for cancer immunotherapy is supported by observations of tumor regression in the setting of infection and Coley's Toxins. Coley reported that intravenous (i.v.) administration was likely most effective but produced uncontrollable toxicity. The discovery of TLRs and their agonists, particularly the potent TLR4 agonist lipopolysaccharide (LPS)-endotoxin, comprising ~75% of the outer membrane of G-NB, suggests that LPS may be both a critical active ingredient and responsible for dose-limiting i.v. toxicity of G-NB. This communication reports the production of killed, stabilized, intact bacteria products from non-pathogenic G-NB with ~96% reduction of LPS-endotoxin activity. One resulting product candidate, Decoy10, was resistant to standard methods of cell disruption and contained TLR2,4,8,9, NOD2 and STING agonist activity. Decoy10 also exhibited reduced i.v. toxicity in mice and rabbits, and a largely uncompromised ability to induce cytokine and chemokine secretion by human immune cells in vitro, all relative to unprocessed, parental bacterial cells. Decoy10 and a closely related product, Decoy20, produced single agent anti-tumor activity or combination-mediated durable regression of established subcutaneous, metastatic or orthotopic colorectal, hepatocellular (HCC), pancreatic, and non-Hodgkin's lymphoma (NHL) tumors in mice, with induction of both innate and adaptive immunological memory (syngeneic and human tumor xenograft models). Decoy bacteria combination-mediated regressions were observed with a low-dose, oral non-steroidal anti-inflammatory drug (NSAID), anti-PD-1 checkpoint therapy, low-dose cyclophosphamide (LDC), and/or a targeted antibody (rituximab). Efficient tumor eradication was associated with plasma expression of 15-23 cytokines and chemokines, broad induction of cytokine, chemokine, innate and adaptive immune pathway genes in tumors, cold to hot tumor inflammation signature transition, and required NK, CD4+ and CD8+ T cells, collectively demonstrating a role for both innate and adaptive immune activation in the anti-tumor immune response.

Participation of TLRs in cancer immunopathogenesis and drug resistance via interacting with immunological and/or non-immunological signaling pathways as well as lncRNAs

Toll-like receptors (TLRs) have a convoluted role in cancer even though they are crucial to the immune system. By bridging the innate immune system and cancer, TLRs have a very complex impact on the formation of tumors and the effectiveness of anti-cancer treatments. TLR signaling links the innate and adaptive immune systems and initiates direct pathogen eradication. In cancer immunopathogenesis and treatment resistance, long non-coding RNAs (lncRNAs) modify TLR signaling linkages with immunological and non-immunological pathways. We identified lncRNAs that positively and negatively control TLR signaling, impacting immunological response and drug sensitivity. These results highlight the complex interactions between long non-coding RNAs and TLRs that influence the start of cancer and its response to treatment. Targeting specific lncRNAs is a practical way to control TLR signaling and perhaps enhance anti-tumor immunity while overcoming medication resistance. We provide a framework for developing novel immunotherapeutic regimens and customized medicine approaches for cancer treatment. The exact mechanisms by which lncRNAs regulate TLR signaling pathways should be defined by further research, and these findings should be validated in clinical situations. This finding makes future research of lncRNA-based drugs in combination with existing cancer treatments feasible.

Immunomodulatory Effects of a Prebiotic Formula with 2'-Fucosyllactose and Galacto- and Fructo-Oligosaccharides on Cyclophosphamide (CTX)-Induced Immunosuppressed BALB/c Mice via the Gut-Immune Axis

Obejectives: This study explored the immunomodulatory effects of a prebiotic formula consisting of 2'-fucosyllactose (2'-FL), galacto-oligosaccharides (GOSs), and fructo-oligosaccharides (FOSs) (hereinafter referred to as 2FGF) in cyclophosphamide (CTX)-induced immunosuppressed BALB/c mice and its underlying mechanisms. Methods: Sixty healthy female BALB/c mice were randomly divided into the following groups: normal control (NC) group; CTX treatment (CTX) group; 2FGF low-dose (2FGF-L) group; 2FGF medium-dose (2FGF-M) group; and 2FGF high-dose (2FGF-H) group. An immunosuppressed model was established in the 2FGF-H group by intraperitoneal injection of 80 mg/kg CTX. After 30 days of 2FGF intervention, peripheral blood, spleen tissue, thymus tissue, and intestinal tissue from the mice were collected and analyzed. The changes in weight and food intake of the mice were recorded weekly. Hematoxylin-eosin (HE) staining was used to observe the histological change of the spleen tissue. Enzyme-linked immunosorbent assay (ELISA) was employed to detect cytokine levels in peripheral blood. Flow cytometry was used to analyze T lymphocyte subgroup ratio of splenic lymphocytes. Western blot analysis was conducted on intestinal tissues to assess the expression of proteins involved in the tight junction, toll-like receptor 4 (TLR4), mitogen-activated protein kinase (MAPK), and nuclear factor kappa-light-chain-enhancer of activated B cell (NF-κB) signaling pathways. Additionally, molecular techniques were used to analyze the intestinal microbiota. Results: The results showed that 2FGF restored CTX-induced splenic injury, increased the number of splenic T lymphocytes, and elevated serum cytokines such as interleukin-4 (IL-4) and IL-10. In the intestine, 2FGF upregulated the expression of intestinal epithelial tight junction proteins such as Claudin-1 and zonula occludens 1 (ZO-1), thereby enhancing intestinal barrier function and activating the MAPK and NF-κB pathways via TLR4. Furthermore, 2FGF elevated the α-diversity (Shannon and Simpson indices) of the gut microbiota in CTX-induced immunosuppressed mice, enriching bacteria species positively correlated with anti-inflammatory cytokines (e.g., IL-4) such as g_Streptomyces and g_Bacillus and negatively correlated with pro-inflammatory cytokines (e.g., IL-1β) such as g_Saccharomyces. The results suggest that 2FGF may enhance immunity via the gut-immune axis. Conclusions: The 2FGF prebiotic formula showed an immunomodulatory effect in CTX-induced immunosuppressed mice, and the mechanism of which might involve optimizing the gut flora, enhancing intestinal homeostasis, strengthening the intestinal barrier, and promoting the expression of immune factors by regulating the TLR-4/MAPK/NF-κB pathway.

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.

Therapeutic liposomal combination to enhance chemotherapy response and immune activation of tumor microenvironment

Multiple oxaliplatin-resistance mechanisms have been proposed such as increase of anti-inflammatory M2 macrophages and lack of cytotoxic T-cells. Thereby oxaliplatin chemotherapy promotes an immunosuppressive tumor microenvironment and inhibits anti-tumor efficacy. It has been shown that toll-like receptor (TLR) agonists are capable of triggering broad inflammatory responses, which may potentially reduce oxaliplatin-resistance and improve the efficacy of chemotherapy. In this study, we established colorectal tumor-bearing zebrafish and mice, and investigated the effects of TLR agonists and oxaliplatin in macrophage function and anti-tumor T cell immunity as well as tumor growth control in vivo. To increase the potential of this strategy as well minimize side effects, neutral liposomes carrying oxaliplatin and cationic liposomes co-loaded with TLR agonists Poly I:C and R848 were employed for maximum immune activation. Both of two liposomal systems exhibited good physicochemical properties and excellent biological activities in vitro. The combination strategy delivered by liposomes showed more pronounced tumor regression and correlated with decreased M2 macrophage numbers in both zebrafish and mice. Increasing numbers of dendritic cells, DC maturation and T cell infiltration mediated via immunogenic cell death were observed in treated mice. Our study offers valuable insights into the potential of liposomal combination therapy to improve cancer treatment by reprogramming the tumor microenvironment and enhancing immune responses.

Targeting Tumor-Associated Macrophages with the Immune-Activating Nanomedicine for Achieving Strong Antitumor Activity with Rapid Clearance from the Body

Toll-like receptors (TLRs) are a class of pattern recognition receptors (PRRs) crucial for the detection of infections and activation of downstream signaling pathways that lead to the production of pro-inflammatory cytokines and interferons. The TLR pathway is an attractive actively studied target pathway. Because of their strong immunostimulatory activity, TLRs are thought to be a "double-edged sword" for systemic treatment, even in the cancer field. To solve this, we have developed dextran-based TAM targeting activating conjugate (D-TAC) technology, which successfully uses tumor-associated macrophages (TAMs) to deliver the TLR7 agonist DSP-0509. We used low molecular weight dextran to target CD206 high M2-type macrophages, activate them, and induce a change in phenotype to antitumor M1-type macrophages with rapid clearance from the body and astonishing antitumor activity. We also demonstrated that the antitumor effect of our best drug candidate 5DEX-0509R is dependent on the abundance of TAMs, which is consistent with their mechanism of action. We believe that 5DEX-0509R generated by D-TAC technology can be a clinically applicable immunotherapy targeting the TLR signaling pathway.

Comparative network-based analysis of toll-like receptor agonist, L-pampo signaling pathways in immune and cancer cells

Toll-like receptors (TLRs) are critical components to stimulate immune responses against various infections. Recently, TLR agonists have emerged as a promising way to activate anti-tumor immunity. L-pampo, a TLR1/2 and TLR3 agonist, induces humoral and cellular immune responses and also causes cancer cell death. In this study, we investigated the L-pampo-induced signals and delineated their interactions with molecular signaling pathways using RNA-seq in immune cells and colon and prostate cancer cells. We first constructed a template network with differentially expressed genes and influential genes from network propagation using the weighted gene co-expression network analysis. Next, we obtained perturbed modules using the above method and extracted core submodules from them by conducting Walktrap. Finally, we reconstructed the subnetworks of major molecular signals utilizing a shortest path-finding algorithm, TOPAS. Our analysis suggests that TLR signaling activated by L-pampo is transmitted to oxidative phosphorylation (OXPHOS) with reactive oxygen species (ROS) through PI3K-AKT and JAK-STAT only in immune and prostate cancer cells that highly express TLRs. This signal flow may further sensitize prostate cancer to L-pampo due to its high basal expression level of OXPHOS and ROS. Our computational approaches can be applied for inferring underlying molecular mechanisms from complex gene expression profiles.

TRIF-dependent signaling and its role in liver diseases

TIR domain-containing adaptor inducing IFN-β (TRIF) is a crucial adaptor molecule downstream of toll-like receptors 3 (TLR3) and 4 (TLR4). TRIF directly binds to TLR3 through its TIR domain, while it associates with TLR4 indirectly through the bridge adaptor molecule TRIF-related adaptor molecule (TRAM). TRIF plays a pivotal role in regulating interferon beta 1 (IFN-β) response, nuclear factor kappa B (NF-κB) signaling, apoptosis, and necroptosis signaling mediated by TLR3 and TLR4. It accomplishes these by recruiting and activating various kinases or transcription factors via its distinct domains. In this review, we comprehensively summarize the TRIF-dependent signaling pathways mediated by TLR3 and TLR4, elucidating key target molecules and downstream pathways. Furthermore, we provide an overview of TRIF's impact on several liver disorders, including drug-induced liver injury, ischemia-reperfusion liver injury, autoimmune hepatitis, viral hepatitis, alcohol-associated liver disease (ALD), metabolic dysfunction-associated steatotic liver disease (MASLD) and metabolic dysfunction-associated steatohepatitis (MASH). We also explore its effects on liver steatosis, inflammation, fibrosis, and carcinogenesis. A comprehensive understanding of the TRIF-dependent signaling pathways, as well as the intricate relationship between TRIF and liver diseases, can facilitate the identification of potential drug targets and the development of novel and effective therapeutics against hepatic disorders.

Harnessing innate immune pathways for therapeutic advancement in cancer

The innate immune pathway is receiving increasing attention in cancer therapy. This pathway is ubiquitous across various cell types, not only in innate immune cells but also in adaptive immune cells, tumor cells, and stromal cells. Agonists targeting the innate immune pathway have shown profound changes in the tumor microenvironment (TME) and improved tumor prognosis in preclinical studies. However, to date, the clinical success of drugs targeting the innate immune pathway remains limited. Interestingly, recent studies have shown that activation of the innate immune pathway can paradoxically promote tumor progression. The uncertainty surrounding the therapeutic effectiveness of targeted drugs for the innate immune pathway is a critical issue that needs immediate investigation. In this review, we observe that the role of the innate immune pathway demonstrates heterogeneity, linked to the tumor development stage, pathway status, and specific cell types. We propose that within the TME, the innate immune pathway exhibits multidimensional diversity. This diversity is fundamentally rooted in cellular heterogeneity and is manifested as a variety of signaling networks. The pro-tumor effect of innate immune pathway activation essentially reflects the suppression of classical pathways and the activation of potential pro-tumor alternative pathways. Refining our understanding of the tumor's innate immune pathway network and employing appropriate targeting strategies can enhance our ability to harness the anti-tumor potential of the innate immune pathway and ultimately bridge the gap from preclinical to clinical application.

Recent advances and remaining challenges in lung cancer therapy

ABSTRACT

Lung cancer remains the most common cause of cancer death. Given the continued research into new drugs and combination therapies, outcomes in lung cancer have been improved, and clinical benefits have been expanded to a broader patient population. However, the overall cure and survival rates for lung cancer patients remain low, especially in metastatic cases. Among the available lung cancer treatment options, such as surgery, radiation therapy, chemotherapy, targeted therapies, and alternative therapies, immunotherapy has shown to be the most promising. The exponential progress in immuno-oncology research and recent advancements made in the field of immunotherapy will further increase the survival and quality of life for lung cancer patients. Substantial progress has been made in targeted therapies using tyrosine kinase inhibitors and monoclonal antibody immune checkpoint inhibitors with many US Food And Drug Administration (FDA)-approved drugs targeting the programmed cell death ligand-1 protein (e.g., durvalumab, atezolizumab), the programmed cell death-1 receptor (e.g., nivolumab, pembrolizumab), and cytotoxic T-lymphocyte-associated antigen 4 (e.g., tremelimumab, ipilimumab). Cytokines, cancer vaccines, adoptive T cell therapies, and Natural killer cell mono- and combinational therapies are rapidly being studied, yet to date, there are currently none that are FDA-approved for the treatment of lung cancer. In this review, we discuss the current lung cancer therapies with an emphasis on immunotherapy, including the challenges for future research and clinical applications.

Small-molecule agents for cancer immunotherapy

Cancer immunotherapy, exemplified by the remarkable clinical benefits of the immune checkpoint blockade and chimeric antigen receptor T-cell therapy, is revolutionizing cancer therapy. They induce long-term tumor regression and overall survival benefit in many types of cancer. With the advances in our knowledge about the tumor immune microenvironment, remarkable progress has been made in the development of small-molecule drugs for immunotherapy. Small molecules targeting PRR-associated pathways, immune checkpoints, oncogenic signaling, metabolic pathways, cytokine/chemokine signaling, and immune-related kinases have been extensively investigated. Monotherapy of small-molecule immunotherapeutic drugs and their combinations with other antitumor modalities are under active clinical investigations to overcome immune tolerance and circumvent immune checkpoint inhibitor resistance. Here, we review the latest development of small-molecule agents for cancer immunotherapy by targeting defined pathways and highlighting their progress in recent clinical investigations.

Exploring TLR signaling pathways as promising targets in cervical cancer: The road less traveled

Cervical cancer is the leading cause of cancer-related deaths for women globally. Despite notable advancements in prevention and treatment, the identification of novel therapeutic targets remains crucial for cervical cancer. Toll-like receptors (TLRs) play an essential role in innate immunity as pattern-recognition receptors. There are several types of pathogen-associated molecular patterns (PAMPs), including those present in cervical cancer cells, which have the ability to activate toll-like receptors (TLRs). Recent studies have revealed dysregulated toll-like receptor (TLR) signaling pathways in cervical cancer, leading to the production of inflammatory cytokines and chemokines that can facilitate tumor growth and metastasis. Consequently, TLRs hold significant promise as potential targets for innovative therapeutic agents against cervical cancer. This book chapter explores the role of TLR signaling pathways in cervical cancer, highlighting their potential for targeted therapy while addressing challenges such as tumor heterogeneity and off-target effects. Despite these obstacles, targeting TLR signaling pathways presents a promising approach for the development of novel and effective treatments for cervical cancer.

Polymeric nanocapsules loaded with poly(I:C) and resiquimod to reprogram tumor-associated macrophages for the treatment of solid tumors

Background

In the tumor microenvironment (TME), tumor-associated macrophages (TAMs) play a key immunosuppressive role that limits the ability of the immune system to fight cancer. Toll-like receptors (TLRs) ligands, such as poly(I:C) or resiquimod (R848) are able to reprogram TAMs towards M1-like antitumor effector cells. The objective of our work has been to develop and evaluate polymeric nanocapsules (NCs) loaded with poly(I:C)+R848, to improve drug stability and systemic toxicity, and evaluate their targeting and therapeutic activity towards TAMs in the TME of solid tumors.

Methods

NCs were developed by the solvent displacement and layer-by-layer methodologies and characterized by dynamic light scattering and nanoparticle tracking analysis. Hyaluronic acid (HA) was chemically functionalized with mannose for the coating of the NCs to target TAMs. NCs loaded with TLR ligands were evaluated in vitro for toxicity and immunostimulatory activity by Alamar Blue, ELISA and flow cytometry, using primary human monocyte-derived macrophages. For in vivo experiments, the CMT167 lung cancer model and the MN/MCA1 fibrosarcoma model metastasizing to lungs were used; tumor-infiltrating leukocytes were evaluated by flow cytometry and multispectral immunophenotyping.

Results

We have developed polymeric NCs loaded with poly(I:C)+R848. Among a series of 5 lead prototypes, protamine-NCs were selected based on their physicochemical properties (size, charge, stability) and in vitro characterization, showing good biocompatibility on primary macrophages and ability to stimulate their production of T-cell attracting chemokines (CXCL10, CCL5) and to induce M1-like macrophages cytotoxicity towards tumor cells. In mouse tumor models, the intratumoral injection of poly(I:C)+R848-protamine-NCs significantly prevented tumor growth and lung metastasis. In an orthotopic murine lung cancer model, the intravenous administration of poly(I:C)+R848-prot-NCs, coated with an additional layer of HA-mannose to improve TAM-targeting, resulted in good antitumoral efficacy with no apparent systemic toxicity. While no significant alterations were observed in T cell numbers (CD8, CD4 or Treg), TAM-reprogramming in treated mice was confirmed by the relative decrease of interstitial versus alveolar macrophages, having higher CD86 expression but lower CD206 and Arg1 expression in the same cells, in treated mice.

Conclusion

Mannose-HA-protamine-NCs loaded with poly(I:C)+R848 successfully reprogram TAMs in vivo, and reduce tumor progression and metastasis spread in mouse tumors.

Harnessing the innate immune system by revolutionizing macrophage-mediated cancer immunotherapy

Immunotherapy is a promising and safer alternative to conventional cancer therapies. It involves adaptive T-cell therapy, cancer vaccines, monoclonal antibodies, immune checkpoint blockade (ICB), and chimeric antigen receptor (CAR) based therapies. However, most of these modalities encounter restrictions in solid tumours owing to a dense, highly hypoxic and immune-suppressive microenvironment as well as the heterogeneity of tumour antigens. The elevated intra-tumoural pressure and mutational rates within fastgrowing solid tumours present challenges in efficient drug targeting and delivery. The tumour microenvironment is a dynamic niche infiltrated by a variety of immune cells, most of which are macrophages. Since they form a part of the innate immune system, targeting macrophages has become a plausible immunotherapeutic approach. In this review, we discuss several versatile approaches (both at pre-clinical and clinical stages) such as the direct killing of tumour-associated macrophages, reprogramming pro-tumour macrophages to anti-tumour phenotypes, inhibition of macrophage recruitment into the tumour microenvironment, novel CAR macrophages, and genetically engineered macrophages that have been devised thus far. These strategies comprise a strong and adaptable macrophage-toolkit in the ongoing fight against cancer and by understanding their significance, we may unlock the full potential of these immune cells in cancer therapy.

Antibody preparation and age-dependent distribution of TLR8 in Bactrian camel spleens

BACKGROUND

Toll-like receptor 8 (TLR8) can recognize specific pathogen-associated molecular patterns and exert multiple immunological functions through activation of signaling cascades. However, the precise distribution and age-related alterations of TLR8 in the spleens of Bactrian camels have not yet been investigated. This study aimed to prepare a rabbit anti-Bactrian camel TLR8 polyclonal antibody and elucidate the distribution of TLR8 in the spleens of Bactrian camels at different age groups. The methodology involved the construction of the pET-28a-TLR8 recombinant plasmid, followed by the expression of TLR8 recombinant protein via prokaryotic expression. Subsequently, rabbits were immunized with the purified protein to prepare the TLR8 polyclonal antibody. Finally, twelve Alashan Bactrian camels were categorized into four groups: young (1-2 years), pubertal (3-5 years), middle-aged (6-16 years) and old (17-20 years). These camels received intravenous sodium pentobarbital (20 mg/kg) anesthesia and were exsanguinated to collect spleen samples. Immunohistochemical techniques were employed to observe and analyze the distribution patterns and age-related changes of TLR8 in the spleen.

RESULTS

The results showed that the TLR8 recombinant protein was expressed in the form of inclusion body with a molecular weight of 52 kDa, and the optimal induction condition involved 0.3 mmol/L IPTG induction for 8 h. The prepared antibody yielded a titer of 1:32 000, and the antibody demonstrated specific binding to TLR8 recombinant protein. TLR8 positive cells exhibited a consistent distribution pattern in the spleen across different age groups of Bactrian camels, primarily scattered within the periarterial lymphatic sheath of the white pulp, marginal zone, and red pulp. The predominant cell type expressing TLR8 was macrophages, with expression also observed in neutrophils and dendritic cells. Statistical analysis revealed that there were significant differences in the distribution density of TLR8 positive cells among different spleen regions at the same age, with the red pulp, marginal zone, and white pulp showing a descending order (P<0.05). Age-related changes indicated that the distribution density in the marginal zone and red pulp exhibited a similar trend of initially increasing and subsequently decreasing from young to old camels. As camels age, there was a significant decrease in the distribution density across all spleen regions (P<0.05).

CONCLUSIONS

The results confirmed that this study successfully prepared a rabbit anti-Bactrian camel TLR8 polyclonal antibody with good specificity. TLR8 positive cells were predominantly located in the red pulp and marginal zone of the spleen, signifying their pivotal role in the innate immune response of the spleen. Aging was found to significantly reduce the density of TLR8 positive cells, while leaving their scattered distribution characteristics unaffected. These findings provide valuable support for further investigations into the immunomorphology and immunosenescence of the spleen in Bactrian camels.

Nanoscale coordination polymer synergizes photodynamic therapy and toll-like receptor activation for enhanced antigen presentation and antitumor immunity

While activating antitumor immunity with toll-like receptor (TLR) agonists provides a promising approach toward cancer immunotherapy, existing TLR agonists, including resiquimod (R848), have shown poor tumor selectivity and ineffective TLR activation in tumors for optimal antitumor effects. We hypothesized that improved delivery of TLR agonists to tumors and their effective combination with tumor antigens could significantly enhance their antitumor efficacy. Here, we report a novel nanoscale coordination polymer, Ce6/R848, for the co-delivery of Ce6 photosensitizer to elicit immunogenic cell death via photodynamic therapy (PDT) and cholesterol-conjugated R848 (Chol-R848) for tumor-selective TLR7/8 activation. Upon light irradiation, Ce6-mediated PDT released tumor antigens while selectively delivered R848 activated TLR7/8 in the tumors to synergistically activate antigen-presenting cells and prime T cells for enhanced innate and adaptive antitumor immune responses. Ce6/R848 achieved a 50% cure rate and 99.4% inhibition of tumor growth in subcutaneous MC38 colorectal tumors with minimal systemic toxicity.

Toll-like receptor-guided therapeutic intervention of human cancers: molecular and immunological perspectives

Toll-like receptors (TLRs) serve as the body's first line of defense, recognizing both pathogen-expressed molecules and host-derived molecules released from damaged or dying cells. The wide distribution of different cell types, ranging from epithelial to immune cells, highlights the crucial roles of TLRs in linking innate and adaptive immunity. Upon stimulation, TLRs binding mediates the expression of several adapter proteins and downstream kinases, that lead to the induction of several other signaling molecules such as key pro-inflammatory mediators. Indeed, extraordinary progress in immunobiological research has suggested that TLRs could represent promising targets for the therapeutic intervention of inflammation-associated diseases, autoimmune diseases, microbial infections as well as human cancers. So far, for the prevention and possible treatment of inflammatory diseases, various TLR antagonists/inhibitors have shown to be efficacious at several stages from pre-clinical evaluation to clinical trials. Therefore, the fascinating role of TLRs in modulating the human immune responses at innate as well as adaptive levels directed the scientists to opt for these immune sensor proteins as suitable targets for developing chemotherapeutics and immunotherapeutics against cancer. Hitherto, several TLR-targeting small molecules (e.g., Pam3CSK4, Poly (I:C), Poly (A:U)), chemical compounds, phytocompounds (e.g., Curcumin), peptides, and antibodies have been found to confer protection against several types of cancers. However, administration of inappropriate doses of such TLR-modulating therapeutics or a wrong infusion administration is reported to induce detrimental outcomes. This review summarizes the current findings on the molecular and structural biology of TLRs and gives an overview of the potency and promises of TLR-directed therapeutic strategies against cancers by discussing the findings from established and pipeline discoveries.

Hacking the Immune Response to Solid Tumors: Harnessing the Anti-Cancer Capacities of Oncolytic Bacteria

Oncolytic bacteria are a classification of bacteria with a natural ability to specifically target solid tumors and, in the process, stimulate a potent immune response. Currently, these include species of Klebsiella, Listeria, Mycobacteria, Streptococcus/Serratia (Coley's Toxin), Proteus, Salmonella, and Clostridium. Advancements in techniques and methodology, including genetic engineering, create opportunities to "hijack" typical host-pathogen interactions and subsequently harness oncolytic capacities. Engineering, sometimes termed "domestication", of oncolytic bacterial species is especially beneficial when solid tumors are inaccessible or metastasize early in development. This review examines reported oncolytic bacteria-host immune interactions and details the known mechanisms of these interactions to the protein level. A synopsis of the presented membrane surface molecules that elicit particularly promising oncolytic capacities is paired with the stimulated localized and systemic immunogenic effects. In addition, oncolytic bacterial progression toward clinical translation through engineering efforts are discussed, with thorough attention given to strains that have accomplished Phase III clinical trial initiation. In addition to therapeutic mitigation after the tumor has formed, some bacterial species, referred to as "prophylactic", may even be able to prevent or "derail" tumor formation through anti-inflammatory capabilities. These promising species and their particularly favorable characteristics are summarized as well. A complete understanding of the bacteria-host interaction will likely be necessary to assess anti-cancer capacities and unlock the full cancer therapeutic potential of oncolytic bacteria.