Enterococcus peptidoglycan remodeling promotes checkpoint inhibitor cancer immunotherapy

Intestinal dysbiosis and colorectal cancer

ABSTRACT

Colorectal cancer (CRC) is one of the leading causes of cancer-related morbidity and mortality worldwide, highlighting the urgent need for novel preventive and therapeutic strategies. Emerging research highlights the crucial role of the gut microbiota, including bacteria, fungi, viruses, and their metabolites, in the pathogenesis of CRC. Dysbiosis, characterized by an imbalance in microbial composition, contributes to tumorigenesis through immune modulation, metabolic reprogramming, and genotoxicity. Specific bacterial species, such as Fusobacterium nucleatum and enterotoxigenic Bacteroides fragilis , along with fungal agents like Candida species, have been implicated in CRC progression. Moreover, viral factors, including Epstein-Barr virus and human cytomegalovirus, are increasingly recognized for their roles in promoting inflammation and immune evasion. This review synthesizes the latest evidence on host-microbiome interactions in CRC, emphasizing microbial metabolites, such as short-chain fatty acids and bile acids, which may act as both risk factors and therapeutic agents. We further discuss the latest advances in microbiota-targeted clinical applications, including biomarker-assisted diagnosis, next-generation probiotics, and microbiome-based interventions. A deeper understanding of the role of gut microbiome in CRC pathogenesis could pave the way for diagnostic, preventive, and personalized therapeutic strategies.

Unusual MurC Ligase and Peptidoglycan Discovered in Lachnospiraceae Using a Fluorescent L-Amino Acid Based Selective Labeling Probe

Developing selective labeling probes for specific bacterial taxa can not only facilitate the study of target bacteria but also deepen our understanding of the microbial diversity at structural and molecular levels. The availability of such probes, however, remains very limited. In this study, by exploiting the variation of amino acids in peptidoglycan stem peptide, we designed a fluorescent L-amino acid probe and found that it can selectively target the family Lachnospiraceae (a major Gram-positive family in murine gut microbiome) in vivo. The following in vitro test using two Roseburia species belonging to this family validated labeling by the probe. We then discovered that the labeling site is the first amino acid (L-alanine in most bacteria), which links the stem peptide with N-acetylmuramic acid, a process catalyzed by a highly conserved enzyme MurC. An enzyme assay of Roseburia MurC demonstrated its ability to conjugate a fluorescent L-amino acid and other non-L-Ala amino acids to UDP-N-acetylmuramic acid. Subsequent X-ray crystallography analysis uncovered a substantially enlarged inner space in this enzyme, which can partially explain its tolerance to these atypical substrates. The resulting unusual peptidoglycan structures lead to significantly reduced activation of the NOD immune receptors, suggesting a new mechanism for the host to accommodate these highly abundant commensals.

The interplay between gut microbiota, antibiotics, and immune checkpoint inhibitors in patients with cancer: A narrative review with biological and clinical aspects

Immune checkpoint inhibitors (ICIs) targeting the programmed cell death-1 (PD-1), programmed cell death ligand-1 (PD-L1), and cytotoxic T-lymphocyte antigen 4 (CTLA-4) pathways have revolutionized cancer therapy. However, primary and secondary resistance to ICI pose significant challenges. Recent studies underscore the critical role of gut microbiota (GM) in modulating ICI efficacy by shaping host immune responses and regulating the tumor microenvironment (TME). The composition of the GM has been linked to ICI treatment outcomes, with certain microbial taxa, such as Faecalibacterium spp., Bifidobacterium spp., Eubacterium spp., Roseburia spp., and Akkermansia muciniphila, associated with favorable responses. Mechanistically, the GM affects immune responses via multiple pathways, including induction of T cell differentiation, promotion of anti- or proinflammatory cytokine environments, and enhancement of T cell priming and effector functions. Moreover, microbial-derived metabolites play a role in shaping tumor immune responses and influencing ICI efficacy. Antibiotic treatment can disrupt GM diversity and composition (gut dysbiosis), potentially diminishing ICI effectiveness. A deeper understanding of the interplay between GM, antibiotic treatment, and ICI efficacy is crucial for developing personalized therapeutic strategies to improve patient outcomes. Herein, we review current evidence on the association between specific microbial taxa and tumor immunosurveillance, the impact of antibiotics on the GM composition and immune modulation, and its implications for ICI therapy efficacy.

Microbiota mechanisms in cancer progression and therapy

The composition of the microbiota in patients has been shown to correlate with cancer progression and response to therapy, highlighting unique opportunities to improve patient outcomes. In this review, we discuss the challenges and advancements in understanding the chemical mechanisms of specific microbiota species, pathways, and molecules involved in cancer progression and treatment. We also describe the modulation of cancer and immunotherapy by the microbiota, along with approaches for investigating microbiota enzymes and metabolites. Elucidating these specific microbiota mechanisms and molecules should offer new opportunities for developing enhanced diagnostics and therapeutics to improve outcomes for cancer patients. Nonetheless, many microbiota mechanisms remain to be determined and require innovative chemical genetic approaches.

Gut microbiota in cancer initiation, development and therapy

Cancer has long been associated with genetic and environmental factors, but recent studies reveal the important role of gut microbiota in its initiation and progression. Around 13% of cancers are linked to infectious agents, highlighting the need to identify the specific microorganisms involved. Gut microbiota can either promote or inhibit cancer growth by influencing oncogenic signaling pathways and altering immune responses. Dysbiosis can lead to cancer, while certain probiotics and their metabolites may help reestablish micro-ecological balance and improve anti-tumor immune responses. Research into targeted approaches that enhance therapy with probiotics is promising. However, the effects of probiotics in humans are complex and not yet fully understood. Additionally, methods to counteract harmful bacteria are still in development. Early clinical trials also indicate that modifying gut microbiota may help manage side effects of cancer treatments. Ongoing research is crucial to understand better how gut microbiota can be used to improve cancer prevention and treatment outcomes.

The Encapsulation Strategies for Targeted Delivery of Probiotics in Preventing and Treating Colorectal Cancer: A Review

Colorectal cancer (CRC) ranks as the third most prevalent cancer worldwide. It is associated with imbalanced gut microbiota. Probiotics can help restore this balance, potentially reducing the risk of CRC. However, the hostile environment and constant changes in the gastrointestinal tract pose significant challenges to the efficient delivery of probiotics to the colon. Traditional delivery methods are often insufficient due to their low viability and lack of targeting. To address these challenges, researchers are increasingly focusing on innovative encapsulation technologies. One such approach is single-cell encapsulation, which involves applying nanocoatings to individual probiotic cells. This technique can improve their resistance to the harsh gastrointestinal environment, enhance mucosal adhesion, and facilitate targeted release, thereby increasing the effectiveness of probiotic delivery. This article reviews the latest developments in probiotic encapsulation methods for targeted CRC treatment, emphasizing the potential benefits of emerging single-cell encapsulation techniques. It also analyzes and compares the advantages and disadvantages of current encapsulation technologies. Furthermore, it elucidates the underlying mechanisms through which probiotics can prevent and treat CRC, evaluates the efficacy and safety of probiotics in CRC treatment and adjuvant therapy, and discusses future directions and potential challenges in the targeted delivery of probiotics for CRC treatment and prevention.

Microrobotic Swarms for Cancer Therapy

Microrobotic swarms hold great promise for the revolution of cancer treatment. The coordination of miniaturized microrobots offers a unique approach to treating cancers at the cellular level with enhanced delivery efficiency and environmental adaptability. Prior studies have summarized the design, functionalization, and biomedical applications of microrobotic swarms. The strategies for actuation and motion control of swarms have also been introduced. In this review, we first give a detailed introduction to microrobot swarming. We then explore the design of microrobots and microrobotic swarms specifically engineered for cancer therapy, with a focus on tumor targeting, infiltration, and therapeutic efficacy. Moreover, the latest developments in active delivery methods and imaging techniques that enhance the precision of these systems are discussed. Finally, we categorize and analyze the various cancer therapies facilitated by functional microrobotic swarms, highlighting their potential to revolutionize treatment strategies for different cancer types.

Regulatory role of gut microbiota in immunotherapy of hepatocellular carcinoma

BACKGROUND

The gut microbiota plays a role in triggering innate immunity and regulating the immune microenvironment (IME) of hepatocellular carcinoma (HCC) by acting on various signaling receptors and transcription factors through its metabolites and related molecules. Furthermore, there is an increasing recognition of the gut microbiota as a potential therapeutic target for HCC, given its ability to modulate the efficacy of immune checkpoint inhibitors (ICIs).

OBJECTIVE

This review will discuss the mechanisms of gut microbiota in modulating immunotherapy of HCC, the predictive value of efficacy, and the therapeutic strategies for modulating the gut microbiota in detail.

METHODS

We conducted a systematic literature search in PubMed, Embase, Scopus, Cochrane Library, China National Knowledge Infrastructure, and Wanfang Chinese databases for articles involving the influence of gut microbiota on HCC immunotherapy.

RESULTS

The mechanisms underlying the effect of gut microbiota on HCC immunotherapy include gut-liver axis, tumor immune microenvironment (TIME), and antibodies. Patients who benefit from ICIs exhibit a higher abundance of gut microbiota. Antibiotics, fecal microbiota transplantation (FMT), probiotics, and prebiotics are effective methods to regulate gut microbiota.

CONCLUSION

The strong connection between the liver and gut will provide numerous opportunities for the development of microbiome-based diagnostics, treatments, or prevention strategies for HCC patients.

Gut microbiota affects PD-L1 therapy and its mechanism in melanoma

Immune checkpoint inhibitors (ICIs), particularly PD-1/PD-L1 blockade, have shown great success in treating melanoma. PD-L1 (B7-H1, CD274), a ligand of PD-1, binds to PD-1 on T cells, inhibiting their activation and proliferation through multiple pathways, thus dampening tumor-reactive T cell activity. Studies have linked PD-L1 expression in melanoma with tumor growth, invasion, and metastasis, making the PD-1/PD-L1 pathway a critical target in melanoma therapy. However, immune-related adverse events are common, reducing the effectiveness of anti-PD-L1 treatments. Recent evidence suggests that the gut microbiome significantly influences anti-tumor immunity, with the microbiome potentially reprogramming the tumor microenvironment and overcoming resistance to anti-PD-1 therapies in melanoma patients. This review explores the mechanisms of PD-1/PD-L1 in melanoma and examines how gut microbiota and its metabolites may help address resistance to anti-PD-1 therapy, offering new insights for improving melanoma treatment strategies.

Gut microbiota and gastrointestinal tumors: insights from a bibliometric analysis

Introduction

Despite the growing number of studies on the role of gut microbiota in treating gastrointestinal tumors, the overall research trends in this field remain inadequately characterized.

Methods

A bibliometric analysis was conducted using publications retrieved from the Web of Science Core Collection (up to September 30, 2024). Analytical tools including VOSviewer, CiteSpace, and an online bibliometric platform were employed to evaluate trends and hotspots.

Results

Analysis of 1,421 publications revealed significant geographical disparities in research output, with China and the United States leading contributions. Institutionally, the University of Adelaide, Zhejiang University, and Shanghai Jiao Tong University were prominent contributors. Authorship analysis identified Hannah R. Wardill as the most prolific author, while the International Journal of Molecular Sciences emerged as a leading journal. Rapidly growing frontiers include "proliferation," "inhibition," "immunotherapy," "drug delivery," and "tumorigenesis."

Discussion

This study provides a comprehensive overview of research trends and highlights emerging directions, aiming to advance scientific and clinical applications of gut microbiota in gastrointestinal tumor therapy.

Microbial Ecosystem Therapeutics 4 (MET4) elicits treatment-specific IgG responses associated with changes in gut microbiota in immune checkpoint inhibitor recipients with advanced solid tumors

BACKGROUND

Gut microbiome modulation has shown promise in its potential to treat cancer in combination with immunotherapy. Mechanistically, the pathways and routes by which gut microbiota may influence systemic and antitumor immunity remain uncertain. Here, we used blood and stool samples from Microbial Ecosystem Therapeutic 4 (MET4)-IO, an early-phase trial testing the safety and engraftment of the MET4 bacterial consortium in immune checkpoint inhibitor recipients, to assess how MET4 may affect systemic immunity.

METHODS

Circulating antibody responses induced by MET4 were assessed using an antimicrobial antibody flow cytometry assay on pretreatment and post-treatment plasma. Antibody responses were associated with taxonomic changes in stool identified by metagenomic sequencing. Mass cytometry was performed on peripheral blood mononuclear cells to identify shifts in circulating immune subsets associated with antibody responses.

RESULTS

Increases in circulating anti-MET4 immunoglobulin G (IgG) responses were measured by flow cytometry post-consortium treatment in MET4 recipients, but not untreated control participants, with five individuals displaying notably higher antibody responses. Stronger IgG responses were associated with greater increases in multiple taxa, including MET4 microbe Collinsella aerofaciens, which was previously linked with immune checkpoint response. However, these taxa were not enriched in the IgG-bound fraction post-MET4 treatment. Greater increases in circulating B cells and FoxP3+ CD4+ T cells post-MET4 treatment were observed in the blood of high IgG responders, while CD14+ and CD16+ monocyte populations were decreased in these individuals.

CONCLUSION

These results demonstrate the induction of treatment-specific circulating humoral immunity by a bacterial consortium and suggest potential mechanisms by which gut microbes may contribute to antitumor immunity.

Exploring the role of gut microbiota in colorectal liver metastasis through the gut-liver axis

Colorectal liver metastasis (CRLM) represents a major therapeutic challenge in colorectal cancer (CRC), with complex interactions between the gut microbiota and the liver tumor microenvironment (TME) playing a crucial role in disease progression via the gut-liver axis. The gut barrier serves as a gatekeeper, regulating microbial translocation, which influences liver colonization and metastasis. Through the gut-liver axis, the microbiota actively shapes the TME, where specific microbial species and their metabolites exert dual roles in immune modulation. The immunologically "cold" nature of the liver, combined with the influence of the gut microbiota on liver immunity, complicates effective immunotherapy. However, microbiota-targeted interventions present promising strategies to enhance immunotherapy outcomes by modulating the gut-liver axis. Overall, this review highlights the emerging evidence on the role of the gut microbiota in CRLM and provides insights into the molecular mechanisms driving the dynamic interactions within the gut-liver axis.

H3K18 lactylation-mediated nucleotide-binding oligomerization domain-2 (NOD2) expression promotes bilirubin-induced pyroptosis of astrocytes

Histone lactylation, a newly glycosis-related histone modification, plays a crucial role in the regulation of gene expression in various immune cells. However, the role of histone lactylation in astrocytes remains unclear. Here, this study showed that the H3K18 lactylation (H3K18la) levels were upregulated in primary astrocytes under unconjugated bilirubin (UCB) stimulation and hippocampus of bilirubin encephalopathy (BE) rats. Inhibition of glycolysis decreased H3K18la and attenuated pyroptosis both in vitro and in vivo. CUT& Tag and RNA-seq results revealed that H3K18la was enriched at the promoter of nucleotide-binding oligomerization domain 2 (NOD2) and promoted its transcription. Moreover, NOD2 boosted the activation of downstream mitogen-activated protein kinase (MAPK) and nuclear factor-kappa B (NF-κB) signaling pathways, which exacerbated the neuroinflammation of BE. Collectively, this study provides a novel understanding of epigenetic regulation in astrocytes, and interruption of the H3K18la/NOD2 axis may represent a novel therapeutic strategy for treating bilirubin encephalopathy.

Gut microbiota as a new target for anticancer therapy: from mechanism to means of regulation

In order to decipher the relationship between gut microbiota imbalance and cancer, this paper reviewed the role of intestinal microbiota in anticancer therapy and related mechanisms, discussed the current research status of gut microbiota as a biomarker of cancer, and finally summarized the reasonable means of regulating gut microbiota to assist cancer therapy. Overall, our study reveals that the gut microbiota can serve as a potential target for improving cancer management.

Gut microbiota-derived hexa-acylated lipopolysaccharides enhance cancer immunotherapy responses

The gut microbiome modulates immunotherapy treatment responses, and this may explain why immune checkpoint inhibitors, such as anti-PD-1, are only effective in some patients. Previous studies correlated lipopolysaccharide (LPS)-producing gut microbes with poorer prognosis; however, LPS from diverse bacterial species can range from immunostimulatory to inhibitory. Here, by functionally analysing faecal metagenomes from 112 patients with melanoma, we found that a subset of LPS-producing bacteria encoding immunostimulatory hexa-acylated LPS was enriched in microbiomes of clinical responders. In an implanted tumour mouse model of anti-PD-1 treatment, microbiota-derived hexa-acylated LPS was required for effective anti-tumour immune responses, and LPS-binding antibiotics and a small-molecule TLR4 antagonist abolished anti-PD-1 efficacy. Conversely, oral administration of hexa-acylated LPS to mice significantly augmented anti-PD-1-mediated anti-tumour immunity. Penta-acylated LPS did not improve anti-PD-1 efficacy in vivo and inhibited hexa-acylated LPS-induced immune activation in vitro. Microbiome hexa-acylated LPS therefore represents an accessible predictor and potential enhancer of immunotherapy responses.

Photocrosslinking and capture for the analysis of carbohydrate-dependent interactions

Carbohydrates play crucial roles in biological systems, including by mediating cell and protein interactions. The complexity and transient nature of carbohydrate-dependent interactions pose significant challenges for their characterization, as traditional techniques often fail to capture these low-affinity binding events. This review highlights the increasing utility of photocrosslinkers in studying carbohydrate-mediated interactions. Photocrosslinkers, such as aryl azides, benzophenones, and diazirines, allow for the capture of fleeting interactions by forming covalent bonds upon UV irradiation, enabling the downstream application of standard biochemical techniques. I discuss the three primary strategies for incorporating photocrosslinkers: synthetic small molecules, metabolic labeling, and exo-enzymatic labeling. I predict that the continued development and application of these methodologies will enhance our understanding of glycan-mediated interactions and their implications in health and disease.

A Review on the Extraction, Structural Characterization, Function, and Applications of Peptidoglycan

Peptidoglycan (PGN) is the primary component of bacterial cell walls, consisting of linear glycan chains formed by alternating linkages of N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM) through glycosidic bonds. It exhibits biological activity in various aspects, making it a biologically significant macromolecule with extensive industrial application. This review aims to explore the latest research advancements in the extraction techniques, structural characterization, functions, and applications of PGN. The review compares the advantages and limitations of traditional chemical lysis methods with modern mechanical-assisted and bio-assisted extraction techniques, discusses chemical composition analysis techniques and structural characterization methods of PGN. The review emphasizes the potential of PGN in immune modulation, specific recognition, and adsorption functions. Furthermore, the review examines potential applications of PGN in vaccine development, the livestock industry, the removal of harmful substances, and protein bioprocessing. In the end, based on the current development trend, future research directions for PGN are proposed, including in-depth studies on the mechanisms of PGN in different hosts and its immunomodulatory effects in various disease models. It is expected that a comprehensive reference framework for the research and application of PGN will be provided through this review, offering ideas and directions for further development and utilization.

The soil Mycobacterium sp. promotes health and longevity through different bacteria-derived molecules in Caenorhabditis elegans

Commensal bacteria and their derivatives hold significant promise as therapeutic interventions to delay aging. However, with the diverse nature of the soil microbiome and the long lifespan of mammalian models, the exploration of the influence of soil bacteria and bacteria-derived molecules on host aging remains limited. We conducted a lifespan screening in Caenorhabditis elegans using plant root bacterial collection. Our screening identified 8 genera of bacterial isolates capable of extending lifespan, with Mycobacterium sp. Root265 exhibits the most pronounced effect on lifespan extension. Biochemical analysis revealed two specific molecules derived from Root265, polysaccharides (PSs) and arabinogalactan peptidoglycan (AGP), responsible for lifespan extension via daf-16-dependent and -independent pathways, respectively. Notably, AGP exhibited a unique ability to enhance protein homeostasis effectively. Moreover, polar lipids originating from Root265 were found to extend lifespan while mitigating age-related BAS-1 decline in neurons. Intriguingly, even brief exposures to these bioactive compounds were sufficient to achieve the lifespan-promoting effects. We found diverse beneficial bacteria and anti-aging active compounds from soil bacteria. These findings highlight the potential of exploring bacterial derivatives as therapies targeting aging without the constraints associated with direct microbial interventions.

Gut microbial-derived N-acetylmuramic acid alleviates colorectal cancer via the AKT1 pathway

BACKGROUND

Gut microbial metabolites are recognised as critical effector molecules that influence the development of colorectal cancer (CRC). Peptidoglycan fragments (PGFs) produced by microbiota play a crucial role in maintaining intestinal homeostasis, but their role in CRC remains unclear.

OBJECTIVE

Here, we aimed to explore the potential contribution of PGFs in intestinal tumourigenesis.

DESIGN

The relative abundance of peptidoglycan synthase and hydrolase genes was assessed by metagenomic analysis. Specific PGFs in the faeces and serum of CRC patients were quantified using targeted mass spectrometry. The effects of PGF on intestinal tumourigenesis were systematically evaluated using various murine models of CRC and organoids derived from CRC patients. Downstream molecular targets were screened and evaluated using proteome microarray, transcriptome sequencing and rescue assays.

RESULTS

Metagenomic analysis across seven independent cohorts (n=1121) revealed a comprehensive reduction in peptidoglycan synthase gene relative abundance in CRC patients. Targeted mass spectrometry identified significant depletion of a specific PGF, N-acetylmuramic acid (NAM) in CRC patients, which decreased as tumours progressed (p<0.001). NAM significantly inhibits intestinal tumourigenesis in various models, including Apc Min/+, AOM/DSS-treated and MC38 tumour-bearing mice. Additionally, NAM inhibits the growth of patient-derived CRC organoids in a concentration-dependent manner. Mechanistically, NAM inhibits the activation of AKT1 by directly binding to it and blocking its phosphorylation, which is a partial mediator of NAM's anticancer effects.

CONCLUSION

The PGF NAM protects against intestinal tumourigenesis by targeting the AKT1 signalling pathway. NAM may serve as a novel potential preventive and therapeutic biomarker against CRC.

The oncobiome; what, so what, now what?

Microbial communities inhabiting various body sites play critical roles in the initiation, progression, and treatment of cancer. The gut microbiota, a highly diverse microbial ecosystem, interacts with immune cells to modulate inflammation and immune surveillance, influencing cancer risk and therapeutic outcomes. Local tissue microbiota may impact the transition from premalignant states to malignancy. Characterization of the intratumoral microbiota increasingly reveals distinct microbiomes that may influence tumor growth, immune responses, and treatment efficacy. Various bacteria species have been reported to modulate cancer therapies through mechanisms such as altering drug metabolism and shaping the tumor microenvironment (TME). For instance, gut or intratumoral bacterial enzymatic activity can convert prodrugs into active forms, enhancing therapeutic effects or, conversely, inactivating small-molecule chemotherapeutics. Specific bacterial species have also been linked to improved responses to immunotherapy, underscoring the microbiome's role in treatment outcomes. Furthermore, unique microbial signatures in cancer patients, compared with healthy individuals, demonstrate the diagnostic potential of microbiota. Beyond the gut, tumor-associated and local microbiomes also affect therapy by influencing inflammation, tumor progression, and drug resistance. This review explores the multifaceted relationships between microbiomes and cancer, focusing on their roles in modulating the TME, immune activation, and treatment efficacy. The diagnostic and therapeutic potential of bacterial members of microbiota represents a promising avenue for advancing precision oncology and improving patient outcomes. By leveraging microbial biomarkers and interventions, new strategies can be developed to optimize cancer diagnosis and treatment.

Lactiplantibacillus plantarum N1 derived lipoteichoic acid alleviates insulin resistance in association with modulation of the gut microbiota and amino acid metabolism

This study aimed to investigate the effects of heat-killed Lactiplantibacillus plantarum N1 (HK-N1) and lipoteichoic acid (LTA) derived from it on alleviating insulin resistance by modulating the gut microbiota and amino acid metabolism. High-fat diet (HFD)-fed mice were administered live bacteria or HK-N1, and the results demonstrated that HK-N1 significantly reduced epididymal adipocyte size and serum low density lipoprotein-cholesterol, and improved insulin resistance by increasing the YY peptide and glucagon-like peptide levels. HK-N1 also modulated the gut microbiome composition, enhancing microbiota uniformity and reducing the abundance of Ruminococcus, Oscillospira and norank_f_Mogibacteriaceae. Three main active substances obtained from HK-N1 (membrane protein, peptidoglycan, and lipoteichoic acid) were also used to investigate their potential effects in hyperglycemic zebrafish. Only LTA reduced blood sugar and altered the gut microbiome, particularly reducing Aeromonas, which is positively related to hyperglycemia. Untargeted metabolomics revealed that LTA improved vitamin and amino acid metabolism, thereby alleviating metabolic disorders in zebrafish. Collectively, our findings indicate that HK-N1, primarily through LTA, modulated insulin sensitivity by regulating the gut microbiota and amino acid metabolism, offering a potential therapeutic strategy for insulin resistance and type 2 diabetes mellitus.

Translocating gut pathobiont Enterococcus gallinarum induces TH17 and IgG3 anti-RNA-directed autoimmunity in mouse and human

Chronic autoimmune diseases often lead to long-term sequelae and require lifelong immunosuppression because of an incomplete understanding of the triggers and drivers in genetically predisposed patients. Gut bacteria that escape the gut barrier, known as translocating gut pathobionts, have been implicated as instigators and perpetuators of extraintestinal autoimmune diseases in mice. The gut microbial contributions to autoimmunity in humans remain largely unclear, including whether specific pathological human adaptive immune responses are triggered by such pathobionts. Here, we show that the translocating pathobiont Enterococcus gallinarum can induce both human and mouse interferon-γ+ T helper 17 (TH17) differentiation and immunoglobulin G3 (IgG3) subclass switch of anti-E. gallinarum RNA antibodies, which correlated with anti-human RNA autoantibody responses in patients with systemic lupus erythematosus (SLE) and autoimmune hepatitis, two extraintestinal autoimmune diseases. E. gallinarum RNA, but not human RNA, triggered Toll-like receptor 8 (TLR8), and TLR8-mediated human monocyte activation promoted human TH17 induction by E. gallinarum. Translocation of the pathobiont triggered increased anti-RNA autoantibody titers that correlated with renal autoimmune pathophysiology in murine gnotobiotic lupus models and with disease activity in patients with SLE. These studies elucidate cellular mechanisms of how a translocating gut pathobiont induces systemic human T cell- and B cell-dependent autoimmune responses and provide a framework for developing host- and microbiota-derived biomarkers and targeted therapies in autoimmune diseases.

The gut microbiome and cancer response to immune checkpoint inhibitors

Immune checkpoint inhibitors (ICIs) are widely used for cancer immunotherapy, yet only a fraction of patients respond. Remarkably, gut bacteria impact the efficacy of ICIs in fighting tumors outside of the gut. Certain strains of commensal gut bacteria promote antitumor responses to ICIs in a variety of preclinical mouse tumor models. Patients with cancer who respond to ICIs have a different microbiome compared with that of patients who don't respond. Fecal microbiota transplants (FMTs) from patients into mice phenocopy the patient tumor responses: FMTs from responders promote response to ICIs, whereas FMTs from nonresponders do not promote a response. In patients, FMTs from patients who have had a complete response to ICIs can overcome resistance in patients who progress on treatment. However, the responses to FMTs are variable. Though emerging studies indicate that gut bacteria can promote antitumor immunity in the absence of ICIs, this Review will focus on studies that demonstrate relationships between the gut microbiome and response to ICIs. We will explore studies investigating which bacteria promote response to ICIs in preclinical models, which bacteria are associated with response in patients with cancer receiving ICIs, the mechanisms by which gut bacteria promote antitumor immunity, and how microbiome-based therapies can be translated to the clinic.

The gut microbiome modulate response to immunotherapy in cancer

Gut microbiota have been reported to play an important role in the occurrence and development of malignant tumors. Currently, clinical studies have identified specific gut microbiota and its metabolites associated with efficacy of immunotherapy in multiple types of cancers. Preclinical investigations have elucidated that gut microbiota modulate the antitumor immunity and affect the efficacy of cancer immunotherapy. Certain microbiota and its metabolites may favorably remodel the tumor microenvironment by engaging innate and/or adaptive immune cells. Understanding how the gut microbiome interacts with cancer immunotherapy opens new avenues for improving treatment strategies. Fecal microbial transplants, probiotics, dietary interventions, and other strategies targeting the microbiota have shown promise in preclinical studies to enhance the immunotherapy. Ongoing clinical trials are evaluating these approaches. This review presents the recent advancements in understanding the dynamic interplay among the host immunity, the microbiome, and cancer immunotherapy, as well as strategies for modulating the microbiome, with a view to translating into clinical applications.

Gut Microbiota-Tumor Microenvironment Interactions: Mechanisms and Clinical Implications for Immune Checkpoint Inhibitor Efficacy in Cancer

Cancer immunotherapy has transformed cancer treatment in recent years, with immune checkpoint inhibitors (ICIs) emerging as a key therapeutic approach. ICIs work by inhibiting the mechanisms that allow tumors to evade immune detection. Although ICIs have shown promising results, especially in solid tumors, patient responses vary widely due to multiple intrinsic and extrinsic factors within the tumor microenvironment. Emerging evidence suggests that the gut microbiota plays a pivotal role in modulating immune responses at the tumor site and may even influence treatment outcomes in cancer patients receiving ICIs. This review explores the complex interactions between the gut microbiota and the tumor microenvironment, examining how these interactions could impact the effectiveness of ICI therapy. Furthermore, we discuss how dysbiosis, an imbalance in gut microbiota composition, may contribute to resistance to ICIs, and highlight microbiota-targeted strategies to potentially overcome this challenge. Additionally, we review recent studies investigating the diagnostic potential of microbiota profiles in cancer patients, considering how microbial markers might aid in early detection and stratification of patient responses to ICIs. By integrating insights from recent preclinical and clinical studies, we aim to shed light on the potential of microbiome modulation as an adjunct to cancer immunotherapy and as a diagnostic tool, paving the way for personalized therapeutic approaches that optimize patient outcomes.

[Intestinal Flora Dysregulation and Lung Cancer: Mechanism Analysis and Clinical Application]

Lung cancer is the deadliest form of cancer globally, with millions of new cases diagnosed each year. Although rapid advancements in surgical techniques, targeted therapies, and immunotherapy have significantly improved patient outcomes, the overall 5-year survival rate remains disappointingly low. Recent studies have highlighted the vital role of gut microbiota in maintaining host health and its close association with the onset and progression of lung cancer through various mechanisms. This article provides a systematic analysis of the role of gut microbiota in lung cancer, focusing on its immunomodulatory and metabolic functions, as well as its potential applications in treatment, while also exploring its prospects for clinical use.
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Revealing NOD1-Activating Gram-Positive Gut Microbiota via in Vivo Labeling with a meso-Diaminopimelic Acid Probe

As an important receptor in a host's immune and metabolic systems, NOD1 is usually activated by Gram-negative bacteria having meso-diaminopimelic acid (m-DAP) in their peptidoglycan (PGN). But some atypical Gram-positive bacteria also contain m-DAP in their PGN, giving them the potential to activate NOD1. The prevalence of m-DAP-type Gram-positive bacteria in the gut, however, remains largely unknown. Here, we report a stem-peptide-based m-DAP-containing tetrapeptide probe for labeling and identifying m-DAP-type Gram-positive microbiota. The probe was synthesized via a five-step convergent approach and demonstrated moderate selectivity toward m-DAP-type bacteria in vitro. In vivo labeling revealed that ∼13.7% of the mouse gut microbiota (mostly Gram-positive) was selectively labeled. We then identified Oscillibacter and several other Gram-positive genera in this population, most of which were previously unknown m-DAP-type bacteria. The following functional assay showed that Oscillibacter's PGN could indeed activate NOD1, suggesting an overlooked NOD1-activating role for these Gram-positive bacteria. These findings deepen our understanding of the structural diversity of gut microbes and their interactions with the host's immune system.

Understanding the role of the gut microbiome in solid tumor responses to immune checkpoint inhibitors for personalized therapeutic strategies: a review

Immunotherapy, especially immune checkpoint inhibitor (ICI) therapy, has yielded remarkable outcomes for some patients with solid cancers, but others do not respond to these treatments. Recent research has identified the gut microbiota as a key modulator of immune responses, suggesting that its composition is closely linked to responses to ICI therapy in cancer treatment. As a result, the gut microbiome is gaining attention as a potential biomarker for predicting individual responses to ICI therapy and as a target for enhancing treatment efficacy. In this review, we discuss key findings from human observational studies assessing the effect of antibiotic use prior to ICI therapy on outcomes and identifying specific gut bacteria associated with favorable and unfavorable responses. Moreover, we review studies investigating the possibility of patient outcome prediction using machine learning models based on gut microbiome data before starting ICI therapy and clinical trials exploring whether gut microbiota modulation, for example via fecal microbiota transplantation or live biotherapeutic products, can improve results of ICI therapy in patients with cancer. We also briefly discuss the mechanisms through which the gut microbial-derived products influence immunotherapy effectiveness. Further research is necessary to fully understand the complex interactions between the host, gut microbiota, and immunotherapy and to develop personalized strategies that optimize responses to ICI therapy.

Postbiotics From Lactobacillus Johnsonii Activates Gut Innate Immunity to Mitigate Alcohol-Associated Liver Disease

Prolonged alcohol consumption disrupts the gut microbiota and the immune system, contributing to the pathogenesis of alcohol-associated liver disease (ALD). Probiotic-postbiotic intervention strategies can effectively relieve ALD by maintaining gut homeostasis. Herein, the efficacy of heat-killed Lactobacillus johnsonii (HKLJ) in mitigating alcoholic liver damage is demonstrated in mouse models of ALD. The gut-liver axis is identified as a pivotal pathway for the protective effects of L. johnsonii against ALD. Specifically, HKLJ is found to upregulate the expression of intestinal lysozymes, thereby enhancing the production of immunoregulatory substances from gut bacteria, which subsequently activated the Nucleotide-binding oligomerization domain 2 (NOD2)-interleukin (IL-23)-IL-22 innate immune axis. The elevated IL-22 upregulated the antimicrobial peptide synthesis to maintain intestinal homeostasis and moreover activated the Signal transducer and activator of Transcription3 (STAT3) pathway in the liver to facilitate the repair of hepatic injuries. The heat-killed L. johnsonii provoked immunity helps correct the gut microbiota dysbiosis, specifically by reversing the reduction of butyrate-producing bacteria (such as Faecalibaculum rodentium) and the expansion of opportunistic pathogens (such as Helicobacter sp. and Pichia kudriavzevii) induced by ethanol. The findings provide novel insights into the gut microbiota-liver axis that may be leveraged to enhance the treatment of ALD.

Gut microbial metabolites in cancer therapy

The gut microbiota plays a crucial role in maintaining homeostasis and promoting health. A growing number of studies have indicated that gut microbiota can affect cancer development, prognosis, and treatment through their metabolites. By remodeling the tumor microenvironment and regulating tumor immunity, gut microbial metabolites significantly influence the efficacy of anticancer therapies, including chemo-, radio-, and immunotherapy. Several novel therapies that target gut microbial metabolites have shown great promise in cancer models. In this review, we summarize the current research status of gut microbial metabolites in cancer, aiming to provide new directions for future tumor therapy.

Insights into the Relationship Between the Gut Microbiome and Immune Checkpoint Inhibitors in Solid Tumors

Immunotherapy with immune checkpoint inhibitors represents a revolutionary approach to the treatment of solid tumors, including malignant melanoma, lung cancer, and gastrointestinal malignancies. Anti-CTLA-4 and anti-PD-1/PDL-1 therapies provide prolonged survival for cancer patients, but their efficacy and safety are highly variable. This review focuses on the crucial role of the gut microbiome in modulating the efficacy and toxicity of immune checkpoint blockade. Studies suggest that the composition of the gut microbiome may influence the response to immunotherapy, with specific bacterial strains able to promote an anti-tumor immune response. On the other hand, dysbiosis may increase the risk of adverse effects, such as immune-mediated colitis. Interventions aimed at modulating the microbiome, including the use of probiotics, prebiotics, fecal microbial transplantation, or dietary modifications, represent promising strategies to increase treatment efficacy and reduce toxicity. The combination of immunotherapy with the microbiome-based strategy opens up new possibilities for personalized treatment. In addition, factors such as physical activity and nutritional supplementation may indirectly influence the gut ecosystem and consequently improve treatment outcomes in refractory patients, leading to enhanced patient responses and prolonged survival.

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.

The danger theory of immunity revisited

The danger theory of immunity, introduced by Polly Matzinger in 1994, posits that tissue stress, damage or infection has a decisive role in determining immune responses. Since then, a growing body of evidence has supported the idea that the capacity to elicit cognate immune responses (immunogenicity) relies on the combination of antigenicity (the ability to be recognized by T cell receptors or antibodies) and adjuvanticity (additional signals arising owing to tissue damage). Here, we discuss the molecular foundations of the danger theory while focusing on immunologically relevant damage-associated molecular patterns, microorganism-associated molecular patterns, and neuroendocrine stress-associated immunomodulatory molecules, as well as on their receptors. We critically evaluate patient-relevant evidence, examining how cancer cells and pathogenic viruses suppress damage-associated molecular patterns to evade immune recognition, how intestinal dysbiosis can reduce immunostimulatory microorganism-associated molecular patterns and compromise immune responses, and which hereditary immune defects support the validity of the danger theory. Furthermore, we incorporate the danger hypothesis into a close-to-fail-safe hierarchy of immunological tolerance mechanisms that also involve the clonal deletion and inactivation of immune cells.

Potential of natural products and gut microbiome in tumor immunotherapy

Immunotherapy is a novel treatment approach for malignant tumors, which has opened a new journey of anti-tumor therapy. Although some patients will show a positive response to immunotherapy, unfortunately, most patients and cancer types do not achieve an ideal response to immunotherapy. Therefore, it is urgent to search for the pathogenesis of sensitized immunotherapy. This review indicates that Fusobacterium nucleatum, Coprobacillus cateniformis, Akkermansia muciniphila, Bifidobacterium, among others, as well as intestinal microbial metabolites are closely associated with resistance to anti-tumor immunotherapy. While natural products of pectin, inulin, jujube, anthocyanins, ginseng polysaccharides, diosgenin, camu-camu, and Inonotus hispidus (Bull).Fr. P. Karst, Icariside I, Safflower yellow, Ganoderma lucidum, and Ginsenoside Rk3, and other Chinese native medicinal compound prescriptions to boost their efficacy of anti-tumor immunotherapy through the regulation of microbiota and microbiota metabolites. However, current research mainly focuses on intestinal, liver, and lung cancer. In the future, natural products could be a viable option for treating malignant tumors, such as pancreatic, esophageal, and gastric malignancies, via sensitizing immunotherapy. Besides, the application characteristics of different types, sources and efficacy of natural products in different immune resistance scenarios also need to be further clarified through the development of future immunotherapy-related studies.

Chemical genetic approaches to dissect microbiota mechanisms in health and disease

Advances in genomics, proteomics, and metabolomics have revealed associations between specific microbiota species in health and disease. However, the precise mechanism(s) of action for many microbiota species and molecules have not been fully elucidated, limiting the development of microbiota-based diagnostics and therapeutics. In this Review, we highlight innovative chemical and genetic approaches that are enabling the dissection of microbiota mechanisms and providing causation in health and disease. Although specific microbiota molecules and mechanisms have begun to emerge, new approaches are still needed to go beyond phenotypic associations and translate microbiota discoveries into actionable targets and therapeutic leads to prevent and treat diseases.

Outgrowth of Escherichia is susceptible to aggravation of systemic lupus erythematosus

BACKGROUND

Systemic lupus erythematosus (SLE) is linked to host gut dysbiosis. Here we performed faecal gut microbiome sequencing to investigate SLE-pathogenic gut microbes and their potential mechanisms.

METHODS

There were 134 healthy controls (HCs) and 114 SLE cases for 16 S ribosomal RNA (rRNA) sequencing and 97 HCs and 124 SLE cases for shotgun metagenomics. Faecal microbial changes and associations with clinical phenotypes were evaluated, and SLE-associated microbial genera were identified in amplicon analysis. Next, metagenomic sequencing was applied for accurate identification of microbial species and discovery of their metabolic pathways and immunogenic peptides both relevant to SLE. Finally, contribution of specific taxa to disease development was confirmed by oral gavage into lupus-prone MRL/lpr mice.

RESULTS

SLE patients had gut microbiota richness reduction and composition alteration, particularly lupus nephritis and active patients. Proteobacteria/Bacteroidetes (P/B) ratio was remarkably up-regulated, and Escherichia was identified as the dominantly expanded genus in SLE, followed by metagenomics accurately located Escherichia coli and Escherichia unclassified species. Significant associations primarily appeared among Escherichia coli, metabolic pathways of purine nucleotide salvage or peptidoglycan maturation and SLE disease activity index (SLEDAI), and between multiple epitopes from Escherichia coli and disease activity or renal involvement phenotype. Finally, gavage with faecal Escherichia revealed that it upregulated lupus-associated serum traits and aggravated glomerular lesions in MRL/lpr mice.

CONCLUSION

We characterize a novel SLE exacerbating Escherichia outgrowth and suggest its contribution to SLE procession may be partially associated with metabolite changes and cross-reactivity of gut microbiota-associated epitopes and host autoantigens. The findings could provide a deeper insight into gut Escherichia in the procession of SLE.

Microbiome dynamics in immune checkpoint blockade

Immune checkpoint blockade (ICB) is one of the leading immunotherapies, although a variable extent of resistance has been observed among patients and across cancer types. Among the efforts underway to overcome this challenge, the microbiome has emerged as a factor affecting the responsiveness and efficacy of ICB. Active research, facilitated by advances in sequencing techniques, is assessing the predominant influence of the intestinal microbiome, as well as the effects of the presence of an intratumoral microbiome. In this review, we describe recent findings from clinical trials, observational studies of human patients, and animal studies on the impact of the microbiome on the efficacy of ICB, highlighting the role of the intestinal and tumor microbiomes and the contribution of methodological advances in their study.

When the Host Encounters the Cell Wall and Vice Versa

Peptidoglycan (PGN) and associated surface structures such as secondary polymers and capsules have a central role in the physiology of bacteria. The exoskeletal PGN heteropolymer is the major determinant of cell shape and allows bacteria to withstand cytoplasmic turgor pressure. Thus, its assembly, expansion, and remodeling during cell growth and division need to be highly regulated to avoid compromising cell survival. Similarly, regulation of the assembly impacts bacterial cell shape; distinct shapes enhance fitness in different ecological niches, such as the host. Because bacterial cell wall components, in particular PGN, are exposed to the environment and unique to bacteria, these have been coopted during evolution by eukaryotes to detect bacteria. Furthermore, the essential role of the cell wall in bacterial survival has made PGN an important signaling molecule in the dialog between host and microbes and a target of many host responses. Millions of years of coevolution have resulted in a pivotal role for PGN fragments in shaping host physiology and in establishing a long-lasting symbiosis between microbes and the host. Thus, perturbations of this dialog can lead to pathologies such as chronic inflammatory diseases. Similarly, pathogens have devised sophisticated strategies to manipulate the system to enhance their survival and growth.

Cold and hot tumors: from molecular mechanisms to targeted therapy

Immunotherapy has made significant strides in cancer treatment, particularly through immune checkpoint blockade (ICB), which has shown notable clinical benefits across various tumor types. Despite the transformative impact of ICB treatment in cancer therapy, only a minority of patients exhibit a positive response to it. In patients with solid tumors, those who respond well to ICB treatment typically demonstrate an active immune profile referred to as the "hot" (immune-inflamed) phenotype. On the other hand, non-responsive patients may exhibit a distinct "cold" (immune-desert) phenotype, differing from the features of "hot" tumors. Additionally, there is a more nuanced "excluded" immune phenotype, positioned between the "cold" and "hot" categories, known as the immune "excluded" type. Effective differentiation between "cold" and "hot" tumors, and understanding tumor intrinsic factors, immune characteristics, TME, and external factors are critical for predicting tumor response and treatment results. It is widely accepted that ICB therapy exerts a more profound effect on "hot" tumors, with limited efficacy against "cold" or "altered" tumors, necessitating combinations with other therapeutic modalities to enhance immune cell infiltration into tumor tissue and convert "cold" or "altered" tumors into "hot" ones. Therefore, aligning with the traits of "cold" and "hot" tumors, this review systematically delineates the respective immune characteristics, influencing factors, and extensively discusses varied treatment approaches and drug targets based on "cold" and "hot" tumors to assess clinical efficacy.

The impact of traditional Chinese medicine and dietary compounds on modulating gut microbiota in hepatic fibrosis: A review

Traditional Chinese medicine (TCM) and dietary compounds have a profound influence on the regulation of gut microbiota (GM) in hepatic fibrosis (HF). Certain substances found in both food and herbs that are edible and medicinal, such as dietary fiber, polyphenols, and polysaccharides, can generate beneficial metabolites like short-chain fatty acids (SCFAs), bile acids (BAs), and tryptophan (Trp). These compounds contribute to regulate the GM, reduce levels of endotoxins in the liver, and alleviate fibrosis and inflammation in the liver. Furthermore, they enhance the composition and functionality of GM, promoting the growth of beneficial bacteria while inhibiting the proliferation of harmful bacteria. These mechanisms mitigate the inflammatory response in the intestines and maintain the integrity of the intestinal barrier. The purpose of this review is to analyze how the GM regulates the pathogenesis of HF, evaluate the regulatory effect of TCM and dietary compounds on the intestinal microflora, with a particular emphasis on modulating flora structure, enhancing gut barrier function, and addressing associated pathogenic factors, thereby provide new insights for the treatment of HF.

Influence of the gut microbiota on immune cell interactions and cancer treatment

The tumour microenvironment represents a novel frontier in oncological research. Over the past decade, accumulating evidence has underscored the importance of the tumour microenvironment (TME), including tumour cells, stromal cells, immune cells, and various secreted factors, which collectively influence tumour growth, invasion, and responses to therapeutic agents. Immune cells within the TME are now widely acknowledged to play pivotal roles in tumour development and treatment. While some perspectives have posited that immune cells within the TME facilitate tumour progression and confer resistance to therapeutic interventions, contrasting conclusions also exist. Affirmative and negative conclusions appear to be context dependent, and a unified consensus has yet to be reached. The burgeoning body of research on the relationship between the gut microbiota and tumours in recent years has led to a growing understanding. Most studies have indicated that specific components of the gut microbiota, such as unique bacterial communities or specific secretory factors, play diverse roles in regulating immune cells within the TME, thereby influencing the prognosis and outcomes of cancer treatments. A detailed understanding of these factors could provide novel insights into the TME and cancer therapy. In this study, we aimed to synthesise information on the interactions between the gut microbiota and immune cells within the TME, providing an in-depth exploration of the potential guiding implications for future cancer therapies.

Distinctive Immune Signatures Driven by Structural Alterations in Desmuramylpeptide NOD2 Agonists

Herein we report on the design, synthesis and biological evaluation of a series of nucleotide-binding oligomerization-domain-containing protein 2 (NOD2) desmuramylpeptide agonists. The structural prerequisites that shape both physicochemical and immunomodulatory profiles of desmuramylpeptide NOD2 agonists have been delineated. Within this context, we identified 3, a butyrylated desmuramylpeptide, as a potent in vitro NOD2 agonist (EC50 = 4.6 nM), exhibiting an almost 17-fold enhancement in potency compared to its unsubstituted counterpart 1 (EC50 = 77.0 nM). The novel set of desmuramylpeptides demonstrate unique in vitro immunomodulatory activities. They elicited cytokine production in peripheral blood mononuclear cells (PBMCs), both alone and in conjunction with lipopolysaccharide (LPS). The spermine-decorated 32 also stimulated the LPS-induced cytotoxic activity (2.95-fold) of PBMCs against K562 cancer cells. Notably, the cholesterol-conjugate 26 displayed anti-inflammatory actions, highlighted by its capacity to convert the inflammatory monocyte subset into an anti-inflammatory phenotype. Finally, the eicosapentaenoylated derivative 23 augmented antigen presentation by mouse bone marrow-derived dendritic cells (BMDCs), thus highlighting its potential as a vaccine adjuvant.

Elevated muramyl dipeptide by sialic acid-facilitated postantibiotic pathobiont expansion contributes to gut dysbiosis-induced mastitis in mice

INTRODUCTION

In responses to antibiotics exposure, gut dysbiosis is a risk factor not only for pathogen infection but also for facilitating pathobiont expansion, resulting in increased inflammatory responses in the gut and distant organs. However, how this process is regulated has not been fully elucidated.

OBJECTIVES

In this study, we investigated the role of sialic acid, a host-derived carbohydrate, in the pathogenesis of gut dysbiosis-derived inflammation in distant organs.

METHODS

Ampicillin (Amp)-induced gut dysbiotic mice were treated with N-glycolylneuraminic acid (Neu5Gc) and N-acetylneuraminic acid (Neu5Ac) for three weeks to assess the role of sialic acids in mastitis. The underlying mechanism by which sialic acids regulate mastitis was explored using 16S rRNA sequencing, transcriptomics and employed multiple molecular approaches.

RESULTS

Administration of Neu5Ac and Neu5Gc exacerbated gut dysbiosis-induced mastitis and systemic inflammation. The gut dysbiosis caused by Amp was also aggravated by sialic acid. Notably, increased Enterococcus expansion, which was positively correlated with inflammatory markers, was observed in both Neu5Ac- and Neu5Gc-treated gut dysbiotic mice. Treatment of mice with Enterococcus cecorum (E. cecorum) aggravated gut dysbiosis-induced mastitis. Mechanically, sialic acid-facilitated E. cecorum expansion promoted muramyl dipeptide (MDP) release, which induced inflammatory responses by activating the NOD2-RIP2-NF-κB axis.

CONCLUSIONS

Collectively, our data reveal a role of sialic acid-facilitated postantibiotic pathobiont expansion in gut dysbiosis-associated inflammation, highlighting a potential strategy for disease prevention by regulating the MDP-NOD2-RIP2 axis.

Activation of NOD1 on tumor-associated macrophages augments CD8+ T cell-mediated antitumor immunity in hepatocellular carcinoma

The efficacy of immunotherapy targeting the PD-1/PD-L1 pathway in hepatocellular carcinoma (HCC) is limited. NOD-like receptors (NLRs) comprise a highly evolutionarily conserved family of cytosolic bacterial sensors, yet their impact on antitumor immunity against HCC remains unclear. In this study, we uncovered that NOD1, a well-studied member of NLR family, exhibits predominant expression in tumor-associated macrophages (TAMs) and correlates positively with improved prognosis and responses to anti-PD-1 treatments in patients with HCC. Activation of NOD1 in vivo augments antitumor immunity and enhances the effectiveness of anti-PD-1 therapy. Mechanistically, NOD1 activation resulted in diminished expression of perilipin 5, thereby hindering fatty acid oxidation and inducing free fatty acid accumulation in TAMs. This metabolic alteration promoted membrane localization of the costimulatory molecule OX40L in a lipid modification-dependent manner, thereby activating CD8+ T cells. These findings unveil a previously unrecognized role for NOD1 in fortifying antitumor T cell immunity in HCC, potentially advancing cancer immunotherapy.

Gut bacteria, host immunity, and colorectal cancer: From pathogenesis to therapy

The emergence of 16S rRNA and metagenomic sequencing has gradually revealed the close relationship between dysbiosis and colorectal cancer (CRC). Recent studies have confirmed that intestinal dysbiosis plays various roles in the occurrence, development, and therapeutic response of CRC. Perturbation of host immunity is one of the key mechanisms involved. The intestinal microbiota, or specific bacteria and their metabolites, can modulate the progression of CRC through pathogen recognition receptor signaling or via the recruitment, polarization, and activation of both innate and adaptive immune cells to reshape the protumor/antitumor microenvironment. Therefore, the administration of gut bacteria to enhance immune homeostasis represents a new strategy for the treatment of CRC. In this review, we cover recent studies that illuminate the role of gut bacteria in the progression and treatment of CRC through orchestrating the immune response, which potentially offers insights for subsequent transformative research.

Personalised medicine based on host genetics and microbiota applied to colorectal cancer

Colorectal cancer (CRC) ranks second in incidence and third in cancer mortality worldwide. This situation, together with the understanding of the heterogeneity of the disease, has highlighted the need to develop a more individualised approach to its prevention, diagnosis and treatment through personalised medicine. This approach aims to stratify patients according to risk, predict disease progression and determine the most appropriate treatment. It is essential to identify patients who may respond adequately to treatment and those who may be resistant to treatment to avoid unnecessary therapies and minimise adverse side effects. Current research is focused on identifying biomarkers such as specific mutated genes, the type of mutations and molecular profiles critical for the individualisation of CRC diagnosis, prognosis and treatment guidance. In addition, the study of the intestinal microbiota as biomarkers is being incorporated due to the growing scientific evidence supporting its influence on this disease. This article comprehensively addresses the use of current and emerging diagnostic, prognostic and predictive biomarkers in precision medicine against CRC. The effects of host genetics and gut microbiota composition on new approaches to treating this disease are discussed. How the gut microbiota could mitigate the side effects of treatment is reviewed. In addition, strategies to modulate the gut microbiota, such as dietary interventions, antibiotics, and transplantation of faecal microbiota and phages, are discussed to improve CRC prevention and treatment. These findings provide a solid foundation for future research and improving the care of CRC patients.

Microbial Community Structure and Metabolic Function in the Venom Glands of the Predatory Stink Bug, Picromerus lewisi (Hemiptera: Pentatomidae)

The predatory stink bug, Picromerus lewisi (Hemiptera: Pentatomidae), is an important and valuable natural enemy of insect pests in their ecosystems. While insects are known to harbor symbiotic microorganisms, and these microbial symbionts play a crucial role in various aspects of the host's biology, there is a paucity of knowledge regarding the microbiota present in the venom glands of P. lewisi. This study investigated the venom glands of adult bugs using both traditional in vitro isolation and cultural methods, as well as Illumina high-throughput sequencing technology. Additionally, the carbon metabolism of the venom gland's microorganisms was analyzed using Biolog ECO metabolic phenotyping technology. The results showed 10 different culturable bacteria where the dominant ones were Enterococcus spp. and Lactococcus lactis. With high-throughput sequencing, the main bacterial phyla in the microbial community of the venom glands of P. lewisi were Proteobacteria (78.1%) and Firmicutes (20.3%), with the dominant bacterial genera being Wolbachia, Enterococcus, Serratia, and Lactococcus. At the fungal community level, Ascomycota accounted for the largest proportion (64.1%), followed by Basidiomycota (27.6%), with Vishniacozyma, Cladosporium, Papiliotrema, Penicillium, Fusarium, and Aspergillus as the most highly represented fungal genera. The bacterial and fungal community structure of the venom glands of P. lewisi exhibited high species richness and diversity, along with a strong metabolism of 22 carbon sources. Functional prediction indicated that the primary dominant function of P. lewisi venom-gland bacteria was metabolism. The dominant eco-functional groups of the fungal community included undefined saprotroph, fungal parasite-undefined saprotroph, unassigned, endophyte-plant pathogen, plant pathogen-soil saprotroph-wood saprotroph, animal pathogen-endophyte-plant pathogen-wood saprotroph, plant pathogen, and animal pathogen-endophyte-epiphyte-plant pathogen-undefined saprotroph. These results provide a comprehensive characterization of the venom-gland microbiota of P. lewisi and demonstrate the stability (over one week) of the microbial community within the venom glands. This study represents the first report on the characterization of microbial composition from the venom glands of captive-reared P. lewisi individuals. The insights gained from this study are invaluable for future investigations into P. lewisi's development and the possible interactions between P. lewisi's microbiota and some Lepidopteran pests.

Long-distance microbial mechanisms impacting cancer immunosurveillance

The intestinal microbiota determines immune responses against extraintestinal antigens, including tumor-associated antigens. Indeed, depletion or gross perturbation of the microbiota undermines the efficacy of cancer immunotherapy, thereby compromising the clinical outcome of cancer patients. In this review, we discuss the long-distance effects of the gut microbiota and the mechanisms governing antitumor immunity, such as the translocation of intestinal microbes into tumors, migration of leukocyte populations from the gut to the rest of the body, including tumors, as well as immunomodulatory microbial products and metabolites. The relationship between these pathways is incompletely understood, in particular the significance of the tumor microbiota with respect to the identification of host and/or microbial products that regulate the egress of bacteria and immunocytes toward tumor beds.

Integrating functional metagenomics to decipher microbiome-immune interactions

Microbial metabolites can be viewed as the cytokines of the microbiome, transmitting information about the microbial and metabolic environment of the gut to orchestrate and modulate local and systemic immune responses. Still, many immunology studies focus solely on the taxonomy and community structure of the gut microbiota rather than its functions. Early sequencing-based microbiota profiling approaches relied on PCR amplification of small regions of bacterial and fungal genomes to facilitate identification of the microbes present. However, recent microbiome analysis methods, particularly shotgun metagenomic sequencing, now enable culture-independent profiling of microbiome functions and metabolites in addition to taxonomic characterization. In this review, we showcase recent advances in functional metagenomics methods and applications and discuss the current limitations and potential avenues for future development. Importantly, we highlight a few examples of key areas of opportunity in immunology research where integrating functional metagenomic analyses of the microbiome can substantially enhance a mechanistic understanding of microbiome-immune interactions and their contributions to health and disease states.

Host-Gut Microbiota Metabolic Interactions and Their Role in Precision Diagnosis and Treatment of Gastrointestinal Cancers

The critical role of the gut microbiome in gastrointestinal cancers is becoming increasingly clear. Imbalances in the gut microbial community, referred to as dysbiosis, are linked to increased risks for various forms of gastrointestinal cancers. Pathogens like Fusobacterium and Helicobacter pylori relate to the onset of esophageal and gastric cancers, respectively, while microbes such as Porphyromonas gingivalis and Clostridium species have been associated with a higher risk of pancreatic cancer. In colorectal cancer, bacteria such as Fusobacterium nucleatum are known to stimulate the growth of tumor cells and trigger cancer-promoting pathways. On the other hand, beneficial microbes like Bifidobacteria offer a protective effect, potentially inhibiting the development of gastrointestinal cancers. The potential for therapeutic interventions that manipulate the gut microbiome is substantial, including strategies to engineer anti-tumor metabolites and employ microbiota-based treatments. Despite the progress in understanding the influence of the microbiome on gastrointestinal cancers, significant challenges remain in identifying and understanding the precise contributions of specific microbial species and their metabolic products. This knowledge is essential for leveraging the role of the gut microbiome in the development of precise diagnostics and targeted therapies for gastrointestinal cancers.