The interplay between neutrophils and microbiota in cancer

Novel immunotherapeutic approaches in gastric cancer

Gastric cancer is a malignant tumor that ranks third in cancer-related deaths worldwide. Early-stage gastric cancer can often be effectively managed through surgical resection. However, the majority of cases are diagnosed in advanced stages, where outcomes with conventional radiotherapy and chemotherapy remain unsatisfactory. Immunotherapy offers a novel approach to treating molecularly heterogeneous gastric cancer by modifying the immunosuppressive tumor microenvironment. Immune checkpoint inhibitors and adoptive cell therapy are regarded as promising modalities in cancer immunotherapy. Food and Drug Administration-approved programmed death-receptor inhibitors, such as pembrolizumab, in combination with chemotherapy, have significantly extended overall survival in gastric cancer patients and is recommended as a first-line treatment. Despite challenges in solid tumor applications, adoptive cell therapy has demonstrated efficacy against various targets in gastric cancer treatment. Among these approaches, chimeric antigen receptor-T cell therapy research is the most widely explored and chimeric antigen receptor-T cell therapy targeting claudin18.2 has shown acceptable safety and robust anti-tumor capabilities. However, these advancements primarily remain in preclinical stages and further investigation should be made to promote their clinical application. This review summarizes the latest research on immune checkpoint inhibitors and adoptive cell therapy and their limitations, as well as the role of nanoparticles in enhancing immunotherapy.

Fusobacterium Nucleatum Aggravates Intestinal Barrier Impairment and Colitis Through IL-8 Induced Neutrophil Chemotaxis by Activating Epithelial Cells

Background

Inflammatory bowel disease (IBD) is affected by interactions between intestinal microbial factors, abnormal inflammation, and an impaired intestinal mucosal barrier. Neutrophils (NE) are key players in IBD. Fusobacterium nucleatum (F. nucleatum) is reported to contribute to IBD progression. However, the relationship between F. nucleatum, abnormal inflammation, and intestinal barrier impairment should be interpreted to understand the role of F. nucleatum in IBD.

Methods

Dextran sulfate sodium (DSS)-induced colitis model was established and mice were orally administered with F. nucleatum. F. nucleatum colonization was confirmed by fluorescence in situ hybridization (FISH) and PCR. Intestinal barrier impairment was investigated by tight junction protein expression. Immuno-histochemistry (IHC) for Ly6G and flow cytometry detection to measure NE chemotaxis in mouse colon tissues. Caco-2 monolayers were used to evaluate epithelial integrity and permeability in vitro. A transwell model involving caco-2 cells and NE co-culture was used to assess NE chemotaxis. NE chemokines were measured by ELISA. A mouse model of NE exhaustion using an anti-Ly6G antibody was used to identify the role of NEs in F. nucleatum-induced colitis. Transcriptome sequencing and bioinformatics analysis were applied to screen cytokines and signaling pathways.

Results

Administration of F. nucleatum aggravated colitis in the DSS model. F. nucleatum infection downregulates ZO-1 and Occludin expression and increases intestinal permeability. Additionally, F. nucleatum-induced NE chemotaxis decreases the integrity and permeability of the caco-2 monolayer. F. nucleatum-induced NE chemotaxis is dependent on IEC-derived interleukin 8 (IL-8) secretion, mediated by the TLR2/ERK signaling pathway. In addition, NE exhaustion in mice inhibited F. nucleatum-induced intestinal barrier impairment and colitis.

Conclusion

F. nucleatum improves NE chemotaxis by infecting intestinal epithelial cells (IECs) to secrete IL-8 and aggravate intestinal barrier impairment, contributing to the progression of intestinal inflammation. Examining and eliminating F. nucleatum could be a valuable microbiome-based method for IBD surveillance and prevention.

Role of neutrophils in the pathogenesis of Post Kala-azar Dermal Leishmaniasis (PKDL)

BACKGROUND

Post Kala-azar Dermal Leishmaniasis (PKDL) is a dermal sequel of visceral leishmaniasis (VL), poses a significant threat to the success of ongoing kala-azar elimination program, due to its potential role in sustaining transmission cycles and complicating disease management strategies. In VL, neutrophils have been identified as the 'first line of defence', having multiple roles in disease pathogenesis, but their role in PKDL, if any, still remains elusive; presenting a critical gap in knowledge, and was the aim of this study.

METHODOLOGY/PRINCIPAL FINDINGS

In a cohort of PKDL patients, CD66b+ neutrophils were quantified in skin biopsies, followed by immunostaining of FFPE sections to identify activated neutrophils (CD66b+/CD64+) and degranulated (CD66b+/MPO+), along with expression of neutrophil elastase (NE), matrix metalloprotease 9 (MMP9) and collagen I. Plasma levels of neutrophil chemo-attractants CXCL8/1/2/5, CCL2 and 20 and cytokines, (IL-6, IFN-γ, IL-4, IL-10, TNF-α, IL-17 and IL-22, 23) were evaluated by a multiplex assay, while lesional expression of IL-8, IL-10 and IL-17 was evaluated by immunohistochemistry. As compared to healthy individuals (control skin samples), PKDL cases at the lesional sites had an increased number of activated CD66b+ neutrophils (positive for CD64+, MPO+ and NE+). The plasma levels of neutrophil chemo-attractants, pro-inflammatory and regulatory cytokines were raised as was circulating and lesional IL-8, along with an enhanced lesional expression of IL-10 and IL-17A. An increase in circulatory and lesional MMP9 was accompanied by decreased collagen I, suggesting disintegration of matrix integrity.

CONCLUSIONS/SIGNIFICANCE

Taken together, in PKDL, activated neutrophils possibly contribute towards modulating the lesional landscape. Understanding this involvement of neutrophils in patients with PKDL, particularly in the absence of an animal model, could offer better understanding of the disease pathogenesis and provide insights into novel therapeutic strategies for the ongoing elimination program.

Staphylococcus aureus lipid factors modulate melanoma cell clustering and invasion

The microbiome can influence cancer development and progression. However, less is known about the role of the skin microbiota in melanoma. Here, we took advantage of a zebrafish melanoma model to probe the effects of Staphylococcus aureus on melanoma invasion. We found that S. aureus produces factors that enhance melanoma invasion and dissemination in zebrafish larvae. We used a published in vitro 3D cluster formation assay that correlates increased clustering with tumor invasion. S. aureus supernatant increased clustering of melanoma cells and was abrogated by a Rho-Kinase inhibitor, implicating a role for Rho-GTPases. The melanoma clustering response was specific to S. aureus but not to other staphylococcal species, including S. epidermidis. Our findings suggest that S. aureus promotes melanoma clustering and invasion via lipids generated by the lipase Sal2 (officially known as GehB). Taken together, these findings suggest that specific bacterial products mediate melanoma invasive migration in zebrafish.

The role and mechanism of action of microbiota-derived short-chain fatty acids in neutrophils: From the activation to becoming potential biomarkers

Short-chain fatty acids (SCFAs), such as acetate, propionate, and butyrate, have emerged as critical mediators in the communication between the human microbiota and its host. As the first responder to the inflammatory site, neutrophils play an important role in protecting the host against bacterial infections. Recent investigations revealed that SCFAs generated from microbiota influence various neutrophil activities, including activation, migration, and generation of mediators of inflammatory processes. SCFAs have also been demonstrated to exhibit potential therapeutic benefits in a variety of disorders related to neutrophil dysfunction, including inflammatory bowel disease, viral infectious disorders, and cancer. This study aims to examine the molecular processes behind the complicated link between SCFAs and neutrophils, as well as their influence on neutrophil-driven inflammatory disorders. In addition, we will also provide an in-depth review of current research on the diagnostic and therapeutic value of SCFAs as possible biomarkers for neutrophil-related diseases.

Circulating Low Density Neutrophils Are Associated with Resistance to First Line Anti-PD1/PDL1 Immunotherapy in Non-Small Cell Lung Cancer

Simple Summary

Immunotherapy has been positioned as frontline therapy for advanced non-small cell lung cancer (NSCLC), alone when PD-L1 tumor expression is high, or combined with chemotherapy otherwise. However, 50% of the patients do not respond to the treatment and the mechanisms of resistance are not well defined. Moreover, it is not clear whether chemo-immunotherapy could be advantageous in high PD-L1 tumor expression. We have found that baseline circulating low-density neutrophils (LDN) identify a subset of patients intrinsically refractory to immunotherapy. Interestingly, responses can be achieved with CT+IT, detecting a progressive depletion of LDN. Besides the potential role as predictive biomarker we observed that resistance was mediated by soluble molecules related with the HGF/c-MET pathway. Our findings establish circulating myeloid cells as one of the main mediators of resistance to immunotherapy in NSCLC, and give a rationale for potential drug combinations that might improve the outcomes.

Abstract

Single-agent immunotherapy has been widely accepted as frontline treatment for advanced non-small cell lung cancer (NSCLC) with high tumor PD-L1 expression, but most patients do not respond and the mechanisms of resistance are not well known. Several works have highlighted the immunosuppressive activities of myeloid subpopulations, including low-density neutrophils (LDNs), although the context in which these cells play their role is not well defined. We prospectively monitored LDNs in peripheral blood from patients with NSCLC treated with anti-PD-1 immune checkpoint inhibitors (ICIs) as frontline therapy, in a cohort of patients treated with anti-PD1 immunotherapy combined with chemotherapy (CT+IT), and correlated values with outcomes. We explored the underlying mechanisms through ex vivo experiments. Elevated baseline LDNs predict primary resistance to ICI monotherapy in patients with NSCLC, and are not associated with response to CT+IT. Circulating LDNs mediate resistance in NSCLC receiving ICI as frontline therapy through humoral immunosuppression. A depletion of this population with CT+IT might overcome resistance, suggesting that patients with high PD-L1 tumor expression and high baseline LDNs might benefit from this combination. The activation of the HGF/c-MET pathway in patients with elevated LDNs revealed by quantitative proteomics supports potential drug combinations targeting this pathway.

It Takes Two to Tango: A Review of Oncogenic Virus and Host Microbiome Associated Inflammation in Head and Neck Cancer

Simple Summary

Certain viruses, specifically, human papillomavirus (HPV) and Epstein–Barr virus (EBV), have been linked with the development of head and neck cancer. In this study, we review the mechanisms by which (these) viruses lead to cellular transformation and a chronic inflammatory state. Given that the head and neck host a rich microbiome (which itself is intrinsically linked to inflammation), we scrutinize the literature to highlight the interplay between viruses, cellular transformation, inflammation, and the local host microbiome in head and neck cancer.

Abstract

While the two primary risk factors for head and neck squamous cell carcinoma (HNSCC) are alcohol and tobacco, viruses account for an important and significant upward trend in HNSCC incidence. Human papillomavirus (HPV) is the causative agent for a subset of oropharyngeal squamous cell carcinoma (OPSCC)—a cancer that is impacting a rapidly growing group of typically middle-aged non-smoking white males. While HPV is a ubiquitously present (with about 1% of the population having high-risk oral HPV infection at any one time), less than 1% of those infected with high-risk strains develop OPSCC—suggesting that additional cofactors or coinfections may be required. Epstein–Barr virus (EBV) is a similarly ubiquitous virus that is strongly linked to nasopharyngeal carcinoma (NPC). Both of these viruses cause cellular transformation and chronic inflammation. While dysbiosis of the human microbiome has been associated with similar chronic inflammation and the pathogenesis of mucosal diseases (including OPSCC and NPC), a significant knowledge gap remains in understanding the role of bacterial-viral interactions in the initiation, development, and progression of head and neck cancers. In this review, we utilize the known associations of HPV with OPSCC and EBV with NPC to investigate these interactions. We thoroughly review the literature and highlight how perturbations of the pharyngeal microbiome may impact host-microbiome-tumor-viral interactions—leading to tumor growth.

Nucleic Acid Vaccines for COVID-19: A Paradigm Shift in the Vaccine Development Arena

Coronavirus disease, COVID-19, has touched every country globally except five countries (North Korea, Turkmenistan, Tonga, Tuvalu and Nauru). Vaccination is the most effective method to protect against infectious diseases. The objective is to ensure that everyone has access to a COVID-19 vaccine. The conventional vaccine development platforms are complex and time-consuming to obtain desired approved vaccine candidates through rigorous regulatory pathways. These safeguards guarantee that the optimized vaccine product is safe and efficacious for various demographic populations prior to it being approved for general use. Nucleic acid vaccines employ genetic material from a pathogen, such as a virus or bacteria, to induce an immune response against it. Based on the vaccination, the genetic material might be DNA or RNA; as such, it offers instructions for producing a specific pathogen protein that the immune system will perceive as foreign and mount an immune response. Nucleic acid vaccines for multiple antigens might be made in the same facility, lowering costs even more. Most traditional vaccine regimens do not allow for this. Herein, we demonstrate the recent understanding and advances in nucleic acid vaccines (DNA and mRNA based) against COVID-19, specifically those in human clinical trials.

The Gut Microbiome, Metformin, and Aging

Metformin has been extensively used for the treatment of type 2 diabetes, and it may also promote healthy aging. Despite its widespread use and versatility, metformin's mechanisms of action remain elusive. The gut typically harbors thousands of bacterial species, and as the concentration of metformin is much higher in the gut as compared to plasma, it is plausible that microbiome-drug-host interactions may influence the functions of metformin. Detrimental perturbations in the aging gut microbiome lead to the activation of the innate immune response concomitant with chronic low-grade inflammation. With the effectiveness of metformin in diabetes and antiaging varying among individuals, there is reason to believe that the gut microbiome plays a role in the efficacy of metformin. Metformin has been implicated in the promotion and maintenance of a healthy gut microbiome and reduces many age-related degenerative pathologies. Mechanistic understanding of metformin in the promotion of a healthy gut microbiome and aging will require a systems-level approach. Expected final online publication date for the Annual Review of Pharmacology and Toxicology, Volume 62 is January 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

COVID-19: immunopathogenesis and Immunotherapeutics

The recent novel coronavirus disease (COVID-19) outbreak, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is seeing a rapid increase in infected patients worldwide. The host immune response to SARS-CoV-2 appears to play a critical role in disease pathogenesis and clinical manifestations. SARS-CoV-2 not only activates antiviral immune responses, but can also cause uncontrolled inflammatory responses characterized by marked pro-inflammatory cytokine release in patients with severe COVID-19, leading to lymphopenia, lymphocyte dysfunction, and granulocyte and monocyte abnormalities. These SARS-CoV-2-induced immune abnormalities may lead to infections by microorganisms, septic shock, and severe multiple organ dysfunction. Therefore, mechanisms underlying immune abnormalities in patients with COVID-19 must be elucidated to guide clinical management of the disease. Moreover, rational management of the immune responses to SARS-CoV-2, which includes enhancing anti-viral immunity while inhibiting systemic inflammation, may be key to successful treatment. In this review, we discuss the immunopathology of COVID-19, its potential mechanisms, and clinical implications to aid the development of new therapeutic strategies against COVID-19.

Interleukin-35 as an Emerging Player in Tumor Microenvironment

IL-35 is the newest member of IL-12 family. A dimeric protein consisting of two separate subunits has manifested suppressive actions on immune system, which is counterproductive in the context of cancers. Various reports have confirmed its inhibitory role on immune system which is carried out via formation of IL-35-producing regulatory T cells (iTr35), increased Treg development and suppressive Th17 cells growth. Although last decade has seen a great deal of scientific interest on this subject, the exact role, precise signal transduction and elaborative functions of IL-35 in tumor microenvironment (TME) remained elusive. Search for anti-IL-35 therapies have exhibited limited success in animal models. Contrarily, few studies have denied the idea that IL-35 plays a role in cancer. The purpose of this review is to analyze the reported scientific data on continuous symphony of IL-35 in cancers since the inception of former.