Evaluation of antibody level against Fusobacterium nucleatum in the serological diagnosis of colorectal cancer

A rapid and sensitive CRISPR-Cas12a for the detection of Fusobacterium nucleatum

Fusobacterium nucleatum (Fn), as a conditional pathogen, can cause a range of oral and gastrointestinal diseases. However, existing clinical detection methods require expensive equipment and complex procedures, which are inconvenient for large-scale screening in epidemiological research. The purpose of this study was to establish a reliable, rapid, and inexpensive detection method based on CRISPR/Cas12a technology for the detection of Fn. Specific recombinase polymerase amplification (RPA) primer sequences and crRNA sequences were designed based on the nusG gene of Fn. Subsequently, a fluorescence assay and a lateral flow immunoassay were established using the RPA and CRISPR-Cas12a system (RPA-CRISPR-Cas12a). Sensitivity validation revealed a limit of detection of 5 copies/µL. This method could distinguish Fn from other pathogens with excellent specificity. Furthermore, the RPA-CRISPR-Cas12a assay was highly consistent with the classical quantitative real-time PCR method when testing periodontal pocket samples. This makes it a promising method for the detection of Fn and has the potential to play an increasingly important role in infectious disease testing.IMPORTANCEFusobacterium nucleatum (Fn) naturally exists in the microbial communities of the oral and gastrointestinal tracts of healthy individuals and can cause inflammatory diseases in the oral and gastrointestinal tracts. Recent studies have shown that Fn is closely associated with the occurrence and development of gastrointestinal cancer. Therefore, the detection of Fn is very important. Unlike the existing clinical detection methods, this study established a fluorescence-based assay and lateral flow immunoassay based on the RPA and CRISPR-Cas12a system (RPA-CRISPR-Cas12a), which is fast, reliable, and inexpensive and can complete the detection within 30-40 minutes. This makes it a promising method for the detection of Fn and has the potential to play an increasingly important role in infectious disease testing.

The Role of Fusobacterium nucleatum in Oral and Colorectal Carcinogenesis

In recent years, several studies have suggested a strong association of microorganisms with several human cancers. Two periodontopathogenic species in particular have been mentioned frequently: Fusobacterium nucleatum (F. nucleatum) and Porphyromonas gingivalis. Chronic periodontal disease has been reported to be a risk factor for oral squamous cell carcinoma (OSCC), colorectal cancer (CRC) and pancreatic cancer. F. nucleatum is a Gram-negative anaerobic bacterium that lives in the oral cavity, urogenital, intestinal and upper digestive tract. It plays a significant role as a co-aggregation factor, with almost all bacterial species that participate in oral plaque formation acting as a bridge between early and late colonizers. F. nucleatum, gives an important inflammatory contribution to tumorigenesis progression and is associated with epithelial-derived malignancies, such as OSCC and CRC. F. nucleatum produces an adhesion protein, FadA, which binds to VE-cadherin on endothelial cells and to E-cadherins on epithelial cells. The last binding activates oncogenic pathways, such as Wnt/βcatenin, in oral and colorectal carcinogenesis. F. nucleatum also affects immune response because its Fap2 protein interacts with an immune receptor named TIGIT present on some T cells and natural killer cells inhibiting immune cells activities. Morover, F. nucleatum release outer membrane vesicles (OMVs), which induce the production of proinflammatory cytokines and initiating inflammation. F. nucleatum migrates from the oral cavity and reaches the colon hematogenously but it is not known if in the bloodstream it reaches the CRC as free, erythrocyte-bound bacteria or in OMV. F. nucleatum abundance in CRC tissue has been inversely correlated with overall survival (OS). The prevention and treatment of periodontal disease through the improvement of oral hygiene should be included in cancer prevention protocols. FadA virulence factors may also serve as novel targets for therapeutic intervention of oral and colorectal cancer.

Association of Antibody Responses to Fusobacterium nucleatum and Streptococcus gallolyticus Proteins with Colorectal Adenoma and Colorectal Cancer

BACKGROUND

Streptococcus gallolyticus subspecies gallolyticus (SGG) and Fusobacterium (F.) nucleatum have been implicated in colorectal carcinogenesis. Here, the association of immune responses to bacterial exposure with advancing stages of colorectal neoplasia was assessed by multiplex serology.

METHODS

Immunoglobulin (Ig) A and G antibody responses to eleven proteins each of F. nucleatum and SGG were measured in plasma of controls (n = 100) and patients with colorectal cancer (CRC, n = 25), advanced adenoma (n = 82), or small polyps (n = 85). Multivariable logistic regression was used to evaluate the association of bacterial sero-positivity with colorectal neoplasia. In a cohort subset with matched data (n = 45), F. nucleatum sero-positivity was correlated with bacterial abundance in both neoplastic and matched normal tissue.

RESULTS

IgG sero-positivity to Fn1426 of F. nucleatum was associated with an increased CRC risk (OR = 4.84; 95% CI 1.46-16.0), while IgA sero-positivity to any SGG protein or specifically Gallo0272 and Gallo1675 alone was associated with increased advanced adenoma occurrence (OR = 2.02, 95% CI 1.10-3.71; OR = 2.67, 95% CI 1.10-6.46; and OR = 6.17, 95% CI 1.61-23.5, respectively). Only F. nucleatum abundance in the normal mucosa positively correlated with the IgA response to the Fn1426 antigen (Correlation coefficient (r) = 0.38, p < 0.01).

CONCLUSION

Antibody responses to SGG and F. nucleatum were associated with occurrence of colorectal adenomas and CRC, respectively. Further studies are needed to clarify the role these microbes or the immune response to their antigens may have in colorectal carcinogenesis stages.

Fusobacterium nucleatum, a key pathogenic factor and microbial biomarker for colorectal cancer

Colorectal cancer (CRC), one of the most prevalent cancers, has complex etiology. The dysbiosis of intestinal bacteria has been highlighted as an important contributor to CRC. Fusobacterium nucleatum, an oral anaerobic opportunistic pathogen, is enriched in both stools and tumor tissues of patients with CRC. Therefore, F. nucleatum is considered to be a risk factor for CRC. This review summarizes the biological characteristics and the mechanisms underlying the regulatory behavior of F. nucleatum in the tumorigenesis and progression of CRC. F. nucleatum as a marker for the early warning and prognostic prediction of CRC, and as a target for prevention and treatment, is also described.

Gut Microbiota in Colorectal Cancer: Biological Role and Therapeutic Opportunities

Colorectal cancer (CRC) is the second-leading cause of cancer-related deaths worldwide. While CRC is thought to be an interplay between genetic and environmental factors, several lines of evidence suggest the involvement of gut microbiota in promoting inflammation and tumor progression. Gut microbiota refer to the ~40 trillion microorganisms that inhabit the human gut. Advances in next-generation sequencing technologies and metagenomics have provided new insights into the gut microbial ecology and have helped in linking gut microbiota to CRC. Many studies carried out in humans and animal models have emphasized the role of certain gut bacteria, such as Fusobacterium nucleatum, enterotoxigenic Bacteroides fragilis, and colibactin-producing Escherichia coli, in the onset and progression of CRC. Metagenomic studies have opened up new avenues for the application of gut microbiota in the diagnosis, prevention, and treatment of CRC. This review article summarizes the role of gut microbiota in CRC development and its use as a biomarker to predict the disease and its potential therapeutic applications.

Fusobacterium nucleatum and its associated systemic diseases: epidemiologic studies and possible mechanisms

Background

Fusobacterium nucleatum (F. nucleatum) is an anaerobic oral commensal and the major coaggregation bridge organism linking early and late colonisers. In recent years, a large number of studies suggest that F. nucleatum is closely related to the development of various systemic diseases, such as cardiovascular diseases, adverse pregnancy outcomes, inflammatory bowel diseases, cancer, Alzheimer's disease, respiratory infection, rheumatoid arthritis, etc.

Objective

To review the effect of F. nucleatum on systemic diseases and its possible pathogenesis and to open new avenues for prevention and treatment of F. nucleatum-associated systemic diseases.

Design

The research included every article published up to July 2022 featuring the keywords 'Systemic diseases' OR 'Atherosclerotic cardiovascular diseases' OR 'Atherosclerosis' OR 'Adverse pregnancy outcomes' OR 'Inflammatory bowel disease' OR 'Ulcerative colitis' OR 'Crohn’s disease' OR 'Cancers' OR 'Oral squamous cell carcinomas' OR 'Gastrointestinal cancers' OR 'Colorectal cancer' OR 'Breast cancer' OR 'Genitourinary cancers' OR 'Alzheimer’s disease ' OR 'Rheumatoid arthritis' OR 'Respiratory diseases' AND 'Fusobacterium nucleatum' OR 'Periodontal pathogen' OR 'Oral microbiota' OR 'Porphyromonas gingivalis' and was conducted in the major medical databases.

Results

F. nucleatum can induce immune response and inflammation in the body through direct or indirect pathways, and thus affect the occurrence and development of systemic diseases. Only by continuing to investigate the pathogenic lifestyles of F. nucleatum will we discover the divergent pathways that may be leveraged for diagnostic, preventive and therapeutic purposes.

The global research of microbiota in colorectal cancer screening: a bibliometric and visualization analysis

Aims

We conducted bibliometric and visualization analyses to evaluate the current research status, hotspots, and trends related to the human microbiota markers in colorectal cancer screening.

Methods

The related studies were acquired from the Web of Science Core Collection (WoSCC) database on 5 January 2023. Analyses of the co-occurrence and cooperation relationships between the cited authors, institutions, countries/regions, cited journals, cited articles, and keywords in the studies were carried out using CiteSpace 5.8.R3 software and the Online Analysis platform of Literature Metrology. Additionally, relevant knowledge graphs were drawn to perform visualization analyses; a keywords cluster analysis and a burst analysis were also conducted.

Results

After analyzing 700 relevant articles, this bibliometric analysis found that the annual publications showed an increasing trend from 1992 to 2022. Yu Jun from the Chinese University of Hong Kong had the highest cumulative number of publications, whereas Shanghai Jiao Tong University was the most productive institution. China and the USA have contributed the largest number of studies. The keywords frequency analysis demonstrated that "colorectal cancer," "gut microbiota," "Fusobacterium nucleatum," "risk," and "microbiota" were the most frequent keywords, and the keywords cluster analysis found that the current hotspots were as follows: (a) the precancerous lesions of colorectal cancer (CRC) that need to be screened, such as inflammatory bowel disease (IBD) and advanced adenoma, (b) the gut-derived microbiome for CRC screening, and (c) the early detection of CRC. The burst analysis further showed that the combination of microbiomics with metabolomics might be the future research trend in the field of CRC screening.

Conclusion

The findings of the current bibliometric analysis firstly provide an insight into the current research status, hotspots, and future trends in the field of CRC screening based on the microbiome; the research in this field is becoming more in-depth and diversified. Some human microbiota markers, especially "Fusobacterium nucleatum," are promising biomarkers in CRC screening, and a future hotspot might be the combined analysis of microbiomics and metabolomics for CRC risk screening.

Colorectal cancer and gut microbiota studies in China

Colorectal cancer (CRC) is the third most common malignant tumor worldwide. The incidence and mortality rates of CRC have been increasing in China, possibly due to economic development, lifestyle, and dietary changes. Evidence suggests that gut microbiota plays an essential role in the tumorigenesis of CRC. Gut dysbiosis, specific pathogenic microbes, metabolites, virulence factors, and microbial carcinogenic mechanisms contribute to the initiation and progression of CRC. Gut microbiota biomarkers have potential translational applications in CRC screening and early diagnosis. Gut microbiota-related interventions could improve anti-tumor therapy's efficacy and severe intestinal toxic effects. Chinese researchers have made many achievements in the relationship between gut microbiota and CRC, although some challenges remain. This review summarizes the current evidence from China on the role of gut microbiota in CRC, mainly including the gut microbiota characteristics, especially Fusobacterium nucleatum and Parvimonas micra, which have been identified to be enriched in CRC patients; microbial pathogens such as F. nucleatum and enterotoxigenic Bacteroides fragilis, and P. micra, which Chinese scientists have extensively studied; diagnostic biomarkers especially F. nucleatum; therapeutic effects, including microecological agents represented by certain Lactobacillus strains, fecal microbiota transplantation, and traditional Chinese medicines such as Berberine and Curcumin. More efforts should be focused on exploring the underlying mechanisms of microbial pathogenesis of CRC and providing novel gut microbiota-related therapeutic and preventive strategies.

Evaluating the predictive performance of gut microbiota for the early-stage colorectal cancer

BACKGROUND

Colorectal cancer (CRC) has been regarded as one of the most frequently diagnosed malignancies among the leading causes of cancer-related morbidity and mortality globally. Diagnosis of CRC at the early-stages of tumour might improve the survival rate of patients. The current study sought to determine the performance of fecal Fusobacterium nucleatum (F. nucleatum) and Streptococcus bovis (S. bovis) for timely predicting CRC.

METHODS

Through a case-control study, the fecal sample information of 83 individuals (38 females, 45 males) referring to a hospital in Tehran, Iran was used. All patients underwent a complete colonoscopy, regarded as a gold standard test. Bacterial species including S. bovis and F. nucleatum were measured by absolute quantitative real-time PCR. The Bayesian univariate and bivariate latent class models (LCMs) were applied to estimate the ability of the candidate bacterial markers in order to early detection of patients with CRC.

RESULTS

Bayesian univariate LCMs demonstrated that the sensitivities of S. bovis and F. nucleatum were estimated to be 86% [95% credible interval (CrI) 0.82-0.91] and 82% (95% CrI 0.75-0.88); while specificities were 84% (95% CrI 0.78-0.89) and 80% (95% CrI 0.73-0.87), respectively. Moreover, the area under the receiver operating characteristic curves (AUCs) were 0.88 (95% CrI 0.83-0.94) and 0.80 (95% CrI 0.73-0.85) respectively for S. bovis and F. nucleatum. Based on the Bayesian bivariate LCMs, the sensitivities of S. bovis and F. nucleatum were calculated as 93% (95% CrI 0.84-0.98) and 90% (95% CrI 0.85-0.97), the specificities were 88% (95% CrI 0.78-0.93) and 87% (95% CrI 0.79-0.94); and the AUCs were 0.91 (95% CrI 0.83-0.99) and 0.88(95% CrI 0.81-0.96), respectively.

CONCLUSIONS

Our data has identified that according to the Bayesian bivariate LCM, S. bovis and F. nucleatum had a more significant predictive accuracy compared with the univariate model. In summary, these intestinal bacteria have been highlighted as novel tools for early-stage CRC diagnosis.

Understanding the cross-talk between human microbiota and gastrointestinal cancer for developing potential diagnostic and prognostic biomarkers

The interaction between gut microbes and gastrointestinal (GI) tract carcinogenesis has always attracted researchers' attention to identify therapeutic targets or potential prognostic biomarkers. Various studies have suggested that the microbiota do show inflammation and immune dysregulation, which led to carcinogenesis in GI tract. In this review, we have focused on the role of microbes present in the gut, intestine, or faeces in GI tract cancers, including esophageal cancer, gastric cancer, and colorectal cancer. Herein, we have discussed the importance of the microbes and their metabolites, which could serve as diagnostic biomarkers for cancer detection, especially in the early stage, and prognostic markers. To maximize the effect of the treatment strategies, an accurate evaluation of the prognosis is imperative for clinicians. There is a vast difference in the microbiota profiles within a population and across the populations depending upon age, diet, lifestyle, genetic makeup, use of antibiotics, and environmental factors. Therefore, the diagnostic efficiency of the microbial markers needs to be further validated. A deeper understanding of the GI cancer and the host microbiota is needed to acquire pivotal information about disease status.

Structural and Functional Analysis of the Pyridoxal Phosphate Homeostasis Protein YggS from Fusobacterium nucleatum

Pyridoxal 5′-phosphate (PLP) is the active form of vitamin B6, but it is highly reactive and poisonous in its free form. YggS is a PLP-binding protein found in bacteria and humans that mediates PLP homeostasis by delivering PLP to target enzymes or by performing a protective function. Several biochemical and structural studies of YggS have been reported, but the mechanism by which YggS recognizes PLP has not been fully elucidated. Here, we report a functional and structural analysis of YggS from Fusobacterium nucleatum (FnYggS). The PLP molecule could bind to native FnYggS, but no PLP binding was observed for selenomethionine (SeMet)-derivatized FnYggS. The crystal structure of FnYggS showed a type III TIM barrel fold, exhibiting structural homology with several other PLP-dependent enzymes. Although FnYggS exhibited low (<35%) amino acid sequence similarity with previously studied YggS proteins, its overall structure and PLP-binding site were highly conserved. In the PLP-binding site of FnYggS, the sulfate ion was coordinated by the conserved residues Ser201, Gly218, and Thr219, which were positioned to provide the binding moiety for the phosphate group of PLP. The mutagenesis study showed that the conserved Ser201 residue in FnYggS was the key residue for PLP binding. These results will expand the knowledge of the molecular properties and function of the YggS family.

Effect of gut microbiota in the colorectal cancer and potential target therapy

The symbiotic interaction between gut microbiota and the digestive tract is an important factor in maintaining the intestinal environment balance. Colorectal cancer (CRC) is a complex disease involving the interaction between tumour cells and a large number of microorganisms. The microbiota is involved in the occurrence, development and prognosis of colorectal cancer. Several microbiota species have been studied, such as Fusobacterium nucleatum (F. nucleatum), Enterotoxigenic Bacteroides fragilis (ETBF), Streptococcus bovis (S. bovis), Lactobacillus, and Bifidobacterium. Studies about the interaction between microbiota and CRC were retrieved from Embase, PubMed, Ovid and Web of Science up to 21 Oct 2021. This review expounded on the effect of microbiota on CRC, especially the dysregulation of bacteria and carcinogenicity. The methods of gut microbiota modifications representing novel prognostic markers and innovative therapeutic strategies were also described.

A systematic review of microbial markers for risk prediction of colorectal neoplasia

BACKGROUND

Substantial evidence indicates that dysbiosis of the gut microbial community is associated with colorectal neoplasia. This review aims to systematically summarise the microbial markers associated with colorectal neoplasia and to assess their predictive performance.

METHODS

A comprehensive literature search of MEDLINE and EMBASE databases was performed to identify eligible studies. Observational studies exploring the associations between microbial biomarkers and colorectal neoplasia were included. We also included prediction studies that constructed models using microbial markers to predict CRC and adenomas. Risk of bias for included observational and prediction studies was assessed.

RESULTS

Forty-five studies were included to assess the associations between microbial markers and colorectal neoplasia. Nine faecal microbiotas (i.e., Fusobacterium, Enterococcus, Porphyromonas, Salmonella, Pseudomonas, Peptostreptococcus, Actinomyces, Bifidobacterium and Roseburia), two oral pathogens (i.e., Treponema denticola and Prevotella intermedia) and serum antibody levels response to Streptococcus gallolyticus subspecies gallolyticus were found to be consistently associated with colorectal neoplasia. Thirty studies reported prediction models using microbial markers, and 83.3% of these models had acceptable-to-good discrimination (AUROC > 0.75). The results of predictive performance were promising, but most of the studies were limited to small number of cases (range: 9-485 cases) and lack of independent external validation (76.7%).

CONCLUSIONS

This review provides insight into the evidence supporting the association between different types of microbial species and their predictive value for colorectal neoplasia. Prediction models developed from case-control studies require further external validation in high-quality prospective studies. Further studies should assess the feasibility and impact of incorporating microbial biomarkers in CRC screening programme.

Dynamic liquid biopsy components as predictive and prognostic biomarkers in colorectal cancer

Colorectal cancer (CRC) is one of the most common cancers worldwide. The diagnosis, prognosis and therapeutic monitoring of CRC depends largely on tissue biopsy. However, due to tumor heterogeneity and limitations such as invasiveness, high cost and limited applicability in longitudinal monitoring, liquid biopsy has gathered immense attention in CRC. Liquid biopsy has several advantages over tissue biopsy including ease of sampling, effective monitoring, and longitudinal assessment of treatment dynamics. Furthermore, the importance of liquid biopsy is signified by approval of several liquid biopsy assays by regulatory bodies indicating the powerful approach of liquid biopsy for comprehensive CRC screening, diagnostic and prognostics. Several liquid biopsy biomarkers such as novel components of the microbiome, non-coding RNAs, extracellular vesicles and circulating tumor DNA are extensively being researched for their role in CRC management. Majority of these components have shown promising results on their clinical application in CRC including early detection, observe tumor heterogeneity for treatment and response, prediction of metastases and relapse and detection of minimal residual disease. Therefore, in this review, we aim to provide updated information on various novel liquid biopsy markers such as a) oral microbiota related bacterial network b) gut microbiome-associated serum metabolites c) PIWI-interacting RNAs (piRNAs), microRNA(miRNAs), Long non-coding RNAs (lncRNAs), circular RNAs (circRNAs) and d) circulating tumor DNAs (ctDNA) and circulating tumor cells (CTC) for their role in disease diagnosis, prognosis, treatment monitoring and their applicability for personalized management of CRC.

Roles of gut microbiota in colorectal carcinogenesis providing a perspective for early diagnosis and treatment

Colorectal cancer (CRC) is the third most prevalent malignant neoplasm in the world. CRC is influenced by both environmental and genetic factors. Through toxin-mediated DNA damage and promotion of persistent dysregulated inflammation, the gut microbiota plays a crucial role in the development of CRC. In this review, we discussed the correlation between the bacterial microbiota and CRC carcinogenesis as well as the mechanism by which Streptococcus bovis/gallolyticus, Fusobacterium nucleatum, Bacteroides fragilis, and Escherichia coli can cause CRC.

Fusobacterium nucleatum and cancer

Accumulating evidence demonstrates that the oral pathobiont Fusobacterium nucleatum is involved in the progression of an increasing number of tumors types. Thus far, the mechanisms underlying tumor exacerbation by F. nucleatum include the enhancement of proliferation, establishment of a tumor‐promoting immune environment, induction of chemoresistance, and the activation of immune checkpoints. This review focuses on the mechanisms that mediate tumor‐specific colonization by fusobacteria. Elucidating the mechanisms mediating fusobacterial tumor tropism and promotion might provide new insights for the development of novel approaches for tumor detection and treatment.

Blood Bacterial DNA Load and Profiling Differ in Colorectal Cancer Patients Compared to Tumor-Free Controls

Simple Summary

In colorectal cancer patients, epithelial barrier dysfunction can lead to increased intestinal permeability, and gut microbiome was found to vary compared to healthy subjects. We conducted a study to investigate whether bacterial translocation from gastrointestinal tract to bloodstream is associated to intestinal adenoma and/or colorectal cancer. In particular, an epidemiological and metagenomic approach was used to evaluate the relation of the bacterial DNA load and the bacterial taxonomic groups—assessed by 16S rRNA profiling—in blood with the risks of intestinal adenoma and colorectal cancer. These findings can confirm the presence of bacterial DNA in blood in healthy adults and serve as a basis to evaluate new non-invasive techniques for an early CRC diagnosis through the analyses of bacterial DNA circulating in peripheral blood.

Abstract

Inflammation and immunity are linked to intestinal adenoma (IA) and colorectal cancer (CRC) development. The gut microbiota is associated with CRC risk. Epithelial barrier dysfunction can occur, possibly leading to increased intestinal permeability in CRC patients. We conducted a case-control study including 100 incident histologically confirmed CRC cases, and 100 IA and 100 healthy subjects, matched to cases by center, sex and age. We performed 16S rRNA gene analysis of blood and applied conditional logistic regression. Further analyses were based on negative binomial distribution normalization and Random Forest algorithm. We found an overrepresentation of blood 16S rRNA gene copies in colon cancer as compared to tumor-free controls. For high levels of gene copies, community diversity was higher in colon cancer cases than controls. Bacterial taxa and operational taxonomic unit abundances were different between groups and were able to predict CRC with an accuracy of 0.70. Our data support the hypothesis of a higher passage of bacteria from gastrointestinal tract to bloodstream in colon cancer. This result can be applied on non-invasive diagnostic tests for colon cancer control.

Bacterial and Parasitic Pathogens as Risk Factors for Cancers in the Gastrointestinal Tract: A Review of Current Epidemiological Knowledge

The oncogenic potential of viral infections is well established and documented for many years already. However, the contribution of (commensal) bacteria and parasites to the development and progression of cancers has only recently gained momentum, resulting in a rapid growth of publications on the topic. Indeed, various bacteria and parasites have been suggested to play a role in the development of gastrointestinal cancer in particular. Therefore, an overview of the current epidemiological knowledge on the association between infections with bacteria and parasites and cancers of the gastrointestinal tract is needed. In this review, we summarized the methodological characteristics and main results of epidemiological studies investigating the association of 10 different bacteria (Bacteroides fragilis, Campylobacter spp., Clostridium spp., Enterococcus faecalis, Escherichia coli, Fusobacterium nucleatum, Porphyromonas gingivalis, non-typhoidal Salmonella, Salmonella Typhi, and Streptococcus spp.) and three parasites (Cryptosporidium spp., Schistosoma spp., and Strongyloides stercoralis) with gastrointestinal cancer. While the large body of studies based on microbiome sequencing provides valuable insights into the relative abundance of different bacterial taxa in cancer patients as compared to individuals with pre-malignant conditions or healthy controls, more research is needed to fulfill Koch's postulates, possibly making use of follow-up data, to assess the complex role of bacterial and parasitic infections in cancer epidemiology. Studies incorporating follow-up time between detection of the bacterium or parasite and cancer diagnosis remain valuable as these allow for estimation of cause-effect relationships.

Personalized Immunotherapy in Colorectal Cancers: Where Do We Stand?

Colorectal cancer (CRC) is the second leading cause of cancer death in the world. Immunotherapy using monoclonal antibodies, immune-checkpoint inhibitors, adoptive cell therapy, and cancer vaccines has raised great hopes for treating poor prognosis metastatic CRCs that are resistant to the conventional therapies. However, high inter-tumor and intra-tumor heterogeneity hinder the success of immunotherapy in CRC. Patients with a similar tumor phenotype respond differently to the same immunotherapy regimen. Mutation-based classification, molecular subtyping, and immunoscoring of CRCs facilitated the multi-aspect grouping of CRC patients and improved immunotherapy. Personalized immunotherapy using tumor-specific neoantigens provides the opportunity to consider each patient as an independent group deserving of individualized immunotherapy. In the recent decade, the development of sequencing and multi-omics techniques has helped us classify patients more precisely. The expansion of such advanced techniques along with the neoantigen-based immunotherapy could herald a new era in treating heterogeneous tumors such as CRC. In this review article, we provided the latest findings in immunotherapy of CRC. We elaborated on the heterogeneity of CRC patients as a bottleneck of CRC immunotherapy and reviewed the latest advances in personalized immunotherapy to overcome CRC heterogeneity.

Prospects and Challenges of the Study of Anti-Glycan Antibodies and Microbiota for the Monitoring of Gastrointestinal Cancer

Over the past decades, a large amount of data has been accumulated in various subfields of glycobiology. However, much clinically relevant data and many tools are still not widely used in medicine. Synthetic glycoconjugates with the known structure of glycans are an accurate tool for the study of glycan-binding proteins. We used polyacrylamide glycoconjugates (PGs) including PGs with tumour-associated glycans (TAGs) in immunoassays to assess the prognostic potential of the serum level of anti-glycan antibodies (AG Abs) in gastrointestinal cancer patients and found an association of AG Abs with survival. The specificity of affinity-isolated AG Abs was investigated using synthetic and natural glycoconjugates. AG Abs showed mainly a low specificity to tumour-associated and tumour-derived mucins; therefore, the protective role of the examined circulating AG Abs against cancer remains a challenge. In this review, our findings are analysed and discussed in the context of the contribution of bacteria to the AG Abs stimulus and cancer progression. Examples of the influence of pathogenic bacteria colonising tumours on cancer progression and patient survival through mechanisms of interaction with tumours and dysregulated immune response are considered. The possibilities and problems of the integrative study of AG Abs and the microbiome using high-performance technologies are discussed.

Modulation of the Host Cell Transcriptome and Epigenome by Fusobacterium nucleatum

Fusobacterium nucleatum is a ubiquitous opportunistic pathogen with an emerging role as an oncomicrobe in colorectal cancer and other cancer settings. F. nucleatum can adhere to and invade host cells in a manner that varies across F. nucleatum strains and host cell phenotypes. Here, we performed pairwise cocultures between three F. nucleatum strains and two immortalized primary host cell types (human colonic epithelial [HCE] cells and human carotid artery endothelial [HCAE] cells) followed by transcriptome sequencing (RNA-seq) and chromatin immunoprecipitation sequencing (ChIP-seq) to investigate transcriptional and epigenetic host cell responses. We observed that F. nucleatum-induced host cell transcriptional modulation involves strong upregulation of genes related to immune migration and inflammatory processes, such as TNF, CXCL8, CXCL1, and CCL20. Furthermore, we identified genes strongly upregulated in a cell line-specific manner. In HCE cells, overexpressed genes included UBD and DUOX2/DUOXA2, associated with p53 degradation-mediated proliferation and intestinal reactive oxygen species (ROS) production, respectively. In HCAE cells, overexpressed genes included EFNA1 and LIF, two genes commonly upregulated in colorectal cancer and associated with poor patient outcomes, and PTGS2 (COX2), a gene associated with the protective effect of aspirin in the colorectal cancer setting. Interestingly, we also observed downregulation of numerous histone modification genes upon F. nucleatum exposure. We used the ChIP-seq data to annotate chromatin states genome wide and found significant chromatin remodeling following F. nucleatum exposure in HCAE cells, with increased frequencies of active enhancer and low-signal/quiescent states. Thus, our results highlight increased inflammation and chemokine gene expression as conserved host cell responses to F. nucleatum exposure and extensive host cell epigenomic changes specific to host cell type. IMPORTANCE Fusobacterium nucleatum is a bacterium normally found in the healthy oral cavity but also has an emerging role in colorectal cancer and other cancer settings. The host-microbe interactions of F. nucleatum and its involvement in tumor initiation, progression, and treatment resistance are not fully understood. We explored host cell changes that occur in response to F. nucleatum. We identified key genes differentially expressed in response to various conditions of F. nucleatum exposure and determined that the conserved host cell response to F. nucleatum was dominated by increased inflammation and chemokine gene expression. Additionally, we found extensive host cell epigenomic changes as a novel aspect of host modulation associated with F. nucleatum exposure. These results extend our understanding of F. nucleatum as an emerging pathogen and highlight the importance of considering strain heterogeneity and host cell phenotypic variation when exploring pathogenic mechanisms of F. nucleatum.

Immunoglobulin A, an Active Liaison for Host-Microbiota Homeostasis

Mucosal surfaces in the gastrointestinal tract are continually exposed to native, commensal antigens and susceptible to foreign, infectious antigens. Immunoglobulin A (IgA) provides dual humoral responses that create a symbiotic environment for the resident gut microbiota and prevent the invasion of enteric pathogens. This review features recent immunological and microbial studies that elucidate the underlying IgA and microbiota-dependent mechanisms for mutualism at physiological conditions. IgA derailment and concurrent microbiota instability in pathological diseases are also discussed in detail. Highlights of this review underscore that the source of IgA and its structural form can dictate microbiota reactivity to sustain a diverse niche where both host and bacteria benefit. Other important studies emphasize IgA insufficiency can result in the bloom of opportunistic pathogens that encroach the intestinal epithelia and disseminate into circulation. The continual growth of knowledge in these subjects can lead to the development of therapeutics targeting IgA and/or the microbiota to treat life threatening diseases.

Fusobacterium nucleatum Acts as a Pro-carcinogenic Bacterium in Colorectal Cancer: From Association to Causality

Colorectal cancer (CRC) is a common cancer worldwide with complex etiology. Fusobacterium nucleatum (F. nucleatum), an oral symbiotic bacterium, has been linked with CRC in the past decade. A series of gut microbiota studies show that CRC patients carry a high abundance of F. nucleatum in the tumor tissue and fecal, and etiological studies have clarified the role of F. nucleatum as a pro-carcinogenic bacterium in various stages of CRC. In this review, we summarize the biological characteristics of F. nucleatum and the epidemiological associations between F. nucleatum and CRC, and then highlight the mechanisms by which F. nucleatum participates in CRC progression, metastasis, and chemoresistance by affecting cancer cells or regulating the tumor microenvironment (TME). We also discuss the research gap in this field and give our perspective for future studies. These findings will pave the way for manipulating gut F. nucleatum to deal with CRC in the future.

Microbiota-antibody interactions that regulate gut homeostasis

Immunoglobulin A (IgA) is the most abundant antibody at mucosal surfaces and has been the subject of many investigations involving microbiota research in the last decade. Although the classic functions of IgA include neutralization of harmful toxins, more recent investigations have highlighted an important role for IgA in regulating the composition and function of the commensal microbiota. Multiple reviews have comprehensively covered the literature that describes recent, novel mechanisms of action of IgA and development of the IgA response within the intestine. Here we focus on how the interaction between IgA and the microbiota promotes homeostasis with the host to prevent disease.

Tumor models to assess immune response and tumor-microbiome interactions in colorectal cancer

Despite significant advances over the past 2 decades in preventive screening and therapy aimed at improving patient survival, colorectal cancer (CRC) remains the second most common cause of cancer death in the United States. The average 5-year survival rate of CRC patients with positive regional lymph nodes is only 40%, while less than 5% of patients with distant metastases survive beyond 5 years. There is a critical need to develop novel therapies that can improve overall survival in patients with poor prognoses, particularly since 60% of them are diagnosed at an advanced stage. Pertinently, immune checkpoint blockade therapy has dramatically changed how we treat CRC patients with microsatellite-instable high tumors. Furthermore, accumulating evidence shows that changes in gut microbiota are associated with the regulation of host antitumor immune response and cancer progression. Appropriate animal models are essential to deciphering the complex mechanisms of host antitumor immune response and tumor-gut microbiome metabolic interactions. Here, we discuss various mouse models of colorectal cancer that are developed to address key questions on tumor immune response and tumor-microbiota interactions. These CRC models will also serve as resourceful tools for effective preclinical studies.

Temporal dynamics of the plasma microbiome in recipients at early post-liver transplantation: a retrospective study

Background

Immunosuppression during liver transplantation (LT) enables the prevention and treatment of organ rejection but poses a risk for severe infectious diseases. Immune modulation and antimicrobials affect the plasma microbiome. Thus, determining the impact of immunosuppression on the microbiome may be important to understand immunocompetence, elucidate the source of infection, and predict the risk of infection in LT recipients. We characterized the plasma microbiome of LT recipients at early post-LT and assessed the association between the microbiome and clinical events.

Results

In this study, 51 patients who received LT at Nagoya University Hospital from 2016 to 2018 were enrolled. Plasma samples were retrospectively collected at the following time points: 1) within a week after LT; 2) 4 ± 1 weeks after LT; 3) 8 ± 1 weeks after LT; and 4) within 2 days after a positive blood culture. A total of 111 plasma samples were analyzed using shotgun next-generation sequencing (NGS) with the PATHDET pipeline. Relative abundance of Anelloviridae, Nocardiaceae, Microbacteriaceae, and Enterobacteriaceae significantly changed during the postoperative period. Microbiome diversity was higher within a week after LT than that at 8 weeks after LT. Antimicrobials were significantly associated with the microbiome of LT recipients. In addition, the proportion of Enterobacteriaceae was significantly increased and the plasma microbiome diversity was significantly lower in patients with acute cellular rejection (ACR) than non-ACR patients. Sequencing reads of bacteria isolated from blood cultures were predominantly identified by NGS in 8 of 16 samples, and human herpesvirus 6 was detected as a causative pathogen in one recipient with severe clinical condition.

Conclusions

The metagenomic NGS technique has great potential in revealing the plasma microbiome and is useful as a comprehensive diagnostic procedure in clinical settings. Temporal dynamics of specific microorganisms may be used as indirect markers for the determination of immunocompetence and ACR in LT recipients.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12866-021-02154-w.

The dysbiosis signature of Fusobacterium nucleatum in colorectal cancer-cause or consequences? A systematic review

Colorectal cancer (CRC) is the third most common cause of cancer globally and the fourth attributable cause of mortality and morbidity due to cancer. An emerging factor contributing to CRC is the gut microbiota and the cellular changes associated with it. Further insights on this may help in the prevention, diagnosis and new therapeutic approaches to colorectal cancer. In most cases of CRC, genetic factors appear to contribute less to its aetiology than environmental and epigenetic factors; therefore, it may be important to investigate these environmental factors, their effects, and the mechanisms that may contribute to this cancer. The gut microbiota has recently been highlighted as a potential risk factor that may affect the structural components of the tumor microenvironment, as well as free radical and enzymatic metabolites directly, or indirectly. Many studies have reported changes in the gut microbiota of patients with colorectal cancer. What is controversial is whether the cancer is the cause or consequence of the change in the microbiota. There is strong evidence supporting both possibilities. The presence of Fusobacterium nucleatum in human colorectal specimens has been demonstrated by RNA-sequencing. F. nucleatum has been shown to express high levels of virulence factors such as FadA, Fap2 and MORN2 proteins. Our review of the published data suggest that F. nucleatum may be a prognostic biomarker of CRC risk, and hence raises the potential of antibiotic treatment of F. nucleatum for the prevention of CRC.

Prediagnostic Antibody Responses to Fusobacterium nucleatum Proteins Are Not Associated with Risk of Colorectal Cancer in a Large U.S. Consortium

BACKGROUND

The association between prediagnostic antibody responses to Fusobacterium nucleatum (F. nucleatum) and subsequent risk of colorectal cancer is not established.

METHODS

We conducted a nested case-control study of 8,126 participants in a consortium of 10 prospective cohorts in the United States.

RESULTS

Higher seroprevalence of any F. nucleatum antibody was observed among non-White participants (51.1%) compared with White participants (31.2%). We did not find any statistically significant association between seropositivity to any of the eight F. nucleatum proteins and colorectal cancer risk.

CONCLUSIONS

Prediagnostic antibody responses to F. nucleatum proteins were not associated with the risk of colorectal cancer.

IMPACT

Future studies may consider a more specific detection of the immunoglobulin isotypes or focus on examining F. nucleatum in stool or tissue samples.

Diagnostic accuracy of Fusobacterium nucleatum IgA and IgG ELISA test in colorectal cancer

The colorectal cancer is a serious health problem. The diagnosis of the disease mostly relies on an invasive procedure. A non-invasive diagnostic test such as an immunoassay, may facilitate diagnosis of colorectal cancer. The purpose of the study was to evaluate the use of antibodies against Fusobacterium nucleatum in the diagnosis of colorectal cancer (CRC). Totally 78 patients in three groups were included in the study. F. nucleatum in the tissues was detected using quantitative polymerase chain reaction assay. F. nucleatum IgA and IgG were measured using enzyme linked immunosorbent assay. F. nucleatum was detected in 86.7% and 73.1% cases of CRC and precancerous-benign colon disease (P-BCD), respectively. The OD values from F. nucleatum IgA and IgG ELISA tests were higher in CRC group compared with healthy individuals. The sensitivity of IgA ELISA test varied between 31.8 and 95.5% depending on the chosen cut-off values. The positivity rate of antibodies in patients with high amount of F. nucleatum in tissue was significantly greater than in the negative group. The F. nucleatum IgA and IgG antibodies in CRC were higher than the ones in healthy controls but the discriminative ability of the ELISA test was not adequate to be considered as a diagnostic tool.

Resolving the Paradox of Colon Cancer Through the Integration of Genetics, Immunology, and the Microbiota

While colorectal cancers (CRC) are paradigmatic tumors invaded by effector memory lymphocytes, the mechanisms accounting for the relative resistance of MSI negative CRC to immunogenic cell death mediated by oxaliplatin and immune checkpoint inhibitors has remained an open conundrum. Here, we propose the viewpoint where its microenvironmental contexture could be explained -at least in part- by macroenvironmental cues constituted by the complex interplay between the epithelial barrier, its microbial ecosystem, and the local immune system. Taken together this dynamic ménage-à-trois offers novel coordinated actors of the humoral and cellular immune responses actionable to restore sensitivity to immune checkpoint inhibition. Solving this paradox involves breaking tolerance to crypt stem cells by inducing the immunogenic apoptosis of ileal cells in the context of an ileal microbiome shifted towards immunogenic bacteria using cytotoxicants. This manoeuver results in the elicitation of a productive Tfh and B cell dialogue in mesenteric lymph nodes culminating in tumor-specific memory CD8+ T cell responses sparing the normal epithelium.

The Role of Fusobacterium nucleatum in Colorectal Carcinogenesis

Colorectal cancer (CRC) is one of the most frequent and deadly neoplasms worldwide. Genetic factors, lifestyle habits, and inflammation are important risk factors associated with CRC development. In recent years, growing evidence has supporting the significant role of the intestinal microbiome in CRC carcinogenesis. Disturbances in the healthy microbial balance, known as dysbiosis, are frequently observed in these patients. Pathogenic microorganisms that induce intestinal dysbiosis have become an important target to determine the role of bacterial infection in tumorigenesis. Interestingly, the presence of different bacterial strains, such as Fusobacterium nucleatum, has been detected in tissue and stool from patients with CRC and associated with substantial clinical and molecular features, as well as with patient therapy response. Therefore, understanding how the presence and levels of F. nucleatumstrains in the gut affect the risk of CRC onset and progression may inform suitable candidates for interventions focused on modulation of this bacteria. Here we review new insights into the role of gut microbiota in CRC carcinogenesis and the clinical utility of using the detection of F. nucleatum in different settings such as screening, prognosis, and microbiota modulation as a means to prevent cancer, augment therapies, and reduce adverse effects of treatment.

Microbiota and Cancer: The Emerging Beneficial Role of Bifidobacteria in Cancer Immunotherapy

Many intestinal bacteria are believed to be involved in various inflammatory and immune processes that influence tumor etiology because of their metabolic properties and their ability to alter the microbiota homeostasis. Although many functions of the microbiota are still unclear, there is compelling experimental evidence showing that the intestinal microbiota is able to modulate carcinogenesis and the response to anticancer therapies, both in the intestinal tract and other body sites. Among the wide variety of gut-colonizing microorganisms, various species belonging to the Bifidobacterium genus are believed to elicit beneficial effects on human physiology and on the host-immune system. Recent findings, based on preclinical mouse models and on human clinical trials, have demonstrated the impact of gut commensals including bifidobacteria on the efficacy of tumor-targeting immunotherapy. Although the underlying molecular mechanisms remain obscure, bifidobacteria and other microorganisms have become a promising aid to immunotherapeutic procedures that are currently applied to treat cancer. The present review focuses on strategies to recruit the microbiome in order to enhance anticancer responses and develop therapies aimed at fighting the onset and progression of malignancies.

Circulating and Salivary Antibodies to Fusobacterium nucleatum Are Associated With Cystic Pancreatic Neoplasm Malignancy

Objectives

Intraductal papillary mucinous neoplasms (IPMNs) are cystic precursor lesions to pancreatic cancer. The presence of oral microbes in pancreatic tissue or cyst fluid has been associated with high-grade dysplasia (HGD) and cancer. The present study aims at investigating if humoral immunity to pancreas-associated oral microbes reflects IPMN severity.

Design

Paired plasma (n = 109) and saliva (n = 65) samples were obtained from IPMN pancreatic cystic tumor cases and controls, for anti-bacterial antibody analysis and DNA quantification by enzyme-linked immunosorbent assay (ELISA) and qPCR, respectively. Tumor severity was graded by histopathology, laboratory, and clinical data. Circulating plasma and salivary antibody reactivity to a pancreas-associated oral microbe panel were measured by ELISA and correlated to tumor severity.

Results

The patient group with high-risk cystic tumors (HGD and/or associated invasive cancer) shows ample circulating IgG reactivity to Fusobacterium nucleatum (F. nucleatum) but not to Granulicatella adiacens (G. adiacens), which is independent of the salivary bacteria DNA levels. This group also shows higher salivary IgA reactivity to F. nucleatum, Fap2 of F. nucleatum, and Streptococcus gordonii (S. gordonii) compared to low-risk IPMN and controls. The salivary antibody reactivity to F. nucleatum and Fap2 are found to be highly correlated, and cross-competition assays further confirm that these antibodies appear cross-reactive.

Conclusion

Our findings indicate that humoral reactivity against pancreas-associated oral microbes may reflect IPMN severity. These findings are beneficial for biomarker development.

Clostridioides difficile antibody response of colorectal cancer patients versus clinically healthy individuals

Dysbiosis, defined as an imbalance in the gut microbiota caused by too few beneficial bacteria and an overgrowth of bad bacteria, yeast, and/or parasites, is now being associated with several diseases, including the development of colorectal carcinoma (CRC). In this study, the potential association of Clostridioides difficile (formerly Clostridium difficile) with CRC was investigated. Plasma samples obtained from preoperative histologically confirmed CRC patients (n=39) and their age- and sex-matched clinically healthy controls (n=39) were analyzed for antibodies to toxin B of C. difficile (anti-tcdB) by enzyme-linked immunosorbent assay (ELISA). A significantly greater number (p=0.012) of CRC cases (n=26/39, 66.7%) had anti-tcdB IgG levels above the cutoff value compared with controls (n=12/39, 30.8%). Eight cases (8/39, 20.5%) and none of the controls registered anti-tcdB IgA levels above the cutoff value (p=0.0039). Anti-tcdB IgG and IgA levels were not shown to be significantly associated with tumor grade or tumor stage. Anti-tcdB IgG showed 66.7% sensitivity and 69.2% specificity. For anti-tcdB IgA, sensitivity and specificity were 20.5% and 100%, respectively. The positive predictive values for anti-tcdB IgA and IgG were 100% and 68.4%, respectively. The anti-tcdB IgA and IgG negative predictive values were 55.7% and 67.5%, respectively. The results suggest the potential association of C. difficile with CRC and anti-tcdB levels, particularly the IgA level. Hence, anti-tcdB antibodies can be candidate serologic markers for CRC.

The Bacterial Connection between the Oral Cavity and the Gut Diseases

More than 100 trillion symbiotic microorganisms constitutively colonize throughout the human body, including the oral cavity, the skin, and the gastrointestinal tract. The oral cavity harbors one of the most diverse and abundant microbial communities within the human body, second to the community that resides in the gastrointestinal tract, and is composed of >770 bacterial species. Advances in sequencing technologies help define the precise microbial landscape in our bodies. Environmental and functional differences render the composition of resident microbiota largely distinct between the mouth and the gut and lead to the development of unique microbial ecosystems in the 2 mucosal sites. However, it is apparent that there may be a microbial connection between these 2 mucosal sites in the context of disease pathogenesis. Accumulating evidence indicates that resident oral bacteria can translocate to the gastrointestinal tract through hematogenous and enteral routes. The dissemination of oral microbes to the gut may exacerbate various gastrointestinal diseases, including irritable bowel syndrome, inflammatory bowel disease, and colorectal cancer. However, the precise role that oral microbes play in the extraoral organs, including the gut, remains elusive. Here, we review the recent findings on the dissemination of oral bacteria to the gastrointestinal tract and their possible contribution to the pathogenesis of gastrointestinal diseases. Although little is known about the mechanisms of ectopic colonization of the gut by oral bacteria, we also discuss the potential factors that allow the oral bacteria to colonize the gut.

Fusobacterium nucleatum Causes Microbial Dysbiosis and Exacerbates Visceral Hypersensitivity in a Colonization-Independent Manner

Background: Microbial dysbiosis is closely associated with visceral hypersensitivity and is involved in the pathogenesis of irritable bowel syndrome (IBS), but the specific strains that play a key role have yet to be identified. Previous bioinformatic studies have demonstrated that Fusobacterium is a shared microbial feature between IBS patients and maternal separation (MS)-stressed rats. In this study, we assessed the potential role of Fusobacterium nucleatum (F. nucleatum) in the pathogenesis of IBS.

Methods: Fecal samples of patients with diarrhea predominant-IBS (IBS-D) and healthy controls were obtained. An MS rat model was established to receive gavage of either F. nucleatum or normal saline. Visceral sensitivity was evaluated through colorectal distension test, and fecal microbiota was analyzed by 16S rRNA gene sequencing. F. nucleatum-specific IgA levels in fecal supernatants were assessed by western blotting. The antigen reacted with the specific IgA of F. nucleatum was identified by mass spectrometry and the construction of a recombinant Escherichia coli BL21 (DE3).

Results: IBS-D patients showed a lower Shannon index and a higher abundance of Fusobacterium. The F. nucleatum-gavage was shown to exacerbate visceral hypersensitivity in MS rats, with both the F. nucleatum-gavage and MS causing a decreased Shannon index and a clear segregation of fecal microbiota. In addition, specific IgA against F. nucleatum was detected in fecal supernatants of both the F. nucleatum-gavaged rats and the IBS-D patients. The FomA protein, which is a major outer membrane protein of F. nucleatum, was confirmed to react with the specific IgA of F. nucleatum in fecal supernatants.

Conclusion:Fusobacterium increased significantly in IBS-D patients, and F. nucleatum was involved in the pathogenesis of IBS by causing microbial dysbiosis and exacerbating visceral hypersensitivity in a colonization-independent manner. Meanwhile, F. nucleatum was found to induce an increase in specific secretory IgA through FomA.

Diagnostic value of circular RNAs in female reproductive system diseases: A PRISMA-compliant meta-analysis

Circular RNAs (circRNAs) are novel non-coding RNAs that have been reported to be involved in the progression of numerous diseases. However, the clinical diagnostic value of circRNAs in female reproductive system diseases remains unknown. The present study is a systemic review and meta-analysis of the available literature on circRNAs as novel biomarkers for female reproductive system diseases. Relevant studies were systematically searched using the PubMed, Embase, Web of Science and Cochrane Library databases. The data obtained from the included studies were analyzed by RevMan5.3 and STATA 14.2. A total of six studies involving 613 individuals across three types of disease examined the diagnostic capabilities of circRNAs. Within these publications, the pooled sensitivity of circRNAs was 0.70 (95% CI, 0.64-0.76), and the pooled specificity was 0.70 (95% CI, 0.64-0.75). The pooled positive likelihood ratio and negative likelihood ratio were 2.33 and 0.42, respectively. The diagnostic score was 1.70 and the pooled diagnostic odds ratio was 5.48. The area under the summary receiver operator characteristic curve was 0.76 (95% CI, 0.72-0.79), indicating that circRNAs exhibited a moderate diagnostic value for female reproductive system diseases and may function as potential diagnostic biomarkers. However, further studies are required to verify the clinical applications of circRNAs.

Fusobacterium nucleatum in the Colorectum and Its Association with Cancer Risk and Survival: A Systematic Review and Meta-analysis

BACKGROUND

The gut microbiome, in particular Fusobacterium nucleatum, has been reported to play a role in colorectal cancer development and in patient prognosis. We aimed to perform a systematic review and meta-analysis of published studies to assess the prevalence of F. nucleatum in colorectal tumors and evaluate the association between F. nucleatum and colorectal cancer development and prognosis.

METHODS

MEDLINE, EMBASE, and Web of Science databases were systematically searched for studies published until January 2019. Random effects meta-analyses were used to assess the prevalence of F. nucleatum in patients with colorectal cancer or tissues relative to controls and survival in F. nucleatum-positive versus -negative patients.

RESULTS

Forty-five relevant articles were identified. Meta-analyses indicated higher odds of F. nucleatum being present in colorectal tissue samples from patients with colorectal cancer [n = 6 studies, pooled OR = 10.06; 95% confidence intervals (CI), 4.48-22.58] and individuals with colorectal polyps (n = 5 studies, pooled OR = 1.83; 95% CI, 1.07-3.16) compared with healthy controls. Similar results were apparent in fecal samples, and when comparing tumor with adjacent normal tissue. Meta-analyses indicated poorer survival in patients with colorectal cancer with high versus low F. nucleatum abundance (n = 5 studies, pooled HR = 1.87; 95% CI, 1.12-3.11).

CONCLUSIONS

A consistent increase in the prevalence and/or abundance of F. nucleatum in colorectal cancer tissue and fecal samples compared with controls was apparent. High abundance of F. nucleatum in colorectal tumors was also associated with poorer overall survival.

IMPACT

F. nucleatum could be useful as a diagnostic and prognostic marker for colorectal cancer or as a treatment target.

Fusobacterium nucleatum - symbiont, opportunist and oncobacterium

Fusobacterium nucleatum has long been found to cause opportunistic infections and has recently been implicated in colorectal cancer; however, it is a common member of the oral microbiota and can have a symbiotic relationship with its hosts. To address this dissonance, we explore the diversity and niches of fusobacteria and reconsider historic fusobacterial taxonomy in the context of current technology. We also undertake a critical reappraisal of fusobacteria with a focus on F. nucleatum as a mutualist, infectious agent and oncogenic microorganism. In this Review, we delve into recent insights and future directions for fusobacterial research, including the current genetic toolkit, our evolving understanding of its mechanistic role in promoting colorectal cancer and the challenges of developing diagnostics and therapeutics for F. nucleatum.

Our Microbiome: On the Challenges, Promises, and Hype

The microbiome field is increasingly raising interest among scientists, clinicians, biopharmaceutical entities, and the general public. Technological advances from the past two decades have enabled the rapid expansion of our ability to characterize the human microbiome in depth, highlighting its previously underappreciated role in contributing to multifactorial diseases including those with unknown etiology. Consequently, there is growing evidence that the microbiome could be utilized in medical diagnosis and patient stratification. Moreover, multiple gut microbes and their metabolic products may be bioactive, thereby serving as future potential microbiome-targeting or -associated therapeutics. Such therapies could include new generation probiotics, prebiotics, fecal microbiota transplantations, postbiotics, and dietary modulators. However, microbiome research has also been associated with significant limitations, technical and conceptual challenges, and, at times, "over-hyped" expectations that microbiome research will produce quick solutions to chronic and mechanistically complex human disorders. Herein, we summarize these challenges and also discuss some of the realistic promises associated with microbiome research and its applicability into clinical application.

Gut microbiota in colorectal cancer: mechanisms of action and clinical applications

Colorectal cancer (CRC) accounts for about 10% of all new cancer cases globally. Located at close proximity to the colorectal epithelium, the gut microbiota comprises a large population of microorganisms that interact with host cells to regulate many physiological processes, such as energy harvest, metabolism and immune response. Sequencing studies have revealed microbial compositional and ecological changes in patients with CRC, whereas functional studies in animal models have pinpointed the roles of several bacteria in colorectal carcinogenesis, including Fusobacterium nucleatum and certain strains of Escherichia coli and Bacteroides fragilis. These findings give new opportunities to take advantage of our knowledge on the gut microbiota for clinical applications, such as gut microbiota analysis as screening, prognostic or predictive biomarkers, or modulating microorganisms to prevent cancer, augment therapies and reduce adverse effects of treatment. This Review aims to provide an overview and discussion of the gut microbiota in colorectal neoplasia, including relevant mechanisms in microbiota-related carcinogenesis, the potential of utilizing the microbiota as CRC biomarkers, and the prospect for modulating the microbiota for CRC prevention or treatment. These scientific findings will pave the way to clinically translate the use of gut microbiota for CRC in the near future.

Targeting Programmed Fusobacterium nucleatum Fap2 for Colorectal Cancer Therapy

Colorectal patients generally have the maximum counts of Fusobacterium nucleatum (F. nucleatum) in tumors and elevate colorectal adenomas and carcinomas, which show the lowest rate of human survival. Hence, F. nucleatum is a diagnostic marker of colorectal cancer (CRC). Studies demonstrated that targeting fusobacterial Fap2 or polysaccharide of the host epithelium may decrease fusobacteria count in the CRC. Attenuated F. nucleatum-Fap2 prevents transmembrane signals and inhibits tumorigenesis inducing mechanisms. Hence, in this review, we hypothesized that application of genetically programmed fusobacterium can be skillful and thus reduce fusobacterium in the CRC. Genetically programmed F. nucleatum is a promising antitumor strategy.

The Four Horsemen in Colon Cancer

Worldwide, neoplasms of the gastrointestinal tract have a very high incidence and mortality. Among these, colorectal cancer, which includes colon and rectum malignancies, representing both highest incidence and mortality. While gallbladder cancer, another neoplasm associated to gastrointestinal tract occurs less frequently. Genetic factors, inflammation and nutrition are important risk factors associated with colorectal cancer development. Likewise, pathogenic microorganisms inducing intestinal dysbiosis have become an important scope to determine the role of bacterial infection on tumorigenesis. Interestingly, in human biopsies of different types of gastrointestinal tract cancer, the presence of different bacterial strains, such as Fusobacterium nucleatum, Escherichia coli, Bacteroides fragilis and Salmonella enterica have been detected, and it has been considered as a high-risk factor to cancer development. Therefore, pathogens infection could contribute to neoplastic development through different mechanisms; including intestinal dysbiosis, inflammation, evasion of tumoral immune response and activation of pro-tumoral signaling pathways, such as β catenin. Here, we have reviewed the suggested bacterial molecular mechanisms and their possible role on development and progression of gastrointestinal neoplasms, focusing mainly on colon neoplasms, where the bacteria Fusobacterium nucleatum, Escherichia coli, Bacteroides fragilis and Salmonella enterica infect.

Prognostic impact of the Fusobacterium nucleatum status in colorectal cancers

To investigate the clinicopathological features and prognostic impact of Fusobacterium nucleatum (F nucleatum) status in patients with colorectal cancer (CRC) and its relationships with microsatellite instability (MSI) status.Retrospective analysis of consecutive 91 CRC tissues from surgically resected specimens of stage III or high-risk stage II CRC patients who had received curative surgery in Wuhan Union Hospital from January, 2017 to January, 2019 was conducted. F nucleatum DNA was quantitatively measured and classified into 1 of the 2 categories: F nucleatum-high, or F nucleatum-low/negative. The Cox risk ratio model analysis was performed to identify independent risk factors of F nucleatum. F nucleatum-high group was compared with the F nucleatum-low/negative group with respect to clinicopathological features and their relationships with MSI status. Kaplan-Meier method and log-rank test were used for univariate analysis of prognostic factors in patients with CRC.The number of total lymph node acquisition and positive lymph nodes, neurological invasion, vascular tumor thrombus were higher in F nucleatum-high group (27.44 ± 25.213 vs 20.70 ± 10.141; P = .018; 3.80 ± 7.974 vs 1.74 ± 3.531; P = .001; 68.0% vs 33.3%; P = .003; 60.0% vs 25.8%; P = .002). Moreover, microsatellite mutations were more frequent in patients with F nucleatum-high (84.0% vs 60.6%; P = .034). A higher abundance of F nucleatum in CRC is associated with a shorter survival time. The F nucleatum status, peripheral nerve invasion, vascular tumor thrombus, lymph node metastasis, and TNM staging were related factors affecting the prognosis of patients with CRC. The Cox risk ratio model analysis showed that the F nucleatum (odds ratio [OR] 2.094, 95% confidence interval [CI] 1.178-8.122, P = .032) and MSI status (OR 2.243, 95% CI 1.136-5.865, P = 0.039) were independent prognostic factors.Intratumoral F nucleatum load has a poor prognostic effect of CRC by increasing nerve invasion, vascular tumor thrombus, and microsatellite mutation.

Fusobacterium nucleatum, the communication with colorectal cancer

Colorectal cancer (CRC) is the fourth most common cancer in 2018 with poor prognosis. Fusobacterium nucleatum (F.n), an anaerobe, is found to be enriched in both stools and tumor tissues of CRC patients. As surveys show, tumor initiates before the collection of F.n. In return, F.n helps cancer cells to build up tumor microenvironment and benefit for their chemo-resistant. The elements constituted the tumor environment, including neutrophils, macrophages and lymphocytes, contribute to the existing of tumor cells respectively. However, the integrated and interactive roles of those elements are poorly investigated. The intracellular molecular alteration MSI is a result of F.n infection and the microbiology-molecular pathological epidemiology (MPE) has become a new trend to analysis F.n and tumorigenesis. Chemoresistance of tumor cells is also affected by F.n induced microenvironment, or F.n achieves it directly. Finally, F.n could be a biomarker of CRC. All in all, our review will lay a foundation for the therapy of CRC through the interference of F.n and perspective to follow-up studies.