Fusobacterium Nucleatum Subspecies Animalis Influences Proinflammatory Cytokine Expression and Monocyte Activation in Human Colorectal Tumors

Alterations, Interactions, and Diagnostic Potential of Gut Bacteria and Viruses in Colorectal Cancer

Gut microbiome alteration was closely associated with colorectal cancer (CRC). Previous studies had demonstrated the bacteria composition changes but lacked virome profiles, trans-kindom interactions, and reliable diagnostic model explorations in CRC. Hence, we performed metagenomic sequencing to investigate the gut microbiome and microbial interactions in adenoma and CRC patients. We found the decreased microbial diversity in CRC and revealed the taxonomic alterations of bacteria and viruses were highly associated with CRC at the species level. The relative abundance of oral-derived species, such as Fusobacterium nucleatum, Fusobacterium hwasookii, Porphyromonas gingivalis, and Bacteroides fragilis, increased. At the same time, butyrate-producing and anti-inflammatory microbes decreased in adenoma and CRC by non-parametric Kruskal-Wallis test. Despite that, the relative abundance of Escherichia viruses and Salmonella viruses increased, whereas some phages, including Enterobacteria phages and Uncultured crAssphage, decreased along with CRC development. Gut bacteria was negatively associated with viruses in CRC and healthy control by correlation analysis (P=0.017 and 0.002, respectively). Viruses were much more dynamic than the bacteria as the disease progressed, and the altered microbial interactions were distinctively stage-dependent. The degree centrality of microbial interactions decreased while closeness centrality increased along with the adenoma to cancer development. Uncultured crAssphage was the key bacteriophage that enriched in healthy controls and positively associated with butyrate-producing bacteria. Diagnostic tests based on bacteria by random forest confirmed in independent cohorts showed better performance than viruses for CRC. In conclusion, our study revealed the novel CRC-associated bacteria and viruses that exhibited specific differences and intensive microbial correlations, which provided a reliable diagnostic panel for CRC.

Association of Fusobacterium nucleatum infection and colorectal cancer: A Mexican study

INTRODUCTION AND AIMS

Colorectal cancer (CRC) is the third most prevalent cancer worldwide. Many risk factors are involved, and current evidence links the gut microbiota and colorectal carcinogenesis. Fusobacterium nucleatum is proposed as one of the risk factors at the onset and during the progression of CRC, due to immune system and inflammatory modulation.

MATERIALS AND METHODS

Ninety samples from three different regions of the colon were collected through colonoscopy in patients with CRC, and qPCR TagMan® was conducted to detect F. nucleatum and cytokines (IL-17, IL-23, and IL-10) in tumor, peritumor, and normal samples. The differences between them were analyzed and correlated.

RESULTS

The abundance of F. nucleatum determined through the 2-ΔΔCt method in CRC (7.750 [5.790-10.469]) was significantly higher than in the normal control (0.409 [0.251-0.817]) (p<0.05). There was no significant association between F. nucleatum and the cytokines (p>0.05).

CONCLUSIONS

CRC is a heterogeneous disease that presents and progresses in a complex microenvironment, partially due to gut microbiome imbalance. F. nucleatum was enriched in CRC tissue, but whether that is a cause of the pathology or a consequence, has not yet been clearly defined.

The microbiota-gut-bone axis and bone health

The gastrointestinal tract is colonized by trillions of microorganisms, consisting of bacteria, fungi, and viruses, known as the "second gene pool" of the human body. In recent years, the microbiota-gut-bone axis has attracted increasing attention in the field of skeletal health/disorders. The involvement of gut microbial dysbiosis in multiple bone disorders has been recognized. The gut microbiota regulates skeletal homeostasis through its effects on host metabolism, immune function, and hormonal secretion. Owing to the essential role of the gut microbiota in skeletal homeostasis, novel gut microbiota-targeting therapeutics, such as probiotics and prebiotics, have been proven effective in preventing bone loss. However, more well-controlled clinical trials are still needed to evaluate the long-term efficacy and safety of these ecologic modulators in the treatment of bone disorders.

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.

Comparative Analysis of Colon Cancer-Derived Fusobacterium nucleatum Subspecies: Inflammation and Colon Tumorigenesis in Murine Models

Fusobacteria are commonly associated with human colorectal cancer (CRC), but investigations are hampered by the absence of a stably colonized murine model. Further, Fusobacterium nucleatum subspecies isolated from human CRC have not been investigated. While F. nucleatum subspecies are commonly associated with CRC, their ability to induce tumorigenesis and contributions to human CRC pathogenesis are uncertain. We sought to establish a stably colonized murine model and to understand the inflammatory potential and virulence genes of human CRC F. nucleatum, representing the 4 subspecies, animalis, nucleatum, polymorphum, and vincentii. Five human CRC-derived and two non-CRC derived F. nucleatum strains were tested for colonization, tumorigenesis, and cytokine induction in specific-pathogen-free (SPF) and/or germfree (GF) wild-type and ApcMin/+ mice, as well as in vitro assays and whole-genome sequencing (WGS). SPF wild-type and ApcMin/+ mice did not achieve stable colonization with F. nucleatum, whereas certain subspecies stably colonized some GF mice but without inducing colon tumorigenesis. F. nucleatum subspecies did not form in vivo biofilms or associate with the mucosa in mice. In vivo inflammation was inconsistent across subspecies, whereas F. nucleatum induced greater cytokine responses in a human colorectal cell line, HCT116. While F. nucleatum subspecies displayed genomic variability, no distinct virulence genes associated with human CRC strains were identified that could reliably distinguish these strains from non-CRC clinical isolates. We hypothesize that the lack of F. nucleatum-induced tumorigenesis in our model reflects differences in human and murine biology and/or a synergistic role for F. nucleatum in concert with other bacteria to promote carcinogenesis. IMPORTANCE Colon cancer is a leading cause of cancer morbidity and mortality, and it is hypothesized that dysbiosis in the gut microbiota contributes to colon tumorigenesis. Fusobacterium nucleatum, a member of the oropharyngeal microbiome, is enriched in a subset of human colon tumors. However, it is unclear whether this genetically varied species directly promotes tumor formation, modulates mucosal immune responses, or merely colonizes the tumor microenvironment. Mechanistic studies to address these questions have been stymied by the lack of an animal model that does not rely on daily orogastric gavage. Using multiple murine models, in vitro assays with a human colon cancer cell line, and whole-genome sequencing analysis, we investigated the proinflammatory and tumorigenic potential of several F. nucleatum clinical isolates. The significance of this research is development of a stable colonization model of F. nucleatum that does not require daily oral gavages in which we demonstrate that a diverse library of clinical isolates do not promote tumorigenesis.

The association between Fusobacterium nucleatum and cancer colorectal: a systematic review and meta-analysis

INTRODUCTION

The etiological factors of colorectal cancer (CRC) are not precisely known, although genetic and environmental factors have been implicated. A possible association with Fusobacterium nucleatum may provide opportunities for an early diagnosis.

OBJECTIVE

To review studies that address the association between F. nucleatum and CRC.

METHODS

The MEDLINE PubMed database was searched using the terms «colorectal cancer» and «Fusobacterium nucleatum», retrieving publications published up to January 1 2020. Stata software was used for a meta-analysis.

RESULTS

The systematic review included 57 articles. Meta-analysis results indicated a more frequent presence of F. nucleatum in CRC tumor tissue samples in comparison to control samples of healthy tissue, with an odds ratio of 4.558 (95% CI: 3.312-6.272), and in comparison, to control samples of colorectal adenomas, with an odds ratio of 3.244 (95% CI: 2.359-4.462).

CONCLUSION

There is a more frequent presence of F. nucleatum in the CRC. However, further studies are needed to verify this relationship.

Salivary CCL20 Level as a Biomarker for Oral Squamous Cell Carcinoma

BACKGROUND/AIM

This study investigated the utility of C-C motif chemokine ligand 20 (CCL20) expression in saliva as a biomarker for oral squamous cell carcinoma (OSCC) and also examined the associated microbiome.

MATERIALS AND METHODS

The study group included patients with OSCC or oral potentially malignant disorder (OPMD), and healthy volunteers (HVs). microarray and qRT-PCR were used to compare salivary CCL20 expression levels among groups. Data on CCL20 levels in oral cancer tissues and normal tissues were retrieved from a public database and examined. Furthermore, next-generation sequencing was used to investigate the salivary microbiome.

RESULTS

A significant increase in the expression level of CCL20 was observed in both OSCC tissues and saliva from patients with oral cancer. Fusobacterium was identified as the predominant bacteria in OSCC and correlated with CCL20 expression level. OSCC screening based on salivary CCL20 expression enabled successful differentiation between patients with OSCC and HVs.

CONCLUSION

CCL20 expression may be a useful biomarker for OSCC.

Microbes in Tumoral In Situ Tissues and in Tumorigenesis

Cancerous tumors are severe diseases affecting human health that have a complicated etiology and pathogenesis. Microbes have been considered to be related to the development and progression of numerous tumors through various pathogenic mechanisms in recent studies. Bacteria, which have so far remained the most studied microbes worldwide, have four major possible special pathogenic mechanisms (modulation of inflammation, immunity, DNA damage, and metabolism) that are related to carcinogenesis. This review aims to macroscopically summarize and verify the relationships between microbes and tumoral in situ tissues from cancers of four major different systems (urinary, respiratory, digestive, and reproductive); the abovementioned four microbial pathogenic mechanisms, as well as some synergistic pathogenic mechanisms, are also discussed. Once the etiologic role of microbes and their precise pathogenic mechanisms in carcinogenesis are known, the early prevention, diagnosis, and treatment of cancers would progress significantly.

Detection of Fusobaterium nucleatum in feces and colorectal mucosa as a risk factor for colorectal cancer: a systematic review and meta-analysis

BACKGROUND

Colorectal cancer (CRC) is a major cause of cancer deaths worldwide. Accumulating evidence suggests a potentially important role of colorectal infection with Fusobacterium nucleatum (F. nucleatum) in colorectal carcinogenesis. We conducted a systematic review, including both a qualitative synthesis and a meta-analysis, to synthesize the evidence from the epidemiological literature on the association between F. nucleatum detection in the colon/rectum and CRC.

METHODS

A systematic literature search of Ovid MEDLINE(R), Embase, Web of Science Core Collection, EBM Reviews-Cochrane Database of Systematic Reviews, and CINAHL Plus with Full Text was conducted using earliest inclusive dates up to 4 October 2020. Eligible studies were original, comparative observational studies that reported results on colorectal F. nucleatum detection and CRC. Two independent reviewers extracted the relevant information. Odds ratio (OR) estimates were pooled across studies using the random effects model. Newcastle-Ottawa scale was used to critically appraise study quality.

RESULTS

Twenty-four studies were included in the systematic review, of which 12 were included in the meta-analysis. Studies investigated F. nucleatum in feces, colorectal tissue samples, or both. In most studies included in the systematic review, the load of F. nucleatum was higher, on average, in specimens from CRC patients than in those from CRC-free controls. Meta-analysis showed a positive association between F. nucleatum detection in colorectal specimens and CRC (OR = 8.3; 95% confidence interval (95% CI) 5.2 to 13.0).

CONCLUSIONS

The results of this systematic review suggest that F. nucleatum in the colon/rectum is associated with CRC.

SYSTEMATIC REVIEW REGISTRATION

This systematic review protocol has been registered with the International Prospective Register of Systematic Reviews (PROSPERO) on July 10, 2018 (registration number CRD42018095866).

Analysis of differentially expressed genes in oral epithelial cells infected with Fusobacterium nucleatum for revealing genes associated with oral cancer

Accumulating evidence links Fusobacterium nucleatum with tumorigenesis. Our previous study demonstrated that F. nucleatum infection can induce epithelial‐mesenchymal transition (EMT) in oral epithelial cells and elaborated a probable signal pathway involved in the induction of EMT. However, the comprehensive profiling and pathways of other candidate genes involved in F. nucleatum promoting malignant transformation remain largely elusive. Here, we analysed the transcriptome profile of HIOECs exposed to F. nucleatum infection. Totally, 3307 mRNAs (ǀLog2FCǀ >1.5) and 522 lncRNAs (ǀLog2FCǀ >1) were identified to be differentially expressed in F. nucleatum‐infected HIOECs compared with non‐infected HIOECs. GO and KEGG pathway analyses were performed to investigate the potential functions of the dysregulated genes. Tumour‐associated genes were integrated, and top 10 hub genes (FYN, RAF1, ATM, FOS, CREB, NCOA3, VEGFA, JAK2, CREM and ATF3) were identified by protein‐protein interaction (PPI) network, and Oncomine was used to validate hub genes' expression. LncRNA‐hub genes co‐expression network comprising 67 dysregulated lncRNAs were generated. Together, our study revealed the alteration of lncRNA and potential hub genes in oral epithelial cells in response to F. nucleatum infection, which may provide new insights into the shift of normal to malignant transformation initiated by oral bacterial infection.

The Intestinal Microbiota and Colorectal Cancer

The intestinal microbiota, composed of a large population of microorganisms, is often considered a “forgotten organ” in human health and diseases. Increasing evidence indicates that dysbiosis of the intestinal microbiota is closely related to colorectal cancer (CRC). The roles for intestinal microorganisms that initiated and facilitated the CRC process are becoming increasingly clear. Hypothesis models have been proposed to illustrate the complex relationship between the intestinal microbiota and CRC. Recent studies have identified Streptococcus bovis, enterotoxigenic Bacteroides fragilis, Fusobacterium nucleatum, Enterococcus faecalis, Escherichia coli, and Peptostreptococcus anaerobius as CRC candidate pathogens. In this review, we summarized the mechanisms involved in microbiota-related colorectal carcinogenesis, including inflammation, pathogenic bacteria, and their virulence factors, genotoxins, oxidative stress, bacterial metabolites, and biofilm. We also described the clinical values of intestinal microbiota and novel strategies for preventing and treating CRC.

Analysis of 16S rRNA genes reveals reduced Fusobacterial community diversity when translocating from saliva to GI sites

Fusobacterium nucleatum is a Gram-negative oral commensal anaerobe which has been increasingly implicated in various gastrointestinal (GI) disorders, including inflammatory bowel disease, appendicitis, GI cancers. The oral cavity harbors a diverse group of Fusobacterium, and it is postulated that F. nucleatum in the GI tract originate from the mouth. It is not known, however, if all oral Fusobacterium translocate to the GI sites with equal efficiencies. Therefore, we amplified 16S rRNA genes of F. nucleatum and F. periodonticum, two closely related oral species from matched saliva, gastric aspirates, and colon or ileal pouch aspirates of three patients with inflammatory bowel disease (IBD) and three healthy controls, and saliva alone from seven patients with either active IBD or IBD in remission. The 16S rRNA gene amplicons were cloned, and the DNA sequences determined by Sanger sequencing. The results demonstrate that fusobacterial community composition differs more significantly between the oral and GI sites than between different individuals. The oral communities demonstrate the highest level of variation and have the richest pool of unique sequences, with certain nodes/strains enriched in the GI tract and others diminished during translocation. The gastric and colon/pouch communities exhibit reduced diversity and are more closely related, possibly due to selective pressure in the GI tract. This study elucidates selective translocation of oral fusobacteria to the GI tract. Identification of specific transmissible clones will facilitate risk assessment for developing Fusobacterium-implicated GI disorders.

The Role of Diet Related Short-Chain Fatty Acids in Colorectal Cancer Metabolism and Survival: Prevention and Therapeutic Implications

Colorectal Cancer (CRC) is a major cause of cancer-related death worldwide. CRC increased risk has been associated with alterations in the intestinal microbiota, with decreased production of Short Chain Fatty Acids (SCFAs). SCFAs produced in the human colon are the major products of bacterial fermentation of undigested dietary fiber and starch. While colonocytes use the three major SCFAs, namely acetate, propionate and butyrate, as energy sources, transformed CRC cells primarily undergo aerobic glycolysis. Compared to normal colonocytes, CRC cells exhibit increased sensitivity to SCFAs, thus indicating they play an important role in cell homeostasis. Manipulation of SCFA levels in the intestine, through changes in microbiota, has therefore emerged as a potential preventive/therapeutic strategy for CRC. Interest in understanding SCFAs mechanism of action in CRC cells has increased in the last years. Several SCFA transporters like SMCT-1, MCT-1 and aquaporins have been identified as the main transmembrane transporters in intestinal cells. Recently, it was shown that acetate promotes plasma membrane re-localization of MCT-1 and triggers changes in the glucose metabolism. SCFAs induce apoptotic cell death in CRC cells, and further mechanisms have been discovered, including the involvement of lysosomal membrane permeabilization, associated with mitochondria dysfunction and degradation. In this review, we will discuss the current knowledge on the transport of SCFAs by CRC cells and their effects on CRC metabolism and survival. The impact of increasing SCFA production by manipulation of colon microbiota on the prevention/therapy of CRC will also be addressed.

Colon Cancer-Associated Fusobacterium nucleatum May Originate From the Oral Cavity and Reach Colon Tumors via the Circulatory System

Fusobacterium nucleatum is a common oral bacterium that is enriched in colorectal adenomas and adenocarcinomas (CRC). In humans, high fusobacterial CRC abundance is associated with chemoresistance and poor prognosis. In animal models, fusobacteria accelerate CRC progression. Targeting F. nucleatum may reduce fusobacteria cancer progression and therefore determining the origin of CRC F. nucleatum and the route by which it reaches colon tumors is of biologic and therapeutic importance. Arbitrarily primed PCR performed previously on matched same-patients CRC and saliva F. nucleatum isolates, suggested that CRC F. nucleatum may originate from the oral cavity. However, the origin of CRC fusobacteria as well as the route of their arrival to the tumor have not been well-established. Herein, we performed and analyzed whole genome sequencing of paired, same-patient oral, and CRC F. nucleatum isolates and confirmed that CRC-fusobacteria originate from the oral microbial reservoir. Oral fusobacteria may translocate to CRC by descending via the digestive tract or using the hematogenous route during frequent transient bacteremia caused by chewing, daily hygiene activities, or dental procedures. Using the orthotropic CT26 mouse model we previously showed that IV injected F. nucleatum colonize CRC. Here, we compared CRC colonization by gavage vs. intravenous inoculated F. nucleatum in the MC38 and CT26 mouse orthotropic CRC models. Under the tested conditions, hematogenous fusobacteria were more successful in CRC colonization than gavaged ones. Our results therefore provide evidence that the hematogenous route may be the preferred way by which oral fusobacteria reach colon tumors.

Microbiome within Primary Tumor Tissue from Renal Cell Carcinoma May Be Associated with PD-L1 Expression of the Venous Tumor Thrombus

Objective

To perform a proof of concept microbiome evaluation and PD-L1 expression profiling in clear-cell renal cell carcinoma (cc-RCC) with associated tumor thrombus (TT).

Methods

After IRB approval, six patients underwent radical nephrectomy (RN) with venous tumor thrombectomy (VTT). We collected fresh tissue specimens from normal adjacent, tumor, and thrombus tissues. We utilized RNA sequencing to obtain PD-L1 expression profiles and perform microbiome analysis. Statistical assessment was performed using Student's t-test, chi-square, and spearman rank correlations using SPSS v25.

Results

We noted the tumor thrombus to be mostly devoid of diverse microbiota. A large proportion of Staphylococcus epidermidus was detected and unknown if this is a surgical or postsurgical contaminant; however, it was noted more in the thrombus than other tissues. Microbiome diversity profiles were most abundant in the primary tumor compared to the thrombus or normal adjacent tissue. Differential expression of PD-L1 was examined in the tumor thrombus to the normal background tissue and noted three of the six subjects had a threshold above 2-fold. These three similar subjects had foreign microbiota that are typical residents of the oral microbiome.

Conclusion

Renal tumors have more diverse microbiomes than normal adjacent tissue. Identification of resident oral microbiome profiles in clear-cell renal cancer with tumor thrombus provides a potential biomarker for thrombus response to PD-L1 inhibition.

Tea polyphenols and their chemopreventive and therapeutic effects on colorectal cancer

Colorectal cancer (CRC), a multifactorial disease, is usually induced and developed through complex mechanisms, including impact of diet and lifestyle, genomic abnormalities, change of signaling pathways, inflammatory response, oxidation stress, dysbiosis, and so on. As natural polyphenolic phytochemicals that exist primarily in tea, tea polyphenols (TPs) have been shown to have many clinical applications, especially as anticancer agents. Most animal studies and epidemiological studies have demonstrated that TPs can prevent and treat CRC. TPs can inhibit the growth and metastasis of CRC by exerting the anti-inflammatory, anti-oxidative or pro-oxidative, and pro-apoptotic effects, which are achieved by modulations at multiple levels. Many experiments have demonstrated that TPs can modulate several signaling pathways in cancer cells, including the mitogen-activated protein kinase pathway, phosphatidylinositol-3 kinase/Akt pathway, Wnt/β-catenin pathway, and 67 kDa laminin receptor pathway, to inhibit proliferation and promote cell apoptosis. In addition, novel studies have also suggested that TPs can prevent the growth and metastasis of CRC by modulating the composition of gut microbiota to improve immune system and decrease inflammatory responses. Molecular pathological epidemiology, a novel multidisciplinary investigation, has made great progress on CRC, and the further molecular pathological epidemiology research should be developed in the field of TPs and CRC. This review summarizes the existing in vitro and in vivo animal and human studies and potential mechanisms to examine the effects of tea polyphenols on CRC.

Nomogram for predicting overall survival in stage II-III colorectal cancer

PURPOSE

The overall survival (OS) of patients diagnosed with stage II-III colorectal cancer (CRC) can vary greatly, even between patients with the same tumor stage. We aimed to design a nomogram to predict OS in resected, stage II-III CRC and stratify patients with CRC into different risk groups.

PATIENTS AND METHODS

Based on data from 873 patients with CRC, we used univariate Cox regression analysis to select the significant prognostic features, which were subjected to the least absolute shrinkage and selection operator (LASSO) regression algorithm for feature selection. Cross-validation was used to confirm suitable tuning parameters (λ) for LASSO logistic regression. Then, the nomogram was used to estimate 3- and 5-year OS based on the multivariable Cox regression model. The survival curves of the two groups were produced using the Kaplan-Meier method. Risk group stratification was performed to assess the predictive capacity of the nomogram.

RESULTS

Preoperative mean platelet volume, preoperative platelet distribution width, monocytes, and postoperative adjuvant chemotherapy were identified as independent prognostic factors by LASSO regression and integrated for the construction of the nomogram. The nomogram provided good discrimination, with C-indices of 0.67 and 0.69 for the training and validation sets, respectively. Calibration plots illustrated excellent agreement between the nomogram predictions and actual observations for 3- and 5-year OS. Moreover, a significant difference in OS was shown between patients stratified into different risk groups (P < .001).

CONCLUSION

We constructed and validated an original predictive nomogram for OS in patients with CRC after surgery, facilitating physicians to appraise the individual survival of postoperative patients accurately and identify high-risk patients who need more aggressive treatment and follow-up strategies.

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.

Gut Bacteria and their Metabolites: Which One Is the Defendant for Colorectal Cancer?

Colorectal cancer (CRC) is a worldwide health concern which requires efficient therapeutic strategies. The mechanisms underlying CRC remain an essential subject of investigations in the cancer biology field. The evaluation of human microbiota can be critical in this regard, since the disruption of the normal community of gut bacteria is an important issue in the development of CRC. However, several studies have already evaluated the different aspects of the association between microbiota and CRC. The current study aimed at reviewing and summarizing most of the studies on the modifications of gut bacteria detected in stool and tissue samples of CRC cases. In addition, the importance of metabolites derived from gut bacteria, their relationship with the microbiota, and epigenetic modifications have been evaluated.

The Role of the Gut Microbiota in Colorectal Cancer Causation

Here, we reviewed emerging evidence on the role of the microbial community in colorectal carcinogenesis. A healthy gut microbiota promotes intestinal homeostasis and can exert anti-cancer effects; however, this microbiota also produces a variety of metabolites that are genotoxic and which can negatively influence epithelial cell behaviour. Disturbances in the normal microbial balance, known as dysbiosis, are frequently observed in colorectal cancer (CRC) patients. Microbial species linked to CRC include certain strains of Bacteroides fragilis, Escherichia coli, Streptococcus gallolyticus, Enterococcus faecalis and Fusobacterium nucleatum, amongst others. Whether these microbes are merely passive dwellers exploiting the tumour environment, or rather, active protagonists in the carcinogenic process is the subject of much research. The incidence of chemically-induced tumours in mice models varies, depending upon the presence or absence of these microorganisms, thus strongly suggesting influences on disease causation. Putative mechanistic explanations differentially link these strains to DNA damage, inflammation, aberrant cell behaviour and immune suppression. In the future, modulating the composition and metabolic activity of this microbial community may have a role in prevention and therapy.

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.

Oral Bacteria and Intestinal Dysbiosis in Colorectal Cancer

The human organism coexists with its microbiota in a symbiotic relationship. These polymicrobial communities are involved in many crucial functions, such as immunity, protection against pathogens, and metabolism of dietary compounds, thus maintaining homeostasis. The oral cavity and the colon, although distant anatomic regions, are both highly colonized by distinct microbiotas. However, studies indicate that oral bacteria are able to disseminate into the colon. This is mostly evident in conditions such as periodontitis, where specific bacteria, namely Fusobacterium nucrelatum and Porphyromonas gingivalis project a pathogenic profile. In the colon these bacteria can alter the composition of the residual microbiota, in the context of complex biofilms, resulting in intestinal dysbiosis. This orally-driven disruption promotes aberrant immune and inflammatory responses, eventually leading to colorectal cancer (CRC) tumorigenesis. Understanding the exact mechanisms of these interactions will yield future opportunities regarding prevention and treatment of CRC.

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.

Crypt- and Mucosa-Associated Core Microbiotas in Humans and Their Alteration in Colon Cancer Patients

Due to the huge number of bacteria constituting the human colon microbiota, alteration in the balance of its constitutive taxa (i.e., dysbiosis) is highly suspected of being involved in colorectal oncogenesis. Indeed, bacterial signatures in association with CRC have been described. These signatures may vary if bacteria are identified in feces or in association with tumor tissues. Here, we show that bacteria colonize human colonic crypts in tissues obtained from patients with CRC and with normal colonoscopy results. Aerobic nonfermentative Proteobacteria previously identified as constitutive of the crypt-specific core microbiota in murine colonic samples are similarly prevalent in human colonic crypts in combination with other anaerobic taxa. We also show that bacterial signatures characterizing the crypts of colonic tumors vary depending whether right-side or left-side tumors are analyzed.

We have previously identified a crypt-specific core microbiota (CSCM) in the colons of healthy laboratory mice and related wild rodents. Here, we confirm that a CSCM also exists in the human colon and appears to be altered during colon cancer. The colonic microbiota is suggested to be involved in the development of colorectal cancer (CRC). Because the microbiota identified in fecal samples from CRC patients does not directly reflect the microbiota associated with tumor tissues themselves, we sought to characterize the bacterial communities from the crypts and associated adjacent mucosal surfaces of 58 patients (tumor and normal homologous tissue) and 9 controls with normal colonoscopy results. Here, we confirm that bacteria colonize human colonic crypts in both control and CRC tissues, and using laser-microdissected tissues and 16S rRNA gene sequencing, we further show that right and left crypt- and mucosa-associated bacterial communities are significantly different. In addition to Bacteroidetes and Firmicutes, and as with murine proximal colon crypts, environmental nonfermentative Proteobacteria are found in human colonic crypts. Fusobacterium and Bacteroides fragilis are more abundant in right-side tumors, whereas Parvimonas micra is more prevalent in left-side tumors. More precisely, Fusobacterium periodonticum is more abundant in crypts from cancerous samples in the right colon than in associated nontumoral samples from adjacent areas but not in left-side colonic samples. Future analysis of the interaction between these bacteria and the crypt epithelium, particularly intestinal stem cells, will allow deciphering of their possible oncogenic potential.

ETHE1 overexpression promotes SIRT1 and PGC1α mediated aerobic glycolysis, oxidative phosphorylation, mitochondrial biogenesis and colorectal cancer

Ethylmalonic Encephalopathy Protein 1 (ETHE1) is a sulfur dioxygenase that regulates cellular H2S levels. We previously demonstrated a significant increase of ETHE1 expression in "single-hit" colon epithelial cells from crypts of patients with Familial Adenomatous Polyposis (FAP). Here, we report elevated levels of ETHE1 expression and increased mitochondrial density occurring in-situ in phenotypically normal FAP colorectal mucosa. We also found that constitutive expression of ETHE1 increased aerobic glycolysis ("Warburg effect"), oxidative phosphorylation, and mitochondrial biogenesis in colorectal cancer (CRC) cell lines, thereby depleting H2S which relieved the inhibition of phosphodiesterase (PDE), and increased adenosine monophosphate (AMP) levels. This led to activation of the energy sensing AMP-activated protein kinase (AMPKp), Sirtuin1 (SIRT1) and peroxisome proliferator-activated receptor γ coactivator 1α (PGC1α), a master regulator of mitochondrial biogenesis. By contrast, shRNA silencing of ETHE1 reduced PDE activity, AMPKp/SIRT1/PGC1α levels and mitochondrial biogenesis. Constitutive expression of ETHE1 accelerated both CRC cell xenograft and orthotopic patient derived xenograft CRC cell growth in vivo. Overall, our data nominate elevated ETHE1 expression levels as a novel biomarker and potential therapeutic target for the prevention of CRC tumorigenesis.

Oral microbiota and gastrointestinal cancer

The microbiota inhabiting the oral cavity is a complex ecosystem and responsible for resisting pathogens, maintaining homeostasis, and modulating the immune system. Some components of the oral microbiota contribute to the etiology of some oral diseases. Accumulating evidence suggests that the human oral microbiota is implicated in the development and progression of gastrointestinal cancer. In this review, we described the current understanding of possible roles and mechanisms of oral microbiota in the gastrointestinal cancers studied to date. The perspectives for oral microbiota as the biomarkers for early detection and new therapeutic targets were also discussed.

Fusobacterium nucleatum Contributes to the Carcinogenesis of Colorectal Cancer by Inducing Inflammation and Suppressing Host Immunity

The presence of Fusobacterium nucleatum (F. nucleatum) in the gut is associated with the development of colorectal cancer (CRC). F. nucleatum promotes tumor development by inducing inflammation and host immune response in the CRC microenvironment. Adhesion to the intestinal epithelium by the cell surface proteins FadA, Fap2 and RadD expressed by F. nucleatum can cause the host to produce inflammatory factors and recruit inflammatory cells, creating an environment which favors tumor growth. Furthermore, F. nucleatum can induce immune suppression of gut mucosa by suppressing the function of immune cells such as macrophages, T cells and natural killer cells, contributing the progression of CRC.

Integration of microbiology, molecular pathology, and epidemiology: a new paradigm to explore the pathogenesis of microbiome-driven neoplasms

Molecular pathological epidemiology (MPE) is an integrative transdisciplinary field that addresses heterogeneous effects of exogenous and endogenous factors (collectively termed 'exposures'), including microorganisms, on disease occurrence and consequences, utilising molecular pathological signatures of the disease. In parallel with the paradigm of precision medicine, findings from MPE research can provide aetiological insights into tailored strategies of disease prevention and treatment. Due to the availability of molecular pathological tests on tumours, the MPE approach has been utilised predominantly in research on cancers including breast, lung, prostate, and colorectal carcinomas. Mounting evidence indicates that the microbiome (inclusive of viruses, bacteria, fungi, and parasites) plays an important role in a variety of human diseases including neoplasms. An alteration of the microbiome may be not only a cause of neoplasia but also an informative biomarker that indicates or mediates the association of an epidemiological exposure with health conditions and outcomes. To adequately educate and train investigators in this emerging area, we herein propose the integration of microbiology into the MPE model (termed 'microbiology-MPE'), which could improve our understanding of the complex interactions of environment, tumour cells, the immune system, and microbes in the tumour microenvironment during the carcinogenic process. Using this approach, we can examine how lifestyle factors, dietary patterns, medications, environmental exposures, and germline genetics influence cancer development and progression through impacting the microbial communities in the human body. Further integration of other disciplines (e.g. pharmacology, immunology, nutrition) into microbiology-MPE would expand this developing research frontier. With the advent of high-throughput next-generation sequencing technologies, researchers now have increasing access to large-scale metagenomics as well as other omics data (e.g. genomics, epigenomics, proteomics, and metabolomics) in population-based research. The integrative field of microbiology-MPE will open new opportunities for personalised medicine and public health. Copyright © 2019 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Bugs, drugs, and cancer: can the microbiome be a potential therapeutic target for cancer management?

Outnumbering our own cells over ten times, gut microbes can even be considered an additional organ. Several studies have explored the association between microbiomes and antitumor drug response. It has been reported that the presence of specific bacteria might modulate cancer progression and the efficacy of anticancer therapeutics. Bacteria-targeting intervention can provide crucial guidance for the design of next-generation antitumor drugs. Here, we review previous findings elucidating the impact of gut microbiomes on cancer treatment and the possible underlying mechanisms. In addition, we examine the role of microbiome manipulation in controlling tumor growth. Finally, we discuss concerns regarding the alteration of the microbiome composition, and the potential approaches to surpass existing limitations.

Insights into Pathogenic Interactions Among Environment, Host, and Tumor at the Crossroads of Molecular Pathology and Epidemiology

Evidence indicates that diet, nutrition, lifestyle, the environment, the microbiome, and other exogenous factors have pathogenic roles and also influence the genome, epigenome, transcriptome, proteome, and metabolome of tumor and nonneoplastic cells, including immune cells. With the need for big-data research, pathology must transform to integrate data science fields, including epidemiology, biostatistics, and bioinformatics. The research framework of molecular pathological epidemiology (MPE) demonstrates the strengths of such an interdisciplinary integration, having been used to study breast, lung, prostate, and colorectal cancers. The MPE research paradigm not only can provide novel insights into interactions among environment, tumor, and host but also opens new research frontiers. New developments-such as computational digital pathology, systems biology, artificial intelligence, and in vivo pathology technologies-will further transform pathology and MPE. Although it is necessary to address the rarity of transdisciplinary education and training programs, MPE provides an exemplary model of integrative scientific approaches and contributes to advancements in precision medicine, therapy, and prevention.

Proteomic characterization of outer membrane vesicles from gut mucosa-derived fusobacterium nucleatum

Fusobacterium nucleatum is a Gram-negative bacterium commonly found in the oral cavity and is often involved in periodontal diseases. Recent studies have shown increased F. nucleatum prevalence in colorectal cancer (CRC) tissues, and causal data has linked this bacterium to CRC tumorigenesis. Immune-based approaches to contain, reduce or eradicate its gut colonization may prevent CRC. Outer membrane vesicles (OMVs) are naturally produced by Gram-negative bacteria, typically contain multiple putative virulence factors and may elicit protective immune responses if used as vaccines. Here, OMVs were isolated from F. nucleatum cultures and purified using gradient centrifugation. Proteins contained within the OMVs were identified by nano LC/MS/MS analysis. Of 98 proteins consistently identified from duplicate analyses, 60 were predicted to localize to the outer membrane or periplasm via signal peptide driven translocation. Of these, six autotransporter proteins, which constitute the majority of protein mass of OMVs, were associated with Type V secretion system. In addition, other putative virulence factor proteins with functional domains, including FadA, MORN2 and YadA-like domain, were identified with multiple exposed epitope sites as determined by in silico analysis. Altogether, the non-replicative OMVs of F. nucleatum contain multiple antigenic virulence factors that may play important roles in the design and development of vaccines against F. nucleatum. SIGNIFICANCE: Fusobacterium nulceatum has been proved playing significant role in colorectal carcinogenesis. Outer membrane vesicles are nanoparticles that naturally secreted by Gram-negative bacterial containing various antigenic components, which provides new insight in vaccine development. Understanding the constituents of F. nucleatum OMVs will provide fundamental information and potential strategies for OMV-based F. nucleatum vaccines design. Based on our knowledge this is the first proteomic study of OMVs from F. nucleatum.

Progress in characterizing the linkage between Fusobacterium nucleatum and gastrointestinal cancer

Microbiome research is a rapidly advancing field in human cancers. Fusobacterium nucleatum is an oral bacterium, indigenous to the human oral cavity, that plays a role in periodontal disease. Recent studies have found that F. nucleatum can promote gastrointestinal tumor progression and affect the prognosis of the disease. In addition, F. nucleatum may contribute to the chemo-resistance of gastrointestinal cancers. This review summarizes recent progress in the pathogenesis of F. nucleatum and its impact on gastrointestinal cancer.

Gut Microbiota, Fusobacteria, and Colorectal Cancer

The gut microbiota has emerged as an environmental contributor to colorectal cancer (CRC) in both animal models and human studies. It is now generally accepted that bacteria are ubiquitous colonizers of all exposed human body surfaces, including the entire alimentary tract (5). Recently, the concept that a normal bacterial microbiota is essential for the development of inflammation-induced carcinoma has emerged from studies of well-known colonic bacterial microbiota. This review explores the evidence for a role of fusobacteria, an anaerobic gram-negative bacterium that has repeatedly been detected at colorectal tumor sites in higher abundance than surrounding histologically normal tissue. Mechanistic studies provide insight on the interplay between fusobacteria, other gut microbiota, barrier functions, and host responses. Studies have shown that fusobacteria activate host inflammatory responses designed to protect against pathogens that promote tumor growth. We discuss how future research identifying the pathophysiology underlying fusobacteria colon colonization during colorectal cancer may lead to new therapeutic targets for cancer. Furthermore, disease-protective strategies suppressing tumor development by targeting the local tumor environment via bacteria represent another exciting avenue for researchers and are highlighted in this review.

Diets That Promote Colon Inflammation Associate With Risk of Colorectal Carcinomas That Contain Fusobacterium nucleatum

BACKGROUND & AIMS

Specific nutritional components are likely to induce intestinal inflammation, which is characterized by increased levels of interleukin 6 (IL6), C-reactive protein (CRP), and tumor necrosis factor-receptor superfamily member 1B (TNFRSF1B) in the circulation and promotes colorectal carcinogenesis. The inflammatory effects of a diet can be estimated based on an empiric dietary inflammatory pattern (EDIP) score, calculated based on intake of 18 foods associated with plasma levels of IL6, CRP, and TNFRSF1B. An inflammatory environment in the colon (based on increased levels of IL6, CRP, and TNFRSF1B in peripheral blood) contributes to impairment of the mucosal barrier and altered immune cell responses, affecting the composition of the intestinal microbiota. Colonization by Fusobacterium nucleatum has been associated with the presence and features of colorectal adenocarcinoma. We investigated the association between diets that promote inflammation (based on EDIP score) and colorectal cancer subtypes classified by level of F nucleatum in the tumor microenvironment.

METHODS

We calculated EDIP scores based on answers to food frequency questionnaires collected from participants in the Nurses' Health Study (through June 1, 2012) and the Health Professionals Follow-up Study (through January 31, 2012). Participants in both cohorts reported diagnoses of rectal or colon cancer in biennial questionnaires; deaths from unreported colorectal cancer cases were identified through the National Death Index and next of kin. Colorectal tumor tissues were collected from hospitals where the patients underwent tumor resection and F nucleatum DNA was quantified by a polymerase chain reaction assay. We used multivariable duplication-method Cox proportional hazard regression to assess the associations of EDIP scores with risks of colorectal cancer subclassified by F nucleatum status.

RESULTS

During 28 years of follow-up evaluation of 124,433 participants, we documented 951 incident cases of colorectal carcinoma with tissue F nucleatum data. Higher EDIP scores were associated with increased risk of F nucleatum-positive colorectal tumors (P_trend = .03); for subjects in the highest vs lowest EDIP score tertiles, the hazard ratio for F nucleatum-positive colorectal tumors was 1.63 (95% CI, 1.03-2.58). EDIP scores did not associate with F nucleatum-negative tumors (P_trend = .44). High EDIP scores associated with proximal F nucleatum-positive colorectal tumors but not with proximal F nucleatum-negative colorectal tumors (P_{heterogeneity} = .003).

CONCLUSIONS

Diets that may promote intestinal inflammation, based on EDIP score, are associated with increased risk of F nucleatum-positive colorectal carcinomas, but not carcinomas that do not contain these bacteria. These findings indicate that diet-induced intestinal inflammation alters the gut microbiome to contribute to colorectal carcinogenesis; nutritional interventions might be used in precision medicine and cancer prevention.

Fusobacterium nucleatum in Colorectal Cancer Relates to Immune Response Differentially by Tumor Microsatellite Instability Status

The presence of Fusobacterium nucleatum (F. nucleatum) in colorectal carcinoma tissue has been associated with microsatellite instability (MSI), lower-level T-cell infiltrates, and poor clinical outcomes. Considering differences in the tumor-immune microenvironment between MSI-high and non-MSI-high carcinomas, we hypothesized that the association of F. nucleatum with immune response might differ by tumor MSI status. Using samples from 1,041 rectal and colon cancer patients within the Nurses' Health Study and Health Professionals Follow-up Study, we measured F. nucleatum DNA in tumor tissue by a quantitative polymerase chain reaction assay. Multivariable logistic regression models were used to examine the association between F. nucleatum status and histopathologic lymphocytic reactions or density of CD3⁺ cells, CD8⁺ cells, CD45RO (PTPRC)⁺ cells, or FOXP3⁺ cells in strata of tumor MSI status. We adjusted for potential confounders, including CpG island methylator phenotype; LINE-1 methylation; and KRAS, BRAF, and PIK3CA mutations. The association of F. nucleatum with tumor-infiltrating lymphocytes (TIL) and intratumoral periglandular reaction differed by tumor MSI status (P _interaction = 0.002). The presence of F. nucleatum was negatively associated with TIL in MSI-high tumors [multivariable odds ratio (OR), 0.45; 95% confidence interval (CI), 0.22-0.92], but positively associated with TIL in non-MSI-high tumors (multivariable OR 1.91; 95% CI, 1.12-3.25). No significant differential association was observed for peritumoral lymphocytic reaction, Crohn-like lymphoid reaction, or T-cell densities. In conclusion, the association of F. nucleatum with immune response to colorectal carcinoma differs by tumor MSI status, suggesting that F. nucleatum and MSI status interact to affect antitumor immune reactions. Cancer Immunol Res; 6(11); 1327-36. ©2018 AACR See related Spotlight on p. 1290.

Intestinal microbiota: a novel perspective in colorectal cancer biotherapeutics

It is believed that genetic factors, immune system dysfunction, chronic inflammation, and intestinal microbiota (IM) dysbiosis contribute to the pathogenesis of colorectal cancer (CRC). The beneficial role played by the direct regulation of IM in inflammatory bowel disease treatment is identified by the decreased growth of harmful bacteria and the increased production of anti-inflammatory factors. Interestingly, gut microbiota has been proven to inhibit tumor formation and progression in inflammation/carcinogen-induced CRC mouse models. Recently, evidence has indicated that IM is involved in the negative regulation of tumor immune response in tumor microenvironment, which then abolishes or accelerates anticancer immunotherapy in several tumor animals. In clinical trials, a benefit of IM-based CRC therapies in improving the intestinal immunity balance, epithelial barrier function, and quality of life has been reported. Meanwhile, specific microbiota signature can modulate host's sensitivity to chemo-/radiotherapy and the prognosis of CRC patients. In this review, we aim to 1) summarize the potential methods of IM-based therapeutics according to the recent results; 2) explore its roles and underlying mechanisms in combination with other therapies, especially in biotherapeutics; 3) discuss its safety, deficiency, and future perspectives.

Association between Fusobacterium nucleatum and colorectal cancer: Progress and future directions

The initiation and progression of colorectal cancer (CRC) involves genetic and epigenetic alterations influenced by dietary and environmental factors. Increasing evidence has linked the intestinal microbiota and colorectal cancer. More recently, Fusobacterium nucleatum (Fn), an opportunistic commensal anaerobe in the oral cavity, has been associated with CRC. Several research teams have reported an overabundance of Fn in human CRC and have elucidated the possible mechanisms by which Fn is involved in colorectal carcinogenesis in vitro and in mouse models. However, the mechanisms by which Fn promotes colorectal carcinogenesis remain unclear. To provide new perspectives for early diagnosis, the identification of high risk populations and treatment for colorectal cancer, this review will summarize the relative research progresses regarding the relationship between Fn and colorectal cancer.

Sex-specific differences in the occurrence of Fusobacterium nucleatum subspecies and Fusobacterium periodonticum in the oral cavity

The periodontitis-associated species Fusobacterium nucleatum (FN) has been implicated in several extra-oral diseases, including preterm birth and colorectal cancer. Due to its genetic and phenotypic heterogeneity, FN is classified in four subspecies which may differ in their disease potential. Here we compared the prevalence of FN subspecies and the close relative F. periodonticum (FP) via 16S rRNA gene analysis in saliva from 100 healthy individuals (60 females, and 40 males) from eleven countries spanning five continents. By focusing on the most abundant sequence types (i.e. analysis of approximately ten clone sequences each) the average number of FN/FP subspecies per individual differed significantly between females and males, i.e. 2.93 versus 2.5, respectively (P = 0.043). FN subsp. fusiforme/vincentii was significantly more prevalent in females vs males, with 2.85 vs. 1.68 sequence reads per individual, respectively (P = 0.012). A significant age-related difference was observed in females but not in males, i.e. 2.6 subspecies on average in females ≤ 30 years vs. 3.2 in females > 30 (P = 0.0076). Given the link between FN and systemic disorders our findings highlight the need for microbial studies at the subspecies level to further characterize the role of periodontal pathogens in diseases that affect females and males differently, e.g. colorectal cancer.

Understanding the microbiome: Emerging biomarkers for exploiting the microbiota for personalized medicine against cancer

The human body is a home to more than 1 trillion microbes with a diverse variety of commensal microbes that play a crucial role towards the health of the individual. These microbes occupy different habitats such as gut, skin, vagina, oral etc. Not only the types and abundance of microbes are different in different organs, but also these may differ in different individuals. The genome of these microbiota and their ecosystem constitute to form a microbiome. Factors such as diet, environment, host genetics etc. may be the reason behind the wide microbial diversity. A number of studies performed on human microbiome have revealed that microbiota present in healthy and diseased individuals are distinct. Altered microbiome is many a times the reason behind the overexpression of genes which may cause complex diseases including cancer. Manipulation of the human microbiome can be done by microbial supplements such as probiotics or synbiotics, diet or prebiotics and microbial suppression strategies using antibiotics. Recent advances in genome sequencing technologies and metagenomic analysis provide us the broader understanding of these commensal microbes and highlighting the distinctive features of microbiome during healthy and disease states. Molecular pathological epidemiology (MPE) studies have been very helpful in providing insights into the pathological process behind disease evolution and progression by determining the specific etiological factors. New emerging field of research targets the microbiome for therapeutic purposes by which personalized medicines can be made for treating various types of tumors. Screening programmes might be helpful in identifying patients who are at the verge of developing cancer and in delivering appropriate approaches according to individual risk modes so that disease could be prevented.

Fusobacterium's link to colorectal neoplasia sequenced: A systematic review and future insights

AIM

To critically evaluate previous scientific evidence on Fusobacterium's role in colorectal neoplasia development.

METHODS

Two independent investigators systematically reviewed all original scientific articles published between January, 2000, and July, 2017, using PubMed, EMBASE, and MEDLINE. A total of 355 articles were screened at the abstract level. Of these, only original scientific human, animal, and in vitro studies investigating Fusobacterium and its relationship with colorectal cancer (CRC) were included in the analysis. Abstracts, review articles, studies investigating other colonic diseases, and studies written in other languages than English were excluded from our analysis. Ninety articles were included after removing duplicates, resolving disagreements between the two reviewers, and applying the above criteria.

RESULTS

Studies have consistently identified positive associations between Fusobacterium, especially Fusobacterium nucleatum (F. nucleatum), and CRC. Stronger associations were seen in CRCs proximal to the splenic flexure and CpG island methylator phenotype (CIMP)-high CRCs. There was evidence of temporality and a biological gradient, with increased F. nucleatum DNA detection and quantity along the traditional adenoma-carcinoma sequence and in CIMP-high CRC precursors. Diet may have a differential impact on colonic F. nucleatum enrichment; evidence suggests that high fiber diet may reduce the risk of a subset of CRCs that are F. nucleatum DNA-positive. Data also suggest shorter CRC and disease-specific survival with increased amount of F. nucleatum DNA in CRC tissue. The pathophysiology of enrichment of F. nucleatum and other Fusobacterium species in colonic tissue is unclear; however, the virulence factors and changes to the local colonic environment with disruption of the protective mucus layer may contribute. The presence of a host lectin (Gal-GalNAc) in the colonic epithelium may also mediate F. nucleatum attachment to CRC and precursors through interaction with an F. nucleatum protein, fibroblast activation protein 2 (FAP2). The clinical significance of detection or enrichment of Fusobacterium in colorectal neoplasia is ambiguous, but data suggest a procarcinogenic effect of F. nucleatum, likely due to activation of oncogenic and inflammatory pathways and modulation of the tumor immune environment. This is hypothesized to be mediated by certain F. nucleatum strains carrying invasive properties and virulence factors such as FadA and FAP.

CONCLUSION

Evidence suggests a potential active role of Fusobacterium, specifically F. nucleatum, in CRC. Future prospective and experimental human studies would fill an important gap in this literature.

Microbiome, inflammation and colorectal cancer

Chronic inflammation is linked to the development of multiple cancers, including those of the colon. Inflammation in the gut induces carcinogenic mutagenesis and promotes colorectal cancer initiation. Additionally, myeloid and lymphoid cells infiltrate established tumors and propagate so called "tumor-elicited inflammation", which in turn favors cancer development by supporting the survival and proliferation of cancer cells. In addition to the interaction between cancer cells and tumor infiltrating immune cells, the gut also hosts trillions of bacteria and other microbes, whose roles in colorectal inflammation and cancer have only been appreciated in the past decade or so. Commensal and pathobiotic bacteria promote colorectal cancer development by exploiting tumor surface barrier defects following cancer initiation, by invading normal colonic tissue and inducing local inflammation, and by generating genotoxicity against colonic epithelial cells to accelerate their oncogenic transformation. On the other hand, a balanced population of microbiota is important for the prevention of colorectal cancer due to their roles in providing certain bacterial metabolites and inhibiting intestinal inflammation. In this review we summarize our current knowledge regarding the link between microbiota, inflammation, and colorectal cancer, and aim to delineate the mechanisms by which gut microbiome and inflammatory cytokines regulate colorectal tumorigenesis.