The Role of Fecal Fusobacterium nucleatum and pks+ Escherichia coli as Early Diagnostic Markers of Colorectal Cancer

Gut microbiota - bidirectional modulator: role in inflammatory bowel disease and colorectal cancer

The gut microbiota is a diverse ecosystem that significantly impacts human health and disease. This article focuses on how the gut microbiota interacts with inflammatory bowel diseases and colorectal tumors, especially through immune regulation. The gut microbiota plays a role in immune system development and regulation, while the body's immune status can also affect the composition of the microbiota. These microorganisms exert pathogenic effects or correct disease states in gastrointestinal diseases through the actions of toxins and secretions, inhibition of immune responses, DNA damage, regulation of gene expression, and protein synthesis. The microbiota and its metabolites are essential in the development and progression of inflammatory bowel diseases and colorectal tumors. The complexity and bidirectionality of this connection with tumors and inflammation might render it a new therapeutic target. Hence, we explore therapeutic strategies for the gut microbiota, highlighting the potential of probiotics and fecal microbiota transplantation to restore or adjust the microbial community. Additionally, we address the challenges and future research directions in this area concerning inflammatory bowel diseases and colorectal tumors.

Small Intestinal Bacterial and Fungal Overgrowth: Health Implications and Management Perspectives

BACKGROUND/OBJECTIVES

Small Intestinal Bacterial Overgrowth (SIBO) and Small Intestinal Fungal Overgrowth (SIFO) are distinct yet often overlapping conditions characterized by an abnormal increase in microbial populations within the small intestine. SIBO results from an overgrowth of colonic bacteria, while SIFO is driven by fungal overgrowth, primarily involving Candida species. Both conditions present with nonspecific gastrointestinal (GI) symptoms such as bloating, abdominal pain, diarrhea, and malabsorption, making differentiation between SIBO and SIFO challenging. This review aims to elucidate the underlying mechanisms, risk factors, diagnostic challenges, and management strategies associated with SIBO and SIFO.

METHODS

A comprehensive review of current literature was conducted, focusing on the pathophysiology, diagnostic modalities, and therapeutic approaches for SIBO and SIFO.

RESULTS

SIBO is commonly associated with factors such as reduced gastric acid secretion, impaired gut motility, and structural abnormalities like bowel obstruction and diverticula. It is frequently diagnosed using jejunal aspirates (≥105 colony forming units (CFUs)/mL) or breath tests. In contrast, SIFO is linked to prolonged antibiotic use, immunosuppression, and gut microbiome dysbiosis, with diagnosis relying on fungal cultures from small intestinal aspirates due to the absence of standardized protocols.

CONCLUSION

The clinical overlap and frequent misdiagnosis of SIBO and SIFO highlight the need for improved diagnostic tools and a multidisciplinary approach to management. This review emphasizes the importance of understanding the mechanisms behind SIBO and SIFO, how they relate to other health outcomes, and potential management strategies to optimize patient care and therapeutic outcomes.

Microbial dynamics of acute pancreatitis: integrating culture, sequencing, and bile impact on bacterial populations and gaseous metabolites

Background

Our study examined the composition of the intestinal microflora in a hospitalized patient with AP symptoms treated several months earlier for diverticulitis. The therapeutic intervention necessitated Hartmann's procedure, culminating in colostomy creation.

Aims

Employing a thorough microbiological analysis we attempted to demonstrate whether the microflora isolated from the peripancreatic fluid exhibited a stronger correlation with the contents of the stoma or with the rectal swab. Additionally, we sought to determine the association between later onset of AP and diverticulitis.

Methods

Following clinical materials from the patient in the initial phase of AP were collected: rectal swab, colostomy bag contents (in the publication referred to as stoma content/stool) and peripancreatic fluid. Microbiological analysis was performed, including classic culture methodology, NGS techniques, and genotyping methodologies. Furthermore, the effect of bile on the shift in the population of selected bacterial species was examined.

Results

The NGS technique confirmed greater consistency in bacteria percentage (phyla/family) between stoma content and peripancreatic fluid. In both samples, a clear dominance of the Proteobacteria phyla (over 75%) and the Enterobacteriaceae family was demonstrated. Moreover, NGS verified the presence of the Fusobacteriota phylum and Fusobacteriaceae family only in rectal swabs, which may indicate a link between this type of bacteria and the etiology of diverticulitis. We observed that Escherichia coli 33 isolated from stool exhibited active gaseous metabolite production (mainly hydrogen).

Conclusions

The abundant production of hydrogen may substantially impact enzymatic processes, inducing specific alterations in disulfide bonds and trypsin inactivation. Our investigation alludes to the conceivable active involvement of bile in effecting qualitative and quantitative modifications in the peripancreatic microbiota composition, establishing a correlation between released bile and bacterial generation of gaseous metabolites.

Global prevalence of Fusobacterium nucleatum and Bacteroides fragilis in patients with colorectal cancer: an overview of case reports/case series and meta-analysis of prevalence studies

BACKGROUND

Colorectal cancer (CRC) is the second deadliest carcinoma across the globe and has been known as a multi-factor induced-disease. Emerging research have demonstrated that bacterial colonization may contribute to the initiation and promotion of the CRC. The presence of Fusobacterium nucleatum (F. nucleatum) and Bacteroides fragilis (B. fragilis) in the gut is associated with the development of CRC. In this study, the prevalence of F. nucleatum and B. fragilis among CRC patients has been assessed worldwide through a systematic review and meta-analysis.

METHODS

The extensive search was performed using "Fusobacterium nucleatum", "Bacteroides fragilis", "Colorectal cancer" and all relevant keywords. Then, a systematic paper screening was done following a comprehensive search in Embase, Web of Science, and PubMed databases while the time range was limited between the years 2000 and 2024. Afterwards, statistical analysis was performed utilizing the comprehensive meta-analysis (CMA) software (version 2.0, Biostat, USA).

RESULTS

According to the meta-analysis of prevalence studies, the prevalence of F. nucleatum among 19 countries and B. fragilis among 10 countries were indicated to be 38.9% (95% CI 33.7-44.3%) and 42.5% (95% CI 34.4-51.1%), respectively, among the CRC patients. It was then revealed that Asia had the highest prevalence of F. nucleatum while most of the B. fragilis isolates in CRC cases were reported in European countries. Moreover, the data suggested that the most common comorbidity observed among the CRC cases was diabetes.

CONCLUSION

Our results emphasized the high prevalence of F. nucleatum and B. fragilis in CRC patients. Based on this meta-analysis review, regulating the gut microbiota in CRC patients seemed to be a promising approach to improving the efficacy of CRC therapy.

The relationship between pathogenic bacteria and different stages of colorectal cancer

Colorectal cancer (CRC) involves uncontrolled cell growth in the colon and rectum. This study aims to explore the prevalence of key pathogenic bacteria and their role in the progression of CRC, focusing on microbial dysbiosis. This study analyzed 52 stool and tissue samples through polymerase chain reaction (PCR), real-time PCR, and bioinformatics to identify associations between pathogenic bacteria and CRC progression. PCR results revealed a significant association between the Bacteroides fragilis toxin (bft) gene and CRC progression (P = 0.001, r = 0.570). Furthermore, Real-time PCR showed significant differences in the frequency of pks+Escherichia coli in CRC stages 1 (P = 0.03), 2 (P = 0.004), and 3 (P = 0.0002) compared to the control group. Additionally, the frequency of Fusobacterium nucleatum in stage 3 CRC patients was significantly higher than in the control group (P = 0.004) and stage 1 patients (P = 0.01). Furthermore, Streptococcus gallolyticus showed similar significant differences in stage 3 patients (P = 0.004). Bioinformatics analyses using KEGG, Reactome, STRING, and dbSNP highlighted bacteria's roles in colorectal carcinogenesis, emphasizing the need for early identification and management in CRC treatment and prevention strategies. Finally, due to the limitations of the study, the use of more advanced methods and the validation of results through more reliable techniques are essential for future research.

Fusobacterium nucleatum in tumors: from tumorigenesis to tumor metastasis and tumor resistance

Fusobacterium nucleatum, an anaerobic Gram-negative bacterium primarily residing in the oral cavity, has garnered significant attention for its emerging role in cancer progression and prognosis. While extensive research has revealed mechanistic links between Fusobacterium nucleatum and colorectal cancer, a comprehensive review spanning its presence and metastatic implications in cancers beyond colorectal origin is conspicuously absent. This paper broadens our perspective from colorectal cancer to various malignancies associated with Fusobacterium nucleatum, including oral, pancreatic, esophageal, breast, and gastric cancers. Our central focus is to unravel the mechanisms governing Fusobacterium nucleatum colonization, initiation, and promotion of metastasis across diverse cancer types. Additionally, we explore Fusobacterium nucleatum's adverse impacts on cancer therapies, particularly within the domains of immunotherapy and chemotherapy. Furthermore, this paper underscores the clinical research significance of Fusobacterium nucleatum as a potential tumor biomarker and therapeutic target, offering a novel outlook on its applicability in cancer detection and prognostic assessment.

Intratumoral Fusobacterium nucleatum in Pancreatic Cancer: Current and Future Perspectives

The intratumoral microbiome plays a significant role in many cancers, such as lung, pancreatic, and colorectal cancer. Pancreatic cancer (PC) is one of the most lethal malignancies and is often diagnosed at advanced stages. Fusobacterium nucleatum (Fn), an anaerobic Gram-negative bacterium primarily residing in the oral cavity, has garnered significant attention for its emerging role in several extra-oral human diseases and, lately, in pancreatic cancer progression and prognosis. It is now recognized as oncobacterium. Fn engages in pancreatic tumorigenesis and metastasis through multifaceted mechanisms, including immune response modulation, virulence factors, control of cell proliferation, intestinal metabolite interactions, DNA damage, and epithelial-mesenchymal transition. Additionally, compelling research suggests that Fn may exert detrimental effects on cancer treatment outcomes. This paper extends the perspective to pancreatic cancer associated with Fn. The central focus is to unravel the oncogenomic changes driven by Fn in colonization, initiation, and promotion of pancreatic cancer development. The presence of Fusobacterium species can be considered a prognostic marker of PC, and it is also correlated to chemoresistance. Furthermore, this review underscores the clinical research significance of Fn as a potential tumor biomarker and therapeutic target, offering a novel outlook on its applicability in cancer detection and prognostic assessment. It is thought that given the role of Fn in tumor formation and metastasis processes via its FadA, FapA, Fap2, and RadD, new therapies for tumor treatment targeting Fn will be developed.

Impact of metallic nanoparticles on gut microbiota modulation in colorectal cancer: A review

Colorectal cancer (CRC) is the third most prevalent cancer. Ongoing research aims to uncover the causes of CRC, with a growing focus on the role of gut microbiota (GM) in carcinogenesis. The GM influences CRC development, progression, treatment efficacy, and therapeutic toxicities. For example, Fusobacterium nucleatum and Escherichia coli can regulate microbial gene expression through the incorporation of human small noncode RNA and potentially contribute to cancer progression. Metallic nanoparticles (MNPs) have both negative and positive impacts on GM, depending on their type. Several studies state that titanium dioxide may increase the diversity, richness, and abundance of probiotics bacteria, whereas other studies demonstrate dose-dependent GM dysbiosis. The MNPs offer cytotoxicity through the modulation of MAPK signaling pathways, NF-kB signaling pathways, PI3K/Akt signaling pathways, extrinsic signaling pathways, intrinsic apoptosis, and cell cycle arrest at G1, G2, or M phase. MNPs enhance drug delivery, enable targeted therapy, and may restore GM. However, there is a need to conduct well-designed clinical trials to assess the toxicity, safety, and effectiveness of MNPs-based CRC therapies.

The role of gut microbial β-glucuronidases in carcinogenesis and cancer treatment: a scoping review

INTRODUCTION

The human gut microbiota influence critical functions including the metabolism of nutrients, xenobiotics, and drugs. Gut microbial β-glucuronidases (GUS) enzymes facilitate the removal of glucuronic acid from various compounds, potentially affecting anti-cancer drug efficacy and reactivating carcinogens. This review aims to comprehensively analyze and summarize studies on the role of gut microbial GUS in cancer and its interaction with anti-cancer treatments. Its goal is to collate and present insights that are directly relevant to patient care and treatment strategies in oncology.

METHODS

This scoping review followed PRISMA-ScR guidelines and focused on primary research exploring the role of GUS within the gut microbiota related to cancer etiology and anti-cancer treatment. Comprehensive literature searches were conducted in PubMed, Embase, and Web of Science.

RESULTS

GUS activity was only investigated in colorectal cancer (CRC), revealing increased fecal GUS activity, variations in the gut microbial composition, and GUS-contributing bacterial taxa in CRC patients versus controls. Irinotecan affects gastrointestinal (GI) health by increasing GUS expression and shifting gut microbial composition, particularly by enhancing the presence of GUS-producing bacteria, correlating with irinotecan-induced GI toxicities. GUS inhibitors (GUSi) can mitigate irinotecan's adverse effects, protecting the intestinal barrier and reducing diarrhea.

CONCLUSION

To our knowledge, this is the first review to comprehensively analyze and summarize studies on the critical role of gut microbial GUS in cancer and anti-cancer treatment, particularly irinotecan. It underscores the potential of GUSi to reduce side effects and enhance treatment efficacy, highlighting the urgent need for further research to integrate GUS targeting into future anti-cancer treatment strategies.

Escherichia coli on colorectal cancer: A two-edged sword

Escherichia coli (E. coli) is a ubiquitous symbiotic bacterium in the gut, and the diversity of E. coli genes determines the diversity of its functions. In this review, the two-edged sword theory was innovatively proposed. For the question 'how can we harness the ambivalent nature of E. coli to screen and treat CRC?', in terms of CRC screening, the variations in the abundance and subtypes of E. coli across different populations present an opportunity to utilise it as a biomarker, while in terms of CRC treatment, the natural beneficial effect of E. coli on CRC may be limited, and engineered E. coli, particularly certain subtypes with probiotic potential, can indeed play a significant role in CRC treatment. It seems that the favourable role of E. coli as a genetic tool lies not in its direct impact on CRC but its potential as a research platform that can be integrated with various technologies such as nanoparticles, imaging methods, and synthetic biology modification. The relationship between gut microflora and CRC remains unclear due to the complex diversity and interaction of gut microflora. Therefore, the application of E. coli should be based on the 'One Health' view and take the interactions between E. coli and other microorganisms, host, and environmental factors, as well as its own changes into account. In this paper, the two-edged sword role of E. coli in CRC is emphasised to realise the great potential of E. coli in CRC screening and treatment.

Research progress on the correlation between intestinal flora and colorectal cancer

Colorectal cancer (CRC) is one of the most common gastrointestinal malignancies in the world. With the rapid pace of life and changes in diet structure, the incidence and mortality of CRC increase year by year posing a serious threat to human health. As the most complex and largest microecosystem in the human body, intestinal microecology is closely related to CRC. It is an important factor that affects and participates in the occurrence and development of CRC. Advances in next-generation sequencing technology and metagenomics have provided new insights into the ecology of gut microbes. It also helps to link intestinal flora with CRC, and the relationship between intestinal flora and CRC can be continuously understood from different levels. This paper summarizes the relationship between intestinal flora and CRC and its potential role in the diagnosis of CRC providing evidence for early screening and treatment of CRC.

Rapid detection of FadA in Fusobacterium nucleatum using the quantitative LAMP colorimetric phenol red method in stool samples from colorectal cancer patients

The study aimed to develop a quantitative colorimetric loop-mediated isothermal amplification technique using the phenol red indicator (QLAMP-PhR) for detecting Fusobacterium nucleatum (Fn) levels in colorectal cancer (CRC) patients and healthy individuals. QLAMP-PhR assays were conducted on 251 stool samples specific for the Fn FadA gene. Six primers were synthesized and utilized with master mix reagents, and a phenol red indicator was employed to enhance the QLAMP-PhR technique. A standard quantitative analysis curve was generated using a logarithmic function (absorbance vs. concentration) by serially diluting the copy number of genomic DNA templates (Fn ATCC25586). The CRC group exhibited a significantly higher abundance of Fn compared to the healthy control group (P < 0.001). These findings suggest that the QLAMP-PhR technique effectively identifies Fn specifically by its gene for the key virulence factor FadA. Additionally, ideas for developing a real-time QLAMP-PhR test were presented. Compared to the traditional polymerase chain reaction (PCR) technique, QLAMP-PhR offers several advantages including rapidity, simplicity, specificity, sensitivity, and cost-effectiveness method that can quantitatively screen for Fn presence in normal populations. The QLAMP-PhR method represents a sensitive and specific amplification assay for the rapid detection of the Fn pathogen. To the best of our knowledge, this study is the first to report the application of QLAMP-PhR for detecting FadA in Fn.

Polyketide synthase positive Escherichia coli one-time measurement in stool is not informative of colorectal cancer risk in a screening setting

Environmental factors like the pathogenicity island polyketide synthase positive (pks+) Escherichia coli (E. coli) could have potential for risk stratification in colorectal cancer (CRC) screening. The association between pks+ E. coli measured in fecal immunochemical test (FIT) samples and the detection of advanced neoplasia (AN) at colonoscopy was investigated. Biobanked FIT samples were analyzed for both presence of E. coli and pks+ E. coli and correlated with colonoscopy findings; 5020 CRC screening participants were included. Controls were participants in which no relevant lesion was detected because of FIT-negative results (cut-off ≥15 μg Hb/g feces), a negative colonoscopy, or a colonoscopy during which only a nonadvanced polyp was detected. Cases were participants with AN [CRC, advanced adenoma (AA), or advanced serrated polyp (ASP)]. Existing DNA isolation and quantitative polymerase chain reaction (qPCR) procedures were used for the detection of E. coli and pks+ E. coli in stool. A total of 4542 (90.2%) individuals were E. coli positive, and 1322 (26.2%) were pks+ E. coli positive. The prevalence of E. coli in FIT samples from individuals with AN was 92.9% compared to 89.7% in FIT samples of controls (p = 0.010). The prevalence of pks+ E. coli in FIT samples from individuals with AN (28.6%) and controls (25.9%) was not significantly different (p = 0.13). The prevalences of pks+ E. coli in FIT samples from individuals with CRC, AA, or ASP were 29.6%, 28.3%, and 32.1%, respectively. In conclusion, the prevalence of pks+ E. coli in a screening population was 26.2% and did not differ significantly between individuals with AN and controls. These findings disqualify the straightforward option of using a snapshot measurement of pks+ E. coli in FIT samples as a stratification biomarker for CRC risk. © 2024 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Ubiquitinomics revealed disease- and stage-specific patterns relevant for the 3PM approach in human sigmoid colon cancers

Objective

The patients with sigmoid colorectal cancer commonly show high mortality and poor prognosis. Increasing evidence has demonstrated that the ubiquitinated proteins and ubiquitination-mediated molecular pathways influence the growth and aggressiveness of colorectal cancer. It emphasizes the scientific merits of quantitative ubiquitinomics in human sigmoid colon cancer. We hypothesize that the ubiquitinome and ubiquitination-mediated pathway networks significantly differ in sigmoid colon cancers compared to controls, which offers the promise for in-depth insight into molecular mechanisms, discovery of effective therapeutic targets, and construction of reliable biomarkers in the framework of predictive, preventive, and personalized medicine (PPPM; 3P medicine).

Methods

The first ubiquitinome analysis was performed with anti-K-ε-GG antibody beads (PTMScan ubiquitin remnant motif [K-ε-GG])-based label-free quantitative proteomics and bioinformatics to identify and quantify ubiquitination profiling between sigmoid colon cancer tissues and para-carcinoma tissues. A total of 100 human sigmoid colon cancer samples that included complete clinical information and the corresponding gene expression data were obtained from The Cancer Genome Atlas (TCGA). Ubiquitination was the main way of protein degradation; the relationships between differentially ubiquitinated proteins (DUPs) and their differently expressed genes (DEGs) and between DUPs and their differentially expressed proteins (DEPs) were analyzed between cancer tissues and control tissues. The overall survival of those DUPs was obtained with Kaplan-Meier method.

Results

A total of 1249 ubiquitinated sites within 608 DUPs were identified in human sigmoid colon cancer tissues. KEGG pathway network analysis of these DUPs revealed 35 statistically significant signaling pathways, such as salmonella infection, glycolysis/gluconeogenesis, and ferroptosis. Gene Ontology (GO) analysis of 608 DUPs revealed that protein ubiquitination was involved in 98 biological processes, 64 cellular components, 51 molecule functions, and 26 immune system processes. Protein-protein interaction (PPI) network of 608 DUPs revealed multiple high-combined scores and co-expressed DUPs. The relationship analysis between DUPs and their DEGs found 4 types of relationship models, including DUP-up (increased ubiquitination level) and DEG-up (increased gene expression), DUP-up and DEG-down (decreased gene expression), DUP-down (decreased ubiquitination level) and DEG-up, and DUP-down and DEG-down. The relationship analysis between DUPs and their DEPs found 4 types of relationship models, including DUP-up and DEP-up (increased protein expression), DUP-up and DEP-down (decreased protein expression), DUP-down and DEP-up, and DUP-down and DEP-down. Survival analysis found 46 overall survival-related DUPs in sigmoid colon cancer, and the drug sensitivity of overall survival-related DUPs were identified.

Conclusion

The study provided the first differentially ubiquitinated proteomic profiling, ubiquitination-involved signaling pathway network changes, and the relationship models between protein ubiquitination and its gene expression and between protein ubiquitination and its protein expression, in human sigmoid colon cancer. It offers the promise for deep insights into molecular mechanisms of sigmoid colon cancer, and discovery of effective therapeutic targets and biomarkers for patient stratification, predictive diagnosis, prognostic assessment, and personalized treatment in the context of 3P medicine.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13167-023-00328-2.

Association of cigarette smoking with risk of colorectal cancer subtypes classified by gut microbiota

INTRODUCTION

Both cigarette smoking and gut microbiota play important roles in colorectal carcinogenesis. We explored whether the association between smoking and colorectal cancer (CRC) risk varies by gut microbial enterotypes and how smoking-related enterotypes promote colorectal carcinogenesis.

METHODS

A case-control study was conducted. Fecal microbiota was determined by 16S rDNA sequencing. The cases with CRC or adenoma were subclassified by gut microbiota enterotypes. Multivariate analyses were used to test associations between smoking and the odds of colorectal neoplasm subtypes. Mann-Whitney U tests were used to find differential genera, genes, and pathways between the subtypes.

RESULTS

Included in the study were 130 CRC patients (type I: n=77; type II: n=53), 120 adenoma patients (type I: n=66; type II: n=54), and 130 healthy participants. Smoking increased the odds for type II tumors significantly (all p for trend <0.05) but not for type I tumors. The associations of smoking with increased odds of colorectal neoplasm significantly differed by gut microbiota enterotypes (p<0.05 for heterogeneity). An increase in carcinogenic bacteria (genus Escherichia shigella) and a decrease in probiotics (family Lachnospiraceae and Ruminococcaceae) in type II tumors may drive disease progression by upregulating oncogenic signaling pathways and inflammatory/oxidative stress response pathways, as well as protein phospholipase D1/2, cytochrome C, and prostaglandin-endoperoxide synthase 2 expression.

CONCLUSIONS

Smoking was associated with a higher odds of type II colorectal neoplasms but not type I tumors, supporting a potential role for the gut microbiota in mediating the association between smoking and colorectal neoplasms.

Progress of gut microbiome and its metabolomics in early screening of colorectal cancer

Gut microbes are widely considered to be closely associated with colorectal cancer (CRC) development. The microbiota is regarded as a potential identifier of CRC, as several studies have found great significant changes in CRC patients' microbiota and metabolic groups. Changes in microbiota, like Fusobacterium nucleatum and Bacteroides fragilis, also alter the metabolic activity of the host, promoting CRC development. In contrast, the metabolome is an intuitive discriminative biomarker as a small molecular bridge to distinguish CRC from healthy individuals due to the direct action of microbes on the host. More diagnostic microbial markers have been found, and the potential discriminatory power of microorganisms in CRC has been investigated through the combined use of biomic genomic metabolomics, bringing new ideas for screening fecal microbial markers. In this paper, we discuss the potential of microorganisms and their metabolites as biomarkers in CRC screening, hoping to provide thoughts and references for non-invasive screening of CRC.

Gut microbiota in colorectal cancer development and therapy

Colorectal cancer (CRC) is one of the commonest cancers globally. A unique aspect of CRC is its intimate association with the gut microbiota, which forms an essential part of the tumour microenvironment. Research over the past decade has established that dysbiosis of gut bacteria, fungi, viruses and Archaea accompanies colorectal tumorigenesis, and these changes might be causative. Data from mechanistic studies demonstrate the ability of the gut microbiota to interact with the colonic epithelia and immune cells of the host via the release of a diverse range of metabolites, proteins and macromolecules that regulate CRC development. Preclinical and some clinical evidence also underscores the role of the gut microbiota in modifying the therapeutic responses of patients with CRC to chemotherapy and immunotherapy. Herein, we summarize our current understanding of the role of gut microbiota in CRC and outline the potential translational and clinical implications for CRC diagnosis, prevention and treatment. Emphasis is placed on how the gut microbiota could now be better harnessed by developing targeted microbial therapeutics as chemopreventive agents against colorectal tumorigenesis, as adjuvants for chemotherapy and immunotherapy to boost drug efficacy and safety, and as non-invasive biomarkers for CRC screening and patient stratification. Finally, we highlight the hurdles and potential solutions to translating our knowledge of the gut microbiota into clinical practice.

Fecal microbiota transplantation inhibits colorectal cancer progression: Reversing intestinal microbial dysbiosis to enhance anti-cancer immune responses

Many lines of evidence demonstrate the associations of colorectal cancer (CRC) with intestinal microbial dysbiosis. Recent reports have suggested that maintaining the homeostasis of microbiota and host might be beneficial to CRC patients, but the underlying mechanisms remain unclear. In this study, we established a CRC mouse model of microbial dysbiosis and evaluated the effects of fecal microbiota transplantation (FMT) on CRC progression. Azomethane and dextran sodium sulfate were used to induce CRC and microbial dysbiosis in mice. Intestinal microbes from healthy mice were transferred to CRC mice by enema. The vastly disordered gut microbiota of CRC mice was largely reversed by FMT. Intestinal microbiota from normal mice effectively suppressed cancer progression as assessed by measuring the diameter and number of cancerous foci and significantly prolonged survival of the CRC mice. In the intestine of mice that had received FMT, there were massive infiltration of immune cells, including CD8⁺ T and CD49b⁺ NK, which is able to directly kill cancer cells. Moreover, the accumulation of immunosuppressive cells, Foxp3⁺ Treg cells, seen in the CRC mice was much reduced after FMT. Additionally, FMT regulated the expressions of inflammatory cytokines in CRC mice, including down-regulation of IL1a, IL6, IL12a, IL12b, IL17a, and elevation of IL10. These cytokines were positively correlated with Azospirillum_sp._47_25, Clostridium_sensu_stricto_1, the E. coli complex, Akkermansia, Turicibacter, and negatively correlated with Muribaculum, Anaeroplasma, Candidatus_Arthromitus, and Candidatus Saccharimonas. Furthermore, the repressed expressions of TGFb, STAT3 and elevated expressions of TNFa, IFNg, CXCR4 together promoted the anti-cancer efficacy. Their expressions were positively correlated with Odoribacter, Lachnospiraceae-UCG-006, Desulfovibrio, and negatively correlated with Alloprevotella, Ruminococcaceae UCG-014, Ruminiclostridium, Prevotellaceae UCG-001 and Oscillibacter. Our studies indicate that FMT inhibits the development of CRC by reversing gut microbial disorder, ameliorating excessive intestinal inflammation and cooperating with anti-cancer immune responses.

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.

A systematic review of microbiome-derived biomarkers for early colorectal cancer detection

Increasing evidence suggests a role of the gut microbiome in the development of colorectal cancer (CRC) and that it can serve as a biomarker for early diagnosis. This review aims to give an overview of the current status of published studies regarding the microbiome as a screening tool for early CRC detection. A literature search was conducted using PubMed and EMBASE in August 2022. Studies assessing the efficacy of microbiome-derived biomarkers based on noninvasive derived samples were included. Not relevant studies or studies not specifying the stage of CRC or grouping them together in the analysis were excluded. The risk of bias for screening tools was performed using the QUADAS-2 checklist. A total of 28 studies were included, ranging from 2 to 462 for CRC and 18 to 665 advanced adenoma patient inclusions, of which only two investigated the co-metabolome as biomarker. The diagnostic performance of faecal bacteria-derived biomarkers had an AUC ranging from 0.28-0.98 for precursor lesions such as advanced adenomas and 0.54-0.89 for early CRC. Diagnostic performance based on the co-metabolome showed an AUC ranging from 0.69 - 0.84 for precursor lesions and 0.65 - 0.93 for early CRC. All models improved when combined with established clinical early detection markers such as gFOBT. A high level of heterogeneity was seen in the number of inclusions and methodology used in the studies. The faecal and oral gut microbiome has the potential to complement existing CRC screening tools, however current evidence suggests that this is not yet ready for routine clinical use.

Gut microbiota, inflammatory bowel disease and colorectal cancer

The gut microbiota is a complex community of microorganisms that inhabit the digestive tracts of humans, living in symbiosis with the host. Dysbiosis, characterized by an imbalance between the beneficial and opportunistic gut microbiota, is associated with several gastrointestinal disorders, such as irritable bowel syndrome (IBS); inflammatory bowel disease (IBD), represented by ulcerative colitis and Crohn's disease; and colorectal cancer (CRC). Dysbiosis can disrupt the mucosal barrier, resulting in perpetuation of inflammation and carcinogenesis. The increase in some specific groups of harmful bacteria, such as Escherichia coli (E. coli) and enterotoxigenic Bacteroides fragilis (ETBF), has been associated with chronic tissue inflammation and the release of pro-inflammatory and carcinogenic mediators, increasing the chance of developing CRC, following the inflammation-dysplasia-cancer sequence in IBD patients. Therefore, the aim of the present review was to analyze the correlation between changes in the gut microbiota and the development and maintenance of IBD, CRC, and IBD-associated CRC. Patients with IBD and CRC have shown reduced bacterial diversity and abundance compared to healthy individuals, with enrichment of Firmicute sand Bacteroidetes. Specific bacteria are also associated with the onset and progression of CRC, such as Fusobacterium nucleatum, E. coli, Enterococcus faecalis, Streptococcus gallolyticus, and ETBF. Future research can evaluate the advantages of modulating the gut microbiota as preventive measures in CRC high-risk patients, directly affecting the prognosis of the disease and the quality of life of patients.

Bacterial Involvement in Progression and Metastasis of Colorectal Neoplasia

While the gut microbiome is composed of numerous bacteria, specific bacteria within the gut may play a significant role in carcinogenesis, progression, and metastasis of colorectal carcinoma (CRC). Certain microbial species are known to be associated with specific cancers; however, the interrelationship between bacteria and metastasis is still enigmatic. Mounting evidence suggests that bacteria participate in cancer organotropism during solid tumor metastasis. A critical review of the literature was conducted to better characterize what is known about bacteria populating a distant site and whether a tumor depends upon the same microenvironment during or after metastasis. The processes of carcinogenesis, tumor growth and metastatic spread in the setting of bacterial infection were examined in detail. The literature was scrutinized to discover the role of the lymphatic and venous systems in tumor metastasis and how microbes affect these processes. Some bacteria have a potent ability to enhance epithelial-mesenchymal transition, a critical step in the metastatic cascade. Bacteria also can modify the microenvironment and the local immune profile at a metastatic site. Early targeted antibiotic therapy should be further investigated as a measure to prevent metastatic spread in the setting of bacterial infection.