Association between intraepithelial Escherichia coli and colorectal cancer

Therapeutic potential of fecal microbiota transplantation in colorectal cancer based on gut microbiota regulation: from pathogenesis to efficacy

Colorectal cancer (CRC) remains a leading cause of cancer-related deaths worldwide, with its progression intricately linked to gut microbiota dysbiosis. Disruptions in microbial homeostasis contribute to tumor initiation, immune suppression, and inflammation, establishing the microbiota as a key therapeutic target. Fecal microbiota transplantation (FMT) has emerged as a transformative approach to restore microbial balance, enhance immune responses, and reshape the tumor microenvironment. This review explores the mechanisms underlying FMT's therapeutic potential, evaluates its advantages over other microbiota-based interventions, and addresses challenges such as donor selection, safety concerns, and treatment standardization. Looking forward, the integration of FMT into personalized CRC therapies requires robust clinical trials and the identification of predictive biomarkers to optimize its efficacy and safety.

The Influence of Microorganisms on the Onset and Development of Colorectal Cancer in Humans: A Descriptive Cross-Reference Study

BACKGROUND

The aim of this study is to determine which types of microorganisms influence the onset and development of colorectal cancer (CRC) in humans.

METHODS

In patients with CRC, three swabs were taken for microbiological analysis during surgical removal of the cancer: the first swab from the surface of the healthy intestinal mucosa, the second from the surface of the tumor, and the third from the middle of the tumor tissue.

RESULTS

In the healthy mucosa of the colon, the most prevalent microorganism was Escherichia coli at 70.5%, followed by Enterococcus spp. (47.7%) and Klebsiella/Enterobacter (20.5%). Microbiological analysis of the swabs from the surface of the tumor tissue showed that E. coli was the most prevalent at 72.7%, followed by Enterococcus spp. at 40.9%, Klebsiella/Enterobacter at 25%, and Pseudomonas aeruginosa at 20%. In the center of tumor tissue, E. coli was the most prevalent at 77.3%, followed by Enterococcus spp. at 47.7%, Klebsiella at 27%, and Pseudomonas aeruginosa at 18.2%.

CONCLUSION

Certain types of bacteria can influence the emergence and development of cancer, while other types can suppress the development of tumor tissue. Microbiological analysis of human stool samples can prevent the development of CRC.

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

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

E. Coli cytotoxic necrotizing factor-1 promotes colorectal carcinogenesis by causing oxidative stress, DNA damage and intestinal permeability alteration

BACKGROUND

Bacterial toxins are emerging as promising hallmarks of colorectal cancer (CRC) pathogenesis. In particular, Cytotoxic Necrotizing Factor 1 (CNF1) from E. coli deserves special consideration due to the significantly higher prevalence of this toxin gene in CRC patients with respect to healthy subjects, and to the numerous tumor-promoting effects that have been ascribed to the toxin in vitro. Despite this evidence, a definitive causal link between CNF1 and CRC was missing. Here we investigated whether CNF1 plays an active role in CRC onset by analyzing pro-carcinogenic key effects specifically induced by the toxin in vitro and in vivo.

METHODS

Viability assays, confocal microscopy of γH2AX and 53BP1 molecules and cytogenetic analysis were carried out to assess CNF1-induced genotoxicity on non-neoplastic intestinal epithelial cells. Caco-2 monolayers and 3D Caco-2 spheroids were used to evaluate permeability alterations specifically induced by CNF1, either in the presence or in the absence of inflammation. In vivo, an inflammatory bowel disease (IBD) model was exploited to evaluate the carcinogenic potential of CNF1. Immunohistochemistry and immunofluorescence stainings of formalin-fixed paraffin-embedded (FFPE) colon tissue were carried out as well as fecal microbiota composition analysis by 16 S rRNA gene sequencing.

RESULTS

CNF1 induces the release of reactive oxidizing species and chromosomal instability in non-neoplastic intestinal epithelial cells. In addition, CNF1 modifies intestinal permeability by directly altering tight junctions' distribution in 2D Caco-2 monolayers, and by hindering the differentiation of 3D Caco-2 spheroids with an irregular arrangement of these junctions. In vivo, repeated intrarectal administration of CNF1 induces the formation of dysplastic aberrant crypt foci (ACF), and produces the formation of colorectal adenomas in an IBD model. These effects are accompanied by the increased neutrophilic infiltration in colonic tissue, by a mixed pro-inflammatory and anti-inflammatory cytokine milieu, and by the pro-tumoral modulation of the fecal microbiota.

CONCLUSIONS

Taken together, our results support the hypothesis that the CNF1 toxin from E. coli plays an active role in colorectal carcinogenesis. Altogether, these findings not only add new knowledge to the contribution of bacterial toxins to CRC, but also pave the way to the implementation of current screening programs and preventive strategies.

Gut Microbiota Secondary Metabolites: Key Roles in GI Tract Cancers and Infectious Diseases

The gut microbiota, a dynamic ecosystem of trillions of microorganisms, produces secondary metabolites that profoundly influence host health. Recent research has highlighted the significant role of these metabolites, particularly short-chain fatty acids, indoles, and bile acids, in modulating immune responses, impacting epigenetic mechanisms, and contributing to disease processes. In gastrointestinal (GI) cancers such as colorectal, liver, and gastric cancer, microbial metabolites can drive tumorigenesis by promoting inflammation, DNA damage, and immune evasion. Conversely, these same metabolites hold therapeutic promise, potentially enhancing responses to chemotherapy and immunotherapy and even directly suppressing tumor growth. In addition, gut microbial metabolites play crucial roles in infectious disease susceptibility and resilience, mediating immune pathways that impact pathogen resistance. By consolidating recent insights into the gut microbiota's role in shaping disease and health, this review underscores the therapeutic potential of targeting microbiome-derived metabolites for treating GI cancers and infectious diseases and calls for further research into microbiome-based interventions.

Exploring micronutrients and microbiome synergy: pioneering new paths in cancer therapy

The human microbiome is the complex ecosystem consisting of trillions of microorganisms that play a key role in developing the immune system and nutrient metabolism. Alterations in the gut microbiome have been linked to cancer initiation, progression, metastasis, and response to treatment. Accumulating evidence suggests that levels of vitamins and minerals influence the gut environment and may have implications for cancer risk and progression. Bifidobacterium has been reported to reduce the colorectal cancer risk by binding to free iron. Additionally, zinc ions have been shown to activate the immune cells and enhance the effectiveness of immunotherapy. Higher selenium levels have been associated with a reduced risk of several cancers, including colorectal cancer. In contrast, enhanced copper uptake has been implicated in promoting cancer progression, including colon cancer. The interaction between cancer and gut bacteria, as well as dysbiosis impact has been studied in animal models. The interplay between prebiotics, probiotics, synbiotics, postbiotics and gut bacteria in cancer offers the diverse physiological benefits. We also explored the particular probiotic formulations like VSL#3, Prohep, Lactobacillus rhamnosus GG (LGG), etc., for their ability to modulate immune responses and reduce tumor burden in preclinical models. Targeting the gut microbiome through antibiotics, bacteriophage, microbiome transplantation-based therapies will offer a new perspective in cancer research. Hence, to understand this interplay, we outline the importance of micronutrients with an emphasis on the immunomodulatory function of the microbiome and highlight the microbiome's potential as a target for precision medicine in cancer treatment.

Colorectal Cancer in Inflammatory Bowel Disease: A Review of the Role of Gut Microbiota and Bacterial Biofilms in Disease Pathogenesis

The risk of colorectal cancer [CRC] is increased in patients with inflammatory bowel disease [IBD], particularly in extensive ulcerative colitis [UC] and Crohn's colitis. Gut microbiota have been implicated in the pathogenesis of CRC via multiple mechanisms, including the release of reactive oxygen species and genotoxins, and induction of inflammation, as well as activation of the immune response. Gut microbiota can enhance their carcinogenic and proinflammatory properties by organising into biofilms, potentially making them more resistant to the host's immune system and to antibiotics. Colonic biofilms have the capacity to invade colonic tissue and accelerate tumorigenesis in tumour-prone models of mice. In the context of IBD, the prevalence of biofilms has been estimated to be up to 95%. Although the relationship between chronic inflammation and molecular mediators that contribute to IBD-associated CRC is well established, the role of gut microbiota and biofilms in this sequence is not fully understood. Because CRC can still arise in the absence of histological inflammation, there is a growing interest in identifying chemopreventive agents against IBD-associated CRC. Commonly used in the treatment of UC, 5-aminosalicylates have antimicrobial and anticarcinogenic properties that might have a role in the chemoprevention of CRC via the inhibition or modulation of carcinogenic gut microbiota and potentially of biofilm formation. Whether biologics and other IBD-targeted therapies can decrease the progression towards dysplasia and CRC, via mechanisms independent of inflammation, is still unknown. Further research is warranted to identify potential new microbial targets in therapy for chemoprevention of dysplasia and CRC in IBD.

Gastrointestinal cancer resistance to treatment: the role of microbiota

The most common illnesses that adversely influence human health globally are gastrointestinal malignancies. The prevalence of gastrointestinal cancers (GICs) is relatively high, and the majority of patients receive ineffective care since they are discovered at an advanced stage of the disease. A major component of the human body is thought to be the microbiota of the gastrointestinal tract and the genes that make up the microbiome. The gut microbiota includes more than 3000 diverse species and billions of microbes. Each of them has benefits and drawbacks and been demonstrated to alter anticancer medication efficacy. Treatment of GIC with the help of the gut bacteria is effective while changes in the gut microbiome which is linked to resistance immunotherapy or chemotherapy. Despite significant studies and findings in this field, more research on the interactions between microbiota and response to treatment in GIC are needed to help researchers provide more effective therapeutic strategies with fewer treatment complication. In this review, we examine the effect of the human microbiota on anti-cancer management, including chemotherapy, immunotherapy, and radiotherapy.

Advancements in Understanding and Preventing Obesity-Related Colon Cancer

ABSTRACT

Obesity and colorectal cancer are global public health issues, with the prevalence of both conditions increasing over the last 4 decades. In the United States alone, the prevalence of obesity is greater than 40%, and this percentage is projected to increase past 50% by 2030. This review focuses on understanding the association between obesity and the risk of colorectal cancer while also highlighting hypotheses about molecular mechanisms underlying the link between these disease processes. We also consider whether those linkages can be disrupted via weight loss therapies, including lifestyle modifications, pharmacotherapy, bariatric surgery, and endobariatrics.

Interplay of Food-Derived Bioactive Peptides with Gut Microbiota: Implications for Health and Disease Management

Bioactive peptides (BPs) are protein fragments with beneficial effects on metabolism, physiology, and diseases. This review focuses on proteolytic BPs, which are produced by the action of gut microbiota on proteins in food and have demonstrated to influence the composition of gut microbes. And gut microbiota are candidate targets of BPs to alleviate oxidative stress, enhance immunity, and control diseases, including diabetes, hypertension, obesity, cancer, and immune and neurodegenerative diseases. Despite promising results, further research is needed to understand the mechanisms underlying the interactions between BPs and gut microbes, and to identify and screen more BPs for industrial applications. Overall, BPs offer potential as therapeutic agents for various diseases through their interactions with gut microbes, highlighting the importance of continued research in this area.

Molecular epidemiology, antibiotic resistance profile and frequency of integron 1 and 2 in adherent-invasive Escherichia coli isolates of colorectal cancer patients

This study explores the prevalence of adherent-invasive Escherichia coli (AIEC) in colorectal cancer (CRC) patients and investigates the potential of effective intracellular antibiotics as a therapeutic strategy for CRC patients with AIEC infections. Considering the pivotal role of integrons in bacterial antibiotic resistance, the frequency of class 1 and 2 integrons in AIEC isolated from CRC patients, in one of the referenced 3 gastroenterology clinics in Isfahan, Iran was examined. AIEC strains were isolated from the colorectal biopsies and their antimicrobial sensitivity was assessed using the disc diffusion method. Polymerase chain reaction (PCR) was employed to detect intl1 and intl2. The multilocus sequence typing (MLST) method was utilized to type 10 selected isolates. Of the 150 samples, 24 were identified as AIEC, with the highest number isolated from CRC2 (33.4%) and CRC1 (29.16%), and the least from the FH group (8.3%) and control group (12.5%). int1 in 79.2% and int2 in 45.8% of AIEC strains were found and 41.6% of strains had both integrons. AIEC isolates with int1 exhibited the highest sensitivity to trimethoprim-sulfamethoxazole (57.9%), while those with int2 showed the highest sensitivity to ciprofloxacin (63.6%). A significant association between resistance to rifampin and integron 2 presence in AIEC isolates was observed. Furthermore, a significant correlation between integron 1 presence, invasion, survival, and replication within macrophages in AIEC strains was identified. MLST analysis revealed ST131 from CC131 with integron 1 as the most common sequence type (ST). The emergence of such strains in CRC populations poses a serious public health threat. The distribution pattern of STs varied among studied groups, with pandemic STs highlighting the importance of examining and treating patients infected with these isolates. Comprehensive prospective clinical investigations are warranted to assess the prognostic value of detecting this pathovar in CRC and to evaluate therapeutic techniques targeting drug-resistant AIECs, such as phage therapy, bacteriocins, and anti-adhesion compounds, for CRC prevention and treatment.

Unravelling the role of intratumoral bacteria in digestive system cancers: current insights and future perspectives

Recently, research on the human microbiome, especially concerning the bacteria within the digestive system, has substantially advanced. This exploration has unveiled a complex interplay between microbiota and health, particularly in the context of disease. Evidence suggests that the gut microbiome plays vital roles in digestion, immunity and the synthesis of vitamins and neurotransmitters, highlighting its significance in maintaining overall health. Conversely, disruptions in these microbial communities, termed dysbiosis, have been linked to the pathogenesis of various diseases, including digestive system cancers. These bacteria can influence cancer progression through mechanisms such as DNA damage, modulation of the tumour microenvironment, and effects on the host's immune response. Changes in the composition and function within the tumours can also impact inflammation, immune response and cancer therapy effectiveness. These findings offer promising avenues for the clinical application of intratumoral bacteria for digestive system cancer treatment, including the potential use of microbial markers for early cancer detection, prognostication and the development of microbiome-targeted therapies to enhance treatment outcomes. This review aims to provide a comprehensive overview of the pivotal roles played by gut microbiome bacteria in the development of digestive system cancers. Additionally, we delve into the specific contributions of intratumoral bacteria to digestive system cancer development, elucidating potential mechanisms and clinical implications. Ultimately, this review underscores the intricate interplay between intratumoral bacteria and digestive system cancers, underscoring the pivotal role of microbiome research in transforming diagnostic, prognostic and therapeutic paradigms for digestive system cancers.

Contribution of pks+ Escherichia coli (E. coli) to Colon Carcinogenesis

Colorectal cancer (CRC) stands as a significant global health concern, ranking second in mortality and third in frequency among cancers worldwide. While only a small fraction of CRC cases can be attributed to inherited genetic mutations, the majority arise sporadically due to somatic mutations. Emerging evidence reveals gut microbiota dysbiosis to be a contributing factor, wherein polyketide synthase-positive Escherichia coli (pks+ E. coli) plays a pivotal role in CRC pathogenesis. pks+ bacteria produce colibactin, a genotoxic protein that causes deleterious effects on DNA within host colonocytes. In this review, we examine the role of the gut microbiota in colon carcinogenesis, elucidating how colibactin-producer bacteria induce DNA damage, promote genomic instability, disrupt the gut epithelial barrier, induce mucosal inflammation, modulate host immune responses, and influence cell cycle dynamics. Collectively, these actions foster a microenvironment conducive to tumor initiation and progression. Understanding the mechanisms underlying pks+ bacteria-mediated CRC development may pave the way for mass screening, early detection of tumors, and therapeutic strategies such as microbiota modulation, bacteria-targeted therapy, checkpoint inhibition of colibactin production and immunomodulatory pathways.

Friend or Foe: Exploring the Relationship between the Gut Microbiota and the Pathogenesis and Treatment of Digestive Cancers

Digestive cancers are among the leading causes of cancer death in the world. However, the mechanisms of cancer development and progression are not fully understood. Accumulating evidence in recent years pointing to the bidirectional interactions between gut dysbiosis and the development of a specific type of gastrointestinal cancer is shedding light on the importance of this "unseen organ"-the microbiota. This review focuses on the local role of the gut microbiota imbalance in different digestive tract organs and annexes related to the carcinogenic mechanisms. Microbiota modulation, either by probiotic administration or by dietary changes, plays an important role in the future therapies of various digestive cancers.

The microbial landscape of colorectal cancer

Colorectal cancer (CRC) is a substantial source of global morbidity and mortality in dire need of improved prevention and treatment strategies. As our understanding of CRC grows, it is becoming increasingly evident that the gut microbiota, consisting of trillions of microorganisms in direct interface with the colon, plays a substantial role in CRC development and progression. Understanding the roles that individual microorganisms and complex microbial communities play in CRC pathogenesis, along with their attendant mechanisms, will help yield novel preventive and therapeutic interventions for CRC. In this Review, we discuss recent evidence concerning global perturbations of the gut microbiota in CRC, associations of specific microorganisms with CRC, the underlying mechanisms by which microorganisms potentially drive CRC development and the roles of complex microbial communities in CRC pathogenesis. While our understanding of the relationship between the microbiota and CRC has improved in recent years, our findings highlight substantial gaps in current research that need to be filled before this knowledge can be used to the benefit of patients.

Gut Microbiome-Colorectal Cancer Relationship

Traditionally, the role of gut dysbiosis was thought to be limited to pathologies like Clostridioides difficile infection, but studies have shown its role in other intestinal and extraintestinal pathologies. Similarly, recent studies have surfaced showing the strong potential role of the gut microbiome in colorectal cancer, which was traditionally attributed mainly to sporadic or germline mutations. Given that it is the third most common cancer and the second most common cause of cancer-related mortality, 78 grants totaling more than USD 28 million have been granted to improve colon cancer management since 2019. Concerted efforts by several of these studies have identified specific bacterial consortia inducing a proinflammatory environment and promoting genotoxin production, causing the induction or progression of colorectal cancer. In addition, changes in the gut microbiome have also been shown to alter the response to cancer chemotherapy and immunotherapy, thus changing cancer prognosis. Certain bacteria have been identified as biomarkers to predict the efficacy of antineoplastic medications. Given these discoveries, efforts have been made to alter the gut microbiome to promote a favorable diversity to improve cancer progression and the response to therapy. In this review, we expand on the gut microbiome, its association with colorectal cancer, and antineoplastic medications. We also discuss the evolving paradigm of fecal microbiota transplantation in the context of colorectal cancer management.

Dietary fiber (oligosaccharide and non-starch polysaccharide) in preventing and treating functional gastrointestinal disorders - Challenges and controversies: A review

Functional gastrointestinal disorders (FGIDs) are a group of chronic or recurrent gastrointestinal functional diseases, including functional dyspepsia, irritable bowel syndrome, and functional constipation. A lack of safe and reliable treatments for abdominal pain-related FGIDs has prompted interest in new therapies. Evidence has shown that supplementation with dietary fiber may help treat FGIDs. Dietary fibers (DFs) have been demonstrated to have regulatory effects on the gut microbiota, microbiota metabolites, and gastrointestinal movement and have important implications for preventing and treating FGIDs. However, the adverse effects of some DFs, such as fermentable oligosaccharides, on FGIDs are unclear. This review provides an overview of the DFs physiological properties and functional characteristics that influence their use in management of FGIDs, with emphasis on structural modification technology to improve their therapeutic activities. The review highlights that the use of appropriate or novel fibers is a potential therapeutic approach for FGIDs.

Microbiota-derived small molecule genotoxins: host interactions and ecological impact in the gut ecosystem

The human intestinal tract is densely colonized by a microbial community that is subject to intense competition. Bacteria in this complex habitat seek to outcompete their neighbors for nutrients and eliminate competitors with antibacterial toxins. Antagonism can be mediated by diverse effectors including toxic proteins and small molecule inhibitors that are released extracellularly or delivered by specialized secretion systems to targeted cells. Two prototypical microbiota-derived enterotoxins, colibactin and tilimycin, and the newly discovered family of indolimines represent an expanding group of non-proteinaceous small molecules which specifically target DNA. In addition to cell killing, they generate mutations and genome instability in intoxicated microbes and host cells alike. They have been studied in detail because of their direct toxicity to human cells and important etiological roles in intestinal pathologies. Increasing evidence, however, reveals that these commensal genotoxins are also mediators of interbacterial antagonism, which impacts gut microbial ecology. In this review, we illustrate the functional versatility of commensal genotoxins in the gut ecosystem.

Colibactin-producing Escherichia coli enhance resistance to chemotherapeutic drugs by promoting epithelial to mesenchymal transition and cancer stem cell emergence

Human colorectal cancers (CRCs) are readily colonized by colibactin-producing E. coli (CoPEC). CoPEC induces DNA double-strand breaks, DNA mutations, genomic instability, and cellular senescence. Infected cells produce a senescence-associated secretory phenotype (SASP), which is involved in the increase in tumorigenesis observed in CRC mouse models infected with CoPEC. This study investigated whether CoPEC, and the SASP derived from CoPEC-infected cells, impacted chemotherapeutic resistance. Human intestinal epithelial cells were infected with the CoPEC clinical 11G5 strain or with its isogenic mutant, which is unable to produce colibactin. Chemotherapeutic resistance was assessed in vitro and in a xenograft mouse model. Expressions of cancer stem cell (CSC) markers in infected cells were investigated. Data were validated using a CRC mouse model and human clinical samples. Both 11G5-infected cells, and uninfected cells incubated with the SASP produced by 11G5-infected cells exhibited an increased resistance to chemotherapeutic drugs in vitro and in vivo. This finding correlated with the induction of the epithelial to mesenchymal transition (EMT), which led to the emergence of cells exhibiting CSC features. They grew on ultra-low attachment plates, formed colonies in soft agar, and overexpressed several CSC markers (e.g. CD133, OCT-3/4, and NANOG). In agreement with these results, murine and human CRC biopsies colonized with CoPEC exhibited higher expression levels of OCT-3/4 and NANOG than biopsies devoid of CoPEC. Conclusion: CoPEC might aggravate CRCs by inducing the emergence of cancer stem cells that are highly resistant to chemotherapy.

Bacterial infection and microbiota in carcinogenesis and tumor development

Microbiota colonize exposed body tissues (e.g., gastrointestinal tract, skin, lungs, female genital tract, and urogenital tracts) and unexposed sites (e.g., breast). Persistent bacterial infection in the host lead to the development of multiple disease. They are implicated in the pathogenesis of various complex diseases, including diabetes, atherosclerosis, autoimmune diseases, Alzheimer's disease, and malignant diseases. Amounting studies have demonstrated the role of bacterial infection in carcinogenesis. The study of microbiota in tumorigenesis is primarily focused on lung cancer, colorectal cancer (CRC), breast cancer, gastric cancer, and gynecologic tumors, and so on. Infection of Helicobacter pylori in gastric cancer carcinogenesis is recognized as class I carcinogen by the World Health Organization (WHO) decades ago. The role of Fusobacterium nucleatum in the development of colorectal cancer is extensively investigated. Variable bacteria have been cultured from the tumor tissues. The identification of microbiota in multiple tumor tissues reveal that bacterial infection and microbiota are associated with tumor development. The microbiota affects multiple aspects of carcinogenesis and tumor development, including favoring epithelial cells proliferation, establishing inflammatory microenvironment, promoting metastasis, and causing resistance to therapy. On the other hand, microbiota can shape a tumor surveillance environment by enhancing cell activity, and sensitize the tumor cells to immune therapy. In the present review, the roles of microbiota in multiple malignancies are summarized, and unraveling the mechanisms of host-microbiota interactions can contribute to a better understanding of the interaction between microbiota and host cells, also the development of potential anti-tumor therapeutic strategies.

Influence of pathogens on host genome and epigenome in development of head and neck cancer

BACKGROUND

Head and neck cancer (HNSCC) is a heterogeneous group of cancers, affecting multiple regions such as oral cavity, pharynx, larynx, and nasal region, each showing a distinct molecular profile. HNSCC accounts for more than 6 million cases worldwide, soaring mainly in the developing countries.

RECENT FINDINGS

The aetiology of HNSCC is complex and multifactorial, involving both genetic and environmental factors. The critical role of microbiome, which includes bacteria, viruses, and fungi, is under spotlight due to the recent reports on their contribution in the development and progression of HNSCC. This review focuses on the effect of opportunistic pathogens on the host genome and epigenome, which contributes to the disease progression. Drawing parallels from the host-pathogen interactions observed in other tumour types arising from the epithelial tissue such as colorectal cancer, the review also calls attention to the potential explorations of the role of pathogens in HNSCC biology and discusses the clinical implications of microbiome research in detection and treatment of HNSCC.

CONCLUSION

Our understanding of the genomic effects of the microbes on the disease progression and the mechanistic insights of the host-pathogen interaction will pave way to novel treatment and preventive approaches in HNSCC.

Intracellular bacteria in cancer-prospects and debates

Recent evidence suggests that some human cancers may harbor low-biomass microbial ecosystems, spanning bacteria, viruses, and fungi. Bacteria, the most-studied kingdom in this context, are suggested by these studies to localize within cancer cells, immune cells and other tumor microenvironment cell types, where they are postulated to impact multiple cancer-related functions. Herein, we provide an overview of intratumoral bacteria, while focusing on intracellular bacteria, their suggested molecular activities, communication networks, host invasion and evasion strategies, and long-term colonization capacity. We highlight how the integration of sequencing-based and spatial techniques may enable the recognition of bacterial tumor niches. We discuss pitfalls, debates and challenges in decisively proving the existence and function of intratumoral microbes, while reaching a mechanistic elucidation of their impacts on tumor behavior and treatment responses. Together, a causative understanding of possible roles played by intracellular bacteria in cancer may enable their future utilization in diagnosis, patient stratification, and treatment.

The crosstalk between intestinal bacterial microbiota and immune cells in colorectal cancer progression

Different types of cells that are involved in tumor immunity play a significant part in antitumor therapy. The intestinal microbiota consist of the trillions of diverse microorganisms that inhabit the gastrointestinal tract. Recently, much emphasis has been paid to the link between these symbionts and colorectal cancer (CRC). This association might be anything from oncogenesis and cancer development to resistance or susceptibility to chemotherapeutic medicines. Cancer patients have a significantly different microbial composition in their guts compared to healthy persons. The microbiome may play a role in the development and development of cancer through the modulation of tumor immunosurveillance, as shown by these studies; however, the specific processes underlying this role are still poorly understood. This review focuses on the relationship between the intestinal bacterial microbiota and immune cells to determine how the commensal microbiome influences the initiation and development of CRC.

Genotoxins: The Mechanistic Links between Escherichia coli and Colorectal Cancer

Emerging evidence indicates bacterial infections contribute to the formation of cancers. Bacterial genotoxins are effectors that cause DNA damage by introducing single- and double-strand DNA breaks in the host cells. The first bacterial genotoxin cytolethal distending toxin (CDT) was a protein identified in 1987 in a pathogenic strain in Escherichia coli (E. coli) isolated from a young patient. The peptide-polyketide genotoxin colibactin is produced by the phylogenetic group B₂ of E. coli. Recently, a protein produced by attaching/effacing (A/E) pathogens, including enteropathogenic and enterohemorrhagic E. coli (EPEC and EHEC) and their murine equivalent Citrobacter rodentium (CR), has been reported as a novel protein genotoxin, being injected via the type III secretion system (T3SS) into host cells and harboring direct DNA digestion activity with a catalytic histidine-aspartic acid dyad. These E. coli-produced genotoxins impair host DNA, which results in senescence or apoptosis of the target cells if the damage is beyond repair. Conversely, host cells can survive and proliferate if the genotoxin-induced DNA damage is not severe enough to kill them. The surviving cells may accumulate genomic instability and acquire malignant traits. This review presents the cellular responses of infection with the genotoxins-producing E. coli and discusses the current knowledge of the tumorigenic potential of these toxins.

Intestinal bacteria and colorectal cancer: etiology and treatment

The etiology of colorectal cancer (CRC) is influenced by bacterial communities that colonize the gastrointestinal tract. These microorganisms derive essential nutrients from indigestible dietary or host-derived compounds and activate molecular signaling pathways necessary for normal tissue and immune function. Associative and mechanistic studies have identified bacterial species whose presence may increase CRC risk, including notable examples such as Fusobacterium nucleatum, Enterotoxigenic Bacteroides fragilis, and pks+ E. coli. In recent years this work has expanded in scope to include aspects of host mutational status, intra-tumoral microbial heterogeneity, transient infection, and the cumulative influence of multiple carcinogenic bacteria after sequential or co-colonization. In this review, we will provide an updated overview of how host-bacteria interactions influence CRC development, how this knowledge may be utilized to diagnose or prevent CRC, and how the gut microbiome influences CRC treatment efficacy.

Implication of gut microbes and its metabolites in colorectal cancer

BACKGROUND

Colorectal cancer (CRC) is the third most common cancer with a significant impact on loss of life. In 2020, nearly 1.9 million new cases and over 9,35,000 deaths were reported. Numerous microbes that are abundant in the human gut benefit host physiology in many ways. Although the underlying mechanism is still unknown, their association appears to be crucial in the beginning and progression of CRC. Diet has a significant impact on the microbial composition and may increase the chance of getting CRC. Increasing evidence points to the gut microbiota as the primary initiator of colonic inflammation, which is connected to the development of colonic tumors. However, it is unclear how the microbiota contributes to the development of CRCs. Patients with CRC have been found to have dysbiosis of the gut microbiota, which can be identified by a decline in commensal bacterial species, such as those that produce butyrate, and a concurrent increase in harmful bacterial populations, such as opportunistic pathogens that produce pro-inflammatory cytokines. We believe that using probiotics or altering the gut microbiota will likely be effective tools in the fight against CRC treatment.

PURPOSE

In this review, we revisited the association between gut microbiota and colorectal cancer whether cause or effect. The various factors which influence gut microbiome in patients with CRC and possible mechanism in relation with development of CRC.

CONCLUSION

The clinical significance of the intestinal microbiota may aid in the prevention and management of CRC.

Pharmacological Mechanism of Pingxiao Formula against Colorectal Cancer

Colorectal cancer (CRC) is the most common cancer worldwide and develops due to a broad range of causative factors. Pingxiao (PX) formula and Xihuang (XH) formula are two commonly used drugs to treat CRC, especially as an alternative therapy for those patients who could not suffer surgery, chemotherapy, or immunotherapy, namely, elder or advanced CRC patients. However, the pertinent pharmacological mechanisms are still elusive. The investigation was designed to explain the pharmacological mechanisms of the PX formula. A murine model of CRC was established by injecting CT26.WT cells into the caecum of 4-week-old male Balb/c mice, following PX or XH treatment for 30 days. Network pharmacology analysis combined with weighted gene coexpression network analysis (WGCNA) predicted the pharmacological mechanisms and therapeutic value. High-throughput 16S rRNA sequencing determined the alterations in the gut microbiota communities. Western blotting, immunofluorescence, and flow cytometry examined the influence of PX on the tumor microenvironment (TME). Injection of CT26.WT-induced CRC in Balb/c mice was markedly attenuated by PX treatment. Compared with XH administration, PX exhibited a stronger antitumor effect, such as smaller tumor volume, lower interleukin 17 (IL-17), IL-6 and tumor necrosis factor-alpha (TNFα) serum levels, and higher interferon-gamma (IFN-γ) concentration. Network pharmacology analysis demonstrated that both PX and XH targets were enriched in cancers and inflammatory responses. RNA sequencing confirmed that PX treatment induced cancer cell apoptosis and inhibited inflammatory reactions within the tumor. Moreover, the PX formula considerably restored homeostasis of the gut microbiota, which was not observed in the XH group. PX targets, those associated with the survival probability of CRC patients, correlated with macrophage (Mφ) infiltration, which presented an independent risk factor for the CRC outcome. PX treatment promoted the transition of alternatively activated Mφs (M2 Mφs) to classically activated Mφs (M1 Mφs). Moreover, the peritoneal Mφs from the PX group inhibited the migration of CW26.WT cells, as evidenced by the wound healing experiment and transwell assay, which was consistent with the decreased expression of the vascular endothelial growth factor (VEGF). Furthermore, the coculturing system confirmed that PX-treated Mφs suppressed colorectal tumor-derived organoid proliferation. PX formula exhibits a potential antitumor effect against CRC by suppressing the colonization of pathological microorganisms, reshaping Mφ effector functions and hence inhibiting cancer cell proliferation.

Determination of biomarkers associated with neoadjuvant treatment response focusing on colibactin-producing Escherichia coli in patients with mid or low rectal cancer: a prospective clinical study protocol (MICARE)

INTRODUCTION

The management of mid and low rectal cancer is based on neoadjuvant chemoradiotherapy (CRT) followed by standardised surgery. There is no biomarker in rectal cancer to aid clinicians in foreseeing treatment response. The determination of factors associated with treatment response might allow the identification of patients who require tailored strategies (eg, therapeutic de-escalation or intensification). Colibactin-producing Escherichia coli (CoPEC) has been associated with aggressive colorectal cancer and could be a poor prognostic factor. Currently, no study has evaluated the potential association between intestinal microbiota composition and tumour response to CRT in mid and low rectal cancer. The aim of this study is to assess the association between response to neoadjuvant CRT and faecal intestinal microbiota composition and/or CoPEC prevalence in patients with mid or low rectal cancer.

METHODS AND ANALYSIS

This is a non-randomised bicentric prospective clinical study with a recruitment capacity of 200 patients. Three stool samples will be collected from participants with histological-proven adenocarcinome of mid or low rectum who meet eligibility criteria of the study protocol: one before neoadjuvant treatment start, one in the period between CRT end and surgery and one the day before surgery. In each sample, CoPEC will be detected by culture in special media and molecular (PCR) approaches. The global microbiota composition will be also assessed by the bacterial 16S rRNA gene sequencing. Neoadjuvant CRT response and tumour regression grade will be described using the Dworak system at pathological examination. Clinical data and survival outcomes will also be collected and investigated.

ETHICS AND DISSEMINATION

MICARE was approved by the local ethics committee (Comité de Protection des Personnes Sud-Est II, 18 December 2019. Reference number 2019-A02493-54 and the institutional review board. Patients will be required to provide written informed consent. Results will be published in a peer reviewed journal.

TRIAL REGISTRATION NUMBER

NCT04103567.

Antibiotics, the microbiome and gastrointestinal cancers: A causal interference?

Our understanding of the gut microbiota has significantly evolved over the last two decades. Advances in the analysis of the gut microbiome continues to reveal complex microbial communities and discoveries about their role in health and diseases, including cancer development, are continuously growing. In addition, research has demonstrated that the use of antibiotics can modulate the gut microbiota composition negatively and influence cancer treatment outcomes, suggesting that antibiotics should be avoided if possible. In this article, we review the role of the gut microbiota in the formation of GI cancers. We show that specific bacterial populations can positively or negatively affect cancer formation with specific attention given to gastric and colorectal cancer. We also review the role of microbial-targeted therapies on cancer treatment outcomes.

Tumor microbiome - an integral part of the tumor microenvironment

The tumor microenvironment (TME) plays a significant role in tumor progression and cancer cell survival. Besides malignant cells and non-malignant components, including immune cells, elements of the extracellular matrix, stromal cells, and endothelial cells, the tumor microbiome is considered to be an integral part of the TME. Mounting evidence from preclinical and clinical studies evaluated the presence of tumor type-specific intratumoral bacteria. Differences in microbiome composition between cancerous tissues and benign controls suggest the importance of the microbiome-based approach. Complex host-microbiota crosstalk within the TME affects tumor cell biology via the regulation of oncogenic pathways, immune response modulation, and interaction with microbiota-derived metabolites. Significantly, the involvement of tumor-associated microbiota in cancer drug metabolism highlights the therapeutic implications. This review aims to summarize current knowledge about the emerging role of tumor microbiome in various types of solid malignancies. The clinical utility of tumor microbiome in cancer progression and treatment is also discussed. Moreover, we provide an overview of clinical trials evaluating the role of tumor microbiome in cancer patients. The research focusing on the communication between the gut and tumor microbiomes may bring new opportunities for targeting the microbiome to increase the efficacy of cancer treatment and improve patient outcomes.

Genomics and pathotypes of the many faces of Escherichia coli

Escherichia coli is the most researched microbial organism in the world. Its varied impact on human health, consisting of commensalism, gastrointestinal disease, or extraintestinal pathologies, has generated a separation of the species into at least eleven pathotypes (also known as pathovars). These are broadly split into two groups, intestinal pathogenic E. coli (InPEC) and extraintestinal pathogenic E. coli (ExPEC). However, components of E. coli's infinite open accessory genome are horizontally transferred with substantial frequency, creating pathogenic hybrid strains that defy a clear pathotype designation. Here, we take a birds-eye view of the E. coli species, characterizing it from historical, clinical, and genetic perspectives. We examine the wide spectrum of human disease caused by E. coli, the genome content of the bacterium, and its propensity to acquire, exchange, and maintain antibiotic resistance genes and virulence traits. Our portrayal of the species also discusses elements that have shaped its overall population structure and summarizes the current state of vaccine development targeted at the most frequent E. coli pathovars. In our conclusions, we advocate streamlining efforts for clinical reporting of ExPEC, and emphasize the pathogenic potential that exists throughout the entire species.

The Microbiome-Immune Axis Therapeutic Effects in Cancer Treatments

During the last decades, research and therapeutic methods in cancer treatment have been evolving. As the results, nowadays, cancer patients are receiving several types of treatments, ranging from chemotherapy and radiation therapy to surgery and immunotherapy. In fact, most cancer patients take a combination of current anti-cancer therapies to improve the efficacy of treatment. However, current strategies still cause some side effects to patients, such as pain and depression. Therefore, there is the need to discover better ways to eradicate cancer whilst minimizing side effects. Recently, immunotherapy, particularly immune checkpoint blockade, is rising as an effective anti-cancer treatment. Unlike chemotherapy or radiation therapy, immunotherapy has few side effects and a higher tumor cell removal efficacy depend on cellular immunological mechanisms. Moreover, recent studies suggest that tissue immune responses are regulated by their microbiome composition. Each tissue has their specific microenvironment, which makes their microbiome composition different, particularly in the context of different types of cancer, such as breast, colorectal, kidney, lung, and skin. Herein, we review the current understanding of the relationship of immune responses and tissue microbiome in cancer in both animal and human studies. Moreover, we discuss the cancermicrobiome-immune axis in the context of cancer development and treatment. Finally, we speculate on strategies to control tissue microbiome alterations that may synergistically affect the immune system and impact cancer treatment outcomes.

Infectious Causes of Neoplasia in the Domestic Cat

In recent years, growing attention has been paid to the influence/role of infectious diseases in tumour development and progression. Investigations have demonstrated that some infectious organisms can have a direct role in the development of neoplasia, whereas others can predispose to neoplasia by alterations in the immune response, or by creating a pro-inflammatory environment. Feline leukaemia virus was one of the first infectious agents recognised as an oncogenic organism, and along with feline immunodeficiency virus has received the most attention. Since the discovery of this retrovirus, several other organisms have been associated with neoplastic processes in cats, these include gammaherpes virus, mouse mammary tumour virus, papillomaviruses, hepadnavirus, Helicobacter species, and the parasitic infections Platynosomum fastosum and Opisthorchis viverrini. This review summarises the findings to date.

Biological roles of toll-like receptors and gut microbiota in colorectal cancer

Colorectal cancer (CRC) is one of the most considerably common malignancies of the alimentary system, with high mortality and incidence rates.  The present study suggested that the occurrence of CRC is closely related to bacteria, as the large intestine is a gathering place for human micro-organisms. However, the nosogenesis of bacteria leading to tumorigenesis is still obscure. Recently, many studies have reported that toll-like receptors and their related molecular pathways are involved in the process of gut micro-organisms generating CRC. Gut micro-organisms can promote or inhibit the development of CRC via binding to special toll-like receptors. In this paper, the authors review the relationship among toll-like receptors, gut micro-organisms and CRC in order to provide a reference for future tumor immunotherapy and targeted therapy.

Interaction between microbiota and immunity and its implication in colorectal cancer

Colorectal cancer (CRC) is one of the leading causes of cancer-related death in the world. Besides genetic causes, colonic inflammation is one of the major risk factors for CRC development, which is synergistically regulated by multiple components, including innate and adaptive immune cells, cytokine signaling, and microbiota. The complex interaction between CRC and the gut microbiome has emerged as an important area of current CRC research. Metagenomic profiling has identified a number of prominent CRC-associated bacteria that are enriched in CRC patients, linking the microbiota composition to colitis and cancer development. Some microbiota species have been reported to promote colitis and CRC development in preclinical models, while a few others are identified as immune modulators to induce potent protective immunity against colitis and CRC. Mechanistically, microbiota regulates the activation of different immune cell populations, inflammation, and CRC via crosstalk between innate and adaptive immune signaling pathways, including nuclear factor kappa B (NF-κB), type I interferon, and inflammasome. In this review, we provide an overview of the potential interactions between gut microbiota and host immunity and how their crosstalk could synergistically regulate inflammation and CRC, thus highlighting the potential roles and mechanisms of gut microbiota in the development of microbiota-based therapies to prevent or alleviate colitis and CRC.

Phenotypicand Genotypic Characterization of Clinical Isolates of Intracellular Adherent–Invasive Escherichia coli Among Different Stages, Family History, and Treated Colorectal Cancer Patients in Iran

There is increasing evidence showing that microbial dysbiosis impacts the health and cancer risk of the host. An association between adherent–invasive Escherichia coli (AIEC) and colorectal cancer (CRC) has been revealed. Cyclomodulins (CMs) have been receiving increasing attention for carcinogenic changes. In this study, the incidence and features of intracellular AIEC and cyclomodulin-encoding genes were investigated and the phylogenetic grouping and genetic relatedness were evaluated. E. coli strains were isolated from the colorectal biopsies. Adhesion and invasion assays and intramacrophage cell survival test were performed to separate the AIEC isolates. Virulence genotyping for the genes htrA, dsbA, chuA, and lpfA and the cyclomodulin toxins was also conducted. In addition, phylogenetic grouping of the isolates was determined. Subsequently, repetitive element sequence-based PCR (rep-PCR) fingerprinting was performed. A total of 24 AIEC pathovars were isolated from 150 patients. The prevalence rates of htr, dsbA, and lpfA were 70.83% and that of chuA was 91.66%. The frequencies of the cyclomodulin toxins were as follows: cnf1, 29.2%; cnf2, 25%; colibactin, 29.2%; and cdt, 4.2%; cif was not found. Among the AIEC isolates, 4.2%, 4.2%, 54.2%, 29.2%, and 8.3% with phylotypes A or C, B1, B2, D, and E were identified, respectively. Left-sided colon carcinoma and adenocarcinoma T≥1 stage (CRC2) were colonized by B2 phylogroup AIEC-producing CMs more often than the samples from the other groups. Close genetic relatedness was observed in AIEC isolates with rep-PCR.

Bacteria and tumor: Understanding the roles of bacteria in tumor genesis and immunology

In the past, tumor and microbial infection were commonly regarded as independent diseases with few interrelations. The discovery of bacteria in tumor tissue changed the knowledge of bacteria-tumor relationship. Recently, more and more findings have demonstrated the significant effects of bacteria on the genesis, development and metastasis of tumor. Particularly, the influence of bacteria on tumor immunity is of great interest. Bacteria can inhibit the function of immune system through multiple mechanisms. On the other hand, some bacteria can also enhance the immune response and inhibit tumor progression. Understanding the bacteria-tumor interactions is of great importance for developing novel anticancer approaches. Herein, we aim to provide a comprehensive understanding of the tumor/tumor immunology, the biogenesis of bacteria in tumor and the relation of tumorigenesis with bacteria. In addition, the roles of bacteria in tumor immunology and the potential approaches to use bacteria for cancer therapy are discussed.

Bacterial infections in cancer: A bilateral relationship

Bacteria share a long commensal relationship with the human body. New findings, however, continue to unravel many complexities associated with this old alliance. In the past decades, the dysbiosis of human microbiome has been linked to tumorigenesis, and more recently to spontaneous colonization of existing tumors. The topic, however, remains open for debate as the claims for causative-prevailing dual characteristics of bacteria are mostly based on epidemiological evidence rather than robust mechanistic models. There are also no reviews linking the collective impact of bacteria in tumor microenvironments to the efficacy of cancer drugs, mechanisms of pathogen-initiated cancer and bacterial colonization, personalized nanomedicine, nanotechnology, and antimicrobial resistance. In this review, we provide a holistic overview of the bilateral relationship between cancer and bacteria covering all these aspects. Our collated evidence from the literature does not merely categorize bacteria as cancer causative or prevailing agents, but also critically highlights the gaps in the literature where more detailed studies may be required to reach such a conclusion. Arguments are made in favor of dual drug therapies that can simultaneously co-target bacteria and cancer cells to overcome drug resistance. Also discussed are the opportunities for leveraging the natural colonization and remission power of bacteria for cancer treatment. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Infectious Disease Nanotechnology Approaches to Biology > Nanoscale Systems in Biology Therapeutic Approaches and Drug Discovery > Emerging Technologies.

Gut microbiota modulation: a tool for the management of colorectal cancer

Colorectal cancer (CRC) is the second cause of cancer death and the third most frequently diagnosed cancer. Besides the lifestyle, genetic and epigenetic alterations, and environmental factors, gut microbiota also plays a vital role in CRC development. The interruption of the commensal relationship between gut microbiota and the host could lead to an imbalance in the bacteria population, in which the pathogenic bacteria become the predominant population in the gut. Different therapeutic strategies have been developed to modify the gut immune system, prevent pathogen colonization, and alter the activity and composition of gut microbiota, such as prebiotics, probiotics, postbiotics, antibiotics, and fecal microbiota transplantation (FMT). Even though the employed strategies exhibit promising results, their translation into the clinic requires evaluating potential implications and risks, as well as assessment of their long-term effects. This study was set to review the gut microbiota imbalances and their relationship with CRC and their effects on CRC therapy, including chemotherapy and immunotherapy. More importantly, we reviewed the strategies that have been used to modulate gut microbiota, their impact on the treatment of CRC, and the challenges of each strategy.

Prevalence, Abundance, and Virulence of Adherent-Invasive Escherichia coli in Ulcerative Colitis, Colorectal Cancer, and Coeliac Disease

BACKGROUND & AIMS

Adherent-invasive E. coli (AIEC) has largely been implicated in the pathogenesis of Crohn's disease (CD). E. coli strains with similar genetic backgrounds and virulence genes profiles have been associated with other intestinal disorders, such as ulcerative colitis (UC), colorectal cancer (CRC), and coeliac disease (CeD), but the role of AIEC in these diseases remains unexplored. We aimed to assess the distribution, abundance, and pathogenic features of AIEC in UC, CRC, and CeD.

METHODS

The AIEC phenotype was investigated in 4,233 E. coli isolated from the ileum and colon of 14 UC and 15 CRC patients and in 38 fecal E. coli strains obtained from 17 CeD and 10 healthy (H) children. AIEC prevalence and abundance were compared with previous data from CD patients and H controls. Clonality, virulence gene carriage, and phylogenetic origin were determined for the AIEC identified.

RESULTS

In UC, AIEC prevalence was intermediate between CD and H subjects (UC: 35.7%, CD: 55.0%, H: 21.4%), and similar to CD patients with colonic disease (C-CD: 40.0%). In CRC, the prevalence was lower (6.7%) than these groups. In patients with AIEC, the estimated abundance was similar across all intestinal conditions. All AIEC strains isolated from UC and CRC belonged to the B1 phylogroup, except for a strain of the A phylogroup, and the majority (75% of clonally distinct AIEC) harbored the Afa/Dr operon and the cdt gene. None of the E. coli isolated from the CeD cohort were AIEC. Nonetheless, E. coli strains isolated from active CeD patients showed higher invasion indices than those isolated from H and inactive CeD pediatric patients.

CONCLUSION

We support the hypothesis that AIEC-like strains can be involved not only in CD but also in UC. Further works are needed to study the virulence particularities of these groups of strains and to determine if there is a causative link between AIEC and UC. In contrast, we rule out the possible association of AIEC with CRC. In addition, to further study the E. coli strains in CeD for their possible pathogenic role would be of interest.

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

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

Fusobacterium nucleatum is associated with inflammation and poor survival in early-stage HPV-negative tongue cancer

Persistent pathogen infection is a known cause of malignancy, although with sparse systematic evaluation across tumor types. We present a comprehensive landscape of 1060 infectious pathogens across 239 whole exomes and 1168 transcriptomes of breast, lung, gallbladder, cervical, colorectal, and head and neck tumors. We identify known cancer-associated pathogens consistent with the literature. In addition, we identify a significant prevalence of Fusobacterium in head and neck tumors, comparable to colorectal tumors. The Fusobacterium-high subgroup of head and neck tumors occurs mutually exclusive to human papillomavirus, and is characterized by overexpression of miRNAs associated with inflammation, elevated innate immune cell fraction and nodal metastases. We validate the association of Fusobacterium with the inflammatory markers IL1B, IL6 and IL8, miRNAs hsa-mir-451a, hsa-mir-675 and hsa-mir-486-1, and MMP10 in the tongue tumor samples. A higher burden of Fusobacterium is also associated with poor survival, nodal metastases and extracapsular spread in tongue tumors defining a distinct subgroup of head and neck cancer.

Microbiome and colorectal carcinogenesis: Linked mechanisms and racial differences

Various studies have shown the interplay between the intestinal microbiome, environmental factors, and genetic changes in colorectal cancer (CRC) development. In this review, we highlight the various gut and oral microbiota associated with CRC and colorectal adenomas, and their proposed molecular mechanisms in relation to the processes of “the hallmarks of cancer”, and differences in microbial diversity and abundance between race/ethnicity. Patients with CRC showed increased levels of Bacteroides, Prevotella, Escherichia coli, enterotoxigenic Bacteroides fragilis, Streptococcus gallolyticus, Enterococcus faecalis, Fusobacterium nucleatum (F. nucleatum) and Clostridium difficile. Higher levels of Bacteroides have been found in African American (AA) compared to Caucasian American (CA) patients. Pro-inflammatory bacteria such as F. nucleatum and Enterobacter species were significantly higher in AAs. Also, AA patients have been shown to have decreased microbial diversity compared to CA patients. Some studies have shown that using microbiome profiles in conjunction with certain risk factors such as age, race and body mass index may help predict healthy colon vs one with adenomas or carcinomas. Periodontitis is one of the most common bacterial infections in humans and is more prevalent in Non-Hispanic-Blacks as compared to Non-Hispanic Whites. This condition causes increased systemic inflammation, immune dysregulation, gut microbiota dysbiosis and thereby possibly influencing colorectal carcinogenesis. Periodontal-associated bacteria such as Fusobacterium, Prevotella, Bacteroides and Porphyromonas have been found in CRC tissues and in feces of CRC patients. Therefore, a deeper understanding of the association between oral and gastrointestinal bacterial profile, in addition to identifying prevalent bacteria in patients with CRC and the differences observed in ethnicity/race, may play a pivotal role in predicting incidence, prognosis, and lead to the development of new treatments.

Lactulose Modulates the Structure of Gut Microbiota and Alleviates Colitis-Associated Tumorigenesis

Lactulose, a galactose-fructose disaccharide, is made from the milk sugar lactose by heating or isomerization processes. Lactulose is proposed to modulate gut microbiota and thus expected to be beneficial in treating inflammatory bowel disease. In the present study, we investigated the therapeutic effect of lactulose on gastrointestinal inflammation and inflammation-related tumorigenesis in a mouse model of colorectal cancer as well as its effect on gut microbiota composition. Azoxymethane (AOM)/dextran sulfate sodium (DSS) model was used in this study. Lactulose treatment was performed by feeding 2% lactulose for 14 weeks. Stool samples collected at 4 time points were used for metagenomic analysis of the microbiota. Pathological analysis was performed 21 weeks after AOM injection. AOM/DSS increased the macrophage counts, inflammatory cytokine expression, colorectal tumorigenesis, and imbalance in gut microbiota composition, as evidenced by increased pathogen abundance (e.g., Escherichia and Clostridium). Lactulose significantly inhibited the inflammatory events, and ameliorated inflammation and tumorigenesis. The composition of the intestinal microbiota was also restored upon lactulose treatment, and lactulose reduced pathogen abundance and increased the abundance of Muribaculum and Lachnospiraceae. Meanwhile, the pathways related to Crohn’s disease were downregulated after lactulose treatment. Our findings suggest that lactulose restores the structure and composition of the intestinal microbiota, mitigates inflammation, and suppresses inflammatory tumorigenesis.

A bioinspired stimuli-responsive amino acid-based antibacterial drug delivery system in cancer therapy

Design of tyrosine based stimuli responsive antibacterial drug delivery system with potential application in cancer therapy.

Gastrointestinal tumors and infectious agents: A wide field to explore

Infection is currently one of the main contributors to carcinogenesis. In fact, the International Agency for Research on Cancer has categorized eleven biological agents as group I carcinogens. It is estimated that around 16% of the 12.7 million new cancers diagnosed in 2008 were attributable to infectious agents. Although underdeveloped regions carry the highest incidence rates, about 7.4% of infection-related cancer cases occur in developed areas. Physicians are increasingly aware of the potential carcinogenic role of common virus like the Human Papilloma virus in cervical cancer, or the hepatitis B and C viruses in hepatocarcinoma. However, the carcinogenic role of several other infectious agents is less recognized. Given that gastrointestinal malignancies carry an overall poor prognosis, a better understanding of the carcinogenic mechanisms triggered by infectious agents is key to decrease the rate of cancer related deaths. Preventive measures directed to such infections would ideally impact survival. In this paper we review the main pathogenic mechanisms related to the development of gastrointestinal malignancies induced by infectious microorganisms and other pathogens which are currently under investigation.

Mucosa-Associated Escherichia coli in Colorectal Cancer Patients and Control Subjects: Variations in the Prevalence and Attributing Features

Accumulating evidence indicates that specific strains of mucosa-associated Escherichia coli (E. coli) can influence the development of colorectal carcinoma. This study aimed to investigate the prevalence and characterization of mucosa-associated E. coli obtained from the colorectal cancer (CRC) patients and control group. At two referral university-affiliated hospitals in northwest Iran, 100 patients, 50 with CRC and 50 without, were studied over the course of a year. Fresh biopsy specimens were used to identify mucosa-associated E. coli isolates after dithiothreitol mucolysis. To classify the E. coli strains, ten colonies per sample were typed using enterobacterial repetitive intergenic consensus-based PCR (ERIC-PCR). The strains were classified into phylogroups using the quadruplex PCR method. The PCR method was used to examine for the presence of cyclomodulin, bfp, stx1, stx2, and eae-encoding genes. The strains were tested for biofilm formation using the microtiter plate assay. CRC patients had more mucosa-associated E. coli than the control group (p < 0.05). Enteropathogenic Escherichia coli (EPEC) was also found in 23% of CRC strains and 7.1% of control strains (p < 0.05). Phylogroup A was predominant in control group specimens, while E. coli isolates from CRC patients belonged most frequently to phylogroups D and B2. Furthermore, the frequency of cyclomodulin-encoding genes in the CRC patients was significantly higher than the control group. Around 36.9% of E. coli strains from CRC samples were able to form biofilms, compared to 16.6% E. coli strains from the control group (p < 0.05). Noticeably, cyclomodulin-positive strains were more likely to form biofilm in comparison to cyclomodulin-negative strains (p < 0.05). In conclusion, mucosa-associated E. coli especially cyclomodulin-positive isolates from B2 and D phylogroups possessing biofilm-producing capacity colonize the gut mucosa of CRC patients.

Bacteria-Cancer Interface: Awaiting the Perfect Storm

Epidemiological evidence reveal a very close association of malignancies with chronic inflammation as a result of persistent bacterial infection. Recently, more studies have provided experimental evidence for an etiological role of bacterial factors disposing infected tissue towards carcinoma. When healthy cells accumulate genomic insults resulting in DNA damage, they may sustain proliferative signalling, resist apoptotic signals, evade growth suppressors, enable replicative immortality, and induce angiogenesis, thus boosting active invasion and metastasis. Moreover, these cells must be able to deregulate cellular energetics and have the ability to evade immune destruction. How bacterial infection leads to mutations and enriches a tumour-promoting inflammatory response or micro-environment is still not clear. In this review we showcase well-studied bacteria and their virulence factors that are tightly associated with carcinoma and the various mechanisms and pathways that could have carcinogenic properties.

Escherichia coli and colorectal cancer: Unfolding the enigmatic relationship

Colorectal cancer (CRC) is one of the deadliest cancers in the world. Specific strains of intestinal Escherichia coli (E. coli) may influence the initiation and development of CRC by exploiting virulence factors and inflammatory pathways. Mucosa-associated E. coli strains are more prevalent in CRC biopsies in comparison to healthy controls. Moreover, these strains can survive and replicate within macrophages and induce a pro-inflammatory response. Chronic exposure to inflammatory mediators can lead to increased cell proliferation and cancer. Production of colobactin toxin by the majority of mucosa-associated E. coli isolated from CRC patients is another notable finding. Colibactin-producing E. coli strains, in particular, induce double-strand DNA breaks, stop the cell cycle, involve in chromosomal rearrangements of mammalian cells and are implicated in carcinogenic effects in animal models. Moreover, some enteropathogenic E. coli (EPEC) strains are able to survive and replicate in colon cells as chronic intracellular pathogens and may promote susceptibility to CRC by downregulation of DNA Mismatch Repair (MMR) proteins. In this review, we discuss current evidence and focus on the mechanisms by which E. coli can influence the development of CRC.