Microbial Interactions and Interventions in Colorectal Cancer

Exploring the Relationship between Ovarian Cancer and Genital Microbiota: A Systematic Review and Meta-Analysis

Ovarian cancer (OC) remains a significant health challenge globally, with high mortality rates despite advancements in treatment. Emerging research suggests a potential link between OC development and genital dysbiosis, implicating alterations in the microbiome composition as a contributing factor. To investigate this correlation, a meta-analysis was conducted following PRISMA and MOOSE guidelines, involving eight studies encompassing 3504 patients. Studies investigating the role of upper and inferior genital tract dysbiosis were included, with particular reference to HPV infection and/or history of pelvic inflammatory disease. The analysis revealed no significant difference in genital dysbiosis prevalence between OC patients and healthy controls. Although previous literature suggests associations between dysbiosis and gynecologic cancers, such as cervical and endometrial cancers, the findings regarding OC are inconclusive. Methodological variations and environmental factors may contribute to these discrepancies, underscoring the need for standardized methodologies and larger-scale studies. Despite the limitations, understanding the microbiome's role in OC development holds promise for informing preventive and therapeutic strategies. A holistic approach to patient care, incorporating microbiome monitoring and personalized interventions, may offer insights into mitigating OC risk and improving treatment outcomes. Further research with robust methodologies is warranted to elucidate the complex interplay between dysbiosis and OC, potentially paving the way for novel preventive and therapeutic approaches.

The potential role of Listeria monocytogenes in promoting colorectal adenocarcinoma tumorigenic process

BACKGROUND

Listeria monocytogenes is a foodborne pathogen, which can cause a severe illness, especially in people with a weakened immune system or comorbidities. The interactions between host and pathogens and between pathogens and tumor cells have been debated in recent years. However, it is still unclear how bacteria can interact with tumor cells, and if this interaction can affect tumor progression and therapy.

METHODS

In this study, we evaluated the involvement of L. monocytogenes in pre-neoplastic and colorectal cancer cell proliferation and tumorigenic potential.

RESULTS

Our findings showed that the interaction between heat-killed L. monocytogenes and pre-neoplastic or colorectal cancer cells led to a proliferative induction; furthermore, by using a three-dimensional cell culture model, the obtained data indicated that L. monocytogenes was able to increase the tumorigenic potential of both pre-neoplastic and colorectal cancer cells. The observed effects were then confirmed as L. monocytogenes-specific, using Listeria innocua as negative control. Lastly, data suggested the Insulin Growth Factor 1 Receptor (IGF1R) cascade as one of the possible mechanisms involved in the effects induced by L. monocytogenes in the human colorectal adenocarcinoma cell line.

CONCLUSIONS

These findings, although preliminary, suggest that the presence of pathogenic bacterial cells in the tumor niches may directly induce, increase, and stimulate tumor progression.

The State-of-the-Art Mechanisms and Antitumor Effects of Somatostatin in Colorectal Cancer: A Review

Somatostatin, a somatotropin release inhibiting factor (SST, SRIF), is a widely distributed multifunctional cyclic peptide and acts through a transmembrane G protein-coupled receptor (SST1-SST5). Over the past decades, research has begun to reveal the molecular mechanisms underlying the anticancer activity of this hormonal peptide. Among gastrointestinal tract (GIT) tumors, direct and indirect antitumor effects of SST have been documented best in gastroenteropancreatic neuroendocrine tumors (GEP-NETs) and less well in non-endocrine cancers, including sporadic colorectal cancer (CRC). In the latter, the signaling pathways involved in the antitumor function of SST are primarily MAPK/ERK/AKT and Wnt/β-catenin. Direct (involving the MAPK pathway) and indirect (VEGF production) antiangiogenic effects of SST in CRC have also been described. The anti-inflammatory role of SST in CRC is emphasized, but detailed molecular mechanisms are still being explored. The role of SST in tumor genome/tumor microenvironment (TME)/host's gut microbiome interactions is only partially known. The results of SST analogues (SSAs)' treatment of sporadic CRC in monotherapy in vivo are not spectacular. The current review aims to present the state-of-the-art mechanisms and antitumor activity of endogenous SST and its synthetic analogues in CRC, with particular emphasis on sporadic CRC.

Implications of Gut Microbiota in Epithelial-Mesenchymal Transition and Cancer Progression: A Concise Review

Advancement in the development of molecular sequencing platforms has identified infectious bacteria or viruses that trigger the dysregulation of a set of genes inducing the epithelial-mesenchymal transition (EMT) event. EMT is essential for embryogenesis, wound repair, and organ development; meanwhile, during carcinogenesis, initiation of the EMT can promote cancer progression and metastasis. Recent studies have reported that interactions between the host and dysbiotic microbiota in different tissues and organs, such as the oral and nasal cavities, esophagus, stomach, gut, skin, and the reproductive tract, may provoke EMT. On the other hand, it is revealed that certain microorganisms display a protective role against cancer growth, indicative of possible therapeutic function. In this review, we summarize recent findings elucidating the underlying mechanisms of pathogenic microorganisms, especially the microbiota, in eliciting crucial regulator genes that induce EMT. Such an approach may help explain cancer progression and pave the way for developing novel preventive and therapeutic strategies.

Probiotics Interact With Lipids Metabolism and Affect Gut Health

Probiotics have attracted much attention due to their ability to modulate host intestinal microbe, participate in nutrient metabolism or immunomodulatory. Both inflammatory bowel disease (IBD) and bowel cancer are digestive system disease, which have become a global public health problem due to their unclear etiology, difficult to cure, and repeated attacks. Disturbed gut microbiota and abnormal lipid metabolism would increase the risk of intestinal inflammation. However, the link between lipid metabolism, probiotics, and IBD is unclear. In this review, we found that different lipids and their derivatives have different effects on IBD and gut microbes. ω-3 polyunsaturated fatty acids (PUFAs) docosahexaenoic acid, eicosapentaenoic acid, and their derivatives resolvin E1, resolvin D can inhibit oxidative stress and reactive oxygen species activate NFκB and MAPk pathway. While ω-6 PUFAs linoleic acid and arachidonic acid can be derived into leukotrienes and prostaglandins, which will aggravate IBD. Cholesterol can be converted into bile acids to promote lipid absorption and affect microbial survival and colonization. At the same time, it is affected by microbial bile salt hydrolase to regulate blood lipids. Low denstiy lipoprotein (LDL) is easily converted into oxidized LDL, thereby promoting inflammation, while high denstiy lipoprotein (HDL) has the opposite effect. Probiotics compete with intestinal microorganisms for nutrients or ecological sites and thus affect the structure of intestinal microbiota. Moreover, microbial short chain fatty acids, bile salt hydrolase, superoxide dismutase, glutathione, etc. can affect lipid metabolism and IBD. In conclusion, probiotics are directly or indirectly involved in lipids metabolism and their impact on IBD, which provides the possibility to explore the role of probiotics in improving gut health.

Optimal control and Bayes inference applied to complex microbial communities

Interactions between species are essential in ecosystems, but sometimes competition dominates over mutualism. The transition between mutualism-competition can have several implications and consequences, and it has hardly been studied in experimental settings. This work studies the mutualism between cross-feeding bacteria in strains that supply an essential amino acid for their mutualistic partner when both strains are exposed to antimicrobials. When the strains are free of antimicrobials, we found that, depending on the amount of amino acids freely available in the environment, the strains can exhibit extinction, mutualism, or competition. The availability of resources modulates the behavior of both species. When the strains are exposed to antimicrobials, the population dynamics depend on the proportion of bacteria resistant to the antimicrobial, finding that the extinction of both strains is eminent for low levels of the resource. In contrast, competition between both strains continues for high levels of the resource. An optimal control problem was then formulated to reduce the proportion of resistant bacteria, which showed that under cooperation, both strains (sensitive and resistant) are immediately controlled, while under competition, only the density of one of the strains is decreased. In contrast, its mutualist partner with control is increased. Finally, using our experimental data, we did parameters estimation in order to fit our mathematical model to the experimental data.

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.

The Role of Gut Microbiota in Gastrointestinal Tract Cancers

Disturbances in gastrointestinal (GI) microbiota could play a significant role in the development of GI cancers, but the underlying mechanisms remain largely unclear. While some bacteria seem to facilitate carcinogenesis, others appear to be protective. So far only one bacterium (Helicobacter pylori) has been classified by the International Agency for Cancer Research as carcinogenic in humans but many other are the subject of intense research. Most studies on the role of microbiota in GI tract oncogenesis focus on pancreatic and colorectal cancers with the following three species: Helicobacter pylori, Escherichia coli, and Porphyromonas gingivalis as likely causative factors. This review summarizes the role of bacteria in GI tract oncogenesis.

The Fruits of Paris polyphylla Inhibit Colorectal Cancer Cell Migration Induced by Fusobacterium nucleatum-Derived Extracellular Vesicles

Colorectal cancer (CRC) is one of the most common cancers worldwide. Gut microbiota are highly associated with CRC, and Fusobacterium nucleatum was found to be enriched in CRC lesions and correlated with CRC carcinogenesis and metastases. Paris polyphylla is a well-known herbal medicine that showed anticancer activity. The present study demonstrates that P. polyphylla inhibited the growth of CRC cells. In addition, treating with active compounds pennogenin 3-O-beta-chacotrioside and polyphyllin VI isolated from P. polyphylla inhibited the growth of F. nucleatum. We also found that extracellular vesicles (EVs) released from F. nucleatum could promote mitochondrial fusion and cell invasion in CRC cells, whereas active components from P. polyphylla could dampen such an impact. The data suggest that P. polyphylla and its active ingredients could be further explored as potential candidates for developing complementary chemotherapy for the treatment of CRC.

Exploring the Role of Gut Microbiome in Colon Cancer

Dysbiosis of the gut microbiome has been associated with the development of colorectal cancer (CRC). Gut microbiota is involved in the metabolic transformations of dietary components into oncometabolites and tumor-suppressive metabolites that in turn affect CRC development. In a healthy colon, the major of microbial metabolism is saccharolytic fermentation pathways. The alpha-bug hypothesis suggested that oncogenic bacteria such as enterotoxigenic Bacteroides fragilis (ETBF) induce the development of CRC through direct interactions with colonic epithelial cells and alterations of microbiota composition at the colorectal site. Escherichia coli, E. faecalis, F. nucleatum, and Streptococcus gallolyticus showed higher abundance whereas Bifidobacterium, Clostridium, Faecalibacterium, and Roseburia showed reduced abundance in CRC patients. The alterations of gut microbiota may be used as potential therapeutic approaches to prevent or treat CRC. Probiotics such as Lactobacillus and Bifidobacterium inhibit the growth of CRC through inhibiting inflammation and angiogenesis and enhancing the function of the intestinal barrier through the secretion of short-chain fatty acids (SCFAs). Crosstalk between lifestyle, host genetics, and gut microbiota is well documented in the prevention and treatment of CRC. Future studies are required to understand the interaction between gut microbiota and host to the influence and prevention of CRC. However, a better understanding of bacterial dysbiosis in the heterogeneity of CRC tumors should also be considered. Metatranscriptomic and metaproteomic studies are considered a powerful omic tool to understand the anti-cancer properties of certain bacterial strains. The clinical benefits of probiotics in the CRC context remain to be determined. Metagenomic approaches along with metabolomics and immunology will open a new avenue for the treatment of CRC shortly. Dietary interventions may be suitable to modulate the growth of beneficial microbiota in the gut.

Gut Microbiota Manipulation as a Tool for Colorectal Cancer Management: Recent Advances in Its Use for Therapeutic Purposes

Colorectal cancer (CRC) is a multifaceted disease influenced by both environmental and genetic factors. A large body of literature has demonstrated the role of gut microbes in promoting inflammatory responses, creating a suitable microenvironment for the development of skewed interactions between the host and the gut microbiota and cancer initiation. Even if surgery is the primary therapeutic strategy, patients with advanced disease or cancer recurrence after surgery remain difficult to cure. Therefore, the gut microbiota has been proposed as a novel therapeutic target in light of recent promising data in which it seems to modulate the response to cancer immunotherapy. The use of microbe-targeted therapies, including antibiotics, prebiotics, live biotherapeutics, and fecal microbiota transplantation, is therefore considered to support current therapies in CRC management. In this review, we will discuss the importance of host-microbe interactions in CRC and how promoting homeostatic immune responses through microbe-targeted therapies may be useful in preventing/treating CRC development.

The missing heritability of familial colorectal cancer

Pinpointing heritability factors is fundamental for the prevention and early detection of cancer. Up to one-quarter of colorectal cancers (CRCs) occur in the context of familial aggregation of this disease, suggesting a strong genetic component. Currently, only less than half of the heritability of CRC can be attributed to hereditary syndromes or common risk loci. Part of the missing heritability of this disease may be explained by the inheritance of elusive high-risk variants, polygenic inheritance, somatic mosaicism, as well as shared environmental factors, among others. A great deal of the missing heritability in CRC is expected to be addressed in the coming years with the increased application of cutting-edge next-generation sequencing technologies, routine multigene panel testing and tumour-focussed germline predisposition screening approaches. On the other hand, it will be important to define the contribution of environmental factors to familial aggregation of CRC incidence. This review provides an overview of the known genetic causes of familial CRC and aims at providing clues that explain the missing heritability of this disease.

Detrimental Effect of Broad-spectrum Antibiotics on Intestinal Microbiome Diversity in Patients After Allogeneic Stem Cell Transplantation: Lack of Commensal Sparing Antibiotics

BACKGROUND

Maintaining gastrointestinal (GI) microbiome diversity plays a key role during allogeneic stem cell transplantation (ASCT), and loss of diversity correlates with acute GI graft versus host disease (GvHD) and poor outcomes.

METHODS

In this retrospective analysis of 161 ASCT patients, we used serial analyses of urinary 3-indoxyl sulfate (3-IS) levels and GI microbiome parameters within the first 10 days after ASCT to identify potential commensal microbiota-sparing antibiotics. Based on antibiotic activity, we formed 3 subgroups (Rifaximin without systemic antibiotics, Rifaximin with systemic antibiotics, and Ciprofloxacin/Metronidazole with/without systemic antibiotics).

RESULTS

Mono-antibiosis with Rifaximin revealed higher 3-IS levels (P < .001), higher Clostridium cluster XIVa (CCXIVa) abundance (P = .004), and higher Shannon indices (P = .01) compared to Ciprofloxacin/Metronidazole with/without systemic antibiotics. Rifaximin followed by systemic antibiotics maintained microbiome diversity compared to Ciprofloxacin/Metronidazole with/without systemic antibiotics, as these patients showed still higher 3-IS levels (P = .04), higher CCXIVa copy numbers (P = .01), and higher Shannon indexes (P = .01). Even for this larger cohort of patients, the outcome was superior with regard to GI GvHD (P = .05) and lower transplant-related mortality (P < .001) for patients receiving Rifaximin plus systemic antibiotics compared to other types of systemic antibiotic treatment. Antibiosis with Ciprofloxacin/Metronidazole (n = 12, P = .01), Piperacillin/Tazobactam (n = 52, P = .01), Meropenem/Vancomycin (n = 16, P = .003), Ceftazidime (n = 10, P = .03), or multiple systemic antibiotics (n = 53, P = .001) showed significantly lower 3-IS levels compared to mono-antibiosis with Rifaximin (n = 14) or intravenous Vancomycin (n = 4, not statistically significant).

CONCLUSIONS

Different types of antibiotic treatments show different impacts on markers of microbiome diversity. The identification of antibiotics sparing commensal bacteria remains an ongoing challenge. However, Rifaximin allowed a higher intestinal microbiome diversity, even in the presence of systemic broad-spectrum antibiotics.

Colorectal cancer is associated with increased circulating lipopolysaccharide, inflammation and hypercoagulability

Gut dysbiosis contributes to the development of a dysfunctional gut barrier, facilitating the translocation of bacteria and inflammagens, and is implicated in colorectal cancer (CRC) pathogenesis. Such 'leaky gut' conditions result in systemic inflammation, of which a hallmark is increased hypercoagulability. Fluorescence antibody confocal microscopy was used to determine circulating levels of lipopolysaccharide (LPS) in control and CRC populations. Here we showed that circulating levels of LPS are significantly elevated in the CRC population. We also showed that markers of inflammation and hypercoagulability are increased in this population. Furthermore, anomalous blood clotting and structural changes in blood components are presented. Importantly, the association between LPS levels, inflammation, and hematological dysfunction was analysed. Statistical regression models were applied to identify markers with strong association with CRC, and to investigate the correlation between markers. A core aim is enhanced biomarker discovery for CRC. We conclude that circulating LPS can promote systemic inflammation and contribute to the development of a pathological coagulation system, with resulting chronic inflammation and an activated coagulation system implicated in tumorigenesis. Blood-based screening tools are an emerging research area of interest for CRC screening. We propose the use of additional (novel) biomarkers to effectively screen for CRC.

Can the microbiota predict response to systemic cancer therapy, surgical outcomes, and survival? The answer is in the gut

INTRODUCTION

The gut microbiota seems to play a key role in tumorigenesis, across various hallmarks of cancer. Recent evidence suggests its potential use as a biomarker predicting drug response and adding prognostic information, generally in the context of immuno-oncology.

AREAS COVERED

In this review, we focus on the modulating effects of gut microbiota dysbiosis on various anticancer molecules used in practice, including cytotoxic and immune-modulating agents, primarily immune-checkpoint inhibitors (ICI). Pubmed/Medline-based literature search was conducted to find potential original studies that discuss gut microbiota as a prognostic and predictive biomarker for cancer therapy. We also looked at the US ClinicalTrials.gov website to find additional studies particularly ongoing human clinical trials.

EXPERT COMMENTARY

Sequencing of stool-derived materials and tissue samples from cancer patients and animal models has shown a significant enrichment of various bacteria such as Fusobacterium nucleatum and Bacteroides fragilis were associated with resistant disease and poorer outcomes. Gut microbiota was also found to be associated with surgical outcomes and seems to play a significant role in anastomotic leak (ATL) after surgery mainly by collagen breakdown. However, this research field is just at the beginning and the current findings are not yet ready to change clinical practice.

Metabolic models predict bacterial passengers in colorectal cancer

BACKGROUND

Colorectal cancer (CRC) is a complex multifactorial disease. Increasing evidence suggests that the microbiome is involved in different stages of CRC initiation and progression. Beyond specific pro-oncogenic mechanisms found in pathogens, metagenomic studies indicate the existence of a microbiome signature, where particular bacterial taxa are enriched in the metagenomes of CRC patients. Here, we investigate to what extent the abundance of bacterial taxa in CRC metagenomes can be explained by the growth advantage resulting from the presence of specific CRC metabolites in the tumor microenvironment.

METHODS

We composed lists of metabolites and bacteria that are enriched on CRC samples by reviewing metabolomics experimental literature and integrating data from metagenomic case-control studies. We computationally evaluated the growth effect of CRC enriched metabolites on over 1500 genome-based metabolic models of human microbiome bacteria. We integrated the metabolomics data and the mechanistic models by using scores that quantify the response of bacterial biomass production to CRC-enriched metabolites and used these scores to rank bacteria as potential CRC passengers.

RESULTS

We found that metabolic networks of bacteria that are significantly enriched in CRC metagenomic samples either depend on metabolites that are more abundant in CRC samples or specifically benefit from these metabolites for biomass production. This suggests that metabolic alterations in the cancer environment are a major component shaping the CRC microbiome.

CONCLUSION

Here, we show with in sillico models that supplementing the intestinal environment with CRC metabolites specifically predicts the outgrowth of CRC-associated bacteria. We thus mechanistically explain why a range of CRC passenger bacteria are associated with CRC, enhancing our understanding of this disease. Our methods are applicable to other microbial communities, since it allows the systematic investigation of how shifts in the microbiome can be explained from changes in the metabolome.

Novel cancer therapy targeting microbiome

In the human intestinal tract, there are more than 100 trillion symbiotic bacteria, which form the gut microbiota. Approximately 70% of the human immune system is in the intestinal tract, which prevents infection by pathogenic bacteria. When the intestinal microbiota is disturbed, causing dysbiosis, it can lead to obesity, diabetes mellitus, inflammatory bowel disease, rheumatoid arthritis, multiple sclerosis, autism spectrum disorder and cancer. Recent metabolomics analyses have also made the association between the microbiota and carcinogenesis clear. Here, we review the current evidence on the association between the microbiota and gastric, bladder, hepatobiliary, pancreatic, lung and colorectal cancer. Moreover, several animal studies have revealed that probiotics seem to be effective for the prevention of carcinogenesis to some extent. In this review, we focused on this relationship between the microbiota and cancer, and considered how to prevent cancer using strategies involving the gut microbiota.

The exosome secretion inhibitor neticonazole suppresses intestinal dysbacteriosis-induced tumorigenesis of colorectal cancer

Colorectal cancer (CRC) is the most frequently encountered malignancy associated with the rectum or colon, and accumulating evidences have implicated intestinal dysbacteriosis (IDB, disruption of gut microbiome) and exosomes in the pathology of CRC. We aimed to investigate the effect of IDB on exosome secretion in a CRC xenograft mouse model. An IDB mouse model was established and was inoculated with the CRC cell line SW480 as a xenograft tumor. Tumor growth was monitored for 15 days in sham and IDB mice, after which blood was collected to assess serum exosome secretion. A novel exosome secretion inhibitor, neticonazole, was administered to IDB mice bearing CRC xenograft tumors, followed by monitoring of tumor growth and mouse survival. Western blot analysis was performed in xenograft tumors to investigate the underlying molecular mechanism. IDB promoted CRC xenograft tumor growth and exosome secretion, which could be inhibited by the exosome secretion inhibitor neticonazole. Moreover, neticonazole treatment significantly improved the survival of IDB mice with CRC xenograft tumors, likely through increasing apoptosis of CRC xenograft tumor cells. The exosome secretion inhibitor neticonazole may serve as a promising therapeutic candidate against CRC by suppressing IDB-induced CRC tumorigenesis.

Efficacy of fecal microbiota transplantation in a patient with chronic intractable constipation

We have presented the first case report of FMT therapy for a patient with chronic intractable constipation. This therapy resulted in good, medium-term outcomes. Follow-up analysis of the intestinal flora suggested that transplanted microbes from the donor, particularly Bifidobacterium and Clostridium cluster IX, may have been incorporated into the recipient.

Differential expression of tumor-associated genes and altered gut microbiome with decreased Akkermansia muciniphila confer a tumor-preventive microenvironment in intestinal epithelial Pten-deficient mice

Phosphatase and tensin homolog (Pten) antagonizes PI3K-Akt signaling; therefore, Pten impairment causes tumorigenesis. However, the correlation between Pten deficiency and colon cancer has remained elusive due to numerous opposite observations. To study this correlation, we examined whether Pten deficiency in intestinal epithelial cells (IECs) induces tumorigenesis. With mucosal biopsies of human colon cancer and normal colon, Pten mRNA was evaluated by quantitative PCR. Using IEC-specific Pten knockout mice (Pten^ΔIEC/ΔIEC), we examined the mitotic activity of IECs; and Pten^ΔIEC/ΔIEC; Apc^min/+ mice were generated by combining Pten^ΔIEC/ΔIEC with Apc^min/+ mice. Tumor-associated gene was evaluated by micro-array analysis. Fecal microbiome was analyzed through 16S rRNA gene sequencing. We found that Pten mRNA level was reduced in human colon cancer relative to normal tissues. Augmented chromatids, increased Ki-67 and PCNA expression, and enhanced Akt activation were identified in IECs of Pten^ΔIEC/ΔIEC mice compared to Pten^+/+ littermate. Combining Pten^ΔIEC/ΔIEC with Apc^min/+ condition caused rapid and aggressive intestinal tumorigenesis. However, Pten^ΔIEC/ΔIEC mice did not develop any tumors. While maintaining the tumor-driving potential, these data indicated that IEC-Pten deficiency alone did not induce tumorigenesis in mice. Furthermore, the expression of tumor-promoting and tumor-suppressing genes was decreased and increased, respectively, in the intestine of Pten^ΔIEC/ΔIEC mice compared to controls. The abundance of Akkermansia muciniphila, capable of inducing chronic intestinal inflammation, was diminished in Pten^ΔIEC/ΔIEC mice compared to controls. These findings suggested that altered tumor-associated gene expression and changed gut microbiota shape a tumor-preventive microenvironment to counteract the tumor-driving potential, leading to the tumor prevention in Pten^ΔIEC/ΔIEC mice.

Oral hygiene might prevent cancer

Many evidences support that species from the Human Oral Microbiome Database such as Fusobacterium nucleatum or Bacteroides, linked previously to periodontitis and appendicitis, play a role in colorectal cancer (CRC), including metastasis. These typically oral species are invasive anaerobes that form biofilms in their virulent state. Aspirin (a NSAID) has been recently included into routine CRC prevention rationale. NSAIDs can prevent the growth of neoplastic lesions by inhibiting COX enzymes and another set of recently identified COX-independent targets, which include the WNT, AMPK and MTOR signaling pathways, the crosstalk between nucleoli and NF-κB transcriptional activity in apoptosis, and the biochemistry of platelets. These are signaling pathways related to tumor-promoting inflammation. In this process, pathogens or simple deregulation of the microbiota play an important role in CRC. Aspirin and other NSAIDs are efficient inhibitors of biofilm formation and able to control periodontitis development preventing inflammation related to the microbiota of the gingival tissue, so its seems plausible to include this pathway in the mechanisms that aspirin uses to prevent CRC. We propose arguments suggesting that current oral hygiene methods and other future developments against periodontitis might prevent CRC and probably other cancers, alone or in combination with other options; and that the multidisciplinary studies needed to prove this hypothesis might be relevant for cancer prevention.

Intestinal dysbacteriosis activates tumor-associated macrophages to promote epithelial-mesenchymal transition of colorectal cancer

In this study we investigated the association between intestinal dysbacteriosis with colorectal cancer progress and the underlying molecular mechanisms. Tumor progression was evaluated using xenograft mice model. The epithelial-mesenchymal transition (EMT) markers were quantified by both real-time PCR and immunoblotting. The serum content of IL-6 and TNF-α were measured with ELISA kits. Cell proliferation was determined by the Cell Counting Kit-8. Intestinal dysbacteriosis was successfully simulated by the administration of a large dose of antibiotics and was demonstrated to promote xenograft tumor growth and induce EMT. Accordingly, the serum concentrations of cytokines IL-6 and TNF-α were significantly increased. Furthermore, the production and secretion of IL-6 and TNF-α were remarkably elevated in macrophages isolated from intestinal dysbiotic mice in comparison with the normal counterparts, and conditioned medium from these was shown to significantly stimulate EMT process in HT29 cells in vitro. Macrophage depletion completely abrogated the pro-tumor effect of intestinal dysbacteriosis. Our results suggest that intestinal dysbacteriosis stimulates macrophage activation and subsequently induces EMT process via secreted pro-inflammatory cytokines IL-6 and TNF-α.

Immunogenicity of a Fap2 peptide mimotope of Fusobacterium nucleatum and its potential use in the diagnosis of colorectal cancer

Background

The role of Fusobacterium nucleatum Fap2 protein in the development of colorectal cancer has recently been explained. Fap2, when bound to the human inhibitory receptor, TIGIT, inhibits the cytotoxic activity of natural killer (NK) cells against cancer cells, thus, allowing proliferation of the latter eventually leading to tumor growth. The aim of the study was to identify the immunogenicity of a peptide mimotope of the Fap2 protein and to determine the reactivity of colorectal cancer patients’ sera against the mimotope.

Methods

Immunogenic epitope of the Fap2 protein of F. nucleatum was selected using the B-cell epitope prediction of the Immune Epitope Database and Analysis Resource (IEDB). The immunogenicity of the synthetic peptide mimotope of the Fap2 protein was determined in animal models and reactivity of colorectal cancer patients’ sera against the mimotope was done by indirect ELISA.

Results

Results show that the selected peptide mimotope, with sequence TELAYKHYFGT, of the outer membrane protein Fap2 of F. nucleatum is immunogenic. Increase in the absorbance readings of peptide-immunized rabbit sera was observed starting Week 1 which was sustained up to Week 10 in the indirect ELISA performed. Colorectal cancer cases (n = 37) were all reactive in an ELISA-based analysis using the mimotope as the capture antigen.

Conclusions

In this study, we identified an immunogenic epitope of the Fap2 protein of the Fusobacterium nucleatum. We demonstrated the reactivity of serum of histopathologically confirmed CRC patients in a peptide-capture indirect ELISA which may serve as proof of concept for the development of CRC diagnostics.

Role of Microbiome in Carcinogenesis Process and Epigenetic Regulation of Colorectal Cancer

Epigenetic changes during the development of colorectal cancer (CRC) play a significant role. Along with factors such as diet, lifestyle, and genetics, oncogenic infection, bacteria alone or whole microbiome, has been associated with this tumor type. How gut microbiome contributes to CRC pathogenesis in the host is not fully understood. Most of the epigenetic studies in CRC have been conducted in populations infected with Helicobacter pylori. In the current review, we summarize how the gut microbiota contributes in colon carcinogenesis and the potential role of epigenetic mechanism in gene regulation. We discuss microbiota-mediated initiation and progression of colon tumorigenesis and have also touched upon the role of microbial metabolites as an initiator or an inhibitor for procarcinogenic or antioncogenic activities. The hypothesis of gut microbiota associated CRC revealed the dynamic and complexity of microbial interaction in initiating the development of CRC. In the multifaceted processes of colonic carcinogenesis, gradual alteration of microbiota along with their microenvironment and the potential oncopathogenic microbes mediated modulation of cancer therapy and other factors involved in microbiome dysbiosis leading to the CRC have also been discussed. This review provides a comprehensive summary of the mechanisms of CRC development, the role of microbiome or single bacterial infection in regulating the processes of carcinogenesis, and the intervention by novel therapeutics. Epigenetic mechanism involved in CRC is also discussed.

Diet and microbiota linked in health and disease

Diet has shaped microbiota profiles through human evolution.

Rethinking the bile acid/gut microbiome axis in cancer

Dietary factors, probiotic agents, aging and antibiotics/medicines impact on gut microbiome composition leading to disturbances in localised microbial populations. The impact can be profound and underlies a plethora of human disorders, including the focus of this review; cancer. Compromised microbiome populations can alter bile acid signalling and produce distinct pathophysiological bile acid profiles. These in turn have been associated with cancer development and progression. Exposure to high levels of bile acids, combined with localised molecular/genome instability leads to the acquisition of bile mediated neoplastic alterations, generating apoptotic resistant proliferation phenotypes. However, in recent years, several studies have emerged advocating the therapeutic benefits of bile acid signalling in suppressing molecular and phenotypic hallmarks of cancer progression. These studies suggest that in some instances, bile acids may reduce cancer phenotypic effects, thereby limiting metastatic potential. In this review, we contextualise the current state of the art to propose that the bile acid/gut microbiome axis can influence cancer progression to the extent that classical in vitro cancer hallmarks of malignancy (cell invasion, cell migration, clonogenicity, and cell adhesion) are significantly reduced. We readily acknowledge the existence of a bile acid/gut microbiome axis in cancer initiation, however, in light of recent advances, we focus exclusively on the role of bile acids as potentially beneficial molecules in suppressing cancer progression. Finally, we theorise that suppressing aggressive malignant phenotypes through bile acid/gut microbiome axis modulation could uncover new and innovative disease management strategies for managing cancers in vulnerable cohorts.

Precision Nutrition for Targeting Lipid Metabolism in Colorectal Cancer

Cancer is a multistage and multifactorial condition with genetic and environmental factors modulating tumorogenesis and disease progression. Nevertheless, cancer is preventable, as one third of cancer deaths could be avoided by modifying key risk factors. Nutrients can directly affect fundamental cellular processes and are considered among the most important risk factors in colorectal cancer (CRC). Red and processed meat, poultry consumption, fiber, and folate are the best-known diet components that interact with colorectal cancer susceptibility. In addition, the direct association of an unhealthy diet with obesity and dysbiosis opens new routes in the understanding of how daily diet nutrients could influence cancer prognosis. In the “omics” era, traditional nutrition has been naturally evolved to precision nutrition where technical developments have contributed to a more accurate discipline. In this sense, genomic and transcriptomic studies have been extensively used in precision nutrition approaches. However, the relation between CRC carcinogenesis and nutrition factors is more complex than originally expected. Together with classical diet-nutrition-related genes, nowadays, lipid-metabolism-related genes have acquired relevant interest in precision nutrition studies. Lipids regulate very diverse cellular processes from ATP synthesis and the activation of essential cell-signaling pathways to membrane organization and plasticity. Therefore, a wide range of tumorogenic steps can be influenced by lipid metabolism, both in primary tumours and distal metastasis. The extent to which genetic variants, together with the intake of specific dietary components, affect the risk of CRC is currently under investigation, and new therapeutic or preventive applications must be explored in CRC models. In this review, we will go in depth into the study of co-occurring events, which orchestrate CRC tumorogenesis and are essential for the evolution of precision nutrition paradigms. Likewise, we will discuss the application of precision nutrition approaches to target lipid metabolism in CRC.