Chronic liver disease enables gut Enterococcus faecalis colonization to promote liver carcinogenesis

Microbiota mechanisms in cancer progression and therapy

The composition of the microbiota in patients has been shown to correlate with cancer progression and response to therapy, highlighting unique opportunities to improve patient outcomes. In this review, we discuss the challenges and advancements in understanding the chemical mechanisms of specific microbiota species, pathways, and molecules involved in cancer progression and treatment. We also describe the modulation of cancer and immunotherapy by the microbiota, along with approaches for investigating microbiota enzymes and metabolites. Elucidating these specific microbiota mechanisms and molecules should offer new opportunities for developing enhanced diagnostics and therapeutics to improve outcomes for cancer patients. Nonetheless, many microbiota mechanisms remain to be determined and require innovative chemical genetic approaches.

Malignant tumors in vagal-innervated organs: Exploring its homeostatic role

Cancer remains a significant global health challenge, with its progression shaped by complex and multifactorial mechanisms. Recent research suggests that the vagus nerve could play a critical role in mediating communication between the tumor microenvironment and the central nervous system (CNS). This review highlights the diversity of vagal afferent receptors, which could position the vagus nerve as a unique pathway for transmitting immune, metabolic, mechanical, and chemical signals from tumors to the CNS. Such signaling could influence systemic disease progression and tumor-related responses. Additionally, the vagus nerve's interactions with the microbiome and the renin-angiotensin system (RAS)-both implicated in cancer biology-further underscore its potential central role in modulating tumor-related processes. Contradictions in the literature, particularly concerning vagal fibers, illustrate the complexity of its involvement in tumor progression, with both tumor-promoting and tumor-suppressive effects reported depending on cancer type and context. These contradictions often overlook certain experimental biases, such as the failure to distinguish between vagal afferent and efferent fibers during vagotomies or the localized parasympathetic effects that cannot always be extrapolated to the systemic level. By focusing on the homeostatic role of the vagus nerve, understanding these mechanisms could open the door to new perspectives in cancer research related to the vagus nerve and lead to potential therapeutic innovations.

Reduction of Bacteroides fragilis in Gut Microbiome of Chronic Hepatitis B Patients Promotes Liver Injury

In chronic hepatitis B (CHB) patients under antiviral treatment, liver injury, as evidenced by elevated alanine transaminase (ALT), is associated with unfavorable outcomes and needs effective treatment. The interaction between gut microbiota and liver injury in CHB patients remains unclear. Using a case-control design, 28 cases with elevated ALT and 28 matched controls with normal ALT were randomly selected from CHB patients with viral control. Clinical characteristics were comparable between groups. Metagenomic sequencing revealed that Bacteroides fragilis was decreased in cases and exhibited the greatest disparity between cases and controls. Mice colonized by gut microbiota from cases exhibited more severe liver damage in both LPS-induced and MCD diet-induced liver injury models, and had a lower abundance of B. fragilis compared to mice colonized by gut microbiota from controls. Oral gavage of B. fragilis improved both LPS-induced and MCD diet-induced liver injury. Metabolomics analysis revealed that the levels of 7-Ketolithocholic acid (7-Keto-LCA) were positively correlated with B. fragilis and significantly increased in the cultural supernatant of B. fragilis. Consistently, 7-Keto-LCA exerted protective effects against both LPS-induced and MCD diet-induced liver damage. Targeting gut microbiota might be a promising therapeutic treatment for alleviation residual liver inflammation in CHB patients with viral control.

The gut microbiota is altered significantly in primary diffuse large b-cell lymphoma patients and relapse refractory diffuse large b-cell lymphoma patients

PURPOSE

Studies have shown that the gut microbiota may affect anti-tumor immunity by regulating the host immune system and tumor microenvironment. To date, little is known about whether the gut microbiota underlies the occurrence of diffuse large B-cell lymphoma (DLBCL) and drug resistance.

METHODS

In the present study, we compared the gut microbiota structure of fecal samples from 26 patients with primary DLBCL, 28 patients with relapsed and refractory (RR) DLBCL, and 30 healthy people.

RESULTS

Notably, Fusobacteria (from phylum to species) was enriched in the primary group. A decrease of Fusobacterium and an increase of Enterococcus were found in the RR group. PICRUSt analysis found that genes related to cytochrome P450 were upregulated in the RR group compared to the primary group, which likely contributes to the occurrence of DLBCL and the formation of drug resistance.

CONCLUSIONS

Our study provides further evidence for the relationship between gut microbiota and DLBCL and the formation of drug resistance, highlighting the potential significance of the bacterial variations may be used as new biomarkers of DLBCL.

Diet-microbiome interactions in cancer

Diet impacts cancer in diverse manners. Multiple nutritional effects on tumors are mediated by dietary modulation of commensals, residing in mucosal surfaces and possibly also within the tumor microenvironment. Mechanistically understanding such diet-microbiome-host interactions may enable to develop precision nutritional interventions impacting cancer development, dissemination, and treatment responses. However, data-driven nutritional strategies integrating diet-microbiome interactions are infrequently incorporated into cancer prevention and treatment schemes. Herein, we discuss how dietary composition affects cancer-related processes through alterations exerted by specific nutrients and complex foods on the microbiome. We highlight how dietary timing, including time-restricted feeding, impacts microbial function in modulating cancer and its therapy. We review existing and experimental nutritional approaches aimed at enhancing microbiome-mediated cancer treatment responsiveness while minimizing adverse effects, and address challenges and prospects in integrating diet-microbiome interactions into precision oncology. Collectively, mechanistically understanding diet-microbiome-host interactomes may enable to achieve a personalized and microbiome-informed optimization of nutritional cancer interventions.

Faecal Cytolysin is Associated With Worse Survival in Patients With Primary Sclerosing Cholangitis

BACKGROUND AND AIMS

Primary sclerosing cholangitis (PSC) is an immune-related cholangiopathy without treatment options beyond liver transplantation. The gut-liver axis, especially the role of gut microbes, has emerged as a crucial pathway contributing to PSC pathogenesis. Recent research has revealed Enterococcus (E.) faecalis and its virulence factor cytolysin to increase mortality risk in patients with alcohol-associated hepatitis. Thus, we studied the role of enterococci, particularly E. faecalis and its virulence factor genes cytolysin and gelatinase, in faecal samples from patients with PSC.

METHODS

To assess the relevance of Enterococcus species, we performed 16S rRNA gene amplicon analysis in faecal samples from 60 patients with PSC. We validated our findings by qPCR of faecal microbial DNA in an extended cohort of 105 patients with PSC, 104 patients with inflammatory bowel disease (IBD) and 68 healthy subjects.

RESULTS

High-throughput 16S rRNA amplicon analysis revealed an increased relative abundance of enterococci in PSC patients compared with healthy controls and IBD patients, respectively, (p < 0.0001). PSC patients with high enterococci abundance had a decreased probability of transplant-free survival (p = 0.028). E. faecalis and its virulence factors cytolysin and gelatinase were more abundant in patients with PSC. Higher faecal cytolysin was associated with lower overall survival (p = 0.04), while survival was independent of gelatinase levels.

CONCLUSION

Our data highlight the association of E. faecalis and faecal cytolysin with lower survival in patients with PSC. These data should prompt further research into the pathogenic role of cytolysin-positive E. faecalis, and to explore its role as a potential therapeutic target.

Gut microbiota-mediated gut-liver axis: a breakthrough point for understanding and treating liver cancer

The trillions of commensal microorganisms living in the gut lumen profoundly influence the physiology and pathophysiology of the liver through a unique gut-liver axis. Disruptions in the gut microbial communities, arising from environmental and genetic factors, can lead to altered microbial metabolism, impaired intestinal barrier and translocation of microbial components to the liver. These alterations collaboratively contribute to the pathogenesis of liver disease, and their continuous impact throughout the disease course plays a critical role in hepatocarcinogenesis. Persistent inflammatory responses, metabolic rearrangements and suppressed immunosurveillance induced by microbial products underlie the pro-carcinogenic mechanisms of gut microbiota. Meanwhile, intrahepatic microbiota derived from the gut also emerges as a novel player in the development and progression of liver cancer. In this review, we first discuss the causes of gut dysbiosis in liver disease, and then specify the pivotal role of gut microbiota in the malignant progression from chronic liver diseases to hepatobiliary cancers. We also delve into the cellular and molecular interactions between microbes and liver cancer microenvironment, aiming to decipher the underlying mechanism for the malignant transition processes. At last, we summarize the current progress in the clinical implications of gut microbiota for liver cancer, shedding light on microbiota-based strategies for liver cancer prevention, diagnosis and therapy.

Biosocial Determinants of Health Among Patients with Chronic Liver Disease and Liver Cancer

BACKGROUND

Metabolic disorders and chronic liver disease (CLD) play crucial roles in the development and progression of liver cancer (LC). Since the ethnic minority population increasingly suffers from CLD and LC, it is vital to understand the biosocial factors contributing to CLD and LC. The 'All of Us' database, with significant participation from minority populations, provides a valuable tool for studies in different racial/ethnic groups. Using different databases, including the 'All of Us' and 'The Cancer Genome Atlas', this study aimed to understand the biosocial factors contributing to CLD and LC.

METHODS

Using 'All of Us' data, confounding factors like the lack of immunization, comorbidities, and socioeconomic status (SES) barriers were analyzed in a cohort of 33767 CLD [non-alcoholic fatty liver disease, alcoholic liver disease, and Hepatitis B and C] patients. Among the 556 LC patients in the 'All of Us' database, 92% had CLD. Since hypoxanthine is known to be increased in the urine of LC patients, purine metabolic pathway genes were analyzed using different databases and validated using publicly available RNASeq data.

RESULTS

We identified several confounding factors associated with CLD in Hispanic (HA) and African American (AA) populations compared to the non-Hispanic White (NHW) populations. HA and AA CLD patients suffer from high SES barriers. While most of the genes related to the purine metabolic pathway were upregulated in LC, xanthine dehydrogenase (XDH), which converts hypoxanthine to uric acid, showed a downregulation in the tumor compared to the normal tissues. The TCGA data among different racial/ethnic groups showed that only in Asian (AN) LC tumors the XDH expression was significantly lower compared to the NHW. The decreased XDH mRNA expression in AN LC compared to benign tissues was further validated using publicly available RNAseq datasets. Survival analysis confirmed poor overall survival among the AN LC patients with lower XDH expression in their tumors.

CONCLUSIONS

Our study identified several confounding factors contributing to the minority CLD population. This study also identified decreased XDH expression as a critical metabolic alteration that has clinical significance in AN LC patients.

Influence of gut microbial metabolites on tumor immunotherapy: mechanisms and potential natural products

In recent years, tumor immunotherapy has made significant breakthroughs in the treatment of malignant tumors. However, individual differences in efficacy have been observed in clinical practice. There is increasing evidence that gut microbial metabolites influence the efficacy of distal tumor immunotherapy via the gut-liver axis, the gut-brain axis and the gut-breast axis, a process that may involve modulating the expression of immune cells and cytokines in the tumor microenvironment (TME). In this review, we systematically explore the relationship between gut microbial metabolites and tumor immunotherapy, and examine the corresponding natural products and their mechanisms of action. The in-depth exploration of this research area will provide new ideas and strategies to enhance the efficacy of tumor immunotherapy and mitigate adverse effects.

Characterization of liver, adipose, and fecal microbiome in obese patients with MASLD: links with disease severity and metabolic dysfunction parameters

BACKGROUND

Metabolic dysfunction-associated steatotic liver disease (MASLD) encompasses a range of histological findings from the generally benign simple steatosis to steatohepatitis (MASH) which can progress to fibrosis and cirrhosis. Several factors, including the microbiome, may contribute to disease progression.

RESULTS

Here, we demonstrate links between the presence and abundance of specific bacteria in the adipose and liver tissues, inflammatory genes, immune cell responses, and disease severity. Overall, in MASLD patients, we observed a generalized obesity-induced translocation of gut bacteria to hepatic and adipose tissues. We identified microbial patterns unique to more severely diseased tissues. Specifically, Enterococcus, Granulicatella, and Morganellaceae abundance is positively correlated with immune cell counts and inflammatory gene expression levels, and both genera are significantly enriched in MASH patients. Brevibacterium is enriched in adipose tissues of patients with liver fibrosis.

CONCLUSION

Together, these results provide further insight into the microbial factors that may be driving disease severity. Video Abstract.

Gut-liver translocation of pathogen Klebsiella pneumoniae promotes hepatocellular carcinoma in mice

Hepatocellular carcinoma (HCC) is accompanied by an altered gut microbiota but whether the latter contributes to carcinogenesis is unclear. Here we show that faecal microbiota transplantation (FMT) using stool samples from patients with HCC spontaneously initiate liver inflammation, fibrosis and dysplasia in wild-type mice, and accelerate disease progression in a mouse model of HCC. We find that HCC-FMT results in gut barrier injury and translocation of live bacteria to the liver. Metagenomic analyses and bacterial culture of liver tissues reveal enrichment of the gut pathogen Klebsiella pneumoniae in patients with HCC and mice transplanted with the HCC microbiota. Moreover, K. pneumoniae monocolonization recapitulates the effect of HCC-FMT in promoting liver inflammation and hepatocarcinogenesis. Mechanistically, K. pneumoniae surface protein PBP1B interacts with and activates TLR4 on HCC cells, leading to increased cell proliferation and activation of oncogenic signalling. Targeting gut colonization using K. oxytoca or TLR4 inhibition represses K. pneumoniae-induced HCC progression. These findings indicate a role for an altered gut microbiota in hepatocarcinogenesis.

Microbial characteristics of bile in gallstone patients: a comprehensive analysis of 9,939 cases

Introduction

The exact triggers of gallstone formation remain incompletely understood, but research indicates that microbial infection is a significant factor and can interfere with treatment. There is no consensus on the bile microbial culture profiles in previous studies, and determining the microbial profile could aid in targeted prevention and treatment. The primary aim of this study is to investigate the differences in microbial communities cultured from bile specimens of patients with gallstones.

Methods

We collected the clinical characteristics and bile microbial status of 9,939 gallstone patients. Statistical analysis was employed to assess the relationship between microbes and clinical features, and a random forest model was utilized to predict recurrence.

Results

Results showed a higher proportion of females among patients, with the age group of 60-74 years being the most prevalent. The most common type of gallstone was solitary gallbladder stones. A total of 76 microbes were cultured from 5,153 patients, with Escherichia coli, Klebsiella pneumoniae, and Enterococcus faecalis being the most frequently identified. Significant differences in microbial diversity and positive detection rates were observed across different age groups, types of gallstones, and recurrence status. Positive frequencies of E. coli, Enterococcus faecium, and K. pneumoniae varied significantly by age group and gallstone type. The microbial diversity in the recurrence group was significantly lower compared to the non-recurrence group. The recurrence rate was significantly higher in the group with single microbial species compared to those with no microbes or multiple microbes. For the recurrence group, there were significant differences in the frequencies of seven microbes (Aeromonas hydrophila, Enterococcus casseliflavus, Enterococcus faecium, E. coli, K. pneumoniae, Proteus mirabilis, Pseudomonas aeruginosa) before and after recurrence, with these microbes appearing in a higher number of patients after recurrence. Regression analysis identified patient age, stone size, diabetes, venous thrombosis, liver cirrhosis, malignancy, coronary heart disease, and the number of microbial species as important predictors of recurrence. A random forest model constructed using these variables demonstrated good performance and high predictive ability (ROC-AUC = 0.862).

Discussion

These findings highlight the significant role of microbial communities in gallstone formation and recurrence. Furthermore, the identified predictors of recurrence, including clinical factors and microbial diversity, may help develop personalized prevention and recurrence strategies for gallstone patients.

Distinct alterations of gut microbiota between viral- and non-viral-related hepatocellular carcinoma

Altered gut microbiota has been connected to hepatocellular carcinoma (HCC) occurrence and advancement. This study was conducted to identify a gut microbiota signature in differentiating between viral-related HCC (Viral-HCC) and non-hepatitis B-, non-hepatitis C-related HCC (NBNC-HCC). Fecal specimens were obtained from 16 healthy controls, 33 patients with viral-HCC (17 and 16 cases with hepatitis B virus (HBV) and hepatitis C virus (HCV) infection, respectively), and 18 patients with NBNC-HCC. Compositions of fecal microbiota were assessed by 16S rRNA sequencing. Bioinformatic analysis was performed by the DADA2 pipeline in the R program. Significantly different genera from the top 50 relative abundance were used to classify between subgroups of HCC by the Random Forest algorithm. Our data demonstrated that the HCC group had a significantly decreased alpha-diversity and changed microbial composition in comparison with healthy controls. Within the top 50 relative abundance, there were 11 genera including Faecalibacterium, Agathobacter, and Coprococcus that were significantly enhanced in Viral-HCC, while 5 genera such as Bacteroides, Streptococcus, Ruminococcus gnavus group, Parabacteroides, and Erysipelatoclostridium were enhanced in NBNC-HCC. Compared to Viral-HCC, the NBNC-HCC subgroup significantly reduced various short-chain fatty acid-producing bacteria, as well as declined fecal butyrate but elevated plasma surrogate markers of microbial translocation. Based on the machine learning algorithm, a high diagnostic accuracy to classify HCC subgroups was achieved with an area under the receiver-operating characteristic (ROC) curve (AUC) of 0.94. Collectively, these data revealed that gut dysbiosis was distinct according to etiological factors of HCC, which might play an essential role in hepatocarcinogenesis. These findings underscore the possible use of a gut microbiota signature for the diagnosis and therapeutic approaches regarding different subgroups of HCC. KEY POINTS: • Gut dysbiosis is connected to hepatocarcinogenesis and can be used as a novel biomarker. • Gut microbiota composition is significantly altered in different etiological factors of HCC. • Microbiota-based signature can accurately distinguish between Viral-HCC and NBNC-HCC.

Age-related features of the intestinal microbiota changes in Wistar rat pups after application of antibiotics and prebiotic 2′-fucosyllactose

The gut microbiota plays an important role in the formation of the body’s regulatory systems (nervous, endocrine, immune), which is especially important at an early age. Hence, gut dysbiosis can lead to an impaired development of both the intestinal microbiota and these regulatory systems. Prebiotics can have a positive effect on the development of the intestinal microbiome, which can correct negative changes.

The aim of this study is to investigate the features of development of antibiotic-associated dysbiosis in the early postnatal period in rats and to evaluate the effect of 2′-fucosyllactose in health and during dysbiosis.

The study was conducted on Wistar rats aged 12–26 days. To develop dysbiosis at an early age, the following mixtures were used: a mixture of ampicillin trihydrate 75 mg/kg and metronidazole 50 mg/kg and a mixture of amoxicillin 30 mg/kg and cephalexin 20 mg/kg for three days, starting on the 12th day of life. As a prebiotic 2′-fucosyllactose at a dose of 1 g/kg was used, starting on the 12th day and to the last experiment day.

In healthy animals, there is a decrease in the gut content of Bifidobacterium spp. and Enterococcus spp. at the age  of 26 days. A mixture of ampicillin trihydrate 75 mg/kg and metronidazole 50 mg/kg leads to gut dysbiosis – growth suppression of bifidobacteria, lactobacilli and enterococci. After the end of antibiotics application and continued lactation,  the titer of the described bacteria is restored. 2′-fucosyllactose has an effect on the preservation of the titer of Bifidobacterium spp. and Enterococcus spp., both in healthy animals and after early dysbiosis.

Our results indicate that antibiotic-associated dysbiosis at an early age is characterized by a temporary but powerful effect. At the same time, the use of 2′-fucosyllactose leads to preserving important probiotic groups of intestinal bacteria, both in health and after dysbiosis.

Enterococcus faecalis co-cultured with oral cancer cells exhibits higher virulence and promotes cancer cell survival, proliferation, and migration: an in vitro study

Introduction. Enterococcus faecalis is a common pathogen associated with many oral diseases and is often isolated from oral cancer patients. However, limited information is available on its key virulence gene expression in oral cancer cell microenvironment and cancer cell behaviour in co-culture studies.Hypothesis. E. faecalis overexpresses virulence genes when co-cultured with oral cancer cells and possibly alters the tumour microenvironment, promoting oral cancer proliferation and survival.Aim. To investigate altered virulence gene expression in E. faecalis and oral cancer cell behaviour using in vitro co-culture experiments.Methodology. Cal27 cells were co-cultured with E. faecalis and assessed for their cell proliferation, apoptosis, migration and clonogenicity using standard cell culture assays. The levels of reactive oxygen species (ROS) and inflammatory cytokines, along with proliferative, angiogenic and apoptotic biomarker expressions, were also assessed. E. faecalis adherence to cancer cells was demonstrated by the gentamicin protection assay. Real time-PCR was used to analyse the expression of virulence genes.Results. Co-culture of Cal27 cells with E. faecalis showed significantly higher cell proliferation, migration and clonogenicity compared to the control (P<0.01). A significant increase in the levels of ROS and inflammatory cytokines and overexpression of Ki67, vascular endothelial growth factor, extracellular signal-regulated kinase 1/2, phosphoinositide 3 kinase and Akt was observed in the co-culture group. E. faecalis also downregulated p53 and Bax genes while upregulated Bcl-2. The virulence genes GelE, Asa and Ace were overexpressed in E. faecalis co-cultured with Cal27 cells.Conclusion. The results from this study indicate the possible risks of E. faecalis infection in oral cancer. An effective antibiotic strategy against E. faecalis to prevent complications associated with oral diseases, including cancer, is needed.

Enterococcus faecalis: an overlooked cell invader

SUMMARYEnterococcus faecalis and Enterococcus faecium are human pathobionts that exhibit a dual lifestyle as commensal and pathogenic bacteria. The pathogenic lifestyle is associated with specific conditions involving host susceptibility and intestinal overgrowth or the use of a medical device. Although the virulence of E. faecium appears to benefit from its antimicrobial resistance, E. faecalis is recognized for its higher pathogenic potential. E. faecalis has long been considered a predominantly extracellular pathogen; it adheres to and is taken up by a wide range of mammalian cells, albeit with less efficiency than classical intracellular enteropathogens. Carbohydrate structures, rather than proteinaceous moieties, are likely to be primarily involved in the adhesion of E. faecalis to epithelial cells. Consistently, few adhesins have been implicated in the adhesion of E. faecalis to epithelial cells. On the host side, very little is known about cognate receptors, except for the role of glycosaminoglycans during macrophage infection. Several lines of evidence indicate that E. faecalis internalization may involve a zipper-like mechanism as well as a macropinocytosis pathway. Conversely, E. faecalis can use several strategies to prevent engulfment in phagocytes. However, the bacterial and host mechanisms underlying cell infection by E. faecalis are still in their infancy. The most recent striking finding is the existence of an intracellular lifestyle where E. faecalis can replicate within a variety of host cells. In this review, we summarize and discuss the current knowledge of E. faecalis-host cell interactions and argue on the need for further mechanistic studies to prevent or reduce infections.

Enterococcal-host interactions in the gastrointestinal tract and beyond

The gastrointestinal tract (GIT) is typically considered the natural niche of enterococci. However, these bacteria also inhabit extraintestinal tissues, where they can disrupt organ physiology and cause life-threatening infections. Here, we discuss how enterococci, primarily Enterococcus faecalis, interact with the intestine and other host anatomical locations such as the oral cavity, heart, liver, kidney, and vaginal tract. The metabolic flexibility of these bacteria allows them to quickly adapt to new environments, promoting their persistence in diverse tissues. In transitioning from commensals to pathogens, enterococci must overcome harsh conditions such as nutrient competition, exposure to antimicrobials, and immune pressure. Therefore, enterococci have evolved multiple mechanisms to adhere, colonize, persist, and endure these challenges in the host. This review provides a comprehensive overview of how enterococci interact with diverse host cells and tissues across multiple organ systems, highlighting the key molecular pathways that mediate enterococcal adaptation, persistence, and pathogenic behavior.

Targeting microbial pathogenic mechanisms as a novel therapeutic strategy in IBD

BACKGROUND

Current therapy for patients suffering from inflammatory bowel diseases (IBD) is focused on inflammatory mechanisms exclusively and not the dysbiotic microbiota, despite growing evidence implicating a role for intestinal microbes in disease.

MAIN BODY

Ongoing research into the intestinal microbiota of IBD patients, using new technologies and/or deeper application of existing ones, has identified a number of microorganisms whose properties and behaviors warrant consideration as causative factors in disease. Such studies have implicated both bacteria and fungi in the pathogenesis of disease. Some of these organisms manifest mechanisms that should be amenable to therapeutic intervention via either conventional or novel drug discovery platforms. Of particular note is a deeper characterization of microbial derived proteases and their destructive potential.

CONCLUSION

Given the steady progress on the mechanistic role of the microbiota in inflammatory diseases, it is reasonable to anticipate a future in which therapeutics targeting microbial derived pathogenic factors play an important role in improving the lives of IBD patients.

Distinct enterotypes and dysbiosis: unraveling gut microbiota in pulmonary and critical care medicine inpatients

BACKGROUND

The gut-lung axis, pivotal for respiratory health, is inadequately explored in pulmonary and critical care medicine (PCCM) inpatients.

METHODS

Examining PCCM inpatients from three medical university-affiliated hospitals, we conducted 16S ribosomal RNA sequencing on stool samples (inpatients, n = 374; healthy controls, n = 105). We conducted statistical analyses to examine the gut microbiota composition in PCCM inpatients, comparing it to that of healthy controls. Additionally, we explored the associations between gut microbiota composition and various clinical factors, including age, white blood cell count, neutrophil count, platelet count, albumin level, hemoglobin level, length of hospital stay, and medical costs.

RESULTS

PCCM inpatients exhibited lower gut microbiota diversity than healthy controls. Principal Coordinates Analysis revealed marked overall microbiota structure differences. Four enterotypes, including the exclusive Enterococcaceae enterotype in inpatients, were identified. Although no distinctions were found at the phylum level, 15 bacterial families exhibited varying abundances. Specifically, the inpatient population from PCCM showed a significantly higher abundance of Enterococcaceae, Lactobacillaceae, Erysipelatoclostridiaceae, Clostridiaceae, and Tannerellaceae. Using random forest analyses, we calculated the areas under the receiver operating characteristic curves (AUCs) to be 0.75 (95% CIs 0.69-0.80) for distinguishing healthy individuals from inpatients. The four most abundant genera retained in the classifier were Blautia, Subdoligranulum, Enterococcus, and Klebsiella.

CONCLUSIONS

Evidence of gut microbiota dysbiosis in PCCM inpatients underscores the gut-lung axis's significance, promising further avenues in respiratory health research.

Therapeutic mechanism of Cornus Officinalis Fruit Coreon on ALI by AKT/Nrf2 pathway and gut microbiota

BACKGROUND

Acute liver injury (ALI) often precipitates severe liver function impairment and is associated with high mortality rates. Traditional Chinese Medicine (TCM) has demonstrated efficacy in mitigating hepatic damage by exhibiting anti-inflammatory effects, enhancing antioxidant activity, and modulating gut microbiota (GM). Numerous studies have identified similar or identical bioactive compounds within the Cornus Officinalis Fruit Coreon(COFO) and its flesh. Notably, Cornus Officinalis has been shown to possess potent hepatoprotective properties. However, studies on the pharmacological effects and mechanism of action of COFO for hepatoprotection have received little attention.

PURPOSE

To elucidate the mechanisms underlying the COFO effect in ALI by integrating GM gene sequencing, quantifying Short-Chain Fatty Acids (SCFAs), and examining relevant signaling pathways.

MATERIALS AND METHODS

A rat model for carbon tetrachloride (CCl4)-induced ALI was established, and the best liver protective components of COFO were selected by pathological observation and biochemical determination. The therapeutic efficacy of COFO in mitigating liver injury was elucidated through an integrated approach that included network pharmacology, biochemical indexes, 16S rDNA sequencing analyses, short-chain fatty acids, Western blotting analysis of protein levels, and immunohistochemical evaluations.

RESULTS

Pharmacological evaluation established that the n-butanol fraction (CNBP) provided optimal hepatoprotective effects. Firstly, the chemical constituents of CNBP were characterized, and its principal anti-ALI targets, such as ALI, AKT1, TNF, and IL-6, were identified through network pharmacology analysis. Secondly, experimental validation revealed that CNBP may enhance the genetic diversity of the GM, augmenting the diversity of the microbial community, increasing the levels of three SCFAs, and activating key proteins in the AKT/Nrf2 signaling pathway (AKT1, TNF-α, IL-6, NF-κB p65, Nrf2, and HO-1). Consequently, CNBP exhibited hepatoprotective effects, with antioxidative and anti-inflammatory properties.

CONCLUSION

CNBP may mitigate GM-induced disturbances, augment the levels of three SCFAs, activate the AKT/Nrf2 signaling pathway, and exhibit antioxidant and anti-inflammatory effects, thereby conferring hepatoprotective benefits.

Longitudinal gut fungal alterations and potential fungal biomarkers for the progression of primary liver disease

Liver disease, a major health concern worldwide, is a serious and progressive disorder. Herein, we not only established a mouse model of DEN+CCl4-induced primary liver disease but also collected clinical human samples to investigate longitudinal alterations in the gut mycobiome. As liver disease advanced, gut integrity was disrupted, and the mycobiota was disturbed in the mouse models. The metabolites associated with hepatocellular carcinoma (HCC) differed from those associated with the cirrhotic phase as follows: levels of stercobilin and aflatoxin B1 dialcohol were reduced, while levels of triterpenoids, bafilomycin A1, and DHEA were increased in the HCC group. The abundance of the phylum Chytridiomycota increased as the chronic liver disease progressed and was then replaced by the phylum Ascomycota in HCC. Based on the results from clinical human samples, the genus Candida (Ascomycota) (in humans) and the genus Kazachstania (Ascomycota) (in mice) occupied a dominant position in the HCC group, while other fungi were depleted. The increased abundance of C. albicans and depletion of S. cerevisiae may be hallmarks of the progression of liver cirrhosis to early HCC. Moreover, the administration of C. albicans and S. cerevisiae in the LC-HCC progression could accelerate or retard the progression of HCC. Therefore, gut fungi have the potential to serve as a noninvasive clinical biomarker and even a treatment method.

A Review of the Mechanisms of Bacterial Colonization of the Mammal Gut

A healthy animal intestine hosts a diverse population of bacteria in a symbiotic relationship. These bacteria utilize nutrients in the host's intestinal environment for growth and reproduction. In return, they assist the host in digesting and metabolizing nutrients, fortifying the intestinal barrier, defending against potential pathogens, and maintaining gut health. Bacterial colonization is a crucial aspect of this interaction between bacteria and the intestine and involves the attachment of bacteria to intestinal mucus or epithelial cells through nonspecific or specific interactions. This process primarily relies on adhesins. The binding of bacterial adhesins to host receptors is a prerequisite for the long-term colonization of bacteria and serves as the foundation for the pathogenicity of pathogenic bacteria. Intervening in the adhesion and colonization of bacteria in animal intestines may offer an effective approach to treating gastrointestinal diseases and preventing pathogenic infections. Therefore, this paper reviews the situation and mechanisms of bacterial colonization, the colonization characteristics of various bacteria, and the factors influencing bacterial colonization. The aim of this study was to serve as a reference for further research on bacteria-gut interactions and improving animal gut health.

The role of the microbiome in liver disease

PURPOSE OF REVIEW

The intestinal microbiome and the gut-liver axis play a major role in health and disease. The human gut harbors trillions of microbes and a disruption of the gut homeostasis can contribute to liver disease. In this review, the progress in the field within the last 3 years is summarized, focusing on metabolic dysfunction-associated steatotic liver disease (MASLD), alcohol-associated liver disease (ALD), autoimmune liver disease (AILD), and hepatocellular carcinoma (HCC).

RECENT FINDINGS

Changes in the fecal virome and fungal mycobiome have been described in patients with various liver diseases. Several microbial derived metabolites including endogenous ethanol produced by bacteria, have been mechanistically linked to liver disease such as MASLD. Virulence factors encoded by gut bacteria contribute to ALD, AILD and HCC. Novel therapeutic approaches focused on the microbiome including phages, pre- and postbiotics have been successfully used in preclinical models. Fecal microbiota transplantation has been effective in attenuating liver disease. Probiotics are safe in patients with alcohol-associated hepatitis and improve liver disease and alcohol addiction.

SUMMARY

The gut-liver axis plays a key role in the pathophysiology of liver diseases. Understanding the microbiota in liver disease can help to develop precise microbiota centered therapies.

In Vitro Lactic Acid Bacteria Anti-Hepatitis B Virus (HBV) Effect and Modulation of the Intestinal Microbiota in Fecal Cultures from HBV-Associated Hepatocellular Carcinoma Patients

Hepatocellular carcinoma (HCC), being ranked as the top fifth most prevalent cancer globally, poses a significant health challenge, with a considerable mortality rate. Hepatitis B virus (HBV) infection stands as the primary factor contributing to HCC, presenting substantial challenges in its treatment. This study aimed to identify lactic acid bacteria (LAB) with anti-HBV properties and evaluate their impact on the intestinal flora in HBV-associated HCC. Initially, two LAB strains, Levilactobacillus brevis SR52-2 (L. brevis SR52-2) and LeviLactobacillus delbrueckii subsp. bulgaicus Q80 (L. delbrueckii Q80), exhibiting anti-HBV effects, were screened in vitro from a pool of 498 LAB strains through cell experiments, with extracellular expression levels of 0.58 ± 0.05 and 0.65 ± 0.03, respectively. These strains exhibited the capability of inhibiting the expression of HBeAg and HBsAg. Subsequent in vitro fermentation, conducted under simulated anaerobic conditions mimicking the colon environment, revealed a decrease in pH levels in both the health control (HC) and HCC groups influenced by LAB, with a more pronounced effect observed in the HC group. Additionally, the density of total short-chain fatty acids (SCFAs) significantly increased (p < 0.05) in the HCC group. Analysis of 16S rRNA highlighted differences in the gut microbiota (GM) community structure in cultures treated with L. brevis SR52-2 and L. delbrueckii Q80. Fecal microflora in normal samples exhibited greater diversity compared to HBV-HCC samples. The HCC group treated with LAB showed a significant increase in the abundance of the phyla Firmicutes, Bacteroidetes and Actinobacteria, while Proteobacteria significantly decreased compared to the untreated HCC group after 48 h. In conclusion, the findings indicate that LAB, specifically L. brevis SR52-2 and L. delbrueckii Q80, possessing antiviral properties, contribute to an improvement in gastrointestinal health.

An emerging strategy: probiotics enhance the effectiveness of tumor immunotherapy via mediating the gut microbiome

The occurrence and progression of tumors are often accompanied by disruptions in the gut microbiota. Inversely, the impact of the gut microbiota on the initiation and progression of cancer is becoming increasingly evident, influencing the tumor microenvironment (TME) for both local and distant tumors. Moreover, it is even suggested to play a significant role in the process of tumor immunotherapy, contributing to high specificity in therapeutic outcomes and long-term effectiveness across various cancer types. Probiotics, with their generally positive influence on the gut microbiota, may serve as effective agents in synergizing cancer immunotherapy. They play a crucial role in activating the immune system to inhibit tumor growth. In summary, this comprehensive review aims to provide valuable insights into the dynamic interactions between probiotics, gut microbiota, and cancer. Furthermore, we highlight recent advances and mechanisms in using probiotics to improve the effectiveness of cancer immunotherapy. By understanding these complex relationships, we may unlock innovative approaches for cancer diagnosis and treatment while optimizing the effects of immunotherapy.

The gut-liver axis and gut microbiota in health and liver disease

The trillions of microorganisms in the human intestine are important regulators of health, and disruptions in the gut microbial communities can cause disease. The gut, liver and immune system have a symbiotic relationship with these microorganisms. Environmental factors, such as high-fat diets and alcohol consumption, can disrupt and alter microbial communities. This dysbiosis can lead to dysfunction of the intestinal barrier, translocation of microbial components to the liver and development or progression of liver disease. Changes in metabolites produced by gut microorganisms can also contribute to liver disease. In this Review, we discuss the importance of the gut microbiota in maintenance of health and the alterations in microbial mediators that contribute to liver disease. We present strategies for modulation of the intestinal microbiota and/or their metabolites as potential treatments for liver disease.

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.

Hepatocellular Carcinoma Prevention in the Era of Hepatitis C Elimination

The hepatitis C virus (HCV), a single-stranded RNA virus belonging to the Flaviviridae family, is a major cause of hepatocellular carcinoma (HCC) worldwide. Tumors caused by HCC have an increased mortality rate globally, which is more accentuated in Western countries. The carcinogenic potential of this virus is mediated through a wide range of mechanisms, spanning from the induction of chronic inflammation to oxidative stress and deregulation of cellular pathways by viral proteins. As the number of new infections continues unabated, HCC-related mortality should be prioritized through early detection, continued prevention of HCV transmission, and treatment of HCV with safe and efficacious direct antiviral agents (DAAs). People who inject drugs (PWID) are a significant reservoir of new HCV infections globally, and in order to eliminate hepatitis C as a global health threat, as set out by the World Health Organization, an integrated approach based on the optimization of care delivery and increased access to harm reduction and treatment for PWID is needed. Thanks to the development of safe and effective antiviral agents, eradication of the infection is now possible in almost all treated patients, leading to a significant reduction but not the elimination of the risk for HCC in cured patients. This is particularly relevant among aged populations who have cofactors of morbidity known to accelerate HCC progression, such as diabetes, obesity, and excessive alcohol consumption. Given the restless accumulation of individuals with cured HCV infection, the implementation of risk-stratified surveillance programs becomes impellent from a cost-effectiveness perspective, whereas the availability of a performant biomarker to predict HCC in cured patients remains an unmet clinical need.

Direct and indirect effects of pathogenic bacteria on the integrity of intestinal barrier

Bacterial translocation is a pathological process involving migration of pathogenic bacteria across the intestinal barrier to enter the systemic circulation and gain access to distant organs. This phenomenon has been linked to a diverse range of diseases including inflammatory bowel disease, pancreatitis, and cancer. The intestinal barrier is an innate structure that maintains intestinal homeostasis. Pathogenic infections and dysbiosis can disrupt the integrity of the intestinal barrier, increasing its permeability, and thereby facilitating pathogen translocation. As translocation represents an essential step in pathogenesis, a clear understanding of how barrier integrity is disrupted and how this disruption facilitates bacterial translocation could identify new routes to effective prophylaxis and therapy. In this comprehensive review, we provide an in-depth analysis of bacterial translocation and intestinal barrier function. We discuss currently understood mechanisms of bacterial-enterocyte interactions, with a focus on tight junctions and endocytosis. We also discuss the emerging concept of bidirectional communication between the intestinal microbiota and other body systems. The intestinal tract has established 'axes' with various organs. Among our regulatory systems, the nervous, immune, and endocrine systems have been shown to play pivotal roles in barrier regulation. A mechanistic understanding of intestinal barrier regulation is crucial for the development of personalized management strategies for patients with bacterial translocation-related disorders. Advancing our knowledge of barrier regulation will pave the way for future research in this field and novel clinical intervention strategies.

Western diet influences on microbiome and carcinogenesis

The intestinal microbiota composition and associated bioactivities are sensitive to various modifier cues such as stress, inflammation, age, life-style and nutrition, which in turn are associated with susceptibility to developing cancer. Among these modifiers, diet has been shown to influence both microbiota composition as well as being an important source of microbial-derived compounds impacting the immunological, neurological and hormonal systems. Thus, it is necessary to take a holistic view when considering effect of diet on health and diseases. In this review, we focus on the interplay between western diet, the microbiota and cancer development by dissecting key components of the diet and leveraging data from human interventions and pre-clinical studies to better understand this relationship. We highlight key progress as well as stressing limitations in this field of research.

Pathogenesis of Hepatocellular Carcinoma: The Interplay of Apoptosis and Autophagy

The pathogenesis of hepatocellular carcinoma (HCC) is a multifactorial process that has not yet been fully investigated. Autophagy and apoptosis are two important cellular pathways that are critical for cell survival or death. The balance between apoptosis and autophagy regulates liver cell turnover and maintains intracellular homeostasis. However, the balance is often dysregulated in many cancers, including HCC. Autophagy and apoptosis pathways may be either independent or parallel or one may influence the other. Autophagy may either inhibit or promote apoptosis, thus regulating the fate of the liver cancer cells. In this review, a concise overview of the pathogenesis of HCC is presented, with emphasis on new developments, including the role of endoplasmic reticulum stress, the implication of microRNAs and the role of gut microbiota. The characteristics of HCC associated with a specific liver disease are also described and a brief description of autophagy and apoptosis is provided. The role of autophagy and apoptosis in the initiation, progress and metastatic potential is reviewed and the experimental evidence indicating an interplay between the two is extensively analyzed. The role of ferroptosis, a recently described specific pathway of regulated cell death, is presented. Finally, the potential therapeutic implications of autophagy and apoptosis in drug resistance are examined.

The Microbiome and Liver Cancer

ABSTRACT

The gut microbiome and liver are anatomically and functionally connected. The impact of the gut microbiota or microbial metabolites on liver cancer progression via immune cells has been recently revealed across various preclinical models. Commensal gut microbes of liver cancer patients differ from control subjects, and their composition is affected by the etiology of the hepatocellular carcinoma. The gut microbiota represents a potential novel target for intervention as shown in patients with melanoma, but we still lack data in patients with hepatocellular carcinoma. Fecal microbiota transplantation and dietary approaches may improve immunotherapy efficacy, and a couple of clinical trials are ongoing. In liver cancer, the ongoing recognition of interactions between gut microbes and the tumor immune microenvironment provides an exciting therapeutic avenue to complement established immunotherapy.

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.

Anti-diabetic prospects of dietary bio-actives of millets and the significance of the gut microbiota: A case of finger millet

Finger millet (Eleusine coracana) is a staple food in several parts of the world because of its high nutritional value. In addition to its high nutrient content, finger millet contains numerous bioactive compounds, including polyphenol (10.2 mg/g TAE), flavonoid (5.54 mg/g CE), phytic acid (0.48%), and dietary fiber (15-20%). Polyphenols are known for their anti-oxidant and anti-diabetic role. Phytic acid, previously considered an anti-nutritive substance, is now regarded as a nutraceutical as it reduces carbohydrate digestibility and thus controls post-prandial glucose levels and obesity. Thus, finger millet is an attractive diet for patients with diabetes. Recent findings have revealed that the anti-oxidant activity and bio-accessibility of finger millet polyphenols increased significantly (P < 0.05) in the colon, confirming the role of the gut microbiota. The prebiotic content of finger millet was also utilized by the gut microbiota, such as Faecalibacterium, Eubacterium, and Roseburia, to generate colonic short-chain fatty acids (SCFAs), and probiotic Bifidobacterium and Lactobacillus, which are known to be anti-diabetic in nature. Notably, finger millet-induced mucus-degrading Akkermansia muciniphila can also help in alleviate diabetes by releasing propionate and Amuc_1100 protein. Various millet bio-actives effectively controlled pathogenic gut microbiota, such as Shigella and Clostridium histolyticum, to lower gut inflammation and, thus, the risk of diabetes in the host. In the current review, we have meticulously examined the role of gut microbiota in the bio-accessibility of millet compounds and their impact on diabetes.

Probiotic Lactobacilli ameliorate alcohol-induced hepatic damage via gut microbial alteration

Alcoholic liver disease (ALD), which includes fatty liver, cirrhosis, steatosis, fibrosis, and hepatocellular carcinoma, is a global health problem. The probiotic effects of lactic acid bacteria (LAB) are well-known; however, their protective effect against ALD remains unclear. Therefore, in this study, our objective was to assess the protective effects of LAB on ALD. To this end, mice were fed either a normal diet or an alcohol diet for 10 days (to induce ALD) accompanied by vehicle treatment (the NC and AC groups) or kimchi-derived LAB (Lactiplantibacillus plantarum DSR J266 and Levilactobacillus brevis DSR J301, the AL group; or Lacticaseibacillus rhamnosus GG, the AG group). Our results showed that mice in the AC group showed significantly higher serum aspartate aminotransferase and alanine aminotransferase levels than those in the normal diet groups; however, their levels in the AL and AG groups were relatively lower. We also observed that the AL and AG groups showed relatively lower interleukin-6 levels than the AC group. Additionally, AC group showed the accumulation of several fat vesicles in the liver, while the AL and AG groups showed remarkably lower numbers of fat vesicles. The relative abundance of Enterococcus feacalis, which showed association with liver injury, significantly increased in the AC group compared with its levels in the normal diet groups. However, the AG group showed a decreased relative abundance in this regard, confirming that LAB exerted an improvement effect on gut microbial community. These findings suggested that via gut microbiota alteration, the ingestion of LAB can alleviate the ill effects of alcohol consumption, including inflammation, liver damage, gut dysbiosis, and abnormal intestinal nutrient metabolism.

Elevation of enterococcus-specific antibodies associated with bacterial translocation is predictive of survival rate in chronic liver disease

INTRODUCTION/PURPOSE

The gut-liver axis contributes to disease progression, a rise in infection rate, organ failure and a poor overall outcome in chronic liver diseases (CLD). Monitoring of the gut-liver axis is critical in understanding disease status, but biomarkers have not been elucidated. The aim of this study is to determine the level of serum antibodies against Enterococcus (E.) faecalis in evaluating patients with CLD, including those treated with rifaximin (a minimally absorbed antibiotic), and in patients with alcohol-associated liver disease (ALD).

MATERIALS AND METHODS

We enrolled 109 CLD patients (cohort 1), 30 hepatic encephalopathy patients treated with rifaximin (cohort 2), 53 inpatients with ALD undergoing alcohol cessation (cohort 3) and 33 healthy subjects. To assess the consequences of E. faecalis translocation, we developed an assay for the detection of a serum antibody against E. faecalis capsular polysaccharide (E.CPS).

RESULTS

Serum E.CPS antibody titer was elevated only in those patients with advanced CLD and ALD. The E.CPS antibody titer was an independent prognostic factor (p < 0.05), while Mac-2 binding protein and albumin-bilirubin score were not independent predictors of survival. The improvement of predictive model in integrated factors was significant [continuous net reclassification index (value 0.699, p < 0.05) and integrated discrimination improvement (value 0.164, p = 0.051)]. Furthermore, rifaximin treatment led to a decrease of serum E.CPS antibody titer resulting in a significantly longer overall rate of survival.

CONCLUSION

The E.CPS antibody titer appears to be a strong predictor of survival in CLD patients. Serum E.CPS levels decrease in CLD patients receiving rifaximin, and may be associated with an overall improvement in rate of survival.

Cancer as microenvironmental, systemic and environmental diseases: opportunity for transdisciplinary microbiomics science

Cancer is generally regarded as a localised disease, with the well-established role of the tumour microenvironment. However, the realm of cancer goes beyond the tumour microenvironment, and cancer should also be regarded as a systemic and environmental disease. The exposome (ie, the totality of exposures), which encompasses diets, supplements, smoking, alcohol, other lifestyle factors, medications, etc, likely alters the microbiome (inclusive of bacteria, viruses, archaea, fungi, parasites, etc) and immune system in various body sites and influences tumour phenotypes. The systemic metabolic/inflammatory status, which is likely influenced by exposures and intestinal physiological changes, may affect tissue microenvironment of colorectum and any other organs. Germline genomic factors can modify disease phenotypes via gene-by-environment interactions. Although challenges exist, it is crucial to advance not only basic experimental research that can analyse the effects of exposures, microorganisms and microenvironmental components on tumour evolution but also interdisciplinary human population research that can dissect the complex pathogenic roles of the exposome, microbiome and immunome. Metagenomic, metatranscriptomic and metabolomic analyses should be integrated into well-designed population research combined with advanced methodologies of artificial intelligence and molecular pathological epidemiology. Ideally, a prospective cohort study design that enables biospecimen (such as stool) collection before disease detection should be considered to address reverse causation and recall biases. Robust experimental and observational research together can provide insights into dynamic interactions between environmental exposures, microbiota, tumour and immunity during carcinogenesis processes, thereby helping us develop precision prevention and therapeutic strategies to ultimately reduce the cancer burden.

The role of immune cells in the liver tumor microenvironment: an involvement of gut microbiota-derived factors

More than 500 species of microbiota reside in the human intestine and coexist with humans, their host. Gut microbial metabolites and components are absorbed from the intestine and influence cells in the liver, including hepatocytes and stromal cells, such as liver sinusoidal endothelial cells, hepatic stellate cells, Kupffer cells, natural killer (NK) cells, NK T cells, and other immune cells. This gut-originated axis to the liver is called the "gut-liver axis", which underscores the importance of the link between the gut and the liver. In this review, we discuss the gut microbial components and metabolites that affect cells in the liver, particularly in association with immune cells, and the related responses. We also highlight the mechanisms underlying gut microbiota-mediated liver carcinogenesis and discuss cancer prevention, including the recently clarified modulation of immune checkpoint inhibitor efficacy by the gut microbiota.

Adaptation of the gut pathobiont Enterococcus faecalis to deoxycholate and taurocholate bile acids

Enterococcus faecalis is a natural inhabitant of the human gastrointestinal tract. This bacterial species is subdominant in a healthy physiological state of the gut microbiota (eubiosis) in adults, but can become dominant and cause infections when the intestinal homeostasis is disrupted (dysbiosis). The relatively high concentrations of bile acids deoxycholate (DCA) and taurocholate (TCA) hallmark eubiosis and dysbiosis, respectively. This study aimed to better understand how E. faecalis adapts to DCA and TCA. We showed that DCA impairs E. faecalis growth and possibly imposes a continuous adjustment in the expression of many essential genes, including a majority of ribosomal proteins. This may account for slow growth and low levels of E. faecalis in the gut. In contrast, TCA had no detectable growth effect. The evolving transcriptome upon TCA adaptation showed the early activation of an oligopeptide permease system (opp2) followed by the adjustment of amino acid and nucleotide metabolisms. We provide evidence that TCA favors the exploitation of oligopeptide resources to fuel amino acid needs in limiting oligopeptide conditions. Altogether, our data suggest that the combined effects of decreased DCA and increased TCA concentrations can contribute to the rise of E. faecalis population during dysbiosis.

The microbiome, gastrointestinal cancer, and immunotherapy

The gastrointestinal tract greatly contributes to global cancer burden and cancer-related deaths. The microbiota represents the population of microorganisms that live in and around the body, located primarily in the gastrointestinal tract. The microbiota has been implicated in colorectal cancer development and progression, but its role in cancer therapy for the gastrointestinal tract is less defined, especially for extra-intestinal cancers. In this review, we discuss the past 5 years of research into microbial involvement in immune-related therapies for colorectal, pancreatic, hepatic, and gastric cancers, with the goal of highlighting recent advances and new areas for investigation in this field.