Downregulation of the farnesoid X receptor promotes colorectal tumorigenesis by facilitating enterotoxigenic Bacteroides fragilis colonization

Nontoxigenic Bacteroides fragilis: A double-edged sword

The contribution of commensal microbes to human health and disease is unknown. Bacteroides fragilis (B. fragilis) is an opportunistic pathogen and a common colonizer of the human gut. Nontoxigenic B. fragilis (NTBF) and enterotoxigenic B. fragilis (ETBF) are two kinds of B. fragilis. NTBF has been shown to affect the host immune system and interact with gut microbes and pathogenic microbes. Previous studies indicated that certain strains of B. fragilis have the potential to serve as probiotics, based on their observed relationship with the immune system. However, several recent studies have shown detrimental effects on the host when beneficial gut bacteria are found in the digestive system or elsewhere. In some pathological conditions, NTBF may have adverse reactions. This paper presents a comprehensive analysis of NTBF ecology from the host-microbe perspective, encompassing molecular disease mechanisms analysis, bacteria-bacteria interaction, bacteria-host interaction, and the intricate ecological context of the gut. Our review provides much-needed insights into the precise application of NTBF.

Microbial metabolite trimethylamine-N-oxide induces intestinal carcinogenesis through inhibiting farnesoid X receptor signaling

PURPOSE

Microbial dysbiosis is considered as a hallmark of colorectal cancer (CRC). Trimethylamine-N-oxide (TMAO) as a gut microbiota-dependent metabolite has recently been implicated in CRC development. Nevertheless, evidence relating TMAO to intestinal carcinogenesis remains largely unexplored. Herein, we aimed to examine the crucial role of TMAO in CRC progression.

METHODS

Apcmin/+ mice were treated with TMAO or sterile PBS for 14 weeks. Intestinal tissues were isolated to evaluate the effects of TMAO on the malignant transformation of intestinal adenoma. The gut microbiota of mouse feces was detected by 16S rRNA sequencing analysis. HCT-116 cells were used to provide further evidence of TMAO on the progression of CRC.

RESULTS

TMAO administration increased tumor cell and stem cell proliferation, and decreased apoptosis, accompanied by DNA damage and gut barrier impairment. Gut microbiota analysis revealed that TMAO induced changes in the intestinal microbial community structure, manifested as reduced beneficial bacteria. Mechanistically, TMAO bound to farnesoid X receptor (FXR), thereby inhibiting the FXR-fibroblast growth factor 15 (FGF15) axis and activating the Wnt/β-catenin signaling pathway, whereas the FXR agonist GW4064 could blunt TMAO-induced Wnt/β-catenin pathway activation.

CONCLUSION

The microbial metabolite TMAO can enhance intestinal carcinogenesis by inhibiting the FXR-FGF15 pathway.

Enterotoxigenic Bacteroides fragilis (ETBF) Enhances Colorectal Cancer Cell Proliferation and Metastasis Through HDAC3/miR-139-3p Pathway

Enterotoxigenic Bacteroides fragilis (ETBF) is believed to promote the malignant process of colorectal cancer (CRC), but the underlying molecular mechanism still needs to be revealed. CRC cells (SW480 and HCT-116) were treated with ETBF strain. Cell proliferation, invasion and, migration were evaluated by cell counting kit 8 assay, EdU assay, colony formation assay, transwell assay, and wound healing assay. Protein expression was analyzed by western blot. MicroRNA (miR)-139-3p and histone deacetylase 3 (HDAC3) expression levels in tissues and cells were determined by qRT-PCR. Xenograft tumor model was conducted to evaluate the effect of miR-139-3p on CRC tumor growth. ETBF treatment could promote CRC cell proliferation, invasion and migration. MiR-139-3p expression was decreased by ETBF, and its overexpression reversed the effect of ETBF on CRC cell progression. HDAC3 negatively regulated miR-139-3p expression, and its overexpression facilitated CRC cell behaviors via reducing miR-139-3p expression. Moreover, HDAC3 expression was increased by ETBF, and its knockdown also abolished ETBF-mediated CRC cell progression. Additionally, miR-139-3p overexpression could reduce CRC tumor growth in vivo. ETBF aggravated CRC proliferation and metastasis via the regulation of HDAC3/miR-139-3p axis. The discovery of ETBF/HDAC3/miR-139-3p axis may provide a new direction for CRC treatment.

Comparison of fresh and browning lotus roots (Nelumbo nucifera Gaertn.) on modulating cholesterol metabolism via decreasing hepatic cholesterol deposition and increasing fecal bile acid excretion

Lotus root (LR) is prone to browning after harvest due to the oxidation of phenolic compounds by polyphenol oxidase (PPO). This study compared the effects of LR extract and BLR extract on cholesterol metabolism in high-fat diet (HFD) mice. Our findings highlighted the innovative potentiality of BLR extract in effectively regulating cholesterol metabolism via inhibiting the intestinal FXR-FGF15 signaling pathway and boosting probiotics in gut microbiota, offering valuable insights for hypercholesterolemia and metabolic disorders. In detail, catechin was the main phenolic compound in LR, while after browning, theaflavin was the main oxidation product of phenolic compounds in BLR. Both the intake of LR extract and BLR extract regulated the disorder of cholesterol metabolism induced by HFD. In particular, BLR extract intake exhibited more robust effects on increasing the BAs contents synthesized in the liver and excreted in feces compared with LR extract intake. Furthermore, the consumption of BLR extract was more effective than that of LR extract in reducing the ileal protein expressions of FXR and FGF15 and shifting BAs biosynthesis from the classical pathway to the alternative pathway. Moreover, LR extract and BLR extract had distinct effects on the gut microbiota in HFD-fed mice: BLR extract significantly elevated probiotics Akkermansia abundance, while LR extract increased Lactobacillus abundance. Therefore, both LR extract and BLR extract improved the cholesterol deposition effectively and BLR extract even showed a stronger effect on regulating key gene and protein expressions of cholesterol metabolism.

Preliminary exploration of the effects of environmental factors on the microsatellite status of BRAF-mutated colorectal cancer

BACKGROUND

To investigate the expression of EBV products and frequency of gallstone disease (GD) among different microsatellite status in colorectal cancer (CRC) with BRAFV600E mutation.

METHODS

We collected 30 CRC patients with BRAFV600E mutation and 10 BRAF ( -) CRC patients as well as 54 healthy subjects. Tumor tissue samples were collected to detect the mutation of BRAF, KRAS, and TP53. Microsatellite status was determined by immunohistochemistry and PCR. EBER in situ hybridization was performed to detect EBV. In addition, we also collected clinical information about the patients.

RESULTS

We found that although EBV products were detected in CRC, there were no significant differences in the EBV distribution between the different BRAF groups. Our study demonstrated that BRAFV600E mutation and BRAFV600E with MSI were significantly more frequent in the right CRC. Furthermore, the KRAS mutation rate in the BRAF-wild-type group was proved to be significantly higher than that in the BRAF mutation group. In addition, we revealed that BRAF mutation and MSI were independent risk factors of TNM stage. The frequency of GD was higher in CRC patients than in general population, and although there was no significant difference between CRC with or without BRAFV600E mutation, the highest frequency of GD was found in MSS CRC with BRAFV600E mutation.

CONCLUSIONS

EBV plays a role in CRC, but is not a determinant of different microsatellite status in CRC with BRAFV600E mutation. The frequency of GD in MSS CRC with BRAFV600E mutation is significantly higher than that in the general population.

Bile acid alterations associated with indolent course of inflammatory bowel disease

BACKGROUND

The indolent course of treatment-naive patients with inflammatory bowel disease (IBD) is confirmed predictable based on clinical characteristics. Current evidences supported that bile acids (BAs) alteration might be promising biomarkers in the field of IBD. We aimed to analyze the alterations of BAs as the disease progresses and explore their predictive value for indolent course of IBD.

METHODS

The indolent course of IBD was defined as a disease course without need for strict interventions throughout the entire follow-up. A targeted metabolomics method was used to detect the concentration of 27 BAs from serum sample in treatment-naive patients with IBD (Crohn's disease [CD], n = 27; ulcerative colitis [UC], n = 50). Patients with CD and UC were individually divided into two groups for further study according to the median time of indolent course. The overall BAs profile and the clinical value of BAs in predicting indolent course of IBD were identified between different groups.

RESULTS

For CD, the levels of deoxycholic acid, glycodeoxycholic acid, taurodeoxycholic acid, glycolithocholic acid-3-sulfate disodium salt and iso-lithocholic acid were significantly increased in patients with indolent course > 18 M (p < 0.05). These five BAs owned 83.5% accuracy for predicting indolent course over 18 months in CD. For UC, the concentration of deoxycholic acid and glycodeoxycholic acid were significantly higher, while dehydrocholic acid were lower in patients with indolent course > 48 M (p < 0.05). These three BAs predicted indolent course over 48 months of 69.8% accuracy in UC.

CONCLUSION

The specific BAs alterations might be potential biomarkers in predicting disease course of IBD patients.

FXR agonist GW4064 enhances anti-PD-L1 immunotherapy in colorectal cancer

Colorectal cancer (CRC) is one of the top three malignant tumors in terms of morbidity, and the limited efficacy of existing therapies urges the discovery of potential treatment strategies. Immunotherapy gradually becomes a promising cancer treatment method in recent decades; however, less than 10% of CRC patients could really benefit from immunotherapy. It is pressing to explore the potential combination therapy to improve the immunotherapy efficacy in CRC patients. It is reported that Farnesoid X receptor (FXR) is deficiency in CRC and associated with immunity. Herein, we found that GW4064, a FXR agonist, could induce apoptosis, block cell cycle, and mediate immunogenic cell death (ICD) of CRC cells in vitro. Disappointingly, GW4064 could not suppress the growth of CRC tumors in vivo. Further studies revealed that GW4064 upregulated PD-L1 expression in CRC cells via activating FXR and MAPK signaling pathways. Gratifyingly, the combination of PD-L1 antibody with GW4064 exhibited excellent anti-tumor effects in CT26 xenograft models and increased CD8+ T cells infiltration, with 33% tumor bearing mice cured. This paper illustrates the potential mechanisms of GW4064 to upregulate PD-L1 expression in CRC cells and provides important data to support the combination therapy of PD-L1 immune checkpoint blockade with FXR agonist for CRC patients.

The Emerging Roles of Human Gut Microbiota in Gastrointestinal Cancer

The gut microbiota is composed of a large number of microorganisms with a complex structure. It participates in the decomposition, digestion, and absorption of nutrients; promotes the development of the immune system; inhibits the colonization of pathogens; and thus modulates human health. In particular, the relationship between gut microbiota and gastrointestinal tumor progression has attracted widespread concern. It was found that the gut microbiota can influence gastrointestinal tumor progression in independent ways. Here, we focused on the distribution of gut microbiota in gastrointestinal tumors and further elaborated on the impact of gut microbiota metabolites, especially short-chain fatty acids, on colorectal cancer progression. Additionally, the effects of gut microbiota on gastrointestinal tumor therapy are outlined. Finally, we put forward the possible problems in gut microbiota and the gastrointestinal oncology field and the efforts we need to make.

Key Signaling in Alcohol-Associated Liver Disease: The Role of Bile Acids

Alcohol-associated liver disease (ALD) is a spectrum of diseases, the onset and progression of which are due to chronic alcohol use. ALD ranges, by increasing severity, from hepatic steatosis to alcoholic hepatitis (AH) and alcohol-associated cirrhosis (AC), and in some cases, can lead to the development of hepatocellular carcinoma (HCC). ALD continues to be a significant health burden and is now the main cause of liver transplantations in the United States. ALD leads to biological, microbial, physical, metabolic, and inflammatory changes in patients that vary depending on disease severity. ALD deaths have been increasing in recent years and are projected to continue to increase. Current treatment centers focus on abstinence and symptom management, with little in the way of resolving disease progression. Due to the metabolic disruption and gut dysbiosis in ALD, bile acid (BA) signaling and metabolism are also notably affected and play a prominent role in disease progression in ALD, as well as other liver disease states, such as non-alcoholic fatty liver disease (NAFLD). In this review, we summarize the recent advances in the understanding of the mechanisms by which alcohol consumption induces hepatic injury and the role of BA-mediated signaling in the pathogenesis of ALD.