Role of Farnesoid X Receptor and Bile Acids in Hepatic Tumor Development

Sex Dimorphic Effects of Bile Acid Metabolism in Liver Cancer in Mice

BACKGROUND & AIMS

Hepatocellular carcinoma (HCC) is a male-dominant disease, but targeted sex hormone therapies have not been successful. Bile acids are a potential liver carcinogen and are biomolecules with hormone-like effects. A few studies highlight their potential sex dimorphism in physiology and disease. We hypothesized that bile acids could be a potential molecular signature that explains sex disparity in HCC.

METHODS & RESULTS

We used the farnesoid X receptor knockout (FxrKO) mouse model to study bile acid-dependent HCC. Temporal tracking of circulating bile acids determined more than 80% of FxrKO females developed spontaneous cholemia (ie, serum total bile acids ≥40 μmol/L) as early as 8 weeks old. Opposingly, FxrKO males were highly resistant to cholemia, with ∼23% incidence even when 26 weeks old. However, FxrKO males demonstrated higher levels of deoxycholate than females. Compared with males, FxrKO females had more severe cholestatic liver injury and further aberrancies in bile acid metabolism. Yet, FxrKO females expressed more detoxification transcripts and had greater renal excretion of bile acids. Intervention with CYP7A1 (rate limiting enzyme for bile acid biosynthesis) deficiency or taurine supplementation either completely or partially normalized bile acid levels and liver injury in FxrKO females. Despite higher cholemia prevalence in FxrKO females, their tumor burden was less compared with FxrKO males. An exception to this sex-dimorphic pattern was found in a subset of male and female FxrKO mice born with congenital cholemia due to portosystemic shunt, where both sexes had comparable robust HCC.

CONCLUSIONS

Our study highlights bile acids as sex-dimorphic metabolites in HCC except in the case of portosystemic shunt.

Farnesoid X Receptor Agonist GW4064 Protects Lipopolysaccharide-Induced Intestinal Epithelial Barrier Function and Colorectal Tumorigenesis Signaling through the αKlotho/βKlotho/FGFs Pathways in Mice

The farnesoid X receptor (FXR)/βKlotho/fibroblast growth factors (FGFs) pathway is crucial for maintaining the intestinal barrier and preventing colorectal cancer (CRC). We used an FXR agonist, GW4064, and FXR-knockout (FXR-KO) mice to investigate the role of FXR/Klothos/FGFs pathways in lipopolysaccharide (LPS)-induced intestinal barrier dysfunction and colon carcinogenesis. The results showed that upregulation of FXR in enterocytes effectively ameliorated intestinal tight-junction markers (claudin1 and zonula occludens-1), inflammation, and bile acid levels, thereby protecting mice from intestinal barrier dysfunction and colon carcinogenesis. GW4064 treatment increased FXR, αKlotho, βKlotho, FGF19, FGF21, and FGF23 in wild-type mice exposed to LPS, while FXR-KO mice had decreased levels. FXR-KO mice exhibited elevated colon cancer markers (β-catenin, LGR5, CD44, CD34, and cyclin D1) under LPS, underscoring the pivotal role of FXR in inhibiting the development of colon tumorigenesis. The varying gut microbiota responses in FXR-KO mice versus wild-type mice post LPS exposure emphasize the pivotal role of FXR in preserving intestinal microbial health, involving Bacteroides thetaiotaomicron, Bacteroides acidifaciens, and Helicobacter hepaticus. Our study validates the effectiveness of GW4064 in alleviating LPS-induced disruptions to the intestinal barrier and colon carcinogenesis, emphasizing the importance of the FXR/αKlotho/βKlotho/FGFs pathway and the interplay between bile acids and gut microbiota.

Inflammatory Milieu Related to Dysbiotic Gut Microbiota Promotes Tumorigenesis of Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is an invasive primary liver cancer caused by multiple pathogenic factors and is a significant global health concern. With few effective therapeutic options, HCC is a heterogeneous carcinoma that typically arises in an inflammatory environment. Recent studies have suggested that dysbiotic gut microbiota is involved in hepatocarcinogenesis via multiple mechanisms. In this review, we discuss the effects of gut microbiota, microbial components, and microbiota-derived metabolites on the promotion and progression of HCC by feeding a persistent inflammatory milieu. In addition, we discuss the potential therapeutic modalities for HCC targeting the inflammatory status induced by gut microbiota. A better understanding of the correlation between the inflammatory milieu and gut microbiota in HCC may be beneficial for developing new therapeutic strategies and managing the disease.

Interpretation of Farnesoid X Receptor Immunohistochemical Expression in Discriminating Hepatocellular Carcinoma from Its Non-Neoplastic Mimics as an Adjunct to Glypican 3

AIMS

Differentiating hepatocellular carcinoma (HCC) and non-neoplastic lesions may be challenging. Immunohistochemistry (IHC) can help in the comparative morphologic evaluation of HCC and its mimics. Farnesoid X receptor (FXR) is a nuclear metabolic receptor essential for bile salts homeostasis and other biological functions of liver cells. Preliminary studies have shown that FXR can be useful for diagnosing HCC. This study aimed to assess the role of Farnesoid X receptor (FXR) combined with Glypican 3 (GPC3) in differentiation between HCC and non-neoplastic hepatic lesions.

MATERIAL AND METHODS

Immunohistochemistry of GPC3 and FXR was performed in 38 cases of primary hepatic lesions using an automated immunohistochemical stainer. The study included 17 primary HCC cases and 21 non-neoplastic hepatic lesions (5 cases were focal nodular hyperplasia, 7 were regenerative nodules and 9 were dysplastic nodules).

RESULTS

The percentage of positive GPC3 and low or negative FXR expression was significantly higher in HCC cases than non-neoplastic hepatic lesions (P value <0.001). The sensitivity and specificity of GPC3 in differentiating HCC from non-neoplastic hepatic lesions were 70.6% and 85.7%, respectively, while the sensitivity and specificity of FXR were 58.8% and 100%, respectively.

CONCLUSION

The present work revealed that FXR could be combined with GPC3 in distinguishing between HCC and non-neoplastic hepatic lesions with improved specificity rather than using an individual marker.

Uncovering the Gut-Liver Axis Biomarkers for Predicting Metabolic Burden in Mice

Western diet (WD) intake, aging, and inactivation of farnesoid X receptor (FXR) are risk factors for metabolic and chronic inflammation-related health issues ranging from metabolic dysfunction-associated steatotic liver disease (MASLD) to dementia. The progression of MASLD can be escalated when those risks are combined. Inactivation of FXR, the receptor for bile acid (BA), is cancer prone in both humans and mice. The current study used multi-omics including hepatic transcripts, liver, serum, and urine metabolites, hepatic BAs, as well as gut microbiota from mouse models to classify those risks using machine learning. A linear support vector machine with K-fold cross-validation was used for classification and feature selection. We have identified that increased urine sucrose alone achieved 91% accuracy in predicting WD intake. Hepatic lithocholic acid and serum pyruvate had 100% and 95% accuracy, respectively, to classify age. Urine metabolites (decreased creatinine and taurine as well as increased succinate) or increased gut bacteria (Dorea, Dehalobacterium, and Oscillospira) could predict FXR deactivation with greater than 90% accuracy. Human disease relevance is partly revealed using the metabolite-disease interaction network. Transcriptomics data were also compared with the human liver disease datasets. WD-reduced hepatic Cyp39a1 (cytochrome P450 family 39 subfamily a member 1) and increased Gramd1b (GRAM domain containing 1B) were also changed in human liver cancer and metabolic liver disease, respectively. Together, our data contribute to the identification of noninvasive biomarkers within the gut-liver axis to predict metabolic status.

Bile acid-mediated signaling in cholestatic liver diseases

Chronic cholestatic liver diseases, such as primary biliary cholangitis (PBC) and primary sclerosing cholangitis (PSC), are associated with bile stasis and gradually progress to fibrosis, cirrhosis, and liver failure, which requires liver transplantation. Although ursodeoxycholic acid is effective in slowing the disease progression of PBC, it has limited efficacy in PSC patients. It is challenging to develop effective therapeutic agents due to the limited understanding of disease pathogenesis. During the last decade, numerous studies have demonstrated that disruption of bile acid (BA) metabolism and intrahepatic circulation promotes the progression of cholestatic liver diseases. BAs not only play an essential role in nutrition absorption as detergents but also play an important role in regulating hepatic metabolism and modulating immune responses as key signaling molecules. Several excellent papers have recently reviewed the role of BAs in metabolic liver diseases. This review focuses on BA-mediated signaling in cholestatic liver disease.

FXR agonists for colorectal and liver cancers, as a stand-alone or in combination therapy

Farnesoid X receptor (FXR, NR1H4) is generally considered as a tumor suppressor of colorectal and liver cancers. The interaction between FXR, bile acids (BAs) and gut microbiota is closely associated with an increased risk of colorectal and liver cancers. Increasing evidence shows that FXR agonists may be potential therapeutic agents for colorectal and liver cancers. However, FXR agonists alone do not produce the desired results due to the complicated pathogenesis and single therapeutic mechanism, which suggests that effective treatments will require a multimodal approach. Based on the principle of improvingefficacy andreducingside effects, combination therapy is currently receiving considerable attention. In this review, colorectal and liver cancers are grouped together to discuss the effects of FXR agonists alone or in combination for combating the two cancers. We hope that this review will provide a theoretical basis for the clinical application of novel FXR agonists or combination with FXR agonists against colorectal and liver cancers.

Parabacteroides distasonis ameliorates hepatic fibrosis potentially via modulating intestinal bile acid metabolism and hepatocyte pyroptosis in male mice

Parabacteroides distasonis (P. distasonis) plays an important role in human health, including diabetes, colorectal cancer and inflammatory bowel disease. Here, we show that P. distasonis is decreased in patients with hepatic fibrosis, and that administration of P. distasonis to male mice improves thioacetamide (TAA)- and methionine and choline-deficient (MCD) diet-induced hepatic fibrosis. Administration of P. distasonis also leads to increased bile salt hydrolase (BSH) activity, inhibition of intestinal farnesoid X receptor (FXR) signaling and decreased taurochenodeoxycholic acid (TCDCA) levels in liver. TCDCA produces toxicity in mouse primary hepatic cells (HSCs) and induces mitochondrial permeability transition (MPT) and Caspase-11 pyroptosis in mice. The decrease of TCDCA by P. distasonis improves activation of HSCs through decreasing MPT-Caspase-11 pyroptosis in hepatocytes. Celastrol, a compound reported to increase P. distasonis abundance in mice, promotes the growth of P. distasonis with concomitant enhancement of bile acid excretion and improvement of hepatic fibrosis in male mice. These data suggest that supplementation of P. distasonis may be a promising means to ameliorate hepatic fibrosis.

Screening and interventions to prevent nonalcoholic fatty liver disease/nonalcoholic steatohepatitis-associated hepatocellular carcinoma

Liver cancer is the sixth most commonly diagnosed cancer worldwide, with hepatocellular carcinoma (HCC) comprising most cases. Besides hepatitis B and C viral infections, heavy alcohol use, and nonalcoholic steatohepatitis (NASH)-associated advanced fibrosis/cirrhosis, several other risk factors for HCC have been identified (i.e. old age, obesity, insulin resistance, type 2 diabetes). These might in fact partially explain the occurrence of HCC in non-cirrhotic patients without viral infection. HCC surveillance through effective screening programs is still an unmet need for many nonalcoholic fatty liver disease (NAFLD) patients, and identification of pre-cirrhotic individuals who progress to HCC represents a substantial challenge in clinical practice at the moment. Patients with NASH-cirrhosis should undergo systematic HCC surveillance, while this might be considered in patients with advanced fibrosis based on individual risk assessment. In this context, interventions that potentially prevent NAFLD/ NASH-associated HCC are needed. This paper provided an overview of evidence related to lifestyle changes (i.e. weight loss, physical exercise, adherence to healthy dietary patterns, intake of certain dietary components, etc.) and pharmacological interventions that might play a protective role by targeting the underlying causative factors and pathogenetic mechanisms. However, well-designed prospective studies specifically dedicated to NAFLD/NASH patients are still needed to clarify the relationship with HCC risk.

Metabolic profile predicts incident cancer: A large-scale population study in the UK Biobank

BACKGROUND AND AIMS

Analyses to predict the risk of cancer typically focus on single biomarkers, which do not capture their complex interrelations. We hypothesized that the use of metabolic profiles may provide new insights into cancer prediction.

METHODS

We used information from 290,888 UK Biobank participants aged 37 to 73 years at baseline. Metabolic subgroups were defined based on clustering of biochemical data using an artificial neural network approach and examined for their association with incident cancers identified through linkage to cancer registry. In addition, we evaluated associations between 38 individual biomarkers and cancer risk.

RESULTS

In total, 21,973 individuals developed cancer during the follow-up (median 3.87 years, interquartile range [IQR] = 2.03-5.58). Compared to the metabolically favorable subgroup (IV), subgroup III (defined as "high BMI, C-reactive protein & cystatin C") was associated with a higher risk of obesity-related cancers (hazard ratio [HR] = 1.26, 95 % CI = 1.21 to 1.32) and hematologic-malignancies (e.g., lymphoid leukemia: HR = 1.83, 95%CI = 1.44 to 2.33). Subgroup II ("high triglycerides & liver enzymes") was strongly associated with liver cancer risk (HR = 5.70, 95%CI = 3.57 to 9.11). Analysis of individual biomarkers showed a positive association between testosterone and greater risks of hormone-sensitive cancers (HR per SD higher = 1.32, 95%CI = 1.23 to 1.44), and liver cancer (HR = 2.49, 95%CI =1.47 to 4.24). Many liver tests were individually associated with a greater risk of liver cancer with the strongest association observed for gamma-glutamyl transferase (HR = 2.40, 95%CI = 2.19 to 2.65).

CONCLUSIONS

Metabolic profile in middle-to-older age can predict cancer incidence, in particular risk of obesity-related cancer, hematologic malignancies, and liver cancer. Elevated values from liver tests are strong predictors for later risk of liver cancer.

Hepatocellular carcinoma: Novel understandings and therapeutic strategies based on bile acids (Review)

Bile acids (BAs) are the major components of bile and products of cholesterol metabolism. Cholesterol is catalyzed by a variety of enzymes in the liver to form primary BAs, which are excreted into the intestine with bile, and secondary BAs are formed under the modification of the gut microbiota. Most of the BAs return to the liver via the portal vein, completing the process of enterohepatic circulation. BAs have an important role in the development of hepatocellular carcinoma (HCC), which may participate in the progression of HCC by recognizing receptors such as farnesoid X receptor (FXR) and mediating multiple downstream pathways. Certain BAs, such as ursodeoxycholic acid and obeticholic acid, were indicated to be able to delay liver injury and HCC progression. In the present review, the structure and function of BAs were introduced and the metabolism of BAs and the process of enterohepatic circulation were outlined. Furthermore, the mechanisms by which BAs participate in the development of HCC were summarized and possible strategies for targeting BAs and key sites of their metabolic processes to treat HCC were suggested.

Hepatocellular Carcinoma: Understanding the Inflammatory Implications of the Microbiome

Hepatocellular carcinoma (HCC) is the third leading cause of cancer-related death worldwide. It is well known that repeated inflammatory insults in the liver can cause hepatic cellular injury that lead to cirrhosis and, ultimately, hepatocellular carcinoma. Furthermore, the microbiome has been implicated in multiple inflammatory conditions which predispose patients to malignancy. With this in mind, we explore the inflammatory implications of the microbiome on pathways that lead to HCC. We also focus on how an understanding of these underlying inflammatory principles lead to a more wholistic understanding of this deadly disease, as well as potential therapeutic implications.

Genetics in Familial Intrahepatic Cholestasis: Clinical Patterns and Development of Liver and Biliary Cancers: A Review of the Literature

The family of inherited intrahepatic cholestasis includes autosomal recessive cholestatic rare diseases of childhood involved in bile acids secretion or bile transport defects. Specific genetic pathways potentially cause many otherwise unexplained cholestasis or hepatobiliary tumours in a healthy liver. Lately, next-generation sequencing and whole-exome sequencing have improved the diagnostic procedures of familial intrahepatic cholestasis (FIC), as well as the discovery of several genes responsible for FIC. Moreover, mutations in these genes, even in the heterozygous status, may be responsible for cryptogenic cholestasis in both young and adults. Mutations in FIC genes can influence serum and hepatic levels of bile acids. Experimental studies on the NR1H4 gene have shown that high bile acids concentrations cause excessive production of inflammatory cytokines, resistance to apoptosis, and increased cell regeneration, all risk conditions for developing hepatocellular carcinoma (HCC) and cholangiocarcinoma (CCA). NR1H4 gene encodes farnesoid X-activated receptor having a pivotal role in bile salts synthesis. Moreover, HCC and CCA can emerge in patients with several FIC genes such as ABCB11, ABCB4 and TJP2. Herein, we reviewed the available data on FIC-related hepatobiliary cancers, reporting on genetics to the pathophysiology, the risk factors and the clinical presentation.

Bile acids and their receptors: modulators and therapeutic targets in liver inflammation

Bile acids participate in the intestinal emulsion, digestion, and absorption of lipids and fat-soluble vitamins. When present in high concentrations, as in cholestatic liver diseases, bile acids can damage cells and cause inflammation. After the discovery of bile acids receptors about two decades ago, bile acids are considered signaling molecules. Besides regulating bile acid, xenobiotic, and nutrient metabolism, bile acids and their receptors have shown immunomodulatory properties and have been proposed as therapeutic targets for inflammatory diseases of the liver. This review focuses on bile acid-related signaling pathways that affect inflammation in the liver and provides an overview of the preclinical and clinical applications of modulators of these pathways for the treatment of cholestatic and autoimmune liver diseases.

Pleiotropic roles of FXR in liver and colorectal cancers

Nuclear receptor farnesoid X receptor (FXR) is generally considered a cell protector of enterohepatic tissues and a suppressor of liver cancer and colorectal carcinoma (CRC). Loss or reduction of FXR expression occurs during carcinogenesis, and the FXR level is inversely associated with the aggressive behaviors of the malignancy. Global deletion of FXR and tissue-specific deletion of FXR display distinct effects on tumorigenesis. Epigenetic silencing and inflammatory context are two main contributors to impaired FXR expression and activity. FXR exerts its antitumorigenic function via the following mechanisms: 1) FXR regulates multiple metabolic processes, notably bile acid homeostasis; 2) FXR antagonizes hepatic and enteric inflammation; 3) FXR impedes aberrant activation of some cancer-related pathways; and 4) FXR downregulates a number of oncogenes while upregulating some tumor suppressor genes. Restoring FXR functions via its agonists provides a therapeutic approach for patients with liver cancer and CRC. However, an in-depth understanding of the species-specific pharmacological effects is a prerequisite for assessing the clinical safety and efficacy of FXR agonists in human cancer treatment.

Norcholic Acid Promotes Tumor Progression and Immune Escape by Regulating Farnesoid X Receptor in Hepatocellular Carcinoma

Accumulating evidence shows a close association between various types of bile acids (BAs) and hepatocellular carcinoma (HCC), and they have been revealed to affect tumor immune response and progression mainly by regulating Farnesoid X receptor (FXR). Nevertheless, the roles of Norcholic acid(NorCA) in HCC progression remain unknown yet. In this study, herein we demonstrate that NorCA can promote HCC cell proliferation, migration and invasion through negatively regulating FXR. Additionally, NorCA can increase PD-L1 level on the surfaces of HCC cells and their exosomes, and NorCA-induced exosomes dramatically dampen the function of CD4⁺T cells, thereby inducing an immunosuppressive microenvironment. Meanwhile, a negative correlation between PD-L1 and FXR expression in human HCC specimens was identified, and HCC patients with FXR^lowPD-L1^high expression exhibit a rather dismal survival outcome. Importantly, FXR agonist (GW4064) can synergize with anti-PD-1 antibody (Ab) to inhibit HCC growth in tumor-bearing models. Taken together, NorCA can promote HCC progression and immune invasion by inhibiting FXR signaling, implying a superiority of the combination of FXR agonist and anti-PD-1 Ab to the monotherapy of immune checkpoint inhibitor in combating HCC. However, more well-designed animal experiments and clinical trials are warranted to further confirm our findings in future due to the limitations in our study.

miRNA-382-5p Suppresses the Expression of Farnesoid X Receptor to Promote Progression of Liver Cancer

Background

The dysregulation of microRNAs (miRNAs) and hepatotoxicity due to the aberrant accumulation of bile acids (BAs) are notorious causes that predispose an individual to the development of hepatocellular carcinoma (HCC). Farnesoid X receptor (FXR), encoded by NR1H4 gene, has been identified as a crucial BA receptor to maintain the homeostasis of BA pool and its expression is decreased in HCC. miR-382-5p plays an important role in the pathogenesis of many human malignancies and was reported to promote the proliferation and differentiation of normal liver cells and liver regeneration. However, there is still some controversy about its role in HCC microenvironment. This study aims to explore the expression pattern of miR-382-5p in HCC and its role in regulating FXR during the development of HCC.

Methods

Tissues collected from 30 HCC patients were subjected to extraction of total RNA and quantitative real-time PCR (qRT-PCR) for the analyses of miR-382-5p expression and NR1H4 mRNA levels, and their expressions were verified by analyzing the online HCC-related GSE datasets. The role of miR-382-5p in regulating cellular proliferation and expression of FXR in different HCC cell lines was analyzed by qRT-PCR, Western Blot, real-time cellular analysis (RTCA) and luciferase reporter assays. The role of miR-382-5p in regulating downstream genes of FXR in HCC cells was also analyzed.

Results

miR-382-5p was upregulated in HCC tissues and inversely associated with the downregulation of NR1H4 mRNA levels. The luciferase reporter assay proved that miR-382-5p directly targeted the 3ʹ-untranslated region (3ʹ-UTR) of human NR1H4 mRNA. Overexpression of miR-382-5p led to a malignant proliferation of HCC cells by suppressing the expression of FXR. In contrast, blocking the endogenous miR-382-5p was sufficient to suppress the cellular proliferation rate of HCC through increasing FXR expression. Additionally, miR-382-5p inhibited the expression of some target genes of FXR, including SHP, FGF19 and SLC51A, and this inhibitory effect was FXR-dependent.

Conclusion

Therefore, miR-382-5p promotes the progression of HCC in vitro by suppressing FXR and could serve as a valuable therapeutic target for HCC treatment.

Ablation of liver Fxr results in an increased colonic mucus barrier in mice

Background & Aims

The interorgan crosstalk between the liver and the intestine has been the focus of intense research. Key in this crosstalk are bile acids, which are secreted from the liver into the intestine, interact with the microbiome, and upon absorption reach back to the liver. The bile acid-activated farnesoid X receptor (Fxr) is involved in the gut-to-liver axis. However, liver-to-gut communication and the roles of bile acids and Fxr remain elusive. Herein, we aim to get a better understanding of Fxr-mediated liver-to-gut communication, particularly in colon functioning.

Methods

Fxr floxed/floxed mice were crossed with cre-expressing mice to yield Fxr ablation in the intestine (Fxr-intKO), liver (Fxr-livKO), or total body (Fxr-totKO). The effects on colonic gene expression (RNA sequencing), the microbiome (16S sequencing), and mucus barrier function by ex vivo imaging were analysed.

Results

Despite relatively small changes in biliary bile acid concentration and composition, more genes were differentially expressed in the colons of Fxr-livKO mice than in those of Fxr-intKO and Fxr-totKO mice (3272, 731, and 1824, respectively). The colons of Fxr-livKO showed increased expression of antimicrobial genes, Toll-like receptors, inflammasome-related genes and genes belonging to the ‘Mucin-type O-glycan biosynthesis’ pathway. Fxr-livKO mice have a microbiome profile favourable for the protective capacity of the mucus barrier. The thickness of the inner sterile mucus layer was increased and colitis symptoms reduced in Fxr-livKO mice.

Conclusions

Targeting of FXR is at the forefront in the battle against metabolic diseases. We show that ablation of Fxr in the liver greatly impacts colonic gene expression and increased the colonic mucus barrier. Increasing the mucus barrier is of utmost importance to battle intestinal diseases such as inflammatory bowel disease, and we show that this might be done by antagonising FXR in the liver.

Lay summary

This study shows that the communication of the liver to the intestine is crucial for intestinal health. Bile acids are key players in this liver-to-gut communication, and when Fxr, the master regulator of bile acid homoeostasis, is ablated in the liver, colonic gene expression is largely affected, and the protective capacity of the mucus barrier is increased.

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Fxr ablation in the mouse liver has a major impact on colonic gene expression.

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Fxr signalling is induced in the colons of liver Fxr knockout (Fxr-livKO) mice.

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In Fxr-livKO colons, expression of antimicrobial and mucus genes is increased.

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Microbiome of Fxr-livKO mice is indicative of enhanced mucus barrier function.

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Fxr-livKO mice have an increased mucus barrier.

Disordered farnesoid X receptor signaling is associated with liver carcinogenesis in Abcb11-deficient mice

ABCB11 encodes the bile salt export pump (BSEP), a key regulator in maintaining bile acid (BA) homeostasis. Although inherited ABCB11 mutations have previously been linked to primary liver cancer, whether ABCB11 deficiency leads to liver cancer remains unknown. Here, we analyzed ABCB11 mRNA expression levels in liver tumor specimens [29 with hepatocellular carcinoma (HCC), one with intrahepatic cholangiocarcinoma (ICC), and one with mixed HCC/ICC] with adjacent normal specimens and published human datasets. Liver tissues obtained from Abcb11-deficient (Abcb11^-/- ) mice and wild-type mice at different ages were compared by histologic, RNA-sequencing, and BA analyses. ABCB11 was significantly downregulated in human liver tumors compared with normal controls. Abcb11^-/- mice demonstrated progressive intrahepatic cholestasis and liver fibrosis, and spontaneously developed HCC and ICC over 12 months of age. Abcb11 deficiency increased BAs in the liver and serum in mice, most of which are farnesoid X receptor (FXR) antagonists/non-agonists. Accordingly, the hepatic expression and transcriptional activity of FXR were downregulated in Abcb11^-/- mouse livers. Administration of the FXR agonist obeticholic acid reduced liver injury and tumor incidence in Abcb11^-/- mice. In conclusion, ABCB11 is aberrantly downregulated and plays a vital role in liver carcinogenesis. The cholestatic liver injury and liver tumors developed in Abcb11^-/- mice are associated with increased FXR antagonist BAs and thereby decreased activation of FXR. FXR activation might be a therapeutic strategy in ABCB11 deficiency diseases. © 2021 The Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

FXR-Deoxycholic Acid-TNF-α Axis Modulates Acetaminophen-Induced Hepatotoxicity

The idiosyncratic characteristics and severity of acetaminophen (APAP) overdose-induced hepatotoxicity render identifying the predisposing factors and mechanisms of APAP-induced liver toxicity necessary and urgent. Farnesoid X receptor (FXR) controls bile acid homeostasis and modulates the progression of various liver diseases. Although global FXR deficiency in mice enhances APAP intoxication, the mechanism remains elusive. In this study, an increased sensitivity to APAP-induced toxicity was found in global Fxr-null (Fxr-/-) mice, but was not observed in hepatocyte-specific or macrophage-specific Fxr-null mice, suggesting that global FXR deficiency enhances APAP hepatotoxicity via disruption of systematic bile acid homeostasis. Indeed, more bile acid accumulation was found in global Fxr-/- mice, while 2% cholestyramine diet feeding decreased serum bile acids and alleviated APAP hepatotoxicity in global Fxr-/- mice, suggesting that bile acid accumulation contributes to APAP toxicity. Bile acids were suspected to induce macrophage to release tumor necrosis factor-α (TNF-α), which is known to enhance the APAP hepatotoxicity. In vitro, deoxycholic acid (DCA), a secondary bile acid metabolite, significantly induced Tnfa mRNA and dose-dependently enhanced TNF-α release from macrophage, while the same dose of DCA did not directly potentiate APAP toxicity in cultured primary hepatocytes. In vivo, DCA enhanced TNF-α release and potentiated APAP toxicity, both of which were abolished by the specific TNF-α antagonist infliximab. These results reveal an FXR-DCA-TNF-α axis that potentiates APAP hepatotoxicity, which could guide the clinical safe use of APAP.

Farnesoid X Receptor Activation Impairs Liver Progenitor Cell-Mediated Liver Regeneration via the PTEN-PI3K-AKT-mTOR Axis in Zebrafish

BACKGROUND AND AIMS

Following mild liver injury, pre-existing hepatocytes replicate. However, if hepatocyte proliferation is compromised, such as in chronic liver diseases, biliary epithelial cells (BECs) contribute to hepatocytes through liver progenitor cells (LPCs), thereby restoring hepatic mass and function. Recently, augmenting innate BEC-driven liver regeneration has garnered attention as an alternative to liver transplantation, the only reliable treatment for patients with end-stage liver diseases. Despite this attention, the molecular basis of BEC-driven liver regeneration remains poorly understood.

APPROACH AND RESULTS

By performing a chemical screen with the zebrafish hepatocyte ablation model, in which BECs robustly contribute to hepatocytes, we identified farnesoid X receptor (FXR) agonists as inhibitors of BEC-driven liver regeneration. Here we show that FXR activation blocks the process through the FXR-PTEN (phosphatase and tensin homolog)-PI3K (phosphoinositide 3-kinase)-AKT-mTOR (mammalian target of rapamycin) axis. We found that FXR activation blocked LPC-to-hepatocyte differentiation, but not BEC-to-LPC dedifferentiation. FXR activation also suppressed LPC proliferation and increased its death. These defects were rescued by suppressing PTEN activity with its chemical inhibitor and ptena/b mutants, indicating PTEN as a critical downstream mediator of FXR signaling in BEC-driven liver regeneration. Consistent with the role of PTEN in inhibiting the PI3K-AKT-mTOR pathway, FXR activation reduced the expression of pS6, a marker of mTORC1 activation, in LPCs of regenerating livers. Importantly, suppressing PI3K and mTORC1 activities with their chemical inhibitors blocked BEC-driven liver regeneration, as did FXR activation.

CONCLUSIONS

FXR activation impairs BEC-driven liver regeneration by enhancing PTEN activity; the PI3K-AKT-mTOR pathway controls the regeneration process. Given the clinical trials and use of FXR agonists for multiple liver diseases due to their beneficial effects on steatosis and fibrosis, the detrimental effects of FXR activation on LPCs suggest a rather personalized use of the agonists in the clinic.

Therapeutic pipeline in nonalcoholic steatohepatitis

Our understanding of nonalcoholic fatty liver disease pathophysiology continues to advance rapidly. Accordingly, the field has moved from describing the clinical phenotype through the presence of nonalcoholic steatohepatitis (NASH) and degree of fibrosis to deep phenotyping with a description of associated comorbidities, genetic polymorphisms and environmental influences that could be associated with disease progression. These insights have fuelled a robust therapeutic pipeline across a variety of new targets to resolve steatohepatitis or reverse fibrosis, or both. Additionally, some of these therapies have beneficial effects that extend beyond the liver, such as effects on glycaemic control, lipid profile and weight loss. In addition, emerging therapies for NASH cirrhosis would have to demonstrate either reversal of fibrosis with associated reduction in portal hypertension or at least delay the progression with eventual decrease in liver-related outcomes. For non-cirrhotic NASH, it is the expectation that reversal of fibrosis by one stage or resolution of NASH with no worsening in fibrosis will need to be accompanied by overall survival benefits. In this Review, we summarize NASH therapies that have progressed to phase II and beyond. We also discuss some of the potential clinical challenges with the use of these new therapies when approved.

The role of farnesoid X receptor in metabolic diseases, and gastrointestinal and liver cancer

Farnesoid X receptor (FXR) is a ligand-activated transcription factor involved in the control of bile acid (BA) synthesis and enterohepatic circulation. FXR can influence glucose and lipid homeostasis. Hepatic FXR activation by obeticholic acid is currently used to treat primary biliary cholangitis. Late-stage clinical trials investigating the use of obeticholic acid in the treatment of nonalcoholic steatohepatitis are underway. Mouse models of metabolic disease have demonstrated that inhibition of intestinal FXR signalling reduces obesity, insulin resistance and fatty liver disease by modulation of hepatic and gut bacteria-mediated BA metabolism, and intestinal ceramide synthesis. FXR also has a role in the pathogenesis of gastrointestinal and liver cancers. Studies using tissue-specific and global Fxr-null mice have revealed that FXR acts as a suppressor of hepatocellular carcinoma, mainly through regulating BA homeostasis. Loss of whole-body FXR potentiates progression of spontaneous colorectal cancer, and obesity-induced BA imbalance promotes intestinal stem cell proliferation by suppressing intestinal FXR in Apc^min/+ mice. Owing to altered gut microbiota and FXR signalling, changes in overall BA levels and specific BA metabolites probably contribute to enterohepatic tumorigenesis. Modulating intestinal FXR signalling and altering BA metabolites are potential strategies for gastrointestinal and liver cancer prevention and treatment. In this Review, studies on the role of FXR in metabolic diseases and gastrointestinal and liver cancer are discussed, and the potential for development of targeted drugs are summarized.

The pathophysiological function of non-gastrointestinal farnesoid X receptor

Farnesoid X receptor (FXR) influences bile acid homeostasis and the progression of various diseases. While the roles of hepatic and intestinal FXR in enterohepatic transport of bile acids and metabolic diseases were reviewed previously, the pathophysiological functions of FXR in non-gastrointestinal cells and tissues have received little attention. Thus, the roles of FXR in the liver, immune system, nervous system, cardiovascular system, kidney, and pancreas beyond the gastrointestinal system are reviewed herein. Gain of FXR function studies in non-gastrointestinal tissues reveal that FXR signaling improves various experimentally-induced metabolic and immune diseases, including non-alcoholic fatty liver disease, type 2 diabetes, primary biliary cholangitis, sepsis, autoimmune diseases, multiple sclerosis, and diabetic nephropathy, while loss of FXR promotes regulatory T cells production, protects the brain against ischemic injury, atherosclerosis, and inhibits pancreatic tumor progression. The downstream pathways regulated by FXR are diverse and tissue/cell-specific, and FXR has both ligand-dependent and ligand-independent activities, all of which may explain why activation and inhibition of FXR signaling could produce paradoxical or even opposite effects in some experimental disease models. FXR signaling is frequently compromised by diseases, especially during the progressive stage, and rescuing FXR expression may provide a promising strategy for boosting the therapeutic effect of FXR agonists. Tissue/cell-specific modulation of non-gastrointestinal FXR could influence the treatment of various diseases. This review provides a guide for drug discovery and clinical use of FXR modulators.

Differential roles of farnesoid X receptor (FXR) in modulating apoptosis in cancer cells

Cancer is one of the leading causes of mortality in the world. The conventional treatment strategies of cancer are surgery, radiation, and chemotherapy. However, in the advanced stage of the disease chemotherapy is the prime treatment and it is effective in only less than 10% of the patients. Therefore, there is an urgent need to find out novel therapeutic targets and delineate the mechanism of action of these targets for better management of this disease. Recent studies have shown that some of the proteins have differential role in different cancers. Therefore, it is pertinent that the targeting of these proteins should be based on the type of cancer. The nuclear receptor, FXR, is one of the vital proteins that regulate cell apoptosis. Besides, it also regulates other processes such as cell proliferation, angiogenesis, invasion, and migration. Studies suggest that the low or high expression of FXR is associated with the progression of carcinogenesis depending on the cancer types. Due to the diverse expression, it functions as both tumor suppressor and promoter. Previous studies suggest the overexpression of FXR in breast, lung, esophageal, and prostate cancer, which is related to poor survival and poor prognosis in patients. Therefore, targeting FXR with agonists and antagonists play different outcome in different cancers. Hence, this review describes the role of FXR in different cancers and the role of its inhibitors and activators for the prevention and treatment of various cancers.

The gut microbiome-bile acid axis in hepatocarcinogenesis

Hepatocellular carcinoma (HCC) is the most common primary liver malignancy and is a leading cause of cancer-related deaths globally, with few effective therapeutic options. Bile acids (BAs) are synthesized from cholesterol in the liver and can be modulated by farnesoid X receptor (FXR) and G-protein coupled BA receptor 1 (GPBAR1/TGR5). Alterations in BAs can affect hepatic metabolic homeostasis and contribute to the pathogenesis of liver cancer. Increasing evidence points to the key role of bacterial microbiota in the promotion and development of liver cancer. They are also involved in the regulation of BA synthesis and metabolism. The purpose of this review is to integrate related articles involving gut microbiota, BAs and HCC, and review how the gut microbiota-BA signaling axis can possibly influence the development of HCC.

Signaling pathways in hepatocellular carcinoma

Despite the recent introduction of new effective systemic agents, the survival of patients with hepatocellular carcinoma (HCC) at advanced stages remains dismal. This underscores the need for new therapies, which has spurred extensive research on the identification of the main drivers of pathway de-regulation as a source of novel therapeutic targets. Frequently altered pathways in HCC involve growth factor receptors (e.g., VEGFR, FGFR, TGFA, EGFR, IGFR) and/or its cytoplasmic intermediates (e.g., PI3K-AKT-mTOR, RAF/ERK/MAPK) as well as key pathways in cell differentiation (e.g., Wnt/β-catenin, JAK/STAT, Hippo, Hedgehog, Notch). Somatic mutations, chromosomal aberrations and epigenetic changes are common mechanisms for pathway deregulation in HCC. Aberrant pathway activation has also been explored as a biomarker to predict response to specific therapies, but currently, these strategies are not implemented when deciding systemic therapies in HCC patients. Beyond the well-established molecular cascades, there are numerous emerging signaling pathways also deregulated in HCC (e.g., tumor microenvironment, non-coding RNA, intestinal microbiota), which have opened new avenues for therapeutic exploration.

The Role of Nuclear Receptor Subfamily 1 Group H Member 4 (NR1H4) in Colon Cancer Cell Survival through the Regulation of c-Myc Stability

Nuclear receptor subfamily group H member 4 (NR1H4), also known as farnesoid X receptor, has been implicated in several cellular processes in the liver and intestine. Preclinical and clinical studies have suggested a role of NR1H4 in colon cancer development; however, how NR1H4 regulates colon cancer cell growth and survival remains unclear. We generated NR1H4 knockout (KO) colon cancer cells using clustered regularly interspaced short palindromic repeats (CRISPR)-CRISPR-associated protein-9 nuclease (CAS9) technology and explored the effects of NR1H4 KO in colon cancer cell proliferation, survival, and apoptosis. Interestingly, NR1H4 KO cells showed impaired cell proliferation, reduced colony formation, and increased apoptotic cell death compared to control colon cancer cells. We identified MYC as an important mediator of the signaling pathway alterations induced by NR1H4 KO. NR1H4 silencing in colon cancer cells resulted in reduced MYC protein levels, while NR1H4 activation using an NR1H4 ligand, chenodeoxycholic acid, resulted in time- and dose-dependent MYC induction. Moreover, NR1H4 KO enhanced the anti-cancer effects of doxorubicin and cisplatin, supporting the role of MYC in the enhanced apoptosis observed in NR1H4 KO cells. Taken together, our findings suggest that modulating NR1H4 activity in colon cancer cells might be a promising alternative approach to treat cancer using MYC-targeting agents.

Clinical relevance of increased serum preneoplastic antigen in hepatitis C-related hepatocellular carcinoma

BACKGROUND

The prognosis of hepatocellular carcinoma (HCC) patients remains poor despite advances in treatment modalities and diagnosis. It is important to identify useful markers for the early detection of HCC in patients. Preneoplastic antigen (PNA), originally reported in a rat carcinogenesis model, is increased in the tissues and serum of HCC patients.

AIM

To determine the diagnostic value of PNA for discriminating HCC and to characterize PNA-positive HCC.

METHODS

Patients with hepatitis C virus (HCV)-related hepatic disorders were prospectively enrolled in this study, which included patients with hepatitis, with cirrhosis, and with HCC. A novel enzyme-linked immunosorbent assay was developed to measure serum PNA concentrations in patients.

RESULTS

Serum PNA concentrations were measured in 89 controls and 141 patients with HCV infections (50 hepatitis, 44 cirrhosis, and 47 HCC). Compared with control and non-HCC patients, PNA was increased in HCC. On receiver operating characteristic curve analysis, the sensitivity of PNA was similar to the HCC markers des-γ-carboxy-prothrombin (DCP) and α-fetoprotein (AFP), but the specificity of PNA was lower. There was no correlation between PNA and AFP and a significant but weak correlation between PNA and DCP in HCC patients. Importantly, the correlations with biochemical markers were completely different for PNA, AFP, and DCP; glutamyl transpeptidase was highly correlated with PNA, but not with AFP or DCP, and was significantly higher in PNA-high patients than in PNA-low patients with HCV-related HCC.

CONCLUSION

PNA may have the potential to diagnose a novel type of HCC in which glutamyl transpeptidase is positively expressed but AFP or DCP is weakly or negatively expressed.

Molecular links between non-alcoholic fatty liver disease and hepatocellular carcinoma

Non-alcoholic fatty liver disease (NAFLD) and its advanced complication, non-alcoholic steatohepatitis (NASH), have become leading causes of hepatocellular carcinoma (HCC) worldwide. In this review, we discuss the role of metabolic, gut microbial, immune and endocrine mediators which promote the progression of NAFLD to HCC. In particular, this progression involves multiple hits resulting from lipotoxicity, oxidative stress, inhibition of hepatic autophagy and inflammation. Furthermore, dysbiosis in the gut associated with obesity also promotes HCC via induction of proinflammatory cytokines and Toll like receptor signalling as well as altered bile metabolism. Additionally, compromised T-cell function and impaired hepatic hormonal action promote the development of NASH-associated HCC. Lastly, we discuss the current challenges involved in the diagnosis and treatment of NAFLD/NASH-associated HCC.

In silico identification of natural products with anticancer activity using a chemo-structural database of Brazilian biodiversity

Cancer is one of the leading causes of death worldwide, and the number of patients has only increased each year, despite the considerable efforts and investments in scientific research. Since natural products (NPs) may serve as suitable sources for drug development, the cytotoxicity against cancer cells of 2221 compounds from the Nuclei of Bioassays, Ecophysiology, and Biosynthesis of Natural Products Database (NuBBE_DB) was predicted using CDRUG algorithm. Molecular modeling, chemoinformatics, and chemometric tools were then used to analyze the structural and physicochemical properties of these compounds. We compared the positive NPs with FDA-approved anticancer drugs and predicted the molecular targets involved in the anticancer activity. In the present study, 46 families comprising potential anticancer compounds and at least 19 molecular targets involved in oncogenesis. To the best of our knowledge, this is the first large-scale study conducted to evaluate the potentiality of NPs sourced from Brazilian biodiversity as anticancer agents, using in silico approaches. Our results provided interesting insights about the mechanism of action of these compounds, and also suggested that their structural diversity may aid structure-based optimization strategies for developing novel drugs for cancer therapy.

Hepatocyte peroxisome proliferator-activated receptor α regulates bile acid synthesis and transport

Peroxisome proliferator-activated receptor alpha (PPARα) controls lipid homeostasis through regulation of lipid transport and catabolism. PPARα activators are clinically used for hyperlipidemia treatment. The role of PPARα in bile acid (BA) homeostasis is beginning to emerge. Herein, Ppara-null and hepatocyte-specific Ppara-null (Ppara^∆Hep) as well as the respective wild-type mice were treated with the potent PPARα agonist Wy-14,643 (Wy) and global metabolomics performed to clarify the role of hepatocyte PPARα in the regulation of BA homeostasis. Levels of all serum BAs were markedly elevated in Wy-treated wild-type mice but not in Ppara-null and Ppara^∆Hep mice. Gene expression analysis showed that PPARα activation (1) down-regulated the expression of sodium-taurocholate acid transporting polypeptide and organic ion transporting polypeptide 1 and 4, responsible for the uptake of BAs into the liver; (2) decreased the expression of bile salt export pump transporting BA from hepatocytes into the bile canaliculus; (3) upregulated the expression of multidrug resistance-associated protein 3 and 4 transporting BA from hepatocytes into the portal vein. Moreover, there was a notable increase in the compositions of serum, hepatic and biliary cholic acid and taurocholic acid following Wy treatment, which correlated with the upregulated expression of the Cyp8b1 gene encoding sterol 12α-hydroxylase. The effects of Wy were identical between the Ppara^∆Hep and Ppara-null mice. Hepatocyte PPARα controlled BA synthesis and transport not only via direct transcriptional regulation but also via crosstalk with hepatic farnesoid X receptor signaling. These findings underscore a key role for hepatocyte PPARα in the control of BA homeostasis.

Diffuse Adenomatosis and Hepatocellular Carcinoma Treated with Liver Transplantation in an Adolescent Female with Kabuki Syndrome with a Novel KMT2D Gene Mutation

Kabuki syndrome (KS) is a rare disorder primarily associated with mutations in the KMT2D and KDM6A genes. Several tumors have been reported with KS; however, there have been no reports of hepatocellular carcinoma (HCC) or hepatic adenomatosis. We present an adolescent girl with KS and a novel KMT2D mutation who developed diffuse adenomatosis, HCC, and subsequently underwent liver transplantation.

Oxysterols and Gastrointestinal Cancers Around the Clock

This review focuses on the role of oxidized sterols in three major gastrointestinal cancers (hepatocellular carcinoma, pancreatic, and colon cancer) and how the circadian clock affects the carcinogenesis by regulating the lipid metabolism and beyond. While each field of research (cancer, oxysterols, and circadian clock) is well-studied within their specialty, little is known about the intertwining mechanisms and how these influence the disease etiology in each cancer type. Oxysterols are involved in pathology of these cancers, but final conclusions about their protective or damaging effects are elusive, since the effect depends on the type of oxysterol, concentration, and the cell type. Oxysterol concentrations, the expression of key regulators liver X receptors (LXR), farnesoid X receptor (FXR), and oxysterol-binding proteins (OSBP) family are modulated in tumors and plasma of cancer patients, exposing these proteins and selected oxysterols as new potential biomarkers and drug targets. Evidence about how cholesterol/oxysterol pathways are intertwined with circadian clock is building. Identified key contact points are different forms of retinoic acid receptor related orphan receptors (ROR) and LXRs. RORs and LXRs are both regulated by sterols/oxysterols and the circadian clock and in return also regulate the same pathways, representing a complex interplay between sterol metabolism and the clock. With this in mind, in addition to classical therapies to modulate cholesterol in gastrointestinal cancers, such as the statin therapy, the time is ripe also for therapies where time and duration of the drug application is taken as an important factor for successful therapies. The final goal is the personalized approach with chronotherapy for disease management and treatment in order to increase the positive drug effects.