Farnesoid X receptor represses matrix metalloproteinase 7 expression, revealing this regulatory axis as a promising therapeutic target in colon cancer

Delineating the role of nuclear receptors in colorectal cancer, a focused review

Colorectal cancer (CRC) stands as one of the most prevalent form of cancer globally, causing a significant number of deaths, surpassing 0.9 million in the year 2020. According to GLOBOCAN 2020, CRC ranks third in incidence and second in mortality in both males and females. Despite extensive studies over the years, there is still a need to establish novel therapeutic targets to enhance the patients' survival rate in CRC. Nuclear receptors (NRs) are ligand-activated transcription factors (TFs) that regulate numerous essential biological processes such as differentiation, development, physiology, reproduction, and cellular metabolism. Dysregulation and anomalous expression of different NRs has led to multiple alterations, such as impaired signaling cascades, mutations, and epigenetic changes, leading to various diseases, including cancer. It has been observed that differential expression of various NRs might lead to the initiation and progression of CRC, and are correlated with poor survival outcomes in CRC patients. Despite numerous studies on the mechanism and role of NRs in this cancer, it remains of significant scientific interest primarily due to the diverse functions that various NRs exhibit in regulating key hallmarks of this cancer. Thus, modulating the expression of NRs with their agonists and antagonists, based on their expression levels, holds an immense prospect in the diagnosis, prognosis, and therapeutical modalities of CRC. In this review, we primarily focus on the role and mechanism of NRs in the pathogenesis of CRC and emphasized the significance of targeting these NRs using a variety of agents, which may represent a novel and effective strategy for the prevention and treatment of this cancer.

Farnesoid X receptor promotes non-small cell lung cancer metastasis by activating Jak2/STAT3 signaling via transactivation of IL-6ST and IL-6 genes

Metastasis accounts for the majority of cases of cancer recurrence and death in patients with advanced non-small cell lung cancer (NSCLC). Farnesoid X Receptor (FXR) is a bile acid nuclear receptor that was recently found to be upregulated in NSCLC tissues. However, whether and how FXR regulates NSCLC metastasis remains unclear. In the present study, it was found that FXR promoted the migration, invasion, and angiogenic ability of NSCLC cells in vitro, and increased NSCLC metastasis in a mouse model in vivo. Mechanistic investigation demonstrated that FXR specifically bound to the promoters of IL-6ST and IL-6 genes to upregulate their transcription, thereby leading to activation of the Jak2/STAT3 signaling pathway, which facilitated tumor migration, invasion, and angiogenesis in NSCLC. Notably, Z-guggulsterone, a natural FXR inhibitor, significantly reduced FXRhigh NSCLC metastasis, and decreased the expression of FXR, IL-6, IL-6ST, and p-STAT3 in the mouse model. Clinical analysis verified that FXR was positively correlated with IL-6, IL-6ST and p-STAT3 expression in NSCLC patients, and was indicative of a poor prognosis. Collectively, these results highlight a novel FXR-induced IL-6/IL-6ST/Jak2/STAT3 axis in NSCLC metastasis, and a promising therapeutic means for treating FXRhigh metastatic NSCLC.

Targeting Farnesoid X Receptor in Tumor and the Tumor Microenvironment: Implication for Therapy

The farnesoid-X receptor (FXR), a member of the nuclear hormone receptor superfamily, can be activated by bile acids (BAs). BAs binding to FXR activates BA signaling which is important for maintaining BA homeostasis. FXR is differentially expressed in human organs and exists in immune cells. The dysregulation of FXR is associated with a wide range of diseases including metabolic disorders, inflammatory diseases, immune disorders, and malignant neoplasm. Recent studies have demonstrated that FXR influences tumor cell progression and development through regulating oncogenic and tumor-suppressive pathways, and, moreover, it affects the tumor microenvironment (TME) by modulating TME components. These characteristics provide a new perspective on the FXR-targeted therapeutic strategy in cancer. In this review, we have summarized the recent research data on the functions of FXR in solid tumors and its influence on the TME, and discussed the mechanisms underlying the distinct function of FXR in various types of tumors. Additionally, the impacts on the TME by other BA receptors such as takeda G protein-coupled receptor 5 (TGR5), sphingosine-1-phosphate receptor 2 (S1PR2), and muscarinic receptors (CHRM2 and CHRM3), have been depicted. Finally, the effects of FXR agonists/antagonists in a combination therapy with PD1/PD-L1 immune checkpoint inhibitors and other anti-cancer drugs have been addressed.

Pathogenic role of 25-hydroxycholesterol in cancer development and progression

Cholesterol is an essential lipid that serves several important functions, including maintaining the homeostasis of cells, acting as a precursor to bile acid and steroid hormones and preserving the stability of membrane lipid rafts. 25-hydroxycholesterol (25-HC) is a cholesterol derivative that may be formed from cholesterol. 25-HC is a crucial component in various biological activities, including cholesterol metabolism. In recent years, growing evidence has shown that 25-HC performs a critical function in the etiology of cancer, infectious diseases and autoimmune disorders. This review will summarize the latest findings regarding 25-HC, including its biogenesis, immunomodulatory properties and role in innate/adaptive immunity, inflammation and the development of various types of cancer.

CXCL1 promotes colon cancer progression through activation of NF-κB/P300 signaling pathway

BACKGROUND

The upregulated expression of CXCL1 has been validated in colorectal cancer patients. As a potential biotherapeutic target for colorectal cancer, the mechanism by which CXCL1 affects the development of colorectal cancer is not clear.

METHODS

Expression data of CXCL1 in colorectal cancer were obtained from the GEO database and verified using the GEPIA database and the TIMER 2.0 database. Knockout and overexpression of CXCL1 in colorectal cancer cells by CRISPR/Cas and "Sleeping Beauty" transposon-mediated gene editing techniques. Cell biological function was demonstrated by CCK-8, transwell chamber and Colony formation assay. RT-qPCR and Western Blot assays measured RNA and protein expression. Protein localization and expression were measured by immunohistochemistry and immunofluorescence.

RESULTS

Bioinformatics analysis showed significant overexpression of CXCL1 in the colorectal cancer tissues compared to normal human tissues, and identified CXCL1 as a potential therapeutic target for colorectal cancer. We demonstrate that CXCL1 promotes the proliferation and migration of colon cancer cells and has a facilitative effect on tumor angiogenesis. Furthermore, CXCL1 elevation promoted the migration of M2-tumor associated macrophages (TAMs) while disrupting the aggregation of CD4+ and CD8+ T cells at tumor sites. Mechanistic studies suggested that CXCL1 activates the NF-κB pathway. In the in vivo colon cancer transplantation tumor model, treatment with the P300 inhibitor C646 significantly inhibited the growth of CXCL1-overexpressing colon cancer.

CONCLUSION

CXCL1 promotes colon cancer development through activation of NF-κB/P300, and that CXCL1-based therapy is a potential novel strategy to prevent colon cancer development.

Dysbiosis: The first hit for digestive system cancer

Gastrointestinal cancer may be associated with dysbiosis, which is characterized by an alteration of the gut microbiota. Understanding the role of gut microbiota in the development of gastrointestinal cancer is useful for cancer prevention and gut microbiota-based therapy. However, the potential role of dysbiosis in the onset of tumorigenesis is not fully understood. While accumulating evidence has demonstrated the presence of dysbiosis in the intestinal microbiota of both healthy individuals and patients with various digestive system diseases, severe dysbiosis is often present in patients with digestive system cancer. Importantly, specific bacteria have been isolated from the fecal samples of these patients. Thus, the association between dysbiosis and the development of digestive system cancer cannot be ignored. A new model describing this relationship must be established. In this review, we postulate that dysbiosis serves as the first hit for the development of digestive system cancer. Dysbiosis-induced alterations, including inflammation, aberrant immune response, bacteria-produced genotoxins, and cellular stress response associated with genetic, epigenetic, and/or neoplastic changes, are second hits that speed carcinogenesis. This review explains the mechanisms for these four pathways and discusses gut microbiota-based therapies. The content included in this review will shed light on gut microbiota-based strategies for cancer prevention and therapy.

Bile Acids: Physiological Activity and Perspectives of Using in Clinical and Laboratory Diagnostics

Bile acids play a significant role in the digestion of nutrients. In addition, bile acids perform a signaling function through their blood-circulating fraction. They regulate the activity of nuclear and membrane receptors, located in many tissues. The gut microbiota is an important factor influencing the effects of bile acids via enzymatic modification. Depending on the rate of healthy and pathogenic microbiota, a number of bile acids may support lipid and glucose homeostasis as well as shift to more toxic compounds participating in many pathological conditions. Thus, bile acids can be possible biomarkers of human pathology. However, the chemical structure of bile acids is similar and their analysis requires sensitive and specific methods of analysis. In this review, we provide information on the chemical structure and the biosynthesis of bile acids, their regulation, and their physiological role. In addition, the review describes the involvement of bile acids in various diseases of the digestive system, the approaches and challenges in the analysis of bile acids, and the prospects of their use in omics technologies.

New Insights into Bile Acids Related Signaling Pathways in the Onset of Colorectal Cancer

Colorectal cancer (CRC) ranks as the second among the causes of tumor death worldwide, with an estimation of 1.9 million new cases in 2020 and more than 900,000 deaths. This rate might increase by 60% over the next 10 years. These data are unacceptable considering that CRC could be successfully treated if diagnosed in the early stages. A high-fat diet promotes the hepatic synthesis of bile acids (BAs) increasing their delivery to the colonic lumen and numerous scientific reports correlate BAs, especially secondary BAs, with CRC incidence. We reviewed the physicochemical and biological characteristics of BAs, focusing on the major pathways involved in CRC risk and progression. We specifically pointed out the role of BAs as signaling molecules and the tangled relationships among their nuclear and membrane receptors with the big bang of molecular and cellular events that trigger CRC occurrence.

Type IV Collagen in Human Colorectal Liver Metastases—Cellular Origin and a Circulating Biomarker

Simple Summary

Patients with colorectal liver metastases (CLM) can be cured through surgery if metastases are detected early in disease progression. Today, CLM diagnosis relies heavily on diagnostic imaging, and cheap, non-invasive, and efficiently measurable biomarkers are needed. Circulating type IV collagen (COL IV) is a potential biomarker for detecting CLM. Patients with CLM show elevated circulating levels of COL IV and increased tissue expression of COL IV in CLM tissue, which could result from enhanced production and degradation of COL IV. This study aimed to establish the cellular source behind enhanced COL IV levels, which is helpful in the evaluation of the biomarker potential of COL IV. We show that fibroblasts express COL IV both in vitro and in the stromal tissue of CLM. We also found that CLM tissue expresses COL IV-degrading proteases. Lastly, CLM patients have higher circulating COL IV levels than healthy controls.

Abstract

Circulating type IV collagen (cCOL IV) is a potential biomarker for patients with colorectal liver metastases (CLM) who present with elevated levels of COL IV in both CLM tissue and circulation. This study aimed to establish the cellular origin of elevated levels of COL IV and analyze circulating COL IV in CLM patients. The cellular source was established through in situ hybridization, immunohistochemical staining, and morphological evaluation. Cellular expression in vitro was assessed by immunofluorescence. Tissue expression of COL IV-degrading matrix metalloproteinases (MMPs)-2, -7, -9, and -13 was studied with immunohistochemical staining. Plasma levels of COL IV in CLM patients and healthy controls were analyzed with ELISA. This study shows that cancer-associated fibroblasts (CAFs) express COL IV in the stroma of CLM and that COL IV is expressed in vitro by fibroblasts but not by tumor cells. MMP-2, -7, -9, and -13 are expressed in CLM tissue, mainly by hepatocytes and immune cells, and circulating COL IV is significantly elevated in CLM patients compared with healthy controls. Our study shows that stromal cells, not tumor cells, produce COL IV in CLM, and that circulating COL IV is elevated in patients with CLM.

Synergistic effect of obeticholic acid and fasting-mimicking on proliferative, migration, and survival signaling in prostate cancer

The systemic and resistant nature of the androgen-independent stage of prostate cancers makes it largely incurable even after intensive multimodal therapy. Apoptosis and epithelial-mesenchymal transition (EMT) are two fundamental events that are deeply linked to carcinogenesis. Hence, it is necessary to find a new combination of several therapies targeting apoptosis and EMT without causing side effects. Several recent studies have indicated that the Farnesoid X receptor is extensively associated with human tumorigenesis. The FXR agonist obeticholic acid (INT 747) has preliminarily exhibited a tumor suppressor potential. In this present study, we assess the potential synergism of FXR activation under nutrient deprivation in prostate cancer cell lines to investigate whether FXR activation enhances starvation-induced apoptosis in PC3 cells. In this study, PC-3 treatment with INT 747 significantly repressed cell proliferation and clonogenic potential. In addition, it significantly induced apoptosis of PC-3 cells and decreased their cancerogenic potential, as evaluated by annexin v apoptosis and transwell migration assay, respectively. The decreased expression of pro-caspase 3 by western blot analysis further confirmed INT 747-induced apoptosis. Furthermore, the fasting-mimicking diet (FMD) potentiated the antiproliferative, pro-apoptotic, and antimetastatic effects of INT 747. Mechanistically, these effects were mediated through the downregulation of cyclin D1 and upregulation of PTEN. In conclusion, INT 747 alone markedly decreases, and when combined with FMD abrogates the growth and migration of PC-3 cells.

Dihydroartemisinin promoted FXR expression independent of YAP1 in hepatocellular carcinoma

Loss of FXR, one of bile acid receptors, enlarged livers. Yes-associated protein 1 (YAP1), a dominant oncogene, promotes hepatocellular carcinoma (HCC). However, the relationship between FXR and YAP1 was unspecified in bile acid homeostasis in HCC. Here, we used TIMER2.0, the Cancer Genome Atlas (TCGA) Database, and Kaplan-Meier Plotter Database and discovered that FXR was positively correlated with better prognosis in liver cancer patients. Our previous research showed that dihydroartemisinin (DHA) inhibited cell proliferation in HepG2 and HepG22215 cells. However, the relationship of YAP1 and the bile acid receptor FXR remains elusive during DHA treatment. Furthermore, we showed that DHA improved FXR and reduced YAP1 in the liver cancer cells and mice. Additionally, the expression of nucleus protein FXR was enhanced in Yap1^LKO mice with liver cancer. DHA promoted the expression level of whole and nuclear protein FXR independent of YAP1 in Yap1^LKO mice with liver cancer. DHA declined cholesterol 7α-hydroxylase, but not sterol 27-hydroxylase, and depressed cholic acid and chenodeoxycholic acid of liver tissue in Yap1^LKO mice with liver cancer. Generally, our results suggested that DHA improved FXR and declined YAP1 to suppress bile acid metabolism. Thus, we suggested that FXR acted as a potential therapeutic target in HCC.

Cholecystectomy promotes colon carcinogenesis by activating the Wnt signaling pathway by increasing the deoxycholic acid level

Purpose

Cholecystectomy (XGB) is widely recognized as a risk factor for colon cancer (CC). Continuous exposure of the colonic epithelium to deoxycholic acid (DCA) post-XGB may exert cytotoxic effects and be involved in the progression of CC. However, the functions of the XGB-induced DCA increase and the underlying mechanism remain unclear.

Methods

Colitis-associated CC (CAC) mouse models constructed by AOM-DSS inducement were used to confirm the effect of XGB on the CC progression. Hematoxylin & eosin staining was performed to assess the tumor morphology of CAC mouse models tissues. Various cell biological assays including EdU, live-cell imaging, wound-healing assays, and flow cytometry for cell cycle and apoptosis were used to evaluate the effect of DCA on CC progression. The correlation among XGB, DCA, and CC and their underlying mechanisms were detected with immunohistochemistry, mass spectrometry, transcriptome sequencing, qRT-PCR, and western blotting.

Results

Here we proved that XGB increased the plasma DCA level and promoted colon carcinogenesis in a colitis-associated CC mouse model. Additionally, we revealed that DCA promoted the proliferation and migration of CC cells. Further RNA sequencing showed that 120 mRNAs were upregulated, and 118 downregulated in DCA-treated CC cells versus control cells. The upregulated mRNAs were positively correlated with Wnt signaling and cell cycle-associated pathways. Moreover, DCA treatment could reduced the expression of the farnesoid X receptor (FXR) and subsequently increased the levels of β-Catenin and c-Myc in vitro and in vivo. Moreover, the FXR agonist GW4064 decreased the proliferation of CC cells by repressing the expression of β-catenin.

Conclusion

We concluded that XGB-induced DCA exposure could promote the progression of CC by inhibiting FXR expression and enhancing the Wnt-β-catenin pathway.

Enhancement of Farnesoid X Receptor Inhibits Migration, Adhesion and Angiogenesis through Proteasome Degradation and VEGF Reduction in Bladder Cancers

(1) Background: Bladder cancer is a malignant tumor mainly caused by exposure to environmental chemicals, with a high recurrence rate. NR1H4, also known as Farnesoid X Receptor (FXR), acts as a nuclear receptor that can be activated by binding with bile acids, and FXR is highly correlated with the progression of cancers. The aim of this study was to verify the role of FXR in bladder cancer cells. (2) Methods: A FXR overexpressed system was established to investigate the effect of cell viability, migration, adhesion, and angiogenesis in low-grade TSGH8301 and high-grade T24 cells. (3) Results: After FXR overexpression, the ability of migration, adhesion, invasion and angiogenesis of bladder cancer cells declined significantly. Focal adhesive complex, MMP2, MMP9, and angiogenic-related proteins were decreased, while FXR was overexpressed in bladder cancer cells. Moreover, FXR overexpression reduced vascular endothelial growth factor mRNA and protein expression and secretion in bladder cancer cells. After treatment with the proteosome inhibitor MG132, the migration, adhesion and angiogenesis caused by FXR overexpression were all reversed in bladder cancer cells. (4) Conclusions: These results may provide evidence on the role of FXR in bladder cancer, and thus may improve the therapeutic efficacy of urothelial carcinoma in the future.

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.

Zinc finger protein 277 is an intestinal transit-amplifying cell marker and colon cancer oncogene

Sustained proliferative signaling and resisting cell death are hallmarks of cancer. Zinc finger protein 277 (ZNF277; murine Zfp277), a transcription factor regulating cellular senescence, is overexpressed in colon cancer, but its actions in intestinal homeostasis and neoplasia are unclear. Using human and murine intestine, human colon cancer cells, and Apc^Min/+ mice with dysregulated β-catenin signaling and exuberant intestinal neoplasia, we explored the actions of ZNF277/Zfp277 and defined the underlying mechanisms. In normal human and murine intestine, ZNF277/Zfp277 was expressed uniquely in early stem cell progenitors, undifferentiated transit-amplifying cells (TACs). Zfp277 was overexpressed in the Apc^Min/+ mouse colon, implicating ZNF277/Zfp277 as a transcriptional target of β-catenin signaling. We confirmed this by showing β-catenin knockdown reduced ZNF277 expression and, using chromatin IP, identified 2 β-catenin binding sites in the ZNF277 promoter. Zfp277 deficiency attenuated intestinal epithelial cell proliferation and tumor formation, and it strikingly prolonged Apc^Min/+ mouse survival. RNA-Seq and PCR analyses revealed that Zfp277 modulates expression of genes in key cancer pathways, including β-catenin signaling, the HOXD family that regulates development, and p21^WAF1, a cell cycle inhibitor and tumor suppressor. In both human colon cancer cells and the murine colon, ZNF277/Zfp277 deficiency induced p21^WAF1 expression and promoted senescence. Our findings identify ZNF277/Zfp277 as both a TAC marker and colon cancer oncogene that regulates cellular proliferation and senescence, in part by repressing p21^WAF1 expression.

Dietary fat, bile acid metabolism and colorectal cancer

Colorectal cancer (CRC) risk is predominantly driven by environmental factors, in particular diet. A high intake of dietary fat has been implicated as a risk factor inducing the formation of pre-neoplastic lesions (e.g., adenomatous polyps) and/or exacerbating colonic tumorigenesis. Recent data attributed the tumor-promoting activity of high-fat diets to their effects on gut microbiota composition and metabolism, in particular with regard to bile acids. Bile acids are synthesized in the liver in response to dietary fat and facilitate lipid absorption in the small intestine. The majority of bile acids is re-absorbed during small intestinal transit and subjected to enterohepatic circulation. Bile acids entering the colon undergo complex biotransformation performed by gut bacteria, resulting in secondary bile acids that show tumor-promoting activity. Excessive dietary fat leads to high levels of secondary bile acids in feces and primes the gut microbiota to bile acid metabolism. This promotes an altered overall bile acid pool, which activates or restricts intestinal and hepatic cross-signaling of the bile acid receptor, farnesoid X receptor (FXR). Recent studies provided evidence that FXR is a main regulator of bile acid-mediated effects on intestinal tumorigenesis integrating dietary, microbial and genetic risk factors for CRC. Selective FXR agonist or antagonist activity by specific bile acids depends on additional factors (e.g., bile acid concentration, composition of bile acid pool, genetic instability of cells) and, thus, may differ in healthy and tumorigenic conditions in the intestine. In conclusion, fat-mediated alterations of the gut microbiota link bile acid metabolism to CRC risk and colonic tumorigenesis, exemplifying how gut microbial co-metabolism affects colon health.

Activation of FXR Suppresses Esophageal Squamous Cell Carcinoma Through Antagonizing ERK1/2 Signaling Pathway

Introduction

Farnesoid X receptor (FXR), a member of nuclear receptors, functionally regulates bile acid, glucose and lipid homeostasis. It is also worth noting that FXR plays a suppressor role in cancer and inflammation. However, the contribution of FXR to esophageal squamous cell carcinoma (ESCC) remains unknown.

Methods

The role of FXR activation in ESCC progression was evaluated in ESCC cell lines KYSE150 and EC109 in vitro and BALB-C nude mice in vivo. In vitro, FXR synthetic ligand GW4064 was used to detect the effects on ESCC cell proliferation, migration, apoptosis and cell cycles. To assess the effects of GW4064 on ESCC development in vivo, a xenograft tumor model was constructed. And ERK1/2 activity was evaluated by immunoblot analysis.

Results

FXR synthetic ligand GW4064 impaired esophageal squamous cell carcinoma (ESCC) proliferation and migration, induced apoptosis and cell cycle arrest in vitro, accompanied by inhibition of some inflammatory genes and promotion of pro-apoptotic genes. We then found that FXR activation decreased the phosphorylation levels of ERK1/2 induced by tumor necrosis factor-α (TNF-α) in ESCC cells. Consistent with these results, GW4064 suppressed ESCC tumorigenesis in a xenograft model and suppressed the phosphorylation of ERK1/2 in tumors.

Discussion

These findings identify that activating FXR may serve as a promising therapy or adjuvant therapeutic tool for controlling ESCC development.

Targeting Farnesoid X receptor (FXR) for developing novel therapeutics against cancer

Cancer is one of the lethal diseases that arise due to the molecular alterations in the cell. One of those alterations associated with cancer corresponds to differential expression of Farnesoid X receptor (FXR), a nuclear receptor regulating bile, cholesterol homeostasis, lipid, and glucose metabolism. FXR is known to regulate several diseases, including cancer and cardiovascular diseases, the two highly reported causes of mortality globally. Recent studies have shown the association of FXR overexpression with cancer development and progression in different types of cancers of breast, lung, pancreas, and oesophagus. It has also been associated with tissue-specific and cell-specific roles in various cancers. It has been shown to modulate several cell-signalling pathways such as EGFR/ERK, NF-κB, p38/MAPK, PI3K/AKT, Wnt/β-catenin, and JAK/STAT along with their targets such as caspases, MMPs, cyclins; tumour suppressor proteins like p53, C/EBPβ, and p-Rb; various cytokines; EMT markers; and many more. Therefore, FXR has high potential as novel biomarkers for the diagnosis, prognosis, and therapy of cancer. Thus, the present review focuses on the diverse role of FXR in different cancers and its agonists and antagonists.

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.

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.

MMP7 as a potential biomarker of colon cancer and its prognostic value by bioinformatics analysis

ABSTRACT

Colon cancer is one of the most common cancers in the world. To identify the candidate genes in the carcinogenesis and progression of colon cancer, the microarray datasets GSE10950, GSE44861 and GSE74602 were downloaded from the Gene Expression Omnibus (GEO) database. The differentially expressed genes (DEGs) were identified, and functional enrichment analyses were performed. A total of 176 DEGs were identified, consisting of 55 genes upregulated and 121 genes downregulated in colon cancer tissues compared to non-cancerous tissues. The DEGs were mainly enriched in mineral absorption, nitrogen metabolism and complement and coagulation cascades. By using STRING database analysis, we constructed a coexpression network composed of 140 nodes and 280 edges for the DEGs with a combined score >0.4 and a significant interaction relation. Thirteen hub genes were identified, and poor OS of patients was only associated with high expression of Matrix Metallopeptidase 7 (MMP7), which may be involved in the carcinogenesis, invasion or recurrence of colon cancer. In conclusion, we propose that the DEGs and hub genes identified in the present study may be regarded as diagnostic biomarkers for colon cancer. Moreover, the overexpression of MMP7 may correlate with poor prognosis.

Intestine-specific FXR agonists as potential therapeutic agents for colorectal cancer

Colorectal cancer (CRC) is one of the most malignant cancers in the world. A major cause of death in CRC patients is the limited therapeutic options in its advanced stages. The Farnesoid X receptor (FXR) is a member of the nuclear superfamily, which is effective in slowing the progression of colorectal cancer in addition to its extraordinary role in regulating metabolic disorders. Due to the systemic side-effects caused by non-selective agonists, the intestine-restricted FXR agonists can induce a whole-body benefit without activating the hepatic FXR, suggesting intestinal FXR activation as a potentially safer therapy in the treatment of CRC. This review highlights the effects of FXR on the disturbed bile acid circulation and the carcinogenesis of CRC and with a specific emphasis on listing the functions of several intestinal-restricted FXR agonists.

Serum matrix metalloproteinase 7 (MMP7) is a biomarker of fibrosis in patients with non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) affects 25% of the adult population globally. Since liver fibrosis is the most important predictor of liver-related complications in patients with NAFLD, identification of patients with advanced fibrosis among at-risk individuals is an important issue in clinical practice. Transient elastography is the best evaluated non-invasive method used in referral centres to assess liver fibrosis, however serum-based tests, such as the Enhanced Liver Fibrosis (ELF) score, have a practical advantage as first-line tests due to their wider availability and lower cost. We previously identified matrix metalloproteinase 7 (MMP7) as a serum biomarker of histological advanced fibrosis in a mixed-etiology patient cohort. In this study we aimed to determine the association between MMP7 and fibrosis, assessed by transient elastography, in patients with NAFLD. Serum MMP7 levels were measured in a cohort of 228 patients with NAFLD. Associations between MMP7, liver stiffness measurement (LSM), ELF score and clinical parameters were determined using logistic regression modelling. Serum MMP7 was associated with clinically significant fibrosis (LSM ≥ 8.2), independent of age, gender, BMI and diabetes. The addition of MMP7 significantly improved the diagnostic performance of the ELF test, particularly in patients over the age of 60. Combinations of serum biomarkers have the potential to improve the sensitivity and specificity of detection of advanced fibrosis in at-risk patients with NAFLD. We have demonstrated that serum MMP7 is independently associated with clinically significant fibrosis and improves the diagnostic performance of currently available tests in older patients.

Farnesoid X receptor: a potential therapeutic target in multiple organs

Farnesoid X receptor (FXR), a member of the nuclear receptor family, is a common receptor found in the intestine and liver, and helps to maintain systemic metabolic homeostasis through regulating bile acid, glucose, lipid metabolism, and energy homeostatsis. In addition, FXR regulates the functions of various organs, such as liver, intestine, kidney, breast, pancreas, cardiovascular system and brain. FXR also plays a key role in regulation of gut-microbiota through mediating the various signaling pathways. Accordingly, FXR has become an attractive therapeutic target in a variety of diseases. This review combines classical and recent research reports to introduce the basic information about FXR and its important roles in various organs of the body.

Farnesoid X receptor activation induces antitumour activity in colorectal cancer by suppressing JAK2/STAT3 signalling via transactivation of SOCS3 gene

Farnesoid X receptor (FXR, encoded by NR1H4), a bile acid‐activated nuclear receptor, is widely implicated in human tumorigenesis. The FXR agonist obeticholic acid (OCA) has preliminarily displayed tumour suppressor potential. However, the anticancer effects of this agent on colorectal cancer (CRC) remain unclear. In this study, the treatment of colon cancer cells with OCA inhibited cell proliferation and invasion in vitro, retarded tumour growth in vivo and prevented the G₀/G₁ to S phase transition. Moreover, the expression of active caspase‐3, p21 and E‐cadherin was up‐regulated and the expression of cyclin D1, c‐Myc, vimentin, N‐cadherin and MMP9 was down‐regulated in OCA‐treated colon cancer cells. Mechanistic studies indicated that OCA treatment suppressed the activity of JAK2/STAT3 pathway by up‐regulating SOCS3 expression. Colivelin, an agonist of JAK2/STAT3 pathway, antagonized the tumour‐suppressive effect of OCA on colon cancer cells. Dual‐luciferase reporter and quantitative chromatin immunoprecipitation (qChIP) assays further confirmed that OCA promoted SOCS3 transcription by enhancing the binding of FXR to the FXRE/IR9 of the SOCS3 promoter. In conclusion, our study demonstrates that targeting FXR and improving its function might be a promising strategy for CRC treatment.

Farnesoid X receptor antagonizes Wnt/β-catenin signaling in colorectal tumorigenesis

Farnesoid X receptor (FXR, encoded by NR1H4), a critical regulator of bile acid homeostasis, is widely implicated in human tumorigenesis. However, the functional role of FXR in colorectal cancer (CRC) and the precise molecular mechanism remain unclear. In this study, we demonstrated that FXR expression was downregulated in colon cancer tissues and decreased expression of FXR predicted a poor prognosis. Knockdown of FXR promoted colon cancer cell growth and invasion in vitro, and facilitated xenograft tumor formation and distant metastasis in vivo, whereas ectopic expression of FXR had the reserved change. Mechanistic studies indicated that FXR exerted its tumor suppressor functions by antagonizing Wnt/β-catenin signaling. Furthermore, we identified an FXR/β-catenin interaction in colon cancer cells. The FXR/β-catenin interaction impaired β-catenin/TCF4 complex formation. In addition, our study suggested a reciprocal relationship between FXR and β-catenin, since loss of β-catenin increased the transcriptional activation of SHP by FXR. Altogether, these data indicated that FXR functions a tumor-suppressor role in CRC by antagonizing Wnt/β-catenin signaling.

Breast Heterogeneity: Obstacles to Developing Universal Biomarkers of Breast Cancer Initiation and Progression

BACKGROUND

Predicting outcomes and response to therapy through biomarkers is a major challenge in cancer research. In previous studies, we suggested that inappropriate "normal" tissue samples used for comparison with tumors, inter-individual heterogeneity in gene expression, and genetic ancestry all influence biomarker expression in tumors. The aim of this study was to investigate these factors in breast cancer using breast tissues from healthy women and normal tissue adjacent to tumor (NAT) with matrix metalloproteinase 7 (MMP7) as a candidate biomarker.

STUDY DESIGN

RNA sequencing was performed on primary luminal progenitor cells from healthy breast, NATs, and tumors to identify transcriptomes enriched in NATs and breast cancer. Expression of select genes was validated via quantitative reverse transcription polymerase chain reaction of RNA and via immunohistochemistry of a tissue microarray of normal, NAT, and tumor samples of different genetic ancestry.

RESULTS

Twenty-six genes were significantly overexpressed in NATs and tumors compared with healthy controls at messenger RNA level and formed a para-inflammatory network. MMP7 had the greatest expression in tumor cells, with upregulation confirmed by quantitative reverse transcription polymerase chain reaction. Tumor-enriched but not NAT-enriched expression of MMP7 compared with healthy controls was reproduced at protein levels. When stratified by genetic ancestry, tumor-specific increase of MMP7 reached statistical significance in women of European ancestry.

CONCLUSIONS

Transcriptome differences across healthy, NAT, and tumor tissue in breast cancer demonstrate an active para-inflammatory network in NATs and indicate unsuitability of NATs as "normal controls" in biomarker discovery. The discordance between transcriptomic and proteomic MMP7 expression in NATs and the influence of genetic ancestry on its protein expression highlight the complexity in developing universally acceptable biomarkers of breast cancer and the importance of genetic ancestry in biomarker development.

Computational Insight into the Allosteric Activation Mechanism of Farnesoid X Receptor

The farnesoid X receptor (FXR) is a bile acid-sensing transcription factor with indispensable roles in regulating metabolic processes. Nowadays, FXR has become a highly promising drug target for severe liver disorders, especially nonalcoholic steatohepatitis (NASH). A recent study showed that imatinib and its analogues were able to allosterically enhance agonist-induced FXR activation and its target gene expression. However, the allosteric modulation mechanism of FXR by these compounds remains unclear. In this work, the most effective imatinib analogue, P16, was used as a probe to explore this issue by computational approaches. Our results identified one potential allosteric site surrounded by residues Ile335, Phe336, Lys338, Glu339, Leu340, and Leu348, which could efficiently accommodate P16. In addition, the long-time molecular dynamics simulations indicated that the binding of P16 could significantly decrease the fluctuation of the co-activator and enhance the communications between the endogenous ligand chenodeoxycholic acid (CDCA) and FXR. By analyzing the residue interaction network, we observed two unique communication pathways connecting P16 and CDCA through three key residues, Arg331, Ser332, and Phe336. The communications of network organization in the P16-bound complex may allow the synergistic effect of the two compounds via robust signal transmission between the binding sites and global network bridges, which coordinate allosteric transitions and modulate the receptor activity. Our study offers insights into the allosteric modulation occurring in FXR and would be helpful for discovery of new allosteric modulators targeting FXR for further clinical research.

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.