| Gastric cancer is a type of cancer with high incidence and mortality rates worldwide.In China,gastric cancer is the fourth most common type of cancer in terms of incidence and mortality,with about 400,000 new cases and 300,000 deaths each year.Gastric cancer has seriously affected the lives and health of Chinese people.Gastric cancer has no obvious symptoms in its early stage,making it difficult to diagnose at an early stage.Often,when gastric cancer is diagnosed,it has already reached the progressive stage,which is difficult to treat,and the prognosis is extremely poor,with an overall five-year survival rate of less than 50%.The molecular mechanism of gastric cancer development is extremely complicated,and different types of gastric cancer have different pathogenesis,which is also an important reason why it is difficult to diagnose and treat gastric cancer.Therefore,it is essential to investigate the pathogenesis of gastric cancer and to find molecular targets and targeted drugs for the treatment of gastric cancer.The farnesol X receptor(FXR),a nuclear receptor identified in1995,plays an important regulatory role in the body as a bile acid receptor.FXR is a central regulator of bile acid metabolism,maintaining bile acid homeostasis by regulating bile acid synthesis and hepatoenteral circulation.FXR is also deeply involved in the regulation of glucose metabolism,lipid metabolism,and energy homeostasis.In addition,FXR regulates the progression of various diseases such as hepatitis and hepatocellular carcinoma,and agonists of FXR have been used clinically to treat primary bile duct cancer and liver fibrosis.Long non-coding RNAs(Lnc RNAs),defined as non-protein-coding RNAs longer than 200 nucleotides,are widely distributed in the human genome.Lnc RNAs are deeply involved in the continuous proliferation,replication immortality,survival and metastasis,metabolism,and shaping of the tumor microenvironment of cancer cells.They have become key regulators of cancer and have the potential to be therapeutic targets and cancer markers.This study explores the role and specific molecular mechanism of FXR in gastric cancer and tries to find a pathway for FXR to antagonize gastric cancer through Lnc RNAs.The specific content and conclusions of the paper are as follows:In this study,the differences of gastric tissues between wild-type mice(WT)and FXR gene-deficient(FXR KO)mice were first compared.In young mice,FXR deficiency resulted in the upregulation of numerous inflammatory genes in the stomach,and FXR KO aged mice are more prone to gastritis and gastric cancer.Moreover,FXR KO mice were more sensitive to LPS-induced gastritis.The results of animal experiments demonstrated the potential antagonistic effect of FXR on gastritis and gastric cancer.Then this study explored the function of FXR using gastric cancer cell lines AGS and MGC803.Activation of FXR significantly inhibited the proliferation and migration of gastric cancer cell lines,blocked the cycle of gastric cancer cells,and promoted the apoptosis of gastric cancer cells.Activation of FXR also inhibited tumor formation in vivo in tumor-bearing mice,revealing the function of FXR as a negative regulator of gastric cancer.Further studies have found that activating FXR can regulate the expression of various inflammatory cancer-related genes in AGS cells,thereby playing an antagonistic role in gastric cancer.Furthermore,we investigate whether FXR would antagonize gastric cancer by regulating the expression of non-coding RNAs.Highthroughput sequencing of Lnc RNAs was performed on AGS cells after activating FXR.LINC01876 was found because of the differential expression in the two groups.Activation of FXR by GW4064 inhibits the binding of ELAV-like RNA-binding protein 1(ELAVL1)to LINC01876 by activating adenylate-activated protein kinase(AMPK)and promotes the degradation of LINC01876.LINC01876 is highly expressed in gastric cancer and may play a role in promoting gastric cancer.In this study,we investigated the effects of LINC01876 on the malignant phenotype of gastric cancer cell lines,including proliferation and migration,by overexpressing and knocking down LINC01876 in gastric cancer cell lines.The results showed that LINC01876 promoted the proliferation and migration of gastric cancer cells and inhibited the apoptosis of gastric cancer cells.The localization of LINC01876 in gastric cancer cells revealed that LINC01876 was distributed in both the cytoplasm and nucleus of gastric cancer cells.The previous studies showed that Lnc RNAs in the cytoplasm often play regulatory roles as competing endogenous RNAs(ce RNA)for mi RNAs.Database prediction results showed that mi R-145-5p might bind to LINC01876,and mutual binding was demonstrated by luciferase reporter gene assay and AGO2 RIP assay.Mi RNAs tend to function by regulating the expression of target genes.This study further determined the target gene FSCN1 of mi R-145-5p through bioinformatics analysis and luciferase experiments.The results of numerous compensatory experimental results showed that LINC01876 promotes FSCN1 expression through the competitive binding of mi R-145-5p,which in turn promotes gastric cancer progression.After that,the role of LINC01876 in the nucleus was explored in this project.We identified the protein,ribosomal protein L11(RPL11),that binds to LINC01876 in the nucleus using RNA pulldown assay and mass spectrometry.We then determined that RPL11 binds to LINC01876 mutually by RIP assay.Previous studies have shown that in the nucleoplasm of cells,RPL11 inhibits the ubiquitination of p53 by binding to MDM2,thus allowing p53 to be retained and exerting an oncogenic effect.Using immunofluorescence staining and cell fractionation experiments,we confirmed that LINC01876 would retain RPL11 in the nucleolus by binding to RPL11,then reduce the formation of RPL11-MDM2-p53 complex,promote the ubiquitination of p53 by MDM2,and accelerate the degradation of p53,thus promoting gastric cancer progression.In summary,this subject proves that FXR can antagonize gastric cancer by regulating the AMPK/LINC01876 axis,which provides a new idea and theoretical basis for the diagnosis,treatment,and prognosis of gastric cancer,and provides guidance for the development of targeted drugs for gastric cancer. |
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