title: Activation of the nuclear receptor FXR enhances hepatocyte chemoprotection and liver tumor chemoresistance against genotoxic compounds.
abstract: The success of pharmacological treatments in primary liver cancers is limited by the marked efficacy of mechanisms of chemoresistance already present in hepatocytes. The role of the nuclear receptor FXR is unclear. Although, in non-treated liver tumors, its expression is reduced, the refractoriness to anticancer drugs is high. Moreover, the treatment with cisplatin up-regulates FXR. The aim of this study was to investigate whether FXR is involved in stimulating chemoprotection/chemoresistance in healthy and tumor liver cells. In human hepatocytes, the activation of FXR with the agonist GW4064 resulted in a significant protection against cisplatin-induced toxicity. In human hepatoma Alexander cells, with negligible endogenous expression of FXR, GW4064 also protected against cisplatin-induced toxicity, but only if they were previously transfected with FXR/RXR. Investigation of 109 genes potentially involved in chemoresistance revealed that only ABCB4, TCEA2, CCL14, CCL15 and KRT13 were up-regulated by FXR activation both in human hepatocytes and FXR/RXR-expressing hepatoma cells. In both models, cisplatin, even in the absence of FXR agonists, such as bile acids and GW4064, was able to up-regulate FXR targets genes, which was due to FXR-mediated trans-activation of response elements in the promoter region. FXR-dependent chemoprotection was also efficient against other DNA-damaging compounds, such as doxorubicin, mitomycin C and potassium dichromate, but not against non-genotoxic drugs, such as colchicine, paclitaxel, acetaminophen, artesunate and sorafenib. In conclusion, ligand-dependent and independent activation of FXR stimulates mechanisms able to enhance the chemoprotection of hepatocytes against genotoxic compounds and to reduce the response of liver tumor cells to certain pharmacological treatments.
authors.affiliation: University of Salamanca, Salamanca, Spain.
authors.forename: Javier
authors.initials: J
authors.lastname: Vaquero
authors.forename: Oscar
authors.initials: O
authors.lastname: Briz
authors.forename: Elisa
authors.initials: E
authors.lastname: Herraez
authors.forename: Jordi
authors.initials: J
authors.lastname: Muntané
authors.forename: Jose J G
authors.initials: JJ
authors.lastname: Marin
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology; D014408:Biomarkers, Tumor / Q000235:genetics* / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D002945:Cisplatin / Q000494:pharmacology*; D019008:Drug Resistance, Neoplasm; D020869:Gene Expression Profiling; D022781:Hepatocytes / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D006801:Humans; D007555:Isoxazoles / Q000494:pharmacology*; D008113:Liver Neoplasms / Q000235:genetics / Q000378:metabolism / Q000517:prevention & control*; D008156:Luciferases / Q000378:metabolism; D020411:Oligonucleotide Array Sequence Analysis; D011401:Promoter Regions, Genetic / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics; D016601:RNA-Binding Proteins / Q000819:agonists / Q000378:metabolism*; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014158:Transcription, Genetic; D015533:Transcriptional Activation
chemical_list: D000970:Antineoplastic Agents; D014408:Biomarkers, Tumor; C096916:FXR1 protein, human; D007555:Isoxazoles; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D008156:Luciferases; D002945:Cisplatin; C412815:GW 4064
keywords: Bile acid; Cancer; Chemotherapy; Drug; FXR; HCC; Liver; MOC; Pharmacology; RXR; TLDA; Taqman low density array; farnesoid X receptor; hepatocellular carcinoma; mechanisms of chemoresistance; retinoid X receptor