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In vivo screen identifies LXR agonism potentiates sorafenib killing of hepatocellular carcinoma

ABSTRACT: Background & Aims: Existing drug therapies for hepatocellular carcinoma (HCC), including sorafenib, extend patient survival by only three months. We sought to identify novel druggable targets for use in combination with sorafenib to increase its efficacy. Methods: We implemented an in vivo genetic screening paradigm utilizing a library of 43 genes-of-interest expressed in the context of repopulation of the injured livers of Fumarylacetoacetate Hydrolase-deficient (Fah-/-) mice, which led to highly penetrant HCC. We treated mice with vehicle or sorafenib, then determined the genetic drivers of each tumor from the library. Liver X Receptor alpha (LXRalpha) emerged as a potential target. To examine LXRalpha agonism in combination with sorafenib treatment, we added varying concentrations of sorafenib and LXRalpha agonist drugs to HCC cell lines. To elucidate the mechanism of tumor death, we performed transcriptomic analysis. Results: Fah-/- mice injected with the screening library developed HCC tumor clones containing Myc cDNA plus various other cDNAs. Treatment with sorafenib resulted in sorafenib-resistant HCCs that were significantly depleted in Nr1h3 cDNA, encoding LXRalpha, suggesting that LXRalpha activation is incompatible with tumor growth in the presence of sorafenib treatment in vivo. Combination treatment using sorafenib and LXR agonist drugs in multiple HCC cell lines led to enhanced cell death as compared to monotherapy, due to reduced expression of cell cycle regulators and increased expression of genes associated with apoptosis. Combination therapy also enhanced cell death in a sorafenib-resistant primary human HCC cell line. Conclusions: We have completed a novel drug resistance screen in vivo, and identified that LXR agonism potentiates the efficacy of sorafenib in treating HCC.

ORGANISM(S): Homo sapiens

PROVIDER: GSE151412 | GEO | 2020/05/29

REPOSITORIES: GEO

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Project description:Molecular targeted therapy has shown promise as a treatment for advanced hepatocellular carcinoma (HCC). Sorafenib, a multikinase inhibitor, recently received FDA approval for the treatment of advanced HCC. However, although sorafenib is well tolerated, concern for its safety has been expressed. Celecoxib (CelebrexM-BM-.) is a selective cyclooxygenase-2 (COX-2) inhibitor wich exhibits antitumor effects in human HCC cells. The present study examined the interaction between celecoxib and sorafenib in two human liver tumor cell lines HepG2 and Huh7. Our data showed that each inhibitor reduced cell growth and the combination of celecoxib with sorafenib synergistically inhibited cell growth and increased apoptosis. To better understand the molecular mechanisms underlying the synergistic antitumor activity of combination, we investigated the expression profile of the combination-treated liver cancer cell lines, using microarray analysis. Combination treatment significantly altered expression levels of 1,986 and 2,483 transcripts in HepG2 and Huh7 cells, respectively. Genes, functionally involved in cell death, signal transduction and regulation of transcription were predominantly up-regulated, while genes implicated in metabolism, cell cycle control and DNA replication and repair were mainly down-regulated upon treatment. However, combination-treated HCC cell line displayed specificity in the expression and activity of crucial factors involved in hepatocarcinogenesis. The altered expression of some of these genes was confirmed by semiquantitative and quantitative RT-PCR and by Western blotting. Many novel genes emerged from our transcriptomics analyses, and further functional analyses may determine whether these genes can serve as potential molecular targets for more effective anti-HCC strategies. To identify new potential mechanisms of combined action of celecoxib and sorafenib, their effects on global gene expression in both cell lines were investigated and compared using the DNA microarray technology. Agilent 44K Human Whole Genome Oligonucleotide Microarrays (containing ~44,000 genes) were used to identify global gene expression changes in the HepG2 and Huh7 hepatocellular carcinoma (HCC) cell lines, following simultaneous treatment with 50 M-BM-5M celecoxib and 7.5 M-BM-5M sorafenib for 48 hours. All microarray experiments (a total of four) were performed in duplicates applying dye-swaps to avoid labeling bias.

Project description:OBJECTIVE: Sorafenib is effective in hepatocellular carcinoma (HCC), but patients ultimately present disease progression. Molecular mechanisms underlying acquired resistance are still unknown. Herein, we characterize the role of tumor-initiating cells (T-ICs) and signaling pathways involved in sorafenib resistance. DESIGN: HCC xenograft mice treated with sorafenib (n=22) were explored for responsiveness (n=5) and acquired resistance (n=17). Mechanism of acquired resistance were assessed by: 1) Role of T-ICs by in vitro sphere formation and in vivo tumorigenesis assays using NOD/SCID mice, 2) Activation of alternative signaling pathways and 3) Efficacy of anti-FGF and anti-IGF drugs in experimental models. Gene expression (microarray, qRT-PCR) and protein analyses (immunohistochemistry, western blot) were conducted. A novel gene signature of sorafenib resistance was generated and tested in 2 independent cohorts. RESULTS: Sorafenib-acquired resistance tumors showed significant enrichment of T-ICs (164 cells needed to create a tumor) vs. sorafenib-sensitive tumors (13400 cells) and non-treated tumors (1292 cells), p<0.001. Tumors with sorafenib-acquired resistance were enriched with IGF and FGF signaling cascades (FDR<0.05). In vitro, cells derived from sorafenib-acquired resistant tumors and two sorafenib-resistant HCC cell lines were responsive to IGF or FGF inhibition. In vivo, FGF blockade delayed tumor growth and improved survival in sorafenib-resistant tumors. A sorafenib-resistance 175-gene signature was characterized by enrichment of progenitor-cell features, aggressive tumoral traits and predicted poor survival in 2 cohorts (n=442 HCC patients). CONCLUSION: Acquired resistance to sorafenib is driven by tumor initiating cells with enrichment of progenitor markers and activation of IGF and FGF signaling. Inhibition of these pathways would benefit a subset of patients after sorafenib progression. Transcriptomic profile of subcutaneous Huh7 cells-derived tumors treated with sorafenib that developed acquired resistance to the drug (n=4), remain responsive to sorafenib (n=3) or were treated with brivanib after development of resistance (n=3). Gene profiling of hepatospheres generated from tumors with acquired resistance to sorafenib (n=3) and non-treated tumors (n=3) was also analyzed.

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In vivo screen identifies LXR agonism potentiates sorafenib killing of hepatocellular carcinoma

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