Publications by authors named "Snorri S Thorgeirsson"

163 Publications

Epigenetic modifications precede molecular alterations and drive human hepatocarcinogenesis.

JCI Insight 2021 Sep 8;6(17). Epub 2021 Sep 8.

Department of Medicine I, University Medical Center Mainz, Mainz, Germany.

Development of primary liver cancer is a multistage process. Detailed understanding of sequential epigenetic alterations is largely missing. Here, we performed Infinium Human Methylation 450k BeadChips and RNA-Seq analyses for genome-wide methylome and transcriptome profiling of cirrhotic liver (n = 7), low- (n = 4) and high-grade (n = 9) dysplastic lesions, and early (n = 5) and progressed (n = 3) hepatocellular carcinomas (HCC) synchronously detected in 8 patients with HCC with chronic hepatitis B infection. Integrative analyses of epigenetically driven molecular changes were identified and validated in 2 independent cohorts comprising 887 HCCs. Mitochondrial DNA sequencing was further employed for clonality analyses, indicating multiclonal origin in the majority of investigated HCCs. Alterations in DNA methylation progressively increased from liver cirrhosis (CL) to dysplastic lesions and reached a maximum in early HCCs. Associated early alterations identified by Ingenuity Pathway Analysis (IPA) involved apoptosis, immune regulation, and stemness pathways, while late changes centered on cell survival, proliferation, and invasion. We further validated 23 putative epidrivers with concomitant expression changes and associated with overall survival. Functionally, Striatin 4 (STRN4) was demonstrated to be epigenetically regulated, and inhibition of STRN4 significantly suppressed tumorigenicity of HCC cell lines. Overall, application of integrative genomic analyses defines epigenetic driver alterations and provides promising targets for potentially novel therapeutic approaches.
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http://dx.doi.org/10.1172/jci.insight.146196DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8492348PMC
September 2021

c-Met Signaling Is Essential for Mouse Adult Liver Progenitor Cells Expansion After Transforming Growth Factor-β-Induced Epithelial-Mesenchymal Transition and Regulates Cell Phenotypic Switch.

Stem Cells 2019 08 18;37(8):1108-1118. Epub 2019 Jun 18.

Department of Biochemistry and Molecular Biology, Faculty of Pharmacy, Complutense University of Madrid, Health Research Institute of the Hospital Clínico San Carlos, Madrid, Spain.

Adult hepatic progenitor cells (HPCs)/oval cells are bipotential progenitors that participate in liver repair responses upon chronic injury. Recent findings highlight HPCs plasticity and importance of the HPCs niche signals to determine their fate during the regenerative process, favoring either fibrogenesis or damage resolution. Transforming growth factor-β (TGF-β) and hepatocyte growth factor (HGF) are among the key signals involved in liver regeneration and as component of HPCs niche regulates HPCs biology. Here, we characterize the TGF-β-triggered epithelial-mesenchymal transition (EMT) response in oval cells, its effects on cell fate in vivo, and the regulatory effect of the HGF/c-Met signaling. Our data show that chronic treatment with TGF-β triggers a partial EMT in oval cells based on coexpression of epithelial and mesenchymal markers. The phenotypic and functional profiling indicates that TGF-β-induced EMT is not associated with stemness but rather represents a step forward along hepatic lineage. This phenotypic transition confers advantageous traits to HPCs including survival, migratory/invasive and metabolic benefit, overall enhancing the regenerative potential of oval cells upon transplantation into a carbon tetrachloride-damaged liver. We further uncover a key contribution of the HGF/c-Met pathway to modulate the TGF-β-mediated EMT response. It allows oval cells expansion after EMT by controlling oxidative stress and apoptosis, likely via Twist regulation, and it counterbalances EMT by maintaining epithelial properties. Our work provides evidence that a coordinated and balanced action of TGF-β and HGF are critical for achievement of the optimal regenerative potential of HPCs, opening new therapeutic perspectives. Stem Cells 2019;37:1108-1118.
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http://dx.doi.org/10.1002/stem.3038DOI Listing
August 2019

Genome-Wide RNAi Screen Identifies PMPCB as a Therapeutic Vulnerability in EpCAM Hepatocellular Carcinoma.

Cancer Res 2019 05 12;79(9):2379-2391. Epub 2019 Mar 12.

Laboratory of Human Carcinogenesis, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland.

Hepatocellular carcinoma (HCC) is a genetically heterogeneous disease for which a dominant actionable molecular driver has not been identified. Patients with the stem cell-like EpCAMAFP HCC subtype have poor prognosis. Here, we performed a genome-wide RNAi screen to identify genes with a synthetic lethal interaction with EpCAM as a potential therapeutic target for the EpCAMAFP HCC subtype. We identified 26 candidate genes linked to EpCAM/Wnt/β-catenin signaling and HCC cell growth. We further characterized the top candidate PMPCB, which plays a role in mitochondrial protein processing, as a target for EpCAM HCC. PMPCB blockage suppressed EpCAM expression and Wnt/β-catenin signaling via mitochondria-related reactive oxygen species production and FOXO activities, resulting in apoptosis and tumor suppression. These results indicate that a synthetic lethality screen is a viable strategy to identify actionable drivers of HCC and identify PMPCB as a therapeutically vulnerable gene in EpCAM HCC subpopulations. SIGNIFICANCE: This study identifies PMPCB as critical to mitochondrial homeostasis and a synthetic lethal candidate that selectively kills highly resistant EpCAM HCC tumors by inactivating the Wnt/β-catenin signaling pathway.
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http://dx.doi.org/10.1158/0008-5472.CAN-18-3015DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6497533PMC
May 2019

Application of patient-derived liver cancer cells for phenotypic characterization and therapeutic target identification.

Int J Cancer 2019 06 14;144(11):2782-2794. Epub 2018 Dec 14.

Department of Medicine I, Lichtenberg Research Group, Johannes Gutenberg University, Mainz, Germany.

Primary liver cancer (PLC) ranks among the most lethal solid cancers worldwide due to lack of effective biomarkers for early detection and limited treatment options in advanced stages. Development of primary culture models that closely recapitulate phenotypic and molecular diversities of PLC is urgently needed to improve the patient outcome. Long-term cultures of 7 primary liver cancer cell lines of hepatocellular and cholangiocellular origin were established using defined culture conditions. Morphological and histological characteristics of obtained cell lines and xenograft tumors were analyzed and compared to original tumors. Time course analyses of transcriptomic and genomic changes were performed using next-generation sequencing (NGS). Key oncogenic alterations were identified by targeted NGS and cell lines carrying potentially actionable mutations were treated with corresponding specific inhibitors. PDCL fully resembled morphological features of the primary cancers in vitro and in vivo over extended period in culture. Genomic alterations as well as transcriptome profiles showed high similarity with primary tumors and remained stable during long-term culturing. Targeted-NGS confirmed that key oncogenic mutations such as TP53, KRAS, CTNNB1 as well as actionable mutations (e.g. MET, cKIT, KDR) were highly conserved in PDCL and amenable for individualized therapeutic approaches. Integrative genomic and transcriptomic approaches further demonstrated that PDCL more closely resemble molecular and prognostic features of PLC than established cell lines and are valuable tool for direct target evaluation. Our integrative analysis demonstrates that PDCL represents refined model for discovery of relevant molecular subgroups and exploration of precision medicine approaches for the treatment of this deadly disease.
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http://dx.doi.org/10.1002/ijc.32026DOI Listing
June 2019

Integrated Genomic Comparison of Mouse Models Reveals Their Clinical Resemblance to Human Liver Cancer.

Mol Cancer Res 2018 11 6;16(11):1713-1723. Epub 2018 Aug 6.

Department of Systems Biology, The University of Texas MD Anderson Cancer Center, Houston, Texas.

Hepatocellular carcinoma (HCC) is a heterogeneous disease. Mouse models are commonly used as preclinical models to study hepatocarcinogenesis, but how well these models recapitulate molecular subtypes of human HCC is unclear. Here, integration of genomic signatures from molecularly and clinically defined human HCC ( = 11) and mouse models of HCC ( = 9) identified the mouse models that best resembled subtypes of human HCC and determined the clinical relevance of each model. knockout (KO), KO, and SV40 T antigen mouse models effectively recapitulated subtypes of human HCC with a poor prognosis, whereas the transgenic model best resembled human HCCs with a more favorable prognosis. The model was also associated with activation of β-catenin. , and diethylnitrosamine (DEN)-induced models were heterogeneous and were unequally split into poor and favorable prognoses. KO and KO models best resemble human HCC with hepatic stem cell characteristics. Applying a genomic predictor for immunotherapy, the six-gene IFNγ score, the KO, KO, SV40, and DEN models were predicted to be the least responsive to immunotherapy. Further analysis showed that elevated expression of immune-inhibitory genes ( and Nectin2/) in KO, KO, and SV40 models and decreased expression of immune stimulatory gene () in the DEN model might be accountable for the lack of predictive response to immunotherapy. The current genomic approach identified the most relevant mouse models to human liver cancer and suggests immunotherapeutic potential for the treatment of specific subtypes. .
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http://dx.doi.org/10.1158/1541-7786.MCR-18-0313DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6431260PMC
November 2018

Common Molecular Subtypes Among Asian Hepatocellular Carcinoma and Cholangiocarcinoma.

Cancer Cell 2017 07 22;32(1):57-70.e3. Epub 2017 Jun 22.

Georgetown University Medical Center, Washington, DC 20057, USA.

Intrahepatic cholangiocarcinoma (ICC) and hepatocellular carcinoma (HCC) are clinically disparate primary liver cancers with etiological and biological heterogeneity. We identified common molecular subtypes linked to similar prognosis among 199 Thai ICC and HCC patients through systems integration of genomics, transcriptomics, and metabolomics. While ICC and HCC share recurrently mutated genes, including TP53, ARID1A, and ARID2, mitotic checkpoint anomalies distinguish the C1 subtype with key drivers PLK1 and ECT2, whereas the C2 subtype is linked to obesity, T cell infiltration, and bile acid metabolism. These molecular subtypes are found in 582 Asian, but less so in 265 Caucasian patients. Thus, Asian ICC and HCC, while clinically treated as separate entities, share common molecular subtypes with similar actionable drivers to improve precision therapy.
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http://dx.doi.org/10.1016/j.ccell.2017.05.009DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5524207PMC
July 2017

Transcriptomic and histopathological analysis of cholangiolocellular differentiation trait in intrahepatic cholangiocarcinoma.

Liver Int 2018 01 10;38(1):113-124. Epub 2017 Jul 10.

Department of Pathology, Yonsei University College of Medicine, Seoul, Korea.

Background & Aims: Intrahepatic cholangiocarcinoma (iCCA) is a heterogeneous entity with diverse aetiologies, morphologies and clinical outcomes. Recently, histopathological distinction of cholangiolocellular differentiation (CD) of iCCA has been suggested. However, its genome-wide molecular features and clinical significance remain unclear.

Methods: Based on CD status, we stratified iCCAs into iCCA with CD (n=20) and iCCA without CD (n=102), and performed an integrative analysis using transcriptomic and clinicopathological profiles.

Results: iCCA with CD revealed less aggressive histopathological features compared to iCCA without CD, and iCCA with CD showed favourable clinical outcomes of overall survival and time to recurrence than iCCA without CD (P<.05 for all). Transcriptomic profiling revealed that iCCA with CD resembled an inflammation-related subtype, while iCCA without CD resembled a proliferation subtype. In addition, we identified a CD signature that can predict prognostic outcomes of iCCA (CD_UP, n=486 and CD_DOWN, n=308). iCCAs were subgrouped into G1 (positivity for CRP and CDH2, 7%), G3 (positivity for S100P and TFF1, 32%) and G2 (the others, 61%). Prognostic outcomes for overall survival (P=.001) and time to recurrence (P=.017) were the most favourable in G1-iCCAs, intermediate in G2-iCCAs and the worst in G3-iCCAs. Similar result was confirmed in the iCCA set from GSE26566 (n=68).

Conclusions: CD signature was identified to predict the prognosis of iCCA. The combined evaluation of histology of CD and protein expression status of CRP, CDH2, TFF1 and S100P might help subtyping and predicting clinical outcomes of iCCA.
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http://dx.doi.org/10.1111/liv.13492DOI Listing
January 2018

Stemness in Liver Cancer.

Dig Dis 2017 3;35(4):387-389. Epub 2017 May 3.

Laboratory of Human Carcinogenesis, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, MD, USA.

Cancer cells possessing "stemness," or stem-cell properties, are referred to as cancer stem cells (CSC) or cancer-initiating cells. The concept that these cells rest at the apex of the cancer hierarchy is an evolving theme in cancer research. These cells are by definition primarily responsible for the initiation and propagation of tumors as well as relapse after therapy, and they are therefore of major scientific interest. Several studies indicate that hepatocellular carcinomas that harbor phenotypic features of stem cells and progenitor cells constitute a subclass of therapeutically challenging cancers that are associated with a particularly poor prognosis. We recently demonstrated that any cell type in the mouse hepatic lineage can undergo oncogenic reprogramming into a CSC by activating different cell type-specific pathways [1]. Identification of common and cell of origin-specific phenotypic and genetic changes could provide new therapeutic targets for liver cancer.
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http://dx.doi.org/10.1159/000456592DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5841535PMC
October 2017

Adverse genomic alterations and stemness features are induced by field cancerization in the microenvironment of hepatocellular carcinomas.

Oncotarget 2017 Jul;8(30):48688-48700

Department of Medicine, Johannes Gutenberg University, Mainz, Germany.

Hepatocellular Carcinoma (HCC) commonly develops in chronically damaged liver tissues. The resulting regenerative and inflammatory processes create an adverse milieu that promotes tumor-initiation and progression. A better understanding of the hepatic tumor-microenvironment interaction might infer profound therapeutic implications.Integrative whole genome and transcriptome analyses of different tumor regions, the invasive tumor border and tumor-surrounding liver (SL) were performed to identify associated molecular alterations and integrated with our existing HCC database. Expression levels and localization of established CSC markers were assessed in pre-neoplastic lesions and confirmed in two independent patient cohorts using qRT-PCR, immunohistochemistry and immunofluorescence.Our results indicate that genomic and transcriptomic profiles between SL and different tumor regions are quite distinct. Progressive increase in genetic alterations and activation of pathways related to proliferation as well as apoptosis were observed in the tumor tissue, while activation of stemness markers was present in cirrhotic SL and continuously decreased from pre-neoplastic lesions to HCC. Interestingly, the invasive tumor border was characterized by inflammatory and EMT-related gene sets as well as activation of pro-survival signaling. Consistently, integration of gene expression signatures with two independent HCC databases containing 300 HCCs revealed that border signatures are predictive of HCC patient survival.Prognostic significance of the permissive liver microenvironment might be a consequence of a pro-oncogenic field effect that is caused by chronic regenerative processes. Activation of key oncogenic features and immune-response signaling indicates that the cross-talk between tumor and microenvironment might be a promising therapeutic and/or preventive target.
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http://dx.doi.org/10.18632/oncotarget.16231DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5564717PMC
July 2017

Transcriptional Induction of Periostin by a Sulfatase 2-TGFβ1-SMAD Signaling Axis Mediates Tumor Angiogenesis in Hepatocellular Carcinoma.

Cancer Res 2017 02 21;77(3):632-645. Epub 2016 Nov 21.

Division of Gastroenterology and Hepatology, Mayo Clinic College of Medicine and Science, Rochester, Minnesota.

Existing antiangiogenic approaches to treat metastatic hepatocellular carcinoma (HCC) are weakly effectual, prompting further study of tumor angiogenesis in this disease setting. Here, we report a novel role for sulfatase 2 (SULF2) in driving HCC angiogenesis. Sulf2-deficient mice (Sulf2 KO) exhibited resistance to diethylnitrosamine-induced HCC and did not develop metastases like wild-type mice (Sulf2 WT). The smaller and less numerous tumors formed in Sulf2 KO mice exhibited a markedly lower microvascular density. In human HCC cells, SULF2 overexpression increased endothelial proliferation, adhesion, chemotaxis, and tube formation in a paracrine fashion. Mechanistic analyses identified the extracellular matrix protein periostin (POSTN), a ligand of αvβ3/5 integrins, as an effector protein in SULF2-induced angiogenesis. POSTN silencing in HCC cells attenuated SULF2-induced angiogenesis and tumor growth in vivo The TGFβ1/SMAD pathway was identified as a critical signaling axis between SULF2 and upregulation of POSTN transcription. In clinical HCC specimens, elevated levels of SULF2 correlated with increased microvascular density, POSTN levels, and relatively poorer patient survival. Together, our findings define an important axis controlling angiogenesis in HCC and a mechanistic foundation for rational drug development. Cancer Res; 77(3); 632-45. ©2016 AACR.
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http://dx.doi.org/10.1158/0008-5472.CAN-15-2556DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5429157PMC
February 2017

Plasma glutamate carboxypeptidase is a negative regulator in liver cancer metastasis.

Oncotarget 2016 Nov;7(48):79774-79786

Genome Research Center, Korea Research Institute of Bioscience and Biotechnology, Daejeon 305-333, Republic of Korea.

Tumor metastasis is the leading cause of cancer death. In the metastatic process, EMT is a unique phenotypic change that plays an important role in cell invasion and changes in cell morphology. Despite the clinical significance, the mechanism underlying tumor metastasis is still poorly understood. Here we report a novel mechanism by which secreted plasma glutamate carboxypeptidase(PGCP) negatively involves Wnt/β-catenin signaling by DKK4 regulation in liver cancer metastasis. Pathway analysis of the RNA sequencing data showed that PGCP knockdown in liver cancer cell lines enriched the functions of cell migration, motility and mesenchymal cell differentiation. Depletion of PGCP promoted cell migration and invasion via activation of Wnt/β-catenin signaling pathway components such as phospho-LRP6 and β-catenin. Also, addition of DKK4 antagonized the Wnt/β-catenin signaling cascade in a thyroxine (T4)-dependent manner. In an in vivo study, metastatic nodules were observed in the lungs of the mice after injection of shPGCP stable cell lines. Our findings suggest that PGCP negatively associates with Wnt/β-catenin signaling during metastasis. Targeting this regulation may represent a novel and effective therapeutic option for liver cancer by preventing metastatic activity of primary tumor cells.
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http://dx.doi.org/10.18632/oncotarget.12967DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5340238PMC
November 2016

Heat Stress-Induced PI3K/mTORC2-Dependent AKT Signaling Is a Central Mediator of Hepatocellular Carcinoma Survival to Thermal Ablation Induced Heat Stress.

PLoS One 2016 9;11(9):e0162634. Epub 2016 Sep 9.

Department of Radiology, Mayo Clinic College of Medicine, Rochester, MN, United States of America.

Thermal ablative therapies are important treatment options in the multidisciplinary care of patients with hepatocellular carcinoma (HCC), but lesions larger than 2-3 cm are plagued with high local recurrence rates and overall survival of these patients remains poor. Currently no adjuvant therapies exist to prevent local HCC recurrence in patients undergoing thermal ablation. The molecular mechanisms mediating HCC resistance to thermal ablation induced heat stress and local recurrence remain unclear. Here we demonstrate that the HCC cells with a poor prognostic hepatic stem cell subtype (Subtype HS) are more resistant to heat stress than HCC cells with a better prognostic hepatocyte subtype (Subtype HC). Moreover, sublethal heat stress rapidly induces phosphoinositide 3-kinase (PI3K)/mammalian target of rapamycin (mTOR) dependent-protein kinase B (AKT) survival signaling in HCC cells in vitro and at the tumor ablation margin in vivo. Conversely, inhibition of PI3K/mTOR complex 2 (mTORC2)-dependent AKT phosphorylation or direct inhibition of AKT function both enhance HCC cell killing and decrease HCC cell survival to sublethal heat stress in both poor and better prognostic HCC subtypes while mTOR complex 1 (mTORC1)-inhibition has no impact. Finally, we showed that AKT isoforms 1, 2 and 3 are differentially upregulated in primary human HCCs and that overexpression of AKT correlates with worse tumor biology and pathologic features (AKT3) and prognosis (AKT1). Together these findings define a novel molecular mechanism whereby heat stress induces PI3K/mTORC2-dependent AKT survival signaling in HCC cells and provide a mechanistic rationale for adjuvant AKT inhibition in combination with thermal ablation as a strategy to enhance HCC cell killing and prevent local recurrence, particularly at the ablation margin.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0162634PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5017586PMC
August 2017

Loss of c-Met signaling sensitizes hepatocytes to lipotoxicity and induces cholestatic liver damage by aggravating oxidative stress.

Toxicology 2016 06 6;361-362:39-48. Epub 2016 Jul 6.

1st Department of Medicine, University Medical Center, Johannes Gutenberg University Mainz, Langenbeckstrasse 1, 55131 Mainz, Germany. Electronic address:

Recent studies confirmed a critical importance of c-Met signaling for liver regeneration by modulating redox balance. Here we used liver-specific conditional knockout mice (MetKO) and a nutritional model of hepatic steatosis to address the role of c-Met in cholesterol-mediated liver toxicity. Liver injury was assessed by histopathology and plasma enzymes levels. Global transcriptomic changes were examined by gene expression microarray, and key molecules involved in liver damage and lipid homeostasis were evaluated by Western blotting. Loss of c-Met signaling amplified the extent of liver injury in MetKO mice fed with high-cholesterol diet for 30days as evidenced by upregulation of liver enzymes and increased synthesis of total bile acids, aggravated inflammatory response and enhanced intrahepatic lipid deposition. Global transcriptomic changes confirmed the enrichment of networks involved in steatosis and cholestasis. In addition, signaling pathways related to glutathione and lipid metabolism, oxidative stress and mitochondria dysfunction were significantly affected by the loss of c-Met function. Mechanistically, exacerbation of oxidative stress in MetKO livers was corroborated by increased lipid and protein oxidation. Western blot analysis further revealed suppression of Erk, NF-kB and Nrf2 survival pathways and downstream target genes (e.g. cyclin D1, SOD1, gamma-GCS), as well as up-regulation of proapoptotic signaling (e.g. p53, caspase 3). Consistent with the observed steatotic and cholestatic phenotype, nuclear receptors RAR, RXR showed increased activation while expression levels of CAR, FXR and PPAR-alpha were decreased in MetKO. Collectively, our data provide evidence for the critical involvement of c-Met signaling in cholesterol and bile acids toxicity.
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http://dx.doi.org/10.1016/j.tox.2016.07.004DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5131870PMC
June 2016

Liver Label Retaining Cancer Cells Are Relatively Resistant to the Reported Anti-Cancer Stem Cell Drug Metformin.

J Cancer 2016 6;7(9):1142-51. Epub 2016 Jun 6.

1. Surgery Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA;; 6. Department of Surgery, Saint Peter's Healthcare System, Rutgers University, New Brunswick, NJ 08901, USA.

Background & Aims: Recently, we reported that liver Label Retaining Cancer Cells (LRCC) can initiate tumors with only 10 cells and are relatively resistant to the targeted drug Sorafenib, a standard of practice in advanced hepatocellular carcinoma (HCC). LRCC are the only cancer stem cells (CSC) isolated alive according to a stem cell fundamental function, asymmetric cell division. Metformin has been reported to preferentially target many other types of CSC of different organs, including liver. It's important to know if LRCC, a novel class of CSC, are relatively resistant to metformin, unlike other types of CSC. As metformin inhibits the Sorafenib-Target-Protein (STP) PI3K, and LRCC are newly described CSC, we undertook this study to test the effects of Metformin on Sorafenib-treated HCC and HCC-derived-LRCC.

Methods: We tested various STP levels and phosphorylation status, associated genes' expression, proliferation, viability, toxicity, and apoptosis profiles, before and after treatment with Sorafenib with/without Metformin.

Results: Metformin enhances the effects of Sorafenib on HCC, and significantly decreased viability/proliferation of HCC cells. This insulin-independent effect was associated with inhibition of multiple STPs (PKC, ERK, JNK and AKT). However, Metformin increased the relative proportion of LRCCs. Comparing LRCC vs. non-LRCC, this effect was associated with improved toxicity and apoptosis profiles, down-regulation of cell death genes and up-regulation of cell proliferation and survival genes in LRCC. Concomitantly, Metformin up-regulated pluripotency, Wnt, Notch and SHH pathways genes in LRCC vs. non-LRCC.

Conclusions: Metformin and Sorafenib have enhanced anti-cancer effects. However, in contradistinction to reports on other types of CSC, Metformin is less effective against HCC-derived-CSC LRCC. Our results suggest that combining Metformin with Sorafenib may be able to repress the bulk of tumor cells, but as with other anti-cancer drugs, may leave LRCC behind leading to cancer recurrence. Therefore, liver LRCC, unlike other types of CSC, are relatively resistant to the reported anti-cancer stem cell drug metformin. This is the first report that there is a type of CSC that is not relatively resistant to the CSC-targeting drug. Our findings suggest that a drug targeting LRCC may be critically needed to target CSC and prevent cancer recurrence. These may significantly contribute to the understanding of Metformin's anti-cancer effects and the development of novel drugs targeting the relatively resistant LRCC.
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http://dx.doi.org/10.7150/jca.10047DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4911882PMC
June 2016

DNMT1 is a required genomic regulator for murine liver histogenesis and regeneration.

Hepatology 2016 08 28;64(2):582-98. Epub 2016 Apr 28.

Laboratory of Experimental Carcinogenesis, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD.

Unlabelled: DNA methyltransferase 1 (DNMT1) is an essential regulator maintaining both epigenetic reprogramming during DNA replication and genome stability. We investigated the role of DNMT1 in the regulation of postnatal liver histogenesis under homeostasis and stress conditions. We generated Dnmt1 conditional knockout mice (Dnmt1(Δalb) ) by crossing Dnmt1(fl/fl) with albumin-cyclization recombination transgenic mice. Serum, liver tissues, and primary hepatocytes were collected from 1-week-old to 20-week old mice. The Dnmt1(Δalb) phenotype was assessed by histology, confocal and electron microscopy, biochemistry, as well as transcriptome and methylation profiling. Regenerative growth was induced by partial hepatectomy and exposure to carbon tetrachloride. The impact of Dnmt1 knockdown was also analyzed in hepatic progenitor cell lines; proliferation, apoptosis, DNA damage, and sphere formation were assessed. Dnmt1 loss in postnatal hepatocytes caused global hypomethylation, enhanced DNA damage response, and initiated a senescence state causing a progressive inability to maintain tissue homeostasis and proliferate in response to injury. The liver regenerated through activation and repopulation from progenitors due to lineage-dependent differences in albumin-cyclization recombination expression, providing a basis for selection of less mature and therefore less damaged hepatic progenitor cell progeny. Consistently, efficient knockdown of Dnmt1 in cultured hepatic progenitor cells caused severe DNA damage, cell cycle arrest, senescence, and cell death. Mx1-cyclization recombination-driven deletion of Dnmt1 in adult quiescent hepatocytes did not affect liver homeostasis.

Conclusion: These results establish the indispensable role of DNMT1-mediated epigenetic regulation in postnatal liver growth and regeneration; Dnmt1(Δalb) mice provide a unique experimental model to study the role of senescence and the contribution of progenitor cells to physiological and regenerative liver growth. (Hepatology 2016;64:582-598).
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http://dx.doi.org/10.1002/hep.28563DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5841553PMC
August 2016

Oncogenic driver genes and the inflammatory microenvironment dictate liver tumor phenotype.

Hepatology 2016 06 15;63(6):1888-99. Epub 2016 Mar 15.

Laboratory of Experimental Carcinogenesis, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD.

Unlabelled: The majority of hepatocellular carcinoma develops in the background of chronic liver inflammation caused by viral hepatitis and alcoholic or nonalcoholic steatohepatitis. However, the impact of different types of chronic inflammatory microenvironments on the phenotypes of tumors generated by distinct oncogenes is largely unresolved. To address this issue, we generated murine liver tumors by constitutively active AKT-1 (AKT) and β-catenin (CAT), followed by induction of chronic liver inflammation by 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC) and carbon tetrachloride. Also, the impact of DDC-induced chronic liver inflammation was compared between two liver tumor models using a combination of AKT-CAT or AKT-NRAS(G12V) . Treatment with DDC and carbon tetrachloride significantly facilitated the adenoma-to-carcinoma conversion and accelerated the growth of AKT-CAT tumors. Furthermore, DDC treatment altered the morphology of AKT-CAT tumors and caused loss of lipid droplets. Transcriptome analysis of AKT-CAT tumors revealed that cellular growth and proliferation were mainly affected by chronic inflammation and caused up-regulation of Cxcl16, Galectin-3, and Nedd9, among others. Integration with transcriptome profiles from human hepatocellular carcinomas further demonstrated that AKT-CAT tumors generated in the context of chronic liver inflammation showed enrichment of poor prognosis gene sets or decrease of good prognosis gene sets. In contrast, DDC had a more subtle effect on AKT-NRAS(G12V) tumors and primarily enhanced already existent tumor characteristics as supported by transcriptome analysis. However, it also reduced lipid droplets in AKT-NRAS(G12V) tumors.

Conclusion: Our study suggests that liver tumor phenotype is defined by a combination of driving oncogenes but also the nature of chronic liver inflammation. (Hepatology 2016;63:1888-1899).
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http://dx.doi.org/10.1002/hep.28487DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4874846PMC
June 2016

A Gene Expression Signature Associated with Overall Survival in Patients with Hepatocellular Carcinoma Suggests a New Treatment Strategy.

Mol Pharmacol 2016 Feb 14;89(2):263-72. Epub 2015 Dec 14.

Laboratory of Cell Biology (J-P.G., J.P.M., C-P.W., A.M.C., S.V.A., M.M.G.) and Laboratory of Experimental Carcinogenesis (J.B.A., S.S.T.), Center for Cancer Research, National Cancer Institute, and Bioinformatics and Computational Biosciences Branch, Office of Cyber Infrastructure and Computational Biology, Office of Science Management and Operations, National Institute of Allergy and Infectious Diseases (S.V.), National Institutes of Health, Bethesda, Maryland; and the Viral Technologies Group and Molecular Detection Group, Protein Expression Laboratory, Frederick National Laboratory for Cancer Research, National Institutes of Health, Frederick, Marylanld (R.K.B., K.P., W.E.B.)

Despite improvements in the management of liver cancer, the survival rate for patients with hepatocellular carcinoma (HCC) remains dismal. The survival benefit of systemic chemotherapy for the treatment of liver cancer is only marginal. Although the reasons for treatment failure are multifactorial, intrinsic resistance to chemotherapy plays a primary role. Here, we analyzed the expression of 377 multidrug resistance (MDR)-associated genes in two independent cohorts of patients with advanced HCC, with the aim of finding ways to improve survival in this poor-prognosis cancer. Taqman-based quantitative polymerase chain reaction revealed a 45-gene signature that predicts overall survival (OS) in patients with HCC. Using the Connectivity Map Tool, we were able to identify drugs that converted the gene expression profiles of HCC cell lines from ones matching patients with poor OS to profiles associated with good OS. We found three compounds that convert the gene expression profiles of three HCC cell lines to gene expression profiles associated with good OS. These compounds increase histone acetylation, which correlates with the synergistic sensitization of those MDR tumor cells to conventional chemotherapeutic agents, including cisplatin, sorafenib, and 5-fluorouracil. Our results indicate that it is possible to modulate gene expression profiles in HCC cell lines to those associated with better outcome. This approach also increases sensitization of HCC cells toward conventional chemotherapeutic agents. This work suggests new treatment strategies for a disease for which few therapeutic options exist.
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http://dx.doi.org/10.1124/mol.115.101360DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4727122PMC
February 2016

Stemness and reprogramming in liver cancer.

Hepatology 2016 Apr 14;63(4):1068-70. Epub 2016 Jan 14.

Laboratory of Human Carcinogenesis, National Cancer Institute, National Institutes of Health, Bethesda, MD.

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http://dx.doi.org/10.1002/hep.28362DOI Listing
April 2016

Functional and genetic deconstruction of the cellular origin in liver cancer.

Nat Rev Cancer 2015 Nov;15(11):653-67

Laboratory of Experimental Carcinogenesis, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA.

During the past decade, research on primary liver cancers has particularly highlighted the uncommon plasticity of differentiated parenchymal liver cells (that is, hepatocytes and cholangiocytes (also known as biliary epithelial cells)), the role of liver progenitor cells in malignant transformation, the importance of the tumour microenvironment and the molecular complexity of liver tumours. Whereas other reviews have focused on the landscape of genetic alterations that promote development and progression of primary liver cancers and the role of the tumour microenvironment, the crucial importance of the cellular origin of liver cancer has been much less explored. Therefore, in this Review, we emphasize the importance and complexity of the cellular origin in tumour initiation and progression, and attempt to integrate this aspect with recent discoveries in tumour genomics and the contribution of the disrupted hepatic microenvironment to liver carcinogenesis.
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http://dx.doi.org/10.1038/nrc4017DOI Listing
November 2015

Lack of mitochondrial topoisomerase I (TOP1mt) impairs liver regeneration.

Proc Natl Acad Sci U S A 2015 Sep 24;112(36):11282-7. Epub 2015 Aug 24.

Developmental Therapeutics Branch, Laboratory of Molecular Pharmacology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892;

The liver has an exceptional replicative capacity following partial hepatectomy or chemical injuries. Cellular proliferation requires increased production of energy and essential metabolites, which critically depend on the mitochondria. To determine whether Top1mt, the vertebrate mitochondrial topoisomerase, is involved in this process, we studied liver regeneration after carbon tetrachloride (CCl4) administration. TOP1mt knockout (KO) mice showed a marked reduction in regeneration and hepatocyte proliferation. The hepatic mitochondrial DNA (mtDNA) failed to increase during recovery from CCl4 exposure. Reduced glutathione was also depleted, indicating increased reactive oxygen species (ROS). Steady-state levels of ATP, O2 consumption, mtDNA, and mitochondrial mass were also reduced in primary hepatocytes from CCl4-treated KO mice. To further test whether Top1mt acted by enabling mtDNA regeneration, we tested TOP1mt KO fibroblasts and human colon carcinoma HCT116 cells and measured mtDNA after 3-d treatment with ethidium bromide. Both types of TOP1mt knockout cells showed defective mtDNA regeneration following mtDNA depletion. Our study demonstrates that Top1mt is required for normal mtDNA homeostasis and for linking mtDNA expansion with hepatocyte proliferation.
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http://dx.doi.org/10.1073/pnas.1511016112DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4568654PMC
September 2015

Identification of a mitochondrial defect gene signature reveals NUPR1 as a key regulator of liver cancer progression.

Hepatology 2015 Oct 7;62(4):1174-89. Epub 2015 Aug 7.

Department of Biochemistry, Ajou University School of Medicine, Suwon, Korea.

Unlabelled: Many cancer cells require more glycolytic adenosine triphosphate production due to a mitochondrial respiratory defect. However, the roles of mitochondrial defects in cancer development and progression remain unclear. To address the role of transcriptomic regulation by mitochondrial defects in liver cancer cells, we performed gene expression profiling for three different cell models of mitochondrial defects: cells with chemical respiratory inhibition (rotenone, thenoyltrifluoroacetone, antimycin A, and oligomycin), cells with mitochondrial DNA depletion (Rho0), and liver cancer cells harboring mitochondrial defects (SNU354 and SNU423). By comparing gene expression in the three models, we identified 10 common mitochondrial defect-related genes that may be responsible for retrograde signaling from cancer cell mitochondria to the intracellular transcriptome. The concomitant expression of the 10 common mitochondrial defect genes is significantly associated with poor prognostic outcomes in liver cancers, suggesting their functional and clinical relevance. Among the common mitochondrial defect genes, we found that nuclear protein 1 (NUPR1) is one of the key transcription regulators. Knockdown of NUPR1 suppressed liver cancer cell invasion, which was mediated in a Ca(2+) signaling-dependent manner. In addition, by performing an NUPR1-centric network analysis and promoter binding assay, granulin was identified as a key downstream effector of NUPR1. We also report association of the NUPR1-granulin pathway with mitochondrial defect-derived glycolytic activation in human liver cancer.

Conclusion: Mitochondrial respiratory defects and subsequent retrograde signaling, particularly the NUPR1-granulin pathway, play pivotal roles in liver cancer progression.
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http://dx.doi.org/10.1002/hep.27976DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6312643PMC
October 2015

Signal transducer and activator of transcription 3-mediated CD133 up-regulation contributes to promotion of hepatocellular carcinoma.

Hepatology 2015 Oct 28;62(4):1160-73. Epub 2015 Aug 28.

Department of Pharmacology and Biomedical Sciences, Seoul National University College of Medicine, Seoul, South Korea.

Unlabelled: Enhanced expression of the cancer stem cell (CSC) marker, CD133, is closely associated with a higher rate of tumor formation and poor prognosis in hepatocellular carcinoma (HCC) patients. Despite its clinical significance, the molecular mechanism underlying the deregulation of CD133 during tumor progression remains to be clarified. Here, we report on a novel mechanism by which interleukin-6/signal transducer and activator of transcription 3 (IL-6/STAT3) signaling up-regulates expression of CD133 and promotes HCC progression. STAT3 activated by IL-6 rapidly bound to CD133 promoter and increased protein levels of CD133 in HCC cells. Reversely, in hypoxic conditions, RNA interference silencing of STAT3 resulted in decrease of CD133 levels, even in the presence of IL-6, with a concomitant decrease of hypoxia-inducible factor 1 alpha (HIF-1α) expression. Active STAT3 interacted with nuclear factor kappa B (NF-κB) p65 subunit to positively regulate the transcription of HIF-1α providing a mechanistic explanation on how those three oncogenes work together to increase the activity of CD133 in a hypoxic liver microenvironment. Activation of STAT3 and its consequent induction of HIF-1α and CD133 expression were not observed in Toll-like receptor 4/IL-6 double-knockout mice. Long-term silencing of CD133 by a lentiviral-based approach inhibited cancer cell-cycle progression and suppressed in vivo tumorigenicity by down-regulating expression of cytokinesis-related genes, such as TACC1, ACF7, and CKAP5. We also found that sorafenib and STAT3 inhibitor nifuroxazide inhibit HCC xenograft formation by blocking activation of STAT3 and expression of CD133 and HIF-1α proteins.

Conclusion: IL-6/STAT3 signaling induces expression of CD133 through functional cooperation with NF-κB and HIF-1α during liver carcinogenesis. Targeting STAT3-mediated CD133 up-regulation may represent a novel, effective treatment by eradicating the liver tumor microenvironment.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5049669PMC
http://dx.doi.org/10.1002/hep.27968DOI Listing
October 2015

Identification of microRNAs specific for epithelial cell adhesion molecule-positive tumor cells in hepatocellular carcinoma.

Hepatology 2015 Sep 30;62(3):829-40. Epub 2015 Jun 30.

Laboratory of Human Carcinogenesis, Center for Cancer Research, National Cancer Institute, Bethesda, MD.

Unlabelled: Therapies that target cancer stem cells (CSCs) hold promise in eliminating cancer burden. However, normal stem cells are likely to be targeted owing to their similarities to CSCs. It is established that epithelial cell adhesion molecule (EpCAM) is a biomarker for normal hepatic stem cells (HpSCs), and EpCAM(+) AFP(+) hepatocellular carcinoma (HCC) cells have enriched hepatic CSCs. We sought to determine whether specific microRNAs (miRNAs) exist in hepatic CSCs that are not expressed in normal HpSCs. We performed a pair-wise comparison of the miRNA transcriptome of EpCAM(+) and corresponding EpCAM(-) cells isolated from two primary HCC specimens, as well as from two fetal livers and three healthy adult liver donors by small RNA deep sequencing. We found that miR-150, miR-155, and miR-223 were preferentially highly expressed in EpCAM(+) HCC cells, which was further validated. Their gene surrogates, identified using miRNA and messenger RNA profiling in a cohort of 292 HCC patients, were associated with patient prognosis. We further demonstrated that miR-155 was highly expressed in EpCAM(+) HCC cells, compared to corresponding EpCAM(-) HCC cells, fetal livers with enriched normal hepatic progenitors, and normal adult livers with enriched mature hepatocytes. Suppressing miR-155 resulted in a decreased EpCAM(+) fraction in HCC cells and reduced HCC cell colony formation, migration, and invasion in vitro. The reduced levels of identified miR-155 targets predicted the shortened overall survival and time to recurrence of HCC patients.

Conclusion: miR-155 is highly elevated in EpCAM(+) HCC cells and might serve as a molecular target to eradicate the EpCAM(+) CSC population in human HCCs.
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http://dx.doi.org/10.1002/hep.27886DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4549211PMC
September 2015

Curcumin effectively inhibits oncogenic NF-κB signaling and restrains stemness features in liver cancer.

J Hepatol 2015 Sep 1;63(3):661-9. Epub 2015 May 1.

Laboratory of Experimental Carcinogenesis, National Cancer Institute, NIH, Bethesda, USA.

Background & Aims: The cancer stem cells (CSCs) have important therapeutic implications for multi-resistant cancers including hepatocellular carcinoma (HCC). Among the key pathways frequently activated in liver CSCs is NF-κB signaling.

Methods: We evaluated the CSCs-depleting potential of NF-κB inhibition in liver cancer achieved by the IKK inhibitor curcumin, RNAi and specific peptide SN50. The effects on CSCs were assessed by analysis of side population (SP), sphere formation and tumorigenicity. Molecular changes were determined by RT-qPCR, global gene expression microarray, EMSA, and Western blotting.

Results: HCC cell lines exposed to curcumin exhibited differential responses to curcumin and were classified as sensitive and resistant. In sensitive lines, curcumin-mediated induction of cell death was directly related to the extent of NF-κB inhibition. The treatment also led to a selective CSC-depletion as evidenced by a reduced SP size, decreased sphere formation, down-regulation of CSC markers and suppressed tumorigenicity. Similarly, NF-κB inhibition by SN50 and siRNA against p65 suppressed tumor cell growth. In contrast, curcumin-resistant cells displayed a paradoxical increase in proliferation and expression of CSC markers. Mechanistically, an important component of the CSC-depleting activity of curcumin could be attributed to a NF-κB-mediated HDAC inhibition. Co-administration of the class I/II HDAC inhibitor trichostatine sensitized resistant cells to curcumin. Further, integration of a predictive signature of curcumin sensitivity with human HCC database indicated that HCCs with poor prognosis and progenitor features are most likely to benefit from NF-κB inhibition.

Conclusions: These results demonstrate that blocking NF-κB can specifically target CSC populations and suggest a potential for combined inhibition of NF-κB and HDAC signaling for treatment of liver cancer patients with poor prognosis.
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http://dx.doi.org/10.1016/j.jhep.2015.04.018DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4543531PMC
September 2015

Expression of stanniocalcin 1 in thyroid side population cells and thyroid cancer cells.

Thyroid 2015 Apr 23;25(4):425-36. Epub 2015 Mar 23.

1 Laboratory of Metabolism, National Cancer Institute, National Institutes of Health , Bethesda, Maryland.

Background: Mouse thyroid side population (SP) cells consist of a minor population of mouse thyroid cells that may have multipotent thyroid stem cell characteristics. However the nature of thyroid SP cells remains elusive, particularly in relation to thyroid cancer. Stanniocalcin (STC) 1 and 2 are secreted glycoproteins known to regulate serum calcium and phosphate homeostasis. In recent years, the relationship of STC1/2 expression to cancer has been described in various tissues.

Method: Microarray analysis was carried out to determine genes up- and down-regulated in thyroid SP cells as compared with non-SP cells. Among genes up-regulated, stanniocalcin 1 (STC1) was chosen for study because of its expression in various thyroid cells by Western blotting and immunohistochemistry.

Results: Gene expression analysis revealed that genes known to be highly expressed in cancer cells and/or involved in cancer invasion/metastasis were markedly up-regulated in SP cells from both intact as well as partial thyroidectomized thyroids. Among these genes, expression of STC1 was found in five human thyroid carcinoma-derived cell lines as revealed by analysis of mRNA and protein, and its expression was inversely correlated with the differentiation status of the cells. Immunohistochemical analysis demonstrated higher expression of STC1 in the thyroid tumor cell line and thyroid tumor tissues from humans and mice.

Conclusion: These results suggest that SP cells contain a population of cells that express genes also highly expressed in cancer cells including Stc1, which warrants further study on the role of SP cells and/or STC1 expression in thyroid cancer.
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http://dx.doi.org/10.1089/thy.2014.0464DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4390205PMC
April 2015

Genomic predictors for recurrence patterns of hepatocellular carcinoma: model derivation and validation.

PLoS Med 2014 Dec 23;11(12):e1001770. Epub 2014 Dec 23.

Department of Systems Biology, Division of Cancer Medicine, The University of Texas MD Anderson Cancer Center, Houston, Texas, United States of America; Kleberg Center for Molecular Markers, Division of Cancer Medicine, The University of Texas MD Anderson Cancer Center, Houston, Texas, United States of America; Department of Biochemistry and Molecular Biology, Medical Research Center and Biomedical Science Institute, School of Medicine, Kyung Hee University, Seoul, Korea.

Background: Typically observed at 2 y after surgical resection, late recurrence is a major challenge in the management of hepatocellular carcinoma (HCC). We aimed to develop a genomic predictor that can identify patients at high risk for late recurrence and assess its clinical implications.

Methods And Findings: Systematic analysis of gene expression data from human liver undergoing hepatic injury and regeneration revealed a 233-gene signature that was significantly associated with late recurrence of HCC. Using this signature, we developed a prognostic predictor that can identify patients at high risk of late recurrence, and tested and validated the robustness of the predictor in patients (n = 396) who underwent surgery between 1990 and 2011 at four centers (210 recurrences during a median of 3.7 y of follow-up). In multivariate analysis, this signature was the strongest risk factor for late recurrence (hazard ratio, 2.2; 95% confidence interval, 1.3-3.7; p = 0.002). In contrast, our previously developed tumor-derived 65-gene risk score was significantly associated with early recurrence (p = 0.005) but not with late recurrence (p = 0.7). In multivariate analysis, the 65-gene risk score was the strongest risk factor for very early recurrence (<1 y after surgical resection) (hazard ratio, 1.7; 95% confidence interval, 1.1-2.6; p = 0.01). The potential significance of STAT3 activation in late recurrence was predicted by gene network analysis and validated later. We also developed and validated 4- and 20-gene predictors from the full 233-gene predictor. The main limitation of the study is that most of the patients in our study were hepatitis B virus-positive. Further investigations are needed to test our prediction models in patients with different etiologies of HCC, such as hepatitis C virus.

Conclusions: Two independently developed predictors reflected well the differences between early and late recurrence of HCC at the molecular level and provided new biomarkers for risk stratification. Please see later in the article for the Editors' Summary.
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http://dx.doi.org/10.1371/journal.pmed.1001770DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4275163PMC
December 2014

The transcription factor GTF2IRD1 regulates the topology and function of photoreceptors by modulating photoreceptor gene expression across the retina.

J Neurosci 2014 Nov;34(46):15356-68

Department of Ophthalmology, Wilmer Institute, Johns Hopkins University School of Medicine, Baltimore, Maryland 21231, Departments of Molecular Biology and Genetics, Neuroscience, Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland 21231, and Institut de la Vision, University Pierre and Marie Curie, Paris 75012, France

The mechanisms that specify photoreceptor cell-fate determination, especially as regards to short-wave-sensitive (S) versus medium-wave-sensitive (M) cone identity, and maintain their nature and function, are not fully understood. Here we report the importance of general transcription factor II-I repeat domain-containing protein 1 (GTF2IRD1) in maintaining M cone cell identity and function as well as rod function. In the mouse, GTF2IRD1 is expressed in cell-fate determined photoreceptors at postnatal day 10. GTF2IRD1 binds to enhancer and promoter regions in the mouse rhodopsin, M- and S-opsin genes, but regulates their expression differentially. Through interaction with the transcription factors CRX and thyroid hormone receptor β 2, it enhances M-opsin expression, whereas it suppresses S-opsin expression; and with CRX and NRL, it enhances rhodopsin expression. In an apparent paradox, although GTF2IRD1 is widely expressed in multiple cell types across the retina, knock-out of GTF2IRD1 alters the retinal expression of only a limited number of annotated genes. Interestingly, however, the null mutation leads to altered topology of cone opsin expression in the retina, with aberrant S-opsin overexpression and M-opsin underexpression in M cones. Gtf2ird1-null mice also demonstrate abnormal M cone and rod electrophysiological responses. These findings suggest an important role for GTF2IRD1 in regulating the level and topology of rod and cone gene expression, and in maintaining normal retinal function.
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http://dx.doi.org/10.1523/JNEUROSCI.2089-14.2014DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4228138PMC
November 2014

Engrafted human stem cell-derived hepatocytes establish an infectious HCV murine model.

J Clin Invest 2014 Nov 8;124(11):4953-64. Epub 2014 Oct 8.

The demonstrated ability to differentiate both human embryonic stem cells (hESCs) and patient-derived induced pluripotent stem cells (hiPSCs) into hepatocyte-like cells (HLCs) holds great promise for both regenerative medicine and liver disease research. Here, we determined that, despite an immature phenotype, differentiated HLCs are permissive to hepatitis C virus (HCV) infection and mount an interferon response to HCV infection in vitro. HLCs differentiated from hESCs and hiPSCs could be engrafted in the liver parenchyma of immune-deficient transgenic mice carrying the urokinase-type plasminogen activator gene driven by the major urinary protein promoter. The HLCs were maintained for more than 3 months in the livers of chimeric mice, in which they underwent further maturation and proliferation. These engrafted and expanded human HLCs were permissive to in vivo infection with HCV-positive sera and supported long-term infection of multiple HCV genotypes. Our study demonstrates efficient engraftment and in vivo HCV infection of human stem cell-derived hepatocytes and provides a model to study chronic HCV infection in patient-derived hepatocytes, action of antiviral therapies, and the biology of HCV infection.
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http://dx.doi.org/10.1172/JCI75456DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4347235PMC
November 2014

The biological and clinical challenge of liver cancer heterogeneity.

Hepat Oncol 2014 Oct 11;1(4):349-353. Epub 2014 Dec 11.

Laboratory of Experimental Carcinogenesis, Center for Cancer Research, National Cancer Institute, Bethesda, MD 20892, USA.

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http://dx.doi.org/10.2217/hep.14.18DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6096446PMC
October 2014

MYC activates stem-like cell potential in hepatocarcinoma by a p53-dependent mechanism.

Cancer Res 2014 Oct 4;74(20):5903-13. Epub 2014 Sep 4.

Laboratory of Experimental Carcinogenesis, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, Maryland.

Activation of c-MYC is an oncogenic hallmark of many cancers, including liver cancer, and is associated with a variety of adverse prognostic characteristics. Despite a causative role during malignant transformation and progression in hepatocarcinogenesis, consequences of c-MYC activation for the biology of hepatic cancer stem cells (CSC) are undefined. Here, distinct levels of c-MYC overexpression were established by using two dose-dependent tetracycline-inducible systems in four hepatoma cell lines with different p53 mutational status. The CSCs were evaluated using side population (SP) approach as well as standard in vitro and in vivo assays. Functional repression of p53 was achieved by lentiviral shRNA transduction. The results show that c-MYC expression levels have a differential impact on liver CSC characteristics. At low levels, c-MYC activation led to increased proliferation and enhanced CSC properties including activation of reprogramming transcription factors and CSC marker expression (e.g., NANOG, OCT4, and EpCAM), expansion of SP, and acceleration of tumor growth upon subcutaneous transplantation into immunocompromised mice. However, when exceeding a threshold level, c-MYC induced a proapoptotic program and loss of CSC potential both in vitro and in vivo. Mechanistically, c-MYC-induced self-renewal capacity of liver cancer cells was exerted in a p53-dependent manner. Low c-MYC activation increased spheroid formation in p53-deficient tumor cells, whereas p53-dependent effects were blunted in the absence of c-MYC overexpression. Together, our results confirm the role of c-MYC as a master regulator during hepatocarcinogenesis and establish a new gatekeeper role for p53 in repressing c-MYC-induced CSC phenotype in liver cancer cells.
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http://dx.doi.org/10.1158/0008-5472.CAN-14-0527DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4199878PMC
October 2014
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