Modeling pathogenesis of primary liver cancer in lineage-specific mouse cell types

Liver Progenitors and Adult Cell Plasticity in Hepatic Injury and Repair: Knowns and Unknowns

The liver is a complex organ performing numerous vital physiological functions. For that reason, it possesses immense regenerative potential. The capacity for repair is largely attributable to the ability of its differentiated epithelial cells, hepatocytes and biliary epithelial cells, to proliferate after injury. However, in cases of extreme acute injury or prolonged chronic insult, the liver may fail to regenerate or do so suboptimally. This often results in life-threatening end-stage liver disease for which liver transplantation is the only effective treatment. In many forms of liver injury, bipotent liver progenitor cells are theorized to be activated as an additional tier of liver repair. However, the existence, origin, fate, activation, and contribution to regeneration of liver progenitor cells is hotly debated, especially since hepatocytes and biliary epithelial cells themselves may serve as facultative stem cells for one another during severe liver injury. Here, we discuss the evidence both supporting and refuting the existence of liver progenitor cells in a variety of experimental models. We also debate the validity of developing therapies harnessing the capabilities of these cells as potential treatments for patients with severe and chronic liver diseases.

Genetic Mouse Models as In Vivo Tools for Cholangiocarcinoma Research

Cholangiocarcinoma (CCA) is a genetically and histologically complex disease with a highly dismal prognosis. A deeper understanding of the underlying cellular and molecular mechanisms of human CCA will increase our current knowledge of the disease and expedite the eventual development of novel therapeutic strategies for this fatal cancer. This endeavor is effectively supported by genetic mouse models, which serve as sophisticated tools to systematically investigate CCA pathobiology and treatment response. These in vivo models feature many of the genetic alterations found in humans, recapitulate multiple hallmarks of cholangiocarcinogenesis (encompassing cell transformation, preneoplastic lesions, established tumors and metastatic disease) and provide an ideal experimental setting to study the interplay between tumor cells and the surrounding stroma. This review is intended to serve as a compendium of CCA mouse models, including traditional transgenic models but also genetically flexible approaches based on either the direct introduction of DNA into liver cells or transplantation of pre-malignant cells, and is meant as a resource for CCA researchers to aid in the selection of the most appropriate in vivo model system.

In vitro transformation of primary human hepatocytes: Epigenetic changes and stemness properties

Human hepatocarcinogenesis is a complex process with many unresolved issues, including the cell of origin (differentiated and/or progenitor/stem cells) and the initial steps leading to tumor development. With the aim of providing new tools for studying hepatocellular carcinoma initiation and progression, we developed an innovative model based on primary human hepatocytes (PHHs) lentivirus-transduced with SV40LT+ST, HRASV12 with or without hTERT. The differentiation status of these transduced-PHHs was characterized by RNA sequencing (including lncRNAs), and the expression of some differentiation markers confirmed by RT-qPCR and immunofluorescence. In addition, their transformation capacity was assessed by colony formation in soft agar and tumorigenicity evaluated in immune-deficient mice. The co-expression of SV40LT+ST and HRASV12 in PHHs, in association or not with hTERT, led to the emergence of transformed clones. These clones exhibited a poorly differentiated cell phenotype with expression of stemness and mesenchymal-epithelial transition markers and gave rise to cancer stem cell subpopulations. In vivo, they resulted in poorly differentiated hepatocellular carcinomas with a reactivation of endogenous hTERT. These experiments demonstrate for the first time that non-cycling human mature hepatocytes can be permissive to in vitro transformation. This cellular tool provides the first comprehensive in vitro model for identifying genetic/epigenetic changes driving human hepatocarcinogenesis.

Direct conversion of human fibroblast to hepatocytes using a single inducible polycistronic vector

BACKGROUND

Human fibroblasts can be reprogrammed into induced hepatocyte-like cells through the expression of a set of transcription factors. Although the generation of induced hepatocyte-like cells by HNF4A, HNF1A, and FOXA3 expression has proven to be a robust experimental strategy, using multiple lentivirus results in a highly variable heterogeneous population.

METHODS

We designed and implemented a novel approach based on the delivery of reprogramming factors and green fluorescent protein in a single doxycycline-inducible lentiviral vector using 2A self-cleaving peptides.

RESULTS

Fibroblasts infected with the lentiviral vector can be amplified in basic fibroblast culture media in the absence of doxycycline without induction of hepatic genes. Upon switching to hepatic maturation media containing doxycycline, cells stop proliferating, activate hepatic gene transcription, and perform metabolic functions characteristic of hepatocytes.

CONCLUSION

Our strategy can generate an unlimited source of homogeneously induced hepatocyte-like cells from different genetic background donors, capable of performing typical hepatic functions suitable for drug research and other in vitro applications.

IGF2 mRNA Binding Protein 2 Transgenic Mice Are More Prone to Develop a Ductular Reaction and to Progress Toward Cirrhosis

The insulin-like growth factor 2 (IGF2) mRNA binding proteins (IMPs/IGF2BPs) IMP1 and 3 are regarded as oncofetal proteins, whereas the hepatic IMP2 expression in adults is controversially discussed. The splice variant IMP2-2/p62 promotes steatohepatitis and hepatocellular carcinoma. Aim of this study was to clarify whether IMP2 is expressed in the adult liver and influences progression toward cirrhosis. IMP2 was expressed at higher levels in embryonic compared to adult tissues as quantified in embryonic, newborn, and adult C57BL/6J mouse livers and suggested by analysis of publicly available human data. In an IMP2-2 transgenic mouse model microarray and qPCR analyses revealed increased expression of liver progenitor cell (LPC) markers Bex1, Prom1, Spp1, and Cdh1 indicating a de-differentiated liver cell phenotype. Induction of these LPC markers was confirmed in human cirrhotic tissue datasets. The LPC marker SPP1 has been described to play a major role in fibrogenesis. Thus, DNA methylation was investigated in order to decipher the regulatory mechanism of Spp1 induction. In IMP2-2 transgenic mouse livers single CpG sites were differentially methylated, as quantified by amplicon sequencing, whereas human HCC samples of a human publicly available dataset showed promoter hypomethylation. In order to study the impact of IMP2 on fibrogenesis in the context of steatohepatitis wild-type or IMP2-2 transgenic mice were fed either a methionine-choline deficient (MCD) or a control diet for 2-12 weeks. MCD-fed IMP2-2 transgenic mice showed a higher incidence of ductular reaction (DR), accompanied by hepatic stellate cell activation, extracellular matrix (ECM) deposition, and induction of the LPC markers Spp1, Cdh1, and Afp suggesting the occurrence of de-differentiated cells in transgenic livers. In human cirrhotic samples IMP2 overexpression correlated with LPC marker and ECM component expression. Progression of liver disease was induced by combined MCD and diethylnitrosamine (DEN) treatment. Combined MCD-DEN treatment resulted in shorter survival of IMP2-2 transgenic compared to wild-type mice. Only IMP2-2 transgenic livers progressed to cirrhosis, which was accompanied by strong DR. In conclusion, IMP2 is an oncofetal protein in the liver that promotes DR characterized by de-differentiated cells toward steatohepatitis-associated cirrhosis development with poor survival.

Molecular and histological correlations in liver cancer

Hepatocellular carcinoma (HCC) is a highly heterogeneous cancer, both at the molecular and histological level. High-throughput sequencing and gene expression profiling have identified distinct transcriptomic subclasses and numerous recurrent genetic alterations; several HCC subtypes characterised by histological features have also been identified. HCC phenotype appears to be closely related to particular gene mutations, tumour subgroups and/or oncogenic pathways. Non-proliferative tumours display a well-differentiated phenotype. Among this molecular subgroup, CTNNB1-mutated HCCs constitute a homogeneous subtype, exhibiting cholestasis and microtrabecular and pseudoglandular architectural patterns. Another non-proliferative subtype has a gene expression pattern similar to that of mature hepatocytes (G4) and displays a steatohepatitic phenotype. In contrast, proliferative HCCs are most often poorly differentiated, and notably include tumours with progenitor features. A novel morphological variant of proliferative HCC - designated "macrotrabecular-massive" - was recently shown to be associated with angiogenesis activation and poor prognosis. Altogether, these findings may help to translate our knowledge of HCC biology into clinical practice, resulting in improved precision medicine for patients with this highly aggressive malignancy. This manuscript reviews the most recent data in this exciting field, discussing future directions and challenges.

Hippo signaling and epithelial cell plasticity in mammalian liver development, homeostasis, injury and disease

A traditional view of cellular differentiation is unidirectional: progenitor cells adopt specific fates in response to environmental cues resulting in deployment of cell-specific gene expression programs and acquisition of unique differentiated cellular properties such as production of structural and functional proteins that define individual cell types. In both development and in tissue repair stem and progenitor cells are thought to both self-renew to maintain the pool of precursors and to expand to give rise to transient amplifying and differentiated cell types. Recently, however, it has become appreciated that differentiated cell types can be reprogrammed to adopt progenitor and stem cell properties. In the case of epithelial cells in the mammalian liver, hepatocytes and biliary epithelial cells there is a significant degree of plasticity between these lineages that has been implicated in mechanisms of tissue repair and in liver pathologies such as cancer. Recent studies have highlighted the role of Hippo signaling, an emerging growth control and tumor suppressor pathway, in regulating epithelial cell plasticity in the mammalian liver and in this review, the role of cellular plasticity and Hippo signaling in regulating normal and abnormal tissue responses in the mammalian liver will be discussed.

Crossing borders: A systematic review with quantitative analysis of genetic mutations of carcinomas of the biliary tract

Biliary tract carcinoma (BTC) comprises gallbladder and intra-/extrahepatic cholangiocarcinoma (GBC, ICC, EHC), which are currently classified by anatomical origin. Better understanding of the mutational profile of BTCs might refine classification and improve treatment. We performed a systematic review of studies reporting on mutational profiling of BTC. We included articles reporting on whole-exome/whole-genome-sequencing (WES/WGS) and targeted sequencing (TS) of BTC, published between 2000-2017. Pooled mutation proportions were calculated, stratified by anatomical region and sequencing technique. A total of 25 studies with 1806 patients were included. Overall, TP53 was the most commonly mutated gene in BTC. GBC was associated with mutations in PFKFB3, PLXN2 and PGAP1. Mutations in IDH1, IDH2 and FGFR fusions almost exclusively occurred in ICC patients. Mutations in APC, GNAS and TGFBR2 occurred exclusively in EHC patients. In conclusion, subtypes of BTCs exhibit minor differences in mutational profile, which is likely influenced by the cell of origin.

Experimental models to unravel the molecular pathogenesis, cell of origin and stem cell properties of cholangiocarcinoma

Human cholangiocarcinoma (CCA) is an aggressive tumour entity arising from the biliary tree, whose molecular pathogenesis remains largely undeciphered. Over the last decade, the advent of high-throughput and cell-based techniques has significantly increased our knowledge on the molecular mechanisms underlying this disease while, at the same time, unravelling CCA complexity. In particular, it becomes clear that CCA displays pronounced inter- and intratumoural heterogeneity, which is presumably the consequence of the interplay between distinct tissues and cells of origin, the underlying diseases, and the associated molecular alterations. To better characterize these events and to design novel and more effective therapeutic strategies, a number of CCA experimental and preclinical models have been developed and are currently generated. This review summarizes the current knowledge and understanding of these models, critically underlining their translational usefulness and limitations. Furthermore, this review aims to provide a comprehensive overview on cells of origin, cancers stem cells and their dynamic interplay within CCA tissue.

Murine Liver Organoids as a Genetically Flexible System to Study Liver Cancer In Vivo and In Vitro

The rising incidence of cholangiocarcinoma (CCA) coupled with a low 5‐year survival rate that remains below 10% delineates the urgent need for more effective treatment strategies. Although several recent studies provided detailed information on the genetic landscape of this fatal malignancy, versatile model systems to functionally dissect the immediate clinical relevance of the identified genetic alterations are still missing. To enhance our understanding of CCA pathophysiology and facilitate rapid functional annotation of putative CCA driver and tumor maintenance genes, we developed a tractable murine CCA model by combining the cyclization recombination (Cre)‐lox system, RNA interference, and clustered regularly interspaced short palindromic repeats/CRISPR associated protein 9 (CRISPR/Cas9) technology with liver organoids, followed by subsequent transplantation into immunocompetent, syngeneic mice. Histologically, resulting tumors displayed cytokeratin 19–positive ductal structures surrounded by a desmoplastic stroma—hallmark features of human CCAs. Despite their initial biliary phenotype in vitro, organoids retained the plasticity to induce a broader differentiation spectrum of primary liver cancers following transplantation into recipient mice, depending on their genetic context. Thus, the organoid system combines the advantage of using nontransformed, premalignant cells to recapitulate liver tumorigenesis as a multistep process, with the advantage of a reproducible and expandable cell culture system that abrogates the need for recurrent isolations of primary cells. Conclusion: Genetically modified liver organoids are able to transform into histologically accurate CCAs. Depending on the oncogenic context, they are also able to give rise to liver cancers that show features of hepatocellular carcinomas. The model can be used to functionally explore candidate cancer genes of primary liver cancers in immunocompetent animals and evaluate novel treatment regimens.

TRIB3 Interacts With β-Catenin and TCF4 to Increase Stem Cell Features of Colorectal Cancer Stem Cells and Tumorigenesis

BACKGROUND & AIMS

Activation of Wnt signaling to β-catenin contributes to the development of colorectal cancer (CRC). Expression of tribbles pseudo-kinase 3 (TRIB3) is increased in some colorectal tumors and associated with poor outcome. We investigated whether increased TRIB3 expression promotes stem cell features of CRC cells and tumor progression by interacting with the Wnt signaling pathway.

METHODS

We performed studies with C57BL/6J-Apc^Min/J mice injected with an adeno-associated virus vector that expresses a small hairpin RNA against Trib3 mRNA (Apc^Min/J-Trib3^KD) or a control vector (Apc^Min/J-Ctrl). We created BALB/c mice that overexpress TRIB3 from an adeno-associated virus vector and mice with small hairpin RNA-mediated knockdown of β-catenin. The mice were given azoxymethane followed by dextran sodium sulfate to induce colitis-associated cancer. Intestinal tissues were collected and analyzed by histology, gene expression profiling, immunohistochemistry, and immunofluorescence. Leucine-rich repeat-containing G-protein-coupled receptor 5 (LGR5)-positive (LGR5^Pos) and LGR5-negative (LGR5^Neg) HCT-8 CRC cells, with or without knockdown or transgenic expression of TRIB3, were sorted and analyzed in sphere-formation assays. We derived organoids from human and mouse colorectal tumors to analyze the function of TRIB3 and test the effect of a peptide inhibitor. Wnt signaling to β-catenin was analyzed in dual luciferase reporter, chromatin precipitation, immunofluorescence, and immunoblot assays. Proteins that interact with TRIB3 were identified by immunoprecipitation. CRC cell lines were grown in nude mice as xenograft tumors.

RESULTS

At 10 weeks of age, more than half the Apc^Min/J-Ctrl mice developed intestinal high-grade epithelial neoplasia, whereas Apc^Min/J-Trib3^KD mice had no intestinal polyps and normal histology. Colon tissues from Apc^Min/J-Trib3^KD mice expressed lower levels of genes regulated by β-catenin and genes associated with cancer stem cells. Mice with overexpression of Trib3 developed more tumors after administration of azoxymethane and dextran sodium sulfate than BALB/c mice. Mice with knockdown of β-catenin had a lower tumor burden after administration of azoxymethane and dextran sodium sulfate, regardless of Trib3 overexpression. Intestinal tissues from mice with overexpression of Trib3 and knockdown of β-catenin did not have activation of Wnt signaling or expression of genes regulated by β-catenin. LGR5^Pos cells sorted from HCT-8 cells expressed higher levels of TRIB3 than LGR5^Neg cells. CRC cells that overexpressed TRIB3 had higher levels of transcription by β-catenin and formed larger spheroids than control CRC cells; knockdown of β-catenin prevented the larger organoid size caused by TRIB3 overexpression. TRIB3 interacted physically with β-catenin and transcription factor 4 (TCF4). TRIB3 overexpression increased, and TRIB3 knockdown decreased, recruitment of TCF4 and β-catenin to the promoter region of genes regulated by Wnt. Activated β-catenin increased expression of TRIB3, indicating a positive-feedback loop. A peptide (P2-T3A6) that bound β-catenin disrupted its interaction with TRIB3 and TCF4. In primary CRC cells and HCT-8 cells, P2-T3A6 decreased expression of genes regulated by β-catenin and genes associated with cancer stem cells and decreased cell viability and migration. Injection of C57BL/6J-Apc^Min/J mice with P2-T3A6 decreased the number and size of tumor nodules and colon expression of genes regulated by β-catenin. P2-T3A6 increased 5-fluorouracil-induced death of CRC cells and survival times of mice with xenograft tumors.

CONCLUSION

TRIB3 interacts with β-catenin and TCF4 in intestine cells to increase expression of genes associated with cancer stem cells. Knockdown of TRIB3 decreases colon neoplasia in mice, migration of CRC cells, and their growth as xenograft tumors in mice. Strategies to block TRIB3 activity might be developed for treatment of CRC.

Heterogeneity of Hepatic Cancer Stem Cells

Hepatocellular carcinoma (HCC) is one of the most common cancers with high mortality rate. It is a heterogeneous cancer with diverse inter- and intra-heterogeneity, also in terms of histology, prognosis, and molecular profiles. A rapidly growing evidence has demonstrated that some HCCs, if not all, were caused by the activation of the cancer stem cells (CSC), a small population within the cancer that is responsible for the initiation and maintenance of cancer growth. Until now, various populations of hepatic CSC with more than ten different phenotypical protein markers, such as CD133, CD90, EpCAM, CD24, and CD13, have been identified and validated in xenotransplantation models. They are associated with risk factors, prognosis, chemo-resistance, and metastasis. This chapter summarizes available data on different hepatic CSC markers for the development of potential future therapy.

Activation of hepatic stem cells compartment during hepatocarcinogenesis in a HBsAg HBV-transgenic mouse model

Chronic infection of Hepatitis B Virus (HBV) is one of the highest risk factors of hepatocellular carcinoma (HCC). The accumulation of HBV surface antigen (HBsAg) into hepatocytes induces inflammation and oxidative stress, impairing their replicative ability and allowing the activation of the hepatic stem cells (SC) compartment. This study aimed to understand the involvement of SC during hepatocarcinogenesis in HBsAg-related liver damage, from early injury until HCC. HBsAg-transgenic (TG) and wild type (WT) mouse were followed at several stages of the liver damage: inflammation, early hepatocytes damage, dysplasia, and HCC. Serum transaminases, liver histology, and diagnostic data were collected. The expressions of SC and cancer stem cells (CSC) markers was analyzed by RT-qPCR, immunohistochemistry and Western blot. Starting from 3 months, TG animals showed a progressive liver damage characterized by transaminases increase. The up-regulations of SCs markers Cd34 and Sca-1 started from the beginning of the inflammatory stage while progressive increase of Krt19 and Sox9 and CSCs markers Epcam and Cd133 from early hepatic injury. The expressions of Cd133, Cd34, and Afp were significantly higher in HCC compared to paired non-HCC tissue, in contrast to Epcam and Krt19. Western blot and IHC confirmed the positivity of Cd34 and Cd133 in small cells subpopulation.

How Rap and its GEFs control liver physiology and cancer development. C3G alterations in human hepatocarcinoma

Rap proteins regulate liver physiopathology. For example, Rap2B promotes hepatocarcinoma (HCC) growth, while Rap1 might play a dual role. The RapGEF, Epac1, activates Rap upon cAMP binding, regulating metabolism, survival, and liver regeneration. A liver specific Epac2 isoform lacking cAMP-binding domain also activates Rap1, promoting fibrosis in alcoholic liver disease. C3G (RapGEF1) is also present in the liver, but mainly as shorter isoforms. Its function in the liver remains unknown. Information from different public genetic databases revealed that C3G mRNA levels increase in HCC, although they decrease in metastatic stages. In addition, several mutations in RapGEF1 gene are present, associated with a reduced patient survival. Based on this, C3G might represent a new HCC diagnostic and prognostic marker, and a therapeutic target.

Hepatitis B Virus-Associated Hepatocellular Carcinoma and Hepatic Cancer Stem Cells

Chronic Hepatitis B Virus (HBV) infection is linked to hepatocellular carcinoma (HCC) pathogenesis. Despite the availability of a HBV vaccine, current treatments for HCC are inadequate. Globally, 257 million people are chronic HBV carriers, and children born from HBV-infected mothers become chronic carriers, destined to develop liver cancer. Thus, new therapeutic approaches are needed to target essential pathways involved in HCC pathogenesis. Accumulating evidence supports existence of hepatic cancer stem cells (hCSCs), which contribute to chemotherapy resistance and cancer recurrence after treatment or surgery. Understanding how hCSCs form will enable development of therapeutic strategies to prevent their formation. Recent studies have identified an epigenetic mechanism involving the downregulation of the chromatin modifying Polycomb Repressive Complex 2 (PRC2) during HBV infection, which results in re-expression of hCSC marker genes in infected hepatocytes and HBV-associated liver tumors. However, the genesis of hCSCs requires, in addition to the expression of hCSC markers cellular changes, rewiring of metabolism, cell survival, escape from programmed cell death, and immune evasion. How these changes occur in chronically HBV-infected hepatocytes is not yet understood. In this review, we will present the basics about HBV infection and hepatocarcinogenesis. Next, we will discuss studies describing the mutational landscape of liver cancers and how epigenetic mechanisms likely orchestrate cellular reprograming of hepatocytes to enable formation of hCSCs.

Stem-like plasticity and heterogeneity of circulating tumor cells: current status and prospect challenges in liver cancer

Poor prognosis and high recurrence remain leading causes of primary liver cancerassociated mortality. The spread of circulating tumor cells (CTCs) in the blood plays a major role in the initiation of metastasis and tumor recurrence after surgery. Nevertheless, only a subset of CTCs can survive, migrate to distant sites and establish secondary tumors. Consistent with cancer stem cell (CSC) hypothesis, stem-like CTCs might represent a potential source for cancer relapse and distant metastasis. Thus, identification of stem-like metastasis-initiating CTC-subset may provide useful clinically prognostic information. This review will emphasize the most relevant findings of CTCs in the context of stem-like biology associated to liver carcinogenesis. In this view, the emerging field of stem-like CTCs may deliver substantial contribution in liver cancer field in order to move to personalized approaches for diagnosis, prognosis and therapy.

Stem/progenitor cells in pituitary organ homeostasis and tumourigenesis

Evidence for the presence of pituitary gland stem cells has been provided over the last decade using a combination of approaches including in vitro clonogenicity assays, flow cytometric side population analysis, immunohistochemical analysis and genetic approaches. These cells have been demonstrated to be able to self-renew and undergo multipotent differentiation to give rise to all hormonal lineages of the anterior pituitary. Furthermore, evidence exists for their contribution to regeneration of the organ and plastic responses to changing physiological demand. Recently, stem-like cells have been isolated from pituitary neoplasms raising the possibility that a cytological hierarchy exists, in keeping with the cancer stem cell paradigm. In this manuscript, we review the evidence for the existence of pituitary stem cells, their role in maintaining organ homeostasis and the regulation of their differentiation. Furthermore, we explore the emerging concept of stem cells in pituitary tumours and their potential roles in these diseases.

Emergence of Intrahepatic Cholangiocarcinoma: How High-Throughput Technologies Expedite the Solutions for a Rare Cancer Type

Intrahepatic cholangiocarcinoma (ICC) is the cancer of the intrahepatic bile ducts, and together with hepatocellular carcinoma (HCC), constitute the majority of primary liver cancers. ICC is a rare disorder as its overall incidence is < 1/100,000 in the United States and Europe. However, it shows much higher incidence in particular geographical regions, such as northeastern Thailand, where liver fluke infection is the most common risk factor of ICC. Since the early stages of ICC are often asymptomatic, the patients are usually diagnosed at advanced stages with no effective treatments available, leading to the high mortality rate. In addition, unclear genetic mechanisms, heterogeneous nature, and various etiologies complicate the development of new efficient treatments. Recently, a number of studies have employed high-throughput approaches, including next-generation sequencing and mass spectrometry, in order to understand ICC in different biological aspects. In general, the majority of recurrent genetic alterations identified in ICC are enriched in known tumor suppressor genes and oncogenes, such as mutations in TP53, KRAS, BAP1, ARID1A, IDH1, IDH2, and novel FGFR2 fusion genes. Yet, there are no major driver genes with immediate clinical solutions characterized. Interestingly, recent studies utilized multi-omics data to classify ICC into two main subgroups, one with immune response genes as the main driving factor, while another is enriched with driver mutations in the genes associated with epigenetic regulations, such as IDH1 and IDH2. The two subgroups also show different hypermethylation patterns in the promoter regions. Additionally, the immune response induced by host-pathogen interactions, i.e., liver fluke infection, may further stimulate tumor growth through alterations of the tumor microenvironment. For in-depth functional studies, although many ICC cell lines have been globally established, these homogeneous cell lines may not fully explain the highly heterogeneous genetic contents of this disorder. Therefore, the advent of patient-derived xenograft and 3D patient-derived organoids as new disease models together with the understanding of evolution and genetic alterations of tumor cells at the single-cell resolution will likely become the main focus to fill the current translational research gaps of ICC in the future.

Look into hepatic progenitor cell associated trait: Histological heterogeneity of hepatitis B-related combined hepatocellular-cholangiocarcinoma

Combined hepatocellular-cholangiocarcinoma (CHC) is a mixed tumor containing elements of both hepatocellular carcinoma (HCC) and cholangiocarcinoma (CC). Its remarkable histological heterogeneity has been linked to putative hepatic progenitor cell (HPC) origin. However, detailed histological or phenotypic description is rarely documented. In the present study, we reassessed 68 cases previously diagnosed as hepatitis B-related CHCs by immunohistochemistry and double-fluorescence immunostaining, focusing on HPC associated phenotypic observation of intermediate area of the tumor. It was found that tumor cells showed remarkable heterogeneity in intermediate area. Tumor cells with intermediate morphology between hepatocytes and cholangiocytes were oval-shaped and small with scant cytoplasm and hyperchromatic nuclei, arranging in solid nests mostly. By Keratin 7 (K7) staining, it appeared that the nests of tumor cells represented a maturation process from the undifferentiated small cells to mature hepatocytes through the "transitional" cells. Then, these small cells were further confirmed with intermediate phenotype as HPC by exploring immature hepatocellular marker and HPC/biliary markers co-localization. In conclusion, the HPC associated trait in CHC can be interpreted by HPC origin or gain of "stemness" by dedifferentiation. It is still too soon to give a final word that it is innate or acquired signature of HPC associated trait in CHC.

Acquisition of Cholangiocarcinoma Traits during Advanced Hepatocellular Carcinoma Development in Mice

Past studies have identified hepatic tumors with mixed hepatocellular carcinoma (HCC) and cholangiocarcinoma (CC) characteristics that have a more aggressive behavior and a poorer prognosis than classic HCC. Whether this pathologic heterogeneity is due to a cell of origin of bipotent liver progenitors or the plasticity of cellular constituents comprising these tumors remains debated. In this study, we investigated the potential acquisition of CC-like traits during advanced development of HCC in mice. Primary and rare high-grade HCC developed in a genetic mouse model. A mouse model of highly efficient HCC invasion and metastasis by orthotopic transplantation of liver cancer organoids propagated from primary tumors in the genetic model was further developed. Invasive/metastatic tumors developed in both models closely recapitulated advanced human HCC and displayed a striking acquisition of CC-related pathologic and molecular features, which was absent in the primary HCC tumors. Our study directly demonstrates the pathologic evolution of HCC during advanced tumor development, providing the first evidence that tumors with mixed HCC and CC features, or at least a subset of these tumors, represent a more advanced developmental stage of HCC. Finally, liver cancer organoid-generated high-grade tumors exhibited significantly increased extracellular vesicle secretion, suggesting that identifying tumor-specific extracellular vesicle proteins in plasma may be a promising tool for liver cancer detection.

Chronic inflammation-elicited liver progenitor cell conversion to liver cancer stem cell with clinical significance

The substantial heterogeneity and hierarchical organization in liver cancer support the theory of liver cancer stem cells (LCSCs). However, the relationship between chronic hepatic inflammation and LCSC generation remains obscure. Here, we observed a close correlation between aggravated inflammation and liver progenitor cell (LPC) propagation in the cirrhotic liver of rats exposed to diethylnitrosamine. LPCs isolated from the rat cirrhotic liver initiated subcutaneous liver cancers in nonobese diabetic/severe combined immunodeficient mice, suggesting the malignant transformation of LPCs toward LCSCs. Interestingly, depletion of Kupffer cells in vivo attenuated the LCSC properties of transformed LPCs and suppressed cytokeratin 19/Oval cell 6-positive tumor occurrence. Conversely, LPCs cocultured with macrophages exhibited enhanced LCSC properties. We further demonstrated that macrophage-secreted tumor necrosis factor-α triggered chromosomal instability in LPCs through the deregulation of ubiquitin D and checkpoint kinase 2 and enhanced the self-renewal of LPCs through the tumor necrosis factor receptor 1/Src/signal transducer and activator of transcription 3 pathway, which synergistically contributed to the conversion of LPCs to LCSCs. Clinical investigation revealed that cytokeratin 19/Oval cell 6-positive liver cancer patients displayed a worse prognosis and exhibited superior response to sorafenib treatment.

CONCLUSION

Our results not only clarify the cellular and molecular mechanisms underlying the inflammation-mediated LCSC generation but also provide a molecular classification for the individualized treatment of liver cancer. (Hepatology 2017;66:1934-1951).

Road to stemness in hepatocellular carcinoma

Carcinogenic process has been proposed to relay on the capacity to induce local tissue damage and proliferative repair. Liver has a great regeneration capacity and currently, most studies point towards the dominant role of hepatocytes in regeneration at all levels of liver damage. The most frequent liver cancer is hepatocellular carcinoma (HCC). Historical findings originally led to the idea that the cell of origin of HCC might be a progenitor cell. However, current linage tracing studies put the progenitor hypothesis of HCC origin into question. In agreement with their dominant role in liver regeneration, mature hepatocytes are emerging as the cell of origin of HCC, although, the specific hepatocyte subpopulation of origin is yet to be determined. The relationship between the cancer cell of origin (CCO) and cancer-propagating cells, known as hepatic cancer stem cell (HCSC) is unknown. It has been challenging to identify the definitive phenotypic marker of HCSC, probably due to the existence of different cancer stem cells (CSC) subpopulations with different functions within HCC. There is a dynamic interconversion among different CSCs, and between CSC and non-CSCs. Because of that, CSC-state is currently defined as a description of a highly adaptable and dynamic intrinsic property of tumor cells, instead of a static subpopulation of a tumor. Altered conditions could trigger the gain of stemness, some of them include: EMT-MET, epigenetics, microenvironment and selective stimulus such as chemotherapy. This CSC heterogeneity and dynamism makes them out reach from therapeutic protocols directed to a single target. A further avenue of research in this line will be to uncover mechanisms that trigger this interconversion of cell populations within tumors and target it.

Proliferating EpCAM-Positive Ductal Cells in the Inflamed Liver Give Rise to Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) originates from regenerating liver cells with genetic alterations in chronically inflamed liver. Ductal cells and hepatocytes proliferate for liver regeneration, and proliferating ductal cells (PDC) derived from bile ductules have long been considered putative liver stem/progenitor cells and candidate cellular origins of HCC. The potential of PDC as tumor-originating cells, however, remains controversial in contrast to accumulating evidence that HCC originates from hepatocytes. Here, we demonstrate that PDCs expressing the established surface and cancer stem cell marker EpCAM give rise to HCC in inflamed liver. EpCAM-expressing PDCs were specifically labeled in newly developed Epcam^CreERT2 mice and traced in a chemically induced liver injury model. Stepwise accumulation of genetic alterations in EpCAM-positive cells was induced by the mutagenesis activity of activation-induced cytidine deaminase using conditional transgenic mice. Lineage-tracing experiments revealed that labeled PDC differentiated into cholangiocytes, but not into hepatocytes, in the chemically damaged liver. Nevertheless, EpCAM-positive PDC with genetic alterations gave rise to HCC after 8 months of chemical administration. PDC-derived HCC showed histologic characteristics of concomitant ductule-like structures resembling human cholangiolocellular carcinoma (CLC) and exhibited serial transitions from PDC-like CLC cells to hepatocyte-like HCC cells. The Wnt signaling pathway was specifically upregulated in the CLC components of PDC-derived HCC. Our findings provide direct experimental evidence that EpCAM-expressing PDC could be a cellular origin of HCC, suggesting the existence of stem/progenitor-derived hepatocarcinogenesis. Cancer Res; 77(22); 6131-43. ©2017 AACR.

Liver Cancer: Molecular Characterization, Clonal Evolution and Cancer Stem Cells

Liver cancer is the second most common cause of cancer-related death. The major forms of primary liver cancer are hepatocellular carcinoma (HCC) and intrahepatic cholangiocarcinoma (iCCA). Both these tumors develop against a background of cirrhotic liver, non-alcoholic fatty liver disease, chronic liver damage and fibrosis. HCC is a heterogeneous disease which usually develops within liver cirrhosis related to various etiologies: hepatitis B virus (HBV) infection (frequent in Asia and Africa), hepatitis C virus (HCV), chronic alcohol abuse, or metabolic syndrome (frequent in Western countries). In cirrhosis, hepatocarcinogenesis is a multi-step process where pre-cancerous dysplastic macronodules transform progressively into HCC. The patterns of genomic alterations observed in these tumors were recently identified and were instrumental for the identification of potential targeted therapies that could improve patient care. Liver cancer stem cells are a small subset of undifferentiated liver tumor cells, responsible for cancer initiation, metastasis, relapse and chemoresistance, enriched and isolated according to immunophenotypic and functional properties: cell surface proteins (CD133, CD90, CD44, EpCAM, OV-6, CD13, CD24, DLK1, α2δ1, ICAM-1 and CD47); the functional markers corresponding to side population, high aldehyde dehydrogenase (ALDH) activity and autofluorescence. The identification and definition of liver cancer stem cells requires both immunophenotypic and functional properties.

Integrative Genomic Analysis of Cholangiocarcinoma Identifies Distinct IDH-Mutant Molecular Profiles

Cholangiocarcinoma (CCA) is an aggressive malignancy of the bile ducts, with poor prognosis and limited treatment options. Here, we describe the integrated analysis of somatic mutations, RNA expression, copy number, and DNA methylation by The Cancer Genome Atlas, of a set of predominantly intrahepatic CCA cases, and propose a molecular classification scheme. We identified an IDH -mutant enriched subtype with distinct molecular features including low expression of chromatin modifiers, elevated expression of mitochondrial genes, and increased mitochondrial DNA copy number. Leveraging the multi-platform data, we observed that ARID1A exhibited DNA hypermethylation and decreased expression in the IDH -mutant subtype. More broadly, we found that IDH mutations are associated with an expanded histological spectrum of liver tumors with molecular features that stratify with CCA. Our studies reveal insights into the molecular pathogenesis and heterogeneity of cholangiocarcinoma and provide classification information of potential therapeutic significance.

Cancer stem cell marker glycosylation: Nature, function and significance

Glycans are essential for the maintenance of normal biological function, with alterations in glycan expression being a hallmark of cancer. Cancer stem cells (CSCs) are a subset of cells within a tumour capable of self-renewal, cellular differentiation and resistances to conventional therapies. As is the case with stem cells, marker proteins present on the cell surface are frequently used to identify and enrich CSCs, with the expression of these markers statistical correlating with the likelihood of cancer recurrence and overall patient survival. As such CSC markers are of high clinical relevance. The majority of markers currently used to identify CSC populations are glycoproteins, and although the diverse biological roles for many of these markers are known, the nature and function of the glycan moiety on these glycoproteins remains to be fully elucidated. This mini-review summarises our current knowledge regarding the types and extent of CSC marker glycosylation, and the various roles that these glycans play in CSC biology, including in mediating cell adhesion, metastasis, evading apoptosis, tear shear resistance, tumour growth, maintaining pluripotency, self-renewal, trafficking, maintaining stability, maintaining enzymatic activity and aiding epithelial mesenchymal transitioning. Given that CSCs markers have multiple diverse biological functions, and are potentially of significant diagnostic and therapeutic benefit the search for new markers that are uniquely expressed on CSCs is vital to selectively target/identify this subset of cancer cells. As such we have also outlined how high-throughput lectin microarrays can be used to successfully profile the glycosylation status of CSC and to identify glyco-markers unique to CSCs.

Understanding liver regeneration to bring new insights to the mechanisms driving cholangiocarcinoma

Cancer frequently arises in epithelial tissues subjected to repeated cycles of injury and repair. Improving our understanding of tissue regeneration is, therefore, likely to reveal novel processes with inherent potential for aberration that can lead to carcinoma. These highly conserved regenerative mechanisms are increasingly understood and in the liver are associated with special characteristics that underlie the organ's legendary capacity for restoration of size and function following even severe or chronic injury. The nature of the injury can determine the cellular source of epithelial regeneration and the signalling mechanisms brought to play. These observations are shaping how we understand and experimentally investigate primary liver cancer, in particular cholangiocarcinoma; a highly invasive malignancy of the bile ducts, resistant to chemotherapy and whose pathogenesis has hitherto been poorly understood. Interestingly, signals that drive liver development become activated in the formation of cholangiocarcinoma, such as Notch and Wnt and may be potential future therapeutic targets. In this review, we summarise the work which has led to the current understanding of the cellular source of cholangiocarcinoma, how the tumour recruits, sustains and is educated by its supporting stromal environment, and the tumour-derived signals that drive the progression and invasion of the cancer. With few current treatments of any true efficacy, advances that will improve our understanding of the mechanisms driving this aggressive malignancy are welcome and may help drive therapeutic developments.

Hepatocellular Carcinomas Originate Predominantly from Hepatocytes and Benign Lesions from Hepatic Progenitor Cells

Hepatocellular carcinoma (HCC) is an aggressive primary liver cancer. However, its origin remains a debated question. Using human data and various hepatocarcinogenesis mouse models, we show that, in early stages, transformed hepatocytes, independent of their proliferation status, activate hepatic progenitor cell (HPC) expansion. Genetic lineage tracing of HPCs and hepatocytes reveals that, in all models, HCC originates from hepatocytes. However, whereas in various models tumors do not emanate from HPCs, tracking of progenitors in a model mimicking human hepatocarcinogenesis indicates that HPCs can generate benign lesions (regenerative nodules and adenomas) and aggressive HCCs. Mechanistically, galectin-3 and α-ketoglutarate paracrine signals emanating from oncogene-expressing hepatocytes instruct HPCs toward HCCs. α-Ketoglutarate preserves an HPC undifferentiated state, and galectin-3 maintains HPC stemness, expansion, and aggressiveness. Pharmacological or genetic blockage of galectin-3 reduces HCC, and its expression in human HCC correlates with poor survival. Our findings may have clinical implications for liver regeneration and HCC therapy.

Shp2 promotes liver cancer stem cell expansion by augmenting β-catenin signaling and predicts chemotherapeutic response of patients

Src-homology 2 domain-containing phosphatase 2 (Shp2) has been reported to play an important role in the maintenance and self-renewal of embryonic and adult stem cells, but its role in cancer stem cells (CSCs) remains obscure. Herein, we observed high expression of Shp2 in both chemoresistant hepatocellular carcinomas (HCCs) and recurrent HCCs from patients. A remarkable increase of Shp2 was detected in sorted epithelial cell adhesion molecule-positive or cluster of differentiation 133-positive liver CSCs and in CSC-enriched hepatoma spheroids from patients. Up-regulated Shp2 facilitated liver CSC expansion by promoting the dedifferentiation of hepatoma cells and enhancing the self-renewal of liver CSCs. Mechanistically, Shp2 dephosphorylated cell division cycle 73 in the cytosol of hepatoma cells, and the dephosphorylated cell division cycle 73 bound β-catenin and facilitated the nuclear translocation of β-catenin, which promoted the dedifferentiation of hepatoma cells. Shp2 increased β-catenin accumulation by inhibiting glycogen synthase kinase 3β-mediated β-catenin degradation in liver CSCs, thereby enhancing the self-renewal of liver CSCs. Blockage of β-catenin abolished the discrepancy in liver CSC proportion and the self-renewal capacity between Shp2-depleted hepatoma cells and control cells, which further confirmed that β-catenin is required in Shp2-promoted liver CSC expansion. More importantly, HCC patients with low Shp2 levels benefited from transcatheter arterial chemoembolization or sorafenib treatment, but patients with high Shp2 expression did not, indicating the significance of Shp2 in personalized HCC therapy.

CONCLUSION

Shp2 could promote HCC cell dedifferentiation and liver CSC expansion by amplifying β-catenin signaling and may be useful in predicting patient response to chemotherapeutics. (Hepatology 2017;65:1566-1580).

Seeds in the liver

The liver is a crucial organ for homeostasis and has a tremendous self-renewal and regenerative capacity. It has long been believed that the self-renewal and repair of the liver within a given physiological condition or its repopulation in chronic liver diseases, when hepatocyte proliferation is impaired, will primarily be conducted by the proliferating duct cells, termed "oval cells" or hepatic progenitor cells (HPCs). In addition, numerous studies have revealed that HPCs are the initial tumor cells of liver cancer under certain micro-environments. However, benefit from the extensive application of lineage tracing strategies using the Cre/LoxP system, researchers have redefined the fate of these bipotential cells, raising obvious controversies regarding the capacity of liver cells to control their own biology and differentiation. Here, we review the relevant articles, focusing on cell-lineage tracing to better understanding seed cells and their distinct fate in the liver.

Liver carcinogenesis by FOS-dependent inflammation and cholesterol dysregulation

Hepatocellular cancers arise in a background of liver damage and inflammation. Bakiri et al. describe the function of the transcription factor c-Fos/AP-1 using mouse models and human data. c-Fos affects cholesterol and bile acid metabolism and induces DNA damage and inflammation, thus promoting liver cancer.

Human hepatocellular carcinomas (HCCs), which arise on a background of chronic liver damage and inflammation, express c-Fos, a component of the AP-1 transcription factor. Using mouse models, we show that hepatocyte-specific deletion of c-Fos protects against diethylnitrosamine (DEN)-induced HCCs, whereas liver-specific c-Fos expression leads to reversible premalignant hepatocyte transformation and enhanced DEN-carcinogenesis. c-Fos–expressing livers display necrotic foci, immune cell infiltration, and altered hepatocyte morphology. Furthermore, increased proliferation, dedifferentiation, activation of the DNA damage response, and gene signatures of aggressive HCCs are observed. Mechanistically, c-Fos decreases expression and activity of the nuclear receptor LXRα, leading to increased hepatic cholesterol and accumulation of toxic oxysterols and bile acids. The phenotypic consequences of c-Fos expression are partially ameliorated by the anti-inflammatory drug sulindac and largely prevented by statin treatment. An inverse correlation between c-FOS and the LXRα pathway was also observed in human HCC cell lines and datasets. These findings provide a novel link between chronic inflammation and metabolic pathways important in liver cancer.

Integrative Genomic Analysis of Cholangiocarcinoma Identifies Distinct IDH-Mutant Molecular Profiles

Cholangiocarcinoma (CCA) is an aggressive malignancy of the bile ducts, with poor prognosis and limited treatment options. Here, we describe the integrated analysis of somatic mutations, RNA expression, copy number, and DNA methylation by The Cancer Genome Atlas of a set of predominantly intrahepatic CCA cases and propose a molecular classification scheme. We identified an IDH mutant-enriched subtype with distinct molecular features including low expression of chromatin modifiers, elevated expression of mitochondrial genes, and increased mitochondrial DNA copy number. Leveraging the multi-platform data, we observed that ARID1A exhibited DNA hypermethylation and decreased expression in the IDH mutant subtype. More broadly, we found that IDH mutations are associated with an expanded histological spectrum of liver tumors with molecular features that stratify with CCA. Our studies reveal insights into the molecular pathogenesis and heterogeneity of cholangiocarcinoma and provide classification information of potential therapeutic significance.

Gene expression profiling of circulating CD133+ cells of hepatocellular carcinoma patients associated with HCV infection

AIM

Identifying the genetic expression profile of CD133⁺ cells from HCC patients compared to CD133⁺ cells from healthy volunteers that may contribute in hepatocarcinogenesis process.

METHOD

Circulating CD133⁺ cells were sorted from the peripheral blood of HCC patients as well as from healthy volunteers using magnetic activated cell sorting. The differential expression profile of stem cell related genes was performed using the Stem Cell PCR profiling assay.

RESULTS

Data analysis of stem cells related genes in CD133⁺ cells of the HCC group compared to the control group showed that; CCND2, COL1A1, CTNNA1, DLL3, JAG1, KRT15, MYC, NOTCH2, T and TERT were up-regulated (fold change=80, 68.6, 6.67, 7.22, 3.8, 15.2, 14.5, 105.6, 26.6 and 99 respectively while only CD3D was down-regulated (fold change=0.055) in HCC patients. However, after application of Beferroni correction to adjust P-value; KRT15 was the only gene that was significantly over expressed in CD133⁺ cells of HCC compared to control group (P-value=0.012).

CONCLUSION

KRT15 can be used to differentiate between circulating CD133⁺ cells from HCC group and control group. However, further study may be needed to confirm on the protein level.

Liver Cancer Cell of Origin, Molecular Class, and Effects on Patient Prognosis

Primary liver cancer is the second leading cause of cancer-related death worldwide and therefore a major public health challenge. We review hypotheses of the cell of origin of liver tumorigenesis and clarify the classes of liver cancer based on molecular features and how they affect patient prognosis. Primary liver cancer comprises hepatocellular carcinoma (HCC), intrahepatic cholangiocarcinoma (iCCA), and other rare tumors, notably fibrolamellar carcinoma and hepatoblastoma. The molecular and clinical features of HCC versus iCCA are distinct, but these conditions have overlapping risk factors and pathways of oncogenesis. A better understanding of the cell types originating liver cancer can aid in exploring molecular mechanisms of carcinogenesis and therapeutic options. Molecular studies have identified adult hepatocytes as the cell of origin. These cells have been proposed to transform directly into HCC cells (via a sequence of genetic alterations), to dedifferentiate into hepatocyte precursor cells (which then become HCC cells that express progenitor cell markers), or to transdifferentiate into biliary-like cells (which give rise to iCCA). Alternatively, progenitor cells also give rise to HCCs and iCCAs with markers of progenitor cells. Advances in genome profiling and next-generation sequencing have led to the classification of HCCs based on molecular features and assigned them to categories such as proliferation-progenitor, proliferation-transforming growth factor β, and Wnt-catenin β1. iCCAs have been assigned to categories of proliferation and inflammation. Overall, proliferation subclasses are associated with a more aggressive phenotype and poor outcome of patients, although more specific signatures have refined our prognostic abilities. Analyses of genetic alterations have identified those that might be targeted therapeutically, such as fusions in the FGFR2 gene and mutations in genes encoding isocitrate dehydrogenases (in approximately 60% of iCCAs) or amplifications at 11q13 and 6p21 (in approximately 15% of HCCs). Further studies of these alterations are needed before they can be used as biomarkers in clinical decision making.

The evolving concept of liver cancer stem cells

Liver cancer is an often fatal malignant tumor with a high recurrence rate and chemoresistance. The major malignant phenotypes of cancer, including recurrence, metastasis, and chemoresistance, are related to the presence of cancer stem cells (CSCs). In the past few decades, CSCs have been identified and characterized in many tumors including liver cancer. Accumulated evidence has revealed many aspects of the biological behavior of liver CSCs and the mechanism of their regulation. Based on these findings, a number of studies have investigated eradication of liver CSCs. This review focuses on the recent advances in our understanding of the biology of liver CSCs and the development of strategies for their treatment.

Stemness in Liver Cancer

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 [<citeref rid="ref1">1</citeref>]. Identification of common and cell of origin-specific phenotypic and genetic changes could provide new therapeutic targets for liver cancer.

Cholangiocarcinoma

Biliary tract cancer accounts for <1% of all cancers and affects chiefly an elderly population, with predominance in men. We distinguish cholangiocarcinoma (intrahepatic, hilar and distal) and gallbladder cancer, with different pathogenesis and prognosis. The treatment is based on surgery (whenever possible), radiotherapy in selected cases, and chemotherapy. The standard cytotoxic treatment for advanced/metastatic disease is represented by the combination of gemcitabine and cisplatin, whereas fluoropyrimidines are generally administered in second line setting. At the present time, no biologic drug demonstrated a clear efficacy in this cancer, although the molecular characterisation could provide a promising basis for experimental treatments. A good supportive care and an early palliative care are warranted in most patients and should be delivered as a part of a global approach.

Mutational landscape of combined hepatocellular carcinoma and cholangiocarcinoma, and its clinicopathological significance

AIMS

Combined hepatocellular carcinoma and cholangiocarcinoma (cHC-CC), which generally has a poor prognosis, comprises hepatocellular carcinoma (HCC), cholangiocarcinoma (CC), and diverse components with intermediate features between HCC and CC. Histological subtypes with stem cell (SC) features (the SC subtype) have different clinicopathological significance in cHC-CC. The mutational status may reflect the clinicopathological subgroup of cHC-CC together with the histological subtype.

METHODS AND RESULTS

We examined the mutational statuses of KRAS, IDH1 or IDH2 (IDH1/2), ARID1A, the TERT promoter, and TP53, and their relationships with clinicopathological features in 53 patients with cHC-CC. Background liver diseases were hepatitis B (n = 9), hepatitis C (n = 22), alcoholic liver disease (n = 5), non-alcoholic fatty liver disease (NAFLD) (n = 8), and unknown (n = 9). Mutations in KRAS, IDH1/2, ARID1A, the TERT promoter and TP53 were detected in four (7.5%), six (11.8%) seven (13.2%), 16 (31.3%), and 24 patients (45.3%), respectively. KRAS mutations correlated with higher histological diversity scores and a higher M-factor (P < 0.05). ARID1A mutations correlated with alcoholic liver disease, smaller tumour size, a lower grade of coexistent HCC, and α-fetoprotein (AFP) positivity, and were associated with cholangiolocellular carcinoma subtype predominance (P < 0.05). TERT promoter mutations correlated with hepatitis B, an intermediate subtype-predominant histology, higher clinical stage, and a higher N-factor (P < 0.05), and were associated with gender (female-predominant) and previous therapy. TP53 mutations correlated with AFP positivity (P < 0.05).

CONCLUSIONS

The results of the mutational analysis revealed that cHC-CC has diverse types of mutations, and also that mutations in the TERT promoter and ARID1A may reflect aetiological impact, different histological subtypes, histogenesis, and tumour aggressiveness. These results suggest the potential efficacy of molecular-based subclassification of cHC-CC.

[Diagnostics and treatment of cholangiocellular carcinoma]

Cholangiocellular carcinoma (CCA) is the second most frequent primary liver carcinoma and is an aggressive tumor, which is mostly diagnosed in advanced stages. The overall survival is poor. Histpathological analysis of tumor biopsies or cytological analysis of biliary brushings can be used to confirm the diagnosis. A differentiation is made between distal, perihilar and intrahepatic CCA. The anatomical position determines the diagnostic and therapeutic strategy. Before diagnostic or therapeutic measures are undertaken it is essential to resolve biliary obstruction via endoscopic stenting or percutaneous biliary drainage. Depending on the tumor stage curative treatment options comprise radical surgical resection with hepaticojejunostomy or in selected cases liver transplantation. For intrahepatic or distal CCA liver transplantation is not indicated. In the palliative setting systemic chemotherapy with gemcitabine and cisplatin leads to a significant improvement in survival time.

Clinical Significance of Epigenetic Alterations in Human Hepatocellular Carcinoma and Its Association with Genetic Mutations

Accumulation of genetic and epigenetic alterations is a hallmark of cancer genomes, including those in hepatocellular carcinoma (HCC). Particularly, in human HCC, epigenetic changes are more frequently observed than genetic changes in a variety of cancer-related genes, suggesting a potential role for epigenetic alterations during hepatocarcinogenesis. Several environmental factors, such as inflammation, obesity, and steatosis, are reported to affect the epigenetic status in hepatocytes, which could play a role in HCC development. In addition, genetic mutations in histone modulators and chromatin regulators would be critical for the acceleration of epigenetic alteration. It is also possible that major genetic mutations of HCC, such as TP53 and CNTTB1 mutations, are associated with the disturbance of epigenetic integrity. For example, specific TP53 mutations frequently induced by aflatoxin B1 exposure might affect histone modifiers and nucleosome remodelers. Generally, epigenetic alteration is reversible, because of which dysregulation of transcription takes place, without affecting protein structure. Therefore, differentiation therapy is one of the potential approaches for HCC with advanced epigenetic alterations. On the other hand, a tumor carrying an accumulation of genetic mutations would result in many abnormal proteins that could be recognized as non-self and could be targets for immune reactions; thus, immune-checkpoint blockers should be effective for HCCs with genetic hypermutation. Although the emergence of genetic and epigenetic alterations could be linked to each other and there could be some crossover or convergence between these cancer pathways, characterization of the mutation spectrum of genetic and epigenetic alterations could influence future HCC treatment.

Genetic lineage tracing analysis of the cell of origin of hepatotoxin-induced liver tumors in mice

The expression of biliary/progenitor markers by hepatocellular carcinoma (HCC) is often associated with poor prognosis and stem cell-like behaviors of tumor cells. Hepatocellular adenomas (HCAs) also often express biliary/progenitor markers and frequently act as precursor lesions for HCC. However, the cell of origin of HCA and HCC that expresses these markers remains unclear. Therefore, to evaluate if mature hepatocytes give rise to HCA and HCC tumors and to understand the molecular pathways involved in tumorigenesis, we lineage-labeled hepatocytes by injecting adeno-associated virus containing thyroxine-binding globulin promoter-driven causes recombination (AAV-TBG-Cre) into Rosa(YFP) mice. Yellow fluorescent protein (YFP) was present in >96% of hepatocytes before exposure to carcinogens. We treated AAV-TBG-Cre; Rosa(YFP) mice with diethylnitrosamine (DEN), followed by multiple injections of carbon tetrachloride to induce carcinogenesis and fibrosis and found that HCA and HCC nodules were YFP(+) lineage-labeled; positive for osteopontin, SRY (sex determining region Y)-box 9, and epithelial cell adhesion molecule; and enriched for transcripts of biliary/progenitor markers such as prominin 1, Cd44, and delta-like 1 homolog. Next, we performed the converse experiment and lineage-labeled forkhead box protein L1(Foxl1)-positive hepatic progenitor cells simultaneously with exposure to carcinogens. None of the tumor nodules expressed YFP, indicating that Foxl1-expressing cells are not the origin for hepatotoxin-induced liver tumors. We confirmed that HCA and HCC cells are derived from mature hepatocytes and not from Foxl1-Cre-marked cells in a second model of toxin-induced hepatic neoplasia, using DEN and 3,3',5,5'-tetrachloro-1,4-bis(pyridyloxy)benzene (TCPOBOP).

CONCLUSION

Hepatocytes are the cell of origin of HCA and HCC in DEN/carbon tetrachloride and DEN/TCPOBOP induced liver tumors. (Hepatology 2016;64:1163-1177).

Molecular Pathogenesis of Hepatocellular Carcinoma

The pathogenesis of hepatocellular carcinoma (HCC) is a multistep process involving the progressive accumulation of molecular alterations pinpointing different molecular and cellular events. The next-generation sequencing technology is facilitating the global and systematic evaluation of molecular landscapes in HCC. There is emerging evidence supporting the importance of cancer metabolism and tumor microenvironment in providing a favorable and supportive niche to expedite HCC development. Moreover, recent studies have identified distinct surface markers of cancer stem cell (CSC) in HCC, and they also put forward the profound involvement of altered signaling pathways and epigenetic modifications in CSCs, in addition to the concomitant drug resistance and metastasis. Taken together, multiple key genetic and non-genetic factors, as well as liver CSCs, result in the development and progression of HCC.