The identification of stem cells in human liver diseases and hepatocellular carcinoma. Exp Mol Pathol. 2010;88:331-340. [PMID: 20080086 DOI: 10.1016/j.yexmp.2010.01.003]

Hepatic Progenitor Cells in the Form of Ductular Structures within a GIST Liver Metastasis: Supporting a Putative Role in the Hepatic Metastatic Niche

INTRODUCTION

Recent studies have highlighted the presence of hepatic progenitor cells (HPCs) in metastatic liver carcinomas. We provide further evidence of this phenomenon, presenting a case of a gastrointestinal stromal tumour (GIST) liver metastasis with evidence of intra- and peritumoral HPC.

CASE DESCRIPTION

A 64-year-old man presented with a gastric mass diagnosed as a high-risk KIT-mutated GIST. The patient was treated with imatinib, recurring 5 years later with a liver mass. Liver biopsy disclosed a GIST metastasis, hallmarked by a proliferation of ductular structures without cytological atypia intermingled with the tumour cells, with a CK7/CK19/CD56-positive immunophenotype and rare CD44 positivity. The patient underwent liver resection, and the same ductular structures were present in the tumour interior and at its periphery.

CONCLUSION

We document for the time the presence of HPC in the form of ductular structures in a GIST liver metastasis, further supporting their role in the liver metastatic niche.

Correlation between Cancer Stem Cells, Inflammation and Malignant Transformation in a DEN-Induced Model of Hepatic Carcinogenesis

Chronic inflammation and cancer stem cells are known risk factors for tumorigenesis. The aetiology of hepatocellular carcinoma (HCC) involves a multistep pathological process that is characterised by chronic inflammation and hepatocyte damage, but the correlation between HCC, inflammation and cancer stem cells remains unclear. In this study, we examined the role of hepatic progenitor cells in a mouse model of chemical-induced hepatocarcinogenesis to elucidate the relationship between inflammation, malignant transformation and cancer stem cells. We used diethylnitrosamine (DEN) to induce liver tumour and scored for H&E and reticulin staining. We also scored for immunohistochemistry staining for OV-6 expression and analysed the statistical correlation between them. DEN progressively induced inflammation at week 7 (40%, 2/5); week 27 (75%, 6/8); week 33 (62.5%, 5/8); and week 50 (100%, 12/12). DEN progressively induced malignant transformation at week 7 (0%, 0/5); week 27 (87.5%, 7/8); week 33 (100%, 8/8); and week 50 (100%, 12/12). The obtained data showed that DEN progressively induced high-levels of OV-6 expression at week 7 (20%, 1/5); week 27 (37.5%, 3/8); week 33 (50%, 4/8); and week 50 (100%, 12/12). DEN-induced inflammation, malignant transformation and high-level OV-6 expression in hamster liver, as shown above, as well as applying Spearman’s correlation to the data showed that the expression of OV-6 was significantly correlated to inflammation (p = 0.001) and malignant transformation (p < 0.001). There was a significant correlation between the number of cancer stem cells, inflammation and malignant transformation in a DEN-induced model of hepatic carcinogenesis in the hamster.

Cancer stem cell markers for liver cancer and pancreatic cancer

Cancer stem cells (CSC) theory has ushered in a new era of cancer research. Tumor recurrence, metastasis and chemotherapy resistance are all related to the existence of cancer stem cells. Further understanding of tumor heterogeneity will contribute to targeted treatment. Liver cancer and pancreatic cancer are common digestive gland tumors with high lethality. This article reviews the identification and isolation of CSC markers in hepatocellular carcinoma and pancreatic cancer. The markers related signal pathways are involved in the occurrence and development of tumors, and have a significant impact on the proliferation, metastasis and invasion of cancer cells, which can be used as potential molecular therapeutic targets. This study will be helpful to understand cancer stem cell like cells.

LncSEA: a platform for long non-coding RNA related sets and enrichment analysis

Long non-coding RNAs (lncRNAs) have been proven to play important roles in transcriptional processes and various biological functions. Establishing a comprehensive collection of human lncRNA sets is urgent work at present. Using reference lncRNA sets, enrichment analyses will be useful for analyzing lncRNA lists of interest submitted by users. Therefore, we developed a human lncRNA sets database, called LncSEA, which aimed to document a large number of available resources for human lncRNA sets and provide annotation and enrichment analyses for lncRNAs. LncSEA supports >40 000 lncRNA reference sets across 18 categories and 66 sub-categories, and covers over 50 000 lncRNAs. We not only collected lncRNA sets based on downstream regulatory data sources, but also identified a large number of lncRNA sets regulated by upstream transcription factors (TFs) and DNA regulatory elements by integrating TF ChIP-seq, DNase-seq, ATAC-seq and H3K27ac ChIP-seq data. Importantly, LncSEA provides annotation and enrichment analyses of lncRNA sets associated with upstream regulators and downstream targets. In summary, LncSEA is a powerful platform that provides a variety of types of lncRNA sets for users, and supports lncRNA annotations and enrichment analyses. The LncSEA database is freely accessible at http://bio.liclab.net/LncSEA/index.php.

Epigenetic dysregulation in hepatocellular carcinoma: an up-to-date review

Due to the advances made in research based on next generation sequencers, it is now possible to detect and analyze epigenetic abnormalities associated with cancer. DNA methylation, various histone modifications, chromatin remodeling, and non-coding RNA-associated gene silencing are considered to be transcriptional regulatory mechanisms associated with gene expression changes. The breakdown of this precise regulatory system is involved in the transition to cancer. The important role of epigenetic regulation can be observed from the high rate of genetic mutations and abnormal gene expression leading to a breakdown in epigenetic gene expression regulation seen in hepatocellular carcinoma (HCC). Based on an understanding of epigenomic abnormalities associated with pathological conditions, these findings will lead the way to diagnosis and treatment. In particular, in addition to the fact that there are few choices in terms of extant drug therapies aimed at HCC, there are limits to their antitumor effects. The clinical application of epigenetic therapeutic agents for HCC has only just begun, and future developments are expected.

COMMD7 Regulates NF-κB Signaling Pathway in Hepatocellular Carcinoma Stem-like Cells

Previous studies showed that the COpper Metabolism gene MURR1 Domain (COMMD) family of proteins was abnormally expressed in hepatocellular carcinoma (HCC). This study aimed to explore the roles of COMMD1 and COMMD7 in regulating nuclear factor κB (NF-κB) signaling in HCC stem cells (HCSCs). In vivo, the expression of COMMD7 and COMMD1 was determined in 35 pairs of HCC cancer tissues and adjacent tissues, and the effect of COMMD7 silencing on xenograft tumor growth was evaluated. In vitro, the effects of COMMD7 silencing and COMMD1 overexpression on HCSC function were assessed. Results found that the expression levels of COMMD7 were higher, whereas COMMD1 levels were lower in HCC tissues and HCSCs. COMMD7 silencing or COMMD1 overexpression inhibited cell proliferation, migration, and invasion through suppression of NF-κB p65. Furthermore, COMMD7 positively regulated NF-κB by upregulating protein inhibitor for activated stat 4 (PIAS4). This study demonstrates that COMMD7 has a dual regulatory role in the NF-κB signaling pathway in Nanog⁺ HCSCs.

Prognostic value of the expression of cancer stem cell-related markers CD133 and CD44 in hepatocellular carcinoma: From patients to patient-derived tumor xenograft models

High expression of cancer stem cell (CSC) markers is related to poor prognosis of patients with hepatocellular carcinoma (HCC). However, the expression of these markers in patient-derived xenograft (PDX) models and the relationship of the expression levels of these markers between HCC patients and their PDX models at subsequent low passages are unclear. To investigate the prognostic impact of putative CSC markers in patients with HCC and in related PDX models, the expression of CD133, CD90, CD44, ALDH1, CK7, CK19, OCT4, SOX2, vimentin, nestin, CD13 and EpCam were assessed by quantitative reverse transcription-PCR (qRT-PCR) and then were validated using immunohistochemistry in tumor or peritumoral tissues from patients and tumor tissues from PDX models. Cumulative survival analysis of the patients and animals was conducted using the Kaplan-Meier method and the log-rank test. Only the expression levels of CD133 and CD44 were higher in tumor tissues than in the peritumoral tissues of HCC patients by qRT-PCR. High consistency of the prognostic value of the expression of CD133/CD44 was observed in HCC patients and the PDX models. High expression levels of CD133 and CD44 were positively related to the poor prognosis of HCC patients and to that in the PDX models. PDX HCC models in the present study have been suggested to be predictive of disease outcome, which could shed light on personalized medicine and the mechanisms of CSC marker expression on prognosis.

The Progress and Prospects of Putative Biomarkers for Liver Cancer Stem Cells in Hepatocellular Carcinoma

Accumulating evidence suggests that hepatocellular carcinoma (HCC) is organized by liver cancer stem cells (LCSCs), which are a subset of cells with “stem-like” characteristics. Identification of the LCSCs is a fundamental and important problem in HCC research. LCSCs have been investigated by various stem cell biomarkers. There is still lack of consensus regarding the existence of a “global” marker for LCSCs in HCC. In this review article, we summarize the progress and prospects of putative biomarkers for LCSCs in the past decades, which is essential to develop future therapies targeting CSCs and to predict prognosis and curative effect of these therapies.

The role of liver progenitor cells during liver regeneration, fibrogenesis, and carcinogenesis

The growing worldwide challenge of cirrhosis and hepatocellular carcinoma due to increasing prevalence of excessive alcohol consumption, viral hepatitis, obesity, and the metabolic syndrome has sparked interest in stem cell-like liver progenitor cells (LPCs) as potential candidates for cell therapy and tissue engineering, as an alternative approach to whole organ transplantation. However, LPCs always proliferate in chronic liver diseases with a predisposition to cancer; they have been suggested to play major roles in driving fibrosis, disease progression, and may even represent tumor-initiating cells. Hence, a greater understanding of the factors that govern their activation, communication with other hepatic cell types, and bipotential differentiation as opposed to their potential transformation is needed before their therapeutic potential can be harnessed.

Significance of hepatitis virus infection in the oncogenic initiation of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most common causes of cancer-related death worldwide. Chronic infection of hepatitis B virus (HBV) and/or hepatitis C virus (HCV) is a major risk factor in the development of the HCC, independently from excessive alcohol abuse and metabolic disease. Since the biology of HBV and HCV is different, their oncogenic effect may go through different mechanisms, direct and/or indirect. Viral hepatitis infection is associated with cellular inflammation, oxidative stress, and DNA damage, that may lead to subsequent hepatic injuries such as chronic hepatitis, fibrosis, cirrhosis, and finally HCC. Direct oncogenic properties of these viruses are related with their genotypic characteristics and the ability of viral proteins to interact with host proteins, thus altering the molecular pathways balance of the cells. In addition, the integration of HBV DNA, especially the gene S and X, in a particular site of the host genome can disrupt chromosomal stability and may activate various oncogenic mechanisms, including those in hematopoietic cells. Recently, several studies also had demonstrated that viral hepatitis could trigger the population of hepatic cancer stem cells. This review summarize available pre-clinical and clinical data in literature regarding oncogenic properties of HBV and HCV in the early initiation of HCC.

Digital quantitation of HCC-associated stem cell markers and protein quality control factors using tissue arrays of human liver sections

The most common type of liver cancer, hepatocellular carcinoma (HCC), affects over 500,000 people in the world. In the present study, liver tumor resections were used to prepare tissue arrays to examine the intensity of fluorescence of IHC stained stem cell markers in liver tissue from malignant HCC tumors and accompanying surrounding non-tumor liver. We hypothesized that a correlation exists between the fluorescence intensity of IHC stained HCC and surrounding non-tumor liver compared to liver tissue from a completely normal liver. 120 liver resection specimens (including four normal controls) were placed on a single slide to make a tissue array. They were examined by digitally quantifying the intensity of fluorescence using immuno-histochemically stained stem cell markers and protein quality control proteins. The stem cell markers were OCT3/4, Nanog, CD133, pEZH2, CD49F and SOX2. The protein quality control proteins were FAT10, UBA-6 and ubiquitin. The data collected was used to compare normal liver tissue with HCCs and parent liver tissue resected surgically using antibodies to stem cell markers and quality control protein markers. The measurements of the stem cell marker CD133 indicated an increase of fluorescence intensity for both the parent liver tissue and the HCC liver tissues. The other stem cell markers changed as follows: Nanog and OCT3/4 were decreased in both the HCCs and the parent livers; PEZH2 was reduced in the HCCs; SOX2 was increased in the parent livers compared to the controls; and CD49f was decreased in HCCs only. Protein quality control markers FAT10 and ubiquitin were downregulated in both the HCCs and the adjacent non-tumor tissue compared to the controls. UBA6 was increased in both the HCCs and the parent livers, and the levels were higher in the HCCs compared to the parent livers.

SALL4 immunoreactivity predicts prognosis in Western hepatocellular carcinoma patients but is a rare event: a study of 236 cases

Prognostic biomarkers that stratify patients with cancer are needed. Recent studies from Asia have implicated SALL4, a stem cell marker, as useful in identifying aggressive cases of hepatocellular carcinoma (HCC), and >50% of the cases tested had upregulation by microarray or dense immunoreactivity. Given the differences in predominant etiologic factors between the Asian and Western HCC, we sought to determine the prevalence of SALL4 immunoreactivity and its clinical relevance in Western HCC patients. We constructed tissue microarrays from 236 adult HCCs. Two cores each of tumor and nontumor tissue were included for each case. SALL4 immunohistochemistry was scored in a semiquantitative manner and the results correlated with recurrence-free and overall survival, in addition to standard demographics. Among the 236 cases, 165 (70.0%) were male. The median age was 59 years (range: 19 to 83 y). The majority (78.4%) of patients were white, followed by African American (15.7%), Asian (3.8%), Hispanic (1.7%), and Native American (0.4%). The majority of patients had hepatitis C (42.8%), followed by alcoholic liver disease and hepatitis B (both 8.9%), and nonalcoholic steatohepatitis (3.8%). SALL4 immunoreactivity was detected in a total of 3 cases (1.3%), and nonreactivity was validated on tissue sections from 73 cases. By univariate analysis, the SALL4-positive cases had significantly higher tumor grade (P=0.0251), more frequent lymphovascular invasion (P=0.0150), and shorter recurrence-free survival (7.90 vs. 57.54 mo; P=0.0115) and overall survival (7.90 vs. 64.87 mo; P=0.0018). Although SALL4 immunoreactivity in Western HCC is correlated with higher grade and poor prognosis, this is a rare event. Therefore, universal application of SALL4 as a biomarker for HCC should be performed with caution.

p27 Is a critical prognostic biomarker in non-alcoholic steatohepatitis-related hepatocellular carcinoma

Non-alcoholic steatohepatitis (NASH) is a recently identified chronic liver disease, which progresses to liver cirrhosis and hepatocellular carcinoma (HCC). As the number of patients studied to date has been limited, clinically useful prognostic biomarkers of NASH-related HCC have not been available. In this study, we investigated the status of a cell-cycle regulator, p27, in NASH-related HCC. p27 has been regarded as a prognostic factor in various types of cancer patients. A total of 22 cases with NASH-related HCC were analyzed for p27 protein expression, and phosphorylation at threonine 157 (T157) and serine 10 (S10) by immunohistochemical analysis. The correlation of p27 with tumor characteristics, disease-free survival (DFS), and overall survival was analyzed. p27 expression was decreased in 13 HCCs (59%), and was significantly correlated with enlarged tumor size (p = 0.01) and increased cell proliferation (p < 0.01). Phospho-p27 at T157 and S10 was detected in four (18%) and seven (32%) cases, respectively, and patients positive for phospho-p27 (S10) showed reduced DFS (hazard ratio 7.623, p = 0.016) by univariate analysis. Further studies with more patients are required to verify the usefulness of p27 as a biomarker for predicting tumor recurrence in NASH patients.

Clinicopathologic implication of hepatic progenitor cell marker expression in hepatoblastoma

Hepatic progenitor cells (HPCs) are thought to play a role in hepatoblastoma, as hepatoblastomas are characterized by an immature histology and a wide variety of cell lineages. We aimed to investigate the extent of expression of HPCs marker and its clinical implication in hepatoblastoma. We collected 61 hepatoblastomas and 9 childhood hepatocellular carcinomas (HCCs) and performed immunohistochemistry for HPC markers, including cytokeratin 19 (CK19), octamer-binding transcription factor 3/4 (Oct-3/4), epithelial cell adhesion molecule (EpCAM), and delta-like 1 homolog (DLK1). Of the hepatoblastoma samples, 27/61 (44.3%), 21/61 (34.4%), 51/61 (83.6%) and 56/61 (91.8%) exhibited positivity for CK19, Oct-3/4, EpCAM and DLK-1, respectively. For HCCs, the rates of expression were 22.2% (CK19), 77.8% (EpCAM) and 77.8% (DLK-1). Oct-3/4 was not expressed in HCC cells. Hepatoblastomas with a poorly differentiated epithelial component had a higher incidence of CK19 and Oct-3/4 expression than those with a well differentiated epithelial component (p=0.005 and 0.037, respectively). Higher disease stage of hepatoblastoma was correlated with CK19 expression (p=0.043). Oct-3/4-positive hepatoblastomas were associated with short disease-free survival (p=0.035). Both hepatoblastomas and childhood HCCs, therefore, exhibit characteristics of HPCs, and the poor prognosis of patients with Oct-3/4-positive hepatoblastoma suggests that stem-like properties affect hepatoblastoma pathogenicity.

RNA interference-mediated silencing of NANOG leads to reduced proliferation and self-renewal, cell cycle arrest and apoptosis in T-cell acute lymphoblastic leukemia cells via the p53 signaling pathway

NANOG is critical for maintaining the self-renewal and proliferative properties of embryonic stem cells. Here we found that cultured T-cell acute lymphoblastic leukemia (T-ALL) cells, as well as human primary T-ALL cells, express a functional variant of NANOG. NANOG mRNA is derived predominantly from a retrogene locus termed NANOGP8. Furthermore, we showed that RNA interference-mediated NANOG knockdown inhibited cell proliferation, reduced self-renewal, promoted apoptosis and arrested the cell cycle through a p53-mediated pathway in leukemic cells. These findings demonstrate the oncogenic potential of this pluripotent gene in human T-ALL cells.

Hepatic progenitor cells: their role and functional significance in the new classification of primary liver cancers

Hepatic progenitor cells (HPCs) are bipotential cells residing in normal liver. Their proliferation is observed in reactive conditions of the liver and in primary liver cancers. The observation that some hepatocellular carcinomas (HCCs) express a biliary-like immunophenotype has led to the identification of HPCs in HCC. Accumulating evidence suggests that HPCs play a role as the cell of origin in a variety of primary liver cancers. This has led to the development of revolutionary concepts in hepatocarcinogenesis. In this article, the role and significance of HPCs in HCC, including its classification, are summarized and discussed.

Epigenetic events in liver cancer resulting from alcoholic liver disease

Epigenetic mechanisms play an extensive role in the development of liver cancer (i.e., hepatocellular carcinoma [HCC]) associated with alcoholic liver disease (ALD) as well as in liver disease associated with other conditions. For example, epigenetic mechanisms, such as changes in the methylation and/or acetylation pattern of certain DNA regions or of the histone proteins around which the DNA is wrapped, contribute to the reversion of normal liver cells into progenitor and stem cells that can develop into HCC. Chronic exposure to beverage alcohol (i.e., ethanol) can induce all of these epigenetic changes. Thus, ethanol metabolism results in the formation of compounds that can cause changes in DNA methylation and interfere with other components of the normal processes regulating DNA methylation. Alcohol exposure also can alter histone acetylation/deacetylation and methylation patterns through a variety of mechanisms and signaling pathways. Alcohol also acts indirectly on another molecule called toll-like receptor 4 (TLR4) that is a key component in a crucial regulatory pathway in the cells and whose dysregulation is involved in the development of HCC. Finally, alcohol use regulates an epigenetic mechanism involving small molecules called miRNAs that control transcriptional events and the expression of genes important to ALD.

Nanog regulates self-renewal of cancer stem cells through the insulin-like growth factor pathway in human hepatocellular carcinoma

Hepatocellular carcinoma (HCC) exhibits cellular heterogeneity and embryonic stem-cell-related genes are preferentially overexpressed in a fraction of cancer cells of poorly differentiated tumors. However, it is not known whether or how these cancer cells contribute to tumor initiation and progression. Here, our data showed that increased expression of pluripotency transcription factor Nanog in cancer cells correlates with a worse clinical outcome in HCC. Using the Nanog promoter as a reporter system, we could successfully isolate a small subpopulation of Nanog-positive cells. We demonstrate that Nanog-positive cells exhibited enhanced ability of self-renewal, clonogenicity, and initiation of tumors, which are consistent with crucial hallmarks in the definition of cancer stem cells (CSCs). Nanog(Pos) CSCs could differentiate into mature cancer cells in in vitro and in vivo conditions. In addition, we found that Nanog(Pos) CSCs exhibited resistance to therapeutic agents (e.g., sorafenib and cisplatin) and have a high capacity for tumor invasion and metastasis. Knock-down expression of Nanog in Nanog(Pos) CSCs could decrease self-renewal accompanied with decreased expression of stem-cell-related genes and increased expression of mature hepatocyte-related genes. Overexpression of Nanog in Nanog(Neg) cells could restore self-renewal. Furthermore, we found that insulin-like growth factor (IGF)2 and IGF receptor (IGF1R) were up-regulated in Nanog(Pos) CSCs. Knock-down expression of Nanog in Nanog(Pos) CSCs inhibited the expression of IGF1R, and overexpression of Nanog in Nanog(Neg) cells increased the expression of IGF1R. A specific inhibitor of IGF1R signaling could significantly inhibit self-renewal and Nanog expression, indicating that IGF1R signaling participated in Nanog-mediated self-renewal.

CONCLUSION

These data indicate that Nanog could be a novel biomarker for CSCs in HCC, and that Nanog could play a crucial role in maintaining the self-renewal of CSCs through the IGF1R-signaling pathway.

Capturing circulating tumor cells of hepatocellular carcinoma

Early metastases of hepatocellular carcinoma (HCC) may be detected by the isolation of circulating tumor cells (CTCs) in the bloodstream. During the course of therapeutic attempts, monitoring CTC changes in patients with HCC is helpful for the efficacy assessment. Nevertheless, the markers used for the detection, such as α-feto protein, asialoglycoprotein receptor or epithelial cell adhesion molecule, CD133 or CD90, are not specific for HCC CTCs. In spite of these limitations, a timely determination of the existence of CTCs will be beneficial for the monitoring of distant metastases, the evaluation of therapeutic attempts, and the prediction of prognosis.

Ultrastructure of liver progenitor/oval cells in children with nonalcoholic steatohepatitis

PURPOSE

Very interesting reports have appeared lately on the role of liver progenitor/oval cells in the morphogenesis and development of nonalcoholic steatohepatits (NASH) in adult patients and experimental animals. However, no literature data concerning pediatric patients have been available. Therefore, the purpose of the study was to evaluate the ultrastructure of the population of liver progenitor/oval cells in the biopsy material from children with previously clinocopathologically diagnosed NASH.

MATERIAL/METHODS

Electron-microscopic examinations were conducted on fresh tissue samples collected from 10 children with NASH (aged 2-14 years), which were fixed with a solution of 2% paraformaldehyde and 2.5% glutaraldehyde in 0.1 M cacodylate buffer.

RESULTS

Ultrastructural examinations of the liver progenitor/oval cells in children with NASH show a quite prominent number of these cells, especially their two types, hepatic progenitor cells (HPCs) and intermediate hepatocyte-like cells (IHCs), with intermediate bile-like cells being the least frequent. They were found to occur single or in clusters of two, seldom of three, and frequently in the areas of advanced liver fibrosis or close to them. Many times, these cells were accompanied by hepatocytes showing a varying degree of death, to total cell disintegration. Interesting was the presence of activated nonparenchymal liver cells, i.e. Kupffer cells/macrophages and hepatic stellate cells, frequently found to adhere to the hepatic oval cells.

CONCLUSIONS

The current study suggests a marked involvement of the population of liver progenitor/oval cells, mainly HPCs and IHCs, in the development of nonalcoholic steatohepatitis in pediatric patients, especially in fibrosis progression.

Increased expression of OCT4 is associated with low differentiation and tumor recurrence in human hepatocellular carcinoma

Octamer binding transcription factor 4 (OCT4), a key transcription factor required to maintain self-renewal and pluripotency of human and mouse embryonic stem cells, has been recently identified to be associated with tumorigenesis and malignant transformation of many types of cancers. This study was to determine the roles of OCT4 in HCC recurrence and their impact on the clinical outcome of HCC patients. Western blot and immunohistochemical stains were used to detect the expression of OCT4 protein in 152 HCC tissues and 40 cirrhosis tissues, as well as in 6 human HCC cell lines and normal hepatocytes. OCT4 expression in HCC cell lines and tumor tissues was higher than in normal hepatocytes and cirrhosis tissues. Overexpression of OCT4 was significantly associated with low differentiation and tumor recurrence. Patients with elevated expression of OCT4 protein usually carried a poor overall survival and high recurrence rate. Multivariate analysis showed that OCT4 expression was an independent predictive factor for HCC patients survival. OCT4 might serve as a promising biomarker for the diagnosis of highly recurrent cases of HCC and could be used as a valuable indicator for predicting the prognosis of HCC.

NEMO expression in human hepatocellular carcinoma and its association with clinical outcome

The nuclear factor κ-light-chain enhancer of activated B-cells (NF-κB) signaling pathway is regarded as an important factor in inflammation and carcinogenesis. Recently, a role in hepatocarcinogenesis has been attributed to the NF-κB regulatory subunit IKKγ (NEMO) using knockout mice. However, a detailed investigation of NEMO expression in human hepatocellular carcinomas (HCCs) has not yet been reported. We selected 85 HCC patients who had undergone curative liver resection and analyzed NEMO expression of the respective tumors by immunohistochemistry, Western blotting, and real-time PCR. NEMO expression was correlated with clinicopathological parameters, and the impact on 5-year disease-free survival and 5-year overall survival was calculated using multivariate Cox proportional models. In our study, complete loss of NEMO immunoreactivity was found in 34 (40%) of 85 HCCs compared with their adjacent nonneoplastic tissue (P < .05). NEMO messenger RNA (mRNA) expression was detected in all HCC cases; however, no correlation between NEMO immunoreactivity and mRNA level was found. Five-year overall survival rates for patients with low and high NEMO expression were 22% and 50%, respectively (P = .049). However, high tumor stage, but not level of NEMO expression, was confirmed as an independent poor prognostic factor for 5-year disease-free survival (hazards ratio [HR] = 2.1, 95% confidence interval [CI] = 1.3-3.6, P = .009) and 5-year overall survival (HR = 2.5, CI = 1.4-4.4, P = .002). In conclusion, a loss of NEMO immunoreactivity occurs in a substantial proportion of human HCCs. Although low NEMO expression is correlated with a poor 5-year overall survival in patients with HCC, NEMO cannot be regarded as an independent prognostic marker for predicting the clinical outcome of patients suffering from HCC.

FAT10 mediates the effect of TNF-α in inducing chromosomal instability

Tumor necrosis factor-alpha (TNF-α) plays important roles in chronic inflammation-associated tumorigenesis but the mechanisms involved remain poorly understood. Previously, we reported that high levels of FAT10 led to chromosomal instability that is mediated by an abbreviated mitotic phase. Here, we show that TNF-α induces FAT10 gene expression through TNF receptor 1 (TNFR1) and activates the NF-κB pathway in HCT116 and SW620 cells. TNF-α treatment also leads to an abbreviated mitotic phase that can be reversed by inhibiting FAT10 expression. This abbreviated mitotic phase is correlated with a TNF-α-induced reduction in the kinetochore localization of MAD2 during prometaphase which, again, can be reversed by inhibiting FAT10 gene expression. There is greater variability of chromosome numbers in HCT116 and SW620 cells treated with TNF-α than in untreated cells, which can be reversed by the introduction of short hairpin RNA (shRNA) against FAT10. The more stable chromosome numbers in HCT116 cells expressing FAT10 shRNA can revert to greater variability with the addition of a mutant FAT10 that is not recognized by the FAT10 shRNA. Upon TNF-α stimulation, higher cell death is observed when FAT10 expression is inhibited by shRNA. These data strongly suggest that FAT10 plays an important role in mediating the function of TNF-α during tumorigenesis by inducing cell cycle deregulation and chromosomal instability, and by inhibiting apoptosis.

Epithelial mesenchymal transition and hedgehog signaling activation are associated with chemoresistance and invasion of hepatoma subpopulations

BACKGROUND & AIMS

Our previous studies showed that CD133, EpCAM, and aldehyde dehydrogenase (ALDH) are useful markers to identify cancer stem cells (CSCs) in hepatocellular carcinoma (HCC) tissues. The present study aims to evaluate chemosensitivity and invasion capability of HCC based on CSC marker profiles, and to explore the underlying molecular mechanisms.

METHODS

Hepatoma cell lines were separated into subpopulations according to CD133, EpCAM, and ALDH expression profiles. Epithelial mesenchymal transition (EMT) and hedgehog (Hh) signaling were examined to identify their links with chemoresistance and aggressive invasion.

RESULTS

Well-differentiated cell lines were positive for CD133(+)/ALDH(high) and CD133(+)/EpCAM(+) at 1.5-15% and 2.3-8.3%; whereas, poorly-differentiated cells were almost all negative for these markers. FACS-enriched CD133(+)/ALDH(high) and CD133(+)/EpCAM(+) Hep3B and Huh-7 cells formed more spheroids in vitro. CD133(-)/ALDH(low) HLE cells were more resistant to cisplatin, doxorubicin or sorafenib than their positive counterparts. CD133(-)/EpCAM(-) Huh-7 cells or CD133(-)/ALDH(-) HLE cells exhibited a higher invasion rate than their positive counterparts. HLE and HLF cells acquired EMT in double negative subpopulations. Hh activity in Huh-7 CD133(-)/EpCAM(-) cells was higher than in their positive counterparts, and the inhibition of Hh activity by cyclopamine resulted in reduced cell proliferation.

CONCLUSIONS

Well-differentiated CD133(+)/ALDH(high) or CD133(+)/EpCAM(+) cells appear to be a CSC/initiating subpopulation; whereas, in poorly-differentiated hepatoma cells, EMT and enhanced hedgehog signaling activity may be responsible for their chemoresistance and invasion. These findings underscore the significance of EMT and enhanced Hh signaling in liver cancer stem or initiating cells.

Polymeric nanoparticle-encapsulated hedgehog pathway inhibitor HPI-1 (NanoHHI) inhibits systemic metastases in an orthotopic model of human hepatocellular carcinoma

PURPOSE

To illustrate the prognostic significance of hedgehog (Hh) signaling in patients with hepatocellular carcinoma (HCC) and to evaluate the efficacy of a novel nanoparticle-encapsulated inhibitor of the Hh transcription factor, Gli1 (NanoHHI) using in vitro and in vivo models of human HCCs.

EXPERIMENTAL DESIGN

Patched1 (Ptch1) expression was detected in tumor tissue microarrays of 396 patients with HCC who underwent curative surgical resection during February 2000 to December 2002. Prognostic significance was assessed using Kaplan-Meier survival estimates and log-rank tests. The effects of NanoHHI alone and in combination with sorafenib were investigated on HCC cell lines. Primary HCC tumor growth and metastasis were examined in vivo using subcutaneous and orthotopic HCC xenografts in nude mice.

RESULTS

Elevated expression of Ptch1 in HCC tissues was significantly related to disease recurrence, as well as a shorter time to recurrence in patients with HCC. In vitro, NanoHHI significantly inhibited the proliferation and invasion of HCC cell lines. NanoHHI potently suppressed in vivo tumor growth of HCC xenografts in both subcutaneous and orthotopic milieus, and in contrast to sorafenib, resulted in significant attenuation of systemic metastases in the orthotopic setting. Furthermore, NanoHHI significantly decreased the population of CD133-expressing HCC cells, which have been implicated in tumor initiation and metastases.

CONCLUSION

Downstream Hh signaling has prognostic significance in patients with HCC as it predicts early recurrence. Gli inhibition through NanoHHI has profound tumor growth inhibition and antimetastatic effects in HCC models, which may provide a new strategy in the treatment of patients with HCC and prevention post-operative recurrence.

Tg737 inhibition results in malignant transformation in fetal liver stem/progenitor cells by promoting cell-cycle progression and differentiation arrest

Cancer stem/progenitor cells (CSPCs) may originate from the malignant transformation of normal stem cells. However, the mechanism by which normal stem cells undergo such transformation is not understood. Our previous studies provided evidence that Tg737 may play an important role in carcinogenesis of liver stem cells. In this study, we investigated the role of Tg737 in the malignant transformation of fetal liver stem/progenitor cells (FLSPCs). We inhibited Tg737 in FLSPCs using short hairpin RNA (shRNA). The microscopic observations of freshly purified Tg737 normal FLSPCs (nFLSPCs) and Tg737-silent FLSPCs (sFLSPCs), which showed high expression levels of stem cell markers, revealed no significant morphological changes in sFLSPCs. Following RNAi of Tg737, the mRNA and protein levels of sFLSPCs decreased by 81.81% and 80.10% as shown by PCR, Western blot and immunocytochemistry analyses. Excluding apoptosis-related effects, we found that silencing of Tg737 resulted in enhanced cell proliferation through promoting cell-cycle progression via upregulation of cyclin D1 and cyclin B expression (P < 0.05). Silencing of Tg737 also resulted in significant arrest of cell differentiation (P < 0.05), stable expression of both albumin (ALB) and alpha fetoprotein (AFP) (P > 0.05) and quiescent ultrastructure. Assessment of cell malignant traits by transwell migration assays and by growth of xenograft tumors in athymic mice showed that reduced expression of Tg737 greatly promoted cell invasion and hepatocarcinogenesis of FLSPCs (P < 0.05). This work shows that inactivation of Tg737 may play an important role in malignant transformation of FLSPCs.

The role of innate immunity in the pathogenesis of preneoplasia in drug-induced chronic hepatitis based on a mouse model

Innate immunity factors such as conversion of the 26S proteasome to form the immunoproteasome and the Toll-like receptor signaling pathways are activated in chronic hepatitis induced by the carcinogenic drug DDC. Over time, preneoplastic hepatocyte phenotypes appear in the liver parenchyma. These changed hepatocytes expand in number because they have a growth advantage over normal hepatocytes when responding to chronic liver injury. The changed hepatocytes can be identified using immunofluorescent antibodies to preneoplastic cells e.g. FAT10/UbD, A2 macroglobulin, glutathione transpeptidase, alpha fetoprotein, glycipan 3, FAS, and gamma glutamyl transpeptidase. The formation of the preneoplastic cells occurs concomitant with activation of the Toll-like receptor signaling pathways and the transformation of the 26S proteasome to form the immunoproteasome. This transformation is in response to interferon stimulating response element on the promoter of the FAT10/UbD gene. NFκB, Erk, p38 and Jnk are also up regulated. Specific inhibitors block these responses in vitro in a mouse tumor cell line exposed to interferon gamma. Mallory-Denk bodies form in these preneoplastic cells, because of the depletion of the 26S proteasome due to formation of the immunoproteasome. Thus, MDB forming cells are also markers of the preneoplastic hepatocytes. The UbD positive preneoplastic cells regress when the liver injury induced chronic hepatitis subsides. When the drug DDC is refed to mice and chronic hepatitis is activated, the preneoplastic cell population expands and Mallory-Denk bodies rapidly reform. This response is remembered by the preneoplastic cells for at least four months indicating that an epigenetic cellular memory has formed in the preneoplastic cells. This proliferative response is prevented by feeding methyl donors such as S-adenosylmethionine or betaine. Drug feeding reduces the methylation of H(3) K4, 9, and 27 and this response is prevented by feeding the methyl donors. After 8 to 15months of drug withdrawal in mice the preneoplastic liver cells persist as single or small clusters of cells in the liver lobules. Multiple liver tumors form, some of which are hepatocellular carcinomas. The tumors immunostain positively for the same preneoplastic markers as the preneoplastic cells. Similar cells are identified in human cirrhosis and hepatocellular carcinoma indicating the relevance of the drug model described here to the preneoplastic changes associated with human chronic hepatitis and hepatocellular carcinoma.

Tumor initiation and progression in hepatocellular carcinoma: risk factors, classification, and therapeutic targets

Hepatocellular carcinoma (HCC) is a major health problem worldwide responsible for 500 000 deaths annually. A number of risk factors are associated with either the induction of the disease or its progression; these include infection with hepatitis B or C virus, alcohol consumption, non-alcoholic steatohepatitis and certain congenital disorders. In around 80% of the cases, HCC is associated with cirrhosis or advanced fibrosis and with inflammation and oxidative stress. In this review we focus firstly on the different risk factors for HCC and summarize the mechanisms by which each is considered to contribute to HCC. In the second part we look at the molecular processes involved in cancer progression. HCC development is recognized as a multistep process that normally develops over many years. Over this period several mutations accumulate in the cell and that stimulate malign transformation, growth, and metastatic behavior. Over the recent years it has become evident that not only the tumor cell itself but also the tumor microenviroment plays a major role in the development of a tumor. There is a direct link between the role of inflammation and cirrhosis with this microenviroment. Both in vitro and in vivo it has been shown that tumor formation and metastatic properties are linked to epithelial-mesenchymal transition (EMT), a process by which facillitates the tumor cell's attempts to migrate to a more favourable microenviroment. Several groups have analyzed the gene expression in HCC and its surrounding tissue by microarray and this has resulted in the molecular classification into a distinct number of classes. Here we also found a role for hypoxia induced gene expression leading to a clinically more aggressive gene expression in HCC. Molecular analysis also helped to identify important cellular pathways and possible therapeutic targets. The first molecule that in this way has shown clinical application for liver cancer is the multikinase inhibitor sorafenib, others are currently in different stages of clinical studies like the mTOR inhibitor everolimus.

Immunohistochemical staining of cancer stem cell markers in hepatocellular carcinoma

BACKGROUND

Cancer stem cells (CSCs) are thought to be a critical subpopulation in tumor development, progression, metastasis and recurrence, and the identification of these cells is an initial step in understanding their role in oncogenesis and in seeking valuable markers for diagnosis or development of targeting therapeutics.

AIMS

To identify CSCs in hepatocellular carcinoma (HCC) specimens and define their tissue specificity.

METHODS

Immunohistochemical staining of CSC markers: CD44, CD90, CD133 and aldehyde dehydrogenase (ALDH) was performed in 25 HCC specimens, 4 hepatoblastomas, 8 peri-malignant tissues, and 19 cases of viral hepatitis.

RESULTS

The positivity of CD44 staining in HCC specimens was significantly lower than in viral hepatitis specimens. The positive rate of CD133 in HCC was similar to viral hepatitis specimens. CD133(+) cells were largely localized to ALDH-positive cells in HCC as revealed by confocal microscopy. In contrast, the co-expression of both markers was visualized within vessels or in the portal areas in viral hepatitis. Moreover, among 7 liver specimens adjacent to HCC tissue, 3-6 samples were positive for CD44, CD90, CD133 and ALDH, especially in dysplastic cells. One of 4 hepatoblastoma cases was positive for all these markers; whereas, the other three specimens were negative for all these CSC markers.

CONCLUSIONS

In HCC and dysplastic tissues, clusters of CD133(+)/ALDH(high) cells were identified. The use of cancer stem cell markers to screen tissues with chronic liver diseases provides limited guidance in the identification of malignant cells.