Stem cells in hepatocarcinogenesis: evidence from genomic data

Biomarkers in Cancer Detection, Diagnosis, and Prognosis

Biomarkers are vital in healthcare as they provide valuable insights into disease diagnosis, prognosis, treatment response, and personalized medicine. They serve as objective indicators, enabling early detection and intervention, leading to improved patient outcomes and reduced costs. Biomarkers also guide treatment decisions by predicting disease outcomes and facilitating individualized treatment plans. They play a role in monitoring disease progression, adjusting treatments, and detecting early signs of recurrence. Furthermore, biomarkers enhance drug development and clinical trials by identifying suitable patients and accelerating the approval process. In this review paper, we described a variety of biomarkers applicable for cancer detection and diagnosis, such as imaging-based diagnosis (CT, SPECT, MRI, and PET), blood-based biomarkers (proteins, genes, mRNA, and peptides), cell imaging-based diagnosis (needle biopsy and CTC), tissue imaging-based diagnosis (IHC), and genetic-based biomarkers (RNAseq, scRNAseq, and spatial transcriptomics).

Acquired Resistance to Antiangiogenic Therapies in Hepatocellular Carcinoma Is Mediated by Yes-Associated Protein 1 Activation and Transient Expansion of Stem-Like Cancer Cells

Induction of neoangiogenesis is a hallmark feature during disease progression of hepatocellular carcinoma (HCC). Antiangiogenetic compounds represent a mainstay of therapeutic approaches; however, development of chemoresistance is observed in the majority of patients. Recent findings suggest that tumor-initiating cells (TICs) may play a key role in acquisition of resistance, but the exact relevance for HCC in this process remains to be defined. Primary and established hepatoma cell lines were exposed to long-term sorafenib treatment to model acquisition of resistance. Treatment effects on TICs were estimated by sphere-forming capacity in vitro, tumorigenicity in vivo, and flow cytometry. Adaptive molecular changes were assessed by whole transcriptome analyses. Compensatory mechanisms of resistance were identified and directly evaluated. Sustained antiproliferative effect following sorafenib treatment was observed in three of six HCC cell lines and was followed by rapid regrowth, thereby mimicking responses observed in patients. Resistant cells showed induction in sphere forming in vitro and tumor-initiating capacity in vivo as well as increased number of side population and epithelial cell adhesion molecule-positive cells. Conversely, sensitive cell lines showed consistent reduction of TIC properties. Gene sets associated with resistance and poor prognosis, including Hippo/yes-associated protein (YAP), were identified. Western blot and immunohistochemistry confirmed increased levels of YAP. Combined treatment of sorafenib and specific YAP inhibitor consistently revealed synergistic antioncogenic effects in resistant cell lines. Conclusion: Resistance to antiangiogenic therapy might be driven by transient expansion of TICs and activation of compensatory pro-oncogenic signaling pathways, including YAP. Specific targeting of TICs might be an effective therapeutic strategy to overcome resistance in HCC.

Chronic alcohol exposure induces hepatocyte damage by inducing oxidative stress, SATB2 and stem cell‐like characteristics, and activating lipogenesis

Alcohol is a risk factor for hepatocellular carcinoma (HCC). However, the molecular mechanism by which chronic alcohol consumption contributes to HCC is not well understood. The purpose of the study was to demonstrate the effects of chronic ethanol exposure on the damage of human normal hepatocytes. Our data showed that chronic exposure of hepatocytes with ethanol induced changes similar to transformed hepatocytes that is, exhibited colonies and anchorage‐independent growth. These damaged hepatocytes contained high levels of reactive oxygen species (ROS) and showed induction of the SATB2 gene. Furthermore, damaged hepatocytes gained the phenotypes of CSCs which expressed stem cell markers (CD133, CD44, CD90, EpCAM, AFP and LGR5), and pluripotency maintaining factors (Sox‐2, POU5F1/Oct4 and KLF‐4). Ethanol exposure also induced Nanog, a pluripotency maintaining transcription factor that functions in concert with Oct4 and SOX‐2. Furthermore, ethanol induced expression of EMT‐related transcription factors (Snail, Slug and Zeb1), N‐Cadherin, and inhibited E‐cadherin expression in damaged hepatocytes. Ethanol enhanced recruitment of SATB2 to promoters of Bcl‐2, Nanog, c‐Myc, Klf4 and Oct4. Ethanol also induced activation of the Wnt/TCF‐LEF1 pathway and its targets (Bcl‐2, Cyclin D1, AXIN2 and Myc). Finally, ethanol induced hepatocellular steatosis, SREBP1 transcription, and modulated the expression of SREBP1c, ACAC, ACLY, FASN, IL‐1β, IL‐6, TNF‐α, GPC3, FLNB and p53. These data suggest that chronic alcohol consumption may contribute towards the development of HCC by damaging normal hepatocytes with the generation of inflammatory environment, induction of SATB2, stem cell‐like characteristics, and cellular steatosis.

The interplay of UBE2T and Mule in regulating Wnt/β-catenin activation to promote hepatocellular carcinoma progression

Emerging evidence indicates the role of cancer stem cells (CSCs) in tumor relapse and therapeutic resistance in patients with hepatocellular carcinoma (HCC). To identify novel targets against liver CSCs, an integrative analysis of publicly available datasets involving HCC clinical and stemness-related data was employed to select genes that play crucial roles in HCC via regulation of liver CSCs. We revealed an enrichment of an interstrand cross-link repair pathway, in which ubiquitin-conjugating enzyme E2 T (UBE2T) was the most significantly upregulated. Consistently, our data showed that UBE2T was upregulated in enriched liver CSC populations. Clinically, UBE2T overexpression in HCC was further confirmed at mRNA and protein levels and was correlated with advanced tumor stage and poor patient survival. UBE2T was found to be critically involved in the regulation of liver CSCs, as evidenced by increases in self-renewal, drug resistance, tumorigenicity, and metastasis abilities. Mule, an E3 ubiquitin ligase, was identified to be the direct protein binding partner of UBE2T. Rather than the canonical role of acting as a mediator to transfer ubiquitin to E3 ligases, UBE2T is surprisingly able to physically bind and regulate the protein expression of Mule via ubiquitination. Mule was found to directly degrade β-catenin protein, and UBE2T was found to mediate liver CSC functions through direct regulation of Mule-mediated β-catenin degradation; this effect was abolished when the E2 activity of UBE2T was impaired. In conclusion, we revealed a novel UBE2T/Mule/β-catenin signaling cascade that is involved in the regulation of liver CSCs, which provides an attractive potential therapeutic target for HCC.

Anti-oncogenic activities exhibited by paracrine factors of MSCs can be mediated by modulation of KITLG and DKK1 genes in glioma SCs in vitro

Cancer stem cells (CSCs) use their stemness properties to perpetuate their lineage and survive chemotherapy. Currently cell-based and cell-free therapies are under investigation to develop novel anti-cancer treatment modalities. We designed this study to investigate how cell extracts of mesenchymal stem cells affect the growth of glioma stem cells in vitro. Gliospheres were generated from the U87MG cell line and treated with conditioned media of Wharton’s jelly and bone marrow mesenchymal stem cells. The effects were investigated at the functional and molecular levels. Our results showed that conditioned media from both types of mesenchymal stem cells changed the morphology of spheres and inhibited the proliferation, invasion, and self-renewal ability of glioma stem cells. At the molecular level, metabolism interruption at oxidative phosphorylation, cell cycle arrest, cell differentiation, and upregulation of the immune response were observed. Furthermore, this effect was mediated by the upregulation of the DKK1 gene inhibiting the Wnt pathway mediated by growth factor activity and downregulation of the KITLG gene activated by growth factor and cytokine activity, inhibiting multiple pathways. We conclude that different types of mesenchymal stem cells possess antitumor properties and their paracrine factors, in combination with anti-immune modalities, can provide practical therapeutic targets for glioblastoma treatment.

NASH, Fibrosis and Hepatocellular Carcinoma: Lipid Synthesis and Glutamine/Acetate Signaling

Primary liver cancer is predicted to be the sixth most common cancer and the fourth leading cause of cancer mortality worldwide. Recent studies identified nonalcoholic fatty liver disease (NAFLD) as the underlying cause in 13-38.2% of patients with hepatocellular carcinoma unrelated to viral hepatitis and alcohol abuse. NAFLD progresses to nonalcoholic steatohepatitis (NASH), which increases the risk for the development of liver fibrosis, cirrhosis, and hepatocellular carcinoma. NAFLD is characterized by dysregulation of lipid metabolism. In addition, lipid metabolism is effected not only in NAFLD, but also in a broad range of chronic liver diseases and tumor development. Cancer cells manipulate a variety of metabolic pathways, including lipid metabolism, in order to build up their own cellular components. Identifying tumor dependencies on lipid metabolism would provide options for novel targeting strategies. This review article summarizes the research evidence on metabolic reprogramming and focuses on lipid metabolism in NAFLD, NASH, fibrosis, and cancer. As alternative routes of acetyl-CoA production for fatty acid synthesis, topics on glutamine and acetate metabolism are included. Further, studies on small compound inhibitors targeting lipid metabolism are discussed. Understanding reprogramming strategies in liver diseases, as well as the visualization of the metabolism reprogramming networks, could uncover novel therapeutic options.

Stem Cell Differentiation Stage Factors and their Role in Triggering Symmetry Breaking Processes during Cancer Development: A Quantum Field Theory Model for Reprogramming Cancer Cells to Healthy Phenotypes

A long history of research has pursued the use of embryonic factors isolated during cell differentiation processes for the express purpose of transforming cancer cells back to healthy phenotypes. Recent results have clarified that the substances present at different stages of cell differentiation-which we call stem cell differentiation stage factors (SCDSFs)-are proteins with low molecular weight and nucleic acids that regulate genomic expression. The present review summarizes how these substances, taken at different stages of cellular maturation, are able to retard proliferation of many human tumor cell lines and thereby reprogram cancer cells to healthy phenotypes. The model presented here is a quantum field theory (QFT) model in which SCDSFs are able to trigger symmetry breaking processes during cancer development. These symmetry breaking processes, which lie at the root of many phenomena in elementary particle physics and condensed matter physics, govern the phase transitions of totipotent cells to higher degrees of diversity and order, resulting in cell differentiation. In cancers, which share many genomic and metabolic similarities with embryonic stem cells, stimulated redifferentiation often signifies the phenotypic reversion back to health and nonproliferation. In addition to acting on key components of the cellular cycle, SCDSFs are able to reprogram cancer cells by delicately influencing the cancer microenvironment, modulating the electrochemistry and thus the collective electrodynamic behaviors between dipole networks in biomacromolecules and the interstitial water field. Coherent effects in biological water, which are derived from a dissipative QFT framework, may offer new diagnostic and therapeutic targets at a systemic level, before tumor instantiation occurs in specific tissues or organs. Thus, by including the environment as an essential component of our model, we may push the prevailing paradigm of mutation-driven oncogenesis toward a closer description of reality.

C-terminal truncated hepatitis B virus X protein promotes hepatocellular carcinogenesis through induction of cancer and stem cell-like properties

Tumor relapse after chemotherapy typifies hepatocellular carcinoma (HCC) and is believed to be attributable to residual cancer stem cells (CSCs) that survive initial treatment. Chronic infection with hepatitis B virus (HBV) has long been linked to the development of HCC. Upon infection, random HBV genome integration can lead to truncation of hepatitis B virus X (HBx) protein at the C-terminus. The resulting C-terminal-truncated HBx (HBx-ΔC) was previously shown to confer enhanced invasiveness and diminished apoptotic response in HCC cells. Here, we found HBx-ΔC to promote the appearance of a CD133 liver CSC subset and confer cancer and stem cell-like features in HCC. HBx-ΔC was exclusively detected in HCC cell lines that were raised from patients presented with a HBV background with concomitant CD133 expression. Stable overexpression of the naturally occurring HBx-ΔC mutants, HBx-Δ14 or HBx-Δ35, in HCC cells Huh7 and immortalized normal liver cells MIHA resulted in a significant increase in the cells ability to self-renew, resist chemotherapy and targeted therapy, migrate and induce angiogenesis. MIHA cells with the mutants stably overexpressed also resulted in the induction of CD133, mediated through STAT3 activation. RNA sequencing profiling of MIHA cells with or without HBx-ΔC mutants stably overexpressed identified altered FXR activation. This, together with rescue experiments using a selective FXR inhibitor suggested that C-terminal truncated HBx can mediate cancer stemness via FXR activation. Collectively, we find C-terminal truncated HBx mutants to confer cancer and stem cell-like features in vitro and to play an important role in driving tumor relapse in HCC.

Cripto-1 contributes to stemness in hepatocellular carcinoma by stabilizing Dishevelled-3 and activating Wnt/β-catenin pathway

Identification and characterization of functional molecular targets conferring stemness properties in hepatocellular carcinoma (HCC) offers crucial insights to overcome the major hurdles of tumor recurrence, metastasis and chemoresistance in clinical management. In the current study, we investigated the significance of Cripto-1 in contributing to HCC stemness. Cripto-1 was upregulated in the sorafenib-resistant clones derived from HCC cell lines and patient-derived xenograft that we previously developed, suggesting an association between Cripto-1 and stemness. By in vitro experiments, Cripto-1 fostered cell proliferation, migration, and invasion. It also enhanced self-renewal ability and conferred chemoresistance of HCC cells. Consistently, silencing of Cripto-1 suppressed in vivo tumorigenicity on serial transplantation. On the downstream signaling mechanism, expression of major components of Wnt/β-catenin pathway β-catenin, AXIN2, and C-MYC, accompanied by β-catenin activity was reduced upon Cripto-1 knockdown. The suppressive effects on stemness properties with Cripto-1 knockdown in vitro and in vivo were partially rescued by forced expression of constitutively active β-catenin. Further elucidation revealed the binding of Cripto-1 to Frizzled-7 (FZD7), low-density lipoprotein receptor-related protein 6 (LRP6) and Dishevelled-3 (DVL3) of the Wnt/β-catenin pathway and stabilized DVL3 protein. Analyses with clinical samples validated Cripto-1 overexpression in HCC tissues, as well as a positive correlation between Cripto-1 and AXIN2 expressions. High Cripto-1 level in tumor was associated with poorer disease-free survival of HCC patients. Taken together, Cripto-1 binds to FZD7/LRP6 and DVL3, stabilizes DVL3 expression and activates the Wnt/β-catenin signaling cascade to confer stemness in HCC. Our study findings substantiated the role of Cripto-1 in determining stemness phenotypes of HCC and mechanistically in modulating the Wnt/β-catenin signaling cascade, one of the most frequently deregulated pathways in liver cancer.

C-terminal truncated hepatitis B virus X protein regulates tumorigenicity, self-renewal and drug resistance via STAT3/Nanog signaling pathway

Hepatitis B virus (HBV) is a major risk factor of chronic liver disease and hepatocellular carcinoma (HCC). Random integration of HBV DNA into the host genome is frequent in HCC leading to truncation of the HBV DNA, particularly at the C-terminal end of the HBV X protein (HBx). C-terminally truncated HBx (HBx-ΔC) has been implicated in playing a pro-oncogenic role in hepatocarcinogenesis. However, the mechanism whereby HBx-ΔC1 contributes to hepatocarcinogenesis remains unclear. In this study, we investigated the functional role of HBx-ΔC1 in regulating liver cancer stem cell (CSC) properties. Using Tet-on inducible system, we found that HBx-ΔC1 enhanced CSC properties including self-renewal, tumorigenicity, chemoresistance, migration and expression of liver CSC markers, when compared with the full-length HBx counterpart and vector control. Interestingly, HBx-ΔC1 conferred resistance in HCC cells towards sorafenib treatment through suppression of apoptotic cascade. In addition, HBx-ΔC1 upregulated a panel of stemness genes, in which Nanog was found to be among the most significant one in both trasnfected cell lines. Consistently, Nanog was upregulated in human HCC samples which had HBx-ΔC1 expression. Furthermore, the induction of CSC properties by HBx-ΔC1 was via the Stat3/Nanog pathway, as administration of Stat3 inhibitor abolished the HBx-ΔC1-induced self-renewing capacity. In conclusion, our data suggest that HBx-ΔC1 enhances liver CSCs properties through Stat3/Nanog cascade, and provide a new insight for the therapeutic intervention for HBV-related HCC.

Variation of stemness markers expression in tumor nodules from synchronous multi-focal hepatocellular carcinoma - an immunohistochemical study

Background

Advancing knowledge in molecular pathogenesis of hepatocellular carcinoma (HCC) opens up new horizons in the diagnostic, prognostic and therapeutic perspectives. Assessing the expression of molecular targets prior to definitive treatment is gaining importance in clinical practice. In this study, we investigated the variation in expression pattern of stemness markers in synchronous multi-focal HCC.

Methods

In the first cohort, 21 liver explants with multi-focal HCC were examined for expression of stemness markers EpCAM, Sox9 and CK19 by immunohistochemistry (IHC). Expression data of 50 tumor nodules were analyzed to determine the concordance of expression among nodules in the same livers. In the second cohort, 14 tumor nodules from 6 multi-focal HCC cases proven as intra-hepatic metastasis were examined for Soc9 immunoexpression.

Results

In the first cohort, thirty nodules from 16 cases expressed one or more markers, with Sox9 being most frequently expressed. Complete concordance of expression pattern for all 3 markers was observed in 6 cases. Discrepancy of staining degree was noted in 4 cases for EpCAM, 14 cases for Sox9, and 6 cases for CK19. A two-tier or three-tier difference in staining scores was noted in 5 cases for Sox9 and one case for CK19. With Sox9, identical tumor morphology in terms of Edmondson grading and growth pattern did not infer the same degree of immunoexpression; and the largest tumor nodule was not representative of highest IHC score. In the second cohort of intra-hepatic metastasis, complete concordance of Sox9 expression level was observed in 5 out of 6 cases; while the remaining case showed a 1-tier difference of positive staining.

Conclusions

Our findings suggested that clonality of tumor nodules is apparently an important factor to infer immunoexpression pattern. When there is limited information to discern multiple primaries versus intra-hepatic metastasis in multi-focal HCC, discordant degree of stemness markers expression among tumor nodules was commonly observed especially for markers with higher frequency of expression. Pathological features alone do not necessarily indicate the expression pattern of the synchronous nodule and in this scenario examination of each tumor nodule is justified.

Autocrine Human Growth Hormone Promotes Invasive and Cancer Stem Cell-Like Behavior of Hepatocellular Carcinoma Cells by STAT3 Dependent Inhibition of CLAUDIN-1 Expression

Despite progress in diagnosis and treatment of hepatocellular carcinoma (HCC), the clinical outcome is still unsatisfactory. Increased expression of human growth hormone (hGH) in HCC has been reported and is associated with poor survival outcome in HCC patients. Herein, we investigated the mechanism of the oncogenic effects of hGH in HCC cell lines. In vitro functional assays demonstrated that forced expression of hGH in these HCC cell lines promoted cell proliferation, cell survival, anchorage-independent growth, cell migration, and invasion, as previously reported. In addition, forced expression of hGH promoted cancer stem cell (CSC)-like properties of HCC cells. The increased invasive and CSC-like properties of HCC cells with forced expression of hGH were mediated by inhibition of the expression of the tight junction component CLAUDIN-1. Consistently, depletion of CLAUDIN-1 expression increased the invasive and CSC-like properties of HCC cell lines. Moreover, forced expression of CLAUDIN-1 abrogated the acquired invasive and CSC-like properties of HCC cell lines with forced expression of hGH. We further demonstrated that forced expression of hGH inhibited CLAUDIN-1 expression in HCC cell lines via signal transducer and activator of transcription 3 (STAT3) mediated inhibition of CLAUDIN-1 transcription. Hence, we have elucidated a novel hGH-STAT3-CLAUDIN-1 axis responsible for invasive and CSC-like properties in HCC. Inhibition of hGH should be considered as a therapeutic option to hinder progression and relapse of HCC.

The C-terminus domain of the hepatitis B virus x protein stimulates the proliferation of mouse foetal hepatic progenitor cells, although it is not required for the formation of spheroids

The hepatitis B virus X (HBx) protein is an important factor in hepatitis B virus (HBV)-associated hepatocellular carcinoma (HCC). The C-terminal region of HBx plays a major role in the replication of HBV. Notably, HBx promotes the expansion and tumourigenesis of hepatic progenitor cells (HPCs) in mice. However, it remains unclear as to whether the C-terminal region of HBx is required for the stimulation fo the proliferation of mouse foetal HPCs (FHPCs). In our study, we used EpCAM+, CD133+ and CD49f+ FHPCs, which are bipotential clonogenic cells. These FHPCs transformed into mature hepatocytes and cholangiocytes when cultured under conditions that facilitate differentiation. Compared with the FHPCs grown as monolayers, spherical cell proliferation occurred more rapidly. Furthermore, spherically cultured FHPCs can grow in semi-solid agar and tend to maintain the morphology and characteristics of stem cells compared with growth in rat tail collagen. Notably, we also demonstrate that the C-terminus of HBx stimulates the proliferation of FHPCs, but is not required for the formation of spheroids, similar to hepatic cancer stem cells. These findings enhance our understanding of the HBx-induced tumourigenicity of FHPCs and may aid in the treatment of HCC.

Zinc finger protein X-linked promotes expansion of EpCAM+ cancer stem-like cells in hepatocellular carcinoma

Zinc finger protein X-linked (ZFX) is frequently upregulated in multiple human malignancies and also plays a critical role in the maintenance of self-renewal in embryonic stem cells. However, the role of ZFX in liver cancer stem cells (CSCs) remains obscure. We observed that the elevated expression of both ZFX and epithelial cell adhesion molecule (EpCAM) was associated with aggressive clinicopathological features and indicated poor prognosis in patients with hepatocellular carcinoma (HCC). ZFX was commonly enriched in liver EpCAM+ CSCs. Knockdown of ZFX decreased the proportion of EpCAM+ CSCs in HCC cells and suppressed their expression of stemness-related genes, self-renewal capacity, chemoresistance, metastatic potential, and tumorigenicity. Conversely, upregulation of ZFX in CSCs rescued these inhibitory effects and enhanced stem-like properties. Mechanistically, depletion of ZFX reduced nuclear translocation and transactivation of β-catenin, thereby inhibiting the self-renewal capacity of EpCAM+ CSCs. Moreover, knockdown of β-catenin attenuated the self-renewal of EpCAM+ HCC cells stably expressing ZFX, further indicating that β-catenin is required for ZFX-mediated expansion and maintenance of EpCAM+ CSCs. Taken together, our findings indicate that ZFX activates and maintains EpCAM+ liver CSCs by promoting nuclear translocation and transactivation of β-catenin. Furthermore, combination of ZFX and EpCAM may serve as a significant indicator for prognosis of patients with HCC.

Hepatitis B virus PreS1 facilitates hepatocellular carcinoma development by promoting appearance and self-renewal of liver cancer stem cells

Hepatitis B virus (HBV) is a major etiologic agent of hepatocellular carcinoma (HCC). However, the molecular mechanism by which HBV infection contributes to HCC development is not fully understood. Here, we initially showed that HBV stimulates the production of cancer stem cells (CSCs)-related markers (CD133, CD117 and CD90) and CSCs-related genes (Klf4, Sox2, Nanog, c-Myc and Oct4) and facilitates the self-renewal of CSCs in human hepatoma cells. Cellular and clinical studies revealed that HBV facilitates hepatoma cell growth and migration, enhances white blood cell (WBC) production in the sera of patients, stimulates CD133 and CD117 expression in HCC tissues, and promotes the CSCs generation of human hepatoma cells and clinical cancer tissues. Detailed studies revealed that PreS1 protein of HBV is required for HBV-mediated CSCs generation. PreS1 activates CD133, CD117 and CD90 expression in normal hepatocyte derived cell line (L02) and human hepatoma cell line (HepG2 and Huh-7); facilitates L02 cells migration, growth and sphere formation; and finally enhances the abilities of L02 cells and HepG2 cells to induce tumorigeneses in nude mice. Thus, PreS1 acts as a new oncoprotein to play a key role in the appearance and self-renewal of CSCs during HCC development.

Liver cancer stem cells and new strategies for targeted therapy of hepatocellular carcinoma

Over the past ten years, increasing studies show that liver cancer stem cells (LCSCs) are responsible not only for hepatocellular carcinoma (HCC) initiation and development but also for the generation of distant metastasis and relapse after therapy. Therefore, further research for LCSCs is considered a new avenue to explore the cause of HCC invasion and metastasis in order to formulate prevention and control strategies. Current traditional cancer therapies including chemotherapy and radiotherapy which primarily target rapidly dividing and most likely well differentiated tumor cells, would fail to eliminate LCSCs. After surgical removal of HCC mass, the remaining LCSCs still have the ability to differentiate, proliferate and even migrate to other places to form metastatic tumors. Therefore, to explore various kinds of targeted therapies for LCSCs is the only way to break through the "bottleneck" of HCC treatment. Strategies for targeted therapy of HCC include inhibiting LCSCs proliferation, inducing apoptosis and differentiation, increasing chemotherapy sensitivity and disrupting the tumor niche essential for CSC homeostasis.

Stem Cell Differentiation Stage Factors from Zebrafish Embryo: A Novel Strategy to Modulate the Fate of Normal and Pathological Human (Stem) Cells

In spite of the growing body of evidence on the biology of the Zebrafish embryo and stem cells, including the use of Stem Cell Differentiation Stage Factors (SCDSFs) taken from Zebrafish embryo to impact cancer cell dynamics, comparatively little is known about the possibility to use these factors to modulate the homeostasis of normal human stem cells or to modulate the behavior of cells involved in different pathological conditions. In the present review we recall in a synthetic way the most important researches about the use of SCDSFs in reprogramming cancer cells and in modulating the high speed of multiplication of keratinocytes which is characteristic of some pathological diseases like psoriasis. Moreover we add here the results about the capability of SCDSFs in modulating the homeostasis of human adiposederived stem cells (hASCs) isolated from a fat tissue obtained with a novel-non enzymatic method and device. In addition we report the data not yet published about a first protein analysis of the SCDSFs and about their role in a pathological condition like neurodegeneration.

Functional and genetic deconstruction of the cellular origin in liver cancer

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

Pathogenesis and prognosis of hepatocellular carcinoma at the cellular and molecular levels

Different approaches predict the outcome for patients with hepatocellular carcinoma (HCC). The expression of biliary-hepatic progenitor cell markers generally correlates with poor prognosis. This article focuses on the pathogenesis of HCC, how differentiation or dedifferentiation leads to a phenotype switch, and heterogeneity in the same tumor. A tumor cell decides its fate based on a complex interplay of signaling pathways. Interaction with the microenvironment decides whether it will invade, proliferate, or enter survival mode. Several signaling pathways contribute to stemness features, reflecting a small chemoresistant subpopulation of the tumor that expresses biliary-hepatic progenitor cell markers.

Dynamic imbalance between cancer cell subpopulations induced by transforming growth factor beta (TGF-β) is associated with a DNA methylome switch

BACKGROUND

Distinct subpopulations of neoplastic cells within tumors, including hepatocellular carcinoma (HCC), display pronounced ability to initiate new tumors and induce metastasis. Recent evidence suggests that signals from transforming growth factor beta (TGF-β) may increase the survival of these so called tumor initiating cells leading to poor HCC prognosis. However, how TGF-β establishes and modifies the key features of these cell subpopulations is not fully understood.

RESULTS

In the present report we describe the differential DNA methylome of CD133-negative and CD133-expressing liver cancer cells. Next, we show that TGF-β is able to increase the proportion of CD133+ cells in liver cancer cell lines in a way that is stable and persistent across cell division. This process is associated with stable genome-wide changes in DNA methylation that persist through cell division. Differential methylation in response to TGF-β is under-represented at promoter CpG islands and enriched at gene bodies, including a locus in the body of the de novo DNA methyl-transferase DNMT3B gene. Moreover, phenotypic changes induced by TGF-β, including the induction of CD133, are impaired by siRNA silencing of de novo DNA methyl-transferases.

CONCLUSIONS

Our study reveals a self-perpetuating crosstalk between TGF-β signaling and the DNA methylation machinery, which can be relevant in the establishment of cellular phenotypes. This is the first indication of the ability of TGF-β to induce genome-wide changes in DNA methylation, resulting in a stable change in the proportion of liver cancer cell subpopulations.

The Rad50 hook domain regulates DNA damage signaling and tumorigenesis

The Mre11 complex (Mre11, Rad50, and Nbs1) is a central component of the DNA damage response (DDR), governing both double-strand break repair and DDR signaling. Rad50 contains a highly conserved Zn(2+)-dependent homodimerization interface, the Rad50 hook domain. Mutations that inactivate the hook domain produce a null phenotype. In this study, we analyzed mutants with reduced hook domain function in an effort to stratify hook-dependent Mre11 complex functions. One of these alleles, Rad50(46), conferred reduced Zn(2+) affinity and dimerization efficiency. Homozygous Rad50(46/46) mutations were lethal in mice. However, in the presence of wild-type Rad50, Rad50(46) exerted a dominant gain-of-function phenotype associated with chronic DDR signaling. At the organismal level, Rad50(+/46) exhibited hydrocephalus, liver tumorigenesis, and defects in primitive hematopoietic and gametogenic cells. These outcomes were dependent on ATM, as all phenotypes were mitigated in Rad50(+/46) Atm(+/-) mice. These data reveal that the murine Rad50 hook domain strongly influences Mre11 complex-dependent DDR signaling, tissue homeostasis, and tumorigenesis.

Identification of liver cancer progenitors whose malignant progression depends on autocrine IL-6 signaling

Hepatocellular carcinoma (HCC) is a slowly developing malignancy postulated to evolve from premalignant lesions in chronically damaged livers. However, it was never established that premalignant lesions actually contain tumor progenitors that give rise to cancer. Here, we describe isolation and characterization of HCC progenitor cells (HcPCs) from different mouse HCC models. Unlike fully malignant HCC, HcPCs give rise to cancer only when introduced into a liver undergoing chronic damage and compensatory proliferation. Although HcPCs exhibit a similar transcriptomic profile to bipotential hepatobiliary progenitors, the latter do not give rise to tumors. Cells resembling HcPCs reside within dysplastic lesions that appear several months before HCC nodules. Unlike early hepatocarcinogenesis, which depends on paracrine IL-6 production by inflammatory cells, due to upregulation of LIN28 expression, HcPCs had acquired autocrine IL-6 signaling that stimulates their in vivo growth and malignant progression. This may be a general mechanism that drives other IL-6-producing malignancies.

Colorectal cancer biomarkers and the potential role of cancer stem cells

Over 50% of patients with colorectal cancer (CRC) will progress and/or develop metastases. Biomarkers capable of predicting progression, risk stratification and therapeutic benefit are needed. Cancer stem cells are thought to be responsible for tumor initiation, dissemination and treatment failure. Therefore, we hypothesized that CRC stem cell markers (CRCSC) can identify a group of patients whom are at increased risk for recurrence or progression of disease. If proven correct, these CRCSC biomarkers may herald a paradigm shift in the treatment of this deadly disease. This manuscript reviews current CRC evidence based screening modalities, patient stratification, and summarizes the current state of biomarkers and discusses the novel concept of putative CRCSC's as prognostic biomarkers.

Role of the microenvironment in the pathogenesis and treatment of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the most common primary liver tumor and the third greatest cause of cancer-related death worldwide, and its incidence is increasing. Despite the significant improvement in management of HCC over the past 30 years, there are no effective chemoprevention strategies, and only one systemic therapy has been approved for patients with advanced tumors. This drug, sorafenib, acts on tumor cells and the stroma. HCC develops from chronically damaged tissue that contains large amounts of inflammation and fibrosis, which also promote tumor progression and resistance to therapy. Increasing our understanding of how stromal components interact with cancer cells and the signaling pathways involved could help identify new therapeutic and chemopreventive targets.

Molecular mechanisms of fibrosis-associated promotion of liver carcinogenesis

Hepatocellular carcinoma (HCC) mostly develops in patients with advanced fibrosis; however, the mechanisms of interaction between a genotoxic insult and fibrogenesis are not well understood. This study tested a hypothesis that fibrosis promotes HCC via a mechanism that involves activation of liver stem cells. First, B6C3F1 mice were administered diethylnitrosamine (DEN; single ip injection of 1mg/kg at 14 days of age). Second, carbon tetrachloride (CCl(4); 0.2ml/kg, 2/week ip starting at 8 weeks of age) was administered for 9 or 14 weeks to develop advanced liver fibrosis. In animals treated with DEN as neonates, presence of liver fibrosis led to more than doubling (to 100%) of the liver tumor incidence as early as 5 months of age. This effect was associated with activation of cells with progenitor features in noncancerous liver tissue, including markers of replicative senescence (p16), oncofetal transformation (Afp, H19, and Bex1), and increased "stemness" (Prom1 and Epcam). In contrast, the dose of DEN used did not modify the extent of liver inflammation, fibrogenesis, oxidative stress, proliferation, or apoptosis induced by subchronic CCl(4) administration. This study demonstrates the potential role of liver stem-like cells in the mechanisms of chemical-induced, fibrosis-promoted HCC. We posit that the combination of genotoxic and fibrogenic insults is a sensible approach to model liver carcinogenesis in experimental animals. These results may contribute to identification of cirrhotic patients predisposed to HCC by analyzing the expression of hepatic progenitor cell markers in the noncancerous liver tissue.

Comparative histomorphological review of rat and human hepatocellular proliferative lesions

In this comparative review, histomorphological features of common nonneoplastic and neoplastic hepatocyte lesions of rats and humans are examined using H&E-stained slides. The morphological similarities and differences of both neoplastic (hepatocellular carcinoma and hepatocellular adenoma) and presumptive preneoplastic lesions (large and small cell change in humans and foci of cellular alteration in rats) are presented and discussed. There are major similarities in the diagnostic features, growth patterns and behavior of both rat and human hepatocellular proliferative lesions and in the process of hepatocarcinogenesis. Further study of presumptive preneoplastic lesions in humans and rats should help to further define their role in progression to hepatocellular neoplasia in both species.

A Pilot Study Assessing the Potential Role of non-CD133 Colorectal Cancer Stem Cells as Biomarkers

Introduction: Over 50% of patients with colorectal cancer (CRC) will progress and/or develop metastases. Biomarkers capable of predicting progression, risk stratification and therapeutic benefit are needed. Cancer stem cells are thought to be responsible for tumor initiation, dissemination and treatment failure. Therefore, we hypothesized that CRC cancer stem cell markers (CRCSC) will identify a group of patients at high risk for progression.

Methods: Paraffin-embedded tissue cores of normal (n=8), and histopathologically well-defined primary (n= 30) and metastatic (n=10) CRC were arrayed in duplicate on tissue microarrays (TMAs). Expression profiles of non-CD133 CRCSC (CD29, CD44, ALDH1A1, ALDH1B1, EpCam, and CD166) were detected by immunohistochemistry and the association with clinicopathological data and patient outcomes was determined using standard statistical methodology. An independent pathologist, blinded to the clinical data scored the samples. Scoring included percent positive cells (0 to 4, 0 = <10%, 1 = 10 - 24%, 2 = 25 - 49%, 3 = 50 - 74%, 4 = 75 - 100%), and the intensity of positively stained cells (0 to 4; 0 = no staining, 1 = diminutive intensity, 2 = low intensity, 3 = intermediate intensity, 4 = high intensity). The pathologic score represents the sum of these two values, reported in this paper as a combined IHC staining score (CSS).

Results: Of 30 patients 7 were AJCC stage IIA, 10 stage IIIB, 7 stage IIIC and 6 stage IV. Median follow-up was 113 months. DFI was 17 months. Median overall survival (OS) was not reached. Stage-specific OS was: II - not reached; III - not reached; IV - 11 months. In a univariate analysis, poor OS was associated with loss of CD29 expression; median OS, 32 months vs. not reached for CSS 3-7 vs. >7.5, respectively; p=0.052 comparing entire curves, after adjustment. In a Cox model analysis, loss of CD29 exhibited a trend toward association with survival (p=0.098) after adjusting for the effect of stage (p=0.0076). Greater expression of ALDH1A1 was associated with increasing stage (p=0.042 over stages 2, 3b, 3c, and 4) while loss of CD29 expression exhibited a trend toward being associated with stages 3 and 4 (p=0.08). Compared to normal colon tissue, primary tumors were associated with increased expression of ALDH1B1 (p=0.008). ALD1H1B1 expression level differed according to whether the tumor was moderately or poorly differentiated, well differentiated, or mucinous; the highest expression levels were associated with moderately or poorly differentiated tumors (p=0.011). Lymph node metastases were associated with a trend toward decreased expression of EpCAM (p = 0.06) when comparing 0 vs. 1 vs. 2+ positive lymph nodes, as was CD29 (p = 0.08) when comparing 0 vs. any positive lymph nodes. Compared to normal colon tissue metastatic colon cancers from different patients were associated with increased ALDH1B1 expression (p=0.001) whereas CD29 expression was higher in normal colonic tissue (p=0.014).

Conclusion: CD29 may be associated with survival as well as clinical stage and number of lymph nodes. ALDH1B1 expression was associated with differentiation as well as type of tissue evaluated. ALDH1A1 was associated with clinical stage, and decreased EpCAM expression was found in patients with advanced lymph node stage. CRCSCs may be useful biomarkers to risk stratify, and estimate outcomes in CRC. Larger prospective studies are required to validate the current findings.

Disruption of Trp53 in livers of mice induces formation of carcinomas with bilineal differentiation

BACKGROUND & AIMS

p53 limits the self-renewal of stem cells from various tissues. Loss of p53, in combination with other oncogenic events, results in aberrant self-renewal and transformation of progenitor cells. It is not known whether loss of p53 is sufficient to induce tumor formation in liver.

METHODS

We used AlfpCre mice to create mice with liver-specific disruption of Trp53 (AlfpCre(+)Trp53(Δ2-10/Δ2-10) mice). We analyzed colony formation and genomic features and gene expression patterns in liver cells during hepatocarcinogenesis in mice with homozygous, heterozygous, and no disruption of Trp53.

RESULTS

Liver-specific disruption of Trp53 consistently induced formation of liver carcinomas that had bilineal differentiation. In nontransformed liver cells and cultured primary liver cells, loss of p53 (but not p21) resulted in chromosomal imbalances and increased clonogenic capacity of liver progenitor cells (LPCs) and hepatocytes. Primary cultures of hepatocytes and LPCs from AlfpCre(+)Trp53(Δ2-10/Δ2-10) mice, but not Cdkn1a(-/-) mice, formed tumors with bilineal differentiation when transplanted into immunocompromised mice. Spontaneous liver tumors that developed in AlfpCre(+)Trp53(Δ2-10/Δ2-10) mice had significant but complex alterations in expression of Rb checkpoint genes compared with chemically induced liver tumors that developed mice with wild-type Trp53.

CONCLUSIONS

Deletion of p53 from livers of mice is sufficient to induce tumor formation. The tumors have bilineal differentiation and dysregulation of Rb checkpoint genes.

CD24(+) liver tumor-initiating cells drive self-renewal and tumor initiation through STAT3-mediated NANOG regulation

Tumor-initiating cells (T-ICs) are a subpopulation of chemoresistant tumor cells that have been shown to cause tumor recurrence upon chemotherapy. Identification of T-ICs and their related pathways are therefore priorities for the development of new therapeutic paradigms. We established chemoresistant hepatocellular carcinoma (HCC) xenograft tumors in immunocompromised mice in which an enriched T-IC population was capable of tumor initiation and self-renewal. With this model, we found CD24 to be upregulated in residual chemoresistant tumors when compared with bulk tumor upon cisplatin treatment. CD24(+) HCC cells were found to be critical for the maintenance, self-renewal, differentiation, and metastasis of tumors and to significantly impact patients' clinical outcome. With a lentiviral-based knockdown approach, CD24 was found to be a functional liver T-IC marker that drives T-IC genesis through STAT3-mediated NANOG regulation. Our findings point to a CD24 cascade in liver T-ICs that may provide an attractive therapeutic target for HCC patients.

Molecular diagnosis and therapy of hepatocellular carcinoma (HCC): an emerging field for advanced technologies

Despite great progress in diagnosis and management of hepatocellular carcinoma (HCC), the exact biology of the tumor remains poorly understood overall limiting the patients' outcome. Detailed analysis and characterization of the molecular mechanisms and subsequently individual prediction of corresponding prognostic traits would revolutionize both diagnosis and treatment of HCC and is the key goal of modern personalized medicine. Over the recent years systematic approaches for the analysis of whole tumor genomes and transcriptomes as well as epigenomes became affordable tools in translational research. This includes simultaneous analyses of thousands of molecular targets using microarray-based technologies as well as next-generation sequencing. Although currently diagnosis and classification of hepatocellular cancers still rely on histological examination of tumor sections, these technologies show great promise to advance the current knowledge of hepatocarcinogenesis, complement diagnostic classification in a setting of microarray-aided pathology, and rationalize the individual drug selection. This review aims to summarize recent progress of system biological approaches in hepatocarcinogenesis and outline potential areas for translational application in a clinical setting. Further, we give an update about known signaling pathways active in HCC, summarize the historical application of whole genomic approaches in liver cancer and indicate ongoing experimental research utilizing novel technologies in diagnosis and treatment of this deadly disease. This will also include the discussion and characterization of new molecular and cellular targets such as Cancer Stem Cells (CSCs).

Mixed phenotype hepatocellular carcinoma after transarterial chemoembolization and liver transplantation

We investigated the phenotype of hepatocellular carcinoma (HCC) in livers removed during transplantation after local ablation therapy by transarterial chemoembolization (TACE). This study involved 80 HCC nodules (40 treated with TACE and 40 not treated with local ablation before transplantation) observed in 64 explanted livers and included clinicopathological evaluations as well as single and double immunohistochemistry and reverse-transcription polymerase chain reaction (RT-PCR) for cytokeratin 19 (CK19), epithelial cell adhesion molecule (EpCAM), neural cell adhesion molecule (NCAM), and CD133. HCCs with complete necrosis post-TACE without viable tumors were excluded from the analysis. Cholangiolar, glandular, or spindle cell areas suggestive of a mixed hepatocholangiocellular phenotype were seen in 14 post-TACE HCCs and in none of the non-TACE HCCs (P < 0.001). According to single-epitope immunohistochemistry of post-TACE HCCs, CD133, CK19, EpCAM, and NCAM were expressed in 14 (35%), 8 (20%), 12 (30%), and 8 (20%), respectively. Only EpCAM was detected in 4 non-TACE HCC cases (10%). RT-PCR experiments using tissues obtained by laser microdissection showed that 4 of 5 investigated post-TACE HCCs expressed at least 1 of the markers, which were coexpressed in 3 of 5 tumors, whereas CD133 and EpCAM were individually expressed in 2 non-TACE HCCs. Double immunostaining showed that CD133(+) cells frequently coexpressed CK19, EpCAM, or NCAM. Interestingly, the recurrence rate for patients with CD133(+) post-TACE HCC was significantly higher than the rate for patients with CD133(-) post-TACE HCC (P = 0.025). In conclusion, HCC with the combined hepatocholangiocellular phenotype appears to be more frequent in post-TACE HCC versus untreated HCC. Further studies are needed to investigate the potential relationships between TACE and HCC subpopulations with a chemoembolization-resistant phenotype and their clinical significance.

Metastatic breast cancer cells in the bone marrow microenvironment: novel insights into oncoprotection

Among all cancers, malignancies of the breast are the second leading cause of cancer death in the United States after carcinoma of the lung. One of the major factors considered when assessing the prognosis of breast cancer patients is whether the tumor has metastasized to distant organs. Although the exact phenotype of the malignant cells responsible for metastasis and dormancy is still unknown, growing evidence has revealed that they may have stem cell-like properties that may account for resistance to chemotherapy and radiation. One process that has been attributed to primary tumor metastasis is the epithelial-to-mesenchymal transition. In this review, we specifically discuss breast cancer dissemination to the bone marrow and factors that ultimately serve to shelter and promote tumor growth, including the complex relationship between mesenchymal stem cells (MSCs) and various aspects of the immune system, carcinoma-associated fibroblasts, and the diverse components of the tumor microenvironment. A better understanding of the journey from the primary tumor site to the bone marrow and subsequently the oncoprotective role of MSCs and other factors within that microenvironment can potentially lead to development of novel therapeutic targets.

Does the hepatitis B antigen HBx promote the appearance of liver cancer stem cells?

Hepatitis B virus (HBV) is a major etiologic agent of chronic liver disease and hepatocellular carcinoma (HCC). HBV-encoded X antigen, HBx, and pathways implicated in the self-renewal of stem cells contribute to HCC, but it is not clear whether HBx expression promotes "stemness." Thus, experiments were designed to test the hypothesis that HBx triggers malignant transformation by promoting properties that are characteristic of cancer stem cells (CSC). To test this hypothesis, HepG2 cells were stably transduced with HBx and then assayed for phenotypic and molecular characteristics of "stemness." The relationship between HBx and "stemness"-associated markers was also evaluated by immunohistochemical staining of liver and tumor tissue sections from HBV-infected patients. The results showed that Oct-4, Nanog, Klf-4, β-catenin, and epithelial cell adhesion molecule (EpCAM) were activated by HBx in vitro and in vivo. EpCAM was detected in the nuclei of human HCC cells from infected patients. HBx promotes "stemness" by activating β-catenin and epigenetic upregulation of miR-181, both of which target EpCAM. HBx expression was also associated with depressed levels of E-cadherin. Moreover, HBx stimulated cell migration, growth in soft agar, and spheroid formation. This work is the first to propose that HBV promotes "stemness" in the pathogenesis of HCC. HBx-associated upregulated expression of multiple "stemness" markers supports the hypothesis that HBx contributes to hepatocarcinogenesis, at least in part, by promoting changes in gene expression that are characteristics of CSCs.

CD13: Waving the flag for a novel cancer stem cell target

Cancer stem cells (CSCs) are generally dormant or slowly cycling tumor cells that have the ability to reconstitute tumors. They are thought to be involved in tumor resistance to chemo/radiation therapy and tumor relapse and progression. However, neither their existence nor their identity within many cancers has been well defined. Here, we have demonstrated that CD13 is a marker for semiquiescent CSCs in human liver cancer cell lines and clinical samples and that targeting these cells might provide a way to treat this disease. CD13+ cells predominated in the G0 phase of the cell cycle and typically formed cellular clusters in cancer foci. Following treatment, these cells survived and were enriched along the fibrous capsule where liver cancers usually relapse. Mechanistically, CD13 reduced ROS-induced DNA damage after genotoxic chemo/radiation stress and protected cells from apoptosis. In mouse xenograft models, combination of a CD13 inhibitor and the genotoxic chemotherapeutic fluorouracil (5-FU) drastically reduced tumor volume compared with either agent alone. 5-FU inhibited CD90+ proliferating CSCs, some of which produce CD13+ semiquiescent CSCs, while CD13 inhibition suppressed the self-renewing and tumor-initiating ability of dormant CSCs. Therefore, combining a CD13 inhibitor with a ROS-inducing chemo/radiation therapy may improve the treatment of liver cancer.

Epigenetic regulation of cancer stem cells in liver cancer: current concepts and clinical implications

The two dominant models of carcinogenesis postulate stochastic (clonal evolution) or hierarchic organization of tumor (cancer stem cell model). According to the latter, at the germinal center of tumor evolution is a cancer stem cell (CSC) which, similar to normal adult stem cells, possesses the capacity of self-renewal and a differentiation potential. Over the past few years, compelling evidence has emerged in support of the hierarchic cancer model for many solid tumors including hepatocellular cancers. The CSCs are posited to be responsible not only for tumor initiation but also for the generation of distant metastasis and relapse after therapy. These characteristics are particularly relevant for a multi-resistant tumor entity like human hepatocellular carcinoma and may herald a paradigm shift in the management of this deadly disease. Identification and detailed characterization of liver CSCs is therefore imperative for improving prevention approaches, enhancing early detection, and extending the limited treatment options. Despite the current progress in understanding the contribution of CSCs to the generation of heterogeneity of tumors, the molecular complexity and exact regulation of CSCs is poorly understood. This review focuses on the genetic and epigenetic mechanisms that regulate and define the unique CSC properties with an emphasis on key regulatory pathways of liver CSCs and their clinical significance.