Liver cancer stem cells: implications for a new therapeutic target

Inhibition of Liver Cancer Cell Viability by Triazole through Up-regulation of p38 Phosphorylation and Targeting the Activation of p-ERK1/2 and Akt Protein Expression

The present study was aimed to explore the effect of triazole on growth and viability of liver cancer cells. Cell growth was examined using the MTT test and expression of several proteins was assessed by western blotting assay. The Matrigel-coated Transwell assay was employed to examine the infiltration of cells. The data from MTT assay showed that MHCC97H and H4TG liver cancer cell viability was inhibited by triazole in a concentration-dependent manner. After treatment with 0.5, 1.0, 2.0, 4, 8, and 16 µM doses of triazole, the rate of H4TG cell viability was decreased to 96, 73, 58, 39, 29, and 28%, respectively. Treatment of MHCC97H cells with 0.5, 1.0, 2.0, 4, 8, and 16 µM doses of triazole resulted in a reduction in cell viability to 94, 70, 53, 35, 22, and 21%, respectively. Triazole treatment also led to a significant reduction in MHCC97H cell invasiveness compared to the control cells. In MHCC97H cells treated with triazole, there was a noticeable decrease in the levels of p-ERK1/2, and p-Akt protein expression. Treatment of MHCC97H cells with triazole resulted in a prominent increase in p-p38 level. In summary, triazole inhibits growth and viability of liver cancer cells through targeting the activation of p-ERK1/2 and Akt proteins. Therefore, triazole may be investigated further as a therapeutic agent for the treatment of liver cancer.

Extracellular Matrix Cues Regulate Mechanosensing and Mechanotransduction of Cancer Cells

Extracellular biophysical properties have particular implications for a wide spectrum of cellular behaviors and functions, including growth, motility, differentiation, apoptosis, gene expression, cell-matrix and cell-cell adhesion, and signal transduction including mechanotransduction. Cells not only react to unambiguously mechanical cues from the extracellular matrix (ECM), but can occasionally manipulate the mechanical features of the matrix in parallel with biological characteristics, thus interfering with downstream matrix-based cues in both physiological and pathological processes. Bidirectional interactions between cells and (bio)materials in vitro can alter cell phenotype and mechanotransduction, as well as ECM structure, intentionally or unintentionally. Interactions between cell and matrix mechanics in vivo are of particular importance in a variety of diseases, including primarily cancer. Stiffness values between normal and cancerous tissue can range between 500 Pa (soft) and 48 kPa (stiff), respectively. Even the shear flow can increase from 0.1-1 dyn/cm2 (normal tissue) to 1-10 dyn/cm2 (cancerous tissue). There are currently many new areas of activity in tumor research on various biological length scales, which are highlighted in this review. Moreover, the complexity of interactions between ECM and cancer cells is reduced to common features of different tumors and the characteristics are highlighted to identify the main pathways of interaction. This all contributes to the standardization of mechanotransduction models and approaches, which, ultimately, increases the understanding of the complex interaction. Finally, both the in vitro and in vivo effects of this mechanics-biology pairing have key insights and implications for clinical practice in tumor treatment and, consequently, clinical translation.

Cellular and Molecular Biology of Cancer Stem Cells of Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is one of the leading causes of cancer death globally. The cancer stem cells (CSCs) of HCC are responsible for tumor growth, invasion, metastasis, recurrence, chemoresistance, target therapy resistance and radioresistance. The reported main surface markers used to identify liver CSCs include epithelial cell adhesion/activating molecule (EpCAM), cluster differentiation 90 (CD90), CD44 and CD133. The main molecular signaling pathways include the Wnt/β-catenin, transforming growth factors-β (TGF-β), sonic hedgehog (SHH), PI3K/Akt/mTOR and Notch. Patients with EpCAM-positive alpha-fetoprotein (AFP)-positive HCC are usually young but have advanced tumor-node-metastasis (TNM) stages. CD90-positive HCCs are usually poorly differentiated with worse prognosis. Those with CD44-positive HCC cells develop early metastases. Those with CD133 expression have a higher recurrence rate and a shorter overall survival. The Wnt/β-catenin signaling pathway triggers angiogenesis, tumor infiltration and metastasis through the enhancement of angiogenic factors. All CD133+ liver CSCs, CD133+/EpCAM+ liver CSCs and CD44+ liver CSCs contribute to sorafenib resistance. SHH signaling could protect HCC cells against ionizing radiation in an autocrine manner. Reducing the CSC population of HCC is crucial for the improvement of the therapy of advanced HCC. However, targeting CSCs of HCC is still challenging.

Biological role of matrix stiffness in tumor growth and treatment

In recent years, the biological role of changes in physical factors in carcinogenesis and progression has attracted increasing attention. Matrix stiffness, also known as ECM stress, is a critical physical factor of tumor microenvironment and remains alternating during carcinogenesis as a result of ECM remodeling through activation of cancer-associated fibroblasts and extracellular collagen accumulation, crosslinking and fibrosis. Different content and density of extracellular collagen in ECM endows matrix with varying stiffness. Physical signals induced by matrix stiffness are transmitted to tumor cells primarily by the integrins receptor family and trigger a series of mechanotransduction that result in changes in tumor cell morphology, proliferative capacity, and invasive ability. Importantly, accumulating evidence revealed that changes in matrix stiffness in tumor tissues greatly control the sensitivity of tumor cells in response to chemotherapy, radiotherapy, and immunotherapy through integrin signaling, YAP signaling, and related signaling pathways. Here, the present review analyzes the current research advances on matrix stiffness and tumor cell behavior with a view to contributing to tumor cell growth and treatment, with the hope of improving the understanding of the biological role of matrix stiffness in tumors.

Matrix Stiffness Potentiates Stemness of Liver Cancer Stem Cells Possibly via the Yes-Associated Protein Signal

A hepatocellular carcinoma tissue has mechanical heterogeneity, where the stiffness gradually increases from the core to the invasion front. Furthermore, there is evidence that stem cells from liver cancer (LCSCs) preferentially enrich the invasion front, exhibiting the stiffest modulus in the tumor. LCSCs have the features of stem/progenitor cells and play a vital part in liver cancer development. However, whether matrix stiffness affects LCSC stemness remains unclear. Here, we established a three-dimensional hydrogel for culturing LCSCs to simulate the stiffness of the core and the invasion front of a liver cancer tissue. The results showed that a stiffer matrix (72.2 ± 0.90 kPa) significantly potentiated LCSC stemness as compared with a soft matrix (7.7 ± 0.41 kPa). Moreover, Yes-associated protein signaling might mediate this promotion. Together, our findings illustrate the relationship between matrix stiffness and LCSC stemness, which may aid the production of novel treatment approaches against liver cancer.

BMP9 Promotes an Epithelial Phenotype and a Hepatocyte-like Gene Expression Profile in Adult Hepatic Progenitor Cells

Bone morphogenetic protein 9 (BMP9), a member of the TGF-β superfamily, has emerged as a new player in chronic liver diseases (CLDs). Its levels increase in the fibrotic liver where it promotes fibrogenesis. It also regulates hepatic progenitor cells (oval cells in rodents), a cell population that contributes to repopulate the liver and recover functionality upon severe damage, but it can also be pro-fibrogenic, depending upon the hepatic microenvironment. Here we analyze the effect of chronic exposure to BMP9 in oval cells. We show that cells chronically treated with BMP9 (B9T-OC) display a more epithelial and hepatocyte-like phenotype while acquiring proliferative and survival advantages. Since our previous studies had revealed a functional crosstalk between BMP9 and the HGF/c-Met signaling pathways in oval cells, we analyzed a possible role for HGF/c-Met in BMP9-induced long-term effects. Data evidence that active c-Met signaling is necessary to obtain maximum effects in terms of BMP9-triggered hepatocytic differentiation potential, further supporting functionally relevant cooperation between these pathways. In conclusion, our work reveals a novel action of BMP9 in liver cells and helps elucidate the mechanisms that serve to increase oval cell regenerative potential, which could be therapeutically modulated in CLD.

Inhibition of Liver Cancer Cell Growth by Triethylsilyl Resveratrol through Targeting Phosphoinositide-3 Kinase Pathway

Liver cancer is one of the commonly detected malignancy and third highest cause of deaths caused by cancer worldwide. The current study investigated the effect of triethylsilyl resveratrol on HuH7 and hep3B cell proliferation and explored the underlying mechanism. The viability of HuH7 and hep3B cells was suppressed to 23 and 18%, respectively on exposure to 2 µM triethylsilyl resveratrol for 72 h. Triethylsilyl resveratrol treatment of HuH7 cells led to a prominent increase in expression of Atg-5, LC3B-II and Beclin proteins. In triethylsilyl resveratrol treated HuH7 cells expression of activated PI3K and Akt proteins showed a prominent decrease compared to the control cells. Moreover, p-mTOR protein expression was also suppressed in HuH7 cells on treatment with 2 µM triethylsilyl resveratrol. In triethylsilyl resveratrol treated cells a marked increase in ERK1/2 phosphorylation was observed compared to the control cells. Treatment with 2 µM triethylsilyl resveratrol for 72 h led to a significant (p < 0.05) increase in GFP-LC3B labelling in HuH7 cells compared to the control cells. Thus, triethylsilyl resveratrol reduced liver cancer cell viability through increase expression of proteins associated with autophagy. Moreover, it increased p-ERK1/2 expression and targeted activation of PI3K/Akt protein in HuH7 cells. Therefore, triethylsilyl resveratrol may be studied further as a promising therapeutic agent for treatment of liver cancer.

Coumarins and Gastrointestinal Cancer: A New Therapeutic Option?

Cancers of the gastrointestinal (GI) tract are often life-threatening malignancies, which can be a severe burden to the health care system. Globally, the mortality rate from gastrointestinal tumors has been increasing due to the lack of adequate diagnostic, prognostic, and therapeutic measures to combat these tumors. Coumarin is a natural product with remarkable antitumor activity, and it is widely found in various natural plant sources. Researchers have explored coumarin and its related derivatives to investigate their antitumor activity, and the potential molecular mechanisms involved. These mechanisms include hormone antagonists, alkylating agents, inhibitors of angiogenesis, inhibitors of topoisomerase, inducers of apoptosis, agents with antimitotic activity, telomerase inhibitors, inhibitors of human carbonic anhydrase, as well as other potential mechanisms. Consequently, drug design and discovery scientists and medicinal chemists have collaborated to identify new coumarin-related agents in order to produce more effective antitumor drugs against GI cancers. Herein, we summarize the therapeutic effects of coumarin and its derivatives against GI cancer.

The clinical, prognostic and therapeutic significance of liver cancer stem cells and their markers

Hepatocellular carcinoma (HCC) is the fourth most common cause of death among cancers. The poor prognosis of HCC might be caused by a population of cancer stem cells (CSC). CSC have similar characteristics to normal stem cells and are responsible for cancer recurrence, chemoresistance, radioresistance and metastasis. Liver cancer stem cells (LCSC) are identified via specific surface markers, such as CD44, CD90, CD133, and EpCAM (CD326). Recent studies suggested a complex interaction between mentioned LCSC markers and clinical features of HCC. A high expression of CSC is correlated with a negative prognostic factor after surgical resection of HCC and is connected with more aggressive tumor behavior. Moreover, LCSC might be responsible for increasing resistance to sorafenib, a kinase inhibitor drug. A reduction in the LCSC population may be crucial to successful advanced HCC therapy.

Ring1 promotes the transformation of hepatic progenitor cells into cancer stem cells through the Wnt/β-catenin signaling pathway

The proliferation of hepatic progenitor cells (HPCs) is observed in reactive conditions of the liver and primary liver cancers. Ring1 as a member of polycomb-group proteins which play vital roles in carcinogenesis and stem cell self-renewal was increased in HCC patients and promoted proliferation and survival of cancer cell by degrading p53. However, the mechanisms of Ring1 driving the progression of hepatocarcinogenesis have not been elucidated. In this study, forced expression Ring1 and Ring1 siRNA lentiviral vectors were utilized to stably overexpression and silence Ring1 in HPC cell line (WB-F344), respectively. Our finding indicated that overexpression of Ring1 in HPCs promoted colony formation, cell multiplication, and invasion in vitro, conversely depletion of Ring1 repressed the biological functions of HPCs relative to controls. The expression of β-catenin was upregulated in the HPCs with overexpression of Ring1, and the correlation analysis also showed that β-catenin and Ring1 had a significant correlation in the liver cancer tissues and adjacent tissues. The activation of the Wnt/β-catenin signaling pathway significantly increased the expression of liver cancer stem cells related (LCSCs)-related molecular markers CD90 and EpCAM, which led to the transformation of HPCs into LCSCs. Most importantly, the injection of HPCs with overexpressed Ring1 into the subcutaneous of nude mice leads to the formation of poorly differentiated HCC neoplasm. Our findings elucidate that overexpression of Ring1 the activated Wnt/β-catenin signaling pathway and drove the transformation of HPCs into cancer stem cell-like cells, suggesting Ring1 has extraordinary potential in early diagnosis of HCC.

Hydroxypyridinone-Coumarin Inhibits the Proliferation of MHCC97 and HepG2 Human Hepatocellular Carcinoma Cells and Down-Regulates the Phosphoinositide-3 Kinase Pathway

Background

Worldwide, hepatocellular carcinoma (HCC) is one of the most commonly diagnosed malignant diseases and is the third leading cause of cancer-related death. This study aimed to investigate the effect of hydroxypyridinone-coumarin (HPC) on MHCC97 and HepG2 human HCC cells and the mechanisms involved.

Material/Methods

MHCC97 and HepG2 human HCC cells were cultured in vitro. An MTT cytotoxicity assay was used to assess cell viability and proliferation, with and without treatment with HPC. Cell autophagosomes were labeled with GFP-LC3 using confocal fluorescence microscopy. Western blot was used to measure protein expression.

Results

HPC significantly reduced the cell proliferation rate in a concentration-dependent manner, with 2 μM of HPC resulting in a reduced proliferation rate of MHCC97 cells (by 36%) and HepG2 cells (by 29%) (P<0.02). HPC significantly reduced autophagy in MHCC97 and HepG2 cells. Western blot showed that treatment with HPC significant upregulated Atg5, beclin-1, LC3-phosphatidylethanolamine conjugate (LC3-II), and Atg-3, reduced p62 and Akt protein expression, and induced phosphorylation of ERK1/2. GFP-LC3B labeling in MHCC97 and HepG2 cells was increased following HPC treatment.

Conclusions

HPC induced autophagy and inhibited the proliferation of MHCC97 and HepG2 HCC cells in vitro and involved activation of ERK1/2 and down-regulation of the Akt pathway.

A Signaling Crosstalk between BMP9 and HGF/c-Met Regulates Mouse Adult Liver Progenitor Cell Survival

During chronic liver disease, hepatic progenitor cells (HPC, oval cells in rodents) become activated, proliferate, and differentiate into cholangiocytes and/or hepatocytes contributing to the final outcome of the regenerative process in a context-dependent fashion. Here, we analyze the crosstalk between the hepatocyte growth factor (HGF)/c-Met signaling axis, key for liver regeneration, and bone morphogenetic protein (BMP)9, a BMP family ligand that has emerged as a critical regulator of liver pathology. Our results show that HGF/c-Met signaling blocks BMP9-mediated apoptotic cell death, while it potentiates small mothers against decapentaplegic (SMAD)1 signaling triggered by BMP9 in oval cells. Interestingly, HGF-induced overactivation of SMAD1, -5, -8 requires the upregulation of TGF-β type receptor activin receptor-like kinase (ALK)1, and both ALK1 and SMAD1 are required for the counteracting effect of HGF on BMP9 apoptotic activity. On the other hand, we also prove that BMP9 triggers the activation of p38MAPK in oval cells, which drives BMP9-apoptotic cell death. Therefore, our data support a model in which BMP9 and HGF/c-Met signaling axes establish a signaling crosstalk via ALK1 that modulates the balance between the two pathways with opposing activities, SMAD1 (pro-survival) and p38 mitogen-activated protein kinases (p38MAPK; pro-apoptotic), which determines oval cell fate. These data help delineate the complex signaling network established during chronic liver injury and its impact on the oval cell regenerative response.

Effect of gastric cancer stem cell on gastric cancer invasion, migration and angiogenesis

Purpose: Using the gastric cancer cell line SGC7901 and gastric cancer stem cell (CSC-G), we conducted this study to investigate the role of cancer stem cells in invasion, metastasis and tumor angiogenesis. Methods: Stem cell markers (OCT4, SOX2, C-Myc and Klf4) expression was detected by RT-PCR and Western blotting. The proliferation, migration, invasion abilities, L-OHP and 5-FU resistance, angiogenesis were assessed using in vitro spherical clone formation assays, plate cloning experiments, transwell migration, transwell invasion, drug resistance, scratch-wound migration, ring formation assay, and their tumorigenic and ability were assessed using a tumor formation experiment in mice. Results: Compared with the SGC7901, the expression of Oct4, Sox2, Klf4 and CD44 mRNA was significantly higher in CSC-G, the mRNA relative expression of E-cadherin in CSC-G was lower than SGC7901, while the expression of c-Myc did not significantly change. The proliferation, drug resistance, migration, and invasion abilities were significantly higher in CSC-G, and the tumorigenic ability in mice was also significantly higher. Conclusion: The proliferation, drug resistance, migration, invasion, and tumorigenic abilities of CSC-G significantly were higher than SGC7901. CSC-G plays important roles in proliferation, migration, invasion, and tumorigenicity.

Higher expression of SATB2 in hepatocellular carcinoma of African Americans determines more aggressive phenotypes than those of Caucasian Americans

In the United States, Hepatocellular Carcinoma (HCC) incidence has tripled over the past two decades. The disease has disproportionately affected minority and disadvantaged populations. The purpose of this study was to examine the expression of SATB2 gene in HCC cells derived from African Americans (AA) and Caucasian Americans (CA) and assess its oncogenic potential by measuring cell viability, spheroid formation, epithelial‐mesenchymal transition (EMT), stem cell markers and pluripotency maintaining factors in cancer stem cells (CSCs). We compared the expression of SATB2 in human primary hepatocytes, HCC cells derived from AA and CA, and HCC CSCs. Hepatocellular carcinoma cells derived from AA expressed the higher level of SATB2 than those from CA. By comparison, normal human hepatocytes did not express SATB2. Higher expression of SATB2 in HCC cells from AA was associated with greater growth rate, cell viability, colony formation and EMT characteristics than those from CA. Knockout of SATB2 in CSCs by Crispr/Cas9 technique significantly inhibited the expression of SATB2 gene, stem cell markers (CD24, CD44 and CD133), pluripotency maintaining factors (c‐Myc, KLF4, SOX2 and OCT4), and EMT compared with non‐targeting control group. The expression of SATB2 was negatively correlated with miR34a. SATB2 rescued the miR‐34a‐mediated inhibition of CSC's viability. These data suggest that SATB2 is an oncogenic factor, and its higher expression may explain the disparity in HCC outcomes among AA.

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.

Cancer stem cells in hepatocellular carcinoma: an overview and promising therapeutic strategies

The poor clinical outcome of hepatocellular carcinoma (HCC) patients is ascribed to the resistance of HCC cells to traditional treatments and tumor recurrence after curative therapies. Cancer stem cells (CSCs) have been identified as a small subset of cancer cells which have high capacity for self-renewal, differentiation and tumorigenesis. Recent advances in the field of liver CSCs (LCSCs) have enabled the identification of CSC surface markers and the isolation of CSC subpopulations from HCC cells. Given their central role in cancer initiation, metastasis, recurrence and therapeutic resistance, LCSCs constitute a therapeutic opportunity to achieve cure and prevent relapse of HCC. Thus, it is necessary to develop therapeutic strategies to selectively and efficiently target LCSCs. Small molecular inhibitors targeting the core stemness signaling pathways have been actively pursued and evaluated in preclinical and clinical studies. Other alternative therapeutic strategies include targeting LCSC surface markers, interrupting the CSC microenvironment, and altering the epigenetic state. In this review, we summarize the properties of CSCs in HCC and discuss novel therapeutic strategies that can be used to target LCSCs.

Reactive Ductules Are Associated With Angiogenesis and Tumor Cell Proliferation in Pediatric Liver Cancer

While reactive ductules (RDs) have been observed in viral hepatitis, biliary atresia, nonalcoholic fatty liver disease, and adult hepatocellular carcinoma (HCC), RDs in pediatric liver cancer remain uncharacterized. This study investigated the relationship of RDs with angiogenic paracrine factors, the extent of angiogenesis, and tumor cell proliferation in pediatric hepatoblastoma (HBL)/HCC livers. We quantified the extent of RDs and their expression of paracrine factors that include vascular endothelial growth factor (VEGF), vascular endothelial growth factor D (VEGFD), platelet‐derived growth factor C, and angiopoietin 1 (ANGPT1). In addition, we performed immunohistochemical detection of the endothelial marker clusters of differentiation (CD)34 and the proliferation marker Ki67 followed by correlation analyses. In HBL, we found the percentage of RDs with Ki67 expression (% Ki67+ RDs) significantly correlated with intratumoral Ki67+ areas (r = 0.5138, P = 0.0349) and % ANGPT1+ RDs positively correlated with % Ki67+ RDs (r = 0.5851, P = 0.0136). In HCC, the high ANGPT1+ RDs group (i.e., cases with % ANGPT1+ RDs ≥50) exhibited high intratumoral Ki67+ areas compared to the low ANGPT1+ RDs group. In the combined HBL and HCC liver tumor group, there was a positive association between % platelet‐derived growth factor C+ RDs and intratumoral Ki67+ areas (r = 0.4712, P = 0.0099) and the high VEGFD+ RDs group (≥50%) exhibited a high number of peritumoral CD34+ vessels compared to the low VEGFD+ RDs group. Conclusion: Paracrine factor‐expressing RDs are associated with angiogenesis and proliferation of pediatric liver tumors.

The osteopontin-CD44 axis in hepatic cancer stem cells regulates IFN signaling and HCV replication

Osteopontin (OPN) is involved in cell proliferation, migration, inflammation, and tumor progression in various tissues. OPN induces stemness by interacting with CD44, but the functional relevance of OPN-mediated interferon (IFN) signaling and hepatitis C virus (HCV) replication in stem cell populations remains unclear. In this study, we investigated the effect of OPN on HCV replication and IFN signaling in cancer stem cells (CSCs) positive for epithelial cell adhesion molecule (EpCAM) and CD44. We show that the EpCAM⁺/CD44⁺ CSCs show marked HCV replication when compared to EpCAM⁻/CD44⁻ cells. In addition, OPN significantly enhances this HCV replication in EpCAM⁺/CD44⁺ CSCs and markedly suppresses IFN-stimulated gene expression. The GSK-3β inhibitor BIO increases the EpCAM⁺/CD44⁺ CSC population and OPN expression and impairs IFN signaling via STAT1 degradation. Taken together, our data suggest that OPN enhances HCV replication in the EpCAM⁺/CD44⁺ CSCs, while it also negatively regulates the IFN signaling pathway via inhibition of STAT1 phosphorylation and degradation. Therefore, OPN may represent a novel therapeutic target for treating HCV-related hepatocellular carcinoma.

Synthesis and Characterization of Novel BMI1 Inhibitors Targeting Cellular Self-Renewal in Hepatocellular Carcinoma

BACKGROUND

Hepatocellular carcinoma (HCC) represents one of the most lethal cancers worldwide due to therapy resistance and disease recurrence. Tumor relapse following treatment could be driven by the persistence of liver cancer stem-like cells (CSCs). The protein BMI1 is a member of the polycomb epigenetic factors governing cellular self-renewal, proliferation, and stemness maintenance. BMI1 expression also correlates with poor patient survival in various cancer types.

OBJECTIVE

We aimed to elucidate the extent to which BMI1 can be used as a potential therapeutic target for CSC eradication in HCC.

METHODS

We have recently participated in characterizing the first known pharmacological small molecule inhibitor of BMI1. Here, we synthesized a panel of novel BMI1 inhibitors and examined their ability to alter cellular growth and eliminate cancer progenitor/stem-like cells in HCC with different p53 backgrounds.

RESULTS

Among various molecules examined, RU-A1 particularly downregulated BMI1 expression, impaired cell viability, reduced cell migration, and sensitized HCC cells to 5-fluorouracil (5-FU) in vitro. Notably, long-term analysis of HCC survival showed that, unlike chemotherapy, RU-A1 effectively reduced CSC content, even as monotherapy. BMI1 inhibition with RU-A1 diminished the number of stem-like cells in vitro more efficiently than the model compound C-209, as demonstrated by clonogenic assays and impairment of CSC marker expression. Furthermore, xenograft assays in zebrafish showed that RU-A1 abrogated tumor growth in vivo.

CONCLUSIONS

This study demonstrates the ability to identify agents with the propensity for targeting CSCs in HCC that could be explored as novel treatments in the clinical setting.

Cancer stem cells of hepatocellular carcinoma

Hepatocellular carcinoma is a malignant tumor arising from hepatocytes. The hepatocellular carcinoma is dictated by a subset of cells with stem cell-like features. These cells are apoptosis-resistant and have particular biomarkers, which serve as seeds in different stages of tumorigenesis including initiation, progression, metastasis, and relapse of hepatocellular carcinoma. Signaling pathways of cancer stem cells are novel targets for the radical intervention of hepatocellular carcinoma.

Mefloquine targets β-catenin pathway and thus can play a role in the treatment of liver cancer

The current study was designed and performed to investigate the effect of mefloquine on the proliferation and tumor formation potential of liver cancer stem cells. CD133 + HepG2 cells were identified using MACS and showed markedly higher tumor formation potential compared to the parental cells. The secondary tumors formed by CD133 + cells were markedly large in size and more in number compared to the parental cells. Mefloquine treatment of CD133 + HepG2 cells inhibited the proliferation selectively in concentration based manner. The rate of proliferation was inhibited to 82 and 12% in parental and CD133 + sphere forming cells, respectively on treatment with 10 μM concentration of mefloquine. The number of secondary tumors formed by primary tumors was decreased significantly on treatment with 10 μM mefloquine concentration. Treatment of the liver cancer stem cells with mefloquine markedly decreased the potential to undergo self-renewal at 10 μM concentration after 48 h. The results from western blot analysis showed significantly higher expression of cancer stem cell molecules β-catenin and cyclin D1 in LCSCs. Treatment of the LCSCs with various concentrations of mefloquine reduced the expression levels of β-catenin and cyclin D1. Administration of the CD133 + cell tumor xenografts in the mice led to the formation of large sized tumors in the control group. However, the tumor growth was inhibited significantly in the mice on treatment with 10 mg/kg doses of mefloquine after day 21. The tumor weight was significantly lower in the animals of mefloquine treatment group compared to the control group. Thus, mefloquine treatment inhibits self-renewal and proliferation potential of cells through targeting β-catenin pathway.

Triptolide inhibits viability and induces apoptosis in liver cancer cells through activation of the tumor suppressor gene p53

The present study investigated the effect of triptolide on viability and apoptosis along with underlying mechanism in liver cancer cells. CCK-8 assay showed that triptolide treatment for 48 h significantly reduced the viability of HepG2 and QSG7701 cells at 50 µM concentration. Annexin V-FITC and propidium iodide staining showed that triptolide treatment of HepG2 cells at 50 µM concentrations induced apoptosis in 56.45% cells compared to only 2.36% cells in the control cultures. Western blot assay showed that treatment of HepG2 cells with 50 µM concentration of triptolide significantly induced phosphorylation of p53 in a 2 h-treatment. Phosphorylation of histone H2A.X indicator of DNA damage was induced by triptolide treatment after 12 h in HepG2 cells. The level of nuclear p53 in a 6 h-treatment with 0, 10, 20, 30, 40 and 50 µM concentration of triptolide was found to be 15.3, 19.6, 28.5, 43.7, 63.8 and 91.5%, respectively. Treatment of HepG2 cells with triptolide at 50 µM concentration caused a significant increase in the binding potential of p53 to DNA. Triptolide treatment of HepG2 cells caused a significant increase in the expression of p21, Bax and DR5 genes in HepG2 cells. It also increased the expression of miR-34b and miR-34c in HepG2 cells markedly. Treatment of HepG2 cells with p53 inhibitor, pifithrin-α prior to incubation with triptolide significantly prevented induction of cell apoptosis. Suppression of p53 expression by siRNA inhibited the expression of p53 as well as its target genes along with the prevention of apoptosis induction. In conclusion, triptolide inhibits viability and induces apoptosis in liver cancer cells through activation of the tumor suppressor gene p53. Thus, triptolide can be used for the treatment of liver cancer.

Brown seaweeds protect against azoxymethane-induced hepatic repercussions through up-regulation of peroxisome proliferator-activated receptor gamma and attenuation of oxidative stress

CONTEXT

Seaweeds of the genera Turbinaria and Padina have long been used as food and in traditional medicine for treating several diseases.

OBJECTIVE

The current study determines the protective efficacy of the brown seaweeds Turbinaria ornata (Turner) J. Agardh (Sargassaceae) and Padina pavonia (Linnaeus) J.V. Lamouroux (Dictyotaceae) against liver injury induced by azoxymethane (AOM).

MATERIALS AND METHODS

Male Swiss mice received 10 mg/kg AOM once a week for two consecutive weeks and then 100 mg/kg daily dose of either T. ornata or P. pavonia ethanolic extract. Thirteen weeks after the first AOM administration and 24 h after the last treatment, overnight fasted mice were sacrificed and samples collected.

RESULTS

Compared with the AOM group, both T. ornata and P. pavonia significantly decreased the activity of aminotransferases and the concentration of bilirubin while increased albumin levels in the serum. The antioxidative effect of both extracts was observed from the increased activity of superoxide dismutase and glutathione peroxidase activities in the liver, both of which were decreased by AOM. Moreover, the levels of malondialdehyde and nitric oxide were reduced, and histological findings also confirmed the antihepatotoxic activity. In addition, treatment with T. ornata and P. pavonia significantly increased PPARγ and decreased NF-κB expression in the liver of AOM-administered mice.

DISCUSSION AND CONCLUSION

Our findings indicate that the protective function of T. ornata and P. pavonia on AOM-induced liver injury may be possibly exerted by multiple pathways including abolishment of inflammation and oxidative damage, and activation of PPARγ.

Hepatocellular Carcinoma-propagating Cells are Detectable by Side Population Analysis and Possess an Expression Profile Reflective of a Primitive Origin

The recent identification of “Side Population” (SP) cells in a number of unrelated human cancers has renewed interests in the hypothesis of cancer stem cells. Here we isolated SP cells from HepG2 cells and 18 of the 21 fresh hepatocellular carcinoma (HCC) tissue samples. These SP cells have higher abilities of forming spheroids, invasion and migration. Tumors could generate only from SP, not non-SP (NSP), cells in a low dose of subcutaneous injection to the NOD/SCID mice (5 × 10² cells/mouse). The mRNA microarray analysis of the SP vs. NSP cells isolated from HepG2 cells revealed that the SP cells express higher levels of pluripotency- and stem cell-associated transcription factors including Klf4, NF-Ya, SALL4 and HMGA2. Some of the known hepatobiliary progenitor/stem cell markers, such as Sox9 was also up-regulated. RT-qPCR analysis of the gene expression between SP cells and NSP cells isolated from both HepG2 cells and HCC tissue samples showed that most of the tested mRNAs’ changes were in consistent with the microarray data, including the general progenitor/stem cells markers such as Klf4, NF-Ya, SALL4 and HMGA2, which were up-regulated in SP cells. Our data indicates that HCC cancer stem cells exist in HepG2 and HCC fresh tissue samples and can be isolated by SP assay.

Musashi 2 contributes to the stemness and chemoresistance of liver cancer stem cells via LIN28A activation

Accumulating evidence suggests that cancer stem cells (CSCs), a small subset of cancer cells, are responsible for tumor initiation, progression, relapse and metastasis. Musashi 2 (MSI2), a RNA-binding protein, was proposed to be a potent oncogene playing key roles in myeloid leukemia and gastrointestinal malignancies. However, it remains elusive how MSI2 regulates stem cell features in HCC. Herein, we demonstrated that MSI2 was highly expressed in liver CSCs. Overexpression or knockdown of MSI2 altered CSC-related gene expression, self-renewal as well as resistance to chemotherapy in HCC cell lines. In mouse xenograft models, MSI2 could markedly enhance tumorigenicity. Mechanistically, overexpression of MSI2 resulted in the upregulation of Lin28A. Stemness and chemotherapeutic drug resistance induced by MSI2 overexpression were dramatically reduced by Lin28A knockdown. Moreover, MSI2 and LIN28A levels positively correlated with the clinical severity and prognosis in HCC patients. In conclusion, MSI2 might play a crucial role in sustaining stemness and chemoresistance of liver CSCs via LIN28A-dependent manner in HCC. Our findings revealed that MSI2 and Lin28A might be used as potential therapeutic targets for eradicating liver CSCs.

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

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

CONCLUSION

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

The potential role of liver stem cells in initiation of primary liver cancer

Identification of the cellular origin of primary liver cancer remains challenging. Some data point toward liver stem cells (LSCs) or liver progenitor cells (LPCs) not only as propagators of liver regeneration, but also as initiators of liver cancer. LSCs exhibit a long lifespan and strong duplicative potential upon activation and are inclined to accumulate more mutations that can be passed down to the next generations. Recent evidence shows that dysregulation of signaling pathways associated with self-renewal of LSCs can drive their aberrant proliferation and even malignant transformation. If LSCs could be proved to be an initiator of liver carcinogenesis, they would be promising for ultra-early diagnosis and targeting therapy of liver cancer. This review mainly summarizes the potential role of LSCs in the carcinogenesis of primary liver cancer.

Positive feedback loop between cancer stem cells and angiogenesis in hepatocellular carcinoma

Anti-angiogenesis-related therapies have become the standard care for patients with advanced hepatocellular carcinoma (HCC), as HCC is a highly vascularized solid tumor. Unfortunately, only modest and limited efficacies are observed. Emerging evidence have attributed to the limited efficacy to the presence of cancer stem cells (CSCs) in the tumor. CSCs predominantly drives angiogenesis via releasing proangiogenic factors and exosomes. They have the ability to resistant intratumoral hypoxia via autophagy or by directly forming the tubular structure to obtain blood. On the other hand, the vascular niche in tumor microenvironment also releases growth factors via juxtacrine and paracrine mechanisms to support the growth of CSCs and maintain its stemness features. This positive feedback loop between angiogenesis and CSCs exists in liver tumor microenvironment that is responsible for the development and poor prognosis of HCC. In this review, we summarize recent advances in our understanding of the crosstalks between angiogenesis and CSCs, and their interactions in liver tumor microenvironment and their purpose that an effective anti-angiogenic therapy should also target CSCs for HCC treatment.

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.

Cantharidin inhibits cell proliferation and induces apoptosis through G2/M phase cell cycle arrest in hepatocellular carcinoma stem cells

The present study was designed to investigate the effect of cantharidin on cell proliferation, ability of selfrenewal, cell cycle arrest and induction of apoptosis in HepG2 hepatocellular carcinoma stem cells (HCSCs). It was observed that cantharidin treatment exhibited dose- and time-dependent inhibitory effect on the viability of HCSCs. The inhibition of cell viability by cantharidin in HepG2 CD133+ and parental cells was significant at the concentration 5 and 15 µM, respectively after 48 h. Cantharidin treatment inhibited the self-renewal ability of the HCSCs and the expression of β-catenin and cyclin D1. Flow cytometry revealed that cantharidin treatment at 5 µM concentration significantly increased the cell population in G2/M phase and decreased the population in the G1 phase. Cantharidin treatment in the HCSCs for 48 h increased expression of histone H2AX, Myt1, cyclin A2, cyclin B1, p53 and cdc2 (Tyr15) phosphorylation significantly compared to the parental cells. Exposure of the HCSCs to cantharidin for 48 h at a concentration of 5 µM caused a significant increase in the proportion of apoptotic cells. Therefore, cantharidin is a promising agent for the hepatocellular carcinoma treatment.

Constitutive expression of Wnt/β‑catenin target genes promotes proliferation and invasion of liver cancer stem cells

Wnt/β-catenin is an important signaling pathways involved in the tumorgenesis, progression and maintenance of cancer stem cells (CSCs). In the present study, the role of Wnt/β-catenin signaling in CSC-mediated tumorigenesis and invasion in liver CSCs was investigated. A small population of cancer stem-like side population (SP) cells (3.6%) from liver cancer samples were identified. The cells were highly resistant to drug treatment due to the enhanced expression of drug efflux pumps, such as ABC subfamily G member 2, multidrug resistance protein 1 and ATP-binding cassette subfamily B member 5. Furthermore, using TOPflash and reverse transcription-quantitative polymerase chain reaction analysis, Wnt/β-catenin signaling and the transcriptional regulation of Wnt/β-catenin target genes including dickkopf Wnt signaling pathway inhibitor 1, axis inhibition protein 2 and cyclin D1 were observed to be markedly upregulated in liver cancer SP cells. As a consequence, SP cells possessed infinite cell proliferation potential and the ability to generating tumor spheres. In addition, upon reducing Wnt/β-catenin signaling, the rates of proliferation, tumor sphere formation and tumor invasion of SP cells were markedly reduced. Therefore, these data suggest that Wnt/β-catenin signaling is a potential therapeutic target to reduce CSC-mediated tumorigenicity and invasion in liver cancer.

Plasma DCLK1 is a marker of hepatocellular carcinoma (HCC): Targeting DCLK1 prevents HCC tumor xenograft growth via a microRNA-dependent mechanism

Tumor stem cell marker Doublecortin-like kinase1 (DCLK1) is upregulated in several solid tumors. The role of DCLK1 in hepatocellular carcinoma (HCC) is unclear. We immunostained tissues from human livers with HCC, cirrhosis controls (CC), and non-cirrhosis controls (NCC) for DCLK1. Western blot and ELISA analyses for DCLK1 were performed with stored plasma samples. We observed increased immunoreactive DCLK1 in epithelia and stroma in HCC and CCs compared with NCCs, and observed a marked increase in plasma DCLK1 from patients with HCC compared with CC and NCC. Analysis of the Cancer Genome Atlas' HCC dataset revealed that DCLK1 is overexpressed in HCC tumors relative to adjacent normal tissues. High DCLK1-expressing cells had more epithelial-mesenchymal transition (EMT). Various tumor suppressor miRNAs were also downregulated in HCC tumors. We evaluated the effects of DCLK1 knockdown on Huh7.5-derived tumor xenograft growth. This was associated with growth arrest and a marked downregulation of cMYC, and EMT transcription factors ZEB1, ZEB2, SNAIL, and SLUG via let-7a and miR-200 miRNA-dependent mechanisms. Furthermore, upregulation of miR-143/145, a corresponding decrease in pluripotency factors OCT4, NANOG, KLF4, and LIN28, and a reduction of let-7a, miR-143/145, and miR-200-specific luciferase activity was observed. These findings suggest that the detection of elevated plasma DCLK1 may provide a cost-effective, less invasive tool for confirmation of clinical signs of cirrhosis, and a potential companion diagnostic marker for patients with cirrhosis and HCC. Our results support evaluating DCLK1 as a biomarker for detection and as a therapeutic target for eradicating HCC.

Aberrantly regulated dysadherin and B-cell lymphoma 2/B-cell lymphoma 2-associated X enhances tumorigenesis and DNA targeting drug resistance of liver cancer stem cells

Cancer stem cells (CSCs) in hepatocellular carcinoma (HCC) are frequently resistant to current therapeutic regimens and therefore responsible for tumor recurrence. Previous studies have reported that expression levels of dysadherin in CSCs may be used as a prognostic indicator, which is also responsible for treatment failure and poor survival rates. The present study analyzed the association of enhanced dysadherin levels with drug resistance and evasion of apoptosis in human HCC SP cells. An SP of 3.7% was isolated from human HCC cells using fluorescence-activated cell sorting. These SP cells displayed elevated levels of dysadherin and stemness proteins as well as high resistance to chemotherapeutic drugs and apoptosis. In order to reveal the possible link between dysadherin levels and tumorigenesis of SP cells, small interfering RNA technology was used to knockdown the expression of dysadherin in SP cells. Of note, the siRNA-transfected SP cells showed significantly reduced levels of stemness proteins, and were more sensitive to DNA-targeting drugs and apoptotic cell death as compared to non-transfected cells. Furthermore, in vivo experiments in NON/SCID mice indicated that dysadherin-expressing SP cells were highly tumorigenic, as they were able to induce tumor growth. The SP cell-derived tumor tissues in turn showed elevated dysadherin levels. The results of the present study therefore suggested that knockdown of dysadherin suppressed the tumorigenic properties of cancer stem-like SP cells. Hence, dysadherin is a valuable potential target for the development of novel anti-cancer drugs.

HGF/c-Met signaling promotes liver progenitor cell migration and invasion by an epithelial-mesenchymal transition-independent, phosphatidyl inositol-3 kinase-dependent pathway in an in vitro model

Oval cells constitute an interesting hepatic cell population. They contribute to sustain liver regeneration during chronic liver damage, but in doing this they can be target of malignant conversion and become tumor-initiating cells and drive hepatocarcinogenesis. The molecular mechanisms beneath either their pro-regenerative or pro-tumorigenic potential are still poorly understood. In this study, we have investigated the role of the HGF/c-Met pathway in regulation of oval cell migratory and invasive properties. Our results show that HGF induces c-Met-dependent oval cell migration both in normal culture conditions and after in vitro wounding. HGF-triggered migration involves F-actin cytoskeleton reorganization, which is also evidenced by activation of Rac1. Furthermore, HGF causes ZO-1 translocation from cell-cell contact sites to cytoplasm and its concomitant activation by phosphorylation. However, no loss of expression of cell-cell adhesion proteins, including E-cadherin, ZO-1 and Occludin-1, is observed. Additionally, migration does not lead to cell dispersal but to a characteristic organized pattern in rows, in turn associated with Golgi compaction, providing strong evidence of a morphogenic collective migration. Besides migration, HGF increases oval cell invasion through extracellular matrix, a process that requires PI3K activation and is at least partly mediated by expression and activation of metalloproteases. Altogether, our findings provide novel insights into the cellular and molecular mechanisms mediating the essential role of HGF/c-Met signaling during oval cell-mediated mouse liver regeneration.

Heterogeneity of hepatocellular carcinoma contributes to cancer progression

Hepatocellular carcinoma (HCC) is a highly heterogeneous disease displaying differences in angiogenesis, extracellular matrix proteins, the immune microenvironment and tumor cell populations. Additionally, genetic variations and epigenetic changes of HCC cells could lead to aberrant signaling pathways, induce cancer stem cells and enhance tumor progression. Thus, the heterogeneity in HCC contributes to disease progression and a better understanding of its heterogeneity will greatly aid in the development of strategies for the HCC treatment.

Tumor formation and drug resistance properties of human glioblastoma side population cells

Accumulating evidence has demonstrated that the presence of a subset of cells in several types of brain tumor, termed brain cancer stem cells, are responsible for tumor recurrence following chemotherapy or radiotherapy. The isolation and characterization of side population (SP) cells in several types of solid tumor using Hoechst dye has become a powerful technique for obtaining cancer stem cells (CSCs). In the present study, cancer stem‑like SP cells were isolated from the human glioblastoma cell line MG‑12 using the Hoechst 33342 dye exclusion technique. Flow cytometric analysis revealed that the cell line MG‑12 contained 3.2% SP cells, which was reduced to 0.5% in the presence of verapamil, an inhibitor of ATPase‑binding cassette (ABC) transporters. Reverse‑transcription quantitative polymerase chain reaction analysis revealed that the isolated SP cells exhibited increased expression of stem cell markers, including Nestin, Notch 1, octamer‑binding transcription factor 4 (Oct‑4), epithelial cell adhesion molecule (EpCAM) and also ABC transporter protein ABCG2. Additionally, using western blot analysis it was demonstrated that SP cells exhibit positivity and have a higher expression of CD133, CD44, EpCAM, Oct‑4 and B‑cell lymphoma 2. Furthermore, it was demonstrated that the isolated SP cells undergo rapid proliferation, have a high propensity to form tumor spheres and also have a high survival rate following treatment with 5‑fluorouracil. Therefore, the present findings suggest that SP cells of the glioblastoma MG‑12 cell line share characteristics of CSCs. Therefore, the increased expression of stem cell markers and ABCG2 protein may interact with each other and be responsible for drug and apoptotic resistance, tumor recurrence and invasion.

Role of circulating tumor cells and cancer stem cells in hepatocellular carcinoma

Circulating tumor cells (CTC) and cancer stem cells (CSC) have been proposed as tools for detection and characterization of disease and individualization of therapy in patients with many solid tumors. Several automated and semi-automated techniques for identification and isolation of these cells from blood have been proposed and reviewed mostly focusing on their feasibility. In this mini review we summarize the recent relevant literature on this topic and discuss the clinical usability of measuring CTC and CSC in peripheral blood in patients with hepatocellular carcinoma (HCC). Besides literature, the basis for this evaluation was the authors' experience with treating HCC and research experience on CSC and CTC. Few original reports and reviews have been published focusing on CTC and CSC in HCC. Though HCC is one of the five most common malignancies worldwide only recently these cells have come into focus for detection and characterization of this disease that is characterized by high plasticity and malignancy. A focused and prospective validation of the clinical usability of detecting these cells in HCC is still needed, but results seem promising that they may add great benefit for early detection and individualization of therapy.

Hepatocellular Carcinoma: Basic and Transitional Research

BACKGROUND

Hepatocellular carcinoma (HCC) is one of the leading causes of cancer-related deaths worldwide. The outcome of HCC therapy depends on the stage of HCC. Early-stage HCC patients can be cured with radical treatment approaches, whereas no standard treatment regimens can be recommended for patients with advanced disease.

SUMMARY

In-depth basic research into the molecular mechanisms of HCC has contributed to the development of novel therapeutic agents. This article reviews several key classes of novel therapeutic agents that are under development, including molecular-targeted therapies, cancer stem cell (CSC)-based therapy and differentiation therapy.

KEY MESSAGE

A greater understanding of the molecular pathogenesis of HCC has contributed to the development of novel therapeutic agents. This article reviews several key classes of novel therapeutic agents that are under development, including molecular-targeted therapies, CSC-based therapy and differentiation therapy.

PRACTICAL IMPLICATIONS

Molecular-targeted therapies based on signaling pathways involved in hepatocarcinogenesis and progression are being evaluated in several clinical trials. There are three main categories of targeted agents: tyrosine kinase inhibitors (TKIs), monoclonal antibodies and enzyme inhibitors. The best-established agent is sorafenib, a non-specific TKI that is accepted as first-line therapy for specific patients. Other similar agents under investigation include erlotinib, linifanib and brivanib. CSC-based therapies are still in the earlier stages of development and include a neutralizing anti-CD44 antibody, small interfering RNA to suppress epithelial cell adhesion molecular levels, a neutralizing anti-CD13 antibody and a CD13 inhibitor. An important point is that CSC-targeted therapy should be combined with conventional therapies to achieve complete tumor regression. Differentiation therapy is defined as a strategy that induces malignant reversion of tumor cells. Hepatocyte nuclear factor 4α or 1α, important transcriptional factors for hepatocyte differentiation and phenotype maintenance, have shown significant antitumor effects by inducing differentiation of both non-CSCs and CSCs in HCC towards a hepatocyte-like phenotype.

CellMinerHCC: a microarray-based expression database for hepatocellular carcinoma cell lines

BACKGROUND & AIMS

Therapeutic options for hepatocellular carcinoma (HCC) still remain limited. Development of gene targeted therapies is a promising option. A better understanding of the underlying molecular biology is gained in in vitro experiments. However, even with targeted manipulation of gene expression varying treatment responses were observed in diverse HCC cell lines. Therefore, information on gene expression profiles of various HCC cell lines may be crucial to experimental designs. To generate a publicly available database containing microarray expression profiles of diverse HCC cell lines.

METHODS

Microarray data were analyzed using an individually scripted R program package. Data were stored in a PostgreSQL database with a PHP written web interface. Evaluation and comparison of individual cell line expression profiles are supported via public web interface.

RESULTS

This database allows evaluation of gene expression profiles of 18 HCC cell lines and comparison of differential gene expression between multiple cell lines. Analysis of commonly regulated genes for signaling pathway enrichment and interactions demonstrates a liver tumor phenotype with enrichment of major cancer related KEGG signatures like 'cancer' and 'inflammatory response'. Further molecular associations of strong scientific interest, e.g. 'lipid metabolism', were also identified.

CONCLUSIONS

We have generated CellMinerHCC (http://www.medicalgenomics.org/cellminerhcc), a publicly available database containing gene expression data of 18 HCC cell lines. This database will aid in the design of in vitro experiments in HCC research, because the genetic specificities of various HCC cell lines will be considered.

Clinical significance of Ki-67 and p130 expression in liver needle biopsy from patients with hepatocellular carcinoma treated by transcatheter arterial chemoembolization

AIM: To investigate the clinical significance of Ki-67 and p130 expression in liver needle biopsy from patients with hepatocellular carcinoma (HCC) treated by transcatheter arterial chemoembolization (TACE).

METHODS: Medical records for 41 HCC patients treated by TACE between January 2005 and August 2010 were reviewed and the major clinical features, treatment modalities and outcomes were analyzed. The protein expression of Ki-67 and p130 was detected by S-P immunohistochemical method in 41 liver needle biopsies from patients with HCC.

RESULTS: The total positive rates of Ki-67 and p130 expression in HCC were 63.41% (26/41) and 51.52% (21/41), respectively. The expression of Ki-67 and p130 proteins was related to histological grade and prognosis (P < 0.05 for both), but not to sex, age, tumor size, TNM stage or serum level of AFP (P > 0.05 for all). There was a significant negative correlation between Ki-67 and p130 protein expression (r = -0.371, P < 0.05). The prognosis of the 41 patients with HCC treated by TACE was related to TNM stage and expression of Ki-67 and p130 (P < 0.05 for all), but not to sex, age, tumor size, histological grade or serum level of AFP (P > 0.05 for all).

CONCLUSION: Ki-67 and p130 play important roles in occurrence and development of HCC.Ki-67 and p130 can be used as predictive markers for HCC patients treated with TACE.

Casticin inhibits self-renewal of liver cancer stem cells from the MHCC97 cell line

Casticin exerts anticarcinogenic activity in several types of cancers, including human hepatocellular carcinoma (HCC). The aim of the present study was to investigate the effects of casticin, which is derived from Fructus Viticis Simplicifoliae, on the self-renewal capacity of liver cancer stem cells (LCSCs) derived from the HCC MHCC97 cell line. The present study demonstrated that casticin significantly inhibited the proliferation of LCSCs from the MHCC97 cell line in a dose-dependent manner (P<0.05), the half maximal inhibitory concentration of the parental cells and LCSCs was 17.9 and 0.5 μmol/l, respectively. Furthermore, casticin reduced the sphere-forming capacity of LCSCs and downregulated β-catenin protein expression in a concentration-dependent manner. Lithium chloride, an agonist known to activate the Wnt/β-catenin signaling pathway, attenuated the casticin-induced downregulation of β-catenin protein expression and inhibited the self-renewal capacity. To the best of our knowledge, the present study is the first to demonstrate that casticin effectively eradicates LCSCs and β-catenin was identified as the potential target. Thus, casticin may offer a novel therapeutic approach for the treatment of HCC.

Role for putative hepatocellular carcinoma stem cell subpopulations in biological response to incomplete thermal ablation: in vitro and in vivo pilot study

PURPOSE

To investigate the potential role for CD44(+) and CD90(+) hepatocellular carcinoma (HCC) cellular subpopulations in biological response to thermal ablation-induced heat stress.

METHODS

This study was approved by the institutional animal care committee. The N1S1 rat HCC cell line was subjected to sublethal heat stress (45 °C) or control (37 °C) for 10 min, costained with fluorescent-labeled antibodies against CD44, CD90, and 7-AAD after a 48-h recovery and analyzed by flow cytometry to assess the percentage of live CD44(+) and CD90(+) HCC cells (n = 4). Experiments were repeated with pretreatment of N1S1 cells with a dose titration of the dual PI3K-mTOR inhibitor BEZ235 or vehicle control (n = 3). Rats bearing orthotopic N1S1 tumors were subjected to ultrasound-guided partial laser ablation (n = 5) or sham ablation (n = 3), euthanized 24 h after ablation, and liver/tumor analyzed for immunohistochemical staining of CD44 and CD90. Differences between groups were compared with an unpaired t test.

RESULTS

Sublethal heat stress induced a significant increase in the relative proportion of live CD44(+) and CD90(+) HCC cells compared to the control group: CD44(+)CD90(-) (5.3-fold; p = 0.0001), CD44(-)CD90(+) (2.4-fold; p = 0.003), and CD44(+)CD90(+) (22.0-fold; p < 0.03). Inhibition of PI3K-mTOR prevented heat stress-induced enrichment of the population of live CD44(+) HCC cells (p < 0.01), but not CD90(+) cells (p > 0.10). Immunohistochemical analysis demonstrated preferential localization of clusters of CD44(+) cells at both the tumor margin and ablation margin.

CONCLUSION

These studies provide experimental evidence supporting a role for HCC cells expressing the putative stem cell marker CD44 in HCC response to heat stress.

Multiple interactive factors in hepatocarcinogenesis

Hepatocellular carcinoma (HCC) is the fifth most prevalent cancer and the third most frequent cause of cancer mortality globally. Each year there are approximately 630,000 new cases of HCC in the world and more than half of the new cases occur in China. Major risk factors of HCC include HBV or HCV infection, alcoholic liver disease, and nonalcoholic fatty liver disease. Most of these risk factors lead to chronic hepatitis and cirrhosis, which is present in 80-90% of HCC patients. Hepatocarcinogenesis has been regarded as a multi-stage process involving multiple genetic or environmental factors. Interaction and cross-regulation of distinct factors synergistically contributes to HCC occurrence. A comprehensive knowledge on the multiple factors and their interaction in hepatocarcinogenesis is necessary to improve the effectiveness of HCC intervention. In this review, we will focus on the recent progress made in understanding the mechanisms of hepatocarcinogenesis and discuss some potential issues or challenges in this area.

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.

Expression of OV-6 in primary colorectal cancer and rectal cancer with preoperative chemoradiotherapy: a clinicopathological study

AIMS

OV-6 is among the best available markers of liver stem cells. The aim of this study was to investigate OV-6 expression and its clinical implications in colorectal cancer.

METHODS AND RESULTS

Expression of OV-6 and its clinical implications were investigated in 94 patients with American Joint Committee on Cancer (AJCC) stage I-III primary colorectal cancer and in 37 rectal cancer patients who had received preoperative chemoradiotherapy. The two main expression patterns of OV-6 were cytoplasmic and membranous. Overexpression of OV-6, which was identified on the basis of overall staining intensity, was associated with perineural invasion, lymphovascular invasion, and early relapses. Membranous OV-6 overexpression was also significantly associated with depth of tumour invasion, AJCC stage, lymphovascular and perineural invasion, and postoperative early relapse. Disease-free survival and overall survival were significantly poorer in patients with high overall OV-6 expression than in those with low overall OV-6 expression (P = 0.015 and P = 0.029, respectively), and significantly poorer in patients with high membranous OV-6 expression than in those with low membranous OV-6 expression (P < 0.001 and P < 0.001, respectively). Membranous OV-6 expression was a more reliable prognostic marker than overall expression.

CONCLUSIONS

OV-6 is not unique to the hepatobiliary system, and may be a novel prognostic marker in colorectal cancer.

Up-regulation of thy-1 promotes invasion and metastasis of hepatocarcinomas

Increasing evidence has revealed that thy-1 was a potential stem cell marker of liver cancer, but no data have been shown on how thy-1 regulates the pathophysiology of liver cancer, such as proliferation, apoptosis, invasion and migration. We previously demonstrated that thy-1 was expressed in about 1% of hepg2 cells, thy-1+ hepg2 cells, but not thy-1-, demonstrating high tumorigenesis on inoculation 0.5x10⁵ cells per BACA/LA mouse after 2 months. In the present study, our results showed that higher expression of thy-1 occurs in 72% (36/50 cases) of neoplastic hepatic tissues as compared to 40% (20/50 cases) of control tissues, and the expression of thy-1 is higher in poorly differentiated liver tumors than in the well-differentiated ones. In addition, thy-1 expression was detected in 85% of blood samples from liver cancer patients, but none in normal subjects or patients with cirrhosis or hepatitis. There was a significant negative correlation between thy-1 expression and E-cadherin expression (a marker of invasion and migraton), but not between thy-1 expression and AFP expression in all the liver cancer and blood samples. We further investigated the relationship between thy-1 and E- cadherin in liver cancer hepg2 cell line which was transfected with pReceiver-M29/thy-1 eukaryotic expression vector followed by aspirin treatment. Lower expression of E- cadherin but higher expressions of thy-1 were detected in hepg2 cells transfected with pReceiver-M29/thy-1. Taken together, our study suggested that thy-1 probably regulates liver cancer invasion and migration.