Clinical significance of CD13 and epithelial mesenchymal transition (EMT) markers in hepatocellular carcinoma

Ascorbic acid predominantly kills cancer stem cell-like cells in the hepatocellular carcinoma cell line Li-7 and is more effective at low cell density and in small spheroids

The development of therapies that target cancer stem cells (CSCs) is an important challenge in cancer research. The antioxidant system is enhanced in CSCs, which may lead to resistance to existing therapies. Ascorbic acid (AA) has the potential to act as both an antioxidant and a pro-oxidant agent, but its effects on CSCs are a subject of current research. Here, we investigated the effect of AA focusing specifically on CSCs with the hepatocellular carcinoma cell line Li-7. The Li-7 cell line is heterogenous consisting of CD166- and CD166+ cells; CD166- cells include CSC-like cells (CD13+CD166- cells) and CD13-CD166- cells that can revert to CD13+CD166- cells. The addition of AA to the culture medium caused cell death in both cell populations in CD166- cells in a concentration dependent manner. In contrast, AA administration had a limited effect on CD166+ non-CSC cells. The level of reactive oxygen species after AA treatment was elevated only in CD166- cells. The effect of AA only occurred at low cell densities in 2D and 3D cultures. In a mouse tumor model injected with Li-7 cells, intraperitoneal administration of AA failed to prevent tumor formation but appeared to delay tumor growth. Our findings shed light on why AA administration has not become a mainstream treatment for cancer treatment; however, they also show the possibility that AA can be used in therapies to suppress CSCs.

Targeting signaling pathways in cancer stem cells: A potential approach for developing novel anti-cancer therapeutics

Cancer stem cells (CSCs) have emerged as prime players in the intricate landscape of cancer development, progression, and resistance to traditional treatments. These unique cellular subpopulations own the remarkable capability of self-renewal and differentiation, giving rise to the diverse cellular makeup of tumors and fostering their recurrence following conventional therapies. In the quest for developing more effective cancer therapeutics, the focus has now shifted toward targeting the signaling pathways that govern CSCs behavior. This chapter underscores the significance of these signaling pathways in CSC biology and their potential as pivotal targets for the development of novel chemotherapy approaches. We delve into several key signaling pathways essential for maintaining the defining characteristics of CSCs, including the Wnt, Hedgehog, Notch, JAK-STAT, NF-κB pathways, among others, shedding light on their potential crosstalk. Furthermore, we highlight the latest advancements in CSC-targeted therapies, spanning from promising preclinical models to ongoing clinical trials. A comprehensive understanding of the intricate molecular aspects of CSC signaling pathways and their manipulation holds the prospective to revolutionize cancer treatment paradigms. This, in turn, could lead to more efficacious and personalized therapies with the ultimate goal of eradicating CSCs and enhancing overall patient outcomes. The exploration of CSC signaling pathways represents a key step towards a brighter future in the battle against cancer.

Tazemetostat decreases β-catenin and CD13 protein expression in HEPG-2 and Hepatitis B virus-transfected HEPG-2 with decreased cell viability

Hepatocellular carcinoma (HCC) is one of the global health concerns. Hepatitis B virus (HBV) is one of the major causes of HCC. Poor clinical outcome of HCC patients is attributed to a small population of cancer cells known as cancer stem cells (CSCs). In this work, we studied the effect of inhibiting the enhancer of zeste homologue 2 (EZH2), a histone methyltransferase known to be overexpressed in CSCs, using tazemetostat (Taz). The effect of Taz was assessed in the HCC cell line (HEPG2) and Hepatitis B virus-transfected HEPG2 (HBV/HEPG2) cells. MTT assay showed a significant decrease in HEPG2 cells viability after 48 h treatment with either 0.5, 1, 4 or 6 μM Taz. HEPG2 and HBV/HEPG2 cells were incubated with either 0.5 or 1 μM Taz for 48 h, and then, the cells and supernatants were collected for protein expression analysis of EZH2, CD13, epithelial cell adhesion molecule (EpCAM) and β-catenin using enzyme-linked immunosorbent assay (ELISA). Taz showed a significant dose-dependent inhibition of EZH2, CD13 and β-catenin in HEPG2 and HBV/HEPG2 cells. Also, EpCAM protein levels were significantly decreased in HBV/HEPG2 but not in HEPG2 cell line alone. Our results indicate that Taz inhibition of EZH2 leads to downregulation of β-catenin signaling and eventually decreased expression of CD13 and EpCAM, which are characteristic for CSCs. The present study suggests that Taz could be a promising treatment for HCC including HBV-induced HCC that might be used in combination with radio/chemotherapy to target CSCs and prevent tumor relapse.

Identification of a gene set that maintains tumorigenicity of the hepatocellular carcinoma cell line Li-7

The identification and development of therapeutic targets in cancer stem cells that lead to tumor development, recurrence, metastasis, and drug resistance is an important goal in cancer research. The hepatocellular carcinoma cell line Li-7 contains functionally different types of cells. Cells with tumor-forming activity are enriched in cancer stem cell-like CD13+CD166- cells and this cell population gradually decreases during culture in conventional culture medium (RPMI1640 containing 10% fetal bovine serum). When Li-7 cells are cultured in mTeSR1, a medium developed for human pluripotent stem cells, CD13+CD166- cells, and their tumorigenicity is maintained. Here, we sought to identify the mechanisms of tumorigenicity in this sub-population. We compared gene expression profiles of CD13+CD166- cells with other cell sub-populations and identified nine overexpressed genes (ENPP2, SCGN, FGFR4, MCOLN3, KCNJ16, SMIM22, SMIM24, SERPINH1, and TMPRSS2) in CD13+CD166- cells. After transfer from mTeSR1 to RPMI1640 containing 10% fetal bovine serum, the expression of these nine genes decreased in Li-7 cells and they lost tumorigenicity. In contrast, when these genes of Li-7 cells were forcibly expressed in cultures using RPMI1640 containing 10% fetal bovine serum, Li-7 cells maintained tumorigenicity. A metabolome analysis using capillary electrophoresis-mass spectrometry showed that two metabolic pathways, "Alanine, aspartate and glutamate metabolism" and "Arginine biosynthesis" were activated in cancer stem-cell-like cells. Our analyses here showed potential therapeutic target genes and metabolites for treatment of cancer stem cells in hepatocellular carcinoma.

Evaluation and Application of Drug Resistance by Biomarkers in the Clinical Treatment of Liver Cancer

Liver cancer is one of the most lethal cancers in the world, mainly owing to the lack of effective means for early monitoring and treatment. Accordingly, there is considerable research interest in various clinically applicable methods for addressing these unmet needs. At present, the most commonly used biomarker for the early diagnosis of liver cancer is alpha-fetoprotein (AFP), but AFP is sensitive to interference from other factors and cannot really be used as the basis for determining liver cancer. Treatment options in addition to liver surgery (resection, transplantation) include radiation therapy, chemotherapy, and targeted therapy. However, even more expensive targeted drug therapies have a limited impact on the clinical outcome of liver cancer. One of the big reasons is the rapid emergence of drug resistance. Therefore, in addition to finding effective biomarkers for early diagnosis, an important focus of current discussions is on how to effectively adjust and select drug strategies and guidelines for the treatment of liver cancer patients. In this review, we bring this thought process to the drug resistance problem faced by different treatment strategies, approaching it from the perspective of gene expression and molecular biology and the possibility of finding effective solutions.

Long Non-Coding RNAs as Novel Targets for Phytochemicals to Cease Cancer Metastasis

Metastasis is a multi-step phenomenon during cancer development leading to the propagation of cancer cells to distant organ(s). According to estimations, metastasis results in over 90% of cancer-associated death around the globe. Long non-coding RNAs (LncRNAs) are a group of regulatory RNA molecules more than 200 base pairs in length. The main regulatory activity of these molecules is the modulation of gene expression. They have been reported to affect different stages of cancer development including proliferation, apoptosis, migration, invasion, and metastasis. An increasing number of medical data reports indicate the probable function of LncRNAs in the metastatic spread of different cancers. Phytochemical compounds, as the bioactive agents of plants, show several health benefits with a variety of biological activities. Several phytochemicals have been demonstrated to target LncRNAs to defeat cancer. This review article briefly describes the metastasis steps, summarizes data on some well-established LncRNAs with a role in metastasis, and identifies the phytochemicals with an ability to suppress cancer metastasis by targeting LncRNAs.

Role of microRNA-regulated cancer stem cells in recurrent hepatocellular carcinoma

Among the most common cancers, hepatocellular carcinoma (HCC) has a high rate of tumor recurrence, tumor dormancy, and drug resistance after initial successful chemotherapy or radiotherapy. A small subset of cancer cells, cancer stem cells (CSCs), exhibit stem cell characteristics and are present in various cancers, including HCC. The dysregulation of microRNAs (miRNAs) often accompanies the occurrence and development of HCC. miRNAs can influence tumorigenesis, progression, recurrence, and drug resistance by regulating CSCs properties, which supports their clinical utility in managing and treating HCC. This review summarizes the regulatory effects of miRNAs on CSCs in HCC with a special focus on their impact on HCC recurrence.

CD44v6+ Hepatocellular Carcinoma Cells Maintain Stemness Properties through Met/cJun/Nanog Signaling

Cancer stem cells (CSCs) are characterized by their self-renewal and differentiation abilities. CD44v6 is a novel CSC marker that can activate various signaling pathways. Here, we hypothesized that the HGF/Met signaling pathway promotes stemness properties in CD44v6+ hepatocellular carcinoma (HCC) cells via overexpression of the transcription factor, cJun, thus representing a valuable target for HCC therapy. Magnetic activated cell sorting was used to separate the CD44v6+ from CD44v6- cells, and Met levels were regulated using lentiviral particles and the selective Met inhibitor, PHA665752. An orthotopic liver xenograft tumor model was used to assess the self-renewal ability of CD44v6+ cells in immunodeficient NOD/SCID mice. Luciferase reporter and chromatin immunoprecipitation assays were also conducted using cJun-overexpressing 293 T cells to identify the exact binding site of cJun in the Nanog promoter. Our data demonstrate that CD44v6 is an ideal surface marker of liver CSCs. CD44v6+ HCC cells express higher levels of Met and possess self-renewal and tumor growth abilities. Xenograft liver tumors were smaller in nude mice injected with shMet HCC cells. Immunohistochemical analysis of liver tissue specimens revealed that high Met levels in HCC cells were associated with poor patient prognosis. Further, a cJun binding site was identified 1700 bp upstream of the Nanog transcription start site and mutation of the cJun binding site reduced Nanog expression. In conclusion, the HGF/Met signaling pathway is important for maintenance of stemness in CD44v6+ HCC cells by enhancing expression of cJun, which binds 1700 bp upstream of the Nanog transcription start site.

Cancer Stem Cells in Hepatocellular Carcinoma: Intrinsic and Extrinsic Molecular Mechanisms in Stemness Regulation

Hepatocellular carcinoma (HCC) remains the most predominant type of liver cancer with an extremely poor prognosis due to its late diagnosis and high recurrence rate. One of the culprits for HCC recurrence and metastasis is the existence of cancer stem cells (CSCs), which are a small subset of cancer cells possessing robust stem cell properties within tumors. CSCs play crucial roles in tumor heterogeneity constitution, tumorigenesis, tumor relapse, metastasis, and resistance to anti-cancer therapies. Elucidation of how these CSCs maintain their stemness features is essential for the development of CSCs-based therapy. In this review, we summarize the present knowledge of intrinsic molecules and signaling pathways involved in hepatic CSCs, especially the CSC surface markers and associated signaling in regulating the stemness characteristics and the heterogeneous subpopulations within the CSC pool. In addition, we recapitulate the effects of crucial extrinsic cellular components in the tumor microenvironment, including stromal cells and immune cells, on the modulation of hepatic CSCs. Finally, we synopsize the currently valuable CSCs-targeted therapy strategies based on intervention in these intrinsic and extrinsic molecular mechanisms, in the hope of shedding light on better clinical management of HCC patients.

Emerging Regulatory Mechanisms Involved in Liver Cancer Stem Cell Properties in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is the predominant form of primary liver cancer and one of the leading causes of cancer-related deaths worldwide. A growing body of evidence supports the hypothesis that HCC is driven by a population of cells called liver cancer stem cells (LCSCs). LCSCs have been proposed to contribute to malignant HCC progression, including promoting tumor occurrence and growth, mediating tumor metastasis, and treatment resistance, but the regulatory mechanism of LCSCs in HCC remains unclear. Understanding the signaling pathways responsible for LCSC maintenance and survival may provide opportunities to improve patient outcomes. Here, we review the current literature about the origin of LCSCs and the niche composition, describe the current evidence of signaling pathways that mediate LCSC stemness, then highlight several mechanisms that modulate LCSC properties in HCC progression, and finally, summarize the new developments in therapeutic strategies targeting LCSCs markers and regulatory pathways.

Chronic alcohol exposure promotes HCC stemness and metastasis through β-catenin/miR-22-3p/TET2 axis

Hepatocellular Carcinoma (HCC) patients usually have a high rate of relapse and metastasis. Alcohol, a risk factor for HCC, promotes the aggressiveness of HCC. However, the basic mechanism is still unclear. We used HCC cells and an orthotopic liver tumor model of HCC-LM3 cells for BALB/C nude mice to study the mechanism of alcohol-induced HCC progression. We showed that chronic alcohol exposure promoted HCC cells metastasis and pulmonary nodules formation. First, we identified miR-22-3p as an oncogene in HCC, which promoted HCC cells stemness, tumor growth, and metastasis. Further, we found that miR-22-3p directly targeted TET2 in HCC. TET2, a dioxygenase involved in cytosine demethylation, has pleiotropic roles in hematopoietic stem cells self-renewal. In clinic HCC specimen, TET2 expression was not only decreased by alcohol consumption, but also inversely correlated with miR-22-3p levels. Then, we demonstrated that TET2 depletion promoted HCC cells stemness, tumor growth and metastasis. Furthermore, we identified that β-catenin was an upstream activator of miR-22-3p. In conclusion, this study suggests that chronic alcohol exposure promotes HCC progression and β-catenin/miR-22-3p/TET2 regulatory axis plays an important role in alcohol-promoted HCC malignancy.

Could protein content of Urinary Extracellular Vesicles be useful to detect Cirrhosis in Alcoholic Liver Disease?

Alcohol abuse has a high impact on the mortality and morbidity related to a great number of diseases and is responsible for the development of alcoholic liver disease (ALD). It remains challenging to detect and evaluate its severity, which is crucial for prognosis. In this work, we studied if urinary EVs (uEVs) could serve in diagnose and evaluate cirrhosis in ALD. To this purpose, uEVs characterization by cryo-electron microscopy (Cryo-EM), Nanoparticle Tracking Analysis (NTA) and Western blotting (WB) was performed in a cohort of 21 controls and 21 cirrhotic patients. Then, proteomics of uEVs was carried out in a second cohort of 6 controls and 8 patients in order to identify new putative biomarkers for cirrhosis in ALD. Interestingly, uEVs concentration, size and protein composition were altered in cirrhotic patients. From a total of 1304 proteins identified in uEVs, 90 of them were found to be altered in cirrhotic patients. The results suggest that uEVs could be considered as a tool and a supplier of new biomarkers for cirrhosis in ALD, whose application would be especially relevant in chronic patients. Yet, further research is necessary to obtain more relevant result in clinical terms.

Interplay of autophagy and cancer stem cells in hepatocellular carcinoma

Liver cancer is the sixth most common cancer and the fourth leading cause of cancer deaths in the world. The most common type of liver cancers is hepatocellular carcinoma (HCC). Autophagy is the cellular digestion of harmful components by sequestering the waste products into autophagosomes followed by lysosomal degradation for the maintenance of cellular homeostasis. The impairment of autophagy is highly associated with the development and progression of HCC although autophagy may be involved in tumour-suppressing cellular events. In regards to its protecting role, autophagy also shelters the cells from anoikis- a programmed cell death in anchorage-dependent cells detached from the surrounding extracellular matrix which facilitates metastasis in HCC. Liver cancer stem cells (LCSCs) have the ability for self-renewal and differentiation and are associated with the development and progression of HCC by regulating stemness, resistance and angiogenesis. Interestingly, autophagy is also known to regulate normal stem cells by promoting cellular survival and differentiation and maintaining cellular homeostasis. In this review, we discuss the basal autophagic mechanisms and double-faceted roles of autophagy as both tumour suppressor and tumour promoter in HCC, as well as its association with and contribution to self-renewal and differentiation of LCSCs.

Cancer Stem Cell Functions in Hepatocellular Carcinoma and Comprehensive Therapeutic Strategies

Hepatocellular carcinoma (HCC) is a significant cause of cancer-related mortality owing to resistance to traditional treatments and tumor recurrence after therapy, which leads to poor therapeutic outcomes. Cancer stem cells (CSC) are a small subset of tumor cells with the capability to influence self-renewal, differentiation, and tumorigenesis. A number of surface markers for liver cancer stem cell (LCSC) subpopulations (EpCAM, CD133, CD44, CD13, CD90, OV-6, CD47, and side populations) in HCC have been identified. LCSCs play critical roles in regulating HCC stemness, self-renewal, tumorigenicity, metastasis, recurrence, and therapeutic resistance via genetic mutations, epigenetic disruption, signaling pathway dysregulation, or alterations microenvironment. Accumulating studies have shown that biomarkers for LCSCs contribute to diagnosis and prognosis prediction of HCC, supporting their utility in clinical management and development of therapeutic strategies. Preclinical and clinical analyses of therapeutic approaches for HCC using small molecule inhibitors, oncolytic measles viruses, and anti-surface marker antibodies have demonstrated selective, efficient, and safe targeting of LCSC populations. The current review focuses on recent reports on the influence of LCSCs on HCC stemness, tumorigenesis, and multiple drug resistance (MDR), along with LCSC-targeted therapeutic strategies for HCC.

Computational study of novel natural inhibitors targeting aminopeptidase N(CD13)

Objectives: To screen and identify ideal leading compounds from a drug library (ZINC15 database) with potential inhibition of aminopeptidase N(CD13) to contribute to medication design and development.

Results: Two novel natural compounds, ZINC000000895551 and ZINC000014820583, from the ZINC15 database were found to have a higher binding affinity and more favorable interaction energy binding with CD13 with less rodent carcinogenicity, Ames mutagenicity, and non-inhibition with cytochrome P-450 2D6. Molecular dynamics simulation analysis suggested that the 2 complexes, ZINC000000895551-CD13 and ZINC000014820583-CD13, have favorable potential energy, and exist stably in the natural circumstances.

Conclusion: This study discovered that ZINC000000895551 and ZINC000014820583 were ideal leading compounds to be inhibitions targeting to CD13. These compounds were selected as safe drug candidates as CD13 target medication design and improvement.

Materials and Method: Potential inhibitors of CD13 were identified using a series of computer-aided structural and chemical virtual screening techniques. Structure-based virtual screening was carried out to calculate LibDock scores, followed by analyzing their absorption, distribution, metabolism, and excretion and toxicity predictions. Molecule docking was employed to reveal binding affinity between the selected compounds and CD13. Molecular dynamics simulation was applied to evaluate stability of the ligand-CD13 complex under natural environment.

CD13 as a new tumor target for antibody-drug conjugates: validation with the conjugate MI130110

Background

In the search for novel antibody-drug conjugates (ADCs) with therapeutic potential, it is imperative to identify novel targets to direct the antibody moiety. CD13 seems an attractive ADC target as it shows a differential pattern of expression in a variety of tumors and cell lines and it is internalized upon engagement with a suitable monoclonal antibody. PM050489 is a marine cytotoxic compound tightly binding tubulin and impairing microtubule dynamics which is currently undergoing clinical trials for solid tumors.

Methods

Anti-CD13 monoclonal antibody (mAb) TEA1/8 has been used to prepare a novel ADC, MI130110, by conjugation to the marine compound PM050489. In vitro and in vivo experiments have been carried out to demonstrate the activity and specificity of MI130110.

Results

CD13 is readily internalized upon TEA1/8 mAb binding, and the conjugation with PM050489 did not have any effect on the binding or the internalization of the antibody. MI130110 showed remarkable activity and selectivity in vitro on CD13-expressing tumor cells causing the same effects than those described for PM050489, including cell cycle arrest at G2, mitosis with disarrayed and often multipolar spindles consistent with an arrest at metaphase, and induction of cell death. In contrast, none of these toxic effects were observed in CD13-null cell lines incubated with MI130110. Furthermore, in vivo studies showed that MI130110 exhibited excellent antitumor activity in a CD13-positive fibrosarcoma xenograft murine model, with total remissions in a significant number of the treated animals. Mitotic catastrophes, typical of the payload mechanism of action, were also observed in the tumor cells isolated from mice treated with MI130110. In contrast, MI130110 failed to show any activity in a xenograft mouse model of myeloma cells not expressing CD13, thereby corroborating the selectivity of the ADC to its target and its stability in circulation.

Conclusion

Our results show that MI130110 ADC combines the antitumor potential of the PM050489 payload with the selectivity of the TEA1/8 monoclonal anti-CD13 antibody and confirm the correct intracellular processing of the ADC. These results demonstrate the suitability of CD13 as a novel ADC target and the effectiveness of MI130110 as a promising antitumor therapeutic agent.

The Cancer Stem Cell in Hepatocellular Carcinoma

The recognition of intra-tumoral cellular heterogeneity has given way to the concept of the cancer stem cell (CSC). According to this concept, CSCs are able to self-renew and differentiate into all of the cancer cell lineages present within the tumor, placing the CSC at the top of a hierarchical tree. The observation that these cells—in contrast to bulk tumor cells—are able to exclusively initiate new tumors, initiate metastatic spread and resist chemotherapy implies that CSCs are solely responsible for tumor recurrence and should be therapeutically targeted. Toward this end, dissecting and understanding the biology of CSCs should translate into new clinical therapeutic approaches. In this article, we review the CSC concept in cancer, with a special focus on hepatocellular carcinoma.

Mitotic quiescence in hepatic cancer stem cells: An incognito mode

Hepatocellular carcinoma represents one of the most aggressive cancers with high recurrence rates. The high recurrence is a major problem in the management of this disease. Cancer stem cells (CSCs) are often regarded as the basis of cancer recurrence. The anti-proliferative therapy kills the proliferating cells but induces mitotic quiescence in CSCs which remain as residual dormant CSCs. Later on, withdrawal of treatment reactivates the residual CSCs from dormancy to produce new cancer cells. The proliferation of these newly formed cancer cells initiates new tumor formation in the liver leading to tumor recurrence. HCC cells evade the immune surveillance via modulating the key immune cells by alpha feto-protein (AFP) secreted from CSCs or hepatic progenitor cells. This AFP mediated immune evasion assists in establishing new tumors by cancer cells in the liver. In this review, we will summarise the CSC mechanisms of recurrence, mitotic quiescence, dormancy and reactivation of CSCs, metastasis and immune evasion of hepatocellular carcinoma.

Liver resection with thrombectomy for patients with hepatocellular carcinoma and tumour thrombus in the inferior vena cava or right atrium

Background

Hepatocellular carcinoma (HCC) with tumour thrombus (TT) in the inferior vena cava (IVC) or right atrium (RA) is a rare advanced disease state with a poor prognosis. The aim of this study was to examine survival after surgical resection.

Methods

Patients with HCC and TT of either the IVC or RA, who underwent liver resection between February 1997 and July 2017, were included. Their short‐ and long‐term outcomes and surgical details were analysed retrospectively.

Results

Thirty‐seven patients were included; 16 patients had TT in the IVC below the diaphragm, eight had TT in the IVC above the diaphragm, and 13 had TT entering the RA. Twelve patients had advanced portal vein TT (portal vein invasion (Vp) greater than Vp3 and Vp4), ten had bilobar disease, and 12 had extrahepatic disease. There were no in‐hospital deaths, although two patients died within 90 days. Median survival did not differ between patients who had resection with curative intent (18·7 months) and those with residual tumour in the lung only (20·7 months), but survival was poor for patients with residual tumour in the liver (8·3 months).

Conclusion

Liver resection with thrombectomy for advanced HCC with TT in the IVC or RA is safe and feasible, leading to moderate survival.

Epithelial Mesenchymal and Endothelial Mesenchymal Transitions in Hepatocellular Carcinoma: A Review

PURPOSE

To present a comprehensive review of the literature data, published between 2000 and 2019 on the PubMed and Web of Science databases, in the field of the tumor microenvironment in hepatocellular carcinoma (HCC). All the data were combined with the personal experiences of the authors.

DESIGN

From 1002 representative papers, we selected 86 representative publications which included data on epithelial-to-mesenchymal transition (EMT), angiogenesis, cancer stem-like cells (CSCs), and molecular background of chemoresistance or resistance to radiotherapy.

RESULTS

Although the central event concerns activation of the Wnt/β-catenin pathway, other signal pathways, such as c-Met/HGF/Snail, Notch-1/NF-κB, TGF-β/SMAD, and basic fibroblast growth factor-related signaling, play a role in the EMT of HCC cells. This pathway is targeted by specific miRNAs and long noncoding RNAs, as explored in this paper. A central player in the tumor microenvironment proved to be the CSCs which can be marked by CD133, CD44, CD90, EpCAM, and CD105. CSCs can induce resistance to cytotoxic therapy or, alternatively, can be synthesized, de novo, after chemo- or radiotherapy, especially after transarterial chemoembolization- or radiofrequency ablation-induced hypoxia. The circulating tumor cells proved to have epithelial, intermediate, or mesenchymal features; their properties have a critical prognostic role.

CONCLUSION

The metastatic pathway of HCC seems to be related to the Wnt- or, rather, TGFβ1-mediated inflammation-angiogenesis-EMT-CSCs crosstalk link. Molecular therapy should target this molecular axis controlling the HCC microenvironment.

Heterogeneity of Hepatic Cancer Stem Cells

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

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.

Long non-coding RNA THOR promotes liver cancer stem cells expansion via β-catenin pathway

Hepatocellular carcinoma (HCC) is a highly aggressive liver tumor containing cancer stem cells (CSCs), which participate in tumor invasion, therapeutic resistance, and tumor relapse leading to poor outcome and limited therapeutic options. Recently, a novel lncRNA, THOR (testis-associated highly conserved oncogenic long non-coding RNA), was characterized in human cancers and shown to exhibit an oncogenic role. However, the role of THOR in liver cancer stem cells (CSCs) remains obscure. Herein, we observed high expression of THOR in chemoresistant hepatocellular carcinomas (HCCs). A remarkable increase of THOR expression in OV6 or EpCAM-positive liver CSCs as well as in CSC-enriched hepatoma spheres. Interference THOR suppressed liver CSC expansion by inhibiting the dedifferentiation of hepatoma cells and decreasing the self-renewal ability of liver CSCs. Mechanistically, we found β-catenin as the downstream of THOR in HCC cells. The special β-catenin inhibitor FH535 abolished the discrepancy in liver CSC proportion and the self-renewal capacity between THOR knockdown HCC cells and control cells, which further confirmed that β-catenin was required in THOR promoted liver CSCs expansion. Moreover, interference THOR hepatoma cells were more sensitive to sorafenib treatment, indicates that HCC patients with low THOR expression may benefit from sorafenib treatment. Collectively, THOR was upregulated in liver CSCs and could promote HCC cells dedifferentiation and liver CSCs expansion by targeting β-catenin signaling.

Functional Role of Non-Coding RNAs during Epithelial-To-Mesenchymal Transition

Epithelial-to-mesenchymal transition (EMT) is a key biological process involved in a multitude of developmental and pathological events. It is characterized by the progressive loss of cell-to-cell contacts and actin cytoskeletal rearrangements, leading to filopodia formation and the progressive up-regulation of a mesenchymal gene expression pattern enabling cell migration. Epithelial-to-mesenchymal transition is already observed in early embryonic stages such as gastrulation, when the epiblast undergoes an EMT process and therefore leads to the formation of the third embryonic layer, the mesoderm. Epithelial-to-mesenchymal transition is pivotal in multiple embryonic processes, such as for example during cardiovascular system development, as valve primordia are formed and the cardiac jelly is progressively invaded by endocardium-derived mesenchyme or as the external cardiac cell layer is established, i.e., the epicardium and cells detached migrate into the embryonic myocardial to form the cardiac fibrous skeleton and the coronary vasculature. Strikingly, the most important biological event in which EMT is pivotal is cancer development and metastasis. Over the last years, understanding of the transcriptional regulatory networks involved in EMT has greatly advanced. Several transcriptional factors such as Snail, Slug, Twist, Zeb1 and Zeb2 have been reported to play fundamental roles in EMT, leading in most cases to transcriptional repression of cell⁻cell interacting proteins such as ZO-1 and cadherins and activation of cytoskeletal markers such as vimentin. In recent years, a fundamental role for non-coding RNAs, particularly microRNAs and more recently long non-coding RNAs, has been identified in normal tissue development and homeostasis as well as in several oncogenic processes. In this study, we will provide a state-of-the-art review of the functional roles of non-coding RNAs, particularly microRNAs, in epithelial-to-mesenchymal transition in both developmental and pathological EMT.