Liver cancer stem cells: implications for a new therapeutic target

Hepatocellular carcinoma (HCC) is an aggressive tumour with a poor prognosis. Current therapeutic strategies against this disease target mostly rapidly growing differentiated tumour cells. However, the result is often dismal due to the chemoresistant nature of this tumour type. Recent research efforts on stem cells and cancer biology have shed light on new directions for the eradication of cancer stem cells (CSCs) in HCC. The liver is a distinctive organ with the ability of tissue renewal in response to injury. Based on the hypothesis that cancer development is derived from the hierarchy of the stem cell system, we will briefly discuss the origin of liver stem cells and its relation to HCC development. We will also summarize the current CSC markers in HCC and discuss their relevance to the treatment of this deadly disease.     

Liver cancer stem cell markers: Progression and therapeutic implications

Cancer stem cells(CSCs) are a small subpopulation in cancer, have been proposed to be cancer-initiating cells, and have been shown to be responsible for chemotherapy resistance and cancer recurrence. The identification of CSC subpopulations inside a tumor presents a new understanding of cancer development because it implies that tumors can only be eradicated by targeting CSCs. Although advances in liver cancer detection and treatment have increased the possibility of curing the disease at early stages, unfortunately, most patients will relapse and succumb to their disease. Strategies aimed at efficiently targeting liver CSCs are becoming important for monitoring the progress of liver cancer therapy and for evaluating new therapeutic approaches. Herein, we provide a critical discussion of biological markers described in the literature regarding liver cancer stem cells and the potential of these markers to serve as therapeutic targets.     

Current status and perspectives of immune-based therapies for hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a frequent cancer with a high mortality. For early stage cancer there are potentially curative treatments including local ablation, resection and liver transplantation. However, for more advanced stage disease, there is no optimal treatment available. Even in the case of a “curative” treatment, recurrence or development of a new cancer in the precancerous liver is common. Thus, there is an urgent need for novel and effective (adjuvant) therapies to treat HCC and to prevent recurrence after local treatment in patients with HCC. The unique immune response in the liver favors tolerance, which remains a genuine challenge for conventional immunotherapy in patients with HCC. However, even in this “immunotolerant” organ, spontaneous immune responses against tumor antigens have been detected, although they are insufficient to achieve significant tumor death. Local ablation therapy leads to immunogenic tumor cell death by inducing the release of massive amounts of antigens, which enhances spontaneous immune response. New immune therapies such as dendritic cell vaccination and immune checkpoint inhibition are under investigation. Immunotherapy for cancer has made huge progress in the last few years and clinical trials examining the use of immunotherapy to treat hepatocellular carcinoma have shown some success. In this review, we discuss the current status of and offer some perspectives on immunotherapy for hepatocellular carcinoma, which could change disease progression in the near future.     

Oncolytic viruses against cancer stem cells: A promising approach for gastrointestinal cancer

Gastrointestinal cancer has been one of the five most commonly diagnosed and leading causes of cancer mortality over the past few decades. Great progress in traditional therapies has been made, which prolonged survival in patients with early cancer, yet tumor relapse and drug resistance still occurred, which is explained by the cancer stem cell(CSC) theory. Oncolytic virotherapy has attracted increasing interest in cancer because of its ability to infect and lyse CSCs. This paper reviews the basic knowledge, CSC markers and therapeutics of gastrointestinal cancer(liver, gastric, colon and pancreatic cancer), as well as research advances and possible molecular mechanisms of various oncolytic viruses against gastrointestinal CSCs. This paper also summarizes the existing obstacles to oncolytic virotherapy and proposes several alternative suggestions to overcome the therapeutic limitations.     

Research progress and prospects of markers for liver cancer stem cells

Liver cancer is a common malignancy and surgery is the main treatment strategy. However, the prognosis is still poor because of high frequencies of postoperative recurrence and metastasis. In recent years, cancer stem cell(CSC) theory has evolved with the concept of stem cells, and has been applied to oncological research. According to cancer stem cell theory, liver cancer can be radically cured only by eradication of liver cancer stem cells(LCSCs). This notion has lead to the isolation and identification of LCSCs, which has become a highly researched area. Analysis of LCSC markers is considered to be the primary method for identification of LCSCs. Here, we provide an overview of the current research progress and prospects of surface markers for LCSCs.     

Cancer stem cell markers correlate with early recurrence and survival in hepatocellular carcinoma

AIM:To investigate whether expression of cancer stem cell(CSC)markers is associated with recurrence and survival in hepatocellular carcinoma(HCC)patients.METHODS:A consecutive series of 90 HCC patients who underwent curative hepatectomy between April2007 and April 2009 were analyzed.Of the 90 patients,38(42%)experienced recurrence within two years of surgery.To adjust for baseline differences between this early recurrence group and the other patients,propensity-score matching was used to generate 25 pairs of patients.Immunohistochemistry was used to compare expression of CD133,CD90,and epithelial cell adhesion molecule(EpCAM)in liver tissues from propensity score-matched patients and from 10 healthy adults.Associations of the three markers with HCC,clinicopathological characteristics,early recurrence,and survival time were explored.RESULTS:The expression of all three CSC markers was significantly higher in HCC tissue than in healthy liver tissue(P<0.001 for all).Among the HCC clinicopathology characteristics examined,the absence of tumor capsule was associated with CD133 expression(P=0.005);higher histopathology grade and larger tumor size were associated with CD90 expression(P=0.010 and 0.034,respectively);and elevated serum alpha-fetoprotein levels were associated with EpCAM expression(P=0.021).Expression of CD90 and EpCAM was significantly higher in the early recurrence group than in other patients(P=0.001 and 0.045,respectively),whereas CD133 expression was not significantly different between the two groups(P=0.440).Multivariate analysis identified only CD90 expression as significantly associated with early recurrence.Log-rank analysis identified expression of both CD90 and EpCAM as significantly associated with survival time of HCC patients.Cox regression identified EpCAM expression as an independent predictor of survival time.CONCLUSION:Expression of CD133,CD90,and EpCAM CSC markers may be linked to HCC tumor onset and/or progression.In addition,EpCAM expression is associated with shorter survival time,while CD90 expression is associated with early HCC recurrence.     

Role of innate immunity in the development of hepatocellular carcinoma

Hepatocellular carcinoma(HCC)is the most common form of liver cancer worldwide.It is caused by a variety of risk factors,most common ones being infection with hepatitis viruses,alcohol,and obesity.HCC often develops in the background of underlying cirrhosis,and even though a number of interventional treatment methods are currently in use,recurrence is fairly common among patients who have had a resection.Therefore,whole liver transplantation remains the most practical treatment option for HCC.Due to the growing incidence of HCC,intense research efforts are being made to understand cellular and molecular mechanisms of the disease so that novel therapeutic strategies can be developed to combat liver cancer.In recent years,it has become clear that innate immunity plays a critical role in the development of a number of liver diseases,including HCC.In particular,the activation of Toll-like receptor signaling results in the generation of immune responses that often results in the production of proinflammatory cytokines and chemokines,and could cause acute inflammation in the liver.In this review,the current knowledge on the role of innate immune responses in the development and progression of HCC is examined,and emerging therapeutic strategies based on molecular mechanisms of HCC are discussed.     

Identification and characterization of tumorigenic liver cancer stem/progenitor cells

BACKGROUND & AIMS: Recent efforts in stem cell biology suggest that tumors are organized in a hierarchy of heterogeneous cell populations and that the capability to maintain tumor formation/growth specifically resides in a small population of cells called cancer stem cells (CSCs). The aim of this study is to identify, isolate, and characterize the CSC population that drives and maintains hepatocellular carcinoma (HCC) growth and metastasis. METHODS: Normal stem cells involved in liver regeneration were identified using a severe partial hepatectomy model. Purified HCC cells, with or without expression of the identified normal stem cell phenotype, were evaluated, based on their tumorigenic potential and exhibition of defined stem/progenitor cell-like properties, to determine whether liver CSCs can be or partly be identified by this surface marker. RESULTS: We report the identification and isolation of a population of CSCs expressing a CD133 surface phenotype from human liver cell lines. CD133(+) cells possess a greater colony-forming efficiency, higher proliferative output, and greater ability to form tumor in vivo. These cells are endowed with characteristics similar to those of progenitor cells including the expression of "stemness" genes, the ability to self-renew, and the ability to differentiate into nonhepatocyte-like lineages. Furthermore, CD133 is found to represent only a minority of the tumor cell population in human HCC specimens. CONCLUSIONS: We report the identification of a CSC population in HCC characterized by their CD133 phenotype. The identification of tumorigenic liver CSCs could provide new insight into the HCC tumorigenic process and possibly bear great therapeutic implications.     

The biology of cancer stem cells and its clinical implication in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a highly malignant tumor with limited treatment options in its advanced state. The molecular mechanisms underlying HCC remain unclear because of the complexity of its multi-step development process. Cancer stem cells (CSCs) are defined as a small population of cells within a tumor that possess the capability for self-renewal and the generation of heterogeneous lineages of cancer cells. To date, there have been two theories concerning the mechanism of carcinogenesis, i.e., the stochastic (clonal evolution) model and the hierarchical (cancer stem cell-driven) model. The concept of the CSC has been established over the past decade, and the roles of CSCs in the carcinogenic processes of various cancers, including HCC, have been emphasized. Previous experimental and clinical evidence indicated the existence of liver CSCs; however, the potential mechanistic links between liver CSCs and the development of HCC in humans are not fully understood. Although definitive cell surface markers for liver CSCs have not yet been found, several putative markers have been identified, which allow the prospective isolation of CSCs from HCC. The identification and characterization of CSCs in HCC is essential for a better understanding of tumor initiation or progression in relation to signaling pathways. These markers could be used along with clinical parameters for the prediction of chemoresistance, radioresistance, metastasis and survival and may represent potential targets for the development of new molecular therapies against HCC. This review describes the current evidence for the existence and function of liver CSCs and discuss the clinical implications of CSCs in patients demonstrating resistance to conventional anti-cancer therapies, as well as clinical outcomes. Such data may provide a future perspective for targeted therapy in HCC.     

Ablative strategies for recurrent hepatocellular carcinoma

Hepatocellular carcinoma(HCC) is the most common primary liver cancer and is the fifth leading cause of cancer death worldwide and the third leading cause of all diseases worldwide. Liver transplantation, surgical resection and ablation are the three main curative treatments for HCC. Liver transplantation is the optimal treatment option for HCC, but its usage is limited by the shortage of liver sources.Surgical resection is considered the first choice for early-stage HCC, but it does not apply t...     

RhoGTPases and Rho‐effectors in hepatocellular carcinoma metastasis: ROCK N' Rho move it

Hepatocellular carcinoma (HCC) is an intractable disease with an extremely high mortality rate. Metastasis is the major factor of liver failure, tumour recurrence and death in HCC patients. Unfortunately, no promising curative therapy for HCC metastasis is available as yet; therefore, treatment for advanced HCC still remains a formidable challenge. A large body of evidence has demonstrated that the RhoGTPases/Rho‐effector pathway plays important roles in mediating HCC metastasis based on their foremost functions in orchestrating the cell cytoskeletal reorganization. This review will first discuss the general principles of cancer metastasis and cancer cell movement with a particular focus on HCC. We will then summarize the implications of various members in the RhoGTPases/Rho‐effectors signalling cascade including the upstream RhoGTPase regulators RhoGTPases and Rho‐effectors and their downstream targets in HCC metastasis. Finally, we will discuss the therapeutic insight of targeting the RhoGTPases/Rho‐effector pathway in HCC. Taken together, the literature demonstrates the importance of the RhoGTPases/Rho‐effector signalling pathway in HCC metastasis and marks the necessity to have a more thorough knowledge of this complicated signalling network in order to develop novel therapeutic strategies for HCC patients.     

Predictors of recurrence and survival of hepatocellular carcinoma: A prospective study including transient elastography and cancer stem cell markers

Background and Study AimsTo investigate whether the measurement of liver stiffness (LSM) using fibroscan and the serum Cancer Stem Cells (CSC): Ep-CAM and cytokeratin-19, could predict the recurrence of hepatocellular carcinoma (HCC) and their impact on clinical outcome and overall survival.Patients and MethodsThis is a prospective study, including 179 HCV-related HCC patients. All patients were treated following the BCLC guidelines. All HCC patients had transient elastography, measurements of Ep-CAM and cytokeratin-19 before and six months post-treatment. We looked for predictors of recurrence and performed a survival analysis using Kaplan-Meier estimates.ResultsTACE was the most common procedure (77.1%), followed by microwave ablation (15.6%). Complete ablation was achieved in 97 patients; 55 of them developed HCC recurrence. After treatment, LSM increased significantly with a significant reduction in CSCs levels in complete and partial response groups. The median time to observe any recurrence was 14 months. LSM increased significantly post-treatment in patients with recurrence versus no recurrence. Higher levels of CSCs were recorded at baseline and post-treatment in patients with recurrence but without statistical significance. We used univariate analysis to predict the time of recurrence by determining baseline CK-19 and platelet levels as the key factors, while the multivariate analysis determined platelet count as a single factor. The univariate analysis for prediction of overall survival included several factors, LSM and EpCAM (baseline and post-ablation) among them, while multivariate analysis included factors such as Child score B and incomplete ablation.ConclusionDynamic changes were observed in LSM and CSCs levels in response to HCC treatment and tumour recurrence. Child score and complete ablation are factors that significantly affect survival.     

MicroRNAs and liver cancer associated with iron overload: Therapeutic targets unravelled

Primary liver cancer is a global disease that is on the increase.Hepatocellular carcinoma(HCC)accounts for most primary liver cancers and has a notably low survival rate,largely attributable to late diagnosis,resistance to treatment,tumour recurrence and metastasis.MicroRNAs(miRNAs/miRs)are regulatory RNAs that modulate protein synthesis.miRNAs are involved in several biological and pathological processes including the development and progression of HCC.Given the poor outcomes with current HCC treatments,miRNAs represent an important new target for therapeutic intervention.Several studies have demonstrated their role in HCC development and progression.While many risk factors underlie the development of HCC,one process commonly altered is iron homeostasis.Iron overload occurs in several liver diseases associated with the development of HCC including Hepatitis C infection and the importance of miRNAs in iron homeostasis and hepatic iron overload is well characterised.Aberrant miRNA expression in hepatic fibrosis and injury response have been reported,as have dysregulated miRNA expression patterns affecting cell cycle progression,evasion of apoptosis,invasion and metastasis.In2009,miR-26a delivery was shown to prevent HCC progression,highlighting its therapeutic potential.Several studies have since investigated the clinical potential of other miRNAs with one drug,Miravirsen,currently in phaseⅡclinical trials.miRNAs also have potential as biomarkers for the diagnosis of HCC and to evaluate treatment efficacy.Ongoing studies and clinical trials suggest miRNA-based treatments and diagnostic methods will have novel clinical applications for HCC in the coming years,yielding improved HCC survival rates and patient outcomes.     

Liver transplantation for hepatocellular carcinoma

The role of liver transplantation (LT) in patients with hepatocellular carcinoma (HCC) has evolved over the past two decades, and transplantation has become one of the few curative treatment modalities for patients with HCC. Early results were poor, but the current restrictive selection criteria can yield excellent results. This review will discuss recent issues in the field, including (1) factors affecting the recurrence of HCC after LT; (2) the effect of downstaging HCC before LT, including transarterial catheter chemoembolization (TACE) and radiofrequency ablation (RFA); and (3) living-donor versus deceased-donor liver transplantation for HCC patients. The most important factors that have been described to affect LT survival include the tumor size, vascular invasion, and the degree of tumor differentiation. Recently, tumor markers, including alpha-fetoprotein and des-gamma carboxy prothrombin, were reported as predictors of HCC recurrence after LT. Furthermore, the experience accumulated with locoregional therapies such as TACE and RFA as bridging procedures to LT, along with the reduced waiting time under the HCC-adjusted MELD (model for endstage liver disease) system for organ allocation has led to improved outcomes. With the recent advances in adult living-donor liver transplantation (LDLT), there may be a marked change in the role of liver transplantation for hepatic malignancies, in particular for HCC.     

二甲双胍对肝癌PLC/PRF/5肿瘤干细胞增殖分化、凋亡、迁移的影响

目的:探究二甲双胍对肝癌PLC/PRF/5肿瘤干细胞(CSC)增殖分化、凋亡、迁移的影响。方法:体外特殊条件培养法培养PLC/PRF/5 CSC细胞,用不同浓度(5、10、20 mmol/L)二甲双胍处理PLC/PRF/5 CSC,以未进行处理的PLC/PRF/5 CSC为对照组,在显微镜下观察细胞形态;CCK-8法检测各组细胞活力;流式细胞术检测各组细胞凋亡率;划痕实验检测各组细胞迁移能力;蛋白免疫印迹法检测各组细胞蛋白表达情况;构建裸鼠肝癌移植瘤模型,检测二甲双胍对PLC/PRF/5 CSC成瘤能力的影响。结果:PLC/PRF/5 CSC具有成球能力,经二甲双胍处理后,PLC/PRF/5成球细胞数目显著减少;同一时间段,与对照组比较,二甲双胍处理组细胞活力显著降低,且呈剂量依赖性(P<0.05),随着处理时间的增加,各组细胞活力逐渐降低;与对照组比较,二甲双胍处理组细胞凋亡率、凋亡蛋白Caspase-3、Caspase-9、迁移蛋白E-cadherin的表达显著升高,细胞迁移率、细胞干性基因Oct4、Nanog蛋白表达、迁移蛋白N-cadherin的表达显著降低,且呈剂量依赖性(P<0.05);与对照组比较,随着接种时间的增加,二甲双胍处理组裸鼠肿瘤生长速度较慢(P<0.05),且随着二甲双胍浓度的增加,裸鼠肿瘤生长速度逐渐变慢。结论:二甲双胍能够抑制肝癌PLC/PRF/5 CSC的增殖和迁移,促进其凋亡,可能是靶向肝癌CSC治疗的潜在药物。     

Treatment of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the fifth most common cancer in the world, and is the third highest cause of cancer-related mortality. HCC usually develops in patients with chronic liver disease, particularly in those who also have cirrhosis. The possibility of curative treatment depends on both the stage of tumor and liver function. Effective treatments for HCC include percutaneous ablation, surgical resection, and liver transplantation. Both percutaneous ablation and surgical resection provide a high rate of complete responses and are assumed to improve survival that should exceed 50% at 5 years. Liver transplantation results in a better survival rate, and is not contraindicated by advanced liver dysfunction. However, its application is limited by the scarcity of donor organs. Treatments for advanced HCC include transarterial chemoembolization and chemotherapy. Although short-term prognosis of HCC patients has improved recently due to advances in early diagnosis and treatment, long-term prognosis is as yet far from satisfactory due to frequent recurrence. Prevention of recurrence of HCC remains one of the most challenging tasks in current hepatology.     

Targeting Wnt/β-catenin pathway in hepatocellular carcinoma treatment

Hepatocellular carcinoma(HCC) is one of the most common causes of cancer-related death worldwide. Liver cancer is generally related to hepatitis B or Cinfection and cirrhosis. Usually, patients with HCC are asymptomatic and are diagnosed at late stages when surgical treatment is no longer suitable. Limited treatment options for patients with advanced HCC are a major concern. Therefore, there is an urge for finding novel therapies to treat HCC. Liver cancer is highly heterogeneous and involved deregulation of several signaling pathways. Wnt/β-catenin pathway is frequently upregulated in HCC and it is implicated in maintenance of tumor initiating cells, drug resistance, tumor progression, and metastasis. A great effort in developing selective drugs to target components of the β-catenin pathway with anticancer activity is underway but only a few of them have reached phase Ⅰ clinical trials. We aim to review the role of β-catenin pathway on hepatocarcinogenesis and liver cancer stem cell maintenance. We also evaluated the use of small molecules targeting the Wnt/β-catenin pathway with potential application for treatment of HCC.     

Hepatic stem cells and transforming growth factor β in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most common and lethal cancers worldwide. It arises from modulation of multiple genes by mutations, epigenetic regulation, noncoding RNAs and translational modifications of encoded proteins. Although >40% of HCCs are clonal and thought to arise from cancer stem cells (CSCs), the precise identification and mechanisms of CSC formation remain poorly understood. A functional role of transforming growth factor (TGF)-β signalling in liver and intestinal stem cell niches has been demonstrated through mouse genetics. These studies demonstrate that loss of TGF-β signalling yields a phenotype similar to a human CSC disorder, Beckwith-Wiedemann syndrome. Insights into this powerful pathway will be vital for developing new therapeutics in cancer. Current clinical approaches are aimed at establishing novel cancer drugs that target activated pathways when the TGF-β tumour suppressor pathway is lost, and TGF-β itself could potentially be targeted in metastases. Studies delineating key functional pathways in HCC and CSC formation could be important in preventing this disease and could lead to simple treatment strategies; for example, use of vitamin D might be effective when the TGF-β pathway is lost or when wnt signalling is activated.