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Review

Novel Aspects of the Liver Microenvironment in Hepatocellular Carcinoma Pathogenesis and Development

1
Liver Cell Biology, Centenary Institute, Sydney, NSW 2050, Australia
2
Morrow Gastroenterology and Liver Centre, Royal Prince Alfred Hospital, Sydney, NSW 2050, Australia
3
Sydney Medical School, University of Sydney, Sydney, NSW 2006, Australia
4
School of Medicine, University of Adelaide, Adelaide, SA 5005, Australia
5
Department of Endocrinology, Royal Prince Alfred Hospital, Sydney, NSW 2050, Australia
*
Author to whom correspondence should be addressed.
Int. J. Mol. Sci. 2014, 15(6), 9422-9458; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms15069422
Submission received: 7 March 2014 / Revised: 13 May 2014 / Accepted: 14 May 2014 / Published: 27 May 2014
(This article belongs to the Special Issue Molecular Mechanisms of Human Liver Diseases)

Abstract

:
Hepatocellular carcinoma (HCC) is a prevalent primary liver cancer that is derived from hepatocytes and is characterised by high mortality rate and poor prognosis. While HCC is driven by cumulative changes in the hepatocyte genome, it is increasingly recognised that the liver microenvironment plays a pivotal role in HCC propensity, progression and treatment response. The microenvironmental stimuli that have been recognised as being involved in HCC pathogenesis are diverse and include intrahepatic cell subpopulations, such as immune and stellate cells, pathogens, such as hepatitis viruses, and non-cellular factors, such as abnormal extracellular matrix (ECM) and tissue hypoxia. Recently, a number of novel environmental influences have been shown to have an equally dramatic, but previously unrecognized, role in HCC progression. Novel aspects, including diet, gastrointestinal tract (GIT) microflora and circulating microvesicles, are now being recognized as increasingly important in HCC pathogenesis. This review will outline aspects of the HCC microenvironment, including the potential role of GIT microflora and microvesicles, in providing new insights into tumourigenesis and identifying potential novel targets in the treatment of HCC.

1. Introduction

Liver cancer is the fifth most common malignancy globally [1,2,3]. Primary liver cancers include cholangiocarcinomas, hepatoblastomas, and hepatocellular carcinomas (HCC), of which the latter accounts for >90% of primary liver cancers with 500,000–1,000,000 new cases being diagnosed globally annually [1,4,5,6]. HCC is associated with a poor five-year survival rate, leading to ~600,000 deaths each year [7,8]. The worldwide distribution of HCC patients correlates strongly with the incidence of chronic hepatitis B virus (HBV) and hepatitis C virus (HCV) infections, which are present in 75%–85% of people with HCC [5,9,10,11]. The four major risk factors for HCC include: (1) underlying cirrhosis; (2) chronic HBV infection; (3) chronic HCV infection; and (4) exposure to the food-borne mycotoxin aflatoxin B1 (AFB1) [5,12,13,14]. HCC generally occurs late in life and on a background of progressive chronic liver injury, typically over years to decades [3]. In the past, it was generally accepted that HCC occurs as a result of the transformation of hepatocytes, the main cell of the liver. However, the multitude of subtypes and phenotypes of HCC, e.g., progenitor cell phenotype [15], suggest that HCC can originate from other liver cell types including liver progenitor cells [16]. In this review, we will discuss the growing body of evidence that the progression of HCC is not only due to the molecular changes in hepatocytes, but is also influenced by an increasing list of mediators in the liver microenvironment, i.e., surrounding non-hepatocyte cells, non-host microbes (e.g., the GIT microflora) and non-cellular factors (e.g., microvesicles).

2. Overview

This review is divided into four main sections:
  • A discussion of the molecular alterations that occur with HCC.
  • A review of the well-established microenvironmental contributors to HCC and their mechanisms.
  • A description of novel microenvironmental factors whose effects on HCC initiation and development are incompletely understood.
  • An exploration of the clinical impact of novel microenvironmental contributors to HCC initiation and development.

3. Hepatocellular Carcinoma

3.1. Background

The composition of the liver includes hepatocytes and non-hepatocellular cell types [17,18]. Hepatocytes are the main functional parenchymal liver cells that perform the majority of the metabolic duties of the liver. The non-hepatocyte cell types include: (1) stromal cells, such as hepatic stellate cells and fibroblasts, which play a structural role and are responsible for ECM production; (2) immune cells, which mainly consist of resident macrophages (Kupffer cells) in physiological settings, but can include a range of inflammation-recruited leukocytes; (3) epithelial cells lining the bile ducts (cholangiocytes); (4) endothelial cells, which line the blood vessels (liver sinusoidal endothelial cells; LSECs); and (5) liver progenitor cell populations (called oval cells in mice) which give rise to both hepatocyte and non-hepatocyte intrahepatic cell populations. The non-hepatocyte cell types may influence both the initiation and progression of HCC [16,19]. Infectious pathogens, including hepatitis viruses, also contribute to malignant intrahepatic transformation [9,12,20]. Further, non-cellular factors, which include hypoxia and altered ECM, can drive the transformation process through paracrine signaling by surrounding stromal tissue [21]. The contribution of all of these established factors to the development and maintenance of malignant cells is highly interconnected (Figure 1) and has been described in detail in several reviews [22,23,24].
Figure 1. A simplified network of liver microenvironmental factors and their roles in HCC tumour progression and maintenance. Established causal interactions between microenvironmental factors (italicised within the dashed circle) and HCC tumour progression and maintenance are represented by solid arrows, while dashed arrows are interactions that have not yet been conclusively shown. Some known interactions are not shown for clarity. In this review, we describe the direct effects of the liver microenvironment on this network (bold): chronic inflammation; tissue remodeling; genetic alterations; and altered cellular expression. ROS = Reactive Oxygen Species; HBV = Hepatitis B Virus; HCV = Hepatitis C virus; GIT = Gastrointestinal Tract; ECM = Extracellular Matrix.
Figure 1. A simplified network of liver microenvironmental factors and their roles in HCC tumour progression and maintenance. Established causal interactions between microenvironmental factors (italicised within the dashed circle) and HCC tumour progression and maintenance are represented by solid arrows, while dashed arrows are interactions that have not yet been conclusively shown. Some known interactions are not shown for clarity. In this review, we describe the direct effects of the liver microenvironment on this network (bold): chronic inflammation; tissue remodeling; genetic alterations; and altered cellular expression. ROS = Reactive Oxygen Species; HBV = Hepatitis B Virus; HCV = Hepatitis C virus; GIT = Gastrointestinal Tract; ECM = Extracellular Matrix.
Ijms 15 09422 g001

3.2. HCC Diagnosis and Treatment

HCC is diagnosed by a combination of ultrasound imaging, computer tomography (CT) imaging, magnetic resonance imaging (MRI) and measurement of serum alpha-fetoprotein (AFP) levels [25]. Implementation of surveillance programs in high-risk patients has led to increased diagnosis of HCC in early (defined by the Milan criteria as a solitary tumour <5 cm, or <3 tumours, with all tumours <3 cm), asymptomatic stages [26]. If HCC is detected in this stage, surgical interventions—i.e., partial liver resection or liver transplant—are available as effective curative treatments for HCC [27]. In these cases, the median 5-year survival rate is ~70% [28,29].
Despite these programs, diagnosis of HCC still usually occurs in the late stages of progression [10,11,30], a factor which likely contributes to the poor (20%–25%) response rate to treatments with curative intent [10,11,30,31]. Treatments at late stages to control HCC burden or progression—such as administration of the small molecule tyrosine-kinase inhibitor Sorafenib, percutaneous ethanol injection, transarterial chemoembolisation (TACE), and radiofrequency ablation—are rarely curative [32,33]. The chemoresistance associated with HCC is caused by multiple mechanisms: the up-regulation of pathways in the tumour to limit uptake or induce metabolism of chemotherapeutics; the inhibition of chemotherapeutic activity due to the hypoxic environment of the tumour and cirrhotic tissues; and potentially the slow-dividing “HCC stem cell” niche that is intrinsically chemoresistant towards drugs targeted at tumour cells [34,35,36,37]. The main causes of death in these HCC patients are tumour progression, upper gastrointestinal bleeding or hepatic failure [38,39].
Even when HCC is detected in early stages, post-treatment recurrence is common and occurs in ~15% of patients treated with liver transplant [40,41,42], and ~60% of patients treated with partial resection with curative intent [43,44,45,46]. The median 5-year survival rate after recurrence is ~20%–35% [47,48,49,50]. Two types of recurrence have been reported: early recurrence, which occurs within 2 years of treatment and is assumed to arise from tumour cells not removed by liver resection or other treatments; and late recurrence, which generally occurs in a distant site from the primary tumour and is assumed to originate from an independent population of transformed hepatocytes [51,52]. Intrahepatic recurrence—as opposed to metastasis to extrahepatic tissues—occurs in the majority of cases, suggesting that the pro-oncogenic changes in the microenvironment of the resected liver play a major role in recurrence [53,54,55]. This hypothesis is supported by several reports showing that gene-signatures, including those centred about altered HCC-associated interferon (IFN)-γ and p53 signaling networks, in non-tumour tissue can be measured as an indicator for the probability of recurrence [56,57,58].

3.3. Histological and Molecular Changes

HCC has a highly variable histological appearance [59]. Identification of tumour cells is based on the presence of more than one of the following changes: high nuclear to cytoplasmic ratio; prominent nuclei and nucleoli; nuclear irregularity; moderate eosinophilia; and finely granular cytoplasm [60]. Additionally, normal, single cell-thick sinusoid structures are replaced with ≥2 cell-thick contorted cords. As HCC progresses, apparent dedifferentiation of the cells occurs from a hepatocyte-like morphology to a more stem-cell like phenotype [61,62]. For this reason, progression of HCC is associated with histological dedifferentiation from well-, moderately- to poorly-differentiated morphology. The extent of dedifferentiation of hepatocytes assessed by morphology correlates with poorer patient survival and increased rate of tumour recurrence [63,64,65]. HCC progression has also been associated with changes in subcellular organelles, such as significantly fewer and smaller mitochondria, and greater amounts of endoplasmic reticulum and free ribosomes [66,67,68]. Further, mitochondrial DNA mutations (though not consistently in any particular gene) have been detected in HCC [68,69,70]. These organelle changes may be due to metabolic alterations—such as increased autophagy or the Warburg effect—associated with carcinogenesis, but this has yet to be shown.
On a molecular level, HCC genomes commonly have alterations in the DNA genome, including DNA mutations in multiple oncogenes and tumour suppressor genes [71,72,73,74,75,76] and changes in chromosomal copy number, e.g., loss of 1q21.2 and gain of 17q13.1 [77,78], even in varying aetiologies [79,80,81]. Epigenetically, CpG methylation has been seen in the gene promoters of the JAK/STAT and other HCC-driving pathways, though these changes have also been seen in non-tumour tissue [82,83,84]. Additionally, alterations in histone-altering enzymes, such as histone deacetylases and histone methyltransferases, have been implicated in altering expression in HCC pathways though the mechanisms by which they achieve this is not entirely understood [85,86,87,88]. In this section, the most common and well-described changes associated with HCC are described briefly, though it should be noted that this list of altered pathways is not complete, and that these carcinogenic pathways are complex, interconnected, and, in some cases, still to be completely characterised. More detailed descriptions of these pathways are beyond the scope of this review and have been well summarised elsewhere (see relevant cited references).
One of the canonical molecular changes associated with HCC is the differential expression of the Wnt pathway, which regulates the expression of many proliferation, metabolism, and ECM remodeling-associated genes, such as c-myc, c-jun, glycogen synthase kinase-3β, cyclin D1 and matrix metalloproteinases (MMP) [72,89,90,91]. The Wnt pathway has been reported to be up-regulated in up to 90% of HCC tumours [75,76]. Wnt pathway genes may act in concert with the pathway associated with tumour suppressor gene p53, which has been observed to be commonly mutated in primary HCC tissue and animal injury models [92]. However, alteration of the Wnt or p53 pathway is not sufficient for HCC development, as the activation of these pathways via altered p53, adenomatous polyposis coli, or β-catenin gene expression has also been observed in benign liver neoplasms [93] and non-tumour tissue surrounding HCC tumours [94,95]. Additionally, alterations in the Wnt signaling pathway are significantly less common in HBV-associated HCC compared to other aetiologies, suggesting that further changes in the cell phenotype are necessary to produce HBV-associated HCC [76,96].
Another pathway altered in HCC is the Hedgehog (Hh) signaling pathway, which is up-regulated in up to 60% of HCC tumours [97]. Under normal conditions, the Hh pathway is involved in embryonic tissue development through regulation of a large range of downstream target genes [98]. In cancer, inhibition of the Hh pathway has been shown to decrease proliferation and increase apoptosis in HCC cell lines where Hh is regularly up-regulated [97,99,100]. Furthermore, studies from our group have shown a significant increase in intrahepatic levels of Hh mRNA in liver cirrhosis of different aetiologies compared to healthy control livers [101,102]. Similar to the Wnt signaling pathway, the Hh signaling pathway has been found to be up-regulated in a fraction of non-tumour tissue and is not seen in all HCC tumours [97], suggesting that it is also neither sufficient nor necessary for liver carcinogenesis.
Similar changes are seen in the JAK/STAT pathway with the activating phosphorylation of the key transcription factor STAT3 being reported in 50%–100% of HCC tumours and rarely in surrounding non-tumour tissue [103,104,105]. Activation of this pathway is associated with multiple cell functions, such as differentiation, proliferation, and apoptosis [106]. DNA mutations in genes of this pathway are rare, suggesting other regulatory mechanisms are involved, such as DNA promoter methylation or other epigenetic mechanisms [105]. The JAK/STAT pathway can also be activated by excess cytokine signaling via, for example, IL-6 [107,108], which reinforces the point that the liver microenvironment can directly stimulate the development of HCC and should be considered in HCC progression.
While there does not appear to be any single pathway that is sufficient or necessary for HCC development, these pathways commonly result in up-regulation of genes involved in cell cycle progression, proliferation and escape from apoptosis [109,110,111,112]. Not only does it allow for faster tumour growth and escape from some DNA proofreading mechanisms [113], overcoming cell cycle checkpoints is particularly important for HCC progression in the liver microenvironment where hepatocyte turnover is tightly regulated [114,115].
Table 1. Previously reported HCC subtypes and their associated clinical outcomes.
Table 1. Previously reported HCC subtypes and their associated clinical outcomes.
SubtypeClinical outcome associated with subtypeReferences
Hepatoblastoma-likeShorter time to post-resection HCC recurrence[19]
Poorer overall survival
Cholangiocarcinoma-likeShorter time to post-resection HCC recurrence[116]
Poorer overall survival
Cytokeratin-19 (CK19)-positiveShorter time to post-resection HCC recurrence[117]
Poorer overall survival
AFP-positiveIncreased HCC invasion[118,119]
Poorer overall survival
Notch-positiveNo correlation to clinical outcome[120]
Retinoblastoma-positiveBetter overall survival[121,122]
CD24-positiveShorter time to post-resection HCC recurrence[123]
Poorer overall survival
Transforming Growth Factor (TGF)-β late signature (compared to early signature)Increased HCC invasion[124]
Increased risk of HCC metastasis
Poorer overall survival
Myc TGF-α-positivePoorer overall survival[125]
Chromosome 7 gainShorter time to post-resection HCC recurrence [119]
Subtypes A and B based on chromosomal copy number alterationSubtype A is associated with poorer overall survival[126]
Despite this, it has been difficult to explain much of the heterogeneity observed in HCC tumours. Transcriptomic analysis has shown that changes in these common pathways occur late in the tumour development, while only modest transcriptomic changes are seen in early HCC and dysplastic nodules [127]. Even in late stage, intra-tumoural heterogeneity is observed in HCCs, leading to the classification of distinct HCC subtypes (Table 1). However, there is considerable variation even within each of these subtypes. It has been suggested that some of these subtypes arise from a difference in the cell of origin of a particular HCC. In particular, hepatoblastoma-like and cytokeratin-19 (CK-19) positive tumours are hypothesised to have originated from liver progenitor cells due to the similarity of their transcriptomic signatures [19,128,129,130,131]. However, novel data shows that the cells from which HCC originates do not necessarily determine the final phenotype of the tumour [16]. Thus, the cell of origin in HCC, whether from hepatic progenitor cells, dedifferentiated hepatocyte, extra-hepatic haematopoietic stem cells or a combination of some or all of these, is currently controversial. Due to the difficulty in determining the cell of origin, especially in primary clinical samples, this research is often hampered and so this controversy is not likely to be quelled soon.
In response to the heterogeneity displayed between and within the various HCC subtypes, large panels of genes have been used to define risk for HCC initiation, progression and recurrence, instead of single genes or pathways. For example, an mRNA expression panel of 186 genes has been found to be predictive of both HCC recurrence post-transplantation and of HCC initiation in HCV-infected patients with early cirrhosis [58,132], independent of other clinical features. One of the most successful panels for HCC progression includes a 5-gene panel, based on combined expression level of the genes HN1, RAN, RAMP3, KRT19 and TAF9, that has been shown to be highly predictive of survival time post-resection in HCC patients in multiple cohorts [133].

4. Microenvironmental Influence on HCC Pathogenesis

Research examining HCC has focussed on the histological and molecular changes associated with tumour propensity or behaviour. However, it is clear that the microenvironment within the liver should also be considered for both HCC initiation and progression. With regard to initiation, numerous studies and reviews have suggested that circulating cancer cells do not simply grow wherever they are seeded in the body, but their fate (e.g., quiescence or metastatic growth) is determined by the microenvironment of the seeded tissue, often referred to as the “seed and soil” hypothesis [134,135,136]. Additionally, the existence of the different subtypes of HCC [137] suggests that the initiation and progression of HCC may be shaped by various selective pressures, defined by the liver microenvironment.
In the following sections, we will review the roles of the various aspects of the liver microenvironment reported to drive HCC progression and tumour survival (Table 2). As shown schematically in Figure 1, the HCC tumour microenvironment is a highly-interconnected network. In this review, we will focus on particular nodes driven by the liver microenvironment: chronic inflammation, tissue remodeling, genetic alterations, and alterations in cellular signaling.
Table 2. Established and novel elements of the liver microenvironment and their roles in driving HCC progression [138,139,140,141,142,143,144,145,146,147,148,149,150,151,152,153,154,155,156,157,158,159,160,161,162,163,164].
Table 2. Established and novel elements of the liver microenvironment and their roles in driving HCC progression [138,139,140,141,142,143,144,145,146,147,148,149,150,151,152,153,154,155,156,157,158,159,160,161,162,163,164].
Microenvironmental elementMechanismsExample references
Immune cellsActivation of inflammatory cells leading to hepatocyte turnover, ROS formation[138]
Inhibition of immunosurveillance[139]
Regulatory T-cell (Treg) and tumour-associated macrophage (TAM) inhibition of cell-mediated cytotoxicity and immune responses against tumour cells[140,141,142]
Chemical carcinogens (e.g., Aflatoxin B1)DNA adduct formation, leading to chromosomal instability[143,144,145]
Direct induction of cell cycle entry[146]
Hepatitis B/C virusesInduction of chronic inflammation[147]
Induction of immune tolerance[148,149]
Formation of reactive oxygen/nitrogen species [150,151,152]
Alteration of DNA repair mechanisms via viral proteins[153]
Direct alteration of cellular pathways by viral proteins[154,155,156,157,158,159]
HypoxiaAlteration of macrophages to TAM-like phenotype, leading to immunosuppression and angiogenesis[141,160,161]
Induction of angiogenic cytokines by hepatocytes/tumour cells[162,163]
Altered stromal cells and ECM changesBuild-up of ECM (via altered ECM composition) leading to hypoxia[164]
Release of pro-tumourigenic cytokine TGF-β by altered stromal cells[21]
Impeding access of chemotherapies to tumour[34]
Diet and nutrition Unknown
GIT microfloraIncreasing permeability of gut to pro-inflammatory and pro-oncogenic bacterial metabolites (e.g., lipopolysaccharide and deoxycholic acid) responses[165,166]
Extracellular microvesicles Carry ECM-altering signals[167,168]
Carry oncogenic miRNAs and cytokines[169,170,171,172]
Induction of immunosuppression[173,174]

4.1. DNA Alterations in HCC

Several microenvironmental factors can directly induce the DNA alterations that are associated with the stepwise progression of HCC [143,144,145]. Chemical exposure and dietary ingestion of carcinogens are known to directly alter DNA sequences and cause DNA mutation [175,176,177]. For example, the chemical carcinogen 2-acetylaminofluorene (2-AAF) causes DNA adducts in mice [175]. AFB1, a mycotoxin present in a wide range of foods, is also a direct carcinogen that causes DNA adducts and mutations via DNA base conversion from G to T [177]. In particular, human exposure to AFB1 has been epidemiologically associated with mutations in the tumour suppressor gene p53 in HCC patients [176]. Further, mutations in p53 have been recapitulated in transgenic mouse fibroblasts by in vitro exposure to AFB1 [178]. This AFB1-associated DNA alteration can also become a feed-forward mechanism as AFB1 suppresses G1 checkpoint arrest by p53, bypassing the cellular DNA damage response, which leads to a greater mutation rate [179]. Additionally, the combination of AFB1 exposure and p53 mutation has been associated with chromosomal instability with HCC, further contributing to DNA alterations [180]. Further, the genetic diversity introduced by increased DNA mutations is postulated to decrease the effectiveness of chemotherapeutic agents, by increasing the likelihood that resistant tumour cells exist prior to chemotherapy [181,182]. Studies have also suggested that HCV gene products may directly interfere with cellular DNA repair mechanisms to induce DNA mutations [153].

4.2. Chronic Inflammation

Chronic inflammation is one of the main contributors to HCC initiation and progression. In virtually every case, chronic inflammation precedes the development of HCC [138]. The microenvironmental causes of chronic inflammation are diverse, including chronic HBV and HCV infection [147], and excessive ethanol consumption [147,183,184]. The immune-mediated cell death associated with chronic HBV and HCV infections can continuously trigger production of ROS, including hydrogen peroxide, hydroxyl radicals and superoxide radicals, by macrophages, neutrophils and cytotoxic T-lymphocytes [147]. The increased ROS results in increased hepatocellular oxidative stress, which can in turn induce DNA mutations that drive HCC [185,186,187,188]. HCV can directly increase intracellular ROS via expression of the HCV core protein and its inhibition of mitochondrial electron transport [148,149]. Ethanol consumption, a risk factor of HCC, is also known to increase the ROS concentration within hepatocytes, leading to increased formation of DNA adducts [147,183,184]. Additionally, reactive nitrogen species, such as nitrous oxide, are produced by hypoxic hepatocytes, the oxidative burst of infiltrating immune cells and endothelial cells responding to altered blood flow within the tumour or cirrhotic tissues [189].
These microenvironmental sources of chronic inflammation cause increased proliferation of hepatocytes, which leads to an increase in DNA mutations due to susceptibility for DNA damage during mitosis [190,191]. The subsequent proliferation of hepatocytes leads to a shortening of telomeres, which is in turn associated with chromosomal instability and progression to HCC [192]. The carcinogen diethylnitrosamine (DEN) induces proliferation of hepatocytes by up-regulating G1/S-phase regulatory proteins in mice [146] and can lead to HCC when given along with 2-AAF [193]. Another characteristic of chronic inflammation is tissue remodeling, which manifests as fibrosis and ultimately cirrhosis. In particular, chronic inflammation can alter cytokine expression within the injured liver, leading to an excess of ECM synthesis by hepatic stellate cells and resultant ECM accumulation [194,195,196]. The significance of tissue remodeling in the progression of HCC is described in further detail below.
Severe chronic inflammation can lead to the expansion of liver progenitor cell populations in the liver to replace hepatocytes [197]. As these are hypothesised to be the origin of at least a fraction of HCCs, proliferation of liver progenitor cells may increase the risk of HCC. Further, the cytokine milieu associated with chronic inflammation (e.g., elevated IL-6 levels) may drive liver progenitor cells to a more cancerous phenotype [198].
Chronic inflammation can also lead to tolerance or exhaustion of the cell-mediated immunity [139] which contributes towards the development and progression of HCC. The most obvious example of the importance of immune surveillance in HCC development is seen in liver transplantation where immunosuppression is used to prevent rejection. Post-transplant HCC recurrence is aggressive and early reduction in immunosuppression is used to minimize recurrence likelihood and/or severity [199,200]. Indeed, calcineurin inhibition of T-cell function to reduce organ rejection is thought to be one of the principal causes of the aggressiveness of HCC recurrence in the post-transplant setting [199,201]. Therefore, lymphocytes, in particular T-cells, are critically important in the immune surveillance and suppression of HCC. Tumour evasion of the immune response can also be facilitated by the intrinsic tolerogenic microenvironment of the liver [202,203], caused in part by Kupffer cells, the main population of macrophages resident in the liver [204,205,206]. Chronic virus infections, such as HBV and HCV, can also contribute to this tolerogenic effect and repression of cytotoxic T-cell response through secretion of viral antigens interacting with immune cells and altering signaling between the host cell and immune system [150,151,152]. Current evidence also suggests that HCC tumour cells can directly alter the liver microenvironment by recruiting regulatory T-cells (Treg) [207,208], or up-regulation of the programmed death-1 (PD-1) pathway [209,210,211], which have been associated with both poorer patient outcome and increased post-operative recurrence [208,212,213].

4.3. Tissue Remodeling and Stromal Interactions

Remodeling of the ECM in HCC involves the concerted action of multiple cell types in the liver microenvironment, including: (1) stromal cells, such as fibroblasts and hepatic stellate cells, which can lay down ECM components; (2) immune cells, such as macrophages, which can induce the ECM remodeling through activation of stromal cells or directly degrade ECM via the actions of MMPs; and (3) tumour cells, which can directly induce remodeling by stromal cells through altered signaling molecules/receptors (Figure 2). These microenvironmental factors can stimulate increased ECM accumulation by changing the balance between ECM degradation and ECM synthesis. As mentioned previously, chronic inflammation can stimulate hepatic stellate cell ECM synthesis and resultant ECM accumulation [194,195,196]. Also, the switch from hepatic stellate cell synthesis of collagen-IV in normal liver to the more proteolysis-resistant collagen types-I and -III also plays a role by slowing down ECM degradation [214,215]. Further, increased expression of tissue inhibitors of MMPs (TIMPs) is associated with ECM build-up [216]. Excess ECM is classified as fibrosis, and then progresses to cirrhosis once the excess fibrotic bands begin to enclose entire liver lobules. As cirrhosis is present in the majority (80%–90%) of patients with HCC [14], the characteristic excess of fibrotic ECM in cirrhosis suggests that abnormal ECM accumulation is also a key driver of HCC progression, though no direct causal link has been convincingly demonstrated.
Figure 2. A schematic diagram of interactions between the ECM and cells in the liver microenvironment.
Figure 2. A schematic diagram of interactions between the ECM and cells in the liver microenvironment.
Ijms 15 09422 g002
Altered blood flow and resultant hypoxia that occurs due to this ECM accumulation are stimulators of tumour progression. For example, tumour growth occurs rapidly following hepatocyte transformation, but is soon limited by the diffusion of oxygen and nutrients when the tumour reaches ~1 mm3 [217]. Tumour and non-tumour cells respond to hypoxic conditions by up-regulating angiogenic factors, such as vascular endothelial growth factor (VEGF) [162,163]. Hepatic stellate cells and liver endothelial cells respond to VEGF by stimulating vascular growth, which alleviates the limited supply of oxygen and nutrients to the tumour and thereby promotes tumour growth. Overexpression of VEGF by both tumour and surrounding non-tumour cells are responsible for the chaotic angiogenesis in tumours [218,219]. This uncoordinated angiogenesis is generally insufficient to relieve tumour-associated hypoxia, so areas of hypoxia still exist and this, in turn, leads to even greater angiogenesis. Altered hepatic blood flow can also reduce the amount of active therapeutic agents that can reach the HCC tumour, thus increasing its resistance to chemotherapy [34].
The pockets of hypoxia in the liver parenchyma during cirrhosis have also been proposed to be a driving mechanism of HCC [164]. Areas of hypoxia can lead to changes in molecular signaling in non-tumour cells that induce the progression of HCC. Macrophages are known to accumulate in hypoxic regions and their activation in hypoxic conditions induces a tumour-associated macrophage (TAM) phenotype [141,160,161]. This phenotype is associated with increased expression of tolerogenic molecules, such as PD-1 ligand and interleukin-10, and pro-angiogenic factors, such as angiopoietin 1, VEGF, and MMP-9 [140,141,142]. However, current reports conflict on whether increased intra-tumoural TAMs are associated with a favourable [220] or unfavourable [221] outcome in HCC patients.

4.4. Altered Hepatocyte Cell Signaling

Altered hepatocyte-stromal cell crosstalk in progressive fibrosis, consisting of alterations in tumour phenotype by ECM components or vice-versa, is also important in HCC pathogenesis [222,223]. For example, altered stromal cells have been reported to drive HCC development via direct signaling to the hepatocytes. Transfer of inflammation-induced myofibroblasts, i.e., fibrogenic cells derived from hepatic stellate cells, was shown to promote HCC in tumour suppressor gene p19ARF-knockout mice [21]. This promotion was suggested to occur through TGF-β secretion from the implanted stromal cells activating oncogenic pathways in the tumour cells.
Tumour-initiated alterations in ECM interactions have been associated with HCC progression and metastasis. Known pathways include down-regulation of cadherins (specifically E-cadherin), up-regulation of MMP activity and epithelial–mesenchymal transition (EMT) [224,225,226]. Alterations in all of these pathways are at least partly mediated by the expression of Extracellular Matrix Metalloproteinase Inducer EMMPRIN. EMMPRIN (also known as Tumour-derived Collagenase Stimulatory Factor or CD147) is a glycoprotein involved in MMP regulation at the tumour-stromal interface [227]. EMMPRIN expressed by leukocytes, tumour cells and TAMs induces contacting hepatic stellate cells [228,229] and hepatocytes [230] to increase expression of MMPs. Previous studies from our group have shown that intrahepatic EMMPRIN mRNA is increased in cirrhosis of different aetiologies [101,102]. Intra-tumoural EMMPRIN and resultant MMP activation in tissue from HCC patients has been associated with increased HCC vascularisation, invasion, EMT, metastasis and recurrence [231,232,233,234]. With regard to specific molecular mechanisms, up-regulation of tumour EMMPRIN expression has been shown to increase tumour vascularisation, potentially via: (1) tumour and hepatic stellate cell up-regulation of growth factors, such as VEGF or IGF-II; or (2) MMP activation in hepatic stellate cells [235,236,237,238]. The resultant extensive vascularisation is a risk factor for HCC metastasis [239,240]. Further, EMMPRIN-transfected hepatocyte cell lines have been shown to up-regulate autocrine signaling of the pro-tumourigenic cytokine TGF-β and increase the rate of HCC formation when injected into nude mice compared to non-transfected controls [241]. EMMPRIN expression has also been shown to decrease the apoptosis associated with loss of cell-contact (known as anoikis) in a range of cell lines, including HCC-derived cells [242,243,244]. This process could allow survival in the circulation, enabling them to seed in distant sites and evade liver resection, ultimately resulting in early HCC recurrence.
Alteration in the Hh pathway, one of the common changes seen in HCC, has been linked with tumour-stromal signaling and subsequent tumour progression. Hh expression from the primary tumour has been found to induce dense fibrous stroma formation in primary pancreatic cancer xenografts [245] and to break down bone stroma prior to breast cancer bone metastasis [246]. In the context of HCC, the Hh pathway has been shown to up-regulate glycolysis in surrounding myofibroblasts [247]. This induces increased production of free lactate, which adjacent HCC cells may take up and feed into fatty acid metabolism pathways to derive energy. Another effect of altered Hh pathway signaling is activation of hepatic stellate cells and hepatic progenitor cells in the liver, thereby driving the fibrogenic process [248,249].
Viral proteins expressed by HBV- and HCV-infected hepatocytes have also been shown to directly alter cellular signaling to drive HCC progression. For example, overexpression of either HBV surface [154,155] or HBV X [158,159] proteins in mouse models lead to liver lesions and HCC. Furthermore, the HCV core, NS3 and NS5a proteins have been reported to directly induce a wide range of cellular effects which drive carcinogenic processes, particularly the escape of cell-cycle checkpoints [156,157,250]. However, the real impact of direct carcinogenesis by viral proteins still remains difficult to quantify and characterise as the HCC models used are usually not physiological (overexpression of HBV surface and X proteins under non-native promoters) or are unavailable (no small animal HCV model exists).

5. Novel Microenvironmental Factors and Their Roles in Hepatocarcinogenesis

Recent research has implicated further aspects of the microenvironment, such as diet, GIT microflora [166,251] and microvesicles derived from cell subpopulations within the liver, in driving HCC initiation and progression. Though the exact causal mechanisms are yet to be established for these factors, these are areas of HCC research that we expect to be studied in greater detail in coming years.

5.1. Nutrition and Diet

In addition to the established promotion of HCC by dietary AFB1, other foods and nutrients may contribute to hepatocarcinogenesis, as the liver acts as both the initial solid organ seen by nutrients absorbed by the digestive tract and a storage site for glycogen and fats. Mouse and human studies have shown that dietary iron overload may directly induce hepatocarcinogenesis [252,253], which is consistent with the HCC risk that hereditary haemochromatosis confers to patients. High fat diet and associated metabolic diseases of obesity and Type II Diabetes Mellitus (T2D) are strongly linked to non-alcoholic liver disease (NAFLD) and non-alcoholic steatohepatitis (NASH), which have been shown to be associated with fibrosis, cirrhosis and HCC in epidemiological studies [254,255,256]. This link of HCC with metabolic diseases has been illustrated with DEN-induced HCC models in mice using both genetically-obese (leptin-deficient) mice and wild-type mice fed a high-fat diet [257,258]. In both models, increased rates and size of HCC were observed. Further, obesity has been shown to be associated with earlier HCC recurrence in patients treated with liver transplantation [259]. HCC risk appears to be affected not only by the level of caloric intake, but also the composition of diet. Large population-based studies have associated reduced HCC rates with increased adherence to the “Mediterranean diet”, to increased consumption of fish, eggs, dairy, and fruits, and increased caffeine intake [260,261,262,263,264]. Together these studies suggest that diet and physical exercise to lower body mass index may protect against HCC, though we have found no reports directly testing this hypothesis.
Detailed studies investigating the specific mechanisms behind these dietary associations with HCC have been sparse to date. A potential contributor to the unclear role of dietary factors in HCC is their complicated interrelation with other known drivers of HCC [265]. For example, a synergistic increase in serum liver transaminases (a marker for liver damage) was seen in mice fed both dietary iron and ethanol [266]. Further, there is a complex relationship between hepatic steatosis, HCV (described earlier as a strong causative factor for hepatocarcinogenesis) and HCC. Patients with HCV have significantly higher rates of hepatic steatosis and fibrosis severity, compared to HBV-positive patients and healthy controls [267]. Further, HCV-positive patients with concurrent T2D were demonstrated to have a 2–3 fold increased risk of developing HCC compared to those patients without T2D [268]. This clearly indicates T2D as a risk factor for HCC; however a multivariate analysis that took other known microenvironment drivers of HCC into account found only a weak association of dietary factors to HCC progression [262,269,270]. Thus, the specific molecular roles of dietary factors in HCC development are poorly understood and are likely to be the subject to future investigations, especially with the increased worldwide incidence of metabolic diseases.

5.2. GIT Microflora

A high-fat diet is also associated with alterations of the resident microflora in the gastrointestinal tract [165,271,272]. It is possible that altered GIT microflora can drive HCC progression via the alteration of hepatic inflammation either by increasing the permeability of the GIT mucosa and allowing inflammatory products, such as bacterial lipopolysaccharide (LPS) or deoxycholic acid (DCA), to enter the portal circulation [165,273,274]. The promotional effect of altered gut flora on development of 7,12-dimethylbenz(a)anthracene-induced HCC in obese mice has been shown to be dependent on DCA and its alteration of hepatic stellate cell gene expression [165]. This HCC-promoting effect was not via a profibrotic hepatic stellate cell response but due to a senescence secretory response, mediated by interleukin-1β. In other studies, the growth of specific species in GIT microflora, in particular Helicobacter species, have been shown to promote HCC initiation and progression in mouse models of chemical and viral carcinogenesis through chronic inflammation [166,251]. Zhang et al. showed that alteration of gut homeostasis with penicillin significantly increased serum LPS levels, circulating pro-inflammatory cytokine interleukin-6, and both cirrhotic and HCC progression in a DEN-induced HCC rat model [166]. Similar changes were seen when the rats were treated with oral dextran sulfate sodium to increase gut permeability. Further, in this study, gut permeability could be normalised (with concomitant decrease in HCC progression) by the administration of probiotics, suggesting that clinical intervention in human patients may be possible.
Limited human studies have reported an association between altered GIT microflora, particularly the appearance of Helicobacter species, with the progression of HCC and cirrhosis [275,276,277,278]. Indeed, Helicobacter bacteria have been found not only in the GIT, but also in the liver itself during HCC formation, though it is not clear whether this drives HCC progression or is an artefact of late-stage liver disease [275,276,277,278]. There have also been studies showing increased inflammatory bacterial metabolites LPS and DCA in patients with liver cirrhosis and HCC [165,166]. However, follow-up studies are required to determine specific causal relationships between HCC and GIT microflora and whether clinical interventions to alter GIT microflora can improve patient outcomes [279].

5.3. Microvesicles (Microparticles and Exosomes)

Microvesicles, including microparticles (formed by cell membrane shedding) and exosomes (formed by release of intracellular multivesicular bodies), are small, enveloped blebs that are secreted by many organs [280]. Microvesicles as carriers of cellular signals have been implicated in hepatocarcinogenesis, though the specific mechanism(s) involved are still unknown. A growing body of literature already describes the myriad of roles of microvesicles and their biological functions particularly in liver disease, ranging from systemic or intercellular communications to eliciting immunological responses [171,172].
In the context of cancer, tumour-derived microvesicles may have both anti-tumourigenic and pro-tumourigenic roles [281]. Exosomes released by cancer cells have been observed to contain tumour antigens, leading to the hypothesis that anti-cancer vaccines could be developed from these tumour-derived exosomes. Several phase I clinical trials have used tumour-derived exosomes or exosome-pulsed dendritic cells as cancer vaccines [282,283]. In addition to their immunostimulatory effects, these exosomes may also be involved in tumour cell apoptosis via decreased B-cell lymphoma 2 protein (Bcl-2) and increased Bcl-2-associated X protein (Bax) expression [284]. Specifically in HCC, heat-shock-protein (HSP)-bearing exosomes are released from human HCC cell lines upon stimulation with chemotherapeutic agents, and these exosomes can elicit natural killer cell anti-tumour responses [285].
The pro-tumourigenic functions of microvesicles include immunosuppressive effects via Treg cells and inhibition of differentiation of bone marrow dendritic cells [169,170]. Further, exosomes can facilitate tumour-invasion and metastasis by up-regulation of tetraspanins (a class of phospholipid membrane molecules known to promote angiogenesis) [286,287], and can transport mRNA, microRNAs and proteins essential for tumour survival and growth [173,174]. Interestingly, microvesicles from tumour cells [167] (including HCC cell lines [288]) and circulating T-cells [168] are known to contain EMMPRIN and stimulate breakdown of ECM by hepatic stellate cells and fibroblasts.
In HCC, the effects of exosome-transported mRNAs and miRNAs have not been completely elucidated. Microvesicles released from human liver stem cells have been shown to inhibit HCC growth in SCID mice [289]. This effect was reportedly due to delivery of miRNAs (miR451, miR223, miR24, miR31, miR214 and miR122), which conferred direct anti-tumour activity via down-regulation of MDR1, MIF, RAB14 and E2F-2. TGF-β activated kinase-1 (TAK1) has also been identified as a potential pathway modified by miRNA carried by microvesicles [290], as loss of TAK1 has been implicated in hepatocarcinogenesis and is a plausible target for intercellular modulation. We are unaware of any studies to date showing that HCC-specific microvesicles in the liver microenvironment alter the phenotype of surrounding non-tumour hepatocytes, though this is a potential, even likely, route of cell-cell signaling.
It is increasingly apparent that microvesicles are intricately linked to various factors in the tumour microenvironment that may promote local spread, intrahepatic metastases, and possibly multifocal growth of HCC. Although the molecular pathophysiological mechanisms are not entirely understood at present, the microvesicular cargo and membrane proteins may be pivotal in intercellular communication and modification of tumour behaviour.

6. Targeting the Microenvironment to Prevent and Treat HCC

By characterising the effect of microenvironmental factors on HCC initiation and development further, we may be able to target HCC in multiple ways to synergistically decrease development and spread of the tumour. Indeed, existing measures against microenvironmental factors have been used to prevent and treat HCC.
The most successful HCC prevention measure to date has been vaccination against HBV. Vaccination in highly endemic areas, such as Taiwan, has led to a large drop in HCC cases [20,291,292]. Since HBV/HCV infection is a risk factor for HCC recurrence after resection [293,294], several groups have studied the rate of HCC recurrence after antiviral treatment [295]. The general consensus is that antiviral treatment significantly decreases HBV/HCV-associated HCC recurrence. However, the specific anti-viral therapy agent(s), dose, timing, and routes all require further optimisation [296,297,298]. In HCV infection, treating active virus infection and achieving a sustained virological response (SVR) is associated with a 75% reduction in HCC risk despite the persistence of cirrhosis. Therefore, the grade of hepatitis activity is a risk factor for HCC recurrence and the main mechanism of antiviral treatment may be freeing the liver microenvironment from drivers of chronic inflammation, and thereby preventing recurrent HCC. Cofactors in HCC progression, including obesity and diabetes, alcohol, iron overload and viral co-infections, are clearly important and may increase risk of HCC through further promotion of inflammation as well as having other unrecognised effects on carcinogenesis. A highly relevant and important example is the increased risk of HCC with increasing HBV DNA levels [293,294,295,296,297,298,299,300], which is associated with greater inflammation. Other factors, such as the serum level of HBV surface antigen, genotype of the virus and expression of HBV e-antigen, all add to the risk for the occurrence of HCC [301,302,303].
HCC progression can potentially be limited by normalising the liver microenvironment using other strategies. For example, treatment with angiogenic agents may normalise existing aberrant vascularisation in the tumour and therefore to limit hypoxic regions [218]. Reducing the number of hypoxic cells may limit tumour progression by improving access of chemotherapies and by decreasing the expression of hypoxia-induced genes in tumour subpopulations that promote metastasis [304]. Several pro-drugs that are converted into cytotoxic agents by low intracellular oxygen levels have been designed and tested up to phase II and phase III trials, with varying levels of success [305]. Also, in addition to being an inhibitor of HCC growth, Sorafenib acts as an anti-fibrotic agent in early stages of fibrosis in mouse models [306]. These agents may limit the formation of hypoxic regions and thus block some pro-oncogenic pathways in the liver. Furthermore, altering the expression or activity of molecules known to be associated with cancer progression may have utility. For example, blocking EMMPRIN signaling using antibodies has been shown to reduce invasion in cell lines, reduce tumour size in experimental HCC mouse models and decrease fibrosis in CCl4-treated mice [228,307]. Further, radiolabelled anti-EMMPRIN antibodies have been shown to be well-tolerated and decrease tumour recurrence in HCC patients, however the mechanism, whether due to blocking EMMPRIN function, enhancing delivery of radio-therapeutics or both, is unclear [308,309].
Attempts have been made to stimulate the poor tumour-specific cytotoxic immune responses present in HCC patients [310,311]. Some studies have used either HCC lysates or specific HCC antigens, such as AFP, as vaccines or as antigens to be loaded onto dendritic cells ex vivo to be reintroduced into the host. While successful in mice [312], early trials conducted on patients with late-stage HCC have shown that tumour-specific immune responses can be raised with these approaches, but with little improvement in clinical outcomes [313,314]. Also, post-resection HCC recurrence was measured in in HCC patients after isolation of circulating lymphocytes and reperfusion following their activation with interleukin-2 and anti-CD3 antibodies [315]. The treated patients had extended recurrence-free time intervals and a reduced risk of recurrence, but overall survival was not significantly different from non-treated controls. Local tolerogenic factors in the tumour may be contributors to the poor clinical outcomes seen in these trials and may have to be modulated to optimise response. For example, Greten et al. depleted Treg in HCC patients by treatment with cyclophosphamide, resulting in an increase in HCC-specific T-cell responses [316].

7. Conclusions

In summary, HCC arises not simply due to a hepatocyte containing sufficient genetic mutations, but also develops due to its context in the liver microenvironment. A multitude of inter-related factors in the liver microenvironment affect the progression of HCC, with some these mechanisms still to be fully described. Characterisation of the mechanisms of these novel factors has driven the pursuit toward new therapies that treat not only the tumour itself, but also the liver microenvironment to prevent the recurrence and treatment resistance associated with HCC.

Acknowledgments

T.T. and M.B. were funded by Sydney Foundation for Medical Research (Grant number 53030). The authors wish to thank Miriam Kleinig for her critical editing of the manuscript.

Conflicts of Interest

The authors declare no conflict of interest.

References

  1. Jemal, A.; Bray, F.; Center, M.M.; Ferlay, J.; Ward, E.; Forman, D. Global cancer statistics. CA: Cancer J. Clin. 2011, 61, 69–90. [Google Scholar] [CrossRef]
  2. Parkin, D.M.; Pisani, P.; Ferlay, J. Estimates of the worldwide incidence of 25 major cancers in 1990. Int. J. Cancer 1999, 80, 827–841. [Google Scholar] [CrossRef]
  3. Bosch, F.X.; Ribes, J.; Diaz, M.; Cleries, R. Primary liver cancer: Worldwide incidence and trends. Gastroenterology 2004, 127, S5–S16. [Google Scholar] [CrossRef]
  4. Montalto, G.; Cervello, M.; Giannitrapani, L.; Dantona, F.; Terranova, A.; Castagnetta, L.A. Epidemiology, risk factors, and natural history of hepatocellular carcinoma. Ann. N. Y. Acad. Sci. 2002, 963, 13–20. [Google Scholar]
  5. Michielsen, P.P.; Francque, S.M.; van Dongen, J.L. Viral hepatitis and hepatocellular carcinoma. World J. Surg. Oncol. 2005, 3, 27. [Google Scholar] [CrossRef] [Green Version]
  6. Parkin, D.M.; Bray, F.; Ferlay, J.; Pisani, P. Global cancer statistics, 2002. CA: A Cancer J. Clin. 2005, 55, 74–108. [Google Scholar] [CrossRef]
  7. Lee, J.G.; Kang, C.M.; Park, J.S.; Kim, K.S.; Yoon, D.S.; Choi, J.S.; Lee, W.J.; Kim, B.R. The actual five-year survival rate of hepatocellular carcinoma patients after curative resection. Yonsei Med. J. 2006, 47, 105–112. [Google Scholar] [CrossRef]
  8. Altekruse, S.F.; McGlynn, K.A.; Reichman, M.E. Hepatocellular carcinoma incidence, mortality, and survival trends in the United States from 1975 to 2005. J. Clin. Oncol. 2009, 27, 1485–1491. [Google Scholar] [CrossRef]
  9. Lu, S.N.; Su, W.W.; Yang, S.S.; Chang, T.T.; Cheng, K.S.; Wu, J.C.; Lin, H.H.; Wu, S.S.; Lee, C.M.; Changchien, C.S.; et al. Secular trends and geographic variations of hepatitis B virus and hepatitis C virus-associated hepatocellular carcinoma in Taiwan. Int. J. Cancer 2006, 119, 1946–1952. [Google Scholar] [CrossRef]
  10. Wong, P.Y.; Xia, V.; Imagawa, D.K.; Hoefs, J.; Hu, K.Q. Clinical presentation of hepatocellular carcinoma (HCC) in Asian-Americans versus non-Asian-Americans. J. Immigr. Minor. Health 2011, 13, 842–848. [Google Scholar] [CrossRef]
  11. Kumar, R.; Saraswat, M.K.; Sharma, B.C.; Sakhuja, P.; Sarin, S.K. Characteristics of hepatocellular carcinoma in India: A retrospective analysis of 191 cases. Mon. J. Assoc. Phys. (QJM) 2008, 101, 479–485. [Google Scholar]
  12. Omer, R.E.; Kuijsten, A.; Kadaru, A.M.; Kok, F.J.; Idris, M.O.; el Khidir, I.M.; van ’t Veer, P. Population-attributable risk of dietary aflatoxins and hepatitis B virus infection with respect to hepatocellular carcinoma. Nutr. Cancer 2004, 48, 15–21. [Google Scholar] [CrossRef]
  13. Yeh, F.S.; Yu, M.C.; Mo, C.C.; Luo, S.; Tong, M.J.; Henderson, B.E. Hepatitis B virus, aflatoxins, and hepatocellular carcinoma in southern Guangxi, China. Cancer Res. 1989, 49, 2506–2509. [Google Scholar]
  14. Fattovich, G.; Stroffolini, T.; Zagni, I.; Donato, F. Hepatocellular carcinoma in cirrhosis: Incidence and risk factors. Gastroenterology 2004, 127, S35–S50. [Google Scholar] [CrossRef]
  15. Chen, Y.; Yu, D.; Zhang, H.; He, H.; Zhang, C.; Zhao, W.; Shao, R.G. CD133(+)EpCAM(+) phenotype possesses more characteristics of tumor initiating cells in hepatocellular carcinoma Huh7 cells. Int. J. Biol. Sci. 2012, 8, 992–1004. [Google Scholar] [CrossRef]
  16. Zucman-Rossi, J.; Nault, J.C.; Zender, L. Primary liver carcinomas can originate from different cell types: A new level of complexity in hepatocarcinogenesis. Gastroenterology 2013, 145, 53–55. [Google Scholar] [CrossRef]
  17. Roskams, T.; Desmet, V.J.; Verslype, C. Development, structure and function of the liver. In MacSween’s Pathology of the Liver, 5th ed.; Burt, A.D., Portmann, B.C., Ferrell, L.D., Eds.; Churchill Livingstone Elsevier: Philidelphia, PA, USA, 2007; Volume 1, pp. 1–74. [Google Scholar]
  18. Grisham, J.W. Cell types in rat liver cultures: Their identification and isolation. Mol. Cell. Biochem. 1983, 53–54, 23–33. [Google Scholar]
  19. Lee, J.S.; Heo, J.; Libbrecht, L.; Chu, I.S.; Kaposi-Novak, P.; Calvisi, D.F.; Mikaelyan, A.; Roberts, L.R.; Demetris, A.J.; Sun, Z.; et al. A novel prognostic subtype of human hepatocellular carcinoma derived from hepatic progenitor cells. Nat. Med. 2006, 12, 410–416. [Google Scholar] [CrossRef]
  20. Beasley, R.P. Hepatitis B virus. The major etiology of hepatocellular carcinoma. Cancer 1988, 61, 1942–1956. [Google Scholar] [CrossRef]
  21. Van Zijl, F.; Mair, M.; Csiszar, A.; Schneller, D.; Zulehner, G.; Huber, H.; Eferl, R.; Beug, H.; Dolznig, H.; Mikulits, W. Hepatic tumor-stroma crosstalk guides epithelial to mesenchymal transition at the tumor edge. Oncogene 2009, 28, 4022–4033. [Google Scholar] [CrossRef]
  22. Hernandez-Gea, V.; Toffanin, S.; Friedman, S.L.; Llovet, J.M. Role of the microenvironment in the pathogenesis and treatment of hepatocellular carcinoma. Gastroenterology 2013, 144, 512–527. [Google Scholar] [CrossRef]
  23. Qin, L.X. Inflammatory immune responses in tumor microenvironment and metastasis of hepatocellular carcinoma. Cancer Microenviron. 2012, 5, 203–209. [Google Scholar] [CrossRef]
  24. Leonardi, G.C.; Candido, S.; Cervello, M.; Nicolosi, D.; Raiti, F.; Travali, S.; Spandidos, D.A.; Libra, M. The tumor microenvironment in hepatocellular carcinoma (review). Int. J. Oncol. 2012, 40, 1733–1747. [Google Scholar]
  25. Forner, A.; Llovet, J.M.; Bruix, J. Hepatocellular carcinoma. Lancet 2012, 379, 1245–1255. [Google Scholar] [CrossRef]
  26. El-Serag, H.B.; Marrero, J.A.; Rudolph, L.; Reddy, K.R. Diagnosis and treatment of hepatocellular carcinoma. Gastroenterology 2008, 134, 1752–1763. [Google Scholar] [CrossRef]
  27. Llovet, J.M.; Burroughs, A.; Bruix, J. Hepatocellular carcinoma. Lancet 2003, 362, 1907–1917. [Google Scholar] [CrossRef]
  28. Lim, K.C.; Chow, P.K.; Allen, J.C.; Siddiqui, F.J.; Chan, E.S.; Tan, S.B. Systematic review of outcomes of liver resection for early hepatocellular carcinoma within the Milan criteria. Br. J. Surg. 2012, 99, 1622–1629. [Google Scholar] [CrossRef]
  29. Morris-Stiff, G.; Gomez, D.; de Liguori Carino, N.; Prasad, K.R. Surgical management of hepatocellular carcinoma: Is the jury still out? Surg. Oncol. 2009, 18, 298–321. [Google Scholar] [CrossRef]
  30. Schoniger-Hekele, M.; Muller, C.; Kutilek, M.; Oesterreicher, C.; Ferenci, P.; Gangl, A. Hepatocellular carcinoma in Austria: Aetiological and clinical characteristics at presentation. Eur. J. Gastroenterol. Hepatol. 2000, 12, 941–948. [Google Scholar] [CrossRef]
  31. Bruix, J.; Sherman, M. Management of hepatocellular carcinoma: An update. Hepatology 2011, 53, 1020–1022. [Google Scholar] [CrossRef]
  32. Mahnken, A.H.; Bruners, P.; Gunther, R.W. Local ablative therapies in HCC: Percutaneous ethanol injection and radiofrequency ablation. Dig. Dis. 2009, 27, 148–156. [Google Scholar] [CrossRef]
  33. Minami, Y.; Kudo, M. Radiofrequency ablation of hepatocellular carcinoma: A literature review. Int. J. Hepatol. 2011, 2011, 104685. [Google Scholar]
  34. Hammer, S.; To, K.K.; Yoo, Y.G.; Koshiji, M.; Huang, L.E. Hypoxic suppression of the cell cycle gene CDC25A in tumor cells. Cell Cycle 2007, 6, 1919–1926. [Google Scholar] [CrossRef]
  35. Jiao, M.; Nan, K.J. Activation of PI3 kinase/Akt/HIF-1alpha pathway contributes to hypoxia-induced epithelial-mesenchymal transition and chemoresistance in hepatocellular carcinoma. Int. J. Oncol. 2012, 40, 461–468. [Google Scholar]
  36. Noda, T.; Nagano, H.; Takemasa, I.; Yoshioka, S.; Murakami, M.; Wada, H.; Kobayashi, S.; Marubashi, S.; Takeda, Y.; Dono, K.; et al. Activation of Wnt/beta-catenin signalling pathway induces chemoresistance to interferon-alpha/5-fluorouracil combination therapy for hepatocellular carcinoma. Br. J. Cancer 2009, 100, 1647–1658. [Google Scholar] [CrossRef]
  37. Wang, X.Q.; Ongkeko, W.M.; Chen, L.; Yang, Z.F.; Lu, P.; Chen, K.K.; Lopez, J.P.; Poon, R.T.; Fan, S.T. Octamer 4 (Oct4) mediates chemotherapeutic drug resistance in liver cancer cells through a potential Oct4-AKT-ATP-binding cassette G2 pathway. Hepatology 2010, 52, 528–539. [Google Scholar] [CrossRef]
  38. Yeung, Y.P.; Lo, C.M.; Liu, C.L.; Wong, B.C.; Fan, S.T.; Wong, J. Natural history of untreated nonsurgical hepatocellular carcinoma. Am. J. Gastroenterol. 2005, 100, 1995–2004. [Google Scholar] [CrossRef]
  39. Llovet, J.M.; Bustamante, J.; Castells, A.; Vilana, R.; Ayuso Mdel, C.; Sala, M.; Bru, C.; Rodes, J.; Bruix, J. Natural history of untreated nonsurgical hepatocellular carcinoma: Rationale for the design and evaluation of therapeutic trials. Hepatology 1999, 29, 62–67. [Google Scholar] [CrossRef]
  40. Escartin, A.; Sapisochin, G.; Bilbao, I.; Vilallonga, R.; Bueno, J.; Castells, L.; Dopazo, C.; Castro, E.; Caralt, M.; Balsells, J. Recurrence of hepatocellular carcinoma after liver transplantation. Transplant. Proc. 2007, 39, 2308–2310. [Google Scholar] [CrossRef]
  41. Saab, S.; Yeganeh, M.; Nguyen, K.; Durazo, F.; Han, S.; Yersiz, H.; Farmer, D.G.; Goldstein, L.I.; Tong, M.J.; Busuttil, R.W. Recurrence of hepatocellular carcinoma and hepatitis B reinfection in hepatitis B surface antigen-positive patients after liver transplantation. Liver Transplant. 2009, 15, 1525–1534. [Google Scholar] [CrossRef]
  42. Kim, Y.S.; Lim, H.K.; Rhim, H.; Lee, W.J.; Joh, J.W.; Park, C.K. Recurrence of hepatocellular carcinoma after liver transplantation: Patterns and prognostic factors based on clinical and radiologic features. Am. J. Roentgenol. 2007, 189, 352–358. [Google Scholar] [CrossRef]
  43. Chen, M.F.; Hwang, T.L.; Jeng, L.B.; Wang, C.S.; Jan, Y.Y.; Chen, S.C. Postoperative recurrence of hepatocellular carcinoma. Two hundred five consecutive patients who underwent hepatic resection in 15 years. Arch. Surg. 1994, 129, 738–742. [Google Scholar] [CrossRef]
  44. Belghiti, J.; Panis, Y.; Farges, O.; Benhamou, J.P.; Fekete, F. Intrahepatic recurrence after resection of hepatocellular carcinoma complicating cirrhosis. Ann. Surg. 1991, 214, 114–117. [Google Scholar] [CrossRef]
  45. Lise, M.; Bacchetti, S.; Da Pian, P.; Nitti, D.; Pilati, P.L.; Pigato, P. Prognostic factors affecting long term outcome after liver resection for hepatocellular carcinoma: Results in a series of 100 Italian patients. Cancer 1998, 82, 1028–1036. [Google Scholar] [CrossRef]
  46. Shah, S.A.; Cleary, S.P.; Wei, A.C.; Yang, I.; Taylor, B.R.; Hemming, A.W.; Langer, B.; Grant, D.R.; Greig, P.D.; Gallinger, S. Recurrence after liver resection for hepatocellular carcinoma: Risk factors, treatment, and outcomes. Surgery 2007, 141, 330–339. [Google Scholar] [CrossRef]
  47. Roayaie, S.; Schwartz, J.D.; Sung, M.W.; Emre, S.H.; Miller, C.M.; Gondolesi, G.E.; Krieger, N.R.; Schwartz, M.E. Recurrence of hepatocellular carcinoma after liver transplant: Patterns and prognosis. Liver Transplant. 2004, 10, 534–540. [Google Scholar] [CrossRef]
  48. Chen, W.T.; Chau, G.Y.; Lui, W.Y.; Tsay, S.H.; King, K.L.; Loong, C.C.; Wu, C.W. Recurrent hepatocellular carcinoma after hepatic resection: prognostic factors and long-term outcome. Eur. J. Surg. Oncol. 2004, 30, 414–420. [Google Scholar]
  49. Poon, R.T.; Fan, S.T.; Lo, C.M.; Liu, C.L.; Wong, J. Long-term survival and pattern of recurrence after resection of small hepatocellular carcinoma in patients with preserved liver function: Implications for a strategy of salvage transplantation. Ann. Surg. 2002, 235, 373–382. [Google Scholar] [CrossRef]
  50. Chan, A.C.; Poon, R.T.; Cheung, T.T.; Chok, K.S.; Chan, S.C.; Fan, S.T.; Lo, C.M. Survival analysis of re-resection versus radiofrequency ablation for intrahepatic recurrence after hepatectomy for hepatocellular carcinoma. World J. Surg. 2012, 36, 151–156. [Google Scholar] [CrossRef]
  51. Poon, R.T. Differentiating early and late recurrences after resection of HCC in cirrhotic patients: Implications on surveillance, prevention, and treatment strategies. Ann. Surg. Oncol. 2009, 16, 792–794. [Google Scholar] [CrossRef] [Green Version]
  52. Portolani, N.; Coniglio, A.; Ghidoni, S.; Giovanelli, M.; Benetti, A.; Tiberio, G.A.; Giulini, S.M. Early and late recurrence after liver resection for hepatocellular carcinoma: Prognostic and therapeutic implications. Ann. Surg. 2006, 243, 229–235. [Google Scholar] [CrossRef]
  53. Cha, C.; Fong, Y.; Jarnagin, W.R.; Blumgart, L.H.; DeMatteo, R.P. Predictors and patterns of recurrence after resection of hepatocellular carcinoma. J. Am. Coll. Surg. 2003, 197, 753–758. [Google Scholar] [CrossRef]
  54. Lee, P.H.; Lin, W.J.; Tsang, Y.M.; Hu, R.H.; Sheu, J.C.; Lai, M.Y.; Hsu, H.C.; May, W.; Lee, C.S. Clinical management of recurrent hepatocellular carcinoma. Ann. Surg. 1995, 222, 670–676. [Google Scholar] [CrossRef]
  55. Kanematsu, T.; Matsumata, T.; Takenaka, K.; Yoshida, Y.; Higashi, H.; Sugimachi, K. Clinical management of recurrent hepatocellular carcinoma after primary resection. Br. J. Surg. 1988, 75, 203–206. [Google Scholar] [CrossRef]
  56. Utsunomiya, T.; Shimada, M.; Imura, S.; Morine, Y.; Ikemoto, T.; Mori, M. Molecular signatures of noncancerous liver tissue can predict the risk for late recurrence of hepatocellular carcinoma. J. Gastroenterol. 2010, 45, 146–152. [Google Scholar] [CrossRef]
  57. Tsuchiya, M.; Parker, J.S.; Kono, H.; Matsuda, M.; Fujii, H.; Rusyn, I. Gene expression in nontumoral liver tissue and recurrence-free survival in hepatitis C virus-positive hepatocellular carcinoma. Mol. Cancer 2010, 9, 74. [Google Scholar] [CrossRef]
  58. Hoshida, Y.; Villanueva, A.; Kobayashi, M.; Peix, J.; Chiang, D.Y.; Camargo, A.; Gupta, S.; Moore, J.; Wrobel, M.J.; Lerner, J.; et al. Gene expression in fixed tissues and outcome in hepatocellular carcinoma. N. Engl. J. Med. 2008, 359, 1995–2004. [Google Scholar] [CrossRef]
  59. Ishak, K.; Anthony, P.P.; Sobin, L.H. Histological Typing of Tumours of the Liver, 2nd ed.; Springer-Verlag: Berlin, Germany, 1994; Volume 1, pp. 5–7. [Google Scholar]
  60. Goodman, Z.D.; Terracciano, L. Tumours and tumour-like lesions of the liver. In MacSween’s Pathology of the Liver, 5th ed.; Burt, A.D., Portmann, B.C., Ferrell, L.D., Eds.; Churchill Livingstone Elsevier: Philidelphia, PA, USA, 2007; Volume 1, pp. 761–814. [Google Scholar]
  61. Edmondson, H.A.; Steiner, P.E. Primary carcinoma of the liver: A study of 100 cases among 48,900 necropsies. Cancer 1954, 7, 462–503. [Google Scholar] [CrossRef]
  62. Sugihara, S.; Nakashima, O.; Kojiro, M.; Majima, Y.; Tanaka, M.; Tanikawa, K. The morphologic transition in hepatocellular carcinoma. A comparison of the individual histologic features disclosed by ultrasound-guided fine-needle biopsy with those of autopsy. Cancer 1992, 70, 1488–1492. [Google Scholar] [CrossRef]
  63. Esnaola, N.F.; Lauwers, G.Y.; Mirza, N.Q.; Nagorney, D.M.; Doherty, D.; Ikai, I.; Yamaoka, Y.; Regimbeau, J.M.; Belghiti, J.; Curley, S.A.; et al. Predictors of microvascular invasion in patients with hepatocellular carcinoma who are candidates for orthotopic liver transplantation. J. Gastrointest. Surg. 2002, 6, 224–232, Discussion 232. [Google Scholar] [CrossRef]
  64. Klintmalm, G.B. Liver transplantation for hepatocellular carcinoma: A registry report of the impact of tumor characteristics on outcome. Ann. Surg. 1998, 228, 479–490. [Google Scholar] [CrossRef]
  65. Tamura, S.; Kato, T.; Berho, M.; Misiakos, E.P.; O’Brien, C.; Reddy, K.R.; Nery, J.R.; Burke, G.W.; Schiff, E.R.; Miller, J.; et al. Impact of histological grade of hepatocellular carcinoma on the outcome of liver transplantation. Arch. Surg. 2001, 136, 25–30, Discussion 31. [Google Scholar] [CrossRef]
  66. Kinoyama, S.; Yamada, G.; Nagashima, H. Ultrastructural observation of alpha-fetoprotein producing cells in human hepatocellular carcinoma using immunoperoxidase methods—Comparison with fetal liver. Gastroenterol. Jpn. 1986, 21, 152–161. [Google Scholar]
  67. Sugihara, S.; Kojiro, M.; Nakashima, T. Ultrastructural study of hepatocellular carcinoma with replacing growth pattern. Acta Pathol. Jpn. 1985, 35, 549–559. [Google Scholar]
  68. Yin, P.H.; Lee, H.C.; Chau, G.Y.; Wu, Y.T.; Li, S.H.; Lui, W.Y.; Wei, Y.H.; Liu, T.Y.; Chi, C.W. Alteration of the copy number and deletion of mitochondrial DNA in human hepatocellular carcinoma. Br. J. Cancer 2004, 90, 2390–2396. [Google Scholar]
  69. Hsu, C.C.; Lee, H.C.; Wei, Y.H. Mitochondrial DNA alterations and mitochondrial dysfunction in the progression of hepatocellular carcinoma. World J. Gastroenterol. 2013, 19, 8880–8886. [Google Scholar] [CrossRef]
  70. Okochi, O.; Hibi, K.; Uemura, T.; Inoue, S.; Takeda, S.; Kaneko, T.; Nakao, A. Detection of mitochondrial DNA alterations in the serum of hepatocellular carcinoma patients. Clin. Cancer Res. 2002, 8, 2875–2878. [Google Scholar]
  71. Azechi, H.; Nishida, N.; Fukuda, Y.; Nishimura, T.; Minata, M.; Katsuma, H.; Kuno, M.; Ito, T.; Komeda, T.; Kita, R.; et al. Disruption of the p16/cyclin D1/retinoblastoma protein pathway in the majority of human hepatocellular carcinomas. Oncology 2001, 60, 346–354. [Google Scholar] [CrossRef]
  72. Edamoto, Y.; Hara, A.; Biernat, W.; Terracciano, L.; Cathomas, G.; Riehle, H.M.; Matsuda, M.; Fujii, H.; Scoazec, J.Y.; Ohgaki, H. Alterations of RB1, p53 and Wnt pathways in hepatocellular carcinomas associated with hepatitis C, hepatitis B and alcoholic liver cirrhosis. Int. J. Cancer 2003, 106, 334–341. [Google Scholar] [CrossRef]
  73. Ito, T.; Nishida, N.; Fukuda, Y.; Nishimura, T.; Komeda, T.; Nakao, K. Alteration of the p14(ARF) gene and p53 status in human hepatocellular carcinomas. J. Gastroenterol. 2004, 39, 355–361. [Google Scholar] [CrossRef]
  74. Rodrigues, R.R.; Barry, C.T. Gene pathway analysis of hepatocellular carcinoma genomic expression datasets. J. Surg. Res. 2011, 170, e85–e92. [Google Scholar] [CrossRef]
  75. Thompson, M.D.; Monga, S.P. WNT/beta-catenin signaling in liver health and disease. Hepatology 2007, 45, 1298–1305. [Google Scholar] [CrossRef]
  76. Wong, C.M.; Fan, S.T.; Ng, I.O. Beta-Catenin mutation and overexpression in hepatocellular carcinoma: Clinicopathologic and prognostic significance. Cancer 2001, 92, 136–145. [Google Scholar] [CrossRef]
  77. Jia, D.; Wei, L.; Guo, W.; Zha, R.; Bao, M.; Chen, Z.; Zhao, Y.; Ge, C.; Zhao, F.; Chen, T.; et al. Genome-wide copy number analyses identified novel cancer genes in hepatocellular carcinoma. Hepatology 2011, 54, 1227–1236. [Google Scholar] [CrossRef]
  78. Wang, K.; Lim, H.Y.; Shi, S.; Lee, J.; Deng, S.; Xie, T.; Zhu, Z.; Wang, Y.; Pocalyko, D.; Yang, W.J.; et al. Genomic landscape of copy number aberrations enables the identification of oncogenic drivers in hepatocellular carcinoma. Hepatology 2013, 58, 706–717. [Google Scholar]
  79. Wilkens, L.; Flemming, P.; Gebel, M.; Bleck, J.; Terkamp, C.; Wingen, L.; Kreipe, H.; Schlegelberger, B. Induction of aneuploidy by increasing chromosomal instability during dedifferentiation of hepatocellular carcinoma. Proc. Natl. Acad. Sci. USA 2004, 101, 1309–1314. [Google Scholar] [CrossRef]
  80. Dore, M.P.; Realdi, G.; Mura, D.; Onida, A.; Massarelli, G.; Dettori, G.; Graham, D.Y.; Sepulveda, A.R. Genomic instability in chronic viral hepatitis and hepatocellular carcinoma. Hum. Pathol. 2001, 32, 698–703. [Google Scholar] [CrossRef]
  81. Zhang, S.H.; Cong, W.M.; Xian, Z.H.; Dong, H.; Wu, M.C. Genomic instability in hepatocellular carcinoma revealed by using the random amplified polymorphic DNA method. J. Cancer Res. Clin. Oncol. 2004, 130, 757–761. [Google Scholar] [CrossRef]
  82. Su, H.; Zhao, J.; Xiong, Y.; Xu, T.; Zhou, F.; Yuan, Y.; Zhang, Y.; Zhuang, S.M. Large-scale analysis of the genetic and epigenetic alterations in hepatocellular carcinoma from Southeast China. Mutat. Res. 2008, 641, 27–35. [Google Scholar] [CrossRef]
  83. Lee, S.; Lee, H.J.; Kim, J.H.; Lee, H.S.; Jang, J.J.; Kang, G.H. Aberrant CpG island hypermethylation along multistep hepatocarcinogenesis. Am. J. Pathol. 2003, 163, 1371–1378. [Google Scholar] [CrossRef]
  84. Tischoff, I.; Tannapfe, A. DNA methylation in hepatocellular carcinoma. World J. Gastroenterol. 2008, 14, 1741–1748. [Google Scholar] [CrossRef]
  85. Noh, J.H.; Bae, H.J.; Eun, J.W.; Shen, Q.; Park, S.J.; Kim, H.S.; Nam, B.; Shin, W.C.; Lee, E.K.; Lee, K.; et al. HDAC2 provides a critical support to malignant progression of hepatocellular carcinoma through feedback control of mTORC1 and AKT. Cancer Res. 2014, 74, 1728–1738. [Google Scholar] [CrossRef]
  86. Dannenberg, L.O.; Edenberg, H.J. Epigenetics of gene expression in human hepatoma cells: Expression profiling the response to inhibition of DNA methylation and histone deacetylation. BMC Genomics 2006, 7, 181. [Google Scholar] [CrossRef]
  87. Fan, D.N.; Tsang, F.H.; Tam, A.H.; Au, S.L.; Wong, C.C.; Wei, L.; Lee, J.M.; He, X.; Ng, I.O.; Wong, C.M. Histone lysine methyltransferase, suppressor of variegation 3–9 homolog 1, promotes hepatocellular carcinoma progression and is negatively regulated by microRNA-125b. Hepatology 2013, 57, 637–647. [Google Scholar] [CrossRef]
  88. Coradini, D.; Speranza, A. Histone deacetylase inhibitors for treatment of hepatocellular carcinoma. Acta Pharmacol. Sin. 2005, 26, 1025–1033. [Google Scholar] [CrossRef]
  89. Calvisi, D.F.; Ladu, S.; Gorden, A.; Farina, M.; Lee, J.S.; Conner, E.A.; Schroeder, I.; Factor, V.M.; Thorgeirsson, S.S. Mechanistic and prognostic significance of aberrant methylation in the molecular pathogenesis of human hepatocellular carcinoma. J. Clin. Investig. 2007, 117, 2713–2722. [Google Scholar] [CrossRef]
  90. Giles, R.H.; van Es, J.H.; Clevers, H. Caught up in a Wnt storm: Wnt signaling in cancer. Biochim. Biophys. Acta 2003, 1653, 1–24. [Google Scholar]
  91. Lee, H.S.; Park, M.H.; Yang, S.J.; Park, K.C.; Kim, N.S.; Kim, Y.S.; Kim, D.I.; Yoo, H.S.; Choi, E.J.; Yeom, Y.I. Novel candidate targets of Wnt/beta-catenin signaling in hepatoma cells. Life Sci. 2007, 80, 690–698. [Google Scholar] [CrossRef]
  92. Hussain, S.P.; Schwank, J.; Staib, F.; Wang, X.W.; Harris, C.C. TP53 mutations and hepatocellular carcinoma: Insights into the etiology and pathogenesis of liver cancer. Oncogene 2007, 26, 2166–2176. [Google Scholar] [CrossRef]
  93. Chen, Y.W.; Jeng, Y.M.; Yeh, S.H.; Chen, P.J. P53 gene and Wnt signaling in benign neoplasms: Beta-catenin mutations in hepatic adenoma but not in focal nodular hyperplasia. Hepatology 2002, 36, 927–935. [Google Scholar] [CrossRef]
  94. Luo, D.; Liu, Q.F.; Gove, C.; Naomov, N.; Su, J.J.; Williams, R. Analysis of N-ras gene mutation and p53 gene expression in human hepatocellular carcinomas. World J. Gastroenterol. 1998, 4, 97–99. [Google Scholar]
  95. Iwamoto, K.S.; Mizuno, T.; Tokuoka, S.; Mabuchi, K.; Seyama, T. Frequency of p53 mutations in hepatocellular carcinomas from atomic bomb survivors. J. Natl. Cancer Inst. 1998, 90, 1167–1168. [Google Scholar] [CrossRef]
  96. Hsu, H.C.; Jeng, Y.M.; Mao, T.L.; Chu, J.S.; Lai, P.L.; Peng, S.Y. Beta-catenin mutations are associated with a subset of low-stage hepatocellular carcinoma negative for hepatitis B virus and with favorable prognosis. Am. J. Pathol. 2000, 157, 763–770. [Google Scholar] [CrossRef]
  97. Huang, S.; He, J.; Zhang, X.; Bian, Y.; Yang, L.; Xie, G.; Zhang, K.; Tang, W.; Stelter, A.A.; Wang, Q.; et al. Activation of the hedgehog pathway in human hepatocellular carcinomas. Carcinogenesis 2006, 27, 1334–1340. [Google Scholar] [CrossRef]
  98. Ingham, P.W.; McMahon, A.P. Hedgehog signaling in animal development: Paradigms and principles. Genes Dev. 2001, 15, 3059–3087. [Google Scholar] [CrossRef]
  99. Cheng, W.T.; Xu, K.; Tian, D.Y.; Zhang, Z.G.; Liu, L.J.; Chen, Y. Role of Hedgehog signaling pathway in proliferation and invasiveness of hepatocellular carcinoma cells. Int. J. Oncol. 2009, 34, 829–836. [Google Scholar]
  100. Patil, M.A.; Zhang, J.; Ho, C.; Cheung, S.T.; Fan, S.T.; Chen, X. Hedgehog signaling in human hepatocellular carcinoma. Cancer Biol. Ther. 2006, 5, 111–117. [Google Scholar] [CrossRef]
  101. Shackel, N.A.; McGuinness, P.H.; Abbott, C.A.; Gorrell, M.D.; McCaughan, G.W. Insights into the pathobiology of hepatitis C virus-associated cirrhosis—Analysis of intrahepatic differential gene expression. Am. J. Pathol. 2002, 160, 641–654. [Google Scholar] [CrossRef]
  102. Shackel, N.A.; McGuinness, P.H.; Abbott, C.A.; Gorrell, M.D.; McCaughan, G.W. Identification of novel molecules and pathogenic pathways in primary biliary cirrhosis: cDNA array analysis of intrahepatic differential gene expression. Gut 2001, 49, 565–576. [Google Scholar] [CrossRef]
  103. Yang, S.F.; Wang, S.N.; Wu, C.F.; Yeh, Y.T.; Chai, C.Y.; Chunag, S.C.; Sheen, M.C.; Lee, K.T. Altered p-STAT3 (tyr705) expression is associated with histological grading and intratumour microvessel density in hepatocellular carcinoma. J. Clin. Pathol. 2007, 60, 642–648. [Google Scholar] [CrossRef]
  104. He, G.; Karin, M. NF-kappaB and STAT3—Key players in liver inflammation and cancer. Cell. Res. 2011, 21, 159–168. [Google Scholar] [CrossRef]
  105. Calvisi, D.F.; Ladu, S.; Gorden, A.; Farina, M.; Conner, E.A.; Lee, J.S.; Factor, V.M.; Thorgeirsson, S.S. Ubiquitous activation of Ras and Jak/Stat pathways in human HCC. Gastroenterology 2006, 130, 1117–1128. [Google Scholar] [CrossRef]
  106. Kisseleva, T.; Bhattacharya, S.; Braunstein, J.; Schindler, C.W. Signaling through the JAK/STAT pathway, recent advances and future challenges. Gene 2002, 285, 1–24. [Google Scholar] [CrossRef]
  107. Rebouissou, S.; Amessou, M.; Couchy, G.; Poussin, K.; Imbeaud, S.; Pilati, C.; Izard, T.; Balabaud, C.; Bioulac-Sage, P.; Zucman-Rossi, J. Frequent in-frame somatic deletions activate gp130 in inflammatory hepatocellular tumours. Nature 2009, 457, 200–204. [Google Scholar] [CrossRef] [Green Version]
  108. Bollrath, J.; Greten, F.R. IKK/NF-kappaB and STAT3 pathways: Central signalling hubs in inflammation-mediated tumour promotion and metastasis. EMBO Rep. 2009, 10, 1314–1319. [Google Scholar] [CrossRef]
  109. Wang, X.; Meng, X.; Sun, X.; Liu, M.; Gao, S.; Zhao, J.; Pei, F.; Yu, H. Wnt/beta-catenin signaling pathway may regulate cell cycle and expression of cyclin A and cyclin E protein in hepatocellular carcinoma cells. Cell Cycle 2009, 8, 1567–1570. [Google Scholar] [CrossRef]
  110. Corlu, A.; Loyer, P. Regulation of the g1/s transition in hepatocytes: Involvement of the cyclin-dependent kinase cdk1 in the DNA replication. Int. J. Hepatol. 2012, 2012, 689324. [Google Scholar]
  111. Guegan, J.P.; Fremin, C.; Baffet, G. The MAPK MEK1/2-ERK1/2 Pathway and Its Implication in Hepatocyte Cell Cycle Control. Int. J. Hepatol. 2012, 2012, 328372. [Google Scholar]
  112. Collin de L’hortet, A.; Gilgenkrantz, H.; Guidotti, J.E. EGFR: A master piece in G1/S phase transition of liver regeneration. Int. J. Hepatol. 2012, 2012, 476910. [Google Scholar]
  113. Kastan, M.B.; Bartek, J. Cell-cycle checkpoints and cancer. Nature 2004, 432, 316–323. [Google Scholar] [CrossRef]
  114. Fausto, N.; Campbell, J.S.; Riehle, K.J. Liver regeneration. Hepatology 2006, 43, S45–S53. [Google Scholar] [CrossRef]
  115. Koniaris, L.G.; McKillop, I.H.; Schwartz, S.I.; Zimmers, T.A. Liver regeneration. J. Am. Coll. Surg. 2003, 197, 634–659. [Google Scholar] [CrossRef]
  116. Woo, H.G.; Lee, J.H.; Yoon, J.H.; Kim, C.Y.; Lee, H.S.; Jang, J.J.; Yi, N.J.; Suh, K.S.; Lee, K.U.; Park, E.S.; et al. Identification of a cholangiocarcinoma-like gene expression trait in hepatocellular carcinoma. Cancer Res. 2010, 70, 3034–3041. [Google Scholar] [CrossRef]
  117. Andersen, J.B.; Loi, R.; Perra, A.; Factor, V.M.; Ledda-Columbano, G.M.; Columbano, A.; Thorgeirsson, S.S. Progenitor-derived hepatocellular carcinoma model in the rat. Hepatology 2010, 51, 1401–1409. [Google Scholar] [CrossRef]
  118. Yamashita, T.; Forgues, M.; Wang, W.; Kim, J.W.; Ye, Q.; Jia, H.; Budhu, A.; Zanetti, K.A.; Chen, Y.; Qin, L.X.; et al. EpCAM and alpha-fetoprotein expression defines novel prognostic subtypes of hepatocellular carcinoma. Cancer Res. 2008, 68, 1451–1461. [Google Scholar] [CrossRef]
  119. Chiang, D.Y.; Villanueva, A.; Hoshida, Y.; Peix, J.; Newell, P.; Minguez, B.; LeBlanc, A.C.; Donovan, D.J.; Thung, S.N.; Sole, M.; et al. Focal gains of VEGFA and molecular classification of hepatocellular carcinoma. Cancer Res. 2008, 68, 6779–6788. [Google Scholar] [CrossRef]
  120. Villanueva, A.; Alsinet, C.; Yanger, K.; Hoshida, Y.; Zong, Y.; Toffanin, S.; Rodriguez-Carunchio, L.; Sole, M.; Thung, S.; Stanger, B.Z.; et al. Notch signaling is activated in human hepatocellular carcinoma and induces tumor formation in mice. Gastroenterology 2012, 143, 1660–1669. [Google Scholar] [CrossRef]
  121. Mayhew, C.N.; Carter, S.L.; Fox, S.R.; Sexton, C.R.; Reed, C.A.; Srinivasan, S.V.; Liu, X.; Wikenheiser-Brokamp, K.; Boivin, G.P.; Lee, J.S.; et al. RB loss abrogates cell cycle control and genome integrity to promote liver tumorigenesis. Gastroenterology 2007, 133, 976–984. [Google Scholar] [CrossRef]
  122. Ahn, S.M.; Jang, S.J.; Shim, J.H.; Kim, D.; Hong, S.M.; Sung, C.O.; Baek, D.; Haq, F.; Ansari, A.A.; Lee, S.Y.; et al. A genomic portrait of resectable hepatocellular carcinomas: Implications of RB1 and FGF19 aberrations for patient stratification. Hepatology 2014. [Google Scholar] [CrossRef]
  123. Woo, H.G.; Park, E.S.; Cheon, J.H.; Kim, J.H.; Lee, J.S.; Park, B.J.; Kim, W.; Park, S.C.; Chung, Y.J.; Kim, B.G.; et al. Gene expression-based recurrence prediction of hepatitis B virus-related human hepatocellular carcinoma. Clin. Cancer Res. 2008, 14, 2056–2064. [Google Scholar] [CrossRef]
  124. Coulouarn, C.; Factor, V.M.; Thorgeirsson, S.S. Transforming growth factor-beta gene expression signature in mouse hepatocytes predicts clinical outcome in human cancer. Hepatology 2008, 47, 2059–2067. [Google Scholar] [CrossRef]
  125. Lee, J.S.; Chu, I.S.; Mikaelyan, A.; Calvisi, D.F.; Heo, J.; Reddy, J.K.; Thorgeirsson, S.S. Application of comparative functional genomics to identify best-fit mouse models to study human cancer. Nat. Genet. 2004, 36, 1306–1311. [Google Scholar] [CrossRef]
  126. Katoh, H.; Ojima, H.; Kokubu, A.; Saito, S.; Kondo, T.; Kosuge, T.; Hosoda, F.; Imoto, I.; Inazawa, J.; Hirohashi, S.; et al. Genetically distinct and clinically relevant classification of hepatocellular carcinoma: Putative therapeutic targets. Gastroenterology 2007, 133, 1475–1486. [Google Scholar] [CrossRef]
  127. Marquardt, J.U.; Seo, D.; Andersen, J.B.; Gillen, M.C.; Kim, M.S.; Conner, E.A.; Galle, P.R.; Factor, V.M.; Park, Y.N.; Thorgeirsson, S.S. Sequential transcriptome analysis of human liver cancer indicates late stage acquisition of malignant traits. J. Hepatol. 2014, 60, 346–353. [Google Scholar] [CrossRef]
  128. Chiba, T.; Kita, K.; Zheng, Y.W.; Yokosuka, O.; Saisho, H.; Iwama, A.; Nakauchi, H.; Taniguchi, H. Side population purified from hepatocellular carcinoma cells harbors cancer stem cell-like properties. Hepatology 2006, 44, 240–251. [Google Scholar]
  129. Hsia, C.C.; Evarts, R.P.; Nakatsukasa, H.; Marsden, E.R.; Thorgeirsson, S.S. Occurrence of oval-type cells in hepatitis B virus-associated human hepatocarcinogenesis. Hepatology 1992, 16, 1327–1333. [Google Scholar] [CrossRef]
  130. Mishra, L.; Banker, T.; Murray, J.; Byers, S.; Thenappan, A.; He, A.R.; Shetty, K.; Johnson, L.; Reddy, E.P. Liver stem cells and hepatocellular carcinoma. Hepatology 2009, 49, 318–329. [Google Scholar] [CrossRef]
  131. Wu, P.C.; Lau, V.K.; Fang, J.W.; Lai, V.C.; Lai, C.L.; Lau, J.Y. Imbalance between cell proliferation and cellular DNA fragmentation in hepatocellular carcinoma. Liver 1999, 19, 444–451. [Google Scholar] [CrossRef]
  132. Hoshida, Y.; Villanueva, A.; Sangiovanni, A.; Sole, M.; Hur, C.; Andersson, K.L.; Chung, R.T.; Gould, J.; Kojima, K.; Gupta, S.; et al. Prognostic gene expression signature for patients with hepatitis C-related early-stage cirrhosis. Gastroenterology 2013, 144, 1024–1030. [Google Scholar] [CrossRef]
  133. Nault, J.C.; de Reynies, A.; Villanueva, A.; Calderaro, J.; Rebouissou, S.; Couchy, G.; Decaens, T.; Franco, D.; Imbeaud, S.; Rousseau, F.; et al. A hepatocellular carcinoma 5-gene score associated with survival of patients after liver resection. Gastroenterology 2013, 145, 176–187. [Google Scholar] [CrossRef]
  134. Rice, J. Metastasis: The rude awakening. Nature 2012, 485, S55–S57. [Google Scholar] [CrossRef]
  135. Paget, S. The distribution of secondary growths in cancer of the breast. 1889. Cancer Metastasis Rev. 1989, 8, 98–101. [Google Scholar]
  136. Fidler, I.J. The pathogenesis of cancer metastasis: The “seed and soil” hypothesis revisited. Nat. Rev. Cancer 2003, 3, 453–458. [Google Scholar] [CrossRef]
  137. Woo, H.G.; Park, E.S.; Thorgeirsson, S.S.; Kim, Y.J. Exploring genomic profiles of hepatocellular carcinoma. Mol. Carcinog. 2011, 50, 235–243. [Google Scholar] [CrossRef]
  138. Villa, E.; Fattovich, G. No inflammation? No cancer! Clear HBV early and live happily. J. Hepatol. 2010, 52, 768–770. [Google Scholar] [CrossRef]
  139. Wherry, E.J. T cell exhaustion. Nat. Immunol. 2011, 12, 492–499. [Google Scholar] [CrossRef]
  140. Pollard, J.W. Tumour-educated macrophages promote tumour progression and metastasis. Nat. Rev. Cancer 2004, 4, 71–78. [Google Scholar] [CrossRef]
  141. Murata, Y.; Ohteki, T.; Koyasu, S.; Hamuro, J. IFN-gamma and pro-inflammatory cytokine production by antigen-presenting cells is dictated by intracellular thiol redox status regulated by oxygen tension. Eur. J. Immunol. 2002, 32, 2866–2873. [Google Scholar] [CrossRef]
  142. Kuang, D.M.; Zhao, Q.; Peng, C.; Xu, J.; Zhang, J.P.; Wu, C.; Zheng, L. Activated monocytes in peritumoral stroma of hepatocellular carcinoma foster immune privilege and disease progression through PD-L1. J. Exp. Med. 2009, 206, 1327–1337. [Google Scholar] [CrossRef]
  143. Oh, B.K.; Kim, Y.J.; Park, C.; Park, Y.N. Up-regulation of telomere-binding proteins, TRF1, TRF2, and TIN2 is related to telomere shortening during human multistep hepatocarcinogenes. Am. J. Pathol. 2005, 166, 73–80. [Google Scholar] [CrossRef]
  144. Midorikawa, Y.; Yamamoto, S.; Tsuji, S.; Kamimura, N.; Ishikawa, S.; Igarashi, H.; Makuuchi, M.; Kokudo, N.; Sugimura, H.; Aburatani, H. Allelic imbalances and homozygous deletion on 8p23.2 for stepwise progression of hepatocarcinogenesis. Hepatology 2009, 49, 513–522. [Google Scholar] [CrossRef]
  145. Rim, K.S.; Sakamoto, M.; Watanabe, H.; Matsuno, Y.; Nakanishi, Y.; Mukai, K.; Hirohashi, S. Pathology and DNA cytophotometry of small hepatocellular carcinoma with a nodule-in-nodule appearance–Evidence for stepwise progression of hepatocellular carcinoma. Jpn. J. Clin. Oncol. 1993, 23, 26–33. [Google Scholar]
  146. Park, D.H.; Shin, J.W.; Park, S.K.; Seo, J.N.; Li, L.; Jang, J.J.; Lee, M.J. Diethylnitrosamine (DEN) induces irreversible hepatocellular carcinogenesis through overexpression of G1/S-phase regulatory proteins in rat. Toxicol. Lett. 2009, 191, 321–326. [Google Scholar] [CrossRef]
  147. Loguercio, C.; Federico, A. Oxidative stress in viral and alcoholic hepatitis. Free Radic. Biol. Med. 2003, 34, 1–10. [Google Scholar] [CrossRef]
  148. Korenaga, M.; Wang, T.; Li, Y.; Showalter, L.A.; Chan, T.; Sun, J.; Weinman, S.A. Hepatitis C virus core protein inhibits mitochondrial electron transport and increases reactive oxygen species (ROS) production. J. Biol. Chem. 2005, 280, 37481–37488. [Google Scholar]
  149. Okuda, M.; Li, K.; Beard, M.R.; Showalter, L.A.; Scholle, F.; Lemon, S.M.; Weinman, S.A. Mitochondrial injury, oxidative stress, and antioxidant gene expression are induced by hepatitis C virus core protein. Gastroenterology 2002, 122, 366–375. [Google Scholar] [CrossRef]
  150. Golden-Mason, L.; Palmer, B.; Klarquist, J.; Mengshol, J.A.; Castelblanco, N.; Rosen, H.R. Upregulation of PD-1 expression on circulating and intrahepatic hepatitis C virus-specific CD8+ T cells associated with reversible immune dysfunction. J. Virol. 2007, 81, 9249–9258. [Google Scholar] [CrossRef]
  151. Ha, S.J.; West, E.E.; Araki, K.; Smith, K.A.; Ahmed, R. Manipulating both the inhibitory and stimulatory immune system towards the success of therapeutic vaccination against chronic viral infections. Immunol. Rev. 2008, 223, 317–333. [Google Scholar] [CrossRef]
  152. Peng, G.; Li, S.; Wu, W.; Tan, X.; Chen, Y.; Chen, Z. PD-1 upregulation is associated with HBV-specific T cell dysfunction in chronic hepatitis B patients. Mol. Immunol. 2008, 45, 963–970. [Google Scholar] [CrossRef]
  153. Chiba, T.; Marusawa, H. A novel mechanism for inflammation-associated carcinogenesis; an important role of activation-induced cytidine deaminase (AID) in mutation induction. J. Mol. Med. (Berl.) 2009, 87, 1023–1027. [Google Scholar] [CrossRef]
  154. Pasquinelli, C.; Bhavani, K.; Chisari, F.V. Multiple oncogenes and tumor suppressor genes are structurally and functionally intact during hepatocarcinogenesis in hepatitis B virus transgenic mice. Cancer Res. 1992, 52, 2823–2829. [Google Scholar]
  155. Chisari, F.V.; Filippi, P.; Buras, J.; McLachlan, A.; Popper, H.; Pinkert, C.A.; Palmiter, R.D.; Brinster, R.L. Structural and pathological effects of synthesis of hepatitis B virus large envelope polypeptide in transgenic mice. Proc. Natl. Acad. Sci. USA 1987, 84, 6909–6913. [Google Scholar] [CrossRef]
  156. Kasprzak, A.; Adamek, A. Role of hepatitis C virus proteins (C, NS3, NS5A) in hepatic oncogenesis. Hepatol. Res. 2008, 38, 1–26. [Google Scholar] [CrossRef]
  157. Banerjee, A.; Ray, R.B.; Ray, R. Oncogenic potential of hepatitis C virus proteins. Viruses 2010, 2, 2108–2133. [Google Scholar] [CrossRef]
  158. Xie, H.; Song, J.; Liu, K.; Ji, H.; Shen, H.; Hu, S.; Yang, G.; Du, Y.; Zou, X.; Jin, H.; et al. The expression of hypoxia-inducible factor-1alpha in hepatitis B virus-related hepatocellular carcinoma: Correlation with patients’ prognosis and hepatitis B virus X protein. Dig. Dis. Sci. 2008, 53, 3225–3233. [Google Scholar] [CrossRef]
  159. Yoo, Y.G.; Na, T.Y.; Seo, H.W.; Seong, J.K.; Park, C.K.; Shin, Y.K.; Lee, M.O. Hepatitis B virus X protein induces the expression of MTA1 and HDAC1, which enhances hypoxia signaling in hepatocellular carcinoma cells. Oncogene 2008, 27, 3405–3413. [Google Scholar]
  160. Lewis, C.E.; Pollard, J.W. Distinct role of macrophages in different tumor microenvironments. Cancer Res. 2006, 66, 605–612. [Google Scholar] [CrossRef]
  161. Murdoch, C.; Lewis, C.E. Macrophage migration and gene expression in response to tumor hypoxia. Int. J. Cancer 2005, 117, 701–708. [Google Scholar] [CrossRef]
  162. Ikeda, E.; Achen, M.G.; Breier, G.; Risau, W. Hypoxia-induced transcriptional activation and increased mRNA stability of vascular endothelial growth factor in C6 glioma cells. J. Biol. Chem. 1995, 270, 19761–19766. [Google Scholar] [CrossRef]
  163. Forsythe, J.A.; Jiang, B.H.; Iyer, N.V.; Agani, F.; Leung, S.W.; Koos, R.D.; Semenza, G.L. Activation of vascular endothelial growth factor gene transcription by hypoxia-inducible factor 1. Mol. Cell. Biol. 1996, 16, 4604–4613. [Google Scholar]
  164. Wu, X.Z.; Xie, G.R.; Chen, D. Hypoxia and hepatocellular carcinoma: The therapeutic target for hepatocellular carcinoma. J. Gastroenterol. Hepatol. 2007, 22, 1178–1182. [Google Scholar] [CrossRef]
  165. Yoshimoto, S.; Loo, T.M.; Atarashi, K.; Kanda, H.; Sato, S.; Oyadomari, S.; Iwakura, Y.; Oshima, K.; Morita, H.; Hattori, M.; et al. Obesity-induced gut microbial metabolite promotes liver cancer through senescence secretome. Nature 2013, 499, 97–101. [Google Scholar] [CrossRef]
  166. Zhang, H.L.; Yu, L.X.; Yang, W.; Tang, L.; Lin, Y.; Wu, H.; Zhai, B.; Tan, Y.X.; Shan, L.; Liu, Q.; et al. Profound impact of gut homeostasis on chemically-induced pro-tumorigenic inflammation and hepatocarcinogenesis in rats. J. Hepatol. 2012, 57, 803–812. [Google Scholar] [CrossRef]
  167. Sidhu, S.S.; Mengistab, A.T.; Tauscher, A.N.; LaVail, J.; Basbaum, C. The microvesicle as a vehicle for EMMPRIN in tumor-stromal interactions. Oncogene 2004, 23, 956–963. [Google Scholar] [CrossRef]
  168. Kornek, M.; Popov, Y.; Libermann, T.A.; Afdhal, N.H.; Schuppan, D. Human T cell microparticles circulate in blood of hepatitis patients and induce fibrolytic activation of hepatic stellate cells. Hepatology 2011, 53, 230–242. [Google Scholar] [CrossRef]
  169. Valenti, R.; Huber, V.; Filipazzi, P.; Pilla, L.; Sovena, G.; Villa, A.; Corbelli, A.; Fais, S.; Parmiani, G.; Rivoltini, L. Human tumor-released microvesicles promote the differentiation of myeloid cells with transforming growth factor-beta-mediated suppressive activity on T lymphocytes. Cancer Res. 2006, 66, 9290–9298. [Google Scholar] [CrossRef]
  170. Yu, S.; Liu, C.; Su, K.; Wang, J.; Liu, Y.; Zhang, L.; Li, C.; Cong, Y.; Kimberly, R.; Grizzle, W.E.; et al. Tumor exosomes inhibit differentiation of bone marrow dendritic cells. J. Immunol. 2007, 178, 6867–6875. [Google Scholar] [CrossRef]
  171. Lemoinne, S.; Thabut, D.; Housset, C.; Moreau, R.; Valla, D.; Boulanger, C.M.; Rautou, P.E. The emerging roles of microvesicles in liver diseases. Nat. Rev. Gastroenterol. Hepatol. 2014. [Google Scholar] [CrossRef]
  172. Quesenberry, P.J.; Goldberg, L.; Aliotta, J.M.; Pereira, M.; Wen, S.; Camussi, G.; Dooner, M.S. Cellular phenotype and extracellular vesicles: Basic and clinical considerations. Stem Cells Dev. 2014. [Google Scholar] [CrossRef]
  173. Webber, J.; Steadman, R.; Mason, M.D.; Tabi, Z.; Clayton, A. Cancer exosomes trigger fibroblast to myofibroblast differentiation. Cancer Res. 2010, 70, 9621–9630. [Google Scholar] [CrossRef]
  174. Runz, S.; Keller, S.; Rupp, C.; Stoeck, A.; Issa, Y.; Koensgen, D.; Mustea, A.; Sehouli, J.; Kristiansen, G.; Altevogt, P. Malignant ascites-derived exosomes of ovarian carcinoma patients contain CD24 and EpCAM. Gynecol. Oncol. 2007, 107, 563–571. [Google Scholar]
  175. Paini, A.; Scholz, G.; Marin-Kuan, M.; Schilter, B.; O’Brien, J.; van Bladeren, P.J.; Rietjens, I.M. Quantitative comparison between in vivo DNA adduct formation from exposure to selected DNA-reactive carcinogens, natural background levels of DNA adduct formation and tumour incidence in rodent bioassays. Mutagenesis 2011, 26, 605–618. [Google Scholar] [CrossRef]
  176. Shirabe, K.; Toshima, T.; Taketomi, A.; Taguchi, K.; Yoshizumi, T.; Uchiyama, H.; Harimoto, N.; Kajiyama, K.; Egashira, A.; Maehara, Y. Hepatic aflatoxin B1-DNA adducts and TP53 mutations in patients with hepatocellular carcinoma despite low exposure to aflatoxin B1 in southern Japan. Liver Int. 2011, 31, 1366–1372. [Google Scholar] [CrossRef]
  177. Wang, J.S.; Groopman, J.D. DNA damage by mycotoxins. Mutat. Res. 1999, 424, 167–181. [Google Scholar] [CrossRef]
  178. Besaratinia, A.; Kim, S.I.; Hainaut, P.; Pfeifer, G.P. In vitro recapitulating of TP53 mutagenesis in hepatocellular carcinoma associated with dietary aflatoxin B1 exposure. Gastroenterology 2009, 137, 1127–1137. [Google Scholar] [CrossRef]
  179. Gursoy-Yuzugullu, O.; Yuzugullu, H.; Yilmaz, M.; Ozturk, M. Aflatoxin genotoxicity is associated with a defective DNA damage response bypassing p53 activation. Liver Int. 2011, 31, 561–571. [Google Scholar] [CrossRef]
  180. Pineau, P.; Marchio, A.; Battiston, C.; Cordina, E.; Russo, A.; Terris, B.; Qin, L.X.; Turlin, B.; Tang, Z.Y.; Mazzaferro, V.; et al. Chromosome instability in human hepatocellular carcinoma depends on p53 status and aflatoxin exposure. Mutat. Res. 2008, 653, 6–13. [Google Scholar] [CrossRef]
  181. Cetta, F.; Zuckermann, M.; del Vecchio, M.T.; Ercolani, G.; Mazziotti, A. Histological and genetic heterogeneity in synchronous hepatocellular carcinoma. Gut 2001, 49, 155–156. [Google Scholar] [CrossRef]
  182. Marusyk, A.; Almendro, V.; Polyak, K. Intra-tumour heterogeneity: A looking glass for cancer? Nat. Rev. Cancer 2012, 12, 323–334. [Google Scholar] [CrossRef]
  183. Frank, A.; Seitz, H.K.; Bartsch, H.; Frank, N.; Nair, J. Immunohistochemical detection of 1,N6-ethenodeoxyadenosine in nuclei of human liver affected by diseases predisposing to hepato-carcinogenesis. Carcinogenesis 2004, 25, 1027–1031. [Google Scholar] [CrossRef]
  184. Navasumrit, P.; Ward, T.H.; O’Connor, P.J.; Nair, J.; Frank, N.; Bartsch, H. Ethanol enhances the formation of endogenously and exogenously derived adducts in rat hepatic DNA. Mutat. Res. 2001, 479, 81–94. [Google Scholar] [CrossRef]
  185. Barash, H.; Gross, E.R.; Edrei, Y.; Ella, E.; Israel, A.; Cohen, I.; Corchia, N.; Ben-Moshe, T.; Pappo, O.; Pikarsky, E.; et al. Accelerated carcinogenesis following liver regeneration is associated with chronic inflammation-induced double-strand DNA breaks. Proc. Natl. Acad. Sci. USA 2010, 107, 2207–2212. [Google Scholar] [CrossRef]
  186. Reuter, S.; Gupta, S.C.; Chaturvedi, M.M.; Aggarwal, B.B. Oxidative stress, inflammation, and cancer: How are they linked? Free Radi. Biol. Med. 2010, 49, 1603–1616. [Google Scholar] [CrossRef]
  187. Shimoda, R.; Nagashima, M.; Sakamoto, M.; Yamaguchi, N.; Hirohashi, S.; Yokota, J.; Kasai, H. Increased formation of oxidative DNA damage, 8-hydroxydeoxyguanosine, in human livers with chronic hepatitis. Cancer Res. 1994, 54, 3171–3172. [Google Scholar]
  188. Shen, Z. Genomic instability and cancer: An introduction. J. Mol. Cell. Biol. 2011, 3, 1–3. [Google Scholar] [CrossRef]
  189. Mohammed, N.A.; Abd El-Aleem, S.; Appleton, I.; Maklouf, M.M.; Said, M.; McMahon, R.F. Expression of nitric oxide synthase isoforms in human liver cirrhosis. J. Pathol. 2003, 200, 647–655. [Google Scholar] [CrossRef]
  190. Burhans, W.C.; Weinberger, M. DNA replication stress, genome instability and aging. Nucleic Acids Res. 2007, 35, 7545–7556. [Google Scholar] [CrossRef]
  191. Sangiovanni, A.; Colombo, E.; Radaelli, F.; Bortoli, A.; Bovo, G.; Casiraghi, M.A.; Ceriani, R.; Roffi, L.; Redaelli, A.; Rossini, A.; et al. Hepatocyte proliferation and risk of hepatocellular carcinoma in cirrhotic patients. Am. J. Gastroenterol. 2001, 96, 1575–1580. [Google Scholar] [CrossRef]
  192. Plentz, R.R.; Caselitz, M.; Bleck, J.S.; Gebel, M.; Flemming, P.; Kubicka, S.; Manns, M.P.; Rudolph, K.L. Hepatocellular telomere shortening correlates with chromosomal instability and the development of human hepatoma. Hepatology 2004, 40, 80–86. [Google Scholar]
  193. Bralet, M.P.; Pichard, V.; Ferry, N. Demonstration of direct lineage between hepatocytes and hepatocellular carcinoma in diethylnitrosamine-treated rats. Hepatology 2002, 36, 623–630. [Google Scholar] [CrossRef]
  194. Matsuzaki, K.; Murata, M.; Yoshida, K.; Sekimoto, G.; Uemura, Y.; Sakaida, N.; Kaibori, M.; Kamiyama, Y.; Nishizawa, M.; Fujisawa, J.; et al. Chronic inflammation associated with hepatitis C virus infection perturbs hepatic transforming growth factor beta signaling, promoting cirrhosis and hepatocellular carcinoma. Hepatology 2007, 46, 48–57. [Google Scholar] [CrossRef]
  195. De Lalla, C.; Galli, G.; Aldrighetti, L.; Romeo, R.; Mariani, M.; Monno, A.; Nuti, S.; Colombo, M.; Callea, F.; Porcelli, S.A.; et al. Production of profibrotic cytokines by invariant NKT cells characterizes cirrhosis progression in chronic viral hepatitis. J. Immunol. 2004, 173, 1417–1425. [Google Scholar]
  196. Giron-Gonzalez, J.A.; Martinez-Sierra, C.; Rodriguez-Ramos, C.; Macias, M.A.; Rendon, P.; Diaz, F.; Fernandez-Gutierrez, C.; Martin-Herrera, L. Implication of inflammation-related cytokines in the natural history of liver cirrhosis. Liver Int. 2004, 24, 437–445. [Google Scholar] [CrossRef]
  197. Malato, Y.; Naqvi, S.; Schurmann, N.; Ng, R.; Wang, B.; Zape, J.; Kay, M.A.; Grimm, D.; Willenbring, H. Fate tracing of mature hepatocytes in mouse liver homeostasis and regeneration. J. Clin. Investig. 2011, 121, 4850–4860. [Google Scholar] [CrossRef]
  198. Tang, Y.; Kitisin, K.; Jogunoori, W.; Li, C.; Deng, C.X.; Mueller, S.C.; Ressom, H.W.; Rashid, A.; He, A.R.; Mendelson, J.S.; et al. Progenitor/stem cells give rise to liver cancer due to aberrant TGF-beta and IL-6 signaling. Proc. Natl. Acad. Sci. USA 2008, 105, 2445–2450. [Google Scholar] [CrossRef]
  199. Rodriguez-Peralvarez, M.; Tsochatzis, E.; Naveas, M.C.; Pieri, G.; Garcia-Caparros, C.; O’Beirne, J.; Poyato-Gonzalez, A.; Ferrin-Sanchez, G.; Montero-Alvarez, J.L.; Patch, D.; et al. Reduced Exposure to Calcineurin Inhibitors Early After Liver Transplantation Prevents Recurrence of Hepatocellular Carcinoma. J. Hepatol. 2013, 59, 1193–1199. [Google Scholar] [CrossRef]
  200. Stadlbauer, V.; Schaffellner, S.; Kniepeiss, D.; Jakoby, E.; Stauber, R.; Iberer, F.; Tscheliessnigg, K.H. Experiences in liver transplantation for hepatocellular carcinoma. Transplant. Proc. 2004, 36, 195–198. [Google Scholar] [CrossRef]
  201. Maluccio, M.; Sharma, V.; Lagman, M.; Vyas, S.; Yang, H.; Li, B.; Suthanthiran, M. Tacrolimus enhances transforming growth factor-beta1 expression and promotes tumor progression. Transplantation 2003, 76, 597–602. [Google Scholar] [CrossRef]
  202. Bowen, D.G.; Zen, M.; Holz, L.; Davis, T.; McCaughan, G.W.; Bertolino, P. The site of primary T cell activation is a determinant of the balance between intrahepatic tolerance and immunity. J. Clin. Investig. 2004, 114, 701–712. [Google Scholar] [CrossRef]
  203. Thomson, A.W.; Knolle, P.A. Antigen-presenting cell function in the tolerogenic liver environment. Nat. Rev. Immunol. 2010, 10, 753–766. [Google Scholar] [CrossRef]
  204. Sato, K.; Yabuki, K.; Haba, T.; Maekawa, T. Role of Kupffer cells in the induction of tolerance after liver transplantation. J. Surg. Res. 1996, 63, 433–438. [Google Scholar] [CrossRef]
  205. You, Q.; Cheng, L.; Kedl, R.M.; Ju, C. Mechanism of T cell tolerance induction by murine hepatic Kupffer cells. Hepatology 2008, 48, 978–990. [Google Scholar] [CrossRef]
  206. Chen, Y.; Liu, Z.; Liang, S.; Luan, X.; Long, F.; Chen, J.; Peng, Y.; Yan, L.; Gong, J. Role of Kupffer cells in the induction of tolerance of orthotopic liver transplantation in rats. Liver Transplant. 2008, 14, 823–836. [Google Scholar] [CrossRef]
  207. Yang, J.; Zhang, J.X.; Wang, H.; Wang, G.L.; Hu, Q.G.; Zheng, Q.C. Hepatocellular carcinoma and macrophage interaction induced tumor immunosuppression via Treg requires TLR4 signaling. World J. Gastroenterol. 2012, 18, 2938–2947. [Google Scholar] [CrossRef]
  208. Chen, K.J.; Lin, S.Z.; Zhou, L.; Xie, H.Y.; Zhou, W.H.; Taki-Eldin, A.; Zheng, S.S. Selective recruitment of regulatory T cell through CCR6-CCL20 in hepatocellular carcinoma fosters tumor progression and predicts poor prognosis. PLoS One 2011, 6, e24671. [Google Scholar]
  209. Francisco, L.M.; Sage, P.T.; Sharpe, A.H. The PD-1 pathway in tolerance and autoimmunity. Immunol. Rev. 2010, 236, 219–242. [Google Scholar] [CrossRef]
  210. Sharpe, A.H.; Wherry, E.J.; Ahmed, R.; Freeman, G.J. The function of programmed cell death 1 and its ligands in regulating autoimmunity and infection. Nat. Immunol. 2007, 8, 239–245. [Google Scholar]
  211. Keir, M.E.; Liang, S.C.; Guleria, I.; Latchman, Y.E.; Qipo, A.; Albacker, L.A.; Koulmanda, M.; Freeman, G.J.; Sayegh, M.H.; Sharpe, A.H. Tissue expression of PD-L1 mediates peripheral T cell tolerance. J. Exp. Med. 2006, 203, 883–895. [Google Scholar]
  212. Shirabe, K.; Motomura, T.; Muto, J.; Toshima, T.; Matono, R.; Mano, Y.; Takeishi, K.; Ijichi, H.; Harada, N.; Uchiyama, H.; et al. Tumor-infiltrating lymphocytes and hepatocellular carcinoma: Pathology and clinical management. Int. J. Clin. Oncol. 2010, 15, 552–558. [Google Scholar] [CrossRef]
  213. Shi, F.; Shi, M.; Zeng, Z.; Qi, R.Z.; Liu, Z.W.; Zhang, J.Y.; Yang, Y.P.; Tien, P.; Wang, F.S. PD-1 and PD-L1 upregulation promotes CD8(+) T-cell apoptosis and postoperative recurrence in hepatocellular carcinoma patients. Int. J. Cancer 2011, 128, 887–896. [Google Scholar] [CrossRef]
  214. Seyer, J.M.; Hutcheson, E.T.; Kang, A.H. Collagen polymorphism in normal and cirrhotic human liver. J. Clin. Investig. 1977, 59, 241–248. [Google Scholar] [CrossRef]
  215. Murata, K.; Kudo, M.; Onuma, F.; Motoyama, T. Changes of collagen types at various stages of human liver cirrhosis. Hepatogastroenterology 1984, 31, 158–161. [Google Scholar]
  216. Benyon, R.C.; Iredale, J.P.; Goddard, S.; Winwood, P.J.; Arthur, M.J. Expression of tissue inhibitor of metalloproteinases 1 and 2 is increased in fibrotic human liver. Gastroenterology 1996, 110, 821–831. [Google Scholar] [CrossRef]
  217. Folkman, J. Tumor angiogenesis: Therapeutic implications. N. Engl. J. Med. 1971, 285, 1182–1186. [Google Scholar] [CrossRef]
  218. Jain, R.K. Normalization of tumor vasculature: An emerging concept in antiangiogenic therapy. Science 2005, 307, 58–62. [Google Scholar] [CrossRef]
  219. Yu, D.C.; Chen, J.; Ding, Y.T. Hypoxic and highly angiogenic non-tumor tissues surrounding hepatocellular carcinoma: The “niche” of endothelial progenitor cells. Int. J. Mol. Sci. 2010, 11, 2901–2909. [Google Scholar] [CrossRef]
  220. Li, Y.W.; Qiu, S.J.; Fan, J.; Gao, Q.; Zhou, J.; Xiao, Y.S.; Xu, Y.; Wang, X.Y.; Sun, J.; Huang, X.W. Tumor-infiltrating macrophages can predict favorable prognosis in hepatocellular carcinoma after resection. J. Cancer Res. Clin. Oncol. 2009, 135, 439–449. [Google Scholar] [CrossRef]
  221. Zhou, J.; Ding, T.; Pan, W.; Zhu, L.Y.; Li, L.; Zheng, L. Increased intratumoral regulatory T cells are related to intratumoral macrophages and poor prognosis in hepatocellular carcinoma patients. Int. J. Cancer 2009, 125, 1640–1648. [Google Scholar] [CrossRef]
  222. Gao, Q.; Wang, X.Y.; Qiu, S.J.; Zhou, J.; Shi, Y.H.; Zhang, B.H.; Fan, J. Tumor stroma reaction-related gene signature predicts clinical outcome in human hepatocellular carcinoma. Cancer Sci. 2011, 102, 1522–1531. [Google Scholar] [CrossRef]
  223. Rasanen, K.; Vaheri, A. Activation of fibroblasts in cancer stroma. Exp. Cell. Res. 2010, 316, 2713–2722. [Google Scholar]
  224. Zhao, X.L.; Sun, T.; Che, N.; Sun, D.; Zhao, N.; Dong, X.Y.; Gu, Q.; Yao, Z.; Sun, B.C. Promotion of hepatocellular carcinoma metastasis through matrix metalloproteinase activation by epithelial-mesenchymal transition regulator Twist1. J. Cell. Mol. Med. 2011, 15, 691–700. [Google Scholar] [CrossRef]
  225. Yang, M.H.; Chen, C.L.; Chau, G.Y.; Chiou, S.H.; Su, C.W.; Chou, T.Y.; Peng, W.L.; Wu, J.C. Comprehensive analysis of the independent effect of twist and snail in promoting metastasis of hepatocellular carcinoma. Hepatology 2009, 50, 1464–1474. [Google Scholar] [CrossRef]
  226. Matsumura, T.; Makino, R.; Mitamura, K. Frequent down-regulation of E-cadherin by genetic and epigenetic changes in the malignant progression of hepatocellular carcinomas. Clin. Cancer Res. 2001, 7, 594–599. [Google Scholar]
  227. Kataoka, H.; DeCastro, R.; Zucker, S.; Biswas, C. Tumor cell-derived collagenase-stimulatory factor increases expression of interstitial collagenase, stromelysin, and 72-kDa gelatinase. Cancer Res. 1993, 53, 3154–3158. [Google Scholar]
  228. Xu, J.; Xu, H.Y.; Zhang, Q.; Song, F.; Jiang, J.L.; Yang, X.M.; Mi, L.; Wen, N.; Tian, R.; Wang, L.; et al. HAb18G/CD147 functions in invasion and metastasis of hepatocellular carcinoma. Mol. Cancer Res. 2007, 5, 605–614. [Google Scholar] [CrossRef]
  229. Kim, J.Y.; Kim, W.J.; Kim, H.; Suk, K.; Lee, W.H. The Stimulation of CD147 Induces MMP-9 Expression through ERK and NF-kappaB in Macrophages: Implication for Atherosclerosis. Immune Netw. 2009, 9, 90–97. [Google Scholar] [CrossRef]
  230. Calabro, S.R.M.; Maczurek, A.E.; Morgan, A.J.; Tu, T.; Wen, V.W.; Yee, C.; Roediger, B.; Mridha, A.; Patkunanathan, B.; Lee, M.; et al. Hepatocyte-Produced Matrix Metalloproteinases are regulated by CD147 in Liver Fibrogenesis. PLoS One 2014, in press. [Google Scholar]
  231. Jiang, Y.F.; Yang, Z.H.; Hu, J.Q. Recurrence or metastasis of HCC:predictors, early detection and experimental antiangiogenic therapy. World J. Gastroenterol. 2000, 6, 61–65. [Google Scholar]
  232. Tsai, W.C.; Chao, Y.C.; Lee, W.H.; Chen, A.; Sheu, L.F.; Jin, J.S. Increasing EMMPRIN and matriptase expression in hepatocellular carcinoma: Tissue microarray analysis of immunohistochemical scores with clinicopathological parameters. Histopathology 2006, 49, 388–395. [Google Scholar] [CrossRef]
  233. Zhang, Q.; Chen, X.; Zhou, J.; Zhang, L.; Zhao, Q.; Chen, G.; Xu, J.; Qian, F.; Chen, Z. CD147, MMP-2, MMP-9 and MVD-CD34 are significant predictors of recurrence after liver transplantation in hepatocellular carcinoma patients. Cancer Biol. Ther. 2006, 5, 808–814. [Google Scholar] [CrossRef]
  234. Zhang, Q.; Zhou, J.; Ku, X.M.; Chen, X.G.; Zhang, L.; Xu, J.; Chen, G.S.; Li, Q.; Qian, F.; Tian, R.; et al. Expression of CD147 as a significantly unfavorable prognostic factor in hepatocellular carcinoma. Eur. J. Cancer Prev. 2007, 16, 196–202. [Google Scholar] [CrossRef]
  235. Caudroy, S.; Polette, M.; Nawrocki-Raby, B.; Cao, J.; Toole, B.P.; Zucker, S.; Birembaut, P. EMMPRIN-mediated MMP regulation in tumor and endothelial cells. Clin. Exp. Metastasis 2002, 19, 697–702. [Google Scholar] [CrossRef]
  236. Huang, C.; Sun, Z.; Sun, Y.; Chen, X.; Zhu, X.; Fan, C.; Liu, B.; Zhao, Y.; Zhang, W. Association of increased ligand cyclophilin A and receptor CD147 with hypoxia, angiogenesis, metastasis and prognosis of tongue squamous cell carcinoma. Histopathology 2012, 60, 793–803. [Google Scholar] [CrossRef]
  237. Bougatef, F.; Quemener, C.; Kellouche, S.; Naimi, B.; Podgorniak, M.P.; Millot, G.; Gabison, E.E.; Calvo, F.; Dosquet, C.; Lebbe, C.; et al. EMMPRIN promotes angiogenesis through hypoxia-inducible factor-2alpha-mediated regulation of soluble VEGF isoforms and their receptor VEGFR-2. Blood 2009, 114, 5547–5556. [Google Scholar] [CrossRef]
  238. Chen, Y.; Gou, X.; Ke, X.; Cui, H.; Chen, Z. Human tumor cells induce angiogenesis through positive feedback between CD147 and insulin-like growth factor-I. PLoS One 2012, 7, e40965. [Google Scholar] [CrossRef]
  239. Li, X.M.; Tang, Z.Y.; Qin, L.X.; Zhou, J.; Sun, H.C. Serum vascular endothelial growth factor is a predictor of invasion and metastasis in hepatocellular carcinoma. J. Exp. Clin. Cancer Res. 1999, 18, 511–517. [Google Scholar]
  240. Li, X.M.; Tang, Z.Y.; Zhou, G.; Lui, Y.K.; Ye, S.L. Significance of vascular endothelial growth factor mRNA expression in invasion and metastasis of hepatocellular carcinoma. J. Exp. Clin. Cancer Res. 1998, 17, 13–17. [Google Scholar]
  241. Wu, J.; Ru, N.Y.; Zhang, Y.; Li, Y.; Wei, D.; Ren, Z.; Huang, X.F.; Chen, Z.N.; Bian, H. HAb18G/CD147 promotes epithelial-mesenchymal transition through TGF-beta signaling and is transcriptionally regulated by Slug. Oncogene 2011, 30, 4410–4427. [Google Scholar] [CrossRef]
  242. Ke, X.; Li, L.; Dong, H.L.; Chen, Z.N. Acquisition of anoikis resistance through CD147 upregulation: A new mechanism underlying metastasis of hepatocellular carcinoma cells. Oncol. Lett. 2012, 3, 1249–1254. [Google Scholar]
  243. Ma, X.K.; Wang, L.; Li, Y.; Yang, X.M.; Zhao, P.; Tang, H.; Zhu, P.; Li, L.; Chen, Z.N. HAb18G/CD147 cell-cell contacts confer resistance of a HEK293 subpopulation to anoikis in an E-cadherin-dependent manner. BMC Cell Biol. 2010, 11, 27. [Google Scholar] [CrossRef]
  244. Yang, J.M.; O’Neill, P.; Jin, W.; Foty, R.; Medina, D.J.; Xu, Z.; Lomas, M.; Arndt, G.M.; Tang, Y.; Nakada, M.; et al. Extracellular matrix metalloproteinase inducer (CD147) confers resistance of breast cancer cells to Anoikis through inhibition of Bim. J. Biol. Chem. 2006, 281, 9719–9727. [Google Scholar] [CrossRef]
  245. Chang, Q.; Foltz, W.D.; Chaudary, N.; Hill, R.P.; Hedley, D.W. Tumor-stroma interaction in orthotopic primary pancreatic cancer xenografts during hedgehog pathway inhibition. Int. J. Cancer 2013, 133, 225–234. [Google Scholar] [CrossRef]
  246. Das, S.; Samant, R.S.; Shevde, L.A. The hedgehog pathway conditions the bone microenvironment for osteolytic metastasis of breast cancer. Int. J. Breast Cancer 2012, 2012, 298623. [Google Scholar]
  247. Chan, I.S.; Guy, C.D.; Chen, Y.; Lu, J.; Swiderska-Syn, M.; Michelotti, G.A.; Karaca, G.; Xie, G.; Kruger, L.; Syn, W.K.; et al. Paracrine Hedgehog signaling drives metabolic changes in hepatocellular carcinoma. Cancer Res. 2012, 72, 6344–6350. [Google Scholar] [CrossRef]
  248. Sicklick, J.K.; Li, Y.X.; Melhem, A.; Schmelzer, E.; Zdanowicz, M.; Huang, J.; Caballero, M.; Fair, J.H.; Ludlow, J.W.; McClelland, R.E.; et al. Hedgehog signaling maintains resident hepatic progenitors throughout life. Am. J. Physiol. Gastrointest. Liver Physiol. 2006, 290, G859–G870. [Google Scholar]
  249. Sicklick, J.K.; Li, Y.X.; Choi, S.S.; Qi, Y.; Chen, W.; Bustamante, M.; Huang, J.; Zdanowicz, M.; Camp, T.; Torbenson, M.S.; et al. Role for hedgehog signaling in hepatic stellate cell activation and viability. Lab. Investig. 2005, 85, 1368–1380. [Google Scholar] [CrossRef]
  250. Quan, H.; Zhou, F.; Nie, D.; Chen, Q.; Cai, X.; Shan, X.; Zhou, Z.; Chen, K.; Huang, A.; Li, S.; et al. Hepatitis C virus core protein epigenetically silences SFRP1 and enhances HCC aggressiveness by inducing epithelial-mesenchymal transition. Oncogene 2013. [Google Scholar] [CrossRef]
  251. Fox, J.G.; Feng, Y.; Theve, E.J.; Raczynski, A.R.; Fiala, J.L.; Doernte, A.L.; Williams, M.; McFaline, J.L.; Essigmann, J.M.; Schauer, D.B.; et al. Gut microbes define liver cancer risk in mice exposed to chemical and viral transgenic hepatocarcinogens. Gut 2010, 59, 88–97. [Google Scholar]
  252. Asare, G.A.; Mossanda, K.S.; Kew, M.C.; Paterson, A.C.; Kahler-Venter, C.P.; Siziba, K. Hepatocellular carcinoma caused by iron overload: A possible mechanism of direct hepatocarcinogenicity. Toxicology 2006, 219, 41–52. [Google Scholar]
  253. Mandishona, E.; MacPhail, A.P.; Gordeuk, V.R.; Kedda, M.A.; Paterson, A.C.; Rouault, T.A.; Kew, M.C. Dietary iron overload as a risk factor for hepatocellular carcinoma in Black Africans. Hepatology 1998, 27, 1563–1566. [Google Scholar] [CrossRef]
  254. Farrell, G.C.; Larter, C.Z. Nonalcoholic fatty liver disease: From steatosis to cirrhosis. Hepatology 2006, 43, S99–S112. [Google Scholar] [CrossRef]
  255. Sanyal, A.J.; Banas, C.; Sargeant, C.; Luketic, V.A.; Sterling, R.K.; Stravitz, R.T.; Shiffman, M.L.; Heuman, D.; Coterrell, A.; Fisher, R.A.; et al. Similarities and differences in outcomes of cirrhosis due to nonalcoholic steatohepatitis and hepatitis C. Hepatology 2006, 43, 682–689. [Google Scholar] [CrossRef]
  256. Duan, X.Y.; Zhang, L.; Fan, J.G.; Qiao, L. NAFLD leads to liver cancer: Do we have sufficient evidence? Cancer Lett. 2014, 345, 230–234. [Google Scholar] [CrossRef]
  257. Park, E.J.; Lee, J.H.; Yu, G.Y.; He, G.; Ali, S.R.; Holzer, R.G.; Osterreicher, C.H.; Takahashi, H.; Karin, M. Dietary and genetic obesity promote liver inflammation and tumorigenesis by enhancing IL-6 and TNF expression. Cell 2010, 140, 197–208. [Google Scholar] [CrossRef]
  258. Gruber, S.; Straub, B.K.; Ackermann, P.J.; Wunderlich, C.M.; Mauer, J.; Seeger, J.M.; Buning, H.; Heukamp, L.; Kashkar, H.; Schirmacher, P.; et al. Obesity promotes liver carcinogenesis via Mcl-1 stabilization independent of IL-6Ralpha signaling. Cell. Rep. 2013, 4, 669–680. [Google Scholar] [CrossRef]
  259. Mathur, A.; Franco, E.S.; Leone, J.P.; Osman-Mohamed, H.; Rojas, H.; Kemmer, N.; Neff, G.W.; Rosemurgy, A.S.; Alsina, A.E. Obesity portends increased morbidity and earlier recurrence following liver transplantation for hepatocellular carcinoma. HPB (Oxford) 2013, 15, 504–510. [Google Scholar] [CrossRef]
  260. Bravi, F.; Bosetti, C.; Tavani, A.; Bagnardi, V.; Gallus, S.; Negri, E.; Franceschi, S.; La Vecchia, C. Coffee drinking and hepatocellular carcinoma risk: A meta-analysis. Hepatology 2007, 46, 430–435. [Google Scholar] [CrossRef]
  261. Shimazu, T.; Tsubono, Y.; Kuriyama, S.; Ohmori, K.; Koizumi, Y.; Nishino, Y.; Shibuya, D.; Tsuji, I. Coffee consumption and the risk of primary liver cancer: Pooled analysis of two prospective studies in Japan. Int. J. Cancer 2005, 116, 150–154. [Google Scholar] [CrossRef]
  262. Fedirko, V.; Trichopolou, A.; Bamia, C.; Duarte-Salles, T.; Trepo, E.; Aleksandrova, K.; Nothlings, U.; Lukanova, A.; Lagiou, P.; Boffetta, P.; et al. Consumption of fish and meats and risk of hepatocellular carcinoma: The European Prospective Investigation into Cancer and Nutrition (EPIC). Ann. Oncol. 2013, 24, 2166–2173. [Google Scholar] [CrossRef]
  263. Turati, F.; Trichopoulos, D.; Polesel, J.; Bravi, F.; Rossi, M.; Talamini, R.; Franceschi, S.; Montella, M.; Trichopoulou, A.; La Vecchia, C.; et al. Mediterranean Diet and Hepatocellular Carcinoma. J. Hepatol. 2014, 60, 606–611. [Google Scholar] [CrossRef]
  264. Talamini, R.; Polesel, J.; Montella, M.; Dal Maso, L.; Crispo, A.; Tommasi, L.G.; Izzo, F.; Crovatto, M.; La Vecchia, C.; Franceschi, S. Food groups and risk of hepatocellular carcinoma: A multicenter case-control study in Italy. Int. J. Cancer 2006, 119, 2916–2921. [Google Scholar] [CrossRef]
  265. Loomba, R.; Yang, H.I.; Su, J.; Brenner, D.; Barrett-Connor, E.; Iloeje, U.; Chen, C.J. Synergism between obesity and alcohol in increasing the risk of hepatocellular carcinoma: A prospective cohort study. Am. J. Epidemiol. 2013, 177, 333–342. [Google Scholar] [CrossRef]
  266. Asare, G.A.; Bronz, M.; Naidoo, V.; Kew, M.C. Synergistic interaction between excess hepatic iron and alcohol ingestion in hepatic mutagenesis. Toxicology 2008, 254, 11–18. [Google Scholar] [CrossRef]
  267. Hwang, S.J.; Lee, S.D. Hepatic steatosis and hepatitis C: Still unhappy bedfellows? J. Gastroenterol. Hepatol. 2011, 26, 96–101. [Google Scholar] [CrossRef]
  268. Davila, J.A.; Morgan, R.O.; Shaib, Y.; McGlynn, K.A.; El-Serag, H.B. Diabetes increases the risk of hepatocellular carcinoma in the United States: A population based case control study. Gut 2005, 54, 533–539. [Google Scholar] [CrossRef]
  269. Trichopoulos, D.; Bamia, C.; Lagiou, P.; Fedirko, V.; Trepo, E.; Jenab, M.; Pischon, T.; Nothlings, U.; Overved, K.; Tjonneland, A.; et al. Hepatocellular carcinoma risk factors and disease burden in a European cohort: A nested case-control study. J. Natl. Cancer Inst. 2011, 103, 1686–1695. [Google Scholar] [CrossRef]
  270. Kita, Y.; Mizukoshi, E.; Takamura, T.; Sakurai, M.; Takata, Y.; Arai, K.; Yamashita, T.; Nakamoto, Y.; Kaneko, S. Impact of diabetes mellitus on prognosis of patients infected with hepatitis C virus. Metab.: Clin. Exp. 2007, 56, 1682–1688. [Google Scholar] [CrossRef]
  271. Ma, Y.Y.; Li, L.; Yu, C.H.; Shen, Z.; Chen, L.H.; Li, Y.M. Effects of probiotics on nonalcoholic fatty liver disease: A meta-analysis. World J. Gastroenterol. 2013, 19, 6911–6918. [Google Scholar] [CrossRef]
  272. Le Roy, T.; Llopis, M.; Lepage, P.; Bruneau, A.; Rabot, S.; Bevilacqua, C.; Martin, P.; Philippe, C.; Walker, F.; Bado, A.; et al. Intestinal microbiota determines development of non-alcoholic fatty liver disease in mice. Gut 2013, 62, 1787–1794. [Google Scholar] [CrossRef]
  273. Son, G.; Kremer, M.; Hines, I.N. Contribution of gut bacteria to liver pathobiology. Gastroenterol. Res. Pract. 2010, 2010. [Google Scholar] [CrossRef]
  274. Wiest, R.; Garcia-Tsao, G. Bacterial translocation (BT) in cirrhosis. Hepatology 2005, 41, 422–433. [Google Scholar] [CrossRef]
  275. Abu Al-Soud, W.; Stenram, U.; Ljungh, A.; Tranberg, K.G.; Nilsson, H.O.; Wadstrom, T. DNA of Helicobacter spp. and common gut bacteria in primary liver carcinoma. Dig. Liver Dis. 2008, 40, 126–131. [Google Scholar] [CrossRef]
  276. Xuan, S.Y.; Li, N.; Qiang, X.; Zhou, R.R.; Shi, Y.X.; Jiang, W.J. Helicobacter infection in hepatocellular carcinoma tissue. World J. Gastroenterol. 2006, 12, 2335–2340. [Google Scholar]
  277. Zhao, H.Y.; Wang, H.J.; Lu, Z.; Xu, S.Z. Intestinal microflora in patients with liver cirrhosis. Chin. J. Dig. Dis. 2004, 5, 64–67. [Google Scholar] [CrossRef]
  278. Rocha, M.; Avenaud, P.; Menard, A.; Le Bail, B.; Balabaud, C.; Bioulac-Sage, P.; de Magalhaes Queiroz, D.M.; Megraud, F. Association of Helicobacter species with hepatitis C cirrhosis with or without hepatocellular carcinoma. Gut 2005, 54, 396–401. [Google Scholar]
  279. Shackel, N.A.; Vadas, M.A.; Gamble, J.R.; McCaughan, G.W. Beyond liver fibrosis: Hepatic stellate cell senescence links obesity to liver cancer via the microbiome. Hepatology 2014. [Google Scholar] [CrossRef]
  280. Taylor, D.D.; Gercel-Taylor, C. Exosomes/microvesicles: Mediators of cancer-associated immunosuppressive microenvironments. Seminars Immunopathol. 2011, 33, 441–454. [Google Scholar] [CrossRef]
  281. Yang, C.; Robbins, P.D. The roles of tumor-derived exosomes in cancer pathogenesis. Clin. Dev. Immunol. 2011, 2011, 842849. [Google Scholar]
  282. Navabi, H.; Croston, D.; Hobot, J.; Clayton, A.; Zitvogel, L.; Jasani, B.; Bailey-Wood, R.; Wilson, K.; Tabi, Z.; Mason, M.D.; et al. Preparation of human ovarian cancer ascites-derived exosomes for a clinical trial. Blood Cells Mol. Dis. 2005, 35, 149–152. [Google Scholar] [CrossRef]
  283. Dai, S.; Wei, D.; Wu, Z.; Zhou, X.; Wei, X.; Huang, H.; Li, G. Phase I clinical trial of autologous ascites-derived exosomes combined with GM-CSF for colorectal cancer. Mol. Ther. 2008, 16, 782–790. [Google Scholar] [CrossRef]
  284. Ristorcelli, E.; Beraud, E.; Verrando, P.; Villard, C.; Lafitte, D.; Sbarra, V.; Lombardo, D.; Verine, A. Human tumor nanoparticles induce apoptosis of pancreatic cancer cells. FASEB J. 2008, 22, 3358–3369. [Google Scholar] [CrossRef]
  285. Lv, L.H.; Wan, Y.L.; Lin, Y.; Zhang, W.; Yang, M.; Li, G.L.; Lin, H.M.; Shang, C.Z.; Chen, Y.J.; Min, J. Anticancer drugs cause release of exosomes with heat shock proteins from human hepatocellular carcinoma cells that elicit effective natural killer cell antitumor responses in vitro. J. Biol. Chem. 2012, 287, 15874–15885. [Google Scholar] [CrossRef]
  286. Gesierich, S.; Berezovskiy, I.; Ryschich, E.; Zoller, M. Systemic induction of the angiogenesis switch by the tetraspanin D6.1A/CO-029. Cancer Res. 2006, 66, 7083–7094. [Google Scholar] [CrossRef]
  287. Nazarenko, I.; Rana, S.; Baumann, A.; McAlear, J.; Hellwig, A.; Trendelenburg, M.; Lochnit, G.; Preissner, K.T.; Zoller, M. Cell surface tetraspanin Tspan8 contributes to molecular pathways of exosome-induced endothelial cell activation. Cancer Res. 2010, 70, 1668–1678. [Google Scholar] [CrossRef]
  288. Zhang, W.; Zhao, P.; Xu, X.L.; Cai, L.; Song, Z.S.; Cao, D.Y.; Tao, K.S.; Zhou, W.P.; Chen, Z.N.; Dou, K.F. Annexin A2 promotes the migration and invasion of human hepatocellular carcinoma cells in vitro by regulating the shedding of CD147-harboring microvesicles from tumor cells. PLoS One 2013, 8, e67268. [Google Scholar]
  289. Fonsato, V.; Collino, F.; Herrera, M.B.; Cavallari, C.; Deregibus, M.C.; Cisterna, B.; Bruno, S.; Romagnoli, R.; Salizzoni, M.; Tetta, C.; et al. Human liver stem cell-derived microvesicles inhibit hepatoma growth in SCID mice by delivering antitumor microRNAs. Stem Cells 2012, 30, 1985–1998. [Google Scholar] [CrossRef]
  290. Kogure, T.; Lin, W.L.; Yan, I.K.; Braconi, C.; Patel, T. Intercellular nanovesicle-mediated microRNA transfer: A mechanism of environmental modulation of hepatocellular cancer cell growth. Hepatology 2011, 54, 1237–1248. [Google Scholar]
  291. Chang, M.H.; Chen, C.J.; Lai, M.S.; Hsu, H.M.; Wu, T.C.; Kong, M.S.; Liang, D.C.; Shau, W.Y.; Chen, D.S. Universal hepatitis B vaccination in Taiwan and the incidence of hepatocellular carcinoma in children. Taiwan Childhood Hepatoma Study Group. N. Engl. J. Med. 1997, 336, 1855–1859. [Google Scholar] [CrossRef]
  292. Chang, M.H.; Chen, T.H.; Hsu, H.M.; Wu, T.C.; Kong, M.S.; Liang, D.C.; Ni, Y.H.; Chen, C.J.; Chen, D.S. Prevention of hepatocellular carcinoma by universal vaccination against hepatitis B virus: The effect and problems. Clin. Cancer Res. 2005, 11, 7953–7957. [Google Scholar] [CrossRef]
  293. Wu, J.C.; Huang, Y.H.; Chau, G.Y.; Su, C.W.; Lai, C.R.; Lee, P.C.; Huo, T.I.; Sheen, I.J.; Lee, S.D.; Lui, W.Y. Risk factors for early and late recurrence in hepatitis B-related hepatocellular carcinoma. J. Hepatol. 2009, 51, 890–897. [Google Scholar] [CrossRef]
  294. Hoshida, Y. Risk of recurrence in hepatitis B-related hepatocellular carcinoma: Impact of viral load in late recurrence. J. Hepatol. 2009, 51, 842–844. [Google Scholar] [CrossRef]
  295. Du, Y.; Su, T.; Ding, Y.; Cao, G. Effects of antiviral therapy on the recurrence of hepatocellular carcinoma after curative resection or liver transplantation. Hepat. Mon. 2012, 12, e6031. [Google Scholar]
  296. Wu, C.; Chen, Y.; Ho, H.J.; Hsu, Y.C.; Kuo, K.N.; Wu, M.S.; Lin, J.T. Association between nucleoside analogues and risk of hepatitis b virus-related hepatocellular carcinoma recurrence following liver resection. J. Am. Med. Assoc. 2012, 308, 1906–1913. [Google Scholar]
  297. Ikeda, K.; Arase, Y.; Saitoh, S.; Kobayashi, M.; Suzuki, Y.; Suzuki, F.; Tsubota, A.; Chayama, K.; Murashima, N.; Kumada, H. Interferon beta prevents recurrence of hepatocellular carcinoma after complete resection or ablation of the primary tumor-A prospective randomized study of hepatitis C virus-related liver cancer. Hepatology 2000, 32, 228–232. [Google Scholar]
  298. Hung, C.H.; Lee, C.M.; Wang, J.H.; Tung, H.D.; Chen, C.H.; Lu, S.N. Antiviral therapy after non-surgical tumor ablation in patients with hepatocellular carcinoma associated with hepatitis C virus. J. Gastroenterol. Hepatol. 2005, 20, 1553–1559. [Google Scholar] [CrossRef]
  299. Chen, C.J.; Yang, H.I.; Iloeje, U.H. Hepatitis B virus DNA levels and outcomes in chronic hepatitis B. Hepatology 2009, 49, S72–S84. [Google Scholar] [CrossRef]
  300. Chan, H.L.; Wong, V.W.; Wong, G.L.; Chim, A.M.; Lai, L.H.; Sung, J.J. Evaluation of impact of serial hepatitis B virus DNA levels on development of hepatocellular carcinoma. J. Clin. Microbiol. 2009, 47, 1830–1836. [Google Scholar] [CrossRef]
  301. Lai, M.; Hyatt, B.J.; Nasser, I.; Curry, M.; Afdhal, N.H. The clinical significance of persistently normal ALT in chronic hepatitis B infection. J. Hepatol. 2007, 47, 760–767. [Google Scholar] [CrossRef]
  302. Tsang, P.S.; Trinh, H.; Garcia, R.T.; Phan, J.T.; Ha, N.B.; Nguyen, H.; Nguyen, K.; Keeffe, E.B.; Nguyen, M.H. Significant prevalence of histologic disease in patients with chronic hepatitis B and mildly elevated serum alanine aminotransferase levels. Clin. Gastroenterol. Hepatol. 2008, 6, 569–574. [Google Scholar] [CrossRef]
  303. Wang, C.C.; Lim, L.Y.; Deubner, H.; Tapia, K.; Lau, A.W.; Manansala, J.; Krows, M.; Shuhart, M.C.; Kowdley, K.V. Factors predictive of significant hepatic fibrosis in adults with chronic hepatitis B and normal serum ALT. J. Clin. Gastroenterol. 2008, 42, 820–826. [Google Scholar]
  304. Sullivan, R.; Graham, C.H. Hypoxia-driven selection of the metastatic phenotype. Cancer Metastasis Rev. 2007, 26, 319–331. [Google Scholar] [CrossRef]
  305. Bennewith, K.L.; Dedhar, S. Targeting hypoxic tumour cells to overcome metastasis. BMC Cancer 2011, 11, 504. [Google Scholar] [CrossRef]
  306. Hong, F.; Chou, H.; Fiel, M.I.; Friedman, S.L. Antifibrotic activity of sorafenib in experimental hepatic fibrosis: Refinement of inhibitory targets, dosing, and window of efficacy in vivo. Dig. Dis. Sci. 2013, 58, 257–264. [Google Scholar]
  307. Zhang, D.W.; Zhao, Y.X.; Wei, D.; Li, Y.L.; Zhang, Y.; Wu, J.; Xu, J.; Chen, C.; Tang, H.; Zhang, W.; et al. HAb18G/CD147 promotes activation of hepatic stellate cells and is a target for antibody therapy of liver fibrosis. J. Hepatol. 2012, 57, 1283–1291. [Google Scholar] [CrossRef]
  308. Dai, D.; Xu, W.; Liu, J.; Zhu, L.; Zhu, X.; Ma, X. Safety and efficacy of a peripheral intravenous bolus of Licartin for the treatment of advanced hepatocellular carcinoma. Exp. Ther. Med. 2013, 6, 1417–1422. [Google Scholar]
  309. Xu, J.; Shen, Z.Y.; Chen, X.G.; Zhang, Q.; Bian, H.J.; Zhu, P.; Xu, H.Y.; Song, F.; Yang, X.M.; Mi, L.; et al. A randomized controlled trial of Licartin for preventing hepatoma recurrence after liver transplantation. Hepatology 2007, 45, 269–276. [Google Scholar] [CrossRef]
  310. Pardee, A.D.; Butterfield, L.H. Immunotherapy of hepatocellular carcinoma: Unique challenges and clinical opportunities. Oncoimmunology 2012, 1, 48–55. [Google Scholar] [CrossRef]
  311. Schmidt, N.; Neumann-Haefelin, C.; Thimme, R. Cellular immune responses to hepatocellular carcinoma: Lessons for immunotherapy. Dig. Dis. 2012, 30, 483–491. [Google Scholar] [CrossRef]
  312. Zhang, W.; Liu, J.; Wu, Y.; Xiao, F.; Wang, Y.; Wang, R.; Yang, H.; Wang, G.; Yang, J.; Deng, H.; et al. Immunotherapy of hepatocellular carcinoma with a vaccine based on xenogeneic homologous alpha fetoprotein in mice. Biochem. Biophys. Res. Commun. 2008, 376, 10–14. [Google Scholar] [CrossRef]
  313. Palmer, D.H.; Midgley, R.S.; Mirza, N.; Torr, E.E.; Ahmed, F.; Steele, J.C.; Steven, N.M.; Kerr, D.J.; Young, L.S.; Adams, D.H. A phase II study of adoptive immunotherapy using dendritic cells pulsed with tumor lysate in patients with hepatocellular carcinoma. Hepatology 2009, 49, 124–132. [Google Scholar] [CrossRef]
  314. Tada, F.; Abe, M.; Hirooka, M.; Ikeda, Y.; Hiasa, Y.; Lee, Y.; Jung, N.C.; Lee, W.B.; Lee, H.S.; Bae, Y.S.; et al. Phase I/II study of immunotherapy using tumor antigen-pulsed dendritic cells in patients with hepatocellular carcinoma. Int. J. Oncol. 2012, 41, 1601–1609. [Google Scholar]
  315. Takayama, T.; Sekine, T.; Makuuchi, M.; Yamasaki, S.; Kosuge, T.; Yamamoto, J.; Shimada, K.; Sakamoto, M.; Hirohashi, S.; Ohashi, Y.; et al. Adoptive immunotherapy to lower postsurgical recurrence rates of hepatocellular carcinoma: A randomised trial. Lancet 2000, 356, 802–807. [Google Scholar] [CrossRef]
  316. Greten, T.F.; Ormandy, L.A.; Fikuart, A.; Hochst, B.; Henschen, S.; Horning, M.; Manns, M.P.; Korangy, F. Low-dose cyclophosphamide treatment impairs regulatory T cells and unmasks AFP-specific CD4+ T-cell responses in patients with advanced HCC. J. Immunother. 2010, 33, 211–218. [Google Scholar] [CrossRef]

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MDPI and ACS Style

Tu, T.; Budzinska, M.A.; Maczurek, A.E.; Cheng, R.; Di Bartolomeo, A.; Warner, F.J.; McCaughan, G.W.; McLennan, S.V.; Shackel, N.A. Novel Aspects of the Liver Microenvironment in Hepatocellular Carcinoma Pathogenesis and Development. Int. J. Mol. Sci. 2014, 15, 9422-9458. https://0-doi-org.brum.beds.ac.uk/10.3390/ijms15069422

AMA Style

Tu T, Budzinska MA, Maczurek AE, Cheng R, Di Bartolomeo A, Warner FJ, McCaughan GW, McLennan SV, Shackel NA. Novel Aspects of the Liver Microenvironment in Hepatocellular Carcinoma Pathogenesis and Development. International Journal of Molecular Sciences. 2014; 15(6):9422-9458. https://0-doi-org.brum.beds.ac.uk/10.3390/ijms15069422

Chicago/Turabian Style

Tu, Thomas, Magdalena A. Budzinska, Annette E. Maczurek, Robert Cheng, Anna Di Bartolomeo, Fiona J. Warner, Geoffrey W. McCaughan, Susan V. McLennan, and Nicholas A. Shackel. 2014. "Novel Aspects of the Liver Microenvironment in Hepatocellular Carcinoma Pathogenesis and Development" International Journal of Molecular Sciences 15, no. 6: 9422-9458. https://0-doi-org.brum.beds.ac.uk/10.3390/ijms15069422

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