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

The genetic and epigenetic alterations in human hepatocellular carcinoma: a recent update

Hepatocellular carcinoma (HCC) is one of the most frequent human malignancies worldwide with very poor prognosis. It is generally accepted that the progression of HCC is a long-term process with accumulation of multiple genetic and epigenetic alterations, which further lead to the activation of critical oncogenes or inactivation of tumor suppressor genes. HCC is characterized with multiple cancer hallmarks including their ability to proliferate, anti-apoptosis, invade, metastasis, as well as the emerging features such as stem cell properties and energy metabolic switch. The irreversible alterations at genetic level could be detected as early as in the pre-neoplastic stages and accumulate during cancer progression. Thus, they might account for the cancer initiating steps and further malignant transformation. In addition to genetic alterations, epigenetic alterations can affect the cancer transcriptome more extensively. Alterations in DNA methylation, histone modification, miRNAs, RNA editing, and lncRNAs might result in disrupted gene regulation networks and substantially contribute to HCC progression. In this review, the genetic and epigenetic alterations which significantly contribute to the malignant capabilities of HCC will be updated and summarized in detail. Further characterization of those critical molecular events might better elucidate the pathogenesis of HCC and provide novel therapeutic targets for treatment of this deadly disease.

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

BACKGROUND

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

RESULTS

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

CONCLUSIONS

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

Human and mouse VEGFA-amplified hepatocellular carcinomas are highly sensitive to sorafenib treatment

Death rates from hepatocellular carcinoma (HCC) are steadily increasing, yet therapeutic options for advanced HCC are limited. We identify a subset of mouse and human HCCs harboring VEGFA genomic amplification, displaying distinct biologic characteristics. Unlike common tumor amplifications, this one seems to work via heterotypic paracrine interactions; stromal VEGF receptors (VEGFR), responding to tumor VEGF-A, produce hepatocyte growth factor (HGF) that reciprocally affects tumor cells. VEGF-A inhibition results in HGF downregulation and reduced proliferation, specifically in amplicon-positive mouse HCCs. Sorafenib-the first-line drug in advanced HCC-targets multiple kinases, including VEGFRs, but has only an overall mild beneficial effect. We found that VEGFA amplification specifies mouse and human HCCs that are distinctly sensitive to sorafenib. FISH analysis of a retrospective patient cohort showed markedly improved survival of sorafenib-treated patients with VEGFA-amplified HCCs, suggesting that VEGFA amplification is a potential biomarker for HCC response to VEGF-A-blocking drugs.

SIGNIFICANCE

Using a mouse model of inflammation-driven cancer, we identified a subclass of HCC carrying VEGFA amplification, which is particularly sensitive to VEGF-A inhibition. We found that a similar amplification in human HCC identifies patients who favorably responded to sorafenib-the first-line treatment of advanced HCC-which has an overall moderate therapeutic efficacy.

Stellate cells and the development of liver cancer: therapeutic potential of targeting the stroma

Hepatocellular carcinoma (HCC) and intrahepatic cholangiocarcinoma (ICC) are the most common types of primary tumors in the liver. Although major advances have been made in understanding the cellular and molecular mechanisms underlying liver carcinogenesis, HCC and ICC are still deadly cancers worldwide waiting for innovative therapeutic options. Growing evidence from the literature highlight the critical role of the tumor cell microenvironment in the pathogenesis of cancer diseases. Thus, targeting the microenvironment, particularly the crosstalk between tumor cells and stromal cells, has emerged as a promising therapeutic strategy. This strategy would be particularly relevant for liver cancers which frequently develop in a setting of chronic inflammation and microenvironment remodeling associated with hepatic fibrosis and cirrhosis, such processes in which hepatic stellate cells (HSC) greatly contribute. This review brings a genomic point of view on the alterations of the cellular microenvironment in liver cancers, particularly the stromal tissue within tumor nodules, emphasizing the importance of the crosstalk between tumor cells and stromal cells, notably activated HSC, in tumor onset and progression. Furthermore, potential therapeutic modalities of targeting the stroma and HSC are discussed.

Involvement of extracellular vesicle long noncoding RNA (linc-VLDLR) in tumor cell responses to chemotherapy

Hepatocellular cancer (HCC) is a highly treatment-refractory cancer and is also highly resistant to adverse cellular stress. Although cell behavior can be modulated by noncoding RNAs (ncRNA) within extracellular vesicles (EV), the contributions of long noncoding RNAs (lncRNAs) are largely unknown. To this end, the involvement and functional roles of lncRNAs contained within EVs during chemotherapeutic stress in human HCC were determined. Expression profiling identified a subset of lncRNAs that were enriched in tumor cell-derived vesicles released from two different cell lines. Of these, lincRNA-VLDLR (linc-VLDLR) was significantly upregulated in malignant hepatocytes. Exposure of HCC cells to diverse anticancer agents such as sorafenib, camptothecin, and doxorubicin increased linc-VLDLR expression in cells as well as within EVs released from these cells. Incubation with EVs reduced chemotherapy-induced cell death and also increased linc-VLDLR expression in recipient cells. RNAi-mediated knockdown of linc-VLDLR decreased cell viability and abrogated cell-cycle progression. Moreover, knockdown of VLDLR reduced expression of ABCG2 (ATP-binding cassette, subfamily G member 2), whereas overexpression of this protein reduced the effects of VLDLR knockdown on sorafenib-induced cell death. Here, linc-VLDLR is identified as an EV-enriched lncRNA that contributes to cellular stress responses.

IMPLICATIONS

These findings provide new insight into the role of EVs and demonstrate the capacity of lncRNAs to mediate chemotherapeutic stress response in HCC.

Novel aspects of the liver microenvironment in hepatocellular carcinoma pathogenesis and development

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.

The potential contributions of a Y-located protooncogene and its X homologue in sexual dimorphisms in hepatocellular carcinoma

There is a significant sex disparity favoring males among hepatocellular carcinoma (HCC) patients. Although various risk factors have been identified, the exact etiology of such sexual dimorphism(s) in HCC is uncertain. Previous studies showed that overexpression of the Y-located protooncogene, testis-specific protein Y encoded (TSPY), promotes cell proliferation and oncogenesis whereas its X-located homologue, TSPYhomologue X (TSPX), retards cell cycle and oncogenic progression. Furthermore, TSPX promotes proteasomal degradation of hepatitis B virus-encoded X oncoprotein and hence could serve as a tumor suppressor in virus-associated HCC. Using immunohistochemistry and reverse-transcription polymerase chain reaction analysis, we had examined the expression of TSPY and TSPX with reference to other established biomarkers in HCC and related liver cancers. Our results demonstrated that 55 (19.2%) of 287 male cases were TSPY positive in immunohistochemistry of tissue arrays, and 15 (46.9%) of 32 male cases were TSPY positive in reverse-transcription polymerase chain reaction analysis of clinical samples. TSPY expression was closely associated with the expression of HCC biomarkers, such as glypican 3. In contrast, TSPX expression was down-regulated in 54.5% of total tumor/nontumorous paired samples (18/33) and negatively associated with those of TSPY, glypican 3, and forkhead box M1 (FOXM1) and was positively associated with that of a tumor suppressor, insulin-like growth factor binding protein 3. The present findings support the hypothesis that the oncogenic events leading to an ectopic activation of the Y-located protooncogene TSPY and/or inactivating mutation/epigenetic silencing of the X-located tumor suppressor gene TSPX could collectively contribute to the sexual dimorphism(s) in HCC and related liver cancers in male-biased manners.

Extracellular vesicle-mediated transfer of long non-coding RNA ROR modulates chemosensitivity in human hepatocellular cancer

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Selected long non-coding RNA are aberrantly expressed in hepatocellular cancers.

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linc-ROR is a highly upregulated lncRNA that is expressed in response to TGFβ.

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linc-ROR contributes to chemoresistance of HCC cells.

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Intercellular transfer of linc-ROR occurs within extracellular vesicles.

Hepatocellular cancers (HCC) are highly resistant to chemotherapy. TGFβ has been associated with chemoresistance in some human cancers but the mechanisms involved are unknown. We explored how TGFβ might contribute to altered responses to therapy by assessing the involvement and mechanistic contribution of extracellular vesicle long non-coding RNA (lncRNA) in mediating TGFβ-dependent chemoresistance. TGFβ reduced the sensitivity of HCC cells to sorafenib or doxorubicin and altered the release of both extracellular vesicles and of selected lncRNA within these vesicles. Amongst these, lincRNA-ROR (linc-ROR), a stress-responsive lncRNA was highly expressed in HCC cells and enriched within extracellular vesicles derived from tumor cells. Incubation with HCC-derived extracellular vesicles increased linc-ROR expression and reduced chemotherapy-induced cell death in recipient cells. Sorafenib increased linc-ROR expression in both tumor cells and extracellular vesicles, whereas siRNA to linc-ROR increased chemotherapy-induced apoptosis and cytotoxicity. Tumor-initiating cells that express CD133 have an increased resistance to therapy. TGFβ increased expression of CD133+ cells and colony growth in limiting dilution assays, both of which were attenuated by linc-ROR knockdown. These data provide mechanistic insights into primary chemoresistance in HCC by showing that: (a) TGFβ selectively enriches linc-RoR within extracellular vesicles, which has a potential role in intercellular signaling in response to TGFβ; (b) expression and enrichment of linc-ROR during chemotherapeutic stress plays a functional role in chemoresistance; and (c) the effects of TGFβ on chemoresistance in HCC may involve linc-RoR-dependent effects on tumor-initiating cells. These findings implicate extracellular vesicle lncRNA as mediators of the chemotherapeutic response, and support targeting linc-ROR to enhance chemosensitivity in HCC.

Role of the tissue microenvironment as a therapeutic target in hepatocellular carcinoma

Hepatocellular carcinoma is difficult to treat, primarily because the underlying molecular mechanisms driving clinical outcome are still poorly understood. Growing evidence suggests that the tissue microenvironment has a role in the biological behavior of the tumor. The main clinical issue is to identify the best target for therapeutic approaches. Here, we discuss the hypothesis that the entire tissue microenvironment might be considered as a biological target. However, the tissue microenvironment consists of several cellular and biochemical components, each of which displays a distinct biological activity. We discuss the major components of this environment and consider how they may interact to promote tumor/host crosstalk.

Differential effects of sorafenib on liver versus tumor fibrosis mediated by stromal-derived factor 1 alpha/C-X-C receptor type 4 axis and myeloid differentiation antigen-positive myeloid cell infiltration in mice

Sorafenib--a broad kinase inhibitor--is a standard therapy for advanced hepatocellular carcinoma (HCC) and has been shown to exert antifibrotic effects in liver cirrhosis, a precursor of HCC. However, the effects of sorafenib on tumor desmoplasia--and its consequences on treatment resistance--remain unknown. We demonstrate that sorafenib has differential effects on tumor fibrosis versus liver fibrosis in orthotopic models of HCC in mice. Sorafenib intensifies tumor hypoxia, which increases stromal-derived factor 1 alpha (SDF-1α) expression in cancer and stromal cells and, subsequently, myeloid differentiation antigen-positive (Gr-1(+)) myeloid cell infiltration. The SDF-1α/C-X-C receptor type 4 (CXCR4) pathway directly promotes hepatic stellate cell (HSC) differentiation and activation through the mitogen-activated protein kinase pathway. This is consistent with the association between SDF-1α expression with fibrotic septa in cirrhotic liver tissues as well as with desmoplastic regions of human HCC samples. We demonstrate that after treatment with sorafenib, SDF-1α increased the survival of HSCs and their alpha-smooth muscle actin and collagen I expression, thus increasing tumor fibrosis. Finally, we show that Gr-1(+) myeloid cells mediate HSC differentiation and activation in a paracrine manner. CXCR4 inhibition, using AMD3100 in combination with sorafenib treatment, prevents the increase in tumor fibrosis--despite persistently elevated hypoxia--in part by reducing Gr-1(+) myeloid cell infiltration and inhibits HCC growth. Similarly, antibody blockade of Gr-1 reduces tumor fibrosis and inhibits HCC growth when combined with sorafenib treatment.

CONCLUSION

Blocking SDF-1α/CXCR4 or Gr-1(+) myeloid cell infiltration may reduce hypoxia-mediated HCC desmoplasia and increase the efficacy of sorafenib treatment.

Synergistic inhibition of HCC and liver cancer stem cell proliferation by targeting RAS/RAF/MAPK and WNT/β-catenin pathways

BACKGROUND/AIM

The aim of this study is to find synergistic effect using FH535 and sorafenib by targeting the RAS/RAF/MAPK and WNT/β-catenin pathways.

MATERIALS AND METHODS

3H-Thymidine incorporation assays were performed to address Huh7 and liver cancer stem cell (LCSC) inhibition using FH535 and sorafenib, alone and in combination. Calcusyn analysis was used to calculate the combination index (CI). A western blot assay was performed to check for potential targets.

RESULTS

FH535 and sorafenib caused inhibition of Huh7 and LCSC. Combination therapy was significantly better than monotherapy in inhibition of HuH7. Combination with sorafenib and FH535 was found to be synergistic in inhibition of LCSC with a CI of less than 1. The western blot assay demonstrated enhanced cleaved poly (ADP-ribose) polymerase (PARP) and inhibition of cyclin D1, B-cell lymphoma 2 (Bcl2), survivin and cellular myelocytomatosis oncogene (c-MYC).

CONCLUSION

FH535 and sorafenib combination produced synergistic effect on inhibition of HCC and LCSC. Our study demonstrated that FH535 can induce apoptosis in these two different hepatocellular carcinoma (HCC) cell lines.

Immunodominance and functional alterations of tumor-associated antigen-specific CD8+ T-cell responses in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the fifth most common malignancy worldwide with a poor prognosis and limited therapeutic options. To aid the development of novel immunological interventions, we studied the breadth, frequency, and tumor-infiltration of naturally occurring CD8(+) T-cell responses targeting several tumor-associated antigens (TAA). We used overlapping peptides spanning the entire alpha-fetoprotein (AFP), glypican-3 (GPC-3), melanoma-associated gene-A1 (MAGE-A1) and New York-esophageal squamous cell carcinoma-1 (NY-ESO-1) proteins and major-histocompatibility-complex-class-I-tetramers specific for epitopes of MAGE-A1 and NY-ESO-1 to analyze TAA-specific CD8(+) T-cell responses in a large cohort of HCC patients. After nonspecific expansion in vitro, we detected interferon-γ (IFN-γ)-producing CD8(+) T cells specific for all four TAA in the periphery as well as in liver and tumor tissue. These CD8(+) T-cell responses displayed clear immunodominance patterns within each TAA, but no consistent hierarchy was observed between different TAA. Importantly, the response breadth was highest in early-stage HCC and associated with patient survival. After antigen-specific expansion, TAA-specific CD8(+) T cells were detectable by tetramer staining but impaired in their ability to produce IFN-γ. Furthermore, regulatory T cells (Treg) were increased in HCC lesions. Depletion of Treg from cultures improved TAA-specific CD8(+) T-cell proliferation but did not restore IFN-γ-production.

CONCLUSION

Naturally occurring TAA-specific CD8(+) T-cell responses are present in patients with HCC and therefore constitute part of the normal T-cell repertoire. Moreover, the presence of these responses correlates with patient survival. However, the observation of impaired IFN-γ production suggests that the efficacy of such responses is functionally limited. These findings support the development of strategies that aim to enhance the total TAA-specific CD8(+) T-cell response by therapeutic boosting and/or specificity diversification. However, further research will be required to help unlock the full potential of TAA-specific CD8(+) T-cell responses.

TGF-β Mediated Crosstalk Between Malignant Hepatocyte and Tumor Microenvironment in Hepatocellular Carcinoma

In this article, we have reviewed current literature regarding the regulation of hepatocellular carcinoma (HCC) by the interaction of malignant hepatocytes and their tissue environment through cytokine signaling, here represented by transforming growth factor-beta (TGF-β) signaling. We have discussed responses of TGF-β signaling in transition of hepatic stellate cells to myofibroblasts (MFBs), recruitment of tumor-associated macrophages (TAMs), and enrichment of tumor-associated endothelial cells (TECs). The malignant hepatocytes also secrete various factors such as platelet-derived growth factors (PDGFs), vascular endothelial growth factor (VEGF), and TGF-β. TGF-β, a super-family of cytokines, creates tumor microenvironment by interacting through other growth factors (epidermal growth factor receptor (EGFR), PDGF, fibroblast growth factor (FGF), hepatocyte growth factor (HGF), VEGF), cytokines and chemokines, and extracellular matrix (ECM) remodeling. Hence, the HCC tumor microenvironment may now be recognized as an important participant of tumor progression to act as potential target to systemic therapies compared to targeted therapies.

Macro- and micro-environmental factors in clinical hepatocellular cancer

We previously developed a network phenotyping strategy (NPS), a graph theory-based transformation of clinical practice data, for recognition of two primary subgroups of hepatocellular cancer (HCC), called S and L, which differed significantly in their tumor masses. In the current study, we have independently validated this result on 641 HCC patients from another continent. We identified the same HCC subgroups with mean tumor masses 9 cm x n (S) and 22 cm x n (L), P<10(-14). The means of survival distribution (not available previously) for this new cohort were also significantly different (S was 12 months, L was 7 months, P<10(-5)). We characterized nine unique reference patterns of interactions between tumor and clinical environment factors, identifying four subtypes for S and five subtypes for L phenotypes, respectively. In L phenotype, all reference patterns were portal vein thrombosis (PVT)-positive, all platelet/alpha fetoprotein (AFP) levels were high, and all were chronic alcohol consumers. L had phenotype landmarks with worst survival. S phenotype interaction patterns were PVT-negative, with low platelet/AFP levels. We demonstrated that tumor-clinical environment interaction patterns explained how a given parameter level can have a different significance within a different overall context. Thus, baseline bilirubin is low in S1 and S4, but high in S2 and S3, yet all are S subtype patterns, with better prognosis than in L. Gender and age, representing macro-environmental factors, and bilirubin, prothrombin time, and AST levels representing micro-environmental factors, had a major impact on subtype characterization. Clinically important HCC phenotypes are therefore represented by complete parameter relationship patterns and cannot be replaced by individual parameter levels.

Association of abnormal plasma bilirubin with aggressive hepatocellular carcinoma phenotype

Cirrhosis-related abnormal liver function is associated with predisposition to hepatocellular carcinoma (HCC). It features in several HCC classification systems and is an HCC prognostic factor. The aim of the present study was to examine the phenotypic tumor differences in HCC patients with normal or abnormal plasma bilirubin levels. A 2,416-patient HCC cohort was studied and dichotomized into normal and abnormal plasma bilirubin groups. Their HCC characteristics were compared for tumor aggressiveness features, namely, blood alpha-fetoprotein (AFP) levels, tumor size, presence of portal vein thrombosis (PVT) and tumor multifocality. In the total cohort, elevated bilirubin levels were associated with higher AFP levels, increased PVT and multifocality, and lower survival, despite similar tumor sizes. When different tumor size terciles were compared, similar results were found, even among patients with small tumors. A multiple logistic regression model for PVT or tumor multifocality showed increased odds ratios for elevated levels of gamma glutamyl transpeptidase (GGTP), bilirubin, and AFP and for larger tumor sizes. We conclude that HCC patients with abnormal bilirubin levels had worse prognosis than patients with normal bilirubin. They also had an increased incidence of PVT and tumor multifocality, and higher AFP levels, in patients with both small and larger tumors. The results show an association between bilirubin levels and indices of HCC aggressiveness.

Molecular Determinants of Prognosis in Hepatocellular Carcinoma

Hepatocellular carcinoma is one of the leading causes of death by cancer worldwide. Prognosis of hepatocellular carcinoma is determined by characteristics of the tumor and the surrounding cirrhotic liver. Several molecular signatures reflecting tumor biology and derived from tumor analyses predict early tumor recurrence and survival. In contrast, molecular signatures from cirrhotic non-tumor samples are enriched in immunity/inflammation related genes and could predict late tumor recurrence. Moreover, combination of clinical, pathological, and molecular features may refine prognosis prediction in these patients. Finally, molecular signatures from both tumor and non-tumor tissues will be helpful in the future to guide treatments in different clinical settings.

Transcriptomic responses provide a new mechanistic basis for the chemopreventive effects of folic acid and tributyrin in rat liver carcinogenesis

The steady increase in the incidence and mortality of hepatocellular carcinoma (HCC) signifies a crucial need to understand better its pathogenesis to improve clinical management and prevention of the disease. The aim of this study was to investigate molecular mechanisms for the chemopreventive effects of folic acid and tributyrin alone or in combination on rat hepatocarcinogenesis. Male Wistar rats were subjected to a classic "resistant hepatocyte" model of liver carcinogenesis and treated with folic acid and tributyrin alone or in combination for 5 weeks during promotion stage. Treatment with folic acid and tributyrin alone or in combination strongly inhibited the development of glutathione-S-transferase placental form (GSTP)-positive foci. Microarray analysis showed significant changes in gene expression. A total of 498, 655 and 940 of differentially expressed genes, involved in cell cycle, p53-signaling, angiogenesis and Wnt pathways, was identified in the livers of rats treated with folic acid, tributyrin or folic acid and tributyrin. A detailed analysis of these differentially expressed genes revealed that treatments inhibited angiogenesis in the preneoplastic livers. This was evidenced by the fact that 30 out of 77 differentially expressed genes common to all three treatments are involved in the regulation of the angiogenesis pathway. The inhibition of angiogenesis was confirmed by reduced levels of CD34 protein. In conclusion, the tumor-suppressing activity of folic acid and tributyrin is associated with inhibition of angiogenesis at early stages of rat liver carcinogenesis. Importantly, the combination of folic acid and tributyrin has stronger chemopreventive effect than each of the compounds alone.

Increasing matrix stiffness upregulates vascular endothelial growth factor expression in hepatocellular carcinoma cells mediated by integrin β1

Matrix stiffness as a novel regulation factor involves in modulating the pathogenesis of hepatocellular carcinoma (HCC) invasion or metastasis. However, the mechanism by which matrix stiffness modulates HCC angiogenesis remains unknown. Here, using buffalo rat HCC models with different liver matrix stiffness backgrounds and an in vitro cell culture system of mechanically tunable Collagen1 (COL1)-coated polyacrylamide gel, we investigated the effects of different matrix stiffness levels on vascular endothelial growth factor (VEGF) expression in HCC cells and explored its regulatory mechanism for controlling HCC angiogenesis. Tissue microarray analysis showed that the expression levels of VEGF and CD31 were gradually upregulated in tumor tissues with increasing COL1 and lysyl oxidase (LOX) expression, indicating a positive correlation between tumor angiogenesis and matrix rigidity. The expression of VEGF and the phosphorylation levels of PI3K and Akt were all upregulated in HCC cells on high-stiffness gel than on low-stiffness gel. Meanwhile, alteration of intergrin β1 expression was found to be the most distinctive, implying that it might mediate the response of HCC cells to matrix stiffness simulation. After integrin β1 was blocked in HCC cells using specific monoclonal antibody, the expression of VEGF and the phosphorylation levels of PI3K and Akt at different culture times were accordingly suppressed and downregulated in the treatment group as compared with those in the control group. All data suggested that the extracellular matrix stiffness stimulation signal was transduced into HCC cells via integrin β1, and this signal activated the PI3K/Akt pathway and upregulated VEGF expression. This study unveils a new paradigm in which matrix stiffness as initiators to modulate HCC angiogenesis.

Potential targeted therapy for liver fluke associated cholangiocarcinoma

Biliary tree cancer or cholangiocarcinoma (CCA) is an unusual subtype of liver cancer with exceptionally poor prognosis. Lack of specific symptoms and availability of early diagnostic markers account for late diagnosis of CCA. Surgical treatment is a gold standard choice but few patients are candidates and local recurrence after surgery is high. Benefit of systemic chemotherapy is limited; hence, better treatment options are required. The differences in etiology, anatomical positions and pathology make it difficult to generalize all CCA subtypes for a single treatment regimen. Herein, we review the uniqueness of molecular profiling identified by multiple approaches, for example, serial analysis of gene expression, exome sequencing, transcriptomics/proteomics profiles, protein kinase profile, etc., that provide the opportunity for treatment of liver fluke-associated CCA. Anti-inflammatory, immunomodulator/immunosuppressor, epidermal growth factor receptor or platelet-derived growth factor receptor inhibitors, multi-targeted tyrosine kinase inhibitor, IL6 antagonist, nuclear factor-κB inhibitor, histone modulator, proteasome inhibitor as well as specific inhibitors suggested from various study approaches, such as MetAP2 inhibitor, 1,25(OH)2 D3 and cyclosporine A are suggested in this review for the treatments of this specific CCA subtype. This might provide an alternative treatment option for CCA patients; however, clinical trials in this specific CCA group are required.

Hepatic fibrosis and the microenvironment: fertile soil for hepatocellular carcinoma development

Hepatocellular carcinoma is an emerging worldwide health threat that has few curative treatment options and poor overall survival. Progressive hepatic fibrosis is a common pathway for all forms of chronic liver disease and is closely linked epidemiologically to hepatocellular carcinoma risk. However, the molecular events that predispose a fibrotic liver to cancer development remain elusive. Nonetheless, a permissive hepatic microenvironment provides fertile soil for transition of damaged hepatocytes into hepatocellular carcinoma. Key predisposing features include alterations in the extracellular matrix, bidirectional signaling pathways between parenchymal and nonparenchymal cells, and immune dysfunction. Emerging research into the contributions of autophagy, tumor-associated fibroblasts, and hepatocellular carcinoma progenitor cells to this dangerous milieu also provides new mechanistic underpinnings to explain the contribution of fibrosis to cancer. As effective antifibrotic therapies are developed, these approaches could attenuate the rising surge of hepatocellular carcinoma associated with chronic liver disease.

The EGFR signalling system in the liver: from hepatoprotection to hepatocarcinogenesis

The liver displays an outstanding wound healing and regenerative capacity unmatched by any other organ. This reparative response is governed by a complex network of inflammatory mediators, growth factors and metabolites that are set in motion in response to hepatocellular injury. However, when liver injury is chronic, these regenerative mechanisms become dysregulated, facilitating the accumulation of genetic alterations leading to unrestrained cell proliferation and the development of hepatocellular carcinoma (HCC). The epidermal growth factor receptor (EGFR or ErbB1) signaling system has been identified as a key player in all stages of the liver response to injury, from early inflammation and hepatocellular proliferation to fibrogenesis and neoplastic transformation. The EGFR system engages in extensive crosstalk with other signaling pathways, acting as a true signaling hub for other growth factors, cytokines and inflammatory mediators. Here, we briefly review essential aspects of the biology of the EGFR, the other ErbB receptors, and their ligands in liver injury, regeneration and HCC development. Some aspects of the preclinical and clinical experience with EGFR therapeutic targeting in HCC are also discussed.

Identification of intragenic methylation in the TUSC1 gene as a novel prognostic marker of hepatocellular carcinoma

Patients with hepatocellular carcinoma (HCC) have a poor prognosis, and novel molecular targets for treating recurrence and progression of the disease along with associated biomarkers are urgently required. In the present study, expression and the regulatory mechanism of TUSC1 (tumor suppressor candidate 1) were investigated to determine if it is a candidate tumor suppressor gene for HCC, which shows repressed transcription that involves aberrant DNA methylation. TUSC1 mRNA expression levels in HCC cell lines and 94 pairs of surgical specimens were determined using quantitative real-time reverse transcription polymerase chain reaction assay. Methylation status of HCC cell lines and clinical samples were analyzed to investigate the regulatory mechanism of TUSC1 transcription and the relationship between the methylation status of the TUSC1 gene and clinicopathological factors. The expression and distribution of the TUSC1 protein in liver tissues were determined using immunohistochemistry. A majority of HCC cell lines (89%) and surgical specimens (84%) demonstrated reduced expression levels of TUSC1 mRNA compared with paired non-cancerous liver tissues. The mean mRNA expression level in HCC was significantly lower than in corresponding non-cancerous liver. In contrast, no significant difference was found in TUSC1 mRNA expression level between adjacent normal and cirrhotic liver tissue from HCC patients. The TUSC1 protein expression pattern in HCC and liver tissues was consistent with TUSC1 mRNA expression. Twenty-nine (31%) of 94 patients showed intragenic hypermethylation of the TUSC1 gene in HCC, and hypermethylation was significantly associated with advanced pathological stage. Subsequently, patients with hypermethylation of the TUSC1 gene had a significantly poorer prognosis than patients without hypermethylation. Our results suggest that TUSC1 is a candidate tumor suppressor gene and intragenic hypermethylation is one of the suppressive mechanisms that regulate TUSC1 transcription in HCC. Intragenic methylation of the TUSC1 gene may serve as a novel prognostic marker of HCC.

Activated hepatic stellate cells promote hepatocellular carcinoma cell migration and invasion via the activation of FAK-MMP9 signaling

Activated hepatic stellate cells (HSCs) are the major subtype of stromal cells in the liver tumor microenvironment which can promote the growth and migration of hepatocellular carcinoma (HCC) cells. However, the underlying mechanisms by which activated HSCs exert their oncogenic effects are not fully understood to date. In the present study, we investigated the number of activated HSCs and its clinicopathological significance in HCC and uncovered its correlation with focal adhesion kinase (FAK)-MMP9 signaling. A higher number of activated HSCs was associated with tumor invasion of the portal vein, advanced TNM stage and poorer tumor differentiation. The number of activated HSCs was positively correlated with the expression levels of p-FAK and MMP9 in HCC. Furthermore, we studied the effects of activated HSCs on the migration and invasion of HCC cells in vitro. Conditioned medium (CM) from activated HSCs or co-culture with activated HSCs significantly induced the migration and invasion of HCC cells. In addition, activation of FAK-MMP9 signaling in HCC was demonstrated in the presence of activated HSC-CM and of co-culture. Inhibition of FAK-MMP9 signaling in HCC cells with FAK short hairpin RNA (shRNA) abrogated the effects of activated HSCs on HCC cells. Taken together, our data suggest that activated HSCs in the tumor microenvironment promote HCC cell migration and invasion via activation of FAK-MMP9 signaling.

The Gordian Knot of dysbiosis, obesity and NAFLD

The development of obesity and NAFLD is known to be determined by host genetics, diet and lack of exercise. In addition, the gut microbiota has been identified to influence the development of both obesity and NAFLD. Evidence for the role of the gut microbiota has been shown by preclinical studies of transfer of gut microbiota from lean and obese individuals, with the recipient developing the metabolic features of the donor. Many bidirectional interactions of the gut microbiota, including with food, bile and the intestinal epithelium, have been identified. These interactions might contribute to the distinct steps in the progression from lean to obese states, and to steatosis, steatohepatitis and eventually fibrosis. The predominant steps are efficient caloric extraction from the diet, intestinal epithelial damage and greater entry of bacterial components into the portal circulation. These steps result in activation of the innate immune system, liver inflammation and fibrosis. Fortunately, therapeutic interventions might not require a full understanding of these complex interactions. Although antibiotics are too unselective in their action, probiotics have shown efficacy in reversing obesity and NASH in experimental systems, and are under investigation in humans.

Role of lymphocytes in liver cancer

Hepatocellular carcinoma (HCC) typically occurs in patients with chronic inflammatory liver diseases, such as viral hepatitis or (non-)alcoholic steatohepatitis. Inflammation appears indeed as a crucial factor in hepatocarcinogenesis. Nevertheless, sophisticated animal models and studies of human samples revealed that the HCC also elicits antitumor immune responses. Patrolling and infiltrating lymphocytes (e.g., NKT and T cells, respectively) can exert decisive functions in the transition from chronic hepatic inflammation to cancer as well as in antitumor immune responses. An improved understanding of the cellular and molecular mechanisms whereby inflammation promotes or restricts hepatocarcinogenesis will open new avenues for therapeutic approaches to liver cancer.

Hepatitis C virus infection, microRNA and liver disease progression

Hepatitis C virus (HCV) is a global health problem with an estimated 170-200 million peoples (approximately 3% of world population) are chronically infected worldwide and new infections are predicted to be on rise in coming years. HCV infection remains categorized as a major risk factor for chronic hepatitis, liver cirrhosis and hepatocellular carcinoma worldwide. There has been considerable improvement in our understanding of virus life cycle since, the discovery of HCV two-decades ago. MicroRNAs (miRNAs) are important players in establishment of HCV infection and their propagation in infected hepatocytes. They target crucial host cellular factors needed for productive HCV replication and augmented cell growth. Very first anti-miRNA oligonucleotides, miravirsen has been tested in clinical trial and shown promising results as therapeutic agent in treatment against chronic HCV infection. Deregulated expression of miRNAs has been linked to the pathogenesis associated with HCV infection by controlling signaling pathways such as, proliferation, apoptosis and migration. Circulating miRNAs emerging as growing field in identification of biomarkers in disease progression and their potential as a means of communication between cells inside the liver is an exciting area of research in future. This review focuses on recent studies enforcing the contribution of miRNAs in HCV life cycle and coordinated regulation in HCV mediated liver disease progression.

Paracrine activation of hepatic stellate cells in platelet-derived growth factor C transgenic mice: evidence for stromal induction of hepatocellular carcinoma

Cirrhosis is the primary risk factor for the development of hepatocellular carcinoma (HCC), yet the mechanisms by which cirrhosis predisposes to carcinogenesis are poorly understood. Using a mouse model that recapitulates many aspects of the pathophysiology of human liver disease, we explored the mechanisms by which changes in the liver microenvironment induce dysplasia and HCC. Hepatic expression of platelet-derived growth factor C (PDGF-C) induces progressive fibrosis, chronic inflammation, neoangiogenesis and sinusoidal congestion, as well as global changes in gene expression. Using reporter mice, immunofluorescence, immunohistochemistry and liver cell isolation, we demonstrate that receptors for PDGF-CC are localized on hepatic stellate cells (HSCs), which proliferate, and transform into myofibroblast-like cells that deposit extracellular matrix and lead to production of growth factors and cytokines. We demonstrate induction of cytokine genes at 2 months, and stromal cell-derived hepatocyte growth factors that coincide with the onset of dysplasia at 4 months. Our results support a paracrine signaling model wherein hepatocyte-derived PDGF-C stimulates widespread HSC activation throughout the liver leading to chronic inflammation, liver injury and architectural changes. These complex changes to the liver microenvironment precede the development of HCC. Further, increased PDGF-CC levels were observed in livers of patients with nonalcoholic fatty steatohepatitis and correlate with the stage of disease, suggesting a role for this growth factor in chronic liver disease in humans. PDGF-C transgenic mice provide a unique model for the in vivo study of tumor-stromal interactions in the liver.

Progress in understanding role of urotensin Ⅱ in hepatic cirrhosis

Urotensin Ⅱ (UⅡ) is a potent vasoactive substance that can result in vasoactive response through interaction with its specific orphan G-protein-coupled receptor GPR-14. In addition to the role of vasoactivity, UⅡ can promote mitosis and fibrosis. The vascular role of UⅡ is to some degree both species- and disease-specific. Studies have found that plasma levels of UⅡ are elevated in patients with cirrhosis, but the relationship between plasma levels of UⅡ and the development of chronic liver disease and portal hypertension has yet to be fully elucidated. This review focuses on the potential relevance of UⅡ as vasoactive substance in chronic liver disease and the site where UⅡ is overproduced.

From cirrhosis to hepatocellular carcinoma: new molecular insights on inflammation and cellular senescence

Sequential progression from chronic liver disease to fibrosis and to cirrhosis culminates in neoplasia in hepatocellular carcinoma (HCC). The preneoplastic setting of the cirrhotic background provides a conducive environment for cellular transformation. The role of classical inflammation in cirrhosis is widely known, but the exact mechanism linking inflammation and cancer remains elusive. Recent studies have elucidated roles for NF-κB, STAT3 and JNK as possible missing links. In addition, the "inflammasome" (a multiprotein complex and sensor of cellular damage) is a recently identified player in this field. The hallmarks of cirrhosis include necroinflammation, deposition of extracellular matrix and shortening of telomeres, leading to senescence and regeneration. Additionally, the accumulation of genetic/epigenetic changes propels atypical cells toward a malignant phenotype. This review provides recent information on the classical inflammatory pathway, together with a spotlight on inflammasomes and the immunomodulatory role of cellular senescence during the progression from cirrhosis to HCC. Moreover, lacunae in the current knowledge were identified and key questions raised on whether the observed adaptive responses are beneficial or detrimental to tissue homeostasis in a complex organ like liver.