Non-parenchymal liver cells support the growth advantage in the first stages of hepatocarcinogenesis

Suppression of NASH-Related HCC by Farnesyltransferase Inhibitor through Inhibition of Inflammation and Hypoxia-Inducible Factor-1α Expression

Inflammatory processes play major roles in carcinogenesis and the progression of hepatocellular carcinoma (HCC) derived from non-alcoholic steatohepatitis (NASH). But, there are no therapies for NASH-related HCC, especially focusing on these critical steps. Previous studies have reported that farnesyltransferase inhibitors (FTIs) have anti-inflammatory and anti-tumor effects. However, the influence of FTIs on NASH-related HCC has not been elucidated. In hepatoblastoma and HCC cell lines, HepG2, Hep3B, and Huh-7, we confirmed the expression of hypoxia-inducible factor (HIF)-1α, an accelerator of tumor aggressiveness and the inflammatory response. We established NASH-related HCC models under inflammation and free fatty acid burden and confirmed that HIF-1α expression was increased under both conditions. Tipifarnib, which is an FTI, strongly suppressed increased HIF-1α, inhibited cell proliferation, and induced apoptosis. Simultaneously, intracellular interleukin-6 as an inflammation marker was increased under both conditions and significantly suppressed by tipifarnib. Additionally, tipifarnib suppressed the expression of phosphorylated nuclear factor-κB and transforming growth factor-β. Finally, in a NASH-related HCC mouse model burdened with diethylnitrosamine and a high-fat diet, tipifarnib significantly reduced tumor nodule formation in association with decreased serum interleukin-6. In conclusion, tipifarnib has anti-tumor and anti-inflammatory effects in a NASH-related HCC model and may be a promising new agent to treat this disease.

PPARγ signaling in hepatocarcinogenesis: Mechanistic insights for cellular reprogramming and therapeutic implications

Liver cancer or hepatocellular carcinoma (HCC) is leading cause of cancer-related mortalities globally. The therapeutic approaches for chronic liver diseases-associated liver cancers aimed at modulating immune check-points and peroxisome proliferator-activated receptor gamma (PPARγ) signaling pathway during multistep process of hepatocarcinogenesis that played a dispensable role in immunopathogenesis and outcomes of disease. Herein, the review highlights PPARγ-induced effects in balancing inflammatory (tumor necrosis factor alpha (TNF-α), interleukin (IL)-6, IL-1) and anti-inflammatory cytokines (IL-10, transforming growth factor beta (TGF-β), and interplay of PPARγ, hepatic stellate cells and fibrogenic niche in cell-intrinsic and -extrinsic crosstalk of hepatocarcinogenesis. PPARγ-mediated effects in pre-malignant microenvironment promote growth arrest, cell senescence and cell clearance in liver cancer pathophysiology. Furthermore, PPARγ-immune cell axis of liver microenvironment exhibits an immunomodulation strategy of resident immune cells of the liver (macrophages, natural killer cells, and dendritic cells) in concomitance with current clinical guidelines of the European Association for Study of Liver Diseases (EASL) for several liver diseases. Thus, mechanistic insights of PPARγ-associated high value targets and canonical signaling suggest PPARγ as a possible therapeutic target in reprogramming of hepatocarcinogenesis to decrease burden of liver cancers, worldwide.

IRE1A Stimulates Hepatocyte-Derived Extracellular Vesicles That Promote Inflammation in Mice With Steatohepatitis

BACKGROUND & AIMS

Endoplasmic reticulum to nucleus signaling 1 (ERN1, also called IRE1A) is a sensor of the unfolded protein response that is activated in the livers of patients with nonalcoholic steatohepatitis (NASH). Hepatocytes release ceramide-enriched inflammatory extracellular vesicles (EVs) after activation of IRE1A. We studied the effects of inhibiting IRE1A on release of inflammatory EVs in mice with diet-induced steatohepatitis.

METHODS

C57BL/6J mice and mice with hepatocyte-specific disruption of Ire1a (IRE1α^Δhep) were fed a diet high in fat, fructose, and cholesterol to induce development of steatohepatitis or a standard chow diet (controls). Some mice were given intraperitoneal injections of the IRE1A inhibitor 4μ8C. Mouse liver and primary hepatocytes were transduced with adenovirus or adeno-associated virus that expressed IRE1A. Livers were collected from mice and analyzed by quantitative polymerase chain reaction and chromatin immunoprecipitation assays; plasma samples were analyzed by enzyme-linked immunosorbent assay. EVs were derived from hepatocytes and injected intravenously into mice. Plasma EVs were characterized by nanoparticle-tracking analysis, electron microscopy, immunoblots, and nanoscale flow cytometry; we used a membrane-tagged reporter mouse to detect hepatocyte-derived EVs. Plasma and liver tissues from patients with NASH and without NASH (controls) were analyzed for EV concentration and by RNAscope and gene expression analyses.

RESULTS

Disruption of Ire1a in hepatocytes or inhibition of IRE1A reduced the release of EVs and liver injury, inflammation, and accumulation of macrophages in mice on the diet high in fat, fructose, and cholesterol. Activation of IRE1A, in the livers of mice, stimulated release of hepatocyte-derived EVs, and also from cultured primary hepatocytes. Mice given intravenous injections of IRE1A-stimulated, hepatocyte-derived EVs accumulated monocyte-derived macrophages in the liver. IRE1A-stimulated EVs were enriched in ceramides. Chromatin immunoprecipitation showed that IRE1A activated X-box binding protein 1 (XBP1) to increase transcription of serine palmitoyltransferase genes, which encode the rate-limiting enzyme for ceramide biosynthesis. Administration of a pharmacologic inhibitor of serine palmitoyltransferase to mice reduced the release of EVs. Levels of XBP1 and serine palmitoyltransferase were increased in liver tissues, and numbers of EVs were increased in plasma, from patients with NASH compared with control samples and correlated with the histologic features of inflammation.

CONCLUSIONS

In mouse hepatocytes, activated IRE1A promotes transcription of serine palmitoyltransferase genes via XBP1, resulting in ceramide biosynthesis and release of EVs. The EVs recruit monocyte-derived macrophages to the liver, resulting in inflammation and injury in mice with diet-induced steatohepatitis. Levels of XBP1, serine palmitoyltransferase, and EVs are all increased in liver tissues from patients with NASH. Strategies to block this pathway might be developed to reduce liver inflammation in patients with NASH.

Three-Dimensional Spheroid Primary Human Hepatocytes in Monoculture and Coculture with Nonparenchymal Cells

Recent advances in the development of various culture platforms are promising for achieving more physiologically relevant in vitro hepatic models using primary human hepatocytes (PHHs). Previous studies have shown the value of PHHs three-dimensional (3D) spheroid models, cultured in low cell number (1330-2000 cells/3D spheroid), to study long-term liver function as well as pharmacological drug effects and toxicity. In this study, we report that only plateable PHHs aggregate and form compact 3D spheroids with a success rate of 79%, and 96% reproducibility. Out of 3D spheroid forming PHH lots, 65% were considered stable (<50% ATP decrease) over the subsequent 14 days of culture, with reproducibility of a given PHH lot being 82%. We also report successful coculturing of PHHs with human liver nonparenchymal cells (NPCs). Crude P1_c-NPC fractions were obtained by low centrifugation of the PHH supernatant fraction followed by a few days of culture before harvesting and cryopreservation. At aggregation of PHHs/P1_c-NPCs (2:1 ratio 3D spheroids), liver sinusoidal endothelial cells, Kupffer cells, and hepatic stellate cells were successfully integrated and remained present throughout the subsequent 14-day culture period as revealed by mRNA expression markers and immunostaining. Increased mRNA expression of albumin (ALB), apolipoprotein B (APOB), cytochrome P450 3A4 (CYP3A4), and increased albumin secretion compared to PHH 3D spheroid monocultures highlighted that in a 3D spheroid coculture, configuration with NPCs, PHH functionality is increased. We thus achieved the development of a more integrated coculture model system requiring low cell numbers, of particular interest due to the scarcity of human liver NPCs.

One New Phenolic Compound from Castanea mollissima Shells and its Suppression of HepatomaCell Proliferation and Inflammation by Inhibiting NF-κB Pathway

Shells of Castanea mollissima (CMS), an agricultural remain and often considered waste from chestnut processing industry, have been proven a resource for traditional Chinese medicine. One new phenol, named castanolB(1), andsix known phenolic compounds (2⁻7) were isolated froma water-soluble extract of CMS. Their chemical structures were determined using preparative HPLC and various spectral analyses, and then were compared to literatures, which indicated the first identification of the seven compounds from C. mollissima. The physicochemical property of compound (2) was also reported for the first time. After antiproliferative screening of compounds (1⁻7) on LPS-induced SMMC-7721 and HepG2 hepatoma cells, castanolB (1) showed the best suppression. CastanolB(1) also significantly induced cell apoptosis. Furthermore, castanolB (1) decreasedsecretion of TNF-α and IL-6. Mechanistically, TLR4⁻NF-κB pathway was inhibited bycastanolB (1) with downregulation of TLR4, IKKβ, and NF-κB p65. This study presents a new phenol and shows its profiles of anticancer and anti-inflammation via inhibiting the TLR4⁻NF-κB pathway.

Senescence and cell death in chronic liver injury: roles and mechanisms underlying hepatocarcinogenesis

Chronic liver injury (CLI) is a complex pathological process typically characterized by progressive destruction and regeneration of liver parenchymal cells due to diverse risk factors such as alcohol abuse, drug toxicity, viral infection, and genetic metabolic disorders. When the damage to hepatocytes is mild, the liver can regenerate itself and restore to the normal state; when the damage is irreparable, hepatocytes would undergo senescence or various forms of death including apoptosis, necrosis and necroptosis. These pathological changes not only promote the progression of the existing hepatopathies via various underlying mechanisms but are closely associated with hepatocarcinogenesis. In this review, we discuss the pathological changes that hepatocytes undergo during CLI, and their roles and mechanisms in the progression of hepatopathies and hepatocarcinogenesis. We also give a brief introduction about some animal models currently used for the research of CLI and progress in the research of CLI.

Photoactivation provides a mechanistic explanation for pan-assay interference behaviour of 2-aminopyrroles in lipoxygenase inhibition

Human 15-lipoxygenase-1 (h-15-LOX-1) is a promising drug target in inflammation and cancer. In this study substitution-oriented screening (SOS) has been used to identify compounds with a 2-aminopyrrole scaffold as inhibitors for h-15-LOX-1. The observed structure activity relationships (SAR) proved to be relatively flat. IC₅₀'s for the most potent inhibitor of the series did not surpass 6.3 μM and the enzyme kinetics demonstrated uncompetitive inhibition. Based on this, we hypothesized that the investigated 2-aminopyrroles are pan assay interference compounds (PAINS) with photoactivation via a radical mechanism. Our results demonstrated clear photoactivation of h-15-LOX-1 inhibition under UV and visible light. In addition, the investigated 2-aminopyrroles decreased viability of cultured human hepatocarcinoma cells HCC-1.2 in a dose-dependent manner with LD₅₀ ranging from 0.55 ± 0.15 μM (21B10) to 2.75 ± 0.91 μM (22). Taken together, this indicates that photoactivation can play an important role in the biological activity of compounds with a 2-amino-pyrrole scaffold as investigated here.

Proinflammatory mesenchymal effects of the non-genotoxic hepatocarcinogen phenobarbital: a novel mechanism of antiapoptosis and tumor promotion

Many environmental pollutants and drugs, including steroid hormones, hypolipidemics and antiepileptics, are non-genotoxic carcinogens (NGC) in rodent liver. The mechanism of action and the risk for human health are still insufficiently known. Here, we study the effects of phenobarbital (PB), a widely used model NGC, on hepatic epithelial-mesenchymal crosstalk and the impact on hepatic apoptosis. Mesenchymal cells (MC) and hepatocytes (HC) were isolated from control and PB-treated rat livers. PB induced extensive changes in gene expression in MC and much less in HC as shown by transcriptomics with oligoarrays. In MC only, transcript levels of numerous proinflammatory cytokines were elevated. Correspondingly, ELISA on the supernatant of MC from PB-treated rats revealed enhanced release of various cytokines. In cultured HC, this supernatant caused (i) nuclear translocation and activation of nuclear factor-κB (shown by immunoblots of nuclear extracts and reporter gene assays), (ii) elevated expression of proinflammatory genes and (iii) protection from the proapoptotic action of transforming growth factor beta 1 (TGFß1). PB treatment in vivo or in vitro elevated the production and release of tumor necrosis factor alpha from MC, which was identified as mainly responsible for the inhibition of apoptosis in HC. In conclusion, our findings reveal profound proinflammatory effects of PB on hepatic mesenchyme and mesenchymal-epithelial interactions. The resulting release of cytokines acts antiapoptotic in HC, an effect crucial for tumor promotion and carcinogenesis by NGC.

E-cadherin, guardian of liver physiology

E-cadherin is a cell-to-cell adhesion molecule involved in epithelial cell behavior, tissue formation and cancer suppression. In the liver, E-cadherin is expressed by hepatocytes and biliary epithelial cells. However, the exact role of E-cadherin in hepatic pathophysiology remains largely unknown. Recently, specific loss of E-cadherin in liver epithelial cells has been shown to favor periportal fibrosis, periportal inflammation and liver cancer progression, suggesting that E-cadherin is a central liver protector.

Cell expression patterns of CD147 in N-diethylnitrosamine/phenobarbital-induced mouse hepatocellular carcinoma

Overexpression of CD147/basigin in hepatic cells promotes the progression of hepatocellular carcinoma (HCC). Whether CD147 also expressed in liver non-parenchymal cells and associated with HCC development was unknown. The aim of the study was to explore time-dependent cell expression patterns of CD147 in a widely accepted N-diethylnitrosamine/phenobarbital (DEN/PB)-induced HCC mouse model. Liver samples collected at month 1-12 of post-DEN/PB administration were assessed the localization of CD147 in hepatocytes, endothelial cells, hepatic stellate cells, and macrophages. Immunohistochemistry analysis showed that CD147 was upregulated in liver tumors during month 1-8 of DEN/PB induction. Expression of CD147 was positively correlated with cytokeratin 18, a hepatocyte marker (r = 0.7857, P = 0.0279), CD31 (r = 0.9048, P = 0.0046), an endothelial cell marker, and CD68, a macrophage marker (r = 0.7619, P = 0.0368). A significant correlation was also observed between CD147 and alpha-smooth muscle actin (r = 0.8857, P = 0.0333) at DEN/PB initiation and early stage of tumor formation. Immunofluorescence and fluorescence in situ hybridization showed that CD147 co-expressed with cytokeratin 18, CD31, alpha-smooth muscle actin, and CD68. Moreover, there existed positive correlations between CD147 and microvessel density (r = 0.7857, P = 0.0279), CD147 and Ki-67 (r = 0.9341, P = 0.0022) in the development of DEN/PB-induced HCC. In conclusion, our results demonstrated that CD147 was upregulated in the liver parenchymal and mesenchymal cells and involved in angiogenesis and tumor cell proliferation in the development of DEN/PB-induced HCC.

Fibroblast growth factor family as a potential target in the treatment of hepatocellular carcinoma

Hepatocellular cancer (HCC) is currently the third leading cause of cancer death worldwide. The prognosis of patients diagnosed with late-stage disease is dismal due to high resistance to conventional systemic therapies. The introduction of sorafenib, despite its limited efficacy, as the standard systemic therapy for advanced HCC has paved a way for targeted molecular therapies for HCC. Fibroblast growth factor (FGF) signaling plays an important role in the developing embryo and the adult. The FGF signaling pathway is often hijacked by cancer cells, including HCC. Several alterations in FGF signaling correlate with poor outcome in HCC patients, suggesting that this family of signaling molecules plays an important role in the development of HCC. Multikinase inhibitors targeting FGF signaling are currently under investigation in clinical trials. This review discusses the current understanding of the biological and clinical implications of aberrant FGF signaling in the prognosis, diagnosis, and treatment of HCC.

The inflammatory microenvironment in hepatocellular carcinoma: a pivotal role for tumor-associated macrophages

Hepatocellular carcinoma (HCC) is one of the most common and aggressive human cancers worldwide. HCC is an example of inflammation-related cancer and represents a paradigm of the relation occurring between tumor microenvironment and tumor development. Tumor-associated macrophages (TAMs) are a major component of leukocyte infiltrate of tumors and play a pivotal role in tumor progression of inflammation-related cancer, including HCC. Several studies indicate that, in the tumor microenvironment, TAMs acquire an M2-polarized phenotype and promote angiogenesis, metastasis, and suppression of adaptive immunity through the expression of cytokines, chemokines, growth factors, and matrix metalloproteases. Indeed, an established M2 macrophage population has been associated with poor prognosis in HCC. The molecular links that connect cancer cells and TAMs are not completely known, but recent studies have demonstrated that NF-κB, STAT-3, and HIF-1 signaling pathways play key roles in this crosstalk. In this paper, we discuss the current knowledge about the role of TAMs in HCC development, highlighting the role of TAM-derived cytokines, chemokines, and growth factors in the initiation and progression of liver cancer and outlining the signaling pathways involved in the interplay between cancer cells and TAMs.

Proteomics reveals acute pro-inflammatory and protective responses in rat Kupffer cells and hepatocytes after chemical initiation of liver cancer and after LPS and IL-6

Inflammation is a key event in the development of liver cancer. We studied early inflammatory responses of Kupffer cells (KCs) and hepatocyte (HC) after cancer initiation. The chemical carcinogen N-nitrosomorpholine (NNM) was used in a rat model. We applied a comprehensive analytical strategy including metabolic labeling, 2-D PAGE, LC-MS/MS-based spot identification and shotgun proteomics and thus determined the rates of synthesis of individual proteins, compared whole tissue with isolated constituent cells and performed in vivo to in vitro comparisons of NNM effects. NNM increased synthesis of overall and 138 individual proteins identified in HC and/or KC, indicating reprogramming of metabolism favoring protection, repair and replacement of cell constituents in HC and KC. Secretome analysis by 2-D PAGE and shotgun proteomics of HC revealed the induction of acute phase proteins, in case of KC of proteases, cytokines and chemokines, indicating inflammatory effects. All responses were induced rapidly, independently of signals from other cells, and closely mimicked the pro-inflammatory and protective effects of inflammation modulators LPS in KC and IL-6 in HC. In conclusion, the carcinogen NNM exerts pro-inflammatory effects in the liver, partially by direct activation of KC. The acute inflammation and its protective component will enhance formation, survival and proliferation of initiated cells and may therefore act synergistically with the genotoxic action of the carcinogen.

Decrease of hepatic stellate cells in rats with enhanced sensitivity to clofibrate-induced hepatocarcinogenesis

To examine the possible involvement of nonparenchymal cells in the development of preneoplastic hepatic lesions induced by clofibrate (CF), alterations of these cells were investigated immunohistochemically in glutathione S-transferase M1 gene polymorphic rats (KS and NC types) with different cancer susceptibilities. After CF administration for 8 weeks, α-smooth muscle actin (α-SMA)-positive hepatic stellate cells (HSC) were markedly decreased in sensitive KS-type rats, but not in the NC-type rats. Kupffer cells were decreased with similar extents between them. The sinusoidal endothelial cells were not changed in either type. The other markers for HSC, vimentin and CRBP1, also confirmed the decrease of HSC in the KS type. The decrease of HSC was not observed at 4 weeks of CF administration. Preneoplastic peroxisomal bifunctional enzyme-negative foci were detected in the KS-type rats at 8 weeks of CF administration, but not at 4 weeks. Human HSC were cultured in the presence of clofibric acid and expression of most HSC marker genes, such as vimentin and α-SMA (ACTA2), evaluated by a microarray, was not altered by the treatment, suggesting that HSC loss in the KS-type rats was not due to the direct toxic effect of CF. The expression levels of most HSC marker genes were low in both control and CF-treated rat livers. A possible link between HSC loss and the development of preneoplastic hepatic foci is discussed.

Inhibin/activin expression in human and rodent liver: subunits α and βB as new players in human hepatocellular carcinoma?

Background:

Activins and inhibins belong to the TGFβ-superfamily, which controls cell proliferation and differentiation in many organs. Activin A, the dimer of inhibin βA subunit, acts strongly anti-proliferative in hepatocytes. Little is known on the other activin/inhibin subunits in human liver and hepatocellular carcinoma (HCC).

Methods:

We studied the expression of the complete inhibin family α, βA, βB, βC, βE in normal liver, tumour-adjacent and HCC tissue, 12 additional organs and rodent liver. A total of 16 HCC and 10 disease-free livers were analysed. Expression of inhibin subunits was determined by qRT–PCR, normalised to RNA input and by geNorm algorithm, and confirmed by immunohistochemistry.

Results:

Remarkably, βA expression was not decreased in HCC. Similarly, βC and βE exhibited no major changes. In contrast, inhibin α, barely detectable in normal liver, was strongly increased in tumour-adjacent liver and dramatically enhanced in HCC. βB was strongly enhanced in some HCC. At variance with human liver, rodent liver showed higher inhibin α and βC expression, but βA was somewhat, and βB dramatically lower.

Conclusions:

Upregulation of inhibin α – and possibly of βB – may shield HCC cells from anti-proliferative effects of activin A. Dramatic variations between humans and rodents may reflect different functions of some inhibins/activins.

Up-regulation of the fibroblast growth factor 8 subfamily in human hepatocellular carcinoma for cell survival and neoangiogenesis

Fibroblast growth factors (FGFs) and their high-affinity receptors [fibroblast growth factor receptors (FGFRs)] contribute to autocrine and paracrine growth stimulation in several non-liver cancer entities. Here we report that at least one member of the FGF8 subfamily (FGF8, FGF17, and FGF18) was up-regulated in 59% of 34 human hepatocellular carcinoma (HCC) samples that we investigated. The levels of the corresponding receptors (FGFR2, FGFR3, and FGFR4) were also elevated in the great majority of the HCC cases. Overall, 82% of the HCC cases showed overexpression of at least one FGF and/or FGFR. The functional implications of the deregulated FGF/FGFR system were investigated by the simulation of an insufficient blood supply. When HCC-1.2, HepG2, or Hep3B cells were subjected to serum withdrawal or the hypoxia-mimetic drug deferoxamine mesylate, the expression of FGF8 subfamily members increased dramatically. In the serum-starved cells, the incidence of apoptosis was elevated, whereas the addition of FGF8, FGF17, or FGF18 impaired apoptosis, which was associated with phosphorylation of extracellular signal-regulated kinase 1/2 and ribosomal protein S6. In contrast, down-modulation of FGF18 by small interfering RNA (siRNA) significantly reduced the viability of the hepatocarcinoma cells. siRNA targeting FGF18 also impaired the cells' potential to form clones at a low cell density or in soft agar. With respect to the tumor microenvironment, FGF17 and FGF18 stimulated the growth of HCC-derived myofibroblasts, and FGF8, FGF17, and FGF18 induced the proliferation and tube formation of hepatic endothelial cells.

CONCLUSION

FGF8, FGF17, and FGF18 are involved in autocrine and paracrine signaling in HCC and enhance the survival of tumor cells under stress conditions, malignant behavior, and neoangiogenesis. Thus, the FGF8 subfamily supports the development and progression of hepatocellular malignancy.

Characterization of the liver tissue interstitial fluid (TIF) proteome indicates potential for application in liver disease biomarker discovery

Tissue interstitial fluid (TIF) forms the interface between circulating body fluids and intracellular fluid. Pathological alterations of liver cells could be reflected in TIF, making it a promising source of liver disease biomarkers. Mouse liver TIF was extracted, separated by SDS-PAGE, analyzed by linear ion trap mass spectrometer, and 1450 proteins were identified. These proteins may be secreted, shed from membrane vesicles, or represent cellular breakdown products. They show different profiling patterns, quantities, and possibly modification/cleavage of intracellular proteins. The high solubility and even distribution of liver TIF supports its suitability for proteome analysis. Comparison of mouse liver TIF data with liver tissue and plasma proteome data identified major proteins that might be released from liver to plasma and serve as blood biomarkers of liver origin. This result was partially supported by comparison of human liver TIF data with human liver and plasma proteome data. Paired TIFs from tumor and nontumor liver tissues of a hepatocellular carcinoma patient were analyzed and the profile of subtracted differential proteins supports the potential for biomarker discovery in TIF. This study is the first analysis of the liver TIF proteome and provides a foundation for further application of TIF in liver disease biomarker discovery.

The epidermal growth factor receptor: a link between inflammation and liver cancer

Epidemiological studies have established that many tumours occur in association with persistent inflammation. One clear example of inflammation-related cancer is hepatocellular carcinoma (HCC). HCC slowly unfolds on a background of chronic inflammation triggered by exposure to infectious agents (hepatotropic viruses), toxic compounds (ethanol), or metabolic impairment. The molecular links that connect inflammation and cancer are not completely known, but evidence gathered over the past few years is beginning to define the precise mechanisms. A central role for cytokines such as interleukin-6 (IL-6) and IL-1 (alpha and beta) in liver cancer has been established in experimental models. Besides these inflammatory mediators, mounting evidence points to the dysregulation of specific growth and survival-related pathways in HCC development. Among them is the pathway governed by the epidermal growth factor receptor (EGFR), which can be bound and activated by a broad family of ligands. Of special relevance is the fact that the EGFR engages in extensive crosstalk with other signaling pathways, serving as a "signaling hub" for an increasing list of growth factors, cytokines, and inflammatory mediators. In this review, we summarize the most recent evidences supporting a role for the EGFR system in inflammation-related cell signaling, with special emphasis in liver inflammation and HCC. The molecular dissection of the pathways connecting the inflammatory reaction and neoplasia will facilitate the development of novel and more effective antitumor strategies.

Inflammation and liver cancer: new molecular links

A connection between inflammation and cancer has been long suspected. Epidemiological studies have established that many tumors occur in association with chronic infectious diseases, and it is also known that persistent inflammation in the absence of infections increases the risk and accelerates the development of cancer. One clear example of inflammation-related cancer is hepatocellular carcinoma (HCC). HCC is a type tumor that slowly unfolds on a background of chronic inflammation mainly triggered by exposure to infectious agents (hepatotropic viruses) or to toxic compounds (ethanol). The molecular links that connect inflammation and cancer are not completely known, but evidences gathered over the past few years are beginning to define the precise mechanisms. In this article we review the most compelling evidences on the role of transcription factors such as NF-kappaB and STAT3, cytokines like IL-6 and IL-1alpha, ligands of the EGF receptor and other inflammatory mediators in cancer development, with special emphasis in HCC. The molecular dissection of the pathways connecting the inflammatory reaction and neoplasia will pave the way for better therapies to treat cancers.

HB-EGF is a paracrine growth stimulator for early tumor prestages in inflammation-associated hepatocarcinogenesis

BACKGROUND/AIMS

We studied the impact of heparin-binding epidermal growth factor-like growth factor (HB-EGF) on inflammation-driven hepatocarcinogenesis.

METHODS

HB-EGF expression was determined by qRT-PCR and immunodetection in hepatocellular adenoma and carcinoma and in mesenchymal (MC) and parenchymal liver cells obtained from different models of inflammation. The functions of HB-EGF in early hepatocarcinogenesis were assessed in co-cultures of unaltered and initiated/premalignant hepatocytes.

RESULTS

In human and rat (pre)malignant liver lesions, HB-EGF levels were comparable to that of the surrounding tissue. In inflamed livers HB-EGF was expressed predominantly in MC and was further increased by pro-inflammatory lipopolysaccharide (LPS) or linoleic acid hydroperoxide (LOOH). In culture, DNA-replication occurred rather in initiated/premalignant than unaltered hepatocytes and was further elevated by LOOH- or LPS-stimulated MC-supernatants. The supernatant effects were abrogated by pre-incubation with HB-EGF-neutralizing antisera. HB-EGF itself induced DNA-replication and mitosis preferentially in the initiated/premalignant cells. When transducing hepatocytes with a dominant-negative ErbB1-construct, HB-EGF-induced DNA-replications were blocked completely in unaltered hepatocytes but incompletely in initiated/premalignant cells, which suggests elevated ErbB-mediated signal transduction in first stages of hepatocarcinogenesis.

CONCLUSIONS

Pro-inflammatory stimuli induce the release of HB-EGF from MC, which stimulates DNA-replication in initiated/premalignant hepatocytes. Similar mechanisms may contribute to carcinogenesis in human inflammatory liver diseases.

New cellular tools reveal complex epithelial-mesenchymal interactions in hepatocarcinogenesis

To enable detailed analyses of cell interactions in tumour development, new epithelial and mesenchymal cell lines were established from human hepatocellular carcinoma by spontaneous outgrowth in culture. We obtained several hepatocarcinoma (HCC)-, B-lymphoblastoid (BLC)-, and myofibroblastoid (MF)-lines from seven cases. In-depth characterisation included cell kinetics, genotype, tumourigenicity, expression of cell-type specific markers, and proteome patterns. Many functions of the cells of origin were found to be preserved. We studied the impact of the mesenchymal lines on hepatocarcinogenesis by in vitro assays. BLC- and MF-supernatants strongly increased the DNA replication of premalignant hepatocytes. The stimulation by MF-lines was mainly attributed to HGF secretion. In HCC-cells, MF-supernatant had only minor effects on cell growth but enhanced migration. MF-lines also stimulated neoangiogenesis through vEGF release. BLC-supernatant dramatically induced death of HCC-cells, which could be largely abrogated by preincubating the supernatant with TNFβ-antiserum. Thus, the new cell lines reveal stage-specific stimulatory and inhibitory interactions between mesenchymal and epithelial tumour cells. In conclusion, the new cell lines provide unique tools to analyse essential components of the complex interplay between the microenvironment and the developing liver cancer, and to identify factors affecting proliferation, migration and death of tumour cells, neoangiogenesis, and outgrowth of additional malignancy.

Proinflammatory cytokines increase hepatocellular carcinoma cells thermotolerance: evidence of how local inflammation may negatively impact radiofrequency ablation local control rates

BACKGROUND

Hepatocellular carcinomas (HCC) associated with inflammation that undergo radiofrequency ablation (RFA) appear to have poorer local control rates. Little is known of how mediators of inflammation influence HCC cellular thermotolerance, which in part is mediated by heat shock protein 70 (HSP70). This study determines how inflammatory mediators affect cellular thermotolerance and provides insight into how associated inflammation may impact HCC RFA local control rates.

METHODS

HepG2 cell lines were cultured in control medium (CM) or CM containing conditioned medium of endotoxin-activated macrophage (CMM). Serial dilutions of CMM established microenvironments approximating low, medium, and high CMM. All groups underwent a heat shock challenge (HSC) at 45 degrees C for 10 min. Western blot, Northern blot, densitometric analysis, along with thymidine and clonogenic assays determined how inflammation influenced multiple biological endpoints.

RESULTS

Cells cultured in low CMM expressed significantly more HSP70 RNA and protein compared with control cells after HSC. The cells also had a higher proliferative and survival rate after HSC compared with control cells. Medium CMM cultured cells had no significant difference in HSP70 RNA and protein production or proliferation and survival rates after HSC, compared with CM cultured cells. AT high CMM, the inhibitory effects of inflammatory mediators prevailed and all of the measured endpoints were significantly less compared with CM cultured cells.

CONCLUSIONS

This study demonstrates that inflammation can alter the responsiveness of HCC cells to a HSC in a dose-dependent manner. This study supports the clinical observation that HCC associated with chronic inflammation have worse RFA local control rates.

Hepatic NF-kappa B essential modulator deficiency prevents obesity-induced insulin resistance but synergizes with high-fat feeding in tumorigenesis

Development of obesity-associated insulin resistance and diabetes mellitus type 2 has been linked to activation of proinflammatory pathways in the liver, leading to impaired insulin signal transduction. To further define the role of hepatic NF-kappaB activation in this process, we have analyzed glucose metabolism in mice with liver-specific inactivation of the NF-kappaB essential modulator gene (NEMO(L-KO) mice) exposed to a high-fat diet (HFD). These animals are protected from the development of obesity-associated insulin resistance, highlighting the importance of hepatic NF-kappaB activation in this context. However, hepatic NEMO deficiency synergizes with HFD in the development of liver steatosis as a consequence of decreased peroxisome proliferator-activated receptor (PPAR-alpha) and increased PPAR-gamma expression. Steatosis interacts with increased inflammation, causing elevated apoptosis in the livers of these mice under HFD. These changes result in liver tumorigenesis of NEMO(L-KO) mice under normal diet, a process that is largely aggravated when these mice are exposed to HFD. These data directly demonstrate the interaction of hepatic inflammation, dietary composition, and metabolism in the development of liver tumorigenesis.

From the bench to the clinic and back again: translational biomarker discovery using in silico mining of pharmacogenomic data

To improve drug efficacy and safety and advance medical intervention in diseases, new biomarkers are urgently needed. Pharmacogenomics can provide a tool to discover and begin to qualify biomarkers useful for these indications and is readily applicable to multiple species. One can begin and end with genes or focus on tissue-derived expression analysis of those genes that encode secreted proteins to discover potential biomarkers that can be monitored in body fluids. The paper will discuss issues surrounding such investigations, show examples of translational biomarkers and end with a summary of the US FDA’s work in this field over the last 6 years.

Deregulation of the activin/follistatin system in hepatocarcinogenesis

BACKGROUND/AIMS

Activins A and E negatively regulate hepatic cell number by inhibiting cell replication and inducing apoptosis. Follistatin and follistatin-like 3 bind activins and antagonise their biological activities. Aim of our study was to investigate, whether activins and follistatins may play a role in hepatocarcinogenesis.

METHODS

Expression levels of follistatin, follistatin-like 3, and activin subunits beta(A) as well as beta(E) were investigated in chemically induced rat and human liver tumours by real-time PCR and immunohistochemistry. In addition, the effects of follistatin and activin A on DNA synthesis of normal as well as preneoplastic hepatocytes and hepatoma cells were analysed.

RESULTS

Follistatin was overexpressed while both activin subunits were downregulated in the majority of rat and human liver tumours. Follistatin-like 3 expression was low in normal but enhanced in malignant rat liver. In human normal liver, in contrast, it was abundantly expressed but downregulated in liver cancer. Administration of follistatin to normal and preneoplastic hepatocytes stimulated DNA synthesis preferentially in preneoplastic rat hepatocytes, whereas activin A repressed it.

CONCLUSIONS

The balanced expression of follistatins and activins becomes deregulated during hepatocarcinogenesis. The sensitivity of preneoplastic hepatocytes to activin signals suggests the activin/follistatin system as promising target for therapeutic intervention.

Analysis of gene expression changes in relation to toxicity and tumorigenesis in the livers of Big Blue transgenic rats fed comfrey (Symphytum officinale)

Background

Comfrey is consumed by humans as a vegetable and a tea, and has been used as an herbal medicine for more than 2000 years. Comfrey, however, is hepatotoxic in livestock and humans and carcinogenic in experimental animals. Our previous study suggested that comfrey induces liver tumors by a genotoxic mechanism and that the pyrrolizidine alkaloids in the plant are responsible for mutation induction and tumor initiation in rat liver.

Results

In this study, we identified comfrey-induced gene expression profile in the livers of rats. Groups of 6 male transgenic Big Blue rats were fed a basal diet and a diet containing 8% comfrey roots, a dose that resulted in liver tumors in a previous carcinogenicity bioassay. The animals were treated for 12 weeks and sacrificed one day after the final treatment. We used a rat microarray containing 26,857 genes to perform genome-wide gene expression studies. Dietary comfrey resulted in marked changes in liver gene expression, as well as in significant decreases in the body weight and increases in liver mutant frequency. When a two-fold cutoff value and a P-value less than 0.01 were selected, 2,726 genes were identified as differentially expressed in comfrey-fed rats compared to control animals. Among these genes, there were 1,617 genes associated by Ingenuity Pathway Analysis with particular functions, and the differentially expressed genes in comfrey-fed rat livers were involved in metabolism, injury of endothelial cells, and liver injury and abnormalities, including liver fibrosis and cancer development.

Conclusion

The gene expression profile provides us a better understanding of underlying mechanisms for comfrey-induced hepatic toxicity. Integration of gene expression changes with known pathological changes can be used to formulate a mechanistic scheme for comfrey-induced liver toxicity and tumorigenesis.