Expression of Fas-related genes in human hepatocellular carcinomas

Apoptosis in liver carcinogenesis and chemotherapy

Hepatocellular carcinoma (HCC) is a major health problem. In human hepatocarcinogenesis, the balance between cell death and proliferation is deregulated, tipping the scales for a situation where antiapoptotic signals are overpowering the death-triggering stimuli. HCC cells harbor a wide variety of mutations that alter the regulation of apoptosis and hence the response to chemotherapeutical drugs, making them resistant to the proapoptotic signals. Considering all these modifications found in HCC cells, therapeutic approaches need to be carefully studied in order to specifically target the antiapoptotic signals. This review deals with the recent relevant contributions reporting molecular alterations for HCC that lead to a deregulation of apoptosis, as well as the challenge of death-inducing chemotherapeutics in current HCC treatment.

Role of p38 MAP Kinase Signal Transduction in Solid Tumors

Mitogen-activated protein kinases (MAPKs) mediate a wide variety of cellular behaviors in response to extracellular stimuli. One of the main subgroups, the p38 MAP kinases, has been implicated in a wide range of complex biologic processes, such as cell proliferation, cell differentiation, cell death, cell migration, and invasion. Dysregulation of p38 MAPK levels in patients are associated with advanced stages and short survival in cancer patients (e.g., prostate, breast, bladder, liver, and lung cancer). p38 MAPK plays a dual role as a regulator of cell death, and it can either mediate cell survival or cell death depending not only on the type of stimulus but also in a cell type specific manner. In addition to modulating cell survival, an essential role of p38 MAPK in modulation of cell migration and invasion offers a distinct opportunity to target this pathway with respect to tumor metastasis. The specific function of p38 MAPK appears to depend not only on the cell type but also on the stimuli and/or the isoform that is activated. p38 MAPK signaling pathway is activated in response to diverse stimuli and mediates its function by components downstream of p38. Extrapolation of the knowledge gained from laboratory findings is essential to address the clinical significance of p38 MAPK signaling pathways. The goal of this review is to provide an overview on recent progress made in defining the functions of p38 MAPK pathways with respect to solid tumor biology and generate testable hypothesis with respect to the role of p38 MAPK as an attractive target for intervention of solid tumors.

Altered of apoptotic markers of both extrinsic and intrinsic pathways induced by hepatitis C virus infection in peripheral blood mononuclear cells

Background

Chronic hepatitis C (CHC) has emerged as a leading cause of cirrhosis in the U.S. and across the world. To understand the role of apoptotic pathways in hepatitis C virus (HCV) infection, we studied the mRNA and protein expression patterns of apoptosis-related genes in peripheral blood mononuclear cells (PBMC) obtained from patients with HCV infection.

Methods

The present study included 50 subjects which plasma samples were positive for HCV, but negative for human immunodeficiency virus (HIV) or hepatitis B virus (HBV). These cases were divided into four groups according to METAVIR, a score-based analysis which helps to interpret a liver biopsy according to the degree of inflammation and fibrosis. mRNA expression of the studied genes were analyzed by reverse transcription of quantitative polymerase chain reaction (RT-qPCR) and protein levels, analyzed by ELISA, was also conducted. HCV genotyping was also determined.

Results

HCV infection increased mRNA expression and protein synthesis of caspase 8 in group 1 by 3 fold and 4 fold, respectively (p < 0.05). In group 4 HCV infection increased mRNA expression and protein synthesis of caspase 9 by 2 fold and 1,5 fold, respectively (p < 0.05). Also, caspase 3 mRNA expression and protein synthesis had level augumented by HCV infection in group 1 by 4 fold and 5 fold, respectively, and in group 4 by 6 fold and 7 fold, respectively (p < 0.05).

Conclusions

HCV induces alteration at both genomic and protein levels of apoptosis markers involved with extrinsic and intrinsic pathways.

Expression of apoptosis-related genes in the endometrium of polycystic ovary syndrome patients during the window of implantation

The present study investigated the expression of the apoptosis-related genes fas-associated via death domain (FADD) and Bcl-2 in the endometrium during the window of implantation in polycystic ovary syndrome (PCOS) patients. The aim was to explore the role of cell apoptosis in endometrial receptivity during this period. The subjects were divided into experimental and control group. The experimental group comprised 12 infertile women with PCOS, and the control group comprised 12 women who were infertile because of tubal pathological factors but had normal menstrual cycles. Endometria were collected by biopsy 7d after ovulation. Six samples from each group were randomly selected and subjected to gene chip analyses. The expression of endometrial FADD and Bcl-2 was determined by immunohistochemistry, and cell apoptosis was detected by the TUNEL method. Compared with the control group, 194 differentially expressed genes were found in the PCOS group, 102 of which were upregulated and 92 were downregulated. The differentially expressed genes were divided into 15 types according to function. Among the nine genes related to cell apoptosis, five (including Bcl-2) were upregulated and four were downregulated (including FADD). Bcl-2 expression during the window of implantation in the PCOS group increased compared with the control group, showing a significant difference (P<0.05). FADD expression in the PCOS group notably decreased compared with that in the control group, which also showed a significant difference (P<0.05). Cell apoptosis analysis showed a significant difference between the average apoptotic indices in the PCOS and control groups (P<0.05). Significant differences were observed between the endometrial gene expression in the PCOS and control groups. The decrease in cell apoptosis during the window of implantation in PCOS patients may be one of the causes of the reduced endometrial receptivity.

Mechanisms and biomarkers of apoptosis in liver disease and fibrosis

Liver fibrosis and cirrhosis are a major cause of morbidity and mortality worldwide. Development of the fibrotic scar is an outcome of chronic liver diseases of varying aetiologies including alcoholic liver disease (ALD) nonalcoholic liver disease (NAFLD) including non-alcoholic steatohepatitis (NASH) viral hepatitis B and C (HBV, HCV). The critical step in the development of scar is activation of hepatic stellate cells (HSCs), which become the primary source of extracellular matrix. Aberrant apoptosis is a feature of chronic liver diseases and is associated with worsening stages of fibrosis. However, apoptosis is also the main mechanism promoting the resolution of fibrosis, and spontaneous or targeted apoptosis of HSC is associated with regression of fibrosis in animal models and patients with chronic liver disease. Given the importance of apoptosis in disease progression and resolution, there is much interest in precisely delineating the mechanisms involved and also developing biomarkers that accurately reflect the underlying pathogenesis. Here, we review the mechanisms driving apoptosis in development of liver disease and use of apoptosis -related biomarkers to aid in clinical diagnosis. Finally, we will also examine the recent literature regarding new insights into mechanisms involved in apoptosis of activated HSCs as possible method of fibrosis regression.

Antitumor immunity produced by the liver Kupffer cells, NK cells, NKT cells, and CD8 CD122 T cells

Mouse and human livers contain innate immune leukocytes, NK cells, NKT cells, and macrophage-lineage Kupffer cells. Various bacterial components, including Toll-like receptor (TLR) ligands and an NKT cell ligand (α-galactocylceramide), activate liver Kupffer cells, which produce IL-1, IL-6, IL-12, and TNF. IL-12 activates hepatic NK cells and NKT cells to produce IFN-γ, which further activates hepatic T cells, in turn activating phagocytosis and cytokine production by Kupffer cells in a positive feedback loop. These immunological events are essentially evoked to protect the host from bacterial and viral infections; however, these events also contribute to antitumor and antimetastatic immunity in the liver by activated liver NK cells and NKT cells. Bystander CD8⁺CD122⁺ T cells, and tumor-specific memory CD8⁺T cells, are also induced in the liver by α-galactocylceramide. Furthermore, adoptive transfer experiments have revealed that activated liver lymphocytes may migrate to other organs to inhibit tumor growth, such as the lungs and kidneys. The immunological mechanism underlying the development of hepatocellular carcinoma in cirrhotic livers in hepatitis C patients and liver innate immunity as a double-edged sword (hepatocyte injury/regeneration, septic shock, autoimmune disease, etc.) are also discussed.

Characterization of chronic HCV infection-induced apoptosis

Background

To understand the complex and largely not well-understood apoptotic pathway and immune system evasion mechanisms in hepatitis C virus (HCV)-associated hepatocellular carcinoma (HCC) and HCV associated chronic hepatitis (CH), we studied the expression patterns of a number of pro-apoptotic and anti-apoptotic genes (Fas, FasL, Bcl-2, Bcl-xL and Bak) in HepG2 cell line harboring HCV- genotype-4 replication. For confirmation, we also assessed the expression levels of the same group of genes in clinical samples obtained from 35 HCC and 34 CH patients.

Methods

Viral replication was assessed in the tissue culture medium by RT-PCR, quantitative Real-Time PCR (qRT-PCR); detection of HCV core protein by western blot and inhibition of HCV replication with siRNA. The expression level of Fas, FasL, Bcl-2, Bcl-xL and Bak was assessed by immunohistochemistry and RT-PCR whereas caspases 3, 8 and 9 were assessed by colorimetric assay kits up to 135 days post infection.

Results

There was a consistent increase in apoptotic activity for the first 4 weeks post-CV infection followed by a consistent decrease up to the end of the experiment. The concordance between the changes in the expression levels of Fas, FasL, Bcl-2, Bcl-xL and Bak in vitro and in situ was statistically significant (p < 0.05). Fas was highly expressed at early stages of infection in cell lines and in normal control liver tissues followed by a dramatic reduction post-HCV infection and an increase in the expression level of FasL post HCV infection. The effect of HCV infection on other apoptotic proteins started very early post-infection, suggesting that hepatitis C modulating apoptosis by modulating intracellular pro-apoptotic signals.

Conclusions

Chronic HCV infection differently modulates the apoptotic machinery during the course of infection, where the virus induces apoptosis early in the course of infection, and as the disease progresses apoptosis is modulated. This study could open a new opportunity for understanding the various signaling of apoptosis and in the developing a targeted therapy to inhibit viral persistence and HCC development.

Potential targets for molecular imaging of apoptosis resistance in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most common cancers, which is mainly a concern in Southeast Asia. Apoptosis resistance in HCC is one of the significant factors for hepatocarcinogenesis and tumour progression. Recent advances of apoptosis resistance mechanisms in HCC could serve as potential targets for molecular imaging, which would be of considerable value to explore the molecular processes involved in HCC progression and to evaluate responses of certain anti-HCC therapies. Disruptions in the balance of anti-apoptotic and pro-apoptotic processes have been found to be involved in apoptosis resistance in HCC. Loss of response to death receptors, transformation of growth factor-β induced apoptosis, upregulation of anti-apoptotic Bcl-2 subgroup, as well as downregulation of pro-apoptotic Bax subgroup and BH3-only subgroup, are associated with apoptosis resistance in HCC. Mutation of p53 gene, dysregulation of NF-κB and survivin are also of interest because of their contribution to HCC development. In this review, the aim is to identify potential targets for molecular imaging of apoptosis resistance in HCC.

Cell death and hepatocarcinogenesis: Dysregulation of apoptosis signaling pathways

Hepatocellular carcinoma (HCC) remains a disease with a poor prognosis despite recent advances in the pathophysiology and treatment. Although the disease is biologically heterogeneous, dysregulation of cellular proliferation and apoptosis both occur frequently and contribute to the malignant phenotype. Chronic liver disease is associated with intrahepatic inflammation which promotes dysregulation of cellular signaling pathways; this triggers proliferation and thus lays the ground for expansion of premalignant cells. Cancer emerges when immunological control fails and transformed cells develop resistance against cell death signaling pathways. The same mechanisms underlie the poor responsiveness of HCC towards chemotherapy. Only recently advances in understanding the signaling pathways involved has led to the development of an effective pharmacological therapy for advanced disease. The current review will discuss apoptosis signaling pathways and focus on apoptosis resistance of HCC involving derangements in cell death receptors (e.g. tumor necrosis factor-alpha [TNF], CD95/Apo-1, TNF-related apoptosis-inducing ligand [TRAIL]) and associated adapter molecules (e.g. FADD and FLIP) of apoptotic signaling pathways. In addition, the role of the transcription factor nuclear factor-kappaB (NFκB) and members of the B cell leukemia-2 (Bcl-2) family that contribute to the regulation of apoptosis in hepatocytes are discussed. Eventually, the delineation of cell death signaling pathways could contribute to the implementation of new therapeutic strategies to treat HCC.

Dysregulation of apoptosis in hepatocellular carcinoma cells

Hepatocellular carcinoma (HCC) is a major health problem, being the sixth most common cancer world-wide. Dysregulation of the balance between proliferation and cell death represents a pro-tumorigenic principle in human hepatocarcinogenesis. This review updates the recent relevant contributions reporting molecular alterations for HCC that induce an imbalance in the regulation of apoptosis. Alterations in the expression and/or activation of p53 are frequent in HCC cells, which confer on them resistance to chemotherapeutic drugs. Many HCCs are also insensitive to apoptosis induced either by death receptor ligands, such as FasL or TRAIL, or by transforming growth factor-beta (TGF-β). Although the expression of some pro-apoptotic genes is decreased, the balance between death and survival is dysregulated in HCC mainly due to overactivation of anti-apoptotic pathways. Indeed, some molecules involved in counteracting apoptosis, such as Bcl-X_L, Mcl-1, c-IAP1, XIAP or survivin are over-expressed in HCC cells. Furthermore, some growth factors that mediate cell survival are up-regulated in HCC, as well as the molecules involved in the machinery responsible for cleavage of their pro-forms to an active peptide. The expression and/or activation of the JAK/STAT, PI3K/AKT and RAS/ERKs pathways are enhanced in many HCC cells, conferring on them resistance to apoptotic stimuli. Finally, recent evidence indicates that inflammatory processes, as well as the epithelial-mesenchymal transitions that occur in HCC cells to facilitate their dissemination, are related to cell survival. Therefore, therapeutic strategies to selectively inhibit anti-apoptotic signals in liver tumor cells have the potential to provide powerful tools to treat HCC.

The role of the tumor necrosis factor (TNF)--Fas L and HCV in the development of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a major public health problem in Egypt due to the high prevalence of hepatitis C viral (HCV) infection. The mechanism by which HCV exerts its carcinogenic effect on the liver is not yet understood. Previous research has suggested that perturbations of the Fas-Fas L tumor necrosis system could result in uncontrolled cancerous cell growth in the liver. This study aims to assess the relationship of Fas ligand (Fas L) to HCC. A total of 28 cases (HCC) and 56 controls (28 cirrhosis and 28 chronic hepatitis) were included in the study. Sera and tissue biopsies were tested for HCV antibody and HCV-RNA. Fas ligand expression in tissue was examined immunohistochemically using a rabbit purified polyclonal antibody. Levels of soluble Fas L were determined in serum by ELISA. The HCC cases were graded as: 17.9% Grade I, 32.1% Grade II, 35.7% Grade III and 14.3% were Grade IV. Among the cases, 81% had evidence of cirrhosis. All the cases and controls were positive for HCV-RNA. Tissue and serum PCR results were identical within the same subjects. Fas ligand cytoplasmic expression was more pronounced in HCC than in cirrhosis, and in cirrhosis more than in chronic hepatitis. This expression was higher with increasing grades of malignancy and in tissues adjacent to the tumor, than in those without nearby tumor. Soluble Fas L levels were higher in cases than in controls, with similar results as that of immunohistochemical expression. These results suggest that HCV and Fas ligand play a key role in hepatocarcinogenesis, consistent with the hypothesis that HCV induces overexpression of Fas ligand in the liver cells, resulting in escape from killing by the immune system cells, with subsequent uncontrolled growth of tissue and the development of malignancy.

Prognostic significance of Bcl-xL in human hepatocellular carcinoma

BACKGROUND

Proliferation and apoptosis of liver cancer cells are closely related phenomena. We investigated the correlation between overexpression of Bcl-xL, an anti-apoptosis-related protein of the Bcl-2 family, and the clinical course of hepatocellular carcinoma (HCC).

METHODS

Specimens from 7 HCC patients were used for Western blotting and immunoelectron microscopy tests. Samples from 33 HCC patients who had undergone hepatectomies were used for immunohistochemical staining. The degrees of expression of Bcl-xL and Ki-67, as an index of HCC mitosis severity, were each classified into 2 groups.

RESULTS

With the use of Western blot analysis, enhanced immunoreactivity of Bcl-xL was found in cancerous specimens. Bcl-xL overexpression was found in cancer specimens in 21 of 33 patients (63.6%). The overall survival (P=.019) and disease-free survival (P=.030) rates of the group overexpressing Bcl-xL were definitely poorer. The Ki-67 higher labeling index LI > 10) group had a poorer survival rate (P=.016). There were significant correlations between Bcl-xL and overall survival and disease-free survival. Multivariate analyses revealed that Bcl-xL, tumor size, histologic portal invasion, and histologic metastatic foci were independent prognostic factors for overall survival and disease-free survival.

CONCLUSIONS

These results showed Bcl-xL in HCC specimens, suggesting that Bcl-xL was a significant prognostic factor for disease progression in human HCC.

Bcl-2 and Bcl-xL are important for the induction of paclitaxel resistance in human hepatocellular carcinoma cells

In this study we have investigated the mechanism underlying resistance to the chemotherapeutic drug paclitaxel in tumors of hepatocellular carcinoma (HCC) patients. Treatment with paclitaxel led to potent inhibition of growth of Hep3B hepatoma cells, but did not affect the growth properties of SNU-368 and SNU-398 cell lines that were established from primary HCC tumors. The growth inhibitory effect induced by paclitaxel correlated with levels of intracellular p21 and resulted in cell cycle arrest at the G2/M phase. However, paclitaxel treatment did not alter intracellular p53 levels. Instead, SNU-398 cells express high levels of the anti-apoptotic Bcl-2 and Bcl-x(L) proteins and the level of Bcl-x(L) could be further induced upon paclitaxel treatment. In contrast, Hep3B cells express pro-apoptotic members of the Bcl family and fail to induce Bcl-x(L) upon paclitaxel treatment. Therefore, these results strongly suggest that Bcl-2 and Bcl-x(L) play an important role in mediating resistance to paclitaxel.

Induction of FAS ligand expression in a human hepatoblastoma cell line by HCV core protein

Tumour cells and virus infected cells expressing Fas ligand (FasL) can evade immune surveillance by inducing apoptosis in T cells expressing Fas. In order to characterise a possible role of hepatitis C virus (HCV) core protein in similar mechanisms during HCV infection, we investigated Fas ligand expression and activity in a human hepatoblastoma cell line (HepG2) constitutively expressing this protein. Strong FasL induction was detected by immunoblotting and flow cytometry analysis in the core expressing cell lines Hep39. In contrast, vector transfected cells or cell lines expressing HCV E1-E2 proteins did not show FasL expression. Co-cultivation experiments of Hep39 cells with a Fas-sensitive T cell line indicated that FasL induced by the core protein had apoptotic activity toward target cells. Effect of the core protein on induction of FasL promoter was further examined by co-transfection of HepG2 cells with core-bearing plasmid and a vector in which luciferase gene expression is driven by human FasL promoter. Results of the luciferase assay indicated a positive regulation of FasL promoter by the core protein. In conclusion, HCV core protein plays a role in the induction of functional FasL in hepatoblastoma cell line and apoptosis in a target T cell line expressing Fas. Similar mechanisms may contribute, in vivo, to establishment of chronic infection and development of hepatocellular carcinoma (HCC).

Midkine protects hepatocellular carcinoma cells against TRAIL-mediated apoptosis through down-regulation of caspase-3 activity

BACKGROUND

It is believed that midkine (MK), a heparin-binding growth factor, plays an important role in carcinogenesis. However, the biologic mechanism of MK in hepatocellular carcinoma has not been clarified to date. The objective of the current study was to investigate the antiapoptotic role of MK in a human hepatoma cell line.

METHODS

The human hepatoma cell line HepG2 was used to study the antiapoptotic effect of MK. Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)/actinomycin D (ActD)-induced apoptosis was detected using a 2-(2-methoxy-4-nitrophenyl)-3-(4-nitrophenyl)-5-(2,4-disulphophenyl)-2H-tetrazolium monosodium salt (WST-8) assay, a caspase-3 activity assay, a caspase-8 activity assay, and flow cytometric analysis.

RESULTS

TRAIL had a potent, dose-dependent inductive effect on cell death in HepG2 cells, for which viable cell counts decreased to 6.3% of the control count at a TRAIL concentration of 100 ng/mL in the presence of 500 ng/mL ActD. Flow cytometry was used to demonstrate that apoptosis induced by TRAIL/ActD was in fact the cause of cell death. According to the WST-8 assay, MK pretreatment resulted in the suppression of TRAIL/ActD-mediated apoptosis in HepG2 cells, although cell viability did not increase when HepG2 cells were treated with MK alone. Caspase-3 activity was down-regulated when MK was added, but caspase-8 activity was high in both the absence and presence of MK.

CONCLUSIONS

The results of the current study indicate that MK acts as an antiapoptotic factor in HepG2 cells through the down-regulation of caspase-3 activity.

Involvement of the p38 mitogen-activated protein kinase cascade in hepatocellular carcinoma

BACKGROUND

The mitogen-activated protein kinase (MAPK) cascade is activated in response to various extracellular stimuli. The authors investigated the involvement of the p38 MAPK, a member of the MAPK superfamily, cascade in hepatoma cell lines and in human hepatocellular carcinoma (HCC) tissue specimens.

METHODS

Constitutively active mutant of MAPK kinase 6 (MKK6), which is upstream of p38 MAPK, was transfected into the HepG2 and HuH7 human hepatoma cell lines. The constitutive active mutant was constructed by replacing Ser-189 and Thr-193 with Glu. The growth and death of mutant MKK6-transfected hepatoma cells were analyzed by the WST-1 and sub-G1 assays. The surgically resected livers of 20 HCC patients were divided histologically into tumorous (T) and nontumorous (NT) lesions. p38 MAPK activity was analyzed using in vitro kinase assay and MKK6 activity was measured using Western blot analysis.

RESULTS

Mutant MKK6 transfection increased p38 MAPK activity, cytochrome c release from the mitochondria to the cytosol, and caspase-3 activity, accompanied by apoptosis. In contrast, SB203580, a p38 MAPK-specific inhibitor, prevented MKK6-induced apoptosis in hepatoma cell lines. In the T lesions of 20 HCC parients, p38 MAPK and MKK6 activities were significantly lower compared with NT lesions (P < 0.05). There was a significant positive correlation between p38 MAPK and MKK6 activity (r = 0.507, P < 0.05). Larger tumors (> 20 mm) exhibited lower levels of p38 MAPK and MKK6 activity than did smaller tumors (P < 0.05).

CONCLUSIONS

These findings suggested that reduction of the p38 MAPK cascade may account, in part, for the resistance to apoptosis, leading to the unrestricted cell growth of human HCC.

A dipalmitoyl peptide that binds SH3 domain, disturbs intracellular signal transduction, and inhibits tumor growth in vivo

The Src homology 3 (SH3) domain plays a crucial role in protein-protein interactions during intracellular signal transduction. Blocking the SH3-mediated protein binding may inhibit the corresponding signal transduction, and thus, block the cellular functions. In this study, a peptide that specifically binds to SH3 domain could be introduced into the intracellular region when the peptides were conjugated with dipalmitic acid and appeared to disturb intracellular signaling. The dipalmitoyl peptide appeared to inhibit the phosphorylation of ZAP-70, Lck, and T-cell antigen receptor zeta in Jurkat. Mobilization of the intracellular free calcium induced by anti-CD3 antibody was reduced after treatment with the dipalmitoyl peptide. It was also observed that the dipalmitoyl peptide inhibited cancer cell growth both in vitro and in vivo. These results suggest that the dipalmitoyl peptide that presumably disturbs SH3-mediated signal transduction may have a potent anti-proliferative activity, which would be useful as a potential anti-tumor agent.

Overexpression of the mouse Fas gene in human Hep3B hepatoma cells overcomes their resistance to Fas-mediated apoptosis

BACKGROUND/AIMS

Fas-induced apoptosis is one of the main forms of apoptosis occurring in hepatocytes. We have previously demonstrated that the human hepatoma cell line Hep3B is resistant to Fas-mediated apoptosis. In this study, we investigated whether the human Fas receptor itself, or the Fas transduction pathway was responsible for the resistant phenotype.

METHODS

Clones of Hep3B cells overexpressing the mouse Fas gene (Hep3B(mfas)) were generated by transfection, and apoptosis was studied by (i) chromatin condensation and nuclear fragmentation, (ii) flow cytometry, (iii) DNA fragmentation and (iv) poly (ADP-ribose) polymerase cleavage.

RESULTS

Use of the species-specific and agonistic anti-mFas monoclonal antibody (JO2), showed that the mFas receptor was correctly routed to the plasma membrane of Hep3B(mfas) cells. Using the four above-mentioned criteria, we demonstrated that JO2 triggered mFas-mediated apoptosis of Hep3B(mfas), but not of Hep3B(pCi) cells (transfected with an empty vector).

CONCLUSIONS

Our data show (i) that the Fas signaling pathway can be completed when a functional mFas receptor is expressed in Hep3B cells, and thus, (ii) that the death-inducing signaling complex components and the effector caspases are functional in Hep3B cells. Moreover, they suggest that the Fas subunits are not pre-assembled at the cell membrane before receptor-ligand interaction.

Decreased expression of Bid in human hepatocellular carcinoma is related to hepatitis B virus X protein

As a mitochondrial membrane death ligand, Bid oligomerises Bak to release cytochrome C and its deficiency renders hepatocytes resistant to apoptosis induced by Fas. The Bid level in hepatocellular carcinoma (HCC) is unknown. In this report, we examined the expression of Bid protein and mRNA in HCC cancerous tissues and their corresponding non-cancerous ones. The effect of the hepatitis B x protein (HBx) on the expression of Bid was also evaluated by transfecting hepatoma cells with the HBx gene. The results showed that the expression of Bid was significantly lower in cancerous tissues than that in their corresponding non-cancerous tissues. Immunohistochemical study revealed that Bid molecule was mainly localised in hepato-cytoplasm. Some nuclei were also positive for Bid antigen though to a lesser degree. In vitro experiments demonstrated that the expression of Bid in cells transfected with HBx was significantly lower than that in the cells without HBx transfection. This finding suggests that HBx may play a causative role in the reduction of Bid expression in HCC. This in vitro result is, to some degree, supported by clinical data that all the HCC examined are positive for hepatitis B virus (HBV). We conclude from this data that the expression of Bid in HCC is significantly decreased and the reduction of Bid may result from a mechanism associated with HBx, a major hepatocarcinogenic product from HBV. The imbalance of increased anti-apoptosis and decreased pro-apoptosis seen in HCC is a critical mechanism leading to the uncontrolled growth of tumour cells. Therefore, this study suggests that a deficiency in the expression of Bid may contribute to the development of such an imbalance in HCC.

IFN-gamma induces cell death in human hepatoma cells through a TRAIL/death receptor-mediated apoptotic pathway

We demonstrated the induction of cell death in a hepatoma cell line by IFN-gamma and its possible mechanism. Among the 2 hepatitis B virus (HBV)-associated hepatoma cell lines, SNU-354 and SNU-368, IFN-gamma induced cell death and increased caspase-3 activity in SNU-368 but not in SNU-354. IFN-gamma induced several changes in the mRNA expression level of apoptosis-regulating genes, e.g., increased expression of Fas, caspase-1 and TNF-related apoptosis-inducing ligand (TRAIL). In particular, IFN-gamma potently increased the mRNA expression of TRAIL in both cell lines. However, it did not change the mRNA expression level of death-mediating TRAIL receptors, e.g., DR4 and DR5, which were constitutively expressed in both cell lines. In contrast, the decoy receptor DcR1 was expressed in SNU-354 but not in SNU-368, and its expression level in SNU-354 was increased by IFN-gamma. Another decoy receptor, DcR2, was constitutively expressed in both cell lines; however, its expression level in SNU-368 was decreased by IFN-gamma. In addition, exogenous recombinant TRAIL reduced viability in SNU-368, but not in SNU-354, cells. From these findings, we speculated that TRAIL up-regulation and the subsequent TRAIL-mediated apoptosis serve as a mechanism of IFN-gamma-induced cell death in SNU-368. To confirm this hypothesis, we demonstrated that soluble DR4-Fc fusion protein, a TRAIL pathway inhibitor, inhibited IFN-gamma-induced cell death in SNU-368. Our results demonstrated that IFN-gamma acts as an inducer of cell death through TRAIL-mediated apoptosis.

Contribution of apoptosis and apoptosis-related proteins to the malformation of the primitive intrahepatic biliary system in Meckel syndrome

In the developing liver, the complete or partial persistence of the primitive double-layered cylinder of biliary-type cells that surrounds the branches of portal vein and its mesenchyme gives origin to portal tracts with an increased number of bile duct structures. The term "ductal plate malformation of the liver" was coined to label the insufficient remodeling of the primitive intrahepatic biliary system. Meckel syndrome is an autosomal recessive inherited disease characterized by occipital encephalocele, postaxial polydactyly, diffuse cystic renal dysplasia, and malformation of the ductal plate of the liver. We studied 52 fetuses with Meckel syndrome from five German centers (Berlin, Freiburg, Heidelberg, Mainz, and Marburg). Analysis of apoptosis and cell proliferation (Ki-67) was performed by terminal deoxynucleotide transferase-mediated dUTP nick-end labeling (TUNEL) and immunohistochemistry in the liver of 24 normal fetuses of different gestational ages (14-38 weeks of gestation) and in 14 fetuses with Meckel syndrome (17-38 weeks of gestation). The expression of two apoptosis-related proteins, Fas (a transmembrane cell surface protein involved in the apoptosis) and Bcl-2 (an anti-apoptotic protein), was studied by immunohistochemistry in the liver of 11 normal fetuses of different gestational ages (14-40 weeks of gestation) and in 40 fetuses with Meckel syndrome (16-38 weeks of gestation). In control fetuses, apoptosis rate and cell proliferation were high in the remodeling ductal plate and moderate in the ductal plate and in remodeled bile ducts. During gestation, expression of Fas and Bcl-2 decreased and increased, respectively. The malformed ductal plates in the fetal livers with Meckel syndrome showed a marked decrease in the apoptotic rate and Fas expression and an increase in proliferative activity and Bcl-2 expression in comparison with control fetuses. Furthermore, by linear regression analysis, we found that both proliferation activity and apoptosis rate in the ductal plate malformation of fetuses with Meckel syndrome were practically constant along the gestation. These results, which represent the first systematic study of apoptosis in ductal plate malformation of the liver, indicate that 1) animals harboring the gene defect of Meckel syndrome could be a good model for the study of the abnormal development of the primitive intrahepatic biliary system, 2) a decreased cell turnover occurs in the ductal plate malformation of fetuses with Meckel syndrome, and 3) the increase of Bcl-2 expression contributes to the pathogenesis of the lack of remodeling of ductal plate of the liver in Meckel syndrome.

FADD and TRADD expression and apoptosis in primary hepatocellular carcinoma

AIM: To investigate the clinical features of FADD and TRADD expressions in primary hepatocellular carcinoma (HCC) and to determine their relationship with hepatic apoptosis.

METHODS: FADD and TRADD expressions were detected by immunohisto chemistry and hepatic apoptosis were determined by in situ end-labeling (ISEL).

RESULTS: Ten (25.6%) cases of HCC were detected to express FADD protein. The positive rate in HCC is lower than that in non-cancerous adjacent liver tissues (62.5%) (P ＜ 0.05). In those of grade I-II, 8 (38.1%) cases were FADD positive, while only 2/18 (11.1%) cases of grade III-IV had detectable FADD protein (P ＜ 0.05). No relationship was found between FADD expression and other clinical features, such as gender, age, tumor size, differentiation or metastasis. ISEL positive cells can be seen in all cases of HCC. The hepatic apoptosis was associated with FADD expression as more apoptotic cells were detected in those cases which had moderately to strongly positive FADD, as compared with negative or weak positive FADD cases (P ＜ 0.05). No relationship was found between FADD expression and hepatic apoptosis in non-cancerous adjacent liver tissues. Fifteen of 39 (38.5%) cases of HCC were found positive for TRADD protein, and similar positive rate (37.5%) in non-cancerous adjacent liver tissues (P ＞ 0.05). The expression of TRADD is correlated with HCC differentiation, as only 22.2% of moderately to highly differentiated HCC showed positive TRADD protein, while as high as 52.4% of poorly differentiated HCC had TRADD (P ＜ 0.05). No relationship was found between TRADD expression and gender, age, tumor size or grade or metastasis, although 42.9% of HCC of grade I/II showed positive TRADD which was slightly higher than that of grade III/IV (33.3%, P ＞ 0.05). Hepatic apoptosis was not related to TRADD expression in HCC or non-cancerous adjacent liver tissues.

CONCLUSION: Loss of FADD expression plays an important role in HCC carcinogenesis, and expression of TRADD also contributes to HCC development. The cell apoptosis in HCC is associated with FADD expression. However, the expression of TRADD does not correlate well with hepatic apoptosis in HCC.

Expression of fas ligand in human hepatoma cell lines: role of hepatitis-B virus X (HBX) in induction of Fas ligand

It has been postulated that tumor cells expressing Fas ligand (FasL) can evade immune surveillance by inducing apoptosis in T cells expressing Fas. In this study, we investigated FasL expression in 13 human hepatoma cell lines. Strong FasL expression was detected by reverse transcription-polymerase chain reaction or immunofluorescence in Hep G2.2.15, in which the hepatitis-B-virus (HBV) genome was transfected, and in SNU-354, which showed HBx transcripts. To determine the biological activity of FasL, Hep G2.2. 15 was co-cultured with MOLT-4, T-cell-leukemia cells. Hep G2.2.15 induced apoptosis in MOLT-4 and this was inhibited by the antagonistic anti-Fas antibody, ZB4. For further analysis of the role of HBx in the induction of FasL, PLC/PRF/5 cells were transfected transiently with the HBV genome, or HBx, or the frameshift mutant of HBx. In PLC/PRF/5 cells transfected with the HBV genome or HBx but not in cells transfected with the frameshift mutant of HBx, FasL expression was detected. Our data suggest that HBx plays a role in the induction of FasL in hepatoma cells and in the escape from immune surveillance.

Expression of fas ligand in human hepatoma cell lines: role of hepatitis-B virus X (HBX) in induction of Fas ligand

It has been postulated that tumor cells expressing Fas ligand (FasL) can evade immune surveillance by inducing apoptosis in T cells expressing Fas. In this study, we investigated FasL expression in 13 human hepatoma cell lines. Strong FasL expression was detected by reverse transcription-polymerase chain reaction or immunofluorescence in Hep G2.2.15, in which the hepatitis-B-virus (HBV) genome was transfected, and in SNU-354, which showed HBx transcripts. To determine the biological activity of FasL, Hep G2.2. 15 was co-cultured with MOLT-4, T-cell-leukemia cells. Hep G2.2.15 induced apoptosis in MOLT-4 and this was inhibited by the antagonistic anti-Fas antibody, ZB4. For further analysis of the role of HBx in the induction of FasL, PLC/PRF/5 cells were transfected transiently with the HBV genome, or HBx, or the frameshift mutant of HBx. In PLC/PRF/5 cells transfected with the HBV genome or HBx but not in cells transfected with the frameshift mutant of HBx, FasL expression was detected. Our data suggest that HBx plays a role in the induction of FasL in hepatoma cells and in the escape from immune surveillance.