Tumor expression of Fas ligand (CD95L) and the consequences

Neutrophils as immune effector cells in antibody therapy in cancer

Tumor-targeting monoclonal antibodies are available for a number of cancer cell types (over)expressing the corresponding tumor antigens. Such antibodies can limit tumor progression by different mechanisms, including direct growth inhibition and immune-mediated mechanisms, in particular complement-dependent cytotoxicity, antibody-dependent cellular phagocytosis, and antibody-dependent cellular cytotoxicity (ADCC). ADCC can be mediated by various types of immune cells, including neutrophils, the most abundant leukocyte in circulation. Neutrophils express a number of Fc receptors, including Fcγ- and Fcα-receptors, and can therefore kill tumor cells opsonized with either IgG or IgA antibodies. In recent years, important insights have been obtained with respect to the mechanism(s) by which neutrophils engage and kill antibody-opsonized cancer cells and these findings are reviewed here. In addition, we consider a number of additional ways in which neutrophils may affect cancer progression, in particular by regulating adaptive anti-cancer immunity.

Niacin mitigates rumen epithelial damage in vivo by inhibiting rumen epithelial cell apoptosis on a high concentrate diet

To investigate the effects of niacin on rumen fermentation, rumen epithelial antioxidant activity, and rumen epithelial cell apoptosis on high concentrate (HC) diets, nine male Hu sheep were randomly fed one of three diets: low concentrate diet (LC; concentrate: forage (C:F) = 20:80, high concentrate diet (HC; C:F = 80:20), and HCN diet (HC diet + niacin at 800 mg/kg diet air-dry matter). Compared with the LC group, the HC group had a lower rumen pH, higher volatile fatty acids and lactic acid in the rumen, reduced activity of antioxidant enzymes and total antioxidant capacity, and increased malondialdehyde content in the rumen epithelium (P < 0.05). Rumen epithelial papilla morphology was decreased, and apoptosis-related indicators and serum inflammatory cytokines were increased in the HC group over the LC group (P < 0.05). Compared with the HC diet, the HCN diet increased rumen pH, rumen epithelium antioxidant capacity, and rumen epithelial papilla morphology, decreased rumen lactate content, serum inflammatory cytokines, and apoptosis-related indicators (P < 0.05). Therefore, adding 800 mg/kg niacin helped protect against rumen epithelial damage by avoiding drastic changes in the rumen environment and improved rumen epithelial antioxidant capacity to inhibit rumen epithelial cell apoptosis in sheep on a HC diet.

Apoptosis of tumor-infiltrating T lymphocytes: a new immune checkpoint mechanism

Immunotherapy based on checkpoint inhibitors is providing substantial clinical benefit, but only to a minority of cancer patients. The current priority is to understand why the majority of patients fail to respond. Besides T-cell dysfunction, T-cell apoptosis was reported in several recent studies as a relevant mechanism of tumoral immune resistance. Several death receptors (Fas, DR3, DR4, DR5, TNFR1) can trigger apoptosis when activated by their respective ligands. In this review, we discuss the immunomodulatory role of the main death receptors and how these are shaping the tumor microenvironment, with a focus on Fas and its ligand. Fas-mediated apoptosis of T cells has long been known as a mechanism allowing the contraction of T-cell responses to prevent immunopathology, a phenomenon known as activation-induced cell death, which is triggered by induction of Fas ligand (FasL) expression on T cells themselves and qualifies as an immune checkpoint mechanism. Recent evidence indicates that other cells in the tumor microenvironment can express FasL and trigger apoptosis of tumor-infiltrating lymphocytes (TIL), including endothelial cells and myeloid-derived suppressor cells. The resulting disappearance of TIL prevents anti-tumor immunity and may in fact contribute to the absence of TIL that is typical of "cold" tumors that fail to respond to immunotherapy. Interfering with the Fas-FasL pathway in the tumor microenvironment has the potential to increase the efficacy of cancer immunotherapy.

Tumor mechanisms of resistance to immune attack

The immune system plays a key role in the interactions between host and tumor. Immune selection pressure is a driving force behind the sculpting and evolution of malignant cancer cells to escape this immune attack. Several common tumor cell-based mechanisms of resistance to immune attack have been identified and can be broadly categorized into three main classes: loss of antigenicity, loss of immunogenicity, and creation of an immunosuppressive microenvironment. In this review, we will discuss in detail the relevant literature associated with each class of resistance and will describe the relevance of these mechanisms to human cancer patients. To conclude, we will outline the implications these mechanisms have for the treatment of cancer using currently available therapeutic approaches. Immunotherapy has been a successful addition to current treatment approaches, but many patients either do not respond or quickly become resistant. This reflects the ability of tumors to continue to adapt to immune selection pressure at all stages of development. Additional study of immune escape mechanisms and immunotherapy resistance mechanisms will be needed to inform future treatment approaches.

The rationale of vectored gene-fusion vaccines against cancer: evolving strategies and latest evidence

The development of vaccines that target tumor antigens in cancer has proven difficult. A major reason for this is that T cells specific for tumor self-antigens and neoantigens are eliminated or inactivated through mechanisms of tolerance. Antigen fusion strategies which increase the ability of vaccines to stimulate T cells that have escaped tolerance mechanisms, may have a particular potential as immunotherapies. This review highlights antigen fusion strategies that have been successful in stimulating the induction of T-cell immunity against cancer and counteracting tumor-associated tolerance. In preclinical studies, these strategies have shown to improve the potency of vectored vaccines through fusion of tumor antigen to proteins or protein domains that increase CD4+ T-cell help, CD8+ T-cell responses or both the CD4+ and CD8+ T-cell responses. However, in clinical trials such strategies seem to be less efficient when provided as a DNA vaccine. The first clinical trial using a viral vectored fusion-gene vaccine is expected to be tested as a partner in a heterologous prime-boost regimen directed against cervical cancer.

Induction of apoptosis by laminarin, regulating the insulin-like growth factor-IR signaling pathways in HT-29 human colon cells

In recent years, algae have been highlighted as potential sources of anticancer agents. Laminarin is a molecule found in marine brown algae that has potentially beneficial biological activities. However, these activities have not been investigated. In the present study, we examined the effects of laminarin on HT-29 cells and analyzed its effect on the insulin-like growth factor (IGF-IR) signaling pathway. 3-(4,5-Dimethylthiazol-2-yl)-5-(3-carboxymethoxy-phenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) assays revealed that laminarin induced cell death in a dose-dependent manner. Western blotting showed that laminarin decreased mitogen-activated protein kinases (MAPK) and ERK phosphorylation. Decreased proliferation depended on IGF-IR, which was associated with the downregulation of MAPK/ERK. These results are important for understanding the roles of IGF-IR in colon cancer cell tumorigenesis, and suggest that laminarin shows activity against human colon cancer.

Toll-like receptors gene polymorphisms may confer increased susceptibility to breast cancer development

Toll-like receptor (TLR) activation may be an important event in tumor cell immune evasion. TLR2 and TLR4 gene polymorphisms have been related to increased susceptibility to cancer development in various organs. 261 patients and 480 health individuals were investigated for genotype and allelic frequencies of a 22-bp nucleotide deletion (-196 to -174del) in the promoter of TLR2 gene as well as two polymorphisms causing amino acid substitutions (Asp299Gly and Thr399Ile) in TLR4 gene. As far as (-196 to -174del) in TLR2 gene is concerned ins/del and del/del genotypes and del allele were significantly more frequent in breast cancer patients compared to healthy controls. Considering Asp299Gly replacement of TLR4 gene, Gly carriers (Asp/Gly & Gly/Gly genotype) and Gly allele were overrepresented among the breast cancer cases. The -174 to -196del of TLR2 gene and Asp299Gly of TLR4 gene polymorphisms may confer an increased susceptibility to breast cancer development.

Weapons ovarian epithelial tumors may use in immune escape: an immunohistochemical correlational study

Investigate FasL and survivin expression in a series of primary ovarian surface epithelial tumors, correlate their expression with each other, and characterize the presence of CD3+ T-lymphocytes in studied tumors and determine whether their presence correlates with FasL or survivin expression in malignant cases. FasL and survivin expression was assessed in 54 ovarian epithelial tumors. The results were compared between different tumor types and grades. Correlation between both markers' expression in all studied tumors was done. Either marker's expression was compared to the mean CD3+ T-lymphocytes per HPF in the studied malignant tumors. Either FasL or survivin expression was significantly higher in malignant versus benign ovarian epithelial tumors (p < 0.001 for both) and both markers were strongly correlated to each other (r = 0.877 & p < 0.001). Malignant tumors show significantly higher mean CD3+ T-lymphocytes than benign and borderline tumors. The mean CD3+ T-lymphocytes decrease significantly on increasing malignant tumor grade (p = 0.019) and expression of both FasL and survivin (r = -0.729, -0.582, respectively & p < 0.001 for both). The higher expression of FasL and survivin in malignant as compared to benign ovarian tumors suggest that they have a significant role in pathogenesis of ovarian carcinoma. Both markers are strongly correlated to each other and may contribute to immune escape of ovarian carcinoma as their higher expression is associated with decreased number of CD3 + T-lymphocytes.

Toll-like receptor 4 activation in cancer progression and therapy

Cancer immunotherapy has been the focus of intense research since the late 19th century when Coley observed that bacterial components can contribute to cancer regression by eliciting an antitumor immune response. Successful activation and maturation of tumor-specific immune cells is now known to be mediated by bacterial endotoxin, which activates Toll-like receptor 4 (TLR4). TLR4 is expressed on a variety of immune as well as tumor cells, but its activation can have opposing effects. While TLR4 activation can promote antitumor immunity, it can also result in increased tumor growth and immunosuppression. Nevertheless, TLR4 engagement by endotoxin as well as by endogenous ligands represents notable contribution to the outcome of different cancer treatments, such as radiation or chemotherapy. Further research of the role and mechanisms of TLR4 activation in cancer may provide novel antitumor vaccine adjuvants as well as TLR4 inhibitors that could prevent inflammation-induced carcinogenesis.

The role of MAPK-ERK pathway in 67-kDa laminin receptor-induced FasL expression in human cholangiocarcinoma cells

BACKGROUND AND AIMS

Cancer cells are thought to possess immune evasion properties due to FasL overexpression in many types of human tumors. In the present study, we set out to investigate the role of MAPK-ERK pathway in 67-kDa laminin receptor induced FasL expression and FasL-mediated apoptosis in human cholangiocarcinoma cells.

METHODS

The expression of FasL and its promoter activity in cultured cholangiocarcinoma cells were examined after treatment with laminin or transfection with plasmids containing siRNA targeted to 67-kDa laminin receptor. The effects of MAPK-ERK cascade inhibitor and c-Myc inhibition by siRNA on 67-kDa laminin receptor-induced FasL expression were determined. Apoptosis assay was performed to analyze the apoptosis of lymphocytes cocultured with cholangiocarcinoma cells treated with or without MAPK-ERK cascade inhibitor.

RESULTS

Our results revealed that the specific MAPK-ERK cascade inhibitor, PD98059, significantly attenuated phosphorylation of c-Myc on Ser-62 and FasL upregulation in QBC-939 cells and these cells showed decreased cytotoxicity against Fas-sensitive Jurkat T cells. A luciferase reporter assay revealed that FasL promoter activity was significantly reduced in cells treated with PD98059 or transfected with c-Myc siRNA.

CONCLUSIONS

Based on these results, we conclude that 67LR induces FasL expression and cytotoxicity against Fas-sensitive Jurkat T cells in human cholangiocarcinoma cells through the phosphorylation of c-Myc on Ser-62 and the subsequent activation of the FasL promoter through the ERK pathway.

Antitumor effect and mechanisms of arsenic trioxide on subcutaneously implanted human gastric cancer in nude mice

We sought to investigate the efficacy of arsenic trioxide (As(2)O(3)) against a human gastric cell line implanted in nude mice in vivo, as well as the mechanism involved. The solid tumor model was created in nude mice with the gastric cancer cell line SGC-7901. The animals were randomly divided into three groups. As(2)O(3) was injected into animals in two arsenic-treated groups (2.5 mg/kg and 5 mg/kg), and the same volume of saline solution was injected into the control group. The inhibitory effect was observed in every group. Apoptotic cells and apoptotic bodies were observed by transmission electron microscope; the fraction of apoptotic cells was detected by TUNEL (terminal deoxynucleotidyl transferase dUTP nick-end labeling) under laser confocal technology. The expression of Fas and FasL was detected by immunohistochemical staining. In nude mice, after treatment with 5 mg/kg and 2.5 mg/kg As(2)O(3), approximately 50% and 30% tumor growth inhibition were observed, respectively (P < 0.05 for both treatment groups). Increase in apoptotic cells and apoptotic bodies appeared in As(2)O(3)-treated tumors compared with the control group. The fluorescence intensity levels of apoptotic cells in tumor were significantly higher in the arsenic-treated groups (P < 0.05 for both treatment groups). The fluorescence intensity level of apoptotic cells in the 5-mg/kg group was higher than that in the 2.5-mg/kg group (P < 0.05). The expression of Fas protein increased in dose- and time-dependent manner after the treatment with As(2)O(3), but that of FasL protein showed no significant difference between control and treated groups. As(2)O(3) did not induce hepatic and renal system injury in the nude mice. As(2)O(3) can inhibit the growth of human gastric cell implanted tumor. We ascribe this to upregulation of Fas, which can induce apoptosis of gastric cells.

Prognostic significance of Fas expression in retinoblastoma

PURPOSE

The loss of Fas is believed to enhance metastatic spread in diverse human tumors. We studied the expression of Fas by immunohistochemistry in retinoblastomas and correlated the results clinicopathologically.

METHODS

Archival specimens of 76 retinoblastomas were included in this study. The tumors were divided into three groups: Group A (n = 21) comprising tumors with no invasion; Group B (n = 46) tumors with invasion of choroid (diffuse), optic nerve (post-laminar), and orbit; and Group C (n = 9) tumors with both invasion and metastasis. Sections were immunostained with monoclonal antibody CD95 (APO-1/Fas) and the immunoreactivity was assessed.

RESULTS

Negative immunoreactivity of Fas was observed in Group B and Group C tumors (p < 0.001). Poorly differentiated retinoblastomas showed a decreased Fas expression (p = 0.006).

CONCLUSIONS

Decreased expression of Fas is seen in aggressive tumors and tumors that are poorly differentiated. This preliminary observation deserves further investigation, which may then shed more light on the immune escape mechanisms of this tumor and thus enable novel therapeutic strategies.

Killer artificial antigen-presenting cells: a novel strategy to delete specific T cells

Several cell-based immunotherapy strategies have been developed to specifically modulate T cell-mediated immune responses. These methods frequently rely on the utilization of tolerogenic cell-based antigen-presenting cells (APCs). However, APCs are highly sensitive to cytotoxic T-cell responses, thus limiting their therapeutic capacity. Here, we describe a novel bead-based approach to modulate T-cell responses in an antigen-specific fashion. We have generated killer artificial APCs (kappaaAPCs) by coupling an apoptosis-inducing alpha-Fas (CD95) IgM mAb together with HLA-A2 Ig molecules onto beads. These kappaaAPCs deplete targeted antigen-specific T cells in a Fas/Fas ligand (FasL)-dependent fashion. T-cell depletion in cocultures is rapidly initiated (30 minutes), dependent on the amount of kappaaAPCs and independent of activation-induced cell death (AICD). kappaaAPCs represent a novel technology that can control T cell-mediated immune responses, and therefore has potential for use in treatment of autoimmune diseases and allograft rejection.

The influence of different culture microenvironments on the generation of dendritic cells from non-small-cell lung cancer patients

INTRODUCTION

Monocyte-derived dendritic cells (DCs) are currently under extensive evaluation as cell vaccines for cancer treatment. Many protocols regarding DCs generation in vitro with different protein components, especially autologous proteins, have been described. On the other hand, active tumor-derived factors in patients' serum could impair monocytes, which might result in their abrogated differentiation into DCs in vitro.

MATERIALS AND METHODS

Autologous DCs from non-small-cell lung cancer (NSCLC)-bearing patients were generated in different culture microenvironments. Peripheral blood mononuclear cells (PBMCs) were cultured in the presence of interleukin-4 and granulocyte-monocyte-stimulating factor with supplementation of 10% autologous serum, 10% allogenic serum, or 2% human albumin. The course of apoptosis, phagocytic ability, and the immunophenotype of the generated DCs were analyzed using flow cytometric methods.

RESULTS

After 48 h of culture, we found a lower percentage of CD1a+/CD14+ and a higher percentage of CD1a+/CD14(-) cells in the culture supplemented with human albumin than in the cultures supplemented with serums. The lowest CD14 antigen expression was found in the human albumin-supplemented 48-h cultures. After 48 h in the cultures carried out with human albumin we found significantly higher percentages of AV+/PI+ cells and AV(-)/PI+ cells than in cultures supplemented with autologous or allogenic serum. We also noted that the expression of FITC-dextran after 4 and 24 h of incubation was significantly higher in the cultures supplemented with both serums than in the HA-SC. The percentage of semi-mature DCs and of CD83 expression was lowest in the culture supplemented with 2% human albumin.

CONCLUSIONS

The kind of culture supplementation had a great impact on the apoptosis of cultured PBMCs. It could also influence the yield of monocyte-derived DCs. It was also confirmed that autologous and allogenic serums provide suitable microenvironments for the generation of autologous DCs from NSCLC patients. The choice of culture supplementation for DC generation is still unsolved and further studies should be undertaken.

Loss of functional Fas ligand enhances intestinal tumorigenesis in the Min mouse model

Fas ligand (FasL/CD95L), a member of the tumor necrosis factor family, interacts with a specific receptor Fas, ultimately leading to cell death. Tumor expression of FasL has been proposed to aid in immune evasion through a "Fas counterattack" mechanism but has also been described as a proinflammatory factor. Here, we tested the role of FasL in a mouse model of spontaneous tumor development. We used the Min mouse in which multiple benign polyps develop in the intestine due to a mutation in the Apc tumor suppressor gene. Mutant mice deficient in functional FasL, termed gld/gld, were crossed to Min mice to generate tumor-prone animals lacking functional FasL. Comparison of FasL-deficient versus proficient Min mice revealed a significant increase in polyp number in the gld/gld mice. We next assessed immune cell infiltration into adenomas. There was no difference in the number of either lymphocytes or macrophages; however, the number of tumor-infiltrating neutrophils was 3-fold lower in the gld/gld specimens compared with controls. Neutrophil migration in vitro was stimulated by wild-type but not mutant FasL. In a nontumor-bearing colitis model in vivo, neutrophil recruitment to the intestine was also reduced in gld/gld mice. Although the Fas counterattack hypothesis suggests that the absence of FasL would result in increased immune-mediated tumor elimination, the opposite is true in the Min model with lack of functional FasL associated with reduced neutrophil influx and increased tumor development. Thus, the proinflammatory rather than counterattack role of tumor FasL is more relevant.

Expression of p16, CD95, CD95L and Helix pomatia agglutinin in relapsing and nonrelapsing very thin melanoma

BACKGROUND

The incidence of malignant melanoma is increasing worldwide and patients are being diagnosed earlier with thinner primary lesions. Most patients with very thin melanoma (Breslow thickness < 0.76 mm) are cured by surgery but 2-18% relapse locally or with distant metastases.

OBJECTIVES

The objective of this study was to establish potential new prognostic markers in very thin melanoma.

METHODS

We identified a group of subjects with relapsing very thin primary cutaneous melanoma and a matched control group who had not relapsed. We investigated the expression of p16, Helix pomatia agglutinin (HPA), CD95 and CD95 ligand (CD95L) by immunohistochemistry on paraffin-embedded tissue sections from the subject group, their subsequent metastases and the control group.

RESULTS

Reduced p16 expression was significantly associated with relapse in very thin melanoma (P = 0.0129). Loss of p16 expression was also found in 76% of metastases. There was no significant association between HPA, CD95 or CD95L expression and subsequent relapse.

CONCLUSIONS

This work is the first to show a significant loss of p16 in relapsing very thin melanoma.

Ex vivo triggering of T-cell-mediated immune responses by autologous tumor cell vaccine in oral cancer patients

We investigated immunomodulatory activity of autologous tumor cell vaccine from oral cancer patients ex vivo by lymphoproliferation assay and two color flow cytometry. Vaccine treatment lead to 10-fold higher proliferation of lymphocytes compared with the untreated controls. A significant increase in CD69(+) and HLA-DR(+) T-cells was observed in vaccine pulsed cultures compared with untreated (p<0.0001) controls. The frequency of IFN-gamma and IL-2 expressing CD4(+)/CD8(+)T-cell subsets was significantly higher with a concomitant reduction in IL-4 and IL-10 expression in the vaccine-treated group (p<0.0001) compared with the untreated controls. Vaccine treatment further increased T-cell receptor Vbeta3, Vbeta5, and Vbeta8 usage. It seems that the autologous tumor cell vaccine triggers T-cell responses ex vivo, hence it may have a protective role in oral cancer patients.

Triggering of T cell-mediated immune responses by allogenic tumor cell vaccine in patients with oral cancer

We investigated the immunomodulatory activity of allogenic whole tumor cell vaccine in oral cancer patients in vitro by two-color flow cytometry. Vaccine treatment significantly increased the expression of CD69 and HLA-DR in CD3+ T-cell subsets. The frequency of Interferon-gamma and Interleukin (IL)-2 expressing CD4+/CD8+ T-cell subsets was significantly higher with a concomitant reduction in IL-4 and IL-10 expressing T-cells in the vaccine treated group as compared with the untreated controls. Vaccine treatment significantly increased T-cell receptor (TCR), Vbeta3, Vbeta5 and Vbeta8 usage. The results indicate that the allogenic whole tumor cell vaccine is able to trigger T-cell mediated immunity in patients with intraoral squamous cell carcinoma.

Inhibition of the phosphatidylinositol 3'-kinase pathway promotes autocrine Fas-induced death of phosphatase and tensin homologue-deficient prostate cancer cells

Rationally designed therapeutics that target the phosphatidylinositol 3'-kinase (PI3K) cell survival pathway are currently in preclinical and clinical development for cancer therapy. Drugs targeting the PI3K pathway aim to inhibit proliferation, promote apoptosis, and enhance chemosensitivity and radiosensitivity of cancer cells. The phosphatase and tensin homologue (PTEN) phosphatidylinositol 3'-phosphatase is a key negative regulator of the PI3K pathway. Inactivation of the PTEN tumor suppressor results in constitutive activation of the PI3K pathway and is found in approximately 50% of advanced prostate cancers, which correlates with a high Gleason score and poor prognosis. Inhibition of the PI3K pathway leads to apoptosis of prostate cancer cells; however, the precise mechanism by which this occurs is unknown. Here we report that apoptotic cell death of PTEN-deficient LNCaP and PC3 prostate cancer cells induced by the PI3K inhibitor LY294002 can be abrogated by disrupting Fas/Fas ligand (FasL) interactions with recombinant Fas:Fc fusion protein or FasL neutralizing antibody (Nok-1), or by expressing dominant-negative Fas-associated death domain. Furthermore, we find that apoptosis induced by expression of wild-type PTEN, driven by a tetracycline-inducible expression system in LNCaP cells, can be inhibited by blocking Fas/FasL interaction using Fas:Fc or Nok-1. These data show that apoptosis induced by blockade of the PI3K pathway in prostate tumor cells is mediated by an autocrine Fas/FasL apoptotic mechanism and the Fas apoptotic pathway is both necessary and sufficient to mediate apoptosis by PI3K inhibition.

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.

Tumor counterattack: fact or fiction?

Cancer development relies on a variety of mechanisms that facilitate tumor growth despite the presence of a functioning immune system. Understanding these mechanisms may foster novel therapeutic approaches for oncology and organ transplantation. By expression of the apoptosis-inducing protein CD95L (FasL, APO-1L, CD178), tumors may eliminate tumor-infiltrating lymphocytes and suppress anti-tumor immune responses, a phenomenon called "tumor counterattack". On the one hand, preliminary evidence of tumor counterattack in human tumors exists, and CD95L expression can prevent T-cell responses in vitro. On the other hand, CD95L-expressing tumors are rapidly rejected and induce inflammation in mice. Here, we summarize and discuss the consequences of CD95L expression of tumor cells and its contribution to immune escape.

Targeted immunotherapy in acute myeloblastic leukemia: from animals to humans

Immunity against acute myeloid leukemia (AML) is demonstrated in humans by the graft-versus-leukemia effect in allogeneic hematopoietic stem cell transplantation. Specific leukemic antigens have progressively been discovered and circulating specific T lymphocytes against Wilms tumor antigen, proteinase peptide or fusion-proteins produced from aberrant oncogenic chromosomal translocations have been detected in leukemic patients. However, due to the fact that leukemic blasts develop various escape mechanisms, antileukemic specific immunity is not able to control leukemic cell proliferation. The aim of immunotherapy is to overcome tolerance and boost immunity to elicit an efficient immune response against leukemia. We review different immunotherapy strategies tested in preclinical animal models of AML and the human trials that spurred from encouraging results obtained in animal models, demonstrate the feasibility of immunotherapy in AML patients.

Squamous cell carcinoma of the lower lip: FAS/FASL expression, lymphocyte subtypes and outcome

Squamous cell carcinoma (SCC) of the lip is a relatively common malignancy of the head and neck region. Tumour thickness, grading and perineural invasion are significant prognostic indicators. However, there is still the need of new reliable biological markers able to predict the prognosis of the single cases with an unfavourable biological behaviour unpredictable by the classic clinical-pathological parameters. 32 cases of (SCC) of the lower lip were analysed for their clincopathologic features, and immunohistochemical expression of Fas/FasL in neoplastic cells and in inflammatory infiltrate. Moreover the density and phenotype of tumour-infiltrating lymphocytes (TIL) were analysed. The results were related with the follow-up of the patients ranging from 2 to 6 years. The cases with over-expression of Fas/FasL in neoplastic cells and Fas+ in T cells preferentially showed a more aggressive clinical behaviour (P<0.01). Moreover we found an alteration of the normal expression of CD4 and CD8 lymphocyte types in ten cases. This data suggest that the Fas/FasL pathway is involved in the close relation between neoplastic cells and T cells and so in the biological behaviour of these tumours.

Alcohol in hepatocellular cancer

Hepatocellular cancer accounts for almost half a million cancer deaths a year, with an escalating incidence in the Western world. Alcohol has long been recognized as a major risk factor for cancer of the liver and of other organs including oropharynx, larynx, esophagus, and possibly the breast and colon. There is compelling epidemiologic data confirming the increased risk of cancer associated with alcohol consumption, which is supported by animal experiments. Cancer of the liver associated with alcohol usually occurs in the setting of cirrhosis. Alcohol may act as a cocarcinogen, and has strong synergistic effects with other carcinogens including hepatitis B and C, aflatoxin, vinyl chloride, obesity, and diabetes mellitus. Acetaldehyde, the main metabolite of alcohol, causes hepatocellular injury, and is an important factor in causing increased oxidant stress, which damages DNA. Alcohol affects nutrition and vitamin metabolism, causing abnormalities of DNA methylation. Abnormalities of DNA methylation, a key pathway of epigenetic gene control, lead to cancer. Other nutritional and metabolic effects, for example on vitamin A metabolism, also play a key role in hepatocarcinogenesis. Alcohol enhances the effects of environmental carcinogens directly and by contributing to nutritional deficiency and impairing immunological tumor surveillance. This review summarizes the epidemiologic evidence for the role of alcohol in hepatocellular cancer, and discusses the mechanisms involved in the promotion of cancer.

CD95L mediates tumor counterattack in vitro but induces neutrophil-independent tumor rejection in vivo

Many tumors express CD95L (CD178, FasL, APO-1L) and may thus kill tumor-infiltrating lymphocytes, a phenomenon called tumor counterattack. However, presently it is not clear whether tumor counterattack is a relevant immune escape mechanism. To characterize the effect of CD95L expression of tumor cells on tumor-specific T cells, we established an in vitro system with TCR tg T cells and a model tumor antigen. Preactivated antitumor T cells were able to kill CD95L(-) and CD95L(+) tumor cells. CD95L(+) tumor cells killed activated T cells in vitro and inhibited the expansion of cytotoxic antitumor T cells in mixed lymphocyte tumor reactions. In vivo CD95L expression led to delayed tumor growth or complete tumor rejection. Neutrophils were not responsible for the delayed growth of the CD95L(+) tumors tested. In mice with neutrophils deficient for important cytotoxicity mechanisms (p47phox(-/-) or iNOS(-/-) mice), CD95L(+) tumors grew similarly as in wild-type mice. Incidence and growth rate of CD95L(+) tumors in mice injected with a neutrophil-depleting or an isotype control antibody was the same. In CD95-deficient lpr mice, tumor growth was not altered as compared to wild-type mice. Taken together, CD95L mediated tumor counterattack in vitro, but led to neutrophil-independent tumor rejection in vivo.

Synergistic induction of the Fas (CD95) ligand promoter by Max and NFkappaB in human non-small lung cancer cells

Fas (CD95/APO-1) ligand is a member of the Tumor Necrosis Factor family and a potent inducer of apoptosis. Fas ligand is expressed in activated T cells and represents a major cytotoxic effector mechanism by which T cells kill their target cells. Activation-induced Fas ligand expression in T cells is under the stringent control of various transcription factors, including nuclear factor kappaB (NFkappaB) and c-Myc/Max. There is accumulating evidence that Fas ligand is also expressed by various non-hematopoietic tumor cells, however, little is known about Fas ligand regulation in tumor cells. In this study, we have analyzed the regulation of the Fas ligand gene promoter induction in two non-small cell lung cancer cell lines, with a major focus on the role of the c-Myc/Max transcription factor. Our results revealed that inhibition of c-Myc/Max did not substantially reduce basal levels of Fas ligand promoter activity, nor did overexpression of c-Myc significantly induce promoter activity. In contrast, we observed that overexpression of Max resulted in a marked increase in basal promoter activity and synergistically enhanced phorbolester- and doxorubicin-induced NFkappaB-mediated Fas ligand promoter activity. These results were confirmed by analyzing endogenous Fas ligand transcription. We conclude that high levels of Max and stress-induced NFkappaB activation may result in elevated expression of Fas ligand in human lung cancer cells and possibly contribute to Fas ligand-associated immune escape mechanisms.

An interferon-gamma ELISPOT and immunohistochemical investigation of cytotoxic T lymphocyte-mediated tumour immunity in patients with paraneoplastic cerebellar degeneration and anti-Yo antibodies

Eight patients with paraneoplastic cerebellar degeneration (PCD) and anti-Yo antibodies were investigated to determine whether there is any association between cytotoxic T lymphocyte (CTL) responses reactive with two previously defined Yo-derived, HLA-A2.1 restricted epitopes (cdr2-1 and cdr2-2) and the presence of tumour-infiltrating CD8+ CTLs. cdr2-1 and cdr2-2-specific CTL responses could not be detected in 5 HLA-A2.1(+) patients in an ex vivo interferon-gamma ELISPOT assay and only 2/9 tumour sections contained CD8(+) intratumoural lymphocytes suggesting a very limited role for CTL-mediated tumour immunity in this patient group, all of whom had evidence of widespread malignancy at the time of diagnosis and/or death.

Prognostic Impact of Fas Ligand on Hepatocellular Carcinoma after Hepatectomy

The expression of Fas ligand on tumor cells may counterattack the host's immunity and worsen the prognosis. Knowledge of the prognostic impact of Fas ligand on patients with hepatocellular carcinoma (HCC) after hepatectomy is still limited. Fas ligand expression in HCCs was examined in 59 patients who underwent hepatectomy for HCC. The prognosis was analyzed and correlated to the expression of Fas ligand. Expression of Fas ligand was detected by immunohistochemical staining in 27 of the 59 HCCs (45.8%). The Fas ligand was expressed in only a small number of cancer cells. However, even though only a few cancer cells expressed it, the prognosis for patients whose HCCs showed Fas ligand expression was worse than that for patients with an HCC without Fas ligand expression. The mean disease-free survival was only 10.83 +/- 1.90 months when HCCs expressed Fas ligand compared with 43.51 +/- 7.02 months for those without Fas ligand expression ( p = 0.0007). The overall patient survival was 28.34 +/- 4.08 months when the HCC expressed Fas ligand compared with 55.31 +/- 5.37 months for HCC without Fas ligand expression ( p = 0.0003). The expression of Fas ligand did not correlate with the presentation of other prognostic factors. Fas ligand expression is thus an independent prognostic factor for HCC. Thus the HCC expressing Fas ligand has a worse prognosis than the HCC without Fas ligand expression.

Tolerance and cancer: mechanisms of tumor evasion and strategies for breaking tolerance

The development of malignant disease might be seen as a failure of immune surveillance. However, not all tumors are naturally immunogenic, and even among those that are immunogenic, the uncontrolled rapid growth of a tumor may sometimes out-run a robust immune response. Nevertheless, recent evidence suggests that mechanisms of tolerance that normally exist to prevent autoimmune disease may also preclude the development of an adequate antitumor response and that tumors themselves have the ability to thwart the development of effective immune responses against their antigens. A major challenge has been to develop approaches to breaking this tolerance in tumor-bearing hosts, and recent advances in our understanding of antigen presentation and tolerance have led to some promising strategies. An alternative approach is to use T cells from nontumor-bearing, allogeneic hosts in the form of lymphocyte infusions, with or without hematopoietic cell transplantation. Immunotherapy may occur in this setting via the response of nontolerant, tumor antigen-specific T cells from nontumor-bearing hosts or via the powerful destructive effect of an alloresponse directed against antigens shared by malignant cells in the recipient. Approaches to exploiting this beneficial effect without the deleterious consequence of graft-versus-host disease in allogeneic hematopoietic cell recipients are discussed.

Function and regulation of the CD95 (APO-1/Fas) ligand in the immune system

CD95/CD95L mediated apoptosis is an important mechanism of immune homeostasis. It is instrumental for termination of an immune response and mainly be involved in peripheral tolerance. Dysregulation of the CD95/CD95L system leads to severe diseases. In this review, we present a survey of the role of the CD95/CD95L system in the immune system and, particularly, focus on the signals and transcription factors (NF-AT, Egr, NF-kappaB, AP-1, c-Myc, Nur77, IRFs, SP-1, ALG-4, ROR(gamma)t, and CIITA) involved in CD95L expression. It should also be evident from this review that a profound insight into the molecular mechanisms of CD95L activation should allow to explore potential therapeutic means to treat CD95/CD95L-dependent diseases.

Altered Expression of FAS System Is Related to Adverse Clinical Outcome in Stage I-II Breast Cancer Patients Treated with Adjuvant Anthracycline-Based Chemotherapy

PURPOSE

To determine the prognostic value of Fas receptor and Fas ligand (FasL) as apoptosis-related biomarkers in the context of chemoresponsiveness in breast cancer (BC) patients submitted to anthracycline-based adjuvant therapy.

EXPERIMENTAL DESIGN

Fas and FasL were investigated by immunohistochemistry in surgical samples collected from 167 stage I-IIa-b BC patients enrolled in a prospective clinical trial using epirubicin plus cyclophosphamide in the adjuvant setting.

RESULTS

Fas and FasL were significantly associated with tumor stage (P < 0.0001). Multivariate analysis indicated that stage, loss of Fas (relative risk, 8.5 and 9.12; P < 0.0001) and FasL up-regulation (relative risk, 2.38 and 2.88; P = 0.01) were independent prognostic variables influencing both disease-free survival (DFS) and overall survival (OS). A Cox analysis using a four-category Fas/FasL phenotype (+/-, +/+, -/+, -/-) as a stratification factor evidenced a highly positive association between Fas/FasL phenotype and the cumulative hazard of relapse and death in the entire series of patients. We also estimated the DFS and OS for different combinations of the pathological-tumor-node-metastasis (TNM) stage and Fas/FasL by using the K sample log-rank exact test demonstrating that significantly shorter DFS and OS were observed in Fas-negative and FasL-positive patients in both stage I-IIa and IIb.

CONCLUSIONS

Data presented herein demonstrated that, according to a number of in vitro studies, the prognosis for BC patients receiving adjuvant anthracycline-based chemotherapy strongly depends on the Fas/FasL status. Therefore, a concomitant altered pattern of Fas/FasL expression seems to configure an aggressive tumor phenotype linked to disease progression.

Natural killer cells and cancer

Natural killer (NK) cells are lymphocytes that were first identified for their ability to kill tumor cells without deliberate immunization or activation. Subsequently, they were also found to be able to kill cells that are infected with certain viruses and to attack preferentially cells that lack expression of major histocompatibility complex (MHC) class I antigens. The recent discovery of novel NK receptors and their ligands has uncovered the molecular mechanisms that regulate NK activation and function. Several activating NK cell receptors and costimulatory molecules have been identified that permit these cells to recognize tumors and virus-infected cells. These are modulated by inhibitory receptors that sense the levels of MHC class I on prospective target cells to prevent unwanted destruction of healthy tissues. In vitro and in vivo, their cytotoxic ability can be enhanced by cytokines, such as interleukin (IL)-2, IL-12, IL-15 and interferon alpha/beta (IFN-alpha/beta). In animal studies, they have been shown to play a critical role in the control of tumor growth and metastasis and to provide innate immunity against infection with certain viruses. Following activation, NK cells release cytokines and chemokines that induce inflammatory responses; modulate monocyte, dendritic cells, and granulocyte growth and differentiation; and influence subsequent adaptive immune responses. The underlining mechanism of discriminating tumor cells and normal cells by NK cells has provided new insights into tumor immunosurveillance and has suggested new strategies for the treatment of human cancer.

Fas/FasL expression in tumor biopsies: a prognostic response factor to fluoropyrimidines?*

Various studies suggested that cytotoxicity induced by 5-fluorouracil (5-FU) is an apoptotic mechanism possibly mediated by the Fas/FasL system. In this preliminary work, we studied retrospectively the role the Fas/FasL expression as a predictive response factor with fluoropyrimidine-based chemotherapies. We developed a real-time PCR method for measuring Fas and FasL expression in various biopsies from patients treated with a FUFOL-like protocol. No correlation was found between Fas or FasL expression and overall survival or partial response. However, the PCR assay was simple and convenient to use for quantitation of Fas/FasL in tumor biopsies.

Fas ligand is not constitutively expressed in low-grade B-cell lymphoma and B-lymphoblastoid cells

The Fas ligand (FasL) pathway is one of the two major effector mechanisms of T-cell-mediated cell death. FasL expression by extralymphatic tissues is thought to maintain a status of immunity. Accordingly, it has been proposed that tumor cells express FasL as a mechanism of immunologic escape. However, data regarding FasL expression in normal or neoplastic tissues remain controversial. In the present study, we investigated the expression of FasL in normal peripheral blood B lymphocytes or malignant cells of the B-lymphocyte lineage to elucidate a possible immunologic counterattack mechanism. FasL gene expression was analyzed by reverse transcriptase polymerase chain reaction in two non-Hodgkin's lymphoma (NHL) entities: the highly aggressive Burkitt's lymphoma (BL) and indolent NHL chronic lymphocytic leukemia (CLL). FasL expression was found to be consistently negative in all BL cell lines and purified samples from patients with CLL. FasL is not constitutively expressed in normal peripheral blood or neoplastic B lymphocytes making the Fas counterattack, as described for gastrointestinal cancer, unlikely as a mechanism of immunologic escape of lymphoma cells.

Tracking death dealing by Fas and TRAIL in lymphatic neoplastic disorders: pathways, targets, and therapeutic tools

In the past decade, it was concluded from a number of investigations that death domain-containing members of the tumor necrosis factor-receptor (TNF-R) family and their ligands such as Fas/FasL and TNF-related apoptosis-inducing ligand (TRAIL)-R/TRAIL are essential for maintaining an intact immune system for surveillance against infection and cancer development and that nondeath domain-containing members such as CD30 or CD40 are involved in the fine tuning of this system during the selection process of the lymphatic system. In line with this conclusion are the observations that alterations in structure, function, and regulation of these molecules contribute to autoimmunity and cancer development of the lymphoid system. Besides controlling size and function of the lymphoid cell pool, Fas/FasL and TRAIL-R/TRAIL regulate myelopoiesis and the dendritic cell functions, and severe alterations of these lineages during the outgrowth and expansion of the lymphoid tumors have been reported. It is the aim of this review to summarize what is currently known about the complex role of these two death receptor/ligand systems in normal, disturbed, and neoplastic hemato-/lymphopoiesis and to point out how such knowledge can be used in developing novel, therapeutic options and the problems that will have to be faced along the way.

Fas ligand on tumor cells mediates inactivation of neutrophils

The expression of Fas ligand (FasL) on tumor cells (tumor FasL) has been implicated in their evasion of immune surveillance. In this study, we investigated the cellular mechanism for FasL-associated immune escape using melanoma B16F10-derived cells as a model. Transfectants carrying FasL-specific ribozymes expressed low levels of FasL (FasL(low) tumor cells) as compared with those carrying enhanced green fluorescent protein-N1 plasmids (FasL(high) tumor cells). When injected s.c. into C57BL/6 mice, FasL(low) tumor cells grew more slowly than did FasL(high) melanoma cells. FasL(high) tumor cells showed more intensive neutrophilic infiltration accompanied by multiple necrotizing areas than did FasL(low) tumor cells. The average size of FasL(low) tumors, but not of FasL(high) tumors, was significantly enhanced in mice depleted of neutrophils. Consistently, a local injection of LPS to recruit/activate neutrophils significantly delayed tumor formation by FasL(low) tumor cells, and slightly retarded that of FasL(high) tumor cells in both C57BL/6 and nonobese diabetic/SCID mice. Neutrophils killed FasL(low) melanoma cells more effectively than FasL(high) melanoma cells in vitro. The resistance of FasL(high) melanoma cells to being killed by neutrophils was correlated with impaired neutrophil activation, as demonstrated by reductions in gelatinase B secretion, reactive oxygen species production, and the surface expression of CD11b and the transcription of FasL. Local transfer of casein-enriched or PMA-treated neutrophils delayed tumor formation by melanoma cells. Taken together, inactivation of neutrophils by tumor FasL is an important mechanism by which tumor cells escape immune attack.

Characterization of antigen processing machinery and Survivin expression in tonsillar squamous cell carcinoma

BACKGROUND

There is a statistically significant association between human leukocyte antigen (HLA) Class I antigen expression and improved prognosis for some patients. This association reflects the control of tumor growth by HLA Class I antigen-restricted, tumor-associated antigen-specific cytolytic T cells. However, progression of other malignant diseases is not associated with the loss of HLA expression. These observations show that the poor prognosis of a subset of tumors, despite high HLA Class I antigen expression, may reflect the development of alternative mechanisms utilized by tumor cells to escape from immune recognition and destruction.

METHODS

The authors evaluated the possible correlation between the expression of the antiapoptosis gene, Survivin, HLA Class I, and progression of tonsillar squamous cell carcinomas (TSCC) lesions. Tissue microarrays were constructed from primary TSCC, metastatically involved lymph nodes, adjacent normal mucosa, and tonsillar parenchyma excised for nonmalignant conditions.

RESULTS

Immunoperoxidase staining of tissue sections demonstrated that Survivin expression is significantly higher (P < 0.001) in malignant tumors than in normal tissue samples. In addition, Survivin expression is significantly higher (P = 0.05) in metastatic than in primary lesions. Survivin expression in primary lesions correlated positively with delta (P = 0.025), tapasin (P = 0.028), and HLA Class I antigen (P = 0.006) expression. The expression patterns of delta, tapasin, HLA Class I antigen, beta-2-microglobulin, and Survivin did not demonstrate any significant association with the clinical course of disease.

CONCLUSIONS

For TSCC that maintain the expression of HLA Class I antigen, overexpression of Survivin may provide an alternative explanation for tumor progression.

T-cell immune responses in the brain and their relevance for cerebral malignancies

In order that cellular immune responses afford protection without risk to sensitive normal tissue, they must be adapted to individual tissues of the body. Nowhere is this more critical than for the brain, where various passive and active mechanisms maintain a state of immune privilege that can limit high magnitude immune responses. Nevertheless, it is now clear that immune responses are induced to antigens in the brain, including those expressed by cerebral malignancies. We discuss hypotheses of how this can occur, although details such as which antigen presenting cells are involved remain to be clarified. Antitumor responses induced spontaneously are insufficient to eradicate malignant astrocytomas; many studies suggest that this can be explained by a combination of low level immune response induction and tumor mediated immunosuppression. A clinical objective currently pursued is to use immunotherapy to ameliorate antitumour immunity. This will necessitate a high level immune response to ensure sufficient effector cells reach the tumor bed, focused cytotoxicity to eradicate malignant cells with little collateral damage to critical normal cells, and minimal inflammation. To achieve these aims, priority should be given to identifying more target antigens in astrocytoma and defining those cells present in the brain parenchyma that are essential to maintain antitumour effector function without exacerbating inflammation. If we are armed with better understanding of immune interactions with brain tumor cells, we can realistically envisage that immunotherapy will one day offer hope to patients with currently untreatable neoplastic diseases of the CNS.

Cancer immunotherapy: the past, the present and the future

One of the most controversial issues in immunology for over a century has been whether an effective immune response can be elicited against malignant tumours. Whether the immunology community has believed cancer immunotherapy is feasible or impossible has been largely determined by the prevailing immunological paradigms at that time. In fact, during the last 110 years it is possible to trace at least five dramatic fluctuations in attitude towards cancer immunotherapy. It now appears, however, that overwhelming evidence is available to support the view that both the innate and adaptive immune responses can recognize and eliminate tumours. On the other hand, it remains to be seen if these immune responses can be harnessed to control cancer as, at the time of diagnosis, many tumours have already been immunoselected to be highly resistant to immune elimination. Based on these observations it is argued that immunotherapy approaches, other than the generation of tumour-specific cytotoxic T lymphocytes, must be explored. Alternative strategies include recruiting tumouricidal myeloid cells into tumours, generating antiangiogenic immune responses and directing innate immunity to hypoxia-induced ligands on tumour cells.

Cross-talk between tumor cells and neutrophils through the Fas (APO-1, CD95)/FasL system: human glioma cells enhance cell viability and stimulate cytokine production in neutrophils

Many tumor cells are resistant to Fas-mediated killing, which has been primarily used as a mechanism to evade immune attack. In this study, we found a new action of Fas on tumors where activation of the Fas signal may force tumor cells to produce survival factors for neutrophils. Human peripheral circulating neutrophils in coculture with glioma cells showed significant delays in spontaneous apoptosis. Interleukin (IL)-6 and IL-8 partially mediated the glioma cell-associated, protective effect on neutrophils. The Fas agonistic antibody CH-11 dose-dependently stimulated the expression of IL-6 and IL-8 in glioma cells. Accordingly, blocking the Fas/FasL interaction reduced IL-6 and IL-8 production in glioma cells and impaired their protective effect on neutrophils. Coculture with glioma cells also affected the expression of cytokines in neutrophils, including IL-8, interferon-gamma, and tumor necrosis factor alpha to various extents. Collectively, our results demonstrate bi-directional cross-talk between tumor and immune cells. Although Fas activation alone cannot induce apoptosis in tumor cells, it may potentially initiate an effective anti-tumor response through a circumvented mechanism.

Fas ligand breaks tolerance to self-antigens and induces tumor immunity mediated by antibodies

The role of Fas ligand (FasL) in programmed cell death via interaction with its receptor Fas is well characterized. It has been proposed that expression of FasL can confer immune privilege to some organs, allowing them to kill infiltrating lymphocytes and inflammatory cells. However, a number of studies have shown that when tumors or transplants express FasL, rejection often occurs as a consequence of proinflammatory functions of FasL. Here we demonstrate that FasL elicits tumor immunity in a murine melanoma model with weak immunogenicity and low expression of major histocompatibility complex (MHC) class I. We show that protected mice recognize melanocyte differentiation self-antigens. Importantly, tumor immunity is mediated by antibodies, as it can be transferred by serum from protected mice.

Hepatitis B virus X protein induced expression of interleukin 18 (IL-18): a potential mechanism for liver injury caused by hepatitis B virus (HBV) infection

BACKGROUND/AIMS

The hepatitis B virus X protein (HBx), a major viral transactivator, is implicated in hepatic inflammation, since it induces many pro-inflammatory cytokines at transcriptional level. The aim of this study was to investigate role of HBx in expression of interleukin 18 (IL-18), a newly identified cytokine that up-regulates Fas ligand (FasL) expression.

METHODS

Chang X-34 that expressing HBx under the control of a doxycycline-inducible promoter, and hepatitis B virus (HBV)-integrated hepatoma cell lines were examined for IL-18 expression by Northern and Western blotting analysis. To test the role of IL-18 produced by hepatoma cells, FasL expression was examined by flow cytometry after treatment with neutralizing anti-IL-18 antibodies. Further, IL-18 expression was examined in the liver tissues of HBx-transgenic mice.

RESULTS

Induction of IL-18 following HBx expression in Chang X-34 and the pattern of IL-18 expression in HBV-integrated cell lines, implicated that HBx transcriptionally induces IL-18 expression. Neutralizing anti-IL-18 antibodies blocked the expression of FasL, suggesting that IL-18 plays a critical role in FasL expression. Further, IL-18 expression in the HBx-transgenic liver, was correlated with the degree of hepatitis.

CONCLUSIONS

Our results demonstrated that HBx induces IL-18 expression in liver, which may be associated with hepatic injury by amplifying FasL expression during HBV infection.

Cells behaving badly: a theoretical model for the Fas/FasL system in tumour immunology

One proposed mechanism of tumour escape from immune surveillance is tumour up-regulation of the cell surface ligand FasL, which can lead to apoptosis of Fas receptor (Fas) positive lymphocytes. Based upon this 'counterattack', we have developed a mathematical model involving tumour cell-lymphocyte interaction, cell surface expression of Fas/FasL, and their secreted soluble forms. The model predicts that (a) the production of soluble forms of Fas and FasL will lead to the down-regulation of the immune response; (b) matrix metalloproteinase (MMP) inactivation should lead to increased membrane FasL and result in a higher rate of Fas-mediated apoptosis for lymphocytes than for tumour cells. Recent studies on cancer patients lend support for these predictions. The clinical implications are two-fold. Firstly, the use of broad spectrum MMP inhibitors as anti-angiogenic agents may be compromised by their adverse effect on tumour FasL up-regulation. Also, Fas/FasL interactions may have an impact on the outcome of numerous ongoing immunotherapeutic trials since the final common pathway of all these approaches is the transduction of death signals within the tumour cell.

Granulocytes mediates the Fas-L-associated apoptosis during lung metastasis of melanoma that determines the metastatic behaviour

The survival of tumour cells in a new tissue environment is crucial for tumour metastasis. Factors contributing to the death of tumour cells during metastasis are not completely understood. In murine melanoma model, activation of Fas (CD95, APO-1) signal in tumour cells reduces their lung metastasis potential, which may be associated with an induction of apoptosis in tumours. To elucidate the cellular mechanism, we used a Fas-ligand (Fas-L) specific ribozyme (Fas-L(ribozyme)) to suppress the expression of Fas-L but not Fas or TNF-alpha in B16F10 melanoma cells. The Fas-L(ribozyme)-carrying cells grew slightly faster in vitro with better viability than controls. Suppression of Fas-L in B16F10 melanoma cells by Fas-L(ribozyme) enhanced lung metastasis of the cells in C57BL/6 mice, and that was correlated with reductions in both apoptotic tumour cells and granulocytic infiltration. Mice depleted of granulocytes, but not CD4+ and CD8+ cells, showed a greatly elevated susceptibility to lung metastasis. Moreover, apoptosis in tumour cells was significantly reduced in granulocyte-depleted mice during the course of tumour formation. Taken together, our findings indicate that Fas-L-associated apoptosis in tumour cells determines the metastasis behaviour of melanoma in the lung and this apoptosis is primarily mediated by the cytotoxicity of recruited granulocytes.