Unique features of dendritic cells in IFN-gamma transgenic mice: relevance to cancer development and therapeutic implications

Conditional Stat1 ablation reveals the importance of interferon signaling for immunity to Listeria monocytogenes infection

Signal transducer and activator of transcription 1 (Stat1) is a key player in responses to interferons (IFN). Mutations of Stat1 cause severe immune deficiencies in humans and mice. Here we investigate the importance of Stat1 signaling for the innate and secondary immune response to the intracellular bacterial pathogen Listeria monocytogenes (Lm). Cell type-restricted ablation of the Stat1 gene in naïve animals revealed unique roles in three cell types: macrophage Stat1 signaling protected against lethal Lm infection, whereas Stat1 ablation in dendritic cells (DC) did not affect survival. T lymphocyte Stat1 reduced survival. Type I IFN (IFN-I) signaling in T lymphocytes reportedly weakens innate resistance to Lm. Surprisingly, the effect of Stat1 signaling was much more pronounced, indicating a contribution of Stat1 to pathways other than the IFN-I pathway. In stark contrast, Stat1 activity in both DC and T cells contributed positively to secondary immune responses against Lm in immunized animals, while macrophage Stat1 was dispensable. Our findings provide the first genetic evidence that Stat1 signaling in different cell types produces antagonistic effects on innate protection against Lm that are obscured in mice with complete Stat1 deficiency. They further demonstrate a drastic change in the cell type-dependent Stat1 requirement for memory responses to Lm infection.

Signal transducer and activator of transcription 1 (Stat1) is an indispensable component of the cellular response to interferons (IFN) during immune reactions to pathogens. Stat1 deficiency leads to severe immune defects in humans and mice. The sensitivity of animals with complete Stat1 ablation to microbial pathogens prevented determining its contribution to various effector systems of the immune response. By way of tissue-restricted Stat1 ablation we now decipher the impact of Stat1 signaling in different cell populations on the innate and adaptive immune response to the intracellular pathogen Listeria monocytogenes. Our data highlight the importance of and requirement for IFNγ-activated macrophages for clearance of the pathogen during early phases of infection, and show a yet unanticipated detrimental role for T cell Stat1. During secondary responses the picture changes and Stat1 in T cells is crucial for proper clearance of L. monocytogenes. Likewise, Stat1 signaling in dendritic cells plays a fundamental role for adaptive immunity to L. monocytogenes. Exploring the local response to L. monocytogenes infection we reveal a role of Stat1 in shaping the cellular composition of inflammatory infiltrates. Furthermore, Stat1 deficiency in dendritic cells increases the proliferation of regulatory T cells, an effect likely to dampen the antibacterial response.

Autocrine, not paracrine, interferon-gamma gene delivery enhances ex vivo antigen-specific cytotoxic T lymphocyte stimulation and killing

The adoptive transfer of antigen-specific cytotoxic T lymphocytes (CTL) shows promise in the treatment of cancer and infectious diseases. We utilize adeno-associated virus-(AAV-) based antigen gene-loaded dendritic cells (DCs) to stimulate such antigen-specific CTL. Yet further improvements in CTL stimulation and killing may result by gene delivery of various Th1-response interferons/cytokines, such as interferon gamma (IFN-gamma), as the delivered gene can continuously produce that interferon. However which immune cell type should optimally express IFN-gamma is unclear as the phenotypes of both DC and T cells are enhanced by it. Here, we used AAV to compare and contrast IFN-gamma gene delivery into DC or T cells, and versus the addition of exogenous IFN-gamma, for stimulating carcinoembryonic antigen-(CEA-) specific CTL. It was found that AAV/IFN-gamma delivery into T cells (autocrine) resulted in T cell populations with the highest CD8(+)/CD4(+) ratio, highest IFN-gamma(+)/IL-4(+) ratio, highest CD69(+),CD8(+) levels, and lowest CD4(+)/CD25(+) levels, all consistent with the strongest Th1 response. Most importantly, AAV/IFN-gamma transduction of T cells resulted in antigen-specific T cell populations with the highest killing capabilities, 49% above other treatments. These data strongly suggest that AAV/IFN-gamma autocrine gene delivery into T cells is worthy of further study towards maximizing the generation of antigen-specific anticancer CTL killers.

Dendritic cells modified with 6Ckine/IFNgamma fusion gene induce specific cytotoxic T lymphocytes in vitro

BACKGROUND AND OBJECTIVE

[corrected] Dendritic cells play an important role in initiation and regulation of immune responses. Previous studies demonstrated that intratumoral administration of 6Ckine-modified DCs enhanced local and systemic antitumor effects. Herein we report the investigation of the specific CTL responses elicited by adenoviral 6Ckine/IFNgamma fusion gene-modified DCs in vitro.

METHODS

Human monocyte-derived DCs were modified with an adenoviral vector encoding 6Ckine/IFNgamma fusion protein (Ad-6Ckine/IFNgamma), and then investigated the effect of 6Ckine/IFNgamma fusion protein on the maturation, cytokine and chemokine secretion of DCs, and their activities of recruiting and activating T cells in vitro were investigated.

RESULTS

6Ckine/IFNgamma fusion protein induced DC maturation characterized with the upregulation of CD83 and CCR7. And it up-regulated the expression of RANTES and IL-12p70, down-regulated that of IL-10 in DCs. Additionally, 6Ckine/IFNgamma markedly increased DC's recruiting ability for naive T cells, benefiting from the enhanced expression of chemokines 6Ckine and RANTES in DCs. Fusion gene-modified DCs significantly promoted the proliferation of autologous T cells, induced Th1 differentiation by upregulating the expression of IL-2 and T-bet in T cells, and increased specific cytotoxicity of CTLs against specific tumor cells, HepG2 or LoVo cells, respectively.

CONCLUSION

Combining the effects of 6Ckine and IFNgamma, Ad-6Ckine/IFNgamma modified DCs induced enhanced CTL responses in vitro, which indicated that Ad-6Ckine/IFNgamma modified DCs might be used as an adjuvant to trigger an effective antitumor immune response.

Genetic and environmental factors in hereditary predisposition to tumors: a conceptual overview

Cancer is a heritable disorder of somatic cells. Carcinogenesis at the cellular level is like an opened Japanese fan, because initiated cells grow in several directions and tumors suggest the edge of the fan by having many gene abnormalities. We discuss here the primal force and gene networks (federal headship) in renal carcinogenesis. The Eker (Tsc2 mutant) rat model of hereditary renal carcinoma (RC) is an example of a Mendelian dominantly inherited predisposition to a specific cancer in an experimental animal. Recently, we discovered a new hereditary renal carcinoma in the rat in Japan, and the rat was named the "Nihon" rat. We suggest that its predisposing (Bhd) gene is a novel renal tumor suppressor gene. We present these unique models as part of the study of problems in carcinogenesis; e.g., multistep carcinogenesis, cancer prevention and the development of the therapeutic treatments that can be translated to human patients, as well as how environmental factors interact with cancer susceptibility gene(s).

Enhanced antimetastatic effect of fetal liver kinase 1 extracellular domain and interferon-gamma fusion gene-modified dendritic cell vaccination

Antiangiogenic immunotherapy benefits from targeting antigens expressed on genetically stable endothelial cells and represents a novel modality for cancer treatment. Vascular endothelial growth factor (VEGF) receptor 2 (VEGFR2, also known as flk1 in mouse) mediated VEGF signaling is the key rate-limiting step in angiogenesis. Blockade of the flk1 signaling pathway can significantly inhibit tumor cell-induced angiogenesis and lead to inhibition of tumor metastasis. Interferon-gamma (IFN-gamma) is a pleiotropic cytokine, which plays an important role in cell-mediated immunity. In this study, we tested the hypothesis that immunization of mice with soluble flk1 (sflk1) and IFN-gamma fusion gene-transfected dendritic cells (DC-sflk1-IFN-gamma) would induce a potent CTL response to flk1, leading to an inhibition of tumor-induced angiogenesis and metastasis. Our data show that immunization of mice with sflk1 gene-modified DC (DC-sflk1) could induce a CTL response to flk1, leading to profound inhibition of tumor-cell-induced angiogenesis and metastasis. However, more striking antimetastatic effects were achieved through induction of enhanced CTL response to flk1 and augmented inhibition of angiogenesis when mice were immunized with DC-sflk1-IFN-gamma. In vivo T-cell subset depletion experiments showed that CD8(+) T cells were mainly responsible for this antimetastatic effect. Our data extend the notion that DC-based active antiangiogenic immunotherapy is an effective modality for cancer treatment, and show that the antitumor efficacy of this strategy can be improved by combination with DC-based cytokine immunotherapy.

Interferon-gamma is an autocrine mediator for dendritic cell maturation

Maturation of dendritic cells (DC) is critical for efficient antigen presentation and initiation of an immune response. Interferon-gamma (IFN-gamma) is an important Th1 cytokine. In this study, we investigated the role of IFN-gamma in DC maturation using either IFN-gamma receptor deficient- or IFN-gamma overexpression-models. We showed that immature DC generated in vitro from bone marrow (BM) progenitor cells produced low level of IFN-gamma. After LPS stimulation, DC produced more IFN-gamma, and IFN-gamma productions were at comparable levels among C57BL/6 mice-derived DC (C57BL/6 DC), wild-type 129 mice-derived DC (129 DC) and IFN-gamma receptor deficient 129 mice-derived DC (IFN-gammaR-/-DC). We found that IFN-gammaR-/-DC exhibited decreased expression of CD54, CD86, reduced capacity to secrete IL-1beta and IL-12p70, and impaired capacity to stimulate alloreactive T cells and to drive Th1 differentiation. Transfection of IFN-gamma gene into DC promoted DC to express higher CD40, CD54, CD80, CD86, CCR7 and I-Ab, secrete more IL-1beta and IL-12p70, and more potently activate both CD4 and CD8 T cells. These data suggest that IFN-gamma signaling pathway is important for the maturation of DC in an autocrine fashion.

Hereditary renal carcinogenesis fitting Knudson's two-hit model: genotype, environment, and phenotype

Cancer is a heritable disorder of somatic cells. Environment and heredity both operate in the origin of human cancer. The Eker (Tsc2 gene mutant) rat model of hereditary renal carcinoma (RC) is an example of Mendelian dominantly inherited predisposition to a specific cancer in an experimental animal. To the best of our knowledge, this was the first isolation of a Mendelian dominantly predisposing cancer gene in a naturally occurring animal model. Recently, we discovered a new hereditary renal carcinoma in the rat in Japan, and the rat was named the "Nihon" rat, and its predisposing (Nihon) gene could be a novel renal tumor suppressor gene. We present these unique models, comparing these two predisposing genes (both are located on rat chromosome 10), for the study of problems in carcinogenesis, for instance, species-specific difference in tumorigenesis, cell stage and tissue/cell-type specific tumorigenesis, multistep carcinogenesis, modifier gene(s) in renal carcinogenesis, cancer prevention, and the development of the therapeutic treatments that can be translated to human patients, as well as how environmental factors interact with cancer susceptibility gene(s).

Renal carcinogenesis: genotype, phenotype and dramatype

Cancer is a heritable disorder of somatic cells. Environment and heredity are both important in the carcinogenic process. The Eker rat model of hereditary renal carcinoma (RC) is an example of a Mendelian dominantly inherited predisposition to a specific cancer in an experimental animal. Forty years after the discovery of the Eker rat in Oslo, we and Knudson's group independently identified a germline retrotransposon insertion in the rat homologue of the human tuberous sclerosis (TSC2) gene. To our knowledge, this was the first isolation of a Mendelian dominantly predisposing cancer gene in a naturally occurring animal model. Recently, we discovered a new hereditary renal carcinoma in the rat. This rat was named the "Nihon" rat and its predisposing (Nihon) gene could be a novel renal tumor suppressor gene. This article will review the utility of these unique models for the study of problems in carcinogenesis; e.g., species-specific differences in tumorigenesis, cell stage and tissue/cell-type specific tumorigenesis, multistep carcinogenesis, modifier gene(s) in renal carcinogenesis, cancer prevention and the development of therapeutic treatments which can be translated to human patients, as well as how environmental factors interact with cancer susceptibility gene(s).

Cytokines regulate the capacity of CD8alpha(+) and CD8alpha(-) dendritic cells to prime Th1/Th2 cells in vivo

Prior studies have shown that subclasses of dendritic cells (DC) direct the development of distinct Th populations in rodents and in humans. In the mouse, we have recently shown that administration of Ag-pulsed CD8alpha(-) DC induces a Th2-type response, whereas injection of CD8alpha(+) DC leads to Th1 differentiation. To define the DC-derived factors involved in the polarization of Th responses, we injected either subset purified from mice genetically deficient for IFN-gamma, IL-4, IL-12, or IL-10 into wild-type animals. In this work, we report that DC-derived IL-12 and IFN-gamma are required for Th1 priming by CD8alpha(+) DC, whereas IL-10 is required for optimal development of Th2 cells by CD8alpha(-) DC. The level of IL-12 produced by the DC appears to determine the Th1/Th2 balance in vivo. We further show that the function of DC subsets displays some flexibility. Treatment of DC with IL-10 in vitro induces a selective decrease in the viability of CD8alpha(+) DC. Conversely, incubation with IFN-gamma down-regulates the Th2-promoting capacities of CD8alpha(-) DC and increases the Th1-skewing properties of both subsets.

Effect of a cancer vaccine prepared by fusions of hepatocarcinoma cells with dendritic cells

AIM: To prepare a cancer vaccine (H₂₂-DC) expressing high levels of costimulatory molecules based on fusions of hepatocarcinoma cells (H₂₂) with dendritic cells (DC) of mice and to analyze the biological characteristics and induction of specific CTL activity of H₂₂-DC.

METHODS: DCs were isolated from murine spleen by metrizamide density gradient centrifugation, purified based on its characteristics of semi-adhesion to culture plates and FcR^-, and were cultured in the medium containing GM-CSF and IL-4. A large number of DC were harvested. DCs were then fused with H₂₂ cells by PEG and the fusion cells were marked with CD11c MicroBeads. The H₂₂-DC was sorted with Mimi MACS sorter. The techniques of cell culture, immunocytochemistry and light microscopy were also used to test the characteristics of growth and morphology of H₂₂-DC in vitro. As the immunogen, H₂₂-DC was inoculated subcutaneously into the right armpit of BALB/C mice, and their tumorigenicity in vivo was observed. MTT was used to test the CTL activity of murine spleen in vitro.

RESULTS: DC cells isolated and generated were CD11c+ cells with irregular shape, and highly expressed CD80, CD86 and CD54 molecules. H₂₂ cells were CD11c^- cells with spherical shape and bigger volume, and did not express CD80, CD86 and CD54 molecules. H₂₂-DC was CD11c⁺ cells with bigger volume, being spherical, flat or irregular in shape, and highly expressed CD80, CD86 and CD54 molecules, too. H₂₂-DC was able to divide and proliferate in vitro, but its activity of proliferation was significantly decreased as compared with H₂₂ cells and its growth curve was flatter than H₂₂ cells. After subcutaneous inoculation over 60 d, H₂₂-DC showed no tumorigenecity in mice, which was significantly different from control groups (P < 0.01). The spleen CTL activity against H₂₂ cells in mice implanted with fresh H₂₂-DC was significantly higher than control groups (P < 0.01).

CONCLUSION: H₂₂-DC could significantly stimulate the specific CTL activity of murine spleen, which suggests that the fusion cells have already obtained the function of antigen presenting of parental DC and could present H₂₂ specific antigen which has not been identified yet, and H₂₂-DC could induce antitumor immune response; although simply mixed H₂₂ cells with DC could stimulate the specific CTL activity which could inhibit the growth of tumor in some degree, it could not prevent the generation of tumor. It shows that the DC vaccine is likely to become a helpful approach in immunotherapy of hepatocarcinoma.

Peripheral blood T-cell responses to pyruvate dehydrogenase complex in primary biliary cirrhosis: role of antigen-presenting dendritic cells

Patients with primary biliary cirrhosis (PBC) are usually characterized by the presence of antibody to pyruvate dehydrogenase complex (PDC) in the sera and PDC-specific T cells in the liver. However, most of the patients with PBC do not show peripheral blood T cells response to PDC. In this study, we re-evaluated the peripheral blood T cell responses to PDC in PBC using antigen-presenting dendritic cells (DCs). Twenty-four patients with PBC (AMA-positive: 16; AMA-negative: 8) and 13 normal controls were enrolled in the study. Peripheral blood mononuclear cells (PBMC) and highly enriched populations of T cells were stimulated with either only PDC or DCs plus PDC or PDC-pulsed DC plus PDC. Antibodies to different components of PDC were estimated by an immunoblotting technique. PBMC from only one out of ten AMA-positive PBC patients proliferated when cultured with only PDC. However, peripheral blood T cells from ten out of ten AMA-positive PBC patients and three out of ten AMA-negative PBC patients, but none of the five normal controls showed PDC-specific proliferation when cultured with PDC-pulsed DCs. Two of these three AMA-negative PBC patients, although negative for AMA, were positive for antibodies to other components of PDC. PDC-specific T cells are present in the peripheral blood from most of the patients with PBC. This is the first report on the effectiveness of antigen-pulsed DCs for the elucidation of autoantigen-specific immune response in human autoimmune diseases.

Localization and characterization of antigen-presenting dendritic cells in the gastric mucosa of murine and human autoimmune gastritis

BACKGROUND

Activated CD4+ T cells and inflammatory cytokines are implicated in the pathogenesis of experimental autoimmune gastritis. However, there is a paucity of information about the cells that induce them. Antigen-presenting dendritic cells (DCs) play a cardinal role in the formation and survival of activated lymphocytes.

MATERIALS AND METHODS

Autoimmune gastritis was induced in neonatal BALB/c mice by thymectomy. DCs were detected in situ in the gastric mucosa from thymectomized mice and in patients with autoimmune gastritis, by immunohistochemistry and immunoelectron microscopy. The expression of MHC class II and CD86 antigens on DCs in the gastric mucosa and spleen was evaluated in dual-colour flow cytometry.

RESULTS

DCs were detected in the gastric mucosa of mice with autoimmune gastritis, and the number of DCs increased as the levels of gastritis became more severe as time passed following thymectomy. Flow cytometric analyses revealed that more than 60% of the DCs in the gastric mucosa had a mature phenotype (expressed MHC class II and/or CD86 antigens) both at 4 and 16 weeks after thymectomy. Activated and mature DCs were localized in the gastric mucosa from patients with autoimmune gastritis.

CONCLUSIONS

This is the first report on the localization and phenotypes of DCs in the gastric mucosa of autoimmune gastritis. The presence of mature DCs in the gastric mucosa of murine and human autoimmune gastritis, in spite of their absence in the gastric mucosa of normal mice, suggests that mature DCs play a role in the pathogenesis of autoimmune gastritis.