Therapeutic effect of alpha-galactosylceramide-loaded dendritic cells genetically engineered to express SLC/CCL21 along with tumor antigen against peritoneally disseminated tumor cells

Development of Immune Cell Therapy Using T Cells Generated from Pluripotent Stem Cells

In the field of cancer immunotherapy, the effectiveness of a method in which patient-derived T cells are genetically modified ex vivo and administered to patients has been demonstrated. However, problems remain with this method, such as (1) time-consuming, (2) costly, and (3) difficult to guarantee the quality. To overcome these barriers, strategies to regenerate T cells using iPSC technology are being pursued by several groups in the last decade. The authors have been developing a method by which specific TCR genes are introduced into iPSCs and T cells are generated from those iPSCs (TCR-iPSC method). At present, our group is preparing this approach for clinical trial, where iPSCs provided from the iPSC project are transduced with WT1 antigen-specific TCR that had been already clinically tested, and killer T cells are generated from such TCR-iPSCs, to be administered to acute myeloid leukemia patients. While the adoptive T cell therapies have been mainly directed to be used in cancer immunotherapy, it is possible to apply these approaches to viral infections. Strategies by other groups to regenerate various types of T cells from iPSCs will also be introduced.

Future prospects for cancer immunotherapy using induced pluripotent stem cell-derived dendritic cells or macrophages

Cancer immunotherapy is now the first-line treatment for many unresectable cancers. However, it remains far from a complete cure for all patients. Therefore, it is necessary to develop innovative methods for cancer immunotherapy, and immune cell therapy could be an option. Currently, several institutions are attempting to generate immune cells from induced pluripotent stem cells (iPSCs) for use in cancer immunotherapy. A method for generating dendritic cells (DCs) and macrophages (MPs) from iPSC has been established. iPSC-derived DCs (iPS-DCs) can activate T cells via antigen presentation, and iPSC-derived macrophages (iPS-MPs) attack cancer. Since iPSCs are used as the source, genetic modification is easy, and various immune functions, such as the production of anti-tumour cytokines, can be added. Furthermore, when iPS-DCs and iPS-MPs are immortalized, cost reduction through mass production is theoretically possible. In this review, the achievements of cancer research using iPS-DCs and iPS-MPs are summarized, and the prospects for the future are discussed.

CCR7 as a therapeutic target in Cancer

The CCR7 chemokine axis is comprised of chemokine ligand 21 (CCL21) and chemokine ligand 19 (CCL19) acting on chemokine receptor 7 (CCR7). This axis plays two important but apparently opposing roles in cancer. On the one hand, this axis is significantly engaged in the trafficking of a number of effecter cells involved in mounting an immune response to a growing tumour. This suggests therapeutic strategies which involve potentiation of this axis can be used to combat the spread of cancer. On the other hand, the CCR7 axis plays a significant role in controlling the migration of tumour cells towards the lymphatic system and metastasis and can thus contribute to the expansion of cancer. This implies that therapeutic strategies which involve decreasing signaling through the CCR7 axis would have a beneficial effect in preventing dissemination of cancer. This dichotomy has partly been the reason why this axis has not yet been exploited, as other chemokine axes have, as a therapeutic target in cancer. Recent report of a crystal structure for CCR7 provides opportunities to exploit this axis in developing new cancer therapies. However, it remains unclear which of these two strategies, potentiation or antagonism of the CCR7 axis, is more appropriate for cancer therapy. This review brings together the evidence supporting both roles of the CCR7 axis in cancer and examines the future potential of each of the two different therapeutic approaches involving the CCR7 axis in cancer.

α-GalCer and iNKT Cell-Based Cancer Immunotherapy: Realizing the Therapeutic Potentials

NKT cells are CD1d-restricted innate-like T cells expressing both T cell receptor and NK cell markers. The major group of NKT cells in both human and mice is the invariant NKT (iNKT) cells and the best-known function of iNKT cells is their potent anti-tumor function in mice. Since its discovery 25 years ago, the prototype ligand of iNKT cells, α-galactosylceramide (α-GalCer) has been used in over 30 anti-tumor clinical trials with mostly suboptimal outcomes. To realize its therapeutic potential, numerous preclinical models have been developed to optimize the scheme and strategies for α-GalCer-based cancer immunotherapies. Nevertheless, since there is no standard protocol for α-GalCer delivery, we reviewed the preclinical studies with a focus on B16 melanoma model in the goal of identifying the best treatment schemes for α-GalCer treatment. We then reviewed the current progress in developing more clinically relevant mouse models for these preclinical studies, most notably the generation of new mouse models with a humanized CD1d/iNKT cell system. With ever-emerging novel iNKT cell ligands, invention of novel α-GalCer delivery strategies and significantly improved preclinical models for optimizing these new strategies, one can be hopeful that the full potential of anti-tumor potential for α-GalCer will be realized in the not too distant future.

The novel agonistic iNKT-cell antibody NKT14m induces a therapeutic antitumor response against B-cell lymphoma

Invariant natural killer T (iNKT) cells are a small population of T lymphocytes that expresses an invariant T cell receptor with a unique specificity for glycolipid antigens. Their activation using the glycolipid α-galactosylceramide (α-GalCer) triggers innate and adaptive immune responses. The use of α-GalCer in preclinical models as a single antitumor treatment showed moderate effect, but its efficacy in cancer patients was less effective. In addition, this glycolipid induces long-term iNKT-cell anergy precluding the possibility of retreatment. Recently, the first murine iNKT-cell agonistic antibody, NKT14m, has been developed. Here, we analyzed, for the first time, the antitumor efficacy of NKT14m in a B-cell lymphoma model. In a therapeutic setting, a single dose of NKT14m had a moderate antitumor efficacy that was associated with an increase of IFN-γ producing iNKT cells even after a second dose of the NKT14m antibody. Importantly, the combination of a single dose of NKT14m with cyclophosphamide had a potent antitumor efficacy and long-lasting immunity in vivo. Our findings provide the first evidence of the in vivo antitumor efficacy of NKT14m antibody, showing that, either alone or in combination with chemotherapy, induces an effective antitumor response. These results open new opportunities for iNKT-cell mediated immunotherapy to treat B-cell lymphoma.

Natural Killer T Cells in Cancer Immunotherapy

Natural killer T (NKT) cells are specialized CD1d-restricted T cells that recognize lipid antigens. Following stimulation, NKT cells lead to downstream activation of both innate and adaptive immune cells in the tumor microenvironment. This has impelled the development of NKT cell-targeted immunotherapies for treating cancer. In this review, we provide a brief overview of the stimulatory and regulatory functions of NKT cells in tumor immunity as well as highlight preclinical and clinical studies based on NKT cells. Finally, we discuss future perspectives to better harness the potential of NKT cells for cancer therapy.

Innate immune cells for immunotherapy of autoimmune and cancer disorders

Modulation of the immune system has been widely targeted for the treatment of several immune-related diseases, such as autoimmune disorders and cancer, due to its crucial role in these pathologies. Current available therapies focus mainly on symptomatic treatment and are often associated with undesirable secondary effects. For several years, remission of disease and subsequently recovery of immune homeostasis has been a major goal for immunotherapy. Most current immunotherapeutic strategies are aimed to inhibit or potentiate directly the adaptive immune response by modulating antibody production and B cell memory, as well as the effector potential and memory of T cells. Although these immunomodulatory approaches have shown some success in the clinic with promising therapeutic potential, they have some limitations related to their effectiveness in disease models and clinical trials, as well as elevated costs. In the recent years, a renewed interest has emerged on targeting innate immune cells for immunotherapy, due to their high plasticity and ability to exert a potent and extremely rapid response, which can influence the outcome of the adaptive immune response. In this review, we discuss the immunomodulatory potential of several innate immune cells, as well as they use for immunotherapy, especially in autoimmunity and cancer.

Enhancement of Adjuvant Functions of Natural Killer T Cells Using Nanovector Delivery Systems: Application in Anticancer Immune Therapy

Type I natural killer T (NKT) cells have gained considerable interest in anticancer immune therapy over the last decade. This “innate-like” T lymphocyte subset has the unique ability to recognize foreign and self-derived glycolipid antigens in association with the CD1d molecule expressed by antigen-presenting cells. An important property of these cells is to bridge innate and acquired immune responses. The adjuvant function of NKT cells might be exploited in the clinics. In this review, we discuss the approaches currently being used to target NKT cells for cancer therapy. In particular, we highlight ongoing strategies utilizing NKT cell-based nanovaccines to optimize immune therapy.

Dendritic cells combined with tumor cells and α-galactosylceramide induce a potent, therapeutic and NK-cell dependent antitumor immunity in B cell lymphoma

Background

Invariant natural killer T (iNKT) cells are a small population of lymphocytes with unique specificity for glycolipid antigens presented by non-polymorphic CD1d receptor on dendritic cells (DCs). iNKT cells play a central role in tumor immunology since they are implicated in the coordination of innate and adaptive immune responses. These cells can be activated with the prototypic lipid α-galactosylceramide (α-GalCer), stimulating interferon gamma (IFN-γ) production and cytokine secretion, which contribute to the enhancement of T cell activation.

Methods

We evaluated the antitumor effect of a combination of dendritic cells (DCs) and tumor cells with the iNKT cell agonist α-GalCer in a therapeutic model of B cell lymphoma. iNKT, NK and T cell phenotype was determined by flow cytometry. Serum cytokines were analyzed by Luminex technology. Significant differences between survival curves were assessed by the log-rank test. For all other data, Mann–Whitney test was used to analyze the differences between groups.

Results

This vaccine induced a potent (100% survival), long-lasting and tumor-specific antitumor immune response, that was associated with an increase of both Th1 cytokines and IFN-γ secreting iNKT cells (4.59 ± 0.41% vs. 0.92 ± 0.12% in control group; p = 0.01) and T cells (CD4 IFN-γ⁺: 3.75 ± 0.59% vs. 0.66 ± 0.18% p = 0.02; CD8 IFN-γ⁺: 10.61 ± 0.84% vs. 0.47 ± 0.03% p = 0.002). Importantly, natural killer (NK) cells played a critical role in the antitumor effect observed after vaccination.

Conclusions

This study provides clinically relevant data for the development of iNKT-cell based immunotherapy treatments for patients with B cell malignancies.

Generation of mouse pluripotent stem cell-derived proliferating myeloid cells as an unlimited source of functional antigen-presenting cells

The use of dendritic cells (DC) to prime tumor-associated antigen-specific T-cell responses provides a promising approach to cancer immunotherapy. Embryonic stem cells (ESC) and induced pluripotent stem cells (iPSC) can differentiate into functional DCs, thus providing an unlimited source of DCs. However, the previously established methods of generating practical volumes of DCs from pluripotent stem cells (PSC) require a large number of PSCs at the start of the differentiation culture. In this study, we generated mouse proliferating myeloid cells (pMC) as a source of antigen-presenting cells (APC) using lentivirus-mediated transduction of the c-Myc gene into mouse PSC-derived myeloid cells. The pMCs could propagate almost indefinitely in a cytokine-dependent manner, while retaining their potential to differentiate into functional APCs. After treatment with IL4 plus GM-CSF, the pMCs showed impaired proliferation and differentiated into immature DC-like cells (pMC-DC) expressing low levels of major histocompatibility complex (MHC)-I, MHC-II, CD40, CD80, and CD86. In addition, exposure to maturation stimuli induced the production of TNFα and IL12p70, and enhanced the expression of MHC-II, CD40, and CD86, which is thus suggestive of typical DC maturation. Similar to bone marrow-derived DCs, they stimulated a primary mixed lymphocyte reaction. Furthermore, the in vivo transfer of pMC-DCs pulsed with H-2K(b)-restricted OVA257-264 peptide primed OVA-specific cytotoxic T cells and elicited protection in mice against challenge with OVA-expressing melanoma. Overall, myeloid cells exhibiting cytokine-dependent proliferation and DC-like differentiation may be used to address issues associated with the preparation of DCs.

Optimization of natural killer T cell-mediated immunotherapy in cancer using cell-based and nanovector vaccines

α-Galactosylceramide (α-GalCer) represents a new class of immune stimulators and vaccine adjuvants that activate type I natural killer T (NKT) cells to swiftly release cytokines and to exert helper functions for acquired immune responses. This unique property prompted clinicians to exploit the antitumor potential of NKT cells. Here, we review the effects of α-GalCer in (pre)clinics and discuss current and future strategies that aim to optimize NKT cell-mediated antitumor therapy, with a particular focus on cell-based and nanovector vaccines.

Chemokine-based immunotherapy: delivery systems and combination therapies

A major role of chemokines is to mediate leukocyte migration through interaction with G-protein-coupled receptors. Various delivery systems have been developed to utilize the chemokine properties for combating disease. Viral and mutant viral vectors expressing chemokines, genetically modified dendritic cells with chemokine or chemokine receptors, engineered chemokine-expressing tumor cells and pDNA encoding chemokines are among these methods. Another approach for inducing a targeted immune response is fusion of a targeting antibody or antibody fragment to a chemokine. In addition, chemokines induce more effective antitumor immunity when used as adjuvants. In this regard, chemokines are codelivered along with antigens or fused as a targeting unit with antigenic moieties. In this review, several chemokines with their role in inducing immune response against different diseases are discussed, with a major emphasis on cancer.

Development of feeder-free culture systems for generation of ckit+sca1+ progenitors from mouse iPS cells

Patient-specific therapeutic cells derived from induced pluripotent stem (iPS) cells may bypass the ethical issues associated with embryonic stem (ES) cells and avoid potential immunological reactions associated with allogenic transplantation. It is critical, for the ultimate clinical applicability of iPS cell-derived therapies, to establish feeder-free cultures that ensure efficient differentiation of iPS cells into therapeutic progenitors. It is also necessary to understand if iPS cell-derived progenitors differ from those derived from ES cells. In this study, we compared the efficiency of three different feeder-free cultures for differentiating mouse iPS cells into ckit+sca1+ hematopoietic progenitor cells (HPCs) and compared how differentiation and functionality varies between ES and iPS cells. Our results indicated that both iPS and ES cells can be efficiently differentiated into HPCs in suspension cultures supplemented with secretion factors from mouse bone marrow stromal cells (OP9-DL1 conditioned medium). The functionality of these cells was demonstrated by differentiation into CD11c+ dendritic cells (DCs). Both ES and iPS-derived DCs expressed activation molecules (CD86, CD80) in response to LPS stimulation and stimulated T cell proliferation in a mixed lymphocyte reaction (MLR). Extensive quantitative RT-PCR studies were used to study the differences in gene expression profiles of ckit+sca1+ cells generated from the various culture systems as well as differences between ES-derived and iPS-derived cells. We conclude that a feeder-free system using stromal conditioned medium can efficiently generate HPCs as well as functional DCs from iPS cells and the generated cells have similar gene expression profile as those from ES cells.

Generation of dendritic cells and macrophages from human induced pluripotent stem cells aiming at cell therapy

This report describes generation of dendritic cells (DCs) and macrophages from human induced pluripotent stem (iPS) cells. iPS cell-derived DC (iPS-DC) exhibited the morphology of typical DC and function of T-cell stimulation and antigen presentation. iPS-DC loaded with cytomegalovirus (CMV) peptide induced vigorous expansion of CMV-specific autologous CD8+ T cells. Macrophages (iPS-MP) with activity of zymosan phagocytosis and C5a-induced chemotaxis were also generated from iPS cells. Genetically modified iPS-MPs were generated by the introduction of expression vectors into undifferentiated iPS cells, isolation of transfectant iPS cell clone and subsequent differentiation. By this procedure, we generated iPS-MP expressing a membrane-bound form of single chain antibody (scFv) specific to amyloid β (Aβ), the causal protein of Alzheimer's disease. The scFv-transfectant iPS-MP exhibited efficient Aβ-specific phagocytosis activity. iPS-MP expressing CD20-specific scFv engulfed and killed BALL-1 B-cell leukemia cells. Anti-BALL-1 effect of iPS-MP in vivo was demonstrated in a xeno-transplantation model using severe combined immunodeficient mice. In addition, we established a xeno-free culture protocol to generate iPS-DC and iPS-MP. Collectively, we demonstrated the possibility of application of iPS-DC and macrophages to cell therapy.

Pluripotent stem cells as source of dendritic cells for immune therapy

Dendritic cells (DC) are the most potent antigen-presenting cells. In vivo transfer of antigen-bearing DC has proven efficient in priming T cell responses specific to the antigen. DC-based cellular vaccination is now regarded as a powerful means for immunotherapy, especially for anti-cancer immunotherapy. Clinical trials of therapy with DC pulsed with peptide antigens or genetically modified to present antigens are currently carried out in many institutions. In addition, antigen-specific negative regulation of immune response by DC is considered to be a promising approach for treatments of autoimmune diseases and also for regulation of allo-reactive immune response causing graft rejection and GVHD in transplantation medicine. DC for transfer therapy are now generated by in vitro differentiation of peripheral blood monocytes of the patients. However, there is a limitation in the number of available monocytes, and the DC-differentiation potential of monocytes varies depending on the blood donor. Embryonic stem (ES) cells possess both pluripotency and infinite propagation capacity. We consider ES cells to be an ideal source for DC to be used in immunotherapy. Several groups, including us, have developed methods to generate DC from ES cells. This review introduces the studies on generation, characterization, and genetic modification of DC derived from ES cells or induced pluripotent stem (iPS) cells. The issues to be resolved before clinical application of pluripotent stem cell-derived DC will also be discussed.

Characterization of dendritic cells and macrophages generated by directed differentiation from mouse induced pluripotent stem cells

Methods have been established to generate dendritic cells (DCs) from mouse and human embryonic stem (ES) cells. We designated them as ES-DCs and mouse models have demonstrated the induction of anti-cancer immunity and prevention of autoimmune disease by in vivo administration of genetically engineered ES-DCs. For the future clinical application of ES-DCs, the histoincompatibility between patients to be treated and available human ES cells and the ethical concerns associated with human ES cells may be serious obstacles. However, recently developed induced pluripotent stem (iPS) cell technology is expected to resolve these issues. This report describes the generation and characterization of DCs derived from mouse iPS cells. The iPS cell-derived DCs (iPS-DCs) possessed the characteristics of DCs including the capacity of T-cell-stimulation, antigen-processing and presentation and cytokine production. DNA microarray analyses revealed the upregulation of genes related to antigen-presenting functions during differentiation into iPS-DCs and similarity in gene expression profile in iPS-DCs and bone marrow cell-derived DCs. Genetically modified iPS-DCs expressing antigenic protein primed T-cells specific to the antigen in vivo and elicited efficient antigen-specific anti-tumor immunity. In addition, macrophages were generated from iPS cells (iPS-MP). iPS-MP were comparable with bone marrow cell-derived macrophages in the cell surface phenotype, functions, and gene expression profiles.

Multiple antigen-targeted immunotherapy with alpha-galactosylceramide-loaded and genetically engineered dendritic cells derived from embryonic stem cells

Numerous tumor-associated antigens (TAA) have been identified and their use in immunotherapy is considered to be promising. For TAA-based immunotherapy to be broadly applied as standard anticancer medicine, methods for active immunization should be improved. In the present study, we demonstrated the efficacy of multiple TAA-targeted dendritic cell (DC) vaccines and also the additive effects of loading alpha-galactosylceramide to DC using mouse melanoma models. On the basis of previously established methods to generate DC from mouse embryonic stem cells (ES-DC), 4 kinds of genetically modified ES-DC, which expressed the melanoma-associated antigens, glypican-3, secreted protein acidic and rich in cysteine, tyrosinase-related protein-2, or gp100 were generated. Anticancer effects elicited by immunization with the ES-DC were assessed in preventive and also therapeutic settings in the models of peritoneal dissemination and spontaneous metastasis to lymph node and lung. The in vivo transfer of a mixture of 3 kinds of TAA-expressing ES-DC protected the recipient mice from melanoma cells more effectively than the transfer of ES-DC expressing single TAA, thus demonstrating the advantage of multiple as compared with single TAA-targeted immunotherapy. Loading ES-DC with alpha-galactosylceramide further enhanced the anticancer effects, suggesting that excellent synergic effects of TAA-specific cytotoxic T lymphocytes and natural killer T cells against metastatic melanoma can be achieved by using genetically modified ES-DC. With the aid of advancing technologies related to pluripotent stem cells, induced pluripotent stem cells, and ES cells, clinical application of DC highly potent in eliciting anticancer immunity will be realized in the near future.

Activation of antigen-specific cytotoxic T lymphocytes by beta 2-microglobulin or TAP1 gene disruption and the introduction of recipient-matched MHC class I gene in allogeneic embryonic stem cell-derived dendritic cells

A method for the genetic modification of dendritic cells (DC) was previously established based on the in vitro differentiation of embryonic stem (ES) cells to DC (ES-DC). The unavailability of human ES cells genetically identical to the patients will be a problem in the future clinical application of this technology. This study attempted to establish a strategy to overcome this issue. The TAP1 or beta(2)-microglobulin (beta(2)m) gene was disrupted in 129 (H-2(b))-derived ES cells and then expression vectors for the H-2K(d) or beta(2)m-linked form of K(d) (beta2m-K(d)) were introduced, thus resulting in two types of genetically engineered ES-DC, TAP1(-/-)/K(d) ES-DC and beta(2)m(-/-)/beta(2)m-K(d) ES-DC. As intended, both of the transfectant ES-DC expressed K(d) but not the intrinsic H-2(b) haplotype-derived MHC class I. Beta(2)m(-/-)/beta(2)m-K(d) and TAP1(-/-)/K(d) ES-DC were not recognized by pre-activated H-2(b)-reactive CTL and did not prime H-2(b) reactive CTL in vitro or in vivo. Beta(2)m(-/-)/beta(2)m-K(d) ES-DC and TAP1(-/-)/K(d) ES-DC had a survival advantage in comparison to beta(2)m(+/-)/beta(2)m-K(d) ES-DC and TAP1(+/+)/K(d) ES-DC, when transferred into BALB/c mice. K(d)-restricted RSV-M2-derived peptide-loaded ES-DC could prime the epitope-specific CTL upon injection into the BALB/c mice, irrespective of the cell surface expression of intrinsic H-2(b) haplotype-encoded MHC class I. Beta(2)m(-/-)/beta(2)m-K(d) ES-DC were significantly more efficient in eliciting immunity against RSV M2 protein-expressing tumor cells than beta(2)m(+/-)/beta(2)m-K(d) ES-DC. The modification of the beta(2)m or TAP gene may therefore be an effective strategy to resolve the problem of HLA class I allele mismatch between human ES or induced pluripotent stem cells and the recipients to be treated.

alpha-Galactosylceramide-loaded, antigen-expressing B cells prime a wide spectrum of antitumor immunity

Most of the current tumor vaccines successfully elicit strong protection against tumor but offer little therapeutic effect against existing tumors, highlighting the need for a more effective vaccine strategy. Vaccination with tumor antigen-presenting cells can induce antitumor immune responses. We have previously shown that NKT-licensed B cells prime cytotoxic T lymphocytes (CTLs) with epitope peptide and generate prophylactic/therapeutic antitumor effects. To extend our B cell vaccine approach to the whole antigen, and to overcome the MHC restriction, we used a nonreplicating adenovirus to transduce B cells with antigenic gene. Primary B cells transduced with an adenovirus-encoding truncated Her-2/neu (AdHM) efficiently expressed Her-2/neu. Compared with the moderate antitumor activity induced by vaccination with adenovirus-transduced B cells (B/AdHM), vaccination with alpha-galactosylceramide-loaded B/AdHM (B/AdHM/alpha GalCer) induced significantly stronger antitumor immunity, especially in the tumor-bearing mice. The depletion study showed that CD4(+), CD8(+) and NK cells were all necessary for the therapeutic immunity. Confirming the results of the depletion study, B/AdHM/alpha GalCer vaccination induced cytotoxic NK cell responses but B/AdHM did not. Vaccination with B/AdHM/alpha GalCer generated Her-2/neu-specific antibodies more efficiently than B/AdHM immunization. More importantly, B/AdHM/alpha GalCer could prime Her-2/neu-specific cytotoxic T cells more efficiently and durably than B/AdHM. CD4(+) cells appeared to be necessary for the induction of antibody and CTL responses. Our results demonstrate that, with the help of NKT cells, antigen-transduced B cells efficiently induce innate immunity as well as a wide range of adaptive immunity against the tumor, suggesting that they could be used to develop a novel cellular vaccine.

Genetically Manipulated Human Embryonic Stem Cell-Derived Dendritic Cells with Immune Regulatory Function

Genetically manipulated dendritic cells (DC) are considered to be a promising means for antigen-specific immune therapy. This study reports the generation, characterization, and genetic modification of DC derived from human embryonic stem (ES) cells. The human ES cell-derived DC (ES-DC) expressed surface molecules typically expressed by DC and had the capacities to stimulate allogeneic T lymphocytes and to process and present protein antigen in the context of histocompatibility leukocyte antigen (HLA) class II molecule. Genetic modification of human ES-DC can be accomplished without the use of viral vectors, by the introduction of expression vector plasmids into undifferentiated ES cells by electroporation and subsequent induction of differentiation of the transfectant ES cell clones to ES-DC. ES-DC introduced with invariant chain-based antigen-presenting vectors by this procedure stimulated HLA-DR-restricted antigen-specific T cells in the absence of exogenous antigen. Forced expression of programmed death-1-ligand-1 in ES-DC resulted in the reduction of the proliferative response of allogeneic T cells cocultured with the ES-DC. Generation and genetic modification of ES-DC from nonhuman primate (cynomolgus monkey) ES cells was also achieved by the currently established method. ES-DC technology is therefore considered to be a novel means for immune therapy.

CD1-restricted T cells and tumor immunity

CD1d-restricted T cells (NKT cells) are potent regulators of a broad range of immune responses. In particular, an abundance of research has focussed on the role of NKT cells in tumor immunity. This field of research has been greatly facilitated by the finding of agonist ligands capable of potently stimulating NKT cells and also animal models where NKT cells have been shown to play a natural role in the surveillance of tumors. Herein, we review the capability of NKT cells to promote the rejection of tumors and the mechanisms by which this occurs. We also highlight a growing field of research that has found that NKT cells are capable of suppressing anti-tumor immunity and discuss the progress to date for the immunotherapeutic use of NKT cells.

Embryonic stem cell-derived dendritic cells expressing glypican-3, a recently identified oncofetal antigen, induce protective immunity against highly metastatic mouse melanoma, B16-F10

We have recently established a method to generate dendritic cells from mouse embryonic stem cells. By introducing exogenous genes into embryonic stem cells and subsequently inducing differentiation to dendritic cells (ES-DC), we can now readily generate transfectant ES-DC expressing the transgenes. A previous study revealed that the transfer of genetically modified ES-DC expressing a model antigen, ovalbumin, protected the recipient mice from a challenge with an ovalbumin-expressing tumor. In the present study, we examined the capacity of ES-DC expressing mouse homologue of human glypican-3, a recently identified oncofetal antigen expressed in human melanoma and hepatocellular carcinoma, to elicit protective immunity against glypican-3-expressing mouse tumors. CTLs specific to multiple glypican-3 epitopes were primed by the in vivo transfer of glypican-3-transfectant ES-DC (ES-DC-GPC3). The transfer of ES-DC-GPC3 protected the recipient mice from subsequent challenge with B16-F10 melanoma, naturally expressing glypican-3, and with glypican-3-transfectant MCA205 sarcoma. The treatment with ES-DC-GPC3 was also highly effective against i.v. injected B16-F10. No harmful side effects, such as autoimmunity, were observed for these treatments. The depletion experiments and immunohistochemical analyses suggest that both CD8+ and CD4+ T cells contributed to the observed antitumor effect. In conclusion, the usefulness of glypican-3 as a target antigen for antimelanoma immunotherapy was thus shown in the mouse model using the ES-DC system. Human dendritic cells expressing glypican-3 would be a promising means for therapy of melanoma and hepatocellular carcinoma.