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

Recruiting Natural Killer T Cells to Improve Vaccination: Lessons from Preclinical and Clinical Studies

The capacity of type I natural killer T (NKT) cells to provide stimulatory signals to antigen-presenting cells has prompted preclinical research into the use of agonists as immune adjuvants, with much of this work focussed on stimulating T cell responses to cancer. In attempting to evaluate this approach in the clinic, our recent dendritic-cell based study failed to show an advantage to adding an agonist to the vaccine. Here we present potential limitations of the study, and suggest why other simpler strategies may be more effective. These include strategies to target antigen-presenting cells in the host, either through promoting efficient transfer from injected cell lines, facilitating uptake of antigen and agonist as injected conjugates, or encapsulating the components into injected nanovectors. While the vaccine landscape has changed with the rapid uptake of mRNA vaccines, we suggest that there is still a role for recruiting NKT cells in altering T cell differentiation programmes, notably the induction of resident memory T cells.

An optimized cocktail of small molecule inhibitors promotes the maturation of dendritic cells in GM-CSF mouse bone marrow culture

Dendritic cells (DCs) are the most potent antigen-presenting cells, playing an essential role in the pathogen and tumor recognition, and anti-tumor immunity, and linking both the innate and adaptive immunity. The monocyte-derived DCs generated by ex vivo culture, have been used for cancer immunotherapy to eliminate tumor; however, the clinical efficacies are not sufficient, and further improvement is essential. In this study, we established a method to generate DCs using small molecule compounds for cancer immunotherapy. We observed an increase in the percentage of CD11c+I-A/I-Ehigh cells, representing DCs, by adding four small molecular inhibitors: Y27632, PD0325901, PD173074, and PD98059 (abbreviated as YPPP), in mouse bone marrow (BM) culture with granulocyte-macrophage colony stimulating factor (GM-CSF). BM-derived DCs cultured with YPPP (YPPP-DCs) showed high responsiveness to lipopolysaccharide stimulation, resulting in increased interleukin (IL) -12 production and enhanced proliferation activity when co-cultured with naïve T cells compared with the vehicle control. RNA-seq analysis revealed an upregulation of peroxisome proliferator - activated receptor (PPAR) γ associated genes increased in YPPP-DCs. In tumor models treated with anti-programmed death (PD) -1 therapies, mice injected intratumorally with YPPP-DCs as a DCs vaccine exhibited reduced tumor growth and increased survival. These findings suggested that our method would be useful for the induction of DCs that efficiently activate effector T cells for cancer immunotherapy.

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.

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 cell vaccines: A review of recent developments and their potential pediatric application

For many cancers the use of conventional chemotherapy has been maximized, and further intensification of chemotherapy generally results in excess toxicity with little long-term benefit for cure. Many tumors become resistant to chemotherapy, making the investigation of novel approaches such as immunotherapy of interest. Because the tumor microenvironment is known to promote immune tolerance and down regulate the body's natural defense mechanisms, modulating the immune system with the use of dendritic cell (DC) therapy is an attractive approach. Thousands of patients with diverse tumor types have been treated with DC vaccines. While antigen specific immune responses have been reported, the duration and magnitude of these responses are typically weak, and objective clinical responses have been limited. DC vaccine generation and administration is a multi-step process with opportunities for improvement in source of DC for vaccine, selection of target antigen, and boosting effector cell response via administration of vaccine adjuvant or concomitant pharmacologic immunomodulation. In this review we will discuss recent developments in each of these areas and highlight elements that could be moved into pediatric clinical trials.

Cell division cycle-associated protein 1 as a new melanoma-associated antigen

Immune checkpoint inhibitors have increased the median survival of melanoma patients. To improve their effects, antigen-specific therapies utilizing melanoma-associated antigens should be developed. Cell division cycle-associated protein 1 (CDCA1), which has a specific function at the kinetochores for stabilizing microtubule attachment, is overexpressed in various cancers. CDCA1, which is a member of cancer-testis antigens, does not show detectable expression levels in normal tissues. Quantitative reverse transcription polymerase chain reaction and immunoblotting analyses revealed that CDCA1 was expressed in all of the tested melanoma cell lines, 74% of primary melanomas, 64% of metastatic melanomas and 25% of nevi. An immunohistochemical analysis and a Cox proportional hazards model showed that CDCA1 could be a prognostic marker in malignant melanoma (MM) patients. CDCA1-specific siRNA inhibited the cell proliferation of SKMEL2 and WM115 cells, but did not reduce the migration or invasion activity. These results suggest that CDCA1 may be a new therapeutic target of melanoma.

Investigation of FOXM1 as a Potential New Target for Melanoma

Recent studies have shown that immunotherapies and molecular targeted therapies are effective for advanced melanoma. Non-antigen-specific immunotherapies such as immunocheckpoint blockades have been shown to be effective in the treatment of advanced melanoma. However, the response rates remain low. To improve their efficacy, they should be combined with antigen-specific immunotherapy. Elevated expression of the transcription factor, Forkhead box M1 (FOXM1), has been reported in various human cancers, and it has been shown to have potential as a target for immunotherapy. The purpose of this study was to investigate the FOXM1 expression in human melanoma samples and cell lines, to evaluate the relationship between the FOXM1 expression and the clinical features of melanoma patients and to investigate the association between the FOXM1 and MAPK and PI3K/AKT pathways in melanoma cell lines. We conducted the quantitative reverse transcription PCR (qRT-PCR) and Western blotting analyses of melanoma cell lines, and investigated melanoma and nevus tissue samples by qRT-PCR and immunohistochemistry. We performed MEK siRNA and PI3K/AKT inhibitor studies and FOXM1 siRNA studies in melanoma cell lines. We found that FOXM1 was expressed in all of the melanoma cell lines, and was expressed in 49% of primary melanomas, 67% of metastatic melanomas and 10% of nevi by performing immunohistochemical staining. Metastatic melanoma samples exhibited significantly higher mRNA levels of FOXM1 (p = 0.004). Primary melanomas thicker than 2 mm were also more likely to express FOXM1. Patients whose primary melanoma expressed FOXM1 had a significantly poorer overall survival compared to patients without FOXM1 expression (p = 0.024). Downregulation of FOXM1 by siRNA significantly inhibited the proliferation of melanoma cells, and blockade of the MAPK and PI3K/AKT pathways decreased the FOXM1 expression in melanoma cell lines. In conclusion, FOXM1 is considered to be a new therapeutic target for melanoma.

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.

Generation of a large number of functional dendritic cells from human monocytes expanded by forced expression of cMYC plus BMI1

Anticancer vaccination therapies with monocyte-derived dendritic cells (DC) are widely conducted. A large number of primary monocytes (approximately 10(8) cells) are needed to generate the number of DC required to achieve an effect upon vaccination, and monocytes are usually purified from peripheral blood mononuclear cells obtained by apheresis procedure, which is somehow invasive for cancer patients. As a means to facilitate the generation of DC for therapeutic use, we herein report a method to amplify human monocytes. We found that lentivirus-mediated transduction of cMYC along with BMI1 induced proliferation of CD14(+) monocytes derived from 9 out of 12 blood donors, and we named the monocyte-derived proliferating cells CD14-ML. Their proliferation continued for 3-5 weeks in the presence of M-CSF and GM-CSF, resulting in 20-1000-fold amplification. Importantly, the expanded CD14-ML differentiated into fully functional DC (CD14-ML-DC) upon the addition of IL-4 to the culture. We successfully stimulated autologous CD8(+) T cells with CD14-ML-DC pulsed with cytomegalovirus peptide or MART-1 peptide to generate antigen-specific CTL lines. This is the first report describing the method for in vitro expansion of human peripheral blood monocytes.

NKT ligand-loaded, antigen-expressing B cells function as long-lasting antigen presenting cells in vivo

We had previously shown that activated NKT cells licensed B cells to be immunogenic antigen-presenting cells and helped to elicit a wide spectrum of cancer targeted immune responses. In the current study, we sought to verify the safety of αGalCer-loaded, and adenovirus-transduced B cell-based vaccines, together with mechanism of action. Intravenously injected αGalCer-loaded, antigen-expressing B cells rapidly localized in the spleen and directly primed CD8(+) T cells in an antigen-specific manner. The transferred antigen was sustained for at least 30 days. While some injected B cells produced nonspecific IgG, the antigen-specific IgG response was completely dependent on endogenous B cells. The liver was one of the main tissues where injected B cells were retained; however, we could not find the signs of liver toxicity. Our results demonstrate that αGalCer-loaded, antigen-expressing B cells behave as "antigen-presenting" cells that stimulate endogenous antigen-specific T cells and B cells in vivo without significant toxicity.

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.

Genetically modified dendritic cells in cancer immunotherapy: a better tomorrow?

IMPORTANCE OF THE FIELD

Dendritic cells (DC) are powerful antigen-presenting cells that induce and maintain primary cytotoxic T lymphocyte (CTL) responses directed against tumor antigens. Consequently, there has been much interest in their application as antitumor vaccines.

AREAS COVERED IN THIS REVIEW

A large number of DC-based vaccine trials targeting a variety of cancers have been conducted; however, the rate of reported clinically significant responses remains low. Modification of DC to express tumor antigens or immunostimulatory molecules through the transfer of genes or mRNA transfection offers a logical alternative with potential advantages over peptide- or protein antigen-loaded DC. In this article, we review the current results and future prospects for genetically modified DC vaccines for the treatment of cancer.

WHAT THE READER WILL GAIN

Genetically-modified dendritic cell-based vaccines represent a powerful tool for cancer therapy. Numerous preclinical and clinical studies have demonstrated the potential of dendritic cell vaccines alone or in combination with other therapeutic modalities.

TAKE HOME MESSAGE

Genetically modified DC-based anti-cancer vaccination holds promise, perhaps being best employed in the adjuvant setting with minimal residual disease after primary therapy, or in combination with other antitumor or immune-enhancing therapies.

[Cancer immunotherapy by utilizing dedritic cells derived from pluripotent stem cells]

It was recently revealed that ES-cell like pluripotent stem cells, designated as iPS cells, can be generated from somatic cells. iPS cells could be used as not only a source of regeneration medicine, but also a source of cell vaccine. Pluripotent stem cells are characterized by pluripotency and infinite propagation capacity. Non-virus-mediated methods for gene transfer have been established. Genetic modification of pluripotent stem cells and subsequent in vitro differentiation to dendritic cells would be an attractive strategy. Here we describe the previous studies about cancer immunotherapy by utilizing dendritic cells derived from pluripotent stem cells.

Identification of HLA-A2-restricted CTL epitopes of a novel tumour-associated antigen, KIF20A, overexpressed in pancreatic cancer

Background:

Identification of tumour-associated antigens (TAAs) that induce cytotoxic T lymphocytes (CTLs) specific to cancer cells is critical for the development of anticancer immunotherapy. In this study, we aimed at identifying a novel TAA of pancreatic cancer for immunotherapy.

Methods:

On the basis of the genome-wide cDNA microarray analysis, we focused on KIF20A (also known as RAB6KIFL/MKlp2) as a candidate TAA in pancreatic cancer cells. The HLA-A2 (A*02:01)-restricted CTL epitopes of KIF20A were identified using HLA-A2 transgenic mice (Tgm) and the peptides were examined to check whether they could generate human CTLs exhibiting cytotoxic responses against KIF20A⁺, HLA-A2⁺ tumour cells in vitro.

Results:

KIF20A was overexpressed in pancreatic cancer and in some other malignancies, but not in their non-cancerous counterparts and many normal adult tissues. We found that KIF20A-2 (p12–20, LLSDDDVVV), KIF20A-8 (p809–817, CIAEQYHTV), and KIF20A-28 (p284–293, AQPDTAPLPV) peptides could induce HLA-A2-restricted CTLs in HLA-A2 Tgm without causing autoimmunity. Peptide-reactive human CTLs were generated from peripheral blood mononuclear cells of HLA-A2⁺ healthy donors by in vitro stimulation with the three peptides, and those CTLs successfully exhibited cytotoxic responses to cancer cells expressing both KIF20A and HLA-A2.

Conclusion:

KIF20A is a novel promising candidate for anticancer immunotherapeutic target for pancreatic cancers.

Emerging applications of lentiviral vectors in dendritic cell-based immunotherapy

Dendritic cells are professional antigen-presenting cells that initiate, regulate and shape the induction of specific immune responses. The ability to use dendritic cells in the induction of antigen-specific tolerance, antigen-specific immunity or specific differentiation of T-helper subsets holds great promise in dendritic cell-based immunotherapy of various diseases such as cancer, viral infections, allergy, as well as autoimmunity. Replication-incompetent HIV-1-based lentiviral vector is now emerging as a promising delivery system to genetically modify dendritic cells through antigen recognition, costimulatory molecules and/or polarization signals for the manipulation of antigen-specific immunity in vivo. This article discusses some of the recent advances in the uses of lentiviral vectors in dendritic cell-based immunotherapy.

The evolving role of dendritic cells in cancer therapy

IMPORTANCE OF THE FIELD

Dendritic cells (DC) are a clear choice for use in cancer immunotherapy, and much research has focused on generating DC for clinical use. Although DC therapy has been successful in inducing specific anti-tumour immune responses, these have rarely translated into clinical efficacy.

AREAS COVERED IN THIS REVIEW

We examine some of the components of generating DC for therapy, including their culture, antigen loading and delivery, and discuss why DC therapy has not yet delivered substantial clinical benefit. We also examine more novel approaches, such as the potential for combination DC-based immunomodulatory strategies.

WHAT THE READER WILL GAIN

Given the highly immunosuppressive tumour environment, many of the approaches to DC vaccination are unlikely to result in effective therapy, as even successfully primed T cells may fail to infiltrate tumours or be anergized after entry. Broader approaches against multiple tumour-associated antigens in the context of overcoming tumour immune suppression are likely to prove more successful. The combination of oncolytic viral therapy with DC vaccines may promote an inflammatory tumour environment, inducing optimal DC activation, T cell priming and effective therapy.

TAKE HOME MESSAGE

Evolving DC-based therapeutic strategies addressing multiple components of tumour-immune system interactions may yield substantial benefits for patients.

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.