In vivo programming of tumor antigen-specific T lymphocytes from pluripotent stem cells to promote cancer immunosurveillance

Pro-inflammatory responses after peptide-based cancer immunotherapy

Therapeutic vaccinations are designed to prevent cancer by inducing immune responses against tumor antigens. in cancer cells, tumor-associated antigens (TAA) or tumor-specific (mutated) derived peptides are presented within the clefts of main histocompatibility complex (MHC) class I or class II molecules, they either activate cytotoxic T-lymphocytes (CTLs), CD4+ T or CD8+ T lymphocytes, which release cytokines that can suppress tumor cells growth. In cancer immunotherapies, CD8+ T lymphocytes are a major mediator of tumor repression. The effect of peptide-based vaccinations on cytokines in the activating CD8+ T cell against targeted tumor antigens is the subject of this review. It is believed that peptide-based vaccines increased IFN-γ, TNF-α, IL-2, and IL-12, secreting CTL line by interacting with dendritic cell (DC), supposed to stimulate immune system. Additionally, mechanisms of CTL activation and dysfunction were also studied. According to most of the data resulted from in vivo and in vitro research works, it is assumed that peptide-based vaccines increased IFN-γ, TNF-α, IL-2, and IL-12.

Tumorous expression of NAC1 restrains antitumor immunity through the LDHA-mediated immune evasion

BACKGROUND

T cell-mediated antitumor immunity has a vital role in cancer prevention and treatment; however, the immune-suppressive tumor microenvironment (TME) constitutes a significant contributor to immune evasion that weakens antitumor immunity. Here, we explore the relationship between nucleus accumbens-associated protein-1 (NAC1), a nuclear factor of the BTB (broad-complex, Tramtrack, bric a brac)/POZ (Poxvirus, and Zinc finger) gene family, and the TME.

METHODS

Adoptive cell transfer (ACT) of mouse or human tumor antigen (Ag)-specific CD8+ cytotoxic T lymphocytes (CTLs) was tested in an immunocompetent or immunodeficient mouse model of melanoma with or without expression of NAC1. The effects of NAC1 expression on immune evasion in tumor cells were assessed in vitro and in vivo. CRISPR/Cas9, glycolysis analysis, retroviral transduction, quantitative real-time PCR, flow cytometric analysis, immunoblotting, database analyses were used to screen the downstream target and underlying mechanism of NAC1 in tumor cells.

RESULTS

Tumorous expression of NAC1 negatively impacts the CTL-mediated antitumor immunity via lactate dehydrogenase A (LDHA)-mediated suppressive TME. NAC1 positively regulated the expression of LDHA at the transcriptional level, which led to higher accumulation of lactic acid in the TME. This inhibited the cytokine production and induced exhaustion and apoptosis of CTLs, impairing their cell-killing ability. In the immunocompetent and immunodeficient mice, NAC1 depleted melanoma tumors grew significantly slower and had an elevated infiltration of tumor Ag-specific CTLs following ACT, compared with the control groups.

CONCLUSIONS

Tumor expression of NAC1 contributes substantially to immune evasion through its regulatory role in LDHA expression and lactic acid production. Thus, therapeutic targeting of NAC1 warrants further exploration as a potential strategy to reinforce cancer immunotherapy, such as the ACT of CTLs.

NAC1 modulates autoimmunity by suppressing regulatory T cell-mediated tolerance

We report here that nucleus accumbens-associated protein-1 (NAC1), a nuclear factor of the Broad-complex, Tramtrack, Bric-a-brac/poxvirus and zinc finger (BTB/POZ) gene family, is a negative regulator of FoxP3 in regulatory T cells (Tregs) and a critical determinant of immune tolerance. Phenotypically, NAC1-/- mice showed substantial tolerance to the induction of autoimmunity and generated a larger amount of CD4+ Tregs that exhibit a higher metabolic profile and immune-suppressive activity, increased acetylation and expression of FoxP3, and slower turnover of this transcription factor. Treatment of Tregs with the proinflammatory cytokines interleukin-1β or tumor necrosis factor-α induced a robust up-regulation of NAC1 but evident down-regulation of FoxP3 as well as the acetylated FoxP3. These findings imply that NAC1 acts as a trigger of the immune response through destabilization of Tregs and suppression of tolerance induction, and targeting of NAC1 warrants further exploration as a potential tolerogenic strategy for treatment of autoimmune disorders.

Stem Cell-Derived Viral Antigen-Specific T Cells Suppress HIV Replication and PD-1 Expression on CD4+ T Cells

The viral antigen (Ag)-specific CD8+ cytotoxic T lymphocytes (CTLs) derived from pluripotent stem cells (PSCs), i.e., PSC-CTLs, have the ability to suppress the human immunodeficiency virus (HIV) infection. After adoptive transfer, PSC-CTLs can infiltrate into the local tissues to suppress HIV replication. Nevertheless, the mechanisms by which the viral Ag-specific PSC-CTLs elicit the antiviral response remain to be fully elucidated. In this study, we generated the functional HIV-1 Gag epitope SL9-specific CTLs from the induced PSC (iPSCs), i.e., iPSC-CTLs, and investigated the suppression of SL9-specific iPSC-CTLs on viral replication and the protection of CD4+ T cells. A chimeric HIV-1, i.e., EcoHIV, was used to produce HIV replication in mice. We show that adoptive transfer of SL9-specific iPSC-CTLs greatly suppressed EcoHIV replication in the peritoneal macrophages and spleen in the animal model. Furthermore, we demonstrate that the adoptive transfer significantly reduced expression of PD-1 on CD4+ T cells in the spleen and generated persistent anti-HIV memory T cells. These results indicate that stem cell-derived viral Ag-specific CTLs can robustly accumulate in the local tissues to suppress HIV replication and prevent CD4+ T cell exhaustion through reduction of PD-1 expression.

An optimized protocol for the generation of HBV viral antigen-specific T lymphocytes from pluripotent stem cells

In T cell-based cancer immunotherapy, tumor antigen (Ag)-specific CD8+ cytotoxic T lymphocytes (CTLs) can specifically target tumor Ags on malignant cells. This promising approach drove us to adopt this strategy of T cell transfer (ACT)-based immunotherapy for chronic viral infections. Here, we describe the generation of hepatitis B virus (HBV) Ag-specific CTLs from induced pluripotent stem cells (iPSCs), i.e., iPSC-CTLs. Ag-specific iPSC-CTLs can target HBV Ag+ cells and infiltrate into the liver to suppress HBV replication in a murine model. For complete details on the use and execution of this protocol, please refer to Haque et al. (2020).

Development of CAR-T Cell Persistence in Adoptive Immunotherapy of Solid Tumors

Chimeric antigen receptor (CAR) T (CAR-T) cell transfer has made great success in hematological malignancies, but only shown a limited effect on solid tumors. One of the major hurdles is the poor persistence of infused cells derived from ex vivo activation/expansion and repeated antigen encounter after re-infusion. Bcl-xL has been demonstrated to play an important role on normal T cell survival and function as well as genetically engineered cells. In the current study, we developed a retroviral CAR construct containing a second-generation carcinoembryonic antigen (CEA)-targeting CAR with the Bcl-xL gene and tested the anti-CEA CAR-T cell immunotherapy for colorectal cancer. In vitro, the anti-CEA CAR-T cells destroyed CEA-expressing tumor cells and sustained survival. In vivo, adoptive cell transfer of anti-CEA CAR-T cells significantly enhanced the ability of the CAR-T cells to accumulate in tumor tissues, suppress tumor growth and increase the overall survival rate of tumor-bearing mice in a murine model of colorectal cancer. These results demonstrate a novel CAR-T platform that has the ability to increase the persistence of CAR-T cells in solid tumors through exogenous expression of persistent genes. The data provide a potentially novel approach to augment CAR-T immunotherapy for solid tumors.

Disease modeling and stem cell immunoengineering in regenerative medicine using CRISPR/Cas9 systems

CRISPR/Cas systems are popular genome editing tools that belong to a class of programmable nucleases and have enabled tremendous progress in the field of regenerative medicine. We here outline the structural and molecular frameworks of the well-characterized type II CRISPR system and several computational tools intended to facilitate experimental designs. The use of CRISPR tools to generate disease models has advanced research into the molecular aspects of disease conditions, including unraveling the molecular basis of immune rejection. Advances in regenerative medicine have been hindered by major histocompatibility complex-human leukocyte antigen (HLA) genes, which pose a major barrier to cell- or tissue-based transplantation. Based on progress in CRISPR, including in recent clinical trials, we hypothesize that the generation of universal donor immune-engineered stem cells is now a realistic approach to tackling a multitude of disease conditions.

Notch Pathway: A Journey from Notching Phenotypes to Cancer Immunotherapy

Notch is a key evolutionary conserved pathway, which has fascinated and engaged the work of investigators in an uncountable number of biological fields, from development of metazoans to immunotherapy for cancer. The study of Notch has greatly contributed to the understanding of cancer biology and a substantial effort has been spent in designing Notch-targeting therapies. Due to its broad involvement in cancer, targeting Notch would allow to virtually modulate any aspect of the disease. However, this means that Notch-based therapies must be highly specific to avoid off-target effects. This review will present the newest mechanistic and therapeutic advances in the Notch field and discuss the promises and challenges of this constantly evolving field.

Stem Cell-Derived Viral Antigen-Specific T Cells Suppress HBV Replication through Production of IFN-γ and TNF-⍺

The viral antigen (Ag)-specific CD8⁺ cytotoxic T lymphocytes (CTLs) derived from pluripotent stem cells (PSCs), i.e., PSC-CTLs, have the ability to suppress hepatitis B virus (HBV) infection. After adoptive transfer, PSC-CTLs can infiltrate into the liver to suppress HBV replication. Nevertheless, the mechanisms by which the viral Ag-specific PSC-CTLs provoke the antiviral response remain to be fully elucidated. In this study, we generated the functional HBV surface Ag-specific CTLs from the induced PSC (iPSCs), i.e., iPSC-CTLs, and investigated the underlying mechanisms of the CTL-mediated antiviral replication in a murine model. We show that adoptive transfer of HBV surface Ag-specific iPSC-CTLs greatly suppressed HBV replication and prevented HBV surface Ag expression. We further demonstrate that the adoptive transfer significantly increased T cell accumulation and production of antiviral cytokines. These results indicate that stem cell-derived viral Ag-specific CTLs can robustly accumulate in the liver and suppress HBV replication through producing antiviral cytokines.

Induced Pluripotent Stem Cells: Reprogramming Platforms and Applications in Cell Replacement Therapy

The generation of induced pluripotent stem cells (iPSCs) from differentiated mature cells is one of the most promising technologies in the field of regenerative medicine. The ability to generate patient-specific iPSCs offers an invaluable reservoir of pluripotent cells, which could be genetically engineered and differentiated into target cells to treat various genetic and degenerative diseases once transplanted, hence counteracting the risk of graft versus host disease. In this context, we review the scientific research streams that lead to the emergence of iPSCs, the roles of reprogramming factors in reprogramming to pluripotency, and the reprogramming strategies. As iPSCs serve tremendous correction potentials for various diseases, we highlight the successes and challenges of iPSCs in cell replacement therapy and the synergy of iPSCs and clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 gene editing tools in therapeutics research.

Targeting cancers through TCR-peptide/MHC interactions

Adoptive T cell therapy has achieved dramatic success in a clinic, and the Food and Drug Administration approved two chimeric antigen receptor-engineered T cell (CAR-T) therapies that target hematological cancers in 2018. A significant issue faced by CAR-T therapies is the lack of tumor-specific biomarkers on the surfaces of solid tumor cells, which hampers the application of CAR-T therapies to solid tumors. Intracellular tumor-related antigens can be presented as peptides in the major histocompatibility complex (MHC) on the cell surface, which interact with the T cell receptors (TCR) on antigen-specific T cells to stimulate an anti-tumor response. Multiple immunotherapy strategies have been developed to eradicate tumor cells through targeting the TCR-peptide/MHC interactions. Here, we summarize the current status of TCR-based immunotherapy strategies, with particular focus on the TCR structure, activated signaling pathways, the effects and toxicity associated with TCR-based therapies in clinical trials, preclinical studies examining immune-mobilizing monoclonal TCRs against cancer (ImmTACs), and TCR-fusion molecules. We propose several TCR-based therapeutic strategies to achieve optimal clinical responses without the induction of autoimmune diseases.

Stem Cell-Derived Viral Ag-Specific T Lymphocytes Suppress HBV Replication in Mice

Hepatitis B virus (HBV) infection is a global health issue. With over 350 million people affected worldwide, HBV infection remains the leading cause of liver cancer. This is a major concern, especially in developing countries. Failure of the immune system to mount an effective response against HBV leads to chronic infection. Although HBV vaccine is present and novel antiviral medicines are being created, eradication of virus-reservoir cells remains a major health topic. Described here is a method for the generation of viral antigen (Ag) -specific CD8⁺ cytotoxic T lymphocytes (CTLs) derived from induced pluripotent stem cells (iPSCs) (i.e., iPSC-CTLs), which have the ability to suppress HBV replication. HBV replication is efficiently induced in mice through hydrodynamic injection of an HBV expression plasmid, pAAV/HBV1.2, into the liver. Then, HBV surface Ag-specific mouse iPSC-CTLs are adoptively transferred, which greatly suppresses HBV replication in the liver and blood as well as prevents HBV surface Ag expression in hepatocytes. This method demonstrates HBV replication in mice after hydrodynamic injection and that stem cell-derived viral Ag-specific CTLs can suppress HBV replication. This protocol provides a useful method for HBV immunotherapy.

Targeting Stem Cell-Derived Tissue-Associated Regulatory T Cells for Type 1 Diabetes Immunotherapy

PURPOSE OF REVIEW

Type 1 diabetes (T1D) is an autoimmune disease in which the immune cells selectively destroy the pancreatic beta (β) cells and results in the deficiency of insulin production. The optimal treatment strategy for T1D should be preventing of β-cell destruction in the pancreas. The purpose of this review is to discuss the immunological therapeutic mechanisms that will help to understand the development and control of β-cell destruction. The review also presents a novel method for development of autoantigen (Ag)-specific regulatory T cells (Tregs) for T1D immunotherapy.

RECENT FINDINGS

Pancreatic-resident Tregs have the ability to dramatically suppress hyperactive immune cells. Islet cell transplantation is another attractive approach to replace the failed β cells. Due to the limited source of islet cells, research is going on in the use of animal cells and adult stem cells that may be derived from the patient's own body to produce β cells for transplantation. The mechanism behind the pancreatic β-cell destruction is largely unknown. In this review, a novel approach for the generation of tissue-associated Tregs from stem cells is considered. The stem cell-derived tissue-associated Tregs have the ability to home to the damaged pancreas to prevent the destruction. The review also provides new insights on the mechanism on how these suppressive immune cells protect the pancreas from the destruction of autoimmune cells. A novel method to develop functional auto Ag-specific Tregs that are derived from induced pluripotent stem cells (iPSCs), i.e., iPSC-Tregs, is discussed. Adoptive transfer of the iPSC-Tregs can substantially suppress T1D development in a murine model.

In vivo construction of lymphoid node by implantation of adipose-derived stromal cells with hydroxypropyl methyl cellulose hydrogel in BALB/c nude mice

Adipose-derived stromal cells have multilineage potential to differentiate into several specialized tissue types. Herein, we investigated whether ADSCs could differentiate into lymphoid node in vivo. Human ADSCs from routine liposuction were cultured in differentiation medium and were supplemented with transforming growth factor β1 (TGF)-β1 and basic fibroblast growth factor (bFGF). The induced hADSCs mixed with 13% (w/v) hydroxypropyl methylcellulose (HPMC) were injected into BALB/c nude mice subcutaneously. Eight weeks later, nodules were found under the injected sites. Histology, immunohistochemistry, and species identification analysis confirmed that the nodules were lymphoid nodes that were derived from the injected hADSCs. Our experiment demonstrated that the hADSCs could differentiate into lymphocyte-like cells and form lymphoid nodes in vivo. TGF-β1 and bFGF might play important roles in the differentiation of hADSCs into lymphocyte-like cells. Our study might present an alternative approach for engineering immune organs and thus offer potential treatment for immunodeficiency diseases.

A Three-dimensional Thymic Culture System to Generate Murine Induced Pluripotent Stem Cell-derived Tumor Antigen-specific Thymic Emigrants

The inheritance of pre-rearranged T cell receptors (TCRs) and their epigenetic rejuvenation make induced pluripotent stem cell (iPSC)-derived T cells a promising source for adoptive T cell therapy (ACT). However, classical in vitro methods for producing regenerated T cells from iPSC result in either innate-like or terminally differentiated T cells, which are phenotypically and functionally distinct from naïve T cells. Recently, a novel three-dimensional (3D) thymic culture system was developed to generate a homogenous subset of CD8αβ⁺ antigen-specific T cells with a naïve T cell-like functional phenotype, including the capacity for proliferation, memory formation, and tumor suppression in vivo. This protocol avoids aberrant developmental fates, allowing for the generation of clinically relevant iPSC-derived T cells, designated as iPSC-derived thymic emigrants (iTE), while also providing a potent tool to elucidate the subsequent functions necessary for T cell maturation after thymic selection.

Generation of Tumor Antigen-Specific Cytotoxic T Lymphocytes from Pluripotent Stem Cells

Immunotherapy is a developing but very promising arsenal to treat cancer. Acquiring a more potent and effective approach in cancer immunotherapy is always the ultimate pursuance. CTL-based therapies are highly acclaimed recently due to its direct killing property. However, difficulty in obtaining adequate number of CTLs is still a major obstacle. In previous studies, it is shown that pluripotent stem cell-derived cytotoxic T lymphocytes (CTL)-especially the genetically engineered tumor antigen-specific CTLs-may serve as a good candidate for this goal. Here we introduce a novel approach in generating tumor antigen-specific CTLs from induced pluripotent stem cells (iPSCs) by using both in vitro and in vivo priming mechanisms for the tumor management in a murine melanoma model.

Stem cell-derived tissue-associated regulatory T cells suppress the activity of pathogenic cells in autoimmune diabetes

The autoantigen-specific Tregs from pluripotent stem cells (PSCs), i.e., PSC-Tregs, have the ability to suppress autoimmunity. PSC-Tregs can be programmed to be tissue associated and to infiltrate into local inflamed tissues to suppress autoimmune responses after adoptive transfer. Nevertheless, the mechanisms by which the autoantigen-specific PSC-Tregs suppress the autoimmune response remain to be fully elucidated. In this study, we generated functional autoantigen-specific Tregs from the induced PSC (iPSCs), i.e., iPSC-Tregs, and investigated the underlying mechanisms of autoimmunity suppression by these Tregs in a type 1 diabetes (T1D) murine model. A double-Tg mouse model of T1D was established in F1 mice, in which the first generation of RIP-mOVA Tg mice that were crossed with OT-I T cell receptor (TCR) Tg mice was challenged with vaccinia viruses expressing OVA (VACV-OVA). We show that adoptive transfer of OVA-specific iPSC-Tregs greatly suppressed autoimmunity in the animal model and prevented the insulin-secreting pancreatic β cells from destruction. Further, we demonstrate that the adoptive transfer significantly reduced the expression of ICAM-1 in the diabetic pancreas and inhibited the migration of pathogenic CD8+ T cells and the production of the proinflammatory IFN-γ in the pancreas. These results indicate that the stem cell-derived tissue-associated Tregs can robustly accumulate in the diabetic pancreas, and, through downregulating the expression of ICAM-1 in the local inflamed tissues and inhibiting the production of proinflammatory cytokine IFN-γ, suppress the migration and activity of the pathogenic immune cells that cause T1D.

Adoptive Cell Transfer: Is it a Promising Immunotherapy for Colorectal Cancer?

The last decade has witnessed significant advances in the adoptive cell transfer (ACT) technique, which has been appreciated as one of the most promising treatments for patients with cancer. Utilization of ACT can enhance the function of the immune system or improve the specificity and persistence of transferred cells. Various immune cells including T lymphocytes, natural killer cells, dendritic cells, and even stem cells can be used in the ACT despite their different functional mechanisms. Colorectal cancer (CRC) is among the most common malignancies and causes millions of deaths worldwide every year. In this review, we discuss the status and perspective of the ACT in the treatment of CRC.

NOTCH Signaling in T-Cell-Mediated Anti-Tumor Immunity and T-Cell-Based Immunotherapies

The NOTCH (1–4) family of receptors are highly conserved and are critical in regulating many developmental processes and in the maintenance of tissue homeostasis. Our laboratory and numerous others have demonstrated that aberrant NOTCH signaling is oncogenic in several different cancer types. Conversely, there is also evidence that NOTCH can also function as a tumor suppressor. In addition to playing an essential role in tumor development, NOTCH receptors regulate T-cell development, maintenance, and activation. Recent studies have determined that NOTCH signaling is required for optimal T-cell-mediated anti-tumor immunity. Consequently, tumor cells and the tumor microenvironment have acquired mechanisms to suppress NOTCH signaling to evade T-cell-mediated killing. Tumor-mediated suppression of NOTCH signaling in T-cells can be overcome by systemic administration of NOTCH agonistic antibodies and ligands or proteasome inhibitors, resulting in sustained NOTCH signaling and T-cell activation. In addition, NOTCH receptors and ligands are being utilized to improve the generation and specificity of T-cells for adoptive transplant immunotherapies. In this review, we will summarize the role(s) of NOTCH signaling in T-cell anti-tumor immunity as well as TCR- and chimeric antigen receptor-based immunotherapies.

Protective Cancer Vaccine Using Genetically Modified Hematopoietic Stem Cells

Hematopoietic stem cells (HSCs) yield both the myeloid and lymphoid lineages of blood cells and can be reprogrammed into tumor antigen (Ag)-specific CD8⁺ cytotoxic T lymphocytes (CTLs) to prevent tumor growth. However, the optimal approach for differentiating tumor Ag-specific CTLs from HSCs, such as HSC-CTLs, remains elusive. In the current study, we showed that a combination of genetic modification of HSCs and in vivo T cell development facilitates the generation of Ag-specific CTLs that suppressed tumor growth. Murine HSCs, which were genetically modified with chicken ovalbumin (OVA)-specific T cell receptor, were adoptively transferred into recipient mice. In the following week, mice were administered with intraperitoneal injections of an agonist α-Notch 2 antibody and cytokines (rFlt3L and rIL-7) three times. After another two weeks, mice received a subcutaneous inoculation of B16-OVA melanoma cells that express OVA as a surrogate tumor Ag, before the anti-tumor activity of HSC-derived T cells was assessed. OVA-specific CTLs developed in vivo and greatly responded to OVA Ag stimulation ex vivo. In addition, mice receiving genetically modified HSCs and in vivo priming established anti-tumor immunity, resulting in the suppression of tumor growth. These results reported in this present study provide an alternative strategy to develop protective cancer vaccines by using genetically modified HSCs.

Generation of Tumor Antigen-Specific iPSC-Derived Thymic Emigrants Using a 3D Thymic Culture System

Induced pluripotent stem cell (iPSC)-derived T cells may provide future therapies for cancer patients, but those generated by current methods, such as the OP9/DLL1 system, have shown abnormalities that pose major barriers for clinical translation. Our data indicate that these iPSC-derived CD8 single-positive T cells are more like CD4+CD8+ double-positive T cells than mature naive T cells because they display phenotypic markers of developmental arrest and an innate-like phenotype after stimulation. We developed a 3D thymic culture system to avoid these aberrant developmental fates, generating a homogeneous subset of CD8αβ+ antigen-specific T cells, designated iPSC-derived thymic emigrants (iTEs). iTEs exhibit phenotypic and functional similarities to naive T cells both in vitro and in vivo, including the capacity for expansion, memory formation, and tumor suppression. These data illustrate the limitations of current methods and provide a tool to develop the next generation of iPSC-based antigen-specific immunotherapies.

Development and characterization of naive single-type tumor antigen-specific CD8+ T lymphocytes from murine pluripotent stem cells

Optimal approaches to differentiate tumor antigen-specific cytotoxic T lymphocytes (CTLs) from pluripotent stem cells (PSCs) remain elusive. In the current study, we showed that combination of in vitro priming through Notch ligands and in vivo development facilitated the generation of tumor Ag-specific CTLs that effectively inhibited tumor growth. We co-cultured the murine induced PSCs (iPSCs) genetically modified with tyrosinase-related protein 2 (TRP2)-specific T cell receptors with OP9 cell line expressing both Notch ligands Delta-like 1 and 4 (OP9-DL1/DL4) for a week before adoptively transferred into recipient C67BL/6 mice. Three weeks later, B16 melanoma cells were inoculated subcutaneously, and the antitumor activity of the iPSC-derived T cells was assessed. We observed the development of the TRP2-specific iPSC-CD8⁺ T cells that responded to Ag stimulation and infiltrated into melanoma tissues, significantly inhibited the tumor growth, and improved the survival of the tumor-bearing mice. Thus, this approach may provide a novel effective strategy to treatment of malignant tumors.

MiR-21 is required for anti-tumor immune response in mice: an implication for its bi-directional roles

Here we show that miR-21, a microRNA known for its oncogenic activity, is also essential for mediating immune responses against tumor. Knockout of miR-21 in mice slowed the proliferation of both CD4⁺ and CD8⁺ cells, reduced their cytokine production and accelerated the grafted tumor growth. Further investigations indicated that miR-21 could activate CD4⁺ and CD8⁺ T cells via the PTEN/Akt pathway in response to stimulations. Taken together, these data suggest the key functions of miR-21 in mediating anti-tumor immune response and thereby uncover a bi-directional role of this traditionally known 'oncomiR' in tumorigenesis. Our study may provide new insights for the design of cancer therapies targeting microRNAs, with an emphasis on the dynamic and possibly unexpected role of these molecules.

c-Myc-Induced Survivin Is Essential for Promoting the Notch-Dependent T Cell Differentiation from Hematopoietic Stem Cells

Notch is indispensable for T cell lineage commitment, and is needed for thymocyte differentiation at early phases. During early stages of T cell development, active Notch prevents other lineage potentials including B cell lineage and myeloid cell (e.g., dendritic cell) lineage. Nevertheless, the precise intracellular signaling pathways by which Notch promotes T cell differentiation remain unclear. Here we report that the transcription factor c-Myc is a key mediator of the Notch signaling–regulated T cell differentiation. In a well-established in vitro differentiation model of T lymphocytes from hematopoietic stem cells, we showed that Notch1 and 4 directly promoted c-Myc expression; dominant-negative (DN) c-Myc inhibited early T cell differentiation. Moreover, the c-Myc expression activated by Notch signaling increased the expression of survivin, an inhibitor of apoptosis (IAP) protein. We further demonstrated that over-expression of c-Myc increased the abundance of survivin and the T cell differentiation thereof, whereas dn c-Myc reduced survivin levels and concomitantly retarded the differentiation. The c-Myc–dependent survivin induction is functionally germane, because Notch-dependent T cell differentiation was canceled by the depletion of survivin. These results identify both c-Myc and survivin as important mediators of the Notch signaling–regulated differentiation of T lymphocytes from hematopoietic stem cells.

Stem Cell-Derived Regulatory T Cells for Therapeutic Use in Arthritis

Pluripotent stem cells (PSCs) can be utilized to obtain a renewable source of healthy regulatory T cells (T_regs) to treat autoimmune arthritis as they have the ability to produce almost all cell types in the body, including T_regs. However, the right conditions for the development of antigen (Ag)-specific T_regs from PSCs (i.e., PSC-T_regs) remain unknown. An ongoing project will determine the mechanisms underlying the Ag-specific PSC-T_reg treatments that aim to modulate tolerance in autoimmune arthritis. The knowledge gained from these studies will provide new insights into cell-based therapies in autoimmune arthritis, and advance the understanding of fundamental mechanisms underlying T_reg differentiation.

Development of Stem Cell-derived Antigen-specific Regulatory T Cells Against Autoimmunity

Autoimmune diseases arise due to the loss of immunological self-tolerance. Regulatory T cells (Tregs) are important mediators of immunologic self-tolerance. Tregs represent about 5 - 10% of the mature CD4⁺ T cell subpopulation in mice and humans, with about 1 - 2% of those Tregs circulating in the peripheral blood. Induced pluripotent stem cells (iPSCs) can be differentiated into functional Tregs, which have a potential to be used for cell-based therapies of autoimmune diseases. Here, we present a method to develop antigen (Ag)-specific Tregs from iPSCs (i.e., iPSC-Tregs). The method is based on incorporating the transcription factor FoxP3 and an Ag-specific T cell receptor (TCR) into iPSCs and then differentiating on OP9 stromal cells expressing Notch ligands delta-like (DL) 1 and DL4. Following in vitro differentiation, the iPSC-Tregs express CD4, CD8, CD3, CD25, FoxP3, and Ag-specific TCR and are able to respond to Ag stimulation. This method has been successfully applied to cell-based therapy of autoimmune arthritis in a murine model. Adoptive transfer of these Ag-specific iPSC-Tregs into Ag-induced arthritis (AIA)-bearing mice has the ability to reduce joint inflammation and swelling and to prevent bone loss.

Development of Auto Antigen-specific Regulatory T Cells for Diabetes Immunotherapy

CD4⁺ regulatory T cells (Tregs) are essential for normal immune surveillance, and their dysfunction can lead to the development of autoimmune diseases, such as type-1 diabetes (T1D). T1D is a T cell-mediated autoimmune disease characterized by islet β cell destruction, hypoinsulinemia, and severely altered glucose homeostasis. Tregs play a critical role in the development of T1D and participate in peripheral tolerance. Pluripotent stem cells (PSCs) can be utilized to obtain a renewable source of healthy Tregs to treat T1D as they have the ability to produce almost all cell types in the body, including Tregs. However, the right conditions for the development of antigen (Ag)-specific Tregs from PSCs (i.e., PSC-Tregs) remain undefined, especially molecular mechanisms that direct differentiation of such Tregs. Auto Ag-specific PSC-Tregs can be programmed to be tissue-associated and infiltrate to local inflamed tissue (e.g., islets) to suppress autoimmune responses after adoptive transfer, thereby avoiding potential overall immunosuppression from non-specific Tregs. Developing auto Ag-specific PSC-Tregs can reduce overall immunosuppression after adoptive transfer by accumulating inflamed islets, which drives forward the use of therapeutic PSC-Tregs for cell-based therapies in T1D.

C-Myc regulation by costimulatory signals modulates the generation of CD8+ memory T cells during viral infection

The signalling mechanisms of costimulation in the development of memory T cells remain to be clarified. Here, we show that the transcription factor c-Myc in CD8⁺ T cells is controlled by costimulatory molecules, which modulates the development of memory CD8⁺ T cells. C-Myc expression was dramatically reduced in Cd28^−/− or Ox40^−/− memory CD8⁺ T cells, and c-Myc over-expression substantially reversed the defects in the development of T-cell memory following viral infection. C-Myc regulated the expression of survivin, an inhibitor of apoptosis, which promoted the generation of virus-specific memory CD8⁺ T cells. Moreover, over-expression of survivin with bcl-xL, a downstream molecule of NF-κB and intracellular target of costimulation that controls survival, in Cd28^−/− or Ox40^−/− CD8⁺ T cells, reversed the defects in the generation of memory T cells in response to viral infection. These results identify c-Myc as a key controller of memory CD8⁺ T cells from costimulatory signals.

Induced Pluripotent Stem Cell as a New Source for Cancer Immunotherapy

The immune system consists of cells, proteins, and other molecules that beside each other have a protective function for the host against foreign pathogens. One of the most essential features of the immune system is distinguishability between self- and non-self-cells. This function has an important role in limiting development and progression of cancer cells. In this case, the immune system can detect tumor cell as a foreign pathogen; so, it can be effective in elimination of tumors in their early phases of development. This ability of the immune system resulted in the development of a novel therapeutic field for cancer treatment using host immune components which is called cancer immunotherapy. The main purpose of cancer immunotherapy is stimulation of a strong immune response against the tumor cells that can result from expressing either the immune activator cytokines in the tumor area or gene-modified immune cells. Because of the problems of culturing and manipulating immune cells ex vivo, in recent years, embryonic stem cell (ESC) and induced pluripotent stem cell (iPSC) have been used as new sources for generation of modified immune stimulatory cells. In this paper, we reviewed some of the progressions in iPSC technology for cancer immunotherapy.

Stem cell-derived tissue-associated regulatory T cells ameliorate the development of autoimmunity

Pluripotent stem cells (PSCs) have the potential to produce almost all of the cells in the body, including regulatory T cells (T_regs). However, the exact conditions required for the development of antigen (Ag)-specific T_regs from PSCs (i.e., PSC-T_regs) are not well delineated. Ag-specific PSC-T_regs can be tissue/organ-associated and migrate to local inflamed tissues/organs to suppress the autoimmune response after adoptive transfer, thereby avoiding potential overall immunosuppression from non-specific T_regs. In this study, we developed a new approach to generate functional Ag-specific T_regs from induced PSCs (iPSCs), i.e., iPSC-T_regs, which had the ability to generate an Ag-specific immunosuppressive response in a murine model of arthritis. We retrovirally transduced murine iPSCs with a construct containing genes of Ag-specific T cell receptor (TCR) and the transcriptional factor FoxP3. We differentiated the iPSCs into Ag-specific iPSC-T_regs using in vitro or in vivo Notch signaling, and demonstrated that adoptive transfer of such T_regs dramatically suppressed autoimmunity in a well-established Ag-induced arthritis model, including the inflammation, joint destruction, cartilage prostaglandin depletion, osteoclast activity, and Th17 production. Our results indicate that PSCs can be used to develop Ag-specific T_regs, which have a therapeutic potential for T_reg-based therapies of autoimmune disorders.

Melanoma Immunotherapy in Mice Using Genetically Engineered Pluripotent Stem Cells

Adoptive cell transfer (ACT) of antigen (Ag)-specific CD8(+) cytotoxic T lymphocytes (CTLs) is a highly promising treatment for a variety of diseases. Naive or central memory T-cell-derived effector CTLs are optimal populations for ACT-based immunotherapy because these cells have a high proliferative potential, are less prone to apoptosis than terminally differentiated cells, and have the higher ability to respond to homeostatic cytokines. However, such ACT with T-cell persistence is often not feasible due to difficulties in obtaining sufficient cells from patients. Here we present that in vitro differentiated HSCs of engineered PSCs can develop in vivo into tumor Ag-specific naive CTLs, which efficiently suppress melanoma growth. Mouse-induced PSCs (iPSCs) were retrovirally transduced with a construct encoding chicken ovalbumin (OVA)-specific T-cell receptors (TCRs) and survival-related proteins (i.e., BCL-xL and survivin). The gene-transduced iPSCs were cultured on the delta-like ligand 1-expressing OP9 (OP9-DL1) murine stromal cells in the presence of murine recombinant cytokines (rFlt3L and rIL-7) for a week. These iPSC-derived cells were then intravenously adoptively transferred into recipient mice, followed by intraperitoneal injection with an agonist α-Notch 2 antibody and cytokines (rFlt3L and rIL-7). Two weeks later, naive OVA-specific CD8(+) T cells were observed in the mouse peripheral lymphatic system, which were responsive to OVA-specific stimulation. Moreover, the mice were resistant to the challenge of B16-OVA melanoma induction. These results indicate that genetically modified stem cells may be used for ACT-based immunotherapy or serve as potential vaccines.

Stem Cell Therapies for Treatment of Liver Disease

Cell therapy is an emerging form of treatment for several liver diseases, but is limited by the availability of donor livers. Stem cells hold promise as an alternative to the use of primary hepatocytes. We performed an exhaustive review of the literature, with a focus on the latest studies involving the use of stem cells for the treatment of liver disease. Stem cells can be harvested from a number of sources, or can be generated from somatic cells to create induced pluripotent stem cells (iPSCs). Different cell lines have been used experimentally to support liver function and treat inherited metabolic disorders, acute liver failure, cirrhosis, liver cancer, and small-for-size liver transplantations. Cell-based therapeutics may involve gene therapy, cell transplantation, bioartificial liver devices, or bioengineered organs. Research in this field is still very active. Stem cell therapy may, in the future, be used as a bridge to either liver transplantation or endogenous liver regeneration, but efficient differentiation and production protocols must be developed and safety must be demonstrated before it can be applied to clinical practice.

Reprogramming of Melanoma Tumor-Infiltrating Lymphocytes to Induced Pluripotent Stem Cells

Induced pluripotent stem cells (iPSCs) derived from somatic cells of patients hold great promise for autologous cell therapies. One of the possible applications of iPSCs is to use them as a cell source for producing autologous lymphocytes for cell-based therapy against cancer. Tumor-infiltrating lymphocytes (TILs) that express programmed cell death protein-1 (PD-1) are tumor-reactive T cells, and adoptive cell therapy with autologous TILs has been found to achieve durable complete response in selected patients with metastatic melanoma. Here, we describe the derivation of human iPSCs from melanoma TILs expressing high level of PD-1 by Sendai virus-mediated transduction of the four transcription factors, OCT3/4, SOX2, KLF4, and c-MYC. TIL-derived iPSCs display embryonic stem cell-like morphology, have normal karyotype, express stem cell-specific surface antigens and pluripotency-associated transcription factors, and have the capacity to differentiate in vitro and in vivo. A wide variety of T cell receptor gene rearrangement patterns in TIL-derived iPSCs confirmed the heterogeneity of T cells infiltrating melanomas. The ability to reprogram TILs containing patient-specific tumor-reactive repertoire might allow the generation of patient- and tumor-specific polyclonal T cells for cancer immunotherapy.

T-cell receptor gene therapy--ready to go viral?

T lymphocytes can be redirected to recognize a tumor target and harnessed to combat cancer by genetic introduction of T-cell receptors of a defined specificity. This approach has recently mediated encouraging clinical responses in patients with cancers previously regarded as incurable. However, despite the great promise, T-cell receptor gene therapy still faces a multitude of obstacles. Identification of epitopes that enable effective targeting of all the cells in a heterogeneous tumor while sparing normal tissues remains perhaps the most demanding challenge. Experience from clinical trials has revealed the dangers associated with T-cell receptor gene therapy and highlighted the need for reliable preclinical methods to identify potentially hazardous recognition of both intended and unintended epitopes in healthy tissues. Procedures for manufacturing large and highly potent T-cell populations can be optimized to enhance their antitumor efficacy. Here, we review the current knowledge gained from preclinical models and clinical trials using adoptive transfer of T-cell receptor-engineered T lymphocytes, discuss the major challenges involved and highlight potential strategies to increase the safety and efficacy to make T-cell receptor gene therapy a standard-of-care for large patient groups.

Inducible T-cell receptor expression in precursor T cells for leukemia control

Co-transplantation of hematopoietic stem cells with those engineered to express leukemia-reactive T-cell receptors (TCRs) and differentiated ex vivo into precursor T cells (preTs) may reduce the risk of leukemia relapse. As expression of potentially self-(leukemia-) reactive TCRs will lead to negative selection or provoke autoimmunity upon thymic maturation, we investigated a novel concept whereby TCR expression set under the control of an inducible promoter would allow timely controlled TCR expression. After in vivo maturation and gene induction, preTs developed potent anti-leukemia effects. Engineered preTs provided protection even after repeated leukemia challenges by giving rise to effector and central memory cells. Importantly, adoptive transfer of TCR-transduced allogeneic preTs mediated anti-leukemia effect without evoking graft-versus-host disease (GVHD). Earlier transgene induction forced CD8(+) T-cell development was required to obtain a mature T-cell subset of targeted specificity, allowed engineered T cells to efficiently pass positive selection and abrogated the endogenous T-cell repertoire. Later induction favored CD4 differentiation and failed to produce a leukemia-reactive population emphasizing the dominant role of positive selection. Taken together, we provide new functional insights for the employment of TCR-engineered precursor cells as a controllable immunotherapeutic modality with significant anti-leukemia activity.

Utilizing regulatory T cells against rheumatoid arthritis

Regulatory T (Treg) cells are essential for normal immune surveillance systems, and their dysfunction leads to development of diseases, such as autoimmune disorders. CD4⁺CD25⁺ Treg cells are well-known suppressive cells, which express the transcription factor Foxp3, are indispensable for the maintenance of immune self-tolerance and homeostasis by suppressing aberrant or excessive immune response. Other Foxp3⁻ Treg cells include Tr1, Th3, CD8⁺CD28^−/−, and Qa1-restricted T cells; however, the contribution of these Treg cells to self-tolerance, immune homeostasis as well as preventing autoimmunity is not well defined. Here, we discuss the phenotypes and function of Foxp3⁺ Treg cells and the potential use of such Treg cells against rheumatoid arthritis (RA). Of note, even though most expanded populations of Foxp3⁺ Treg cells exhibit suppressive activity, tissue-associated or antigen-specific Treg cells appear superior in suppressing local autoimmune disorders such as RA. In addition, utilizing tissue-associated Foxp3⁺ Treg cells from stem cells may stable Foxp3 expression and avoid induction of a potentially detrimental systemic immunosuppression.

Application of Induced Pluripotent Stem Cells in Liver Diseases

Tens of millions of patients are affected by liver disease worldwide. Many of these patients can benefit from therapy involving hepatocyte transplantation. Liver transplantation is presently the only proven treatment for many medically refractory liver diseases including end-stage liver failure and inherited metabolic liver disease. However, the shortage in transplantable livers prevents over 40% of listed patients per year from receiving a liver transplant; many of these patients die before receiving an organ offer or become too sick to transplant. Therefore, new therapies are needed to supplement whole-organ liver transplantation and reduce mortality on waiting lists worldwide. Furthermore, the remarkable regenerative capacity of hepatocytes in vivo is exemplified by the increasing number of innovative cell-based therapies and animal models of human liver disorders. Induced pluripotent stem cells (iPSCs) have similar properties to those of embryonic stem cells (ESCs) but bypass the ethical concerns of embryo destruction. Therefore, generation of hepatocyte-like cells (HLCs) using iPSC technology may be beneficial for the treatment of severe liver diseases, screening of drug toxicities, basic research of several hepatocytic disorders, and liver transplantation. Here we briefly summarize the growing number of potential applications of iPSCs for treatment of liver disease.

Establishment and identification of induced pluripotent stem cells in liver cancer patients

OBJECTIVE

To induce pluripotent stem (IPS) cells from fibrocytes that are separated from liver cancer patients.

METHODS

The fibrocytes were reprogrammed to IPS cells by lentiviral vector, stained and identified by immunohistochemistry.

RESULTS

The IPS cells were successfully established from fibrocytes after infection, and IPS cell clones formed in round shape under a microscopy. The induction rate was 0.013%±0.007%. No tumor formed at the back of nude mice within 8 weeks after the inoculation of cell clones. However, tetatoma appeared in nude mice within 1 week after IPS inoculation. A few tumors formed in nude mice within 4 weeks after the inoculation of cell clones. However, subcutaneous tumors formed within 1 week after IPS inoculation. The induced IPS cells showed three germ layers in tetatoma. Nanog and OCT4 in the induced IPS cells showed hypomethylation. SSEA-A, TRA-1-6-, TRA-1-81 and Nanog were highly expressed in the induced IPS cells, indicating the IPS cells possessed the similar ability as the stem cells.

CONCLUSIONS

The IPS cells of liver cancer patients can be established effectively from fibrocytes and can be cultured stably in vitro, which provides an approach for the treatment of intermediate or advanced stage liver cancer.

Modulation of autoimmune diseases by iPS cells

Autoimmune disease is typically caused by the activated self-reacted immune cells. The mainstream treatment to autoimmune disorders is composed of different mechanisms of immunosuppression. In recent years, a new subtype of T cells called regulatory T (Treg) cells have been identified to maintain the immune homeostasis in terms of suppressing the activated immune components. According to this discovery, it is suggested that treating autoimmune patients by supplementing Treg cells would be a good choice. However, due to their natural scarcity, it is difficult to isolate a desired number of Treg for this therapeutical approach. Here, we report that by using stem cells, especially the induced pluripotent stem (iPS) cells, we are able to generate a significant amount of Treg cells for the autoimmune prevention and treatment.

How (specific) would like your T-cells today? Generating T-cell therapeutic function through TCR-gene transfer

T-cells are central players in the immune response against both pathogens and cancer. Their specificity is solely dictated by the T-cell receptor (TCR) they clonally express. As such, the genetic modification of T lymphocytes using pathogen- or cancer-specific TCRs represents an appealing strategy to generate a desired immune response from peripheral blood lymphocytes. Moreover, notable objective clinical responses were observed in terminally ill cancer patients treated with TCR-gene modified cells in several clinical trials conducted recently. Nevertheless, several key aspects of this approach are the object of intensive research aimed at improving the reliability and efficacy of this strategy. Herein, we will survey recent studies in the field of TCR-gene transfer dealing with the improvement of this approach and its application for the treatment of malignant, autoimmune, and infectious diseases.

Programming of regulatory T cells from pluripotent stem cells and prevention of autoimmunity

Regulatory T (Treg) cells are being used to treat autoimmunity and prevent organ rejection; however, Treg cell-based therapies have been hampered by the technical limitation in obtaining a high number of functional Treg cells. In this study, we show how to generate functional Treg cells from induced pluripotent stem (iPS) cells and to determine the potential role of such cells for Treg cell-based immunotherapy against autoimmunity in a therapeutic setting. Ligation of a Notch ligand and transduction of the gene Foxp3 induce iPS cells to differentiate into Treg cells. Expression of Foxp3 and coculture on Notch ligand-expressing stromal cells augment expression of CD3, TCR, CD4, CD25, and CTLA-4 on iPS cell-differentiated Treg cells, which are able to secrete TGF-β and IL-10 both in vivo and in vitro. Importantly, adoptive transfer of iPS cell-derived Treg cells expressing large amounts of Foxp3 and Bcl-x(L) significantly suppresses host immune responses and reduces arthritis development within murine models. These data suggest that Notch signaling and Foxp3 regulate the development and function of Treg cells derived from iPS cells. Our results provide a novel approach for generating potentially therapeutic Treg cells for the treatment of autoimmune diseases.

Challenges in T cell receptor gene therapy

The function of T lymphocytes as orchestrators and effectors of the adaptive immune response is directed by the specificity of their T cell receptors (TCRs). By transferring into T cells the genes encoding antigen-specific receptors, the functional activity of large populations of T cells can be redirected against defined targets including virally infected or cancer cells. The potential of therapeutic T cells to traffic to sites of disease, to expand and to persist after a single treatment remains a major advantage over the currently available immunotherapies that use monoclonal antibodies. Here we review recent progress in the field of TCR gene therapy, outlining challenges to its successful implementation and the strategies being used to overcome them. We detail strategies used in the optimization of affinity and surface expression of the introduced TCR, the choice of T cell subpopulations for gene transfer, and the promotion of persistence of gene-modified T cells in vivo. We review the safety concerns surrounding the use of gene-modified T cells in patients, discussing emerging solutions to these problems, and describe the increasingly positive results from the use of gene-modified T cells in recent clinical trials of adoptive cellular immunotherapy. The increasing sophistication of measures to ensure the safety of engineered T cells is accompanied by an increasing number of clinical trials: these will be essential to guide the effective translation of cellular immunotherapy from the laboratory to the bedside.