Circumventing tolerance to a human MDM2-derived tumor antigen by TCR gene transfer

Targeting MDM2 in malignancies is a promising strategy for overcoming resistance to anticancer immunotherapy

MDM2 has been established as a biomarker indicating poor prognosis for individuals undergoing immune checkpoint inhibitor (ICI) treatment for different malignancies by various pancancer studies. Specifically, patients who have MDM2 amplification are vulnerable to the development of hyperprogressive disease (HPD) following anticancer immunotherapy, resulting in marked deleterious effects on survival rates. The mechanism of MDM2 involves its role as an oncogene during the development of malignancy, and MDM2 can promote both metastasis and tumor cell proliferation, which indirectly leads to disease progression. Moreover, MDM2 is vitally involved in modifying the tumor immune microenvironment (TIME) as well as in influencing immune cells, eventually facilitating immune evasion and tolerance. Encouragingly, various MDM2 inhibitors have exhibited efficacy in relieving the TIME suppression caused by MDM2. These results demonstrate the prospects for breakthroughs in combination therapy using MDM2 inhibitors and anticancer immunotherapy.

T cell receptor therapeutics: immunological targeting of the intracellular cancer proteome

The T cell receptor (TCR) complex is a naturally occurring antigen sensor that detects, amplifies and coordinates cellular immune responses to epitopes derived from cell surface and intracellular proteins. Thus, TCRs enable the targeting of proteins selectively expressed by cancer cells, including neoantigens, cancer germline antigens and viral oncoproteins. As such, TCRs have provided the basis for an emerging class of oncology therapeutics. Herein, we review the current cancer treatment landscape using TCRs and TCR-like molecules. This includes adoptive cell transfer of T cells expressing endogenous or engineered TCRs, TCR bispecific engagers and antibodies specific for human leukocyte antigen (HLA)-bound peptides (TCR mimics). We discuss the unique complexities associated with the clinical development of these therapeutics, such as HLA restriction, TCR retrieval, potency assessment and the potential for cross-reactivity. In addition, we highlight emerging clinical data that establish the antitumour potential of TCR-based therapies, including tumour-infiltrating lymphocytes, for the treatment of diverse human malignancies. Finally, we explore the future of TCR therapeutics, including emerging genome editing methods to safely enhance potency and strategies to streamline patient identification.

The screening, identification, design and clinical application of tumor-specific neoantigens for TCR-T cells

Recent advances in neoantigen research have accelerated the development of tumor immunotherapies, including adoptive cell therapies (ACTs), cancer vaccines and antibody-based therapies, particularly for solid tumors. With the development of next-generation sequencing and bioinformatics technology, the rapid identification and prediction of tumor-specific antigens (TSAs) has become possible. Compared with tumor-associated antigens (TAAs), highly immunogenic TSAs provide new targets for personalized tumor immunotherapy and can be used as prospective indicators for predicting tumor patient survival, prognosis, and immune checkpoint blockade response. Here, the identification and characterization of neoantigens and the clinical application of neoantigen-based TCR-T immunotherapy strategies are summarized, and the current status, inherent challenges, and clinical translational potential of these strategies are discussed.

Antigen-Specific TCR-T Cells for Acute Myeloid Leukemia: State of the Art and Challenges

The cytogenetic abnormalities and molecular mutations involved in acute myeloid leukemia (AML) lead to unique treatment challenges. Although adoptive T-cell therapies (ACT) such as chimeric antigen receptor (CAR) T-cell therapy have shown promising results in the treatment of leukemias, especially B-cell malignancies, the optimal target surface antigen has yet to be discovered for AML. Alternatively, T-cell receptor (TCR)-redirected T cells can target intracellular antigens presented by HLA molecules, allowing the exploration of a broader territory of new therapeutic targets. Immunotherapy using adoptive transfer of WT1 antigen-specific TCR-T cells, for example, has had positive clinical successes in patients with AML. Nevertheless, AML can escape from immune system elimination by producing immunosuppressive factors or releasing several cytokines. This review presents recent advances of antigen-specific TCR-T cells in treating AML and discusses their challenges and future directions in clinical applications.

Genetic Modification of T Cells for the Immunotherapy of Cancer

Immunotherapy is a beneficial treatment approach for multiple cancers, however, current therapies are effective only in a small subset of patients. Adoptive cell transfer (ACT) is a facet of immunotherapy where T cells targeting the tumor cells are transferred to the patient with several primary forms, utilizing unmodified or modified T cells: tumor-infiltrating lymphocytes (TIL), genetically modified T cell receptor transduced T cells, and chimeric antigen receptor (CAR) transduced T cells. Many clinical trials are underway investigating the efficacy and safety of these different subsets of ACT, as well as trials that combine one of these subsets with another type of immunotherapy. The main challenges existing with ACT are improving clinical responses and decreasing adverse events. Current research focuses on identifying novel tumor targeting T cell receptors, improving safety and efficacy, and investigating ACT in combination with other immunotherapies.

Recent advances in biomaterial-boosted adoptive cell therapy

Adoptive immunotherapies based on the transfer of functional immune cells hold great promise in treating a wide range of malignant diseases, especially cancers, autoimmune diseases, and infectious diseases. However, manufacturing issues and biological barriers lead to the insufficient population of target-selective effector cells at diseased sites after adoptive transfer, hindering effective clinical translation. The convergence of immunology, cellular biology, and materials science lays a foundation for developing biomaterial-based engineering platforms to overcome these challenges. Biomaterials can be rationally designed to improve ex vivo immune cell expansion, expedite functional engineering, facilitate protective delivery of immune cells in situ, and navigate the infused cells in vivo. Herein, this review presents a comprehensive summary of the latest progress in biomaterial-based strategies to enhance the efficacy of adoptive cell therapy, focusing on function-specific biomaterial design, and also discusses the challenges and prospects of this field.

A broad and systematic approach to identify B cell malignancy-targeting TCRs for multi-antigen-based T cell therapy

CAR T cell therapy has shown great promise for the treatment of B cell malignancies. However, antigen-negative escape variants often cause disease relapse, necessitating the development of multi-antigen-targeting approaches. We propose that a T cell receptor (TCR)-based strategy would increase the number of potential antigenic targets, as peptides from both intracellular and extracellular proteins can be recognized. Here, we aimed to isolate a broad range of promising TCRs targeting multiple antigens for treatment of B cell malignancies. As a first step, 28 target genes for B cell malignancies were selected based on gene expression profiles. Twenty target peptides presented in human leukocyte antigen (HLA)-A∗01:01, -A∗24:02, -B∗08:01, or -B∗35:01 were identified from the immunopeptidome of B cell malignancies and used to form peptide-HLA (pHLA)-tetramers for T cell isolation. Target-peptide-specific CD8 T cells were isolated from HLA-mismatched healthy donors and subjected to a stringent stepwise selection procedure to ensure potency and eliminate cross-reactivity. In total, five T cell clones specific for FCRL5 in HLA-A∗01:01, VPREB3 in HLA-A∗24:02, and BOB1 in HLA-B∗35:01 recognized B cell malignancies. For all three specificities, TCR gene transfer into CD8 T cells resulted in cytokine production and efficient killing of multiple B cell malignancies. In conclusion, using this systematic approach we successfully identified three promising TCRs for T cell therapy against B cell malignancies.

TCR-T Immunotherapy: The Challenges and Solutions

T cell receptor-engineered T cell (TCR-T) therapy is free from the limit of surface antigen expression of the target cells, which is a potential cellular immunotherapy for cancer treatment. Significant advances in the treatment of hematologic malignancies with cellular immunotherapy have aroused the interest of researchers in the treatment of solid tumors. Nevertheless, the overall efficacy of TCR-T cell immunotherapy in solid tumors was not significantly high when compared with hematological malignancies. In this article, we pay attention to the barriers of TCR-T cell immunotherapy for solid tumors, as well as the strategies affecting the efficacy of TCR-T cell immunotherapy. To provide some reference for researchers to better overcome the impact of TCR-T cell efficiency in solid tumors.

Characterization and modulation of anti-αβTCR antibodies and their respective binding sites at the βTCR chain to enrich engineered T cells

T cell engineering strategies offer cures to patients and have entered clinical practice with chimeric antibody-based receptors; αβT cell receptor (αβTCR)-based strategies are, however, lagging behind. To allow a more rapid and successful translation to successful concepts also using αβTCRs for engineering, incorporating a method for the purification of genetically modified T cells, as well as engineered T cell deletion after transfer into patients, could be beneficial. This would allow increased efficacy, reduced potential side effects, and improved safety of newly to-be-tested lead structures. By characterizing the antigen-binding interface of a good manufacturing process (GMP)-grade anti-αβTCR antibody, usually used for depletion of αβT cells from stem cell transplantation products, we developed a strategy that allows for the purification of untouched αβTCR-engineered immune cells by changing 2 amino acids only in the TCRβ chain constant domain of introduced TCR chains. Alternatively, we engineered an antibody that targets an extended mutated interface of 9 amino acids in the TCRβ chain constant domain and provides the opportunity to further develop depletion strategies of engineered immune cells.

Evolution of CD8+ T Cell Receptor (TCR) Engineered Therapies for the Treatment of Cancer

Engineered T cell receptor T (TCR-T) cell therapy has facilitated the generation of increasingly reliable tumor antigen-specific adaptable cellular products for the treatment of human cancer. TCR-T cell therapies were initially focused on targeting shared tumor-associated peptide targets, including melanoma differentiation and cancer-testis antigens. With recent technological developments, it has become feasible to target neoantigens derived from tumor somatic mutations, which represents a highly personalized therapy, since most neoantigens are patient-specific and are rarely shared between patients. TCR-T therapies have been tested for clinical efficacy in treating solid tumors in many preclinical studies and clinical trials all over the world. However, the efficacy of TCR-T therapy for the treatment of solid tumors has been limited by a number of factors, including low TCR avidity, off-target toxicities, and target antigen loss leading to tumor escape. In this review, we discuss the process of deriving tumor antigen-specific TCRs, including the identification of appropriate tumor antigen targets, expansion of antigen-specific T cells, and TCR cloning and validation, including techniques and tools for TCR-T cell vector construction and expression. We highlight the achievements of recent clinical trials of engineered TCR-T cell therapies and discuss the current challenges and potential solutions for improving their safety and efficacy, insights that may help guide future TCR-T studies in cancer.

Building on Synthetic Immunology and T Cell Engineering: A Brief Journey Through the History of Chimeric Antigen Receptors

Advancement in our understanding of immune cell recognition and emerging cellular engineering technologies during the last decades made active manipulation of the T cell response possible. Synthetic immunology is providing us with an expanding set of composite receptor molecules capable to reprogram immune cell function in a predefined fashion. Since the first prototypes in the late 1980s, the design of chimeric antigen receptors (CARs; T-bodies, immunoreceptors), has followed a clear line of stepwise improvements from antigen-redirected targeting to designed "living factories" delivering transgenic products on demand. Building on basic research and creative clinical exploration, CAR T cell therapy has been achieving spectacular success in the treatment of hematologic malignancies, now beginning to improve the outcome of cancer patients. In this study, we briefly review the history of CARs and outline how the progress in the basic understanding of T cell recognition and of cell engineering technologies made novel therapies possible.

Generation of Epstein-Barr Virus Antigen-Specific T Cell Receptors Recognizing Immunodominant Epitopes of LMP1, LMP2A, and EBNA3C for Immunotherapy

Epstein-Barr virus (EBV) infections in healthy individuals are usually cleared by immune cells, wherein CD8⁺ T lymphocytes play the most important role. However, in some immunocompromised individuals, EBV infections can lead to the development of cancer in B, T, natural killer (NK) cells and epithelial cells. Most EBV-associated cancers express a limited number of virus-specific antigens such as latent membrane proteins (LMP1 and LMP2) and nuclear proteins (EBNA1, -2, EBNA3A, -B, -C, and EBNA-LP). These antigens represent true tumor-specific antigens and can be considered useful targets for T cell receptor (TCR) gene therapy to treat EBV-associated diseases. We used a TCR isolation platform based on a single major histocompatibility complex class I (MHC I) K562 cell library for the detection, isolation, and re-expression of TCRs targeting immunodominant peptide MHC (pMHC). Mature dendritic cells (mDCs) were pulsed with in vitro-transcribed (ivt) RNA encoding for the selected antigen to stimulate autologous T cells. The procedure allowed the mDCs to select an immunogenic epitope of the antigen for processing and presentation on the cell surface in combination with the most suitable MHC I molecule. We isolated eight EBV-specific TCRs. They recognize various pMHCs of EBV antigens LMP1, LMP2A, and EBNA3C, some of them described previously and some newly identified in this study. The TCR genes were molecularly cloned into retroviral vectors and the resultant TCR-engineered T cells secreted interferon-γ after antigen contact and were able to lyse tumor cells. The EBV-specific TCRs can be used as a basis for the generation of a TCR library, which provides a valuable source of TCRs for the production of EBV-specific T cells to treat EBV-associated diseases in patients with different MHC I types.

Arming Immune Cells for Battle: A Brief Journey through the Advancements of T and NK Cell Immunotherapy

Simple Summary

This review is intended to provide an overview on the history and recent advances of T cell and natural killer (NK) cell-based immunotherapy. While the thymus was discovered as the origin of T cells in the 1960s, and NK cells were first described in 1975, the clinical application of adoptive cell therapies (ACT) only began in the early 1980s with the first lymphokine activated killer (LAK) cell product for the treatment of cancer patients. Over the past decades, further immunotherapies have been developed, including ACT using cytokine-induced killer (CIK) cells, products based on the NK cell line NK-92 as well as specific T and NK cell preparations. Recent advances have successfully improved the effectiveness of T, NK, CIK or NK-92 cells towards tumor-targeting antigens generated by genetic engineering of the immune cells. Herein, we summarize the promising development of ACT over the past decades in the fight against cancer.

Abstract

The promising development of adoptive immunotherapy over the last four decades has revealed numerous therapeutic approaches in which dedicated immune cells are modified and administered to eliminate malignant cells. Starting in the early 1980s, lymphokine activated killer (LAK) cells were the first ex vivo generated NK cell-enriched products utilized for adoptive immunotherapy. Over the past decades, various immunotherapies have been developed, including cytokine-induced killer (CIK) cells, as a peripheral blood mononuclear cells (PBMCs)-based therapeutic product, the adoptive transfer of specific T and NK cell products, and the NK cell line NK-92. In addition to allogeneic NK cells, NK-92 cell products represent a possible “off-the-shelf” therapeutic concept. Recent approaches have successfully enhanced the specificity and cytotoxicity of T, NK, CIK or NK-92 cells towards tumor-specific or associated target antigens generated by genetic engineering of the immune cells, e.g., to express a chimeric antigen receptor (CAR). Here, we will look into the history and recent developments of T and NK cell-based immunotherapy.

Wilms tumor gent 1 (WT1)-specific adoptive immunotherapy in hematologic diseases

As an attractive tumor-associated antigen (TAA), Wilms tumor gene 1 (WT1) is usually overexpressed in malignant hematological diseases. In recent years, WT1-specific adoptive immunotherapy has been the "hot spot" for tumor treatment. The main immunotherapeutic techniques associated with WT1 include WT1-specific cytotoxic T lymphocytes (CTLs), vaccine, and T cell receptor (TCR) gene therapy. WT1-based adoptive immunotherapy exhibited promising anti-tumorous effect with tolerable safety. There are still many limitations needed to be improved including the weak immunogenetics of WT1, immune tolerance, and short persistence of the immune response. In this review, we summarized the progress of productive technologies and the clinical or preclinical investigations of WT1-specific immunotherapy in hematological diseases.

TCR Redirected T Cells for Cancer Treatment: Achievements, Hurdles, and Goals

Adoptive T cell therapy (ACT) is a rapidly evolving therapeutic approach designed to harness T cell specificity and function to fight diseases. Based on the evidence that T lymphocytes can mediate a potent anti-tumor response, initially ACT solely relied on the isolation, in vitro expansion, and infusion of tumor-infiltrating or circulating tumor-specific T cells. Although effective in a subset of cases, in the first ACT clinical trials several patients experienced disease progression, in some cases after temporary disease control. This evidence prompted researchers to improve ACT products by taking advantage of the continuously evolving gene engineering field and by improving manufacturing protocols, to enable the generation of effective and long-term persisting tumor-specific T cell products. Despite recent advances, several challenges, including prioritization of antigen targets, identification, and optimization of tumor-specific T cell receptors, in the development of tools enabling T cells to counteract the immunosuppressive tumor microenvironment, still need to be faced. This review aims at summarizing the major achievements, hurdles and possible solutions designed to improve the ACT efficacy and safety profile in the context of liquid and solid tumors.

The Quest for the Best: How TCR Affinity, Avidity, and Functional Avidity Affect TCR-Engineered T-Cell Antitumor Responses

Over the past decades, adoptive transfer of T cells has revolutionized cancer immunotherapy. In particular, T-cell receptor (TCR) engineering of T cells has marked important milestones in developing more precise and personalized cancer immunotherapies. However, to get the most benefit out of this approach, understanding the role that TCR affinity, avidity, and functional avidity play on how TCRs and T cells function in the context of tumor-associated antigen (TAA) recognition is vital to keep generating improved adoptive T-cell therapies. Aside from TCR-related parameters, other critical factors that govern T-cell activation are the effect of TCR co-receptors on TCR–peptide-major histocompatibility complex (pMHC) stabilization and TCR signaling, tumor epitope density, and TCR expression levels in TCR-engineered T cells. In this review, we describe the key aspects governing TCR specificity, T-cell activation, and how these concepts can be applied to cancer-specific TCR redirection of T cells.

Engineering CD4+ T Cells to Enhance Cancer Immunity

This review presents key advances in combining T cell receptor (TCR) gene transfer to redirect T-cell specificity with gene engineering in order to enhance cancer-protective immune function. We discuss how emerging insights might be applied to CD4+ T cells. Although much attention has been paid to the role of CD8+ cytotoxic T cells in tumour protection, we provide convincing evidence that CD4+ helper T cells play a critical role in cancer immune responses in animal models and also in patients. We demonstrate that genetic engineering technologies provide exciting opportunities to extend the specificity range of CD4+ T cells from MHC class-II-presented epitopes to include peptides presented by MHC class I molecules. Functional enhancement of tumour immunity can improve the sensitivity of T cells to cancer antigens, promote survival in a hostile tumour microenvironment, boost cancer-protective effector mechanisms and enable the formation of T-cell memory. Engineered cancer-specific CD4+ T cells may contribute to protective immunity by a direct pathway involving cancer cell killing, and by an indirect pathway that boosts the function, persistence and memory formation of CD8+ T cells.

Orthotopic T-Cell Receptor Replacement-An "Enabler" for TCR-Based Therapies

Natural adaptive immunity co-evolved with pathogens over millions of years, and adoptive transfer of non-engineered T cells to fight infections or cancer so far exhibits an exceptionally safe and functional therapeutic profile in clinical trials. However, the personalized nature of therapies using virus-specific T cells, donor lymphocyte infusion, or tumor-infiltrating lymphocytes makes implementation in routine clinical care difficult. In principle, genetic engineering can be used to make T-cell therapies more broadly applicable, but so far it significantly alters the physiology of cells. We recently demonstrated that orthotopic T-cell receptor (TCR) replacement (OTR) by clustered regularly interspaced short palindromic repeats (CRISPR)/ CRISPR-associated protein 9 (Cas9) can be used to generate engineered T cells with preservation of near-physiological function. In this review, we present the current status of OTR technology development and discuss its potential for TCR-based therapies. By providing the means to combine the therapeutic efficacy and safety profile of physiological T cells with the versatility of cell engineering, OTR can serve as an "enabler" for TCR-based therapies.

The Diagnostic, Prognostic, and Therapeutic Potential of Adaptive Immune Receptor Repertoire Profiling in Cancer

Lymphocytes play a critical role in antitumor immune responses. They are directly targeted by some therapies, and the composition and spatial organization of intratumor T-cell populations is prognostic in some cancer types. A better understanding of lymphocyte population dynamics over the course of disease and in response to therapy is urgently needed to guide therapy decisions and to develop new therapy targets. Deep sequencing of the repertoire of antigen receptor-encoding genes expressed in a lymphocyte population has become a widely used approach for profiling the population's immune status. Lymphocyte antigen receptor repertoire deep sequencing data can be used to assess the clonal richness and diversity of lymphocyte populations; to track clone members over time, between tissues, and across lymphocyte subsets; to detect clonal expansion; and to detect the recruitment of new clones into a tissue. Repertoire sequencing is thus a critical complement to other methods of lymphocyte and immune profiling in cancer. This review describes the current state of knowledge based on repertoire sequencing studies conducted on human cancer patients, with a focus on studies of the T-cell receptor beta chain locus. The review then outlines important questions left unanswered and suggests future directions for the field.

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.

T cell receptor-engineered T cells for leukemia immunotherapy

At present, refractory and relapse are major issues for leukemia therapy and a major cause of allogeneic hematopoietic stem cell transplant failure. Over the last decade, many studies have demonstrated that adoptive cancer antigen-specific T cell therapy is an effective option for leukemia therapy. Recently, T cell immunotherapy studies have mainly focused on chimeric antigen receptor- and T cell receptor-engineered T cells. Clinical trials involving chimeric antigen receptor-engineered T cells have been a major breakthrough and became a novel therapy for leukemia. As another potential therapy for leukemia, clinical application of TCR-engineered T cells remains in its infancy. This article presents a review of the current status of anti-leukemia immunotherapy using leukemia antigen-specific TCR-engineered T cells.

A Potent Tumor-Reactive p53-Specific Single-Chain TCR without On- or Off-Target Autoimmunity In Vivo

Genetic engineering of T cells with a T cell receptor (TCR) targeting tumor antigen is a promising strategy for cancer immunotherapy. Inefficient expression of the introduced TCR due to TCR mispairing may limit the efficacy and adversely affect the safety of TCR gene therapy. Here, we evaluated the safety and therapeutic efficiency of an optimized single-chain TCR (scTCR) specific for an HLA-A2.1-restricted (non-mutated) p53(264-272) peptide in adoptive T cell transfer (ACT) models using our unique transgenic mice expressing human p53 and HLA-A2.1 that closely mimic the human setting. Specifically, we showed that adoptive transfer of optimized scTCR-redirected T cells does not induce on-target and off-target autoimmunity. Furthermore, ACT resulted in full tumor protection and led to a long-lived effective, antigen-specific memory T cell response in syngeneic and xenograft models. Taken together, the study demonstrated that our scTCR specific for the broadly expressed tumor-associated antigen p53(264-272) can eradicate p53⁺A2.1⁺ tumor cells without inducing off-target or self-directed toxicities in mouse models of ACT. These data strongly support the improved safety and therapeutic efficacy of high-affinity p53scTCR for TCR-based immunotherapy of p53-associated malignancies.

IL-10 inducible CD8+ regulatory T-cells are enriched in patients with multiple myeloma and impact the generation of antigen-specific T-cells

Tumor-mediated immunosuppression via regulatory T-cells is a key player among the various immune-escape mechanisms in multiple myeloma. We analyzed the generation, distribution, function and immunophenotype of CD8+CD28- regulatory T-cells in patients with multiple myeloma. Functionality of CD8+CD28- T-cells was assessed by immunological assays using ex vivo generated antigen-specific T-cells from patients with plasma cell dyscrasias and healthy donors. Detailed analysis of distribution, immunophenotype and cytotoxic potential of CD8+CD28- T-cells was performed by flow cytometry and ELISA. We found that the amount of CD8+CD28- T-cells was directly correlated with the suppression of antigen-specific T-cell responses in patients with plasma cell dyscrasia. Analyzing the CD8+CD28- T-cells in detail, increased numbers of these cells were observed in the bone marrow (i.e., tumor microenvironment) of patients with plasma cell dyscrasia. Furthermore, we identified the expression of lymphocyte function-associated antigen 1 (LFA-1) as a marker of immunosuppression and defined the CD8+CD28-CD57+LFA-1high population as the relevant immunosuppressive compartment. These regulatory T-cells act as immunosuppressors via soluble factors and incubation with IL-10 augmented their immunosuppressive capacity. The immunosuppressive regulatory network of IL-10 and the CD8+CD28-CD57+LFA-1high regulatory T-cells show unique characteristics and contribute to the tumor immune escape mechanism in patients with multiple myeloma.

Principles of adoptive T cell therapy in cancer

Adoptive cell therapy (ACT) utilizing either tumor-infiltrating lymphocyte (TIL)-derived T cells or T cells genetically engineered to express tumor recognizing receptors has emerged as a powerful and potentially curative therapy for several cancers. Many ACT-based therapies have recently entered late-phase clinical testing, with several T cell therapies already achieving regulatory approval for the treatment of patients with B cell malignancies. In this review, we briefly outline the principles of adoptively transferred T cells for the treatment of cancer.

Cellular immunotherapy on primary multiple myeloma expanded in a 3D bone marrow niche model

Bone marrow niches support multiple myeloma, providing signals and cell-cell interactions essential for disease progression. A 3D bone marrow niche model was developed, in which supportive multipotent mesenchymal stromal cells and their osteogenic derivatives were co-cultured with endothelial progenitor cells. These co-cultured cells formed networks within the 3D culture, facilitating the survival and proliferation of primary CD138+ myeloma cells for up to 28 days. During this culture, no genetic drift was observed within the genomic profile of the primary myeloma cells, indicating a stable outgrowth of the cultured CD138+ population. The 3D bone marrow niche model enabled testing of a novel class of engineered immune cells, so called TEGs (αβT cells engineered to express a defined γδTCR) on primary myeloma cells. TEGs were engineered and tested from both healthy donors and myeloma patients. The added TEGs were capable of migrating through the 3D culture, exerting a killing response towards the primary myeloma cells in 6 out of 8 donor samples after both 24 and 48 hours. Such a killing response was not observed when adding mock transduced T cells. No differences were observed comparing allogeneic and autologous therapy. The supporting stromal microenvironment was unaffected in all conditions after 48 hours. When adding TEG therapy, the 3D model surpassed 2D models in many aspects by enabling analyses of specific homing, and both on- and off-target effects, preparing the ground for the clinical testing of TEGs. The model allows studying novel immunotherapies, therapy resistance mechanisms and possible side-effects for this incurable disease.

An optimized single chain TCR scaffold relying on the assembly with the native CD3-complex prevents residual mispairing with endogenous TCRs in human T-cells

Immunotherapy of cancer envisions the adoptive transfer of T-cells genetically engineered with tumor-specific heterodimeric α/β T-cell receptors (TCRα/β). However, potential mispairing of introduced TCRα/β-chains with endogenous β/α-ones may evoke unpredictable autoimmune reactivities. A novel single chain (sc)TCR format relies on the fusion of the Vα-Linker-Vβ-fragment to the TCR Cβ-domain and coexpression of the TCR Cα-domain capable of recruiting the natural CD3-complex for full and hence, native T-cell signaling. Here, we tested whether such a gp100(280-288)- or p53(264-272) tumor antigen-specific scTCR is still prone to mispairing with TCRα. In a human Jurkat-76 T-cell line lacking endogenous TCRs, surface expression and function of a scTCR could be reconstituted by any cointroduced TCRα-chain indicating mispairing to take place on a molecular basis. In contrast, transduction into human TCRα/β-positive T-cells revealed that mispairing is largely reduced. Competition experiments in Jurkat-76 confirmed the preference of dcTCR to selfpair and to spare scTCR. This also allowed for the generation of dc/scTCR-modified cytomegalovirus/tumor antigen-bispecific T-cells to augment T-cell activation in CMV-infected tumor patients. Residual mispairing was prevented by strenghtening the Vα-Li-Vβ-fragment through the design of a novel disulfide bond between a Vα- and a linker-resident residue close to Vβ. Multimer-stainings, and cytotoxicity-, IFNγ-secretion-, and CFSE-proliferation-assays, the latter towards dendritic cells endogenously processing RNA-electroporated gp100 antigen proved the absence of hybrid scTCR/TCRα-formation without impairing avidity of scTCR/Cα in T-cells. Moreover, a fragile cytomegalovirus pp65(495-503)-specific scTCR modified this way acquired enhanced cytotoxicity. Thus, optimized scTCR/Cα inhibits residual TCR mispairing to accomplish safe adoptive immunotherapy for bulk endogenous TCRα/β-positive T-cells.

T Cell Receptor Profiling in Type 1 Diabetes

PURPOSE OF REVIEW

The genetic susceptibility and dominant protection for type 1 diabetes (T1D) associated with human leukocyte antigen (HLA) haplotypes, along with minor risk variants, have long been thought to shape the T cell receptor (TCR) repertoire and eventual phenotype of autoreactive T cells that mediate β-cell destruction. While autoantibodies provide robust markers of disease progression, early studies tracking autoreactive T cells largely failed to achieve clinical utility.

RECENT FINDINGS

Advances in acquisition of pancreata and islets from T1D organ donors have facilitated studies of T cells isolated from the target tissues. Immunosequencing of TCR α/β-chain complementarity determining regions, along with transcriptional profiling, offers the potential to transform biomarker discovery. Herein, we review recent studies characterizing the autoreactive TCR signature in T1D, emerging technologies, and the challenges and opportunities associated with tracking TCR molecular profiles during the natural history of T1D.

T-Cell Receptor-Engineered Cells for the Treatment of Hematologic Malignancies

Recent attention in adoptive immunotherapy for hematologic malignancies has focused on lymphocytes expressing chimeric antigen receptors. An alternative technique to redirect the immune system toward cancer cells involves the use of T-cells carrying an engineered tumor-recognizing T-cell receptor (TCR). This approach allows targeting of surface or intracellular/nuclear proteins as long as they are processed and presented on the cell surface by human leukocyte antigen molecules. Several trials in advanced solid tumors, particularly melanoma and synovial sarcoma, support the validity of this strategy, although tumor responses have often been short-lived. Emerging data from patients with multiple myeloma and myeloid neoplasms suggest that the benefit of TCR-modified cells may extend to blood cancers. Methodological refinements may be necessary to increase the in vivo persistence and functionality of these cells. Particularly with affinity-enhanced TCRs, however, more effective therapies may increase the potential for serious toxicity due to the unexpected on- or off-target reactivity.

Tools to define the melanoma-associated immunopeptidome

Immunotherapies have been traditionally applied in malignant melanoma, which represent one of the most immunogenic tumours. Recently, immune checkpoint modulation has shown high therapeutic efficacy and may provide long-term survival in a significant proportion of affected patients. T cells are the major players in tumour rejection and recognize tumour cells predominantly in an MHC-dependent way. The immunopeptidome comprises the peptide repertoire presented by MHC class I and II molecules on the surface of the body's cells including tumour cells. To understand characteristics of suitable rejection antigens as well as respective effective T-cell responses, determination of the immunopeptidome is of utmost importance. Suitable rejection antigens need to be further characterized and validated not only to systematically improve current therapeutic approaches, but also to develop individualized treatment options. In this review, we report on current tools to explore the immunopeptidome in human melanoma and discuss current understanding and future developments to specifically detect and select those antigens that may be most relevant and promising for effective tumour rejection.

Trial Watch: Adoptively transferred cells for anticancer immunotherapy

Immunotherapies aimed at strengthening immune effector responses against malignant cells are growing at exponential rates. Alongside, the impressive benefits obtained by patients with advanced melanoma who received adoptively transferred tumor-infiltrating lymphocytes (TILs) have encouraged the scientific community to pursue adoptive cell transfer (ACT)-based immunotherapy. ACT involves autologous or allogenic effector lymphocytes that are generally obtained from the peripheral blood or resected tumors, expanded and activated ex vivo, and administered to lymphodepleted patients. ACT may be optionally associated with chemo- and/or immunotherapeutics, with the overall aim of enhancing the proliferation, persistence and functionality of infused cells, as well as to ensure their evolution in an immunological permissive local and systemic microenvironment. In addition, isolated lymphocytes can be genetically engineered to endow them with the ability to target a specific tumor-associated antigen (TAA), to increase their lifespan, and/or to reduce their potential toxicity. The infusion of chimeric antigen receptor (CAR)-expressing cytotoxic T lymphocytes redirected against CD19 has shown promising clinical efficacy in patients with B-cell malignancies. Accordingly, the US Food and Drug Administration (FDA) has recently granted 'breakthrough therapy' designation to a CAR-based T-cell therapy (CTL019) for patients with B-cell malignancies. Considerable efforts are now being devoted to the development of efficient ACT-based immunotherapies for non-hematological neoplasms. In this Trial Watch, we summarize recent clinical advances on the use of ACT for oncological indications.

Evolving adoptive cellular therapies in urological malignancies

Immunotherapies have long been used to treat urological cancers but rarely lead to cure. In the past 5 years, success of immune checkpoint inhibition has led to a resurgence of enthusiasm for immunotherapy in the treatment of solid tumours. Increased understanding of tumour immune biology, technological advancements of gene transfer and cell culture, and improved clinical infrastructures for routine delivery of cell products, has made cell-based immunotherapeutics a real prospect for cancer therapy. These scientific and clinical activities, attempting to exploit the innate and adaptive immune systems for therapeutic gain, are well exemplified by the urological malignancies of renal, bladder, prostate, and penile cancer, a group of anatomically localised diseases, each with a distinct biology and different immunotherapeutic challenges. In this Review, we present the results of clinical studies investigating autologous cellular therapies in urological malignancies. Specifically, we discuss the rationale for upcoming studies, and how novel therapies and adoptive cell combinations can be used for personalised cancer therapy.

Technical Considerations for the Generation of Adoptively Transferred T Cells in Cancer Immunotherapy

A significant function of the immune system is the surveillance and elimination of aberrant cells that give rise to cancer. Even when tumors are well established and metastatic, immune-mediated spontaneous regressions have been documented. While there are have been various forms of immunotherapy, one of the most widely studied for almost 40 years is adoptive cellular immunotherapy, but its success has yet to be fully realized. Adoptive cell transfer (ACT) is a therapeutic modality that has intrigued physicians and researchers for its many theoretical benefits. Preclinical investigations and human trials have utilized natural killer (NK) cells, dendritic cells (DC), macrophages, T-cells or B-cells for ACT with the most intense research focused on T-cell ACT. T-cells are exquisitely specific to the target of its T-cell receptor (TCR), thus potentially reducing the amount of collateral damage and off-target effects from treatment. T-cells also possess a memory subset that may reduce the risk of recurrence of a cancer after the successful treatment of the primary disease. There are several options for the source of T-cells used in the generation of cells for ACT. Perhaps the most widely known source is T-cells generated from tumor-infiltrating lymphocytes (TILs). However, studies have also employed peripheral blood mononuclear cells (PBMCs), lymph nodes, and even induced pluripotent stem cells (IPSCs) as a source of T-cells. Several important technical considerations exist regarding benefits and limitations of each source of T-cells. Unique aspects of T-cells factor into their ability to be efficacious in ACT including the total number of cells available for ACT, the anti-tumor efficacy on a per cell basis, the repertoire of TCRs specific to tumor cells, and their ability to traffic to various organs that harbor tumor. Current research is attempting to unlock the full potential of these cells to effectively and safely treat cancer.

T-cell receptor transfer for boosting HIV-1-specific T-cell immunity in HIV-1-infected patients

OBJECTIVES

Strategies to cure HIV-1 infection require the eradication of viral reservoirs. An innovative approach for boosting the cytotoxic T-lymphocyte response is the transfer of T-cell receptors (TCRs). Previously, we have shown that electroporation of TCR-encoding mRNA is able to reprogram CD8 T cells derived from healthy donors. So far, it is unknown whether the transfer of HIV-1-specific TCRs is capable to reprogram CD8 T cells of HIV-1-infected patients. To assess the efficiency of TCR-transfer by mRNA electroporation and the functionality of reprogramed T cells in HIV-1-infected patients, we performed an in-vitro analysis of TCR-transfer into T cells from HIV-1-infected patients in various stages of disease and from healthy controls.

METHODS

Peripheral blood mononuclear cells from 16 HIV-1-infected patients (nine HLA-A02-positive, seven HLA-A02-negative) and from five healthy controls were electroporated with mRNA-constructs encoding TCRs specific for the HLA-A02/HIV-1-gag p17 epitope SLYNTVATL (SL9). Functionality of the TCRs was measured by γIFN-ELISpot assays.

RESULTS

SL9/TCR transfection into peripheral blood mononuclear cells from both HLA-A02-positive and HLA-A02-negative HIV-1-infected patients and from healthy blood donors reprogramed T cells for recognition of SL9-presenting HLA-A02-positive cells in γIFN-ELISpot assays. SL9/TCR-transfer into T cells from an immunodeficient AIDS patient could induce recognition of SL9-expressing target cells only after reversion of T-cell dysfunction by antiretroviral therapy.

CONCLUSION

The transfer of HIV-1-p17-specific TCRs into T cells is functional both in HIV-1-infected patients as well as in healthy blood donors. TCR-transfer is a promising method to boost the immune system against HIV-1.

Cellular immunotherapy for malignant gliomas

INTRODUCTION

Cancer immunotherapy has made much progress in recent years. Clinical trials evaluating a variety of immunotherapeutic approaches are underway in patients with malignant gliomas. Thanks to recent advancements in cell engineering technologies, infusion of ex vivo prepared immune cells have emerged as promising strategies of cancer immunotherapy.

AREAS COVERED

Herein, the authors review recent and current studies using cellular immunotherapies for malignant gliomas. Specifically, they cover the following areas: a) cellular vaccine approaches using tumor cell-based or dendritic cell (DC)-based vaccines, and b) adoptive cell transfer (ACT) approaches, including lymphokine-activated killer (LAK) cells, γδ T cells, tumor-infiltrating lymphocytes (TIL), chimeric antigen receptor (CAR)-T cells and T-cell receptor (TCR) transduced T cells.

EXPERT OPINION

While some of the recent studies have shown promising results, the ultimate success of cellular immunotherapy in brain tumor patients would require improvements in the following areas: 1) feasibility in producing cellular therapeutics; 2) identification and characterization of targetable antigens given the paucity and heterogeneity of tumor specific antigens; 3) the development of strategies to promote effector T-cell trafficking; 4) overcoming local and systemic immune suppression, and 5) proper interpretation of imaging data for brain tumor patients receiving immunotherapy.

RhoB Mediates Phosphoantigen Recognition by Vγ9Vδ2 T Cell Receptor

Human Vγ9Vδ2 T cells respond to tumor cells by sensing elevated levels of phosphorylated intermediates of the dysregulated mevalonate pathway, which is translated into activating signals by the ubiquitously expressed butyrophilin A1 (BTN3A1) through yet unknown mechanisms. Here, we developed an unbiased, genome-wide screening method that identified RhoB as a critical mediator of Vγ9Vδ2 TCR activation in tumor cells. Our results show that Vγ9Vδ2 TCR activation is modulated by the GTPase activity of RhoB and its redistribution to BTN3A1. This is associated with cytoskeletal changes that directly stabilize BTN3A1 in the membrane, and the subsequent dissociation of RhoB from BTN3A1. Furthermore, phosphoantigen accumulation induces a conformational change in BTN3A1, rendering its extracellular domains recognizable by Vγ9Vδ2 TCRs. These complementary events provide further evidence for inside-out signaling as an essential step in the recognition of tumor cells by a Vγ9Vδ2 TCR.

[Immunological tumor therapy]

Tumor cells could fundamentally be recognized and eliminated by the immune system but malignant cells are able to escape the immune surveillance system. The idea of immunotherapy of cancer is to activate, modulate and amplify the host immune response or to genetically equip the immune repertoire of patients with anti-tumor specificities and effectors. In recent years, a variety of promising immunotherapy strategies have been developed, such as bispecific, multispecific and immunoregulatory antibodies, gene-modified T lymphocytes and tumor vaccines. Some drugs have already been approved and others are available for patients in clinical trials. This article presents the current anti-tumor immune strategies and their molecular basis. Even though further research is needed in some areas, such as the establishment of biomarkers for targeted therapy, duration of therapeutic activity and compatibility of combined strategies, cancer immunotherapy is likely to be a key component in oncological treatment concepts in the very near future.

Expression of a dominant T-cell receptor can reduce toxicity and enhance tumor protection of allogeneic T-cell therapy

Due to the lack of specificity for tumor antigens, allogeneic T-cell therapy is associated with graft-versus-host disease. Enhancing the anti-tumor specificity while reducing the graft-versus-host disease risk of allogeneic T cells has remained a research focus. In this study, we demonstrate that the introduction of 'dominant' T-cell receptors into primary murine T cells can suppress the expression of endogenous T-cell receptors in a large proportion of the gene-modified T cells. Adoptive transfer of allogeneic T cells expressing a 'dominant' T-cell receptor significantly reduced the graft-versus-host toxicity in recipient mice. Using two bone marrow transplant models, enhanced anti-tumor activity was observed in the presence of reduced graft-versus-host disease. However, although transfer of T-cell receptor gene-modified allogeneic T cells resulted in the elimination of antigen-positive tumor cells and improved the survival of treated mice, it was associated with accumulation of T cells expressing endogenous T-cell receptors and the development of delayed graft-versus-host disease. The in-vivo deletion of the engineered T cells, mediated by endogenous mouse mammary tumor virus MTV8 and MTV9, abolished graft-versus-host disease while retaining significant anti-tumor activity of adoptively transferred T cells. Together, this study shows that the in-vitro selection of allogeneic T cells expressing high levels of a 'dominant' T-cell receptor can lower acute graft-versus-host disease and enhance anti-tumor activity of adoptive cell therapy, while the in-vivo outgrowth of T cells expressing endogenous T-cell receptors remains a risk factor for the delayed onset of graft-versus-host disease.

Chimeric Antigen Receptor T-Cell Therapy for the Community Oncologist

: The field of cancer immunotherapy has rapidly progressed in the past decade as several therapeutic modalities have entered into the clinic. One such immunotherapy that has shown promise in the treatment of cancer is the use of chimeric antigen receptor (CAR)-modified T lymphocytes. CARs are engineered receptors constructed from antigen recognition regions of antibodies fused to T-cell signaling and costimulatory domains that can be used to reprogram a patient's T cells to specifically target tumor cells. CAR T-cell therapy has demonstrated sustained complete responses for some patients with advanced leukemia, and a number of CAR therapies are being evaluated in clinical studies. CAR T-cell therapy-associated toxicities, including cytokine release syndrome, macrophage activation syndrome, and tumor lysis syndrome, have been observed and effectively managed in the clinic. In patients with significant clinical responses, sustained B-cell aplasia has also been observed and is a marker of CAR T-cell persistence that might provide long-term disease control. Education on CAR T-cell therapy efficacy and safety management is critical for clinicians and patients who are considering this novel type of treatment. In the present report, the current landscape of CAR T-cell therapy, the effective management of patients undergoing treatment, and which patients are the most suitable candidates for current trials are discussed.

IMPLICATIONS FOR PRACTICE

The present report describes the current status of chimeric antigen receptor (CAR) T lymphocytes as an immunotherapy for patients with relapsed or refractory B-cell malignancies. CAR T cells targeting CD19, a protein expressed on many B-cell malignancies, typically induce high complete response rates in patients with B-cell leukemia or lymphoma who have very limited therapeutic options. Recent clinical trial results of CD19 CAR T-cell therapies and the management of CAR T-cell-associated adverse events are discussed. The present report will therefore inform physicians regarding the efficacy and safety of CAR T cells as a therapy for B-cell malignancies.

TCR gene-modified T cells can efficiently treat established hepatitis C-associated hepatocellular carcinoma tumors

The success in recent clinical trials using T cell receptor (TCR)-genetically engineered T cells to treat melanoma has encouraged the use of this approach toward other malignancies and viral infections. Although hepatitis C virus (HCV) infection is being treated with a new set of successful direct anti-viral agents, potential for virologic breakthrough or relapse by immune escape variants remains. Additionally, many HCV+ patients have HCV-associated disease, including hepatocellular carcinoma (HCC), which does not respond to these novel drugs. Further exploration of other approaches to address HCV infection and its associated disease are highly warranted. Here, we demonstrate the therapeutic potential of PBL-derived T cells genetically engineered with a high-affinity, HLA-A2-restricted, HCV NS3:1406-1415-reactive TCR. HCV1406 TCR-transduced T cells can recognize naturally processed antigen and elicit CD8-independent recognition of both peptide-loaded targets and HCV+ human HCC cell lines. Furthermore, these cells can mediate regression of established HCV+ HCC in vivo. Our results suggest that HCV TCR-engineered antigen-reactive T cells may be a plausible immunotherapy option to treat HCV-associated malignancies, such as HCC.

Enhancing adoptive T cell immunotherapy with microRNA therapeutics

Adoptive T cell-based immunotherapies can mediate complete and durable regressions in patients with advanced cancer, but current response rates remain inadequate. Maneuvers to improve the fitness and antitumor efficacy of transferred T cells have been under extensive exploration in the field. Small non-coding microRNAs have emerged as critical modulators of immune system homeostasis and T cell immunity. Here, we summarize recent advances in our understanding of the role of microRNAs in regulating T cell activation, differentiation, and function. We also discuss how microRNA therapeutics could be employed to fine-tune T cell receptor signaling and enhance T cell persistence and effector functions, paving the way for the next generation of adoptive immunotherapies.

Engineered T cells can fight malignant T cells

In this issue of Blood, Mamonkin and colleagues report genetically engineered T cells with specificity for the lineage marker CD5 selectively kill T-lymphoma but not normal T cells, although both express the CD5 target antigen.

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.

Cancer gene therapy with T cell receptors and chimeric antigen receptors

Viral and non-viral gene transfer technologies have been used to efficiently generate therapeutic T cells with desired cancer-specificity. Chimeric antigen receptors (CARs) redirect T cell specificity toward antibody-recognized antigens expressed on the surface of cancer cells, while T cell receptors (TCRs) extend the range of targets to include intracellular tumor antigens. CAR redirected T cells specific for the B cell differentiation antigen CD19 have shown dramatic efficacy in the treatment of B cell malignancies, while TCR-redirected T cells have shown benefits in patients suffering from solid cancer. In this review we will present strategies to optimize CAR and TCR function, and discuss the importance of target antigen selection to enhance tumor specificity, while reducing on-target and off-target toxicity.

Untouched GMP-Ready Purified Engineered Immune Cells to Treat Cancer

PURPOSE

Engineering T cells with receptors to redirect the immune system against cancer has most recently been described as a scientific breakthrough. However, a main challenge remains the GMP-grade purification of immune cells selectively expressing the introduced receptor in order to reduce potential side effects due to poorly or nonengineered cells.

EXPERIMENTAL DESIGN

In order to test a novel purification strategy, we took advantage of a model γδT cell receptor (TCR), naturally interfering with endogenous TCR expression and designed the optimal retroviral expression cassette to achieve maximal interference with endogenous TCR chains. Following retroviral transduction, nonengineered and poorly engineered immune cells characterized by a high endogenous αβTCR expression were efficiently depleted with GMP-grade anti-αβTCR beads. Next, the engineered immune cells were validated for TCR expression, function against a panel of tumor cell lines and primary tumors and potential allo-reactivity. Engineered immune cells were further validated in two humanized mouse tumor models.

RESULTS

The untouched enrichment of engineered immune cells translated into highly purified receptor-engineered cells with strong antitumor reactivity both in vitro and in vivo. Importantly, this approach eliminated residual allo-reactivity of engineered immune cells. Our data demonstrate that even with long-term suboptimal interference with endogenous TCR chains such as in resting cells, allo-reactivity remained absent and tumor control preserved.

CONCLUSIONS

We present a novel enrichment method for the production of untouched engineered immune cells, ready to be translated into a GMP-grade method and potentially applicable to all receptor-modified cells even if interference with endogenous TCR chains is far from complete.

Genetically modified T cells in cancer therapy: opportunities and challenges

Tumours use many strategies to evade the host immune response, including downregulation or weak immunogenicity of target antigens and creation of an immune-suppressive tumour environment. T cells play a key role in cell-mediated immunity and, recently, strategies to genetically modify T cells either through altering the specificity of the T cell receptor (TCR) or through introducing antibody-like recognition in chimeric antigen receptors (CARs) have made substantial advances. The potential of these approaches has been demonstrated in particular by the successful use of genetically modified T cells to treat B cell haematological malignancies in clinical trials. This clinical success is reflected in the growing number of strategic partnerships in this area that have attracted a high level of investment and involve large pharmaceutical organisations. Although our understanding of the factors that influence the safety and efficacy of these therapies has increased, challenges for bringing genetically modified T-cell immunotherapy to many patients with different tumour types remain. These challenges range from the selection of antigen targets and dealing with regulatory and safety issues to successfully navigating the routes to commercial development. However, the encouraging clinical data, the progress in the scientific understanding of tumour immunology and the improvements in the manufacture of cell products are all advancing the clinical translation of these important cellular immunotherapies.

The New Era of Cancer Immunotherapy: Manipulating T-Cell Activity to Overcome Malignancy

Using the immune system to control cancer has been investigated for over a century. Yet it is only over the last several years that therapeutic agents acting directly on the immune system have demonstrated improved overall survival for cancer patients in phase III clinical trials. Furthermore, it appears that some patients treated with such agents have been cured of metastatic cancer. This has led to increased interest and acceleration in the rate of progress in cancer immunotherapy. Most of the current immunotherapeutic success in cancer treatment is based on the use of immune-modulating antibodies targeting critical checkpoints (CTLA-4 and PD-1/PD-L1). Several other immune-modulating molecules targeting inhibitory or stimulatory pathways are being developed. The combined use of these medicines is the subject of intense investigation and holds important promise. Combination regimens include those that incorporate targeted therapies that act on growth signaling pathways, as well as standard chemotherapy and radiation therapy. In fact, these standard therapies have intrinsic immune-modulating properties that can support antitumor immunity. In the years ahead, adoptive T-cell therapy will also be an important part of treatment for some cancer patients. Other areas which are regaining interest are the use of oncolytic viruses that immunize patients against their own tumors and the use of vaccines against tumor antigens. Immunotherapy has demonstrated unprecedented durability in controlling multiple types of cancer and we expect its use to continue expanding rapidly.