Engineering better chimeric antigen receptor T cells

Inhibition of Calcium Signaling Prevents Exhaustion and Enhances Anti-Leukemia Efficacy of CAR-T Cells via SOCE-Calcineurin-NFAT and Glycolysis Pathways

Chimeric antigen receptor (CAR) T cells are potent agents for recognizing and eliminating tumors, and have achieved remarkable success in the treatment of patients with refractory leukemia and lymphoma. However, dysfunction of T cells, including exhaustion, is an inevitable obstacle for persistent curative effects. Here, the authors initially found that calcium signaling is hyperactivated via sustained tonic signaling in CAR-T cells. Next, it is revealed that the store-operated calcium entry (SOCE) inhibitor BTP-2, but not the calcium chelator BAPTA-AM, markedly diminishes CAR-T cell exhaustion and terminal differentiation of CAR-T cells in both tonic signaling and tumor antigen exposure models. Furthermore, BTP-2 pretreated CAR-T cells show improved antitumor potency and prolonged survival in vivo. Mechanistically, transcriptome and metabolite analyses reveal that treatment with BTP-2 significantly downregulate SOCE-calcineurin-nuclear factor of activated T-cells (NFAT) and glycolysis pathways. Together, the results indicate that modulating the SOCE-calcineurin-NFAT pathway in CAR-T cells renders them resistant to exhaustion, thereby yielding CAR products with enhanced antitumor potency.

Payload Delivery: Engineering Immune Cells to Disrupt the Tumour Microenvironment

Although chimeric antigen receptor (CAR) T cells have shown impressive clinical success against haematological malignancies such as B cell lymphoma and acute lymphoblastic leukaemia, their efficacy against non-haematological solid malignancies has been largely disappointing. Solid tumours pose many additional challenges for CAR T cells that have severely blunted their potency, including homing to the sites of disease, survival and persistence within the adverse conditions of the tumour microenvironment, and above all, the highly immunosuppressive nature of the tumour milieu. Gene engineering approaches for generating immune cells capable of overcoming these hurdles remain an unmet therapeutic need and ongoing area of research. Recent advances have involved gene constructs for membrane-bound and/or secretable proteins that provide added effector cell function over and above the benefits of classical CAR-mediated cytotoxicity, rendering immune cells not only as direct cytotoxic effectors against tumours, but also as vessels for payload delivery capable of both modulating the tumour microenvironment and orchestrating innate and adaptive anti-tumour immunity. We discuss here the novel concept of engineered immune cells as vessels for payload delivery into the tumour microenvironment, how these cells are better adapted to overcome the challenges faced in a solid tumour, and importantly, the novel gene engineering approaches required to deliver these more complex polycistronic gene constructs.

Chimeric Antigen Receptor T-Cell Therapy in Lung Cancer: Potential and Challenges

Chimeric antigen receptor T (CAR-T) cell therapy has exhibited a substantial clinical response in hematological malignancies, including B-cell leukemia, lymphoma, and multiple myeloma. Therefore, the feasibility of using CAR-T cells to treat solid tumors is actively evaluated. Currently, multiple basic research projects and clinical trials are being conducted to treat lung cancer with CAR-T cell therapy. Although numerous advances in CAR-T cell therapy have been made in hematological tumors, the technology still entails considerable challenges in treating lung cancer, such as on−target, of−tumor toxicity, paucity of tumor-specific antigen targets, T cell exhaustion in the tumor microenvironment, and low infiltration level of immune cells into solid tumor niches, which are even more complicated than their application in hematological tumors. Thus, progress in the scientific understanding of tumor immunology and improvements in the manufacture of cell products are advancing the clinical translation of these important cellular immunotherapies. This review focused on the latest research progress of CAR-T cell therapy in lung cancer treatment and for the first time, demonstrated the underlying challenges and future engineering strategies for the clinical application of CAR-T cell therapy against lung cancer.

Nanocomplex-Mediated In Vivo Programming to Chimeric Antigen Receptor-M1 Macrophages for Cancer Therapy

Chimeric antigen receptor-T (CAR-T) cell immunotherapy has shown impressive clinical outcomes for hematologic malignancies. However, its broader applications are challenged due to its complex ex vivo cell-manufacturing procedures and low therapeutic efficacy against solid tumors. The limited therapeutic effects are partially due to limited CAR-T cell infiltration to solid tumors and inactivation of CAR-T cells by the immunosuppressive tumor microenvironment. Here, a facile approach is presented to in vivo program macrophages, which can intrinsically penetrate solid tumors, into CAR-M1 macrophages displaying enhanced cancer-directed phagocytosis and anti-tumor activity. In vivo injected nanocomplexes of macrophage-targeting nanocarriers and CAR-interferon-γ-encoding plasmid DNA induce CAR-M1 macrophages that are capable of CAR-mediated cancer phagocytosis, anti-tumor immunomodulation, and inhibition of solid tumor growth. Together, this study describes an off-the-shelf CAR-macrophage therapy that is effective for solid tumors and avoids the complex and costly processes of ex vivo CAR-cell manufacturing.

Combination strategies to maximize the benefits of cancer immunotherapy

Immunotherapies such as immune checkpoint blockade (ICB) and adoptive cell therapy (ACT) have revolutionized cancer treatment, especially in patients whose disease was otherwise considered incurable. However, primary and secondary resistance to single agent immunotherapy often results in treatment failure, and only a minority of patients experience long-term benefits. This review article will discuss the relationship between cancer immune response and mechanisms of resistance to immunotherapy. It will also provide a comprehensive review on the latest clinical status of combination therapies (e.g., immunotherapy with chemotherapy, radiation therapy and targeted therapy), and discuss combination therapies approved by the US Food and Drug Administration. It will provide an overview of therapies targeting cytokines and other soluble immunoregulatory factors, ACT, virotherapy, innate immune modifiers and cancer vaccines, as well as combination therapies that exploit alternative immune targets and other therapeutic modalities. Finally, this review will include the stimulating insights from the 2020 China Immuno-Oncology Workshop co-organized by the Chinese American Hematologist and Oncologist Network (CAHON), the China National Medical Product Administration (NMPA) and Tsinghua University School of Medicine.

An optimized protocol for the retroviral transduction of mouse CD4 T cells

Transduction of primary T cells has become prominent with the introduction of chimeric antigen receptor T-cell therapy. Although there are many protocols for the transduction of human T cells, it remains a challenge to transduce murine T cells. We present an optimized protocol for the retroviral transduction of murine CD4 T cells, which overcomes major challenges including large-scale production and long-term culturing of transduced cells. The optimized protocol combines high transduction efficiency with a low rate of cell death. For complete details on the use and execution of this protocol, please refer to Eremenko et al., 2019.

Strategic Variants of CSP Delivered as SynDNA Vaccines Demonstrate Heterogeneity of Immunogenicity and Protection from Plasmodium Infection in a Murine Model

Malaria infects millions of people every year, and despite recent advances in controlling disease spread, such as vaccination, it remains a global health concern. The circumsporozoite protein (CSP) has long been acknowledged as a key target in antimalarial immunity. Leveraging the DNA vaccine platform against this formidable pathogen, the following five synthetic DNA vaccines encoding variations of CSP were designed and studied: 3D7, GPI1, ΔGPI, TM, and DD2. Among the single CSP antigen constructs, a range of immunogenicity was observed with ΔGPI generating the most robust immunity. In an intravenous (i.v.) sporozoite challenge, the best protection among vaccinated mice was achieved by ΔGPI, which performed almost as well as the monoclonal antibody 311 (MAb 311) antibody control. Further analyses revealed that ΔGPI develops high-molecular-weight multimers in addition to monomeric CSP. We then compared the immunity generated by ΔGPI versus synDNA mimics for the antimalaria vaccines RTS,S and R21. The anti-CSP antibody responses induced were similar among these three immunogens. T cell responses demonstrated that ΔGPI induced a more focused anti-CSP response. In an infectious mosquito challenge, all three of these constructs generated inhibition of liver-stage infection as well as immunity from blood-stage parasitemia. This study demonstrates that synDNA mimics of complex malaria immunogens can provide substantial protection as can a novel synDNA vaccine ΔGPI.

Chimeric Antigen Receptor-Engineered Natural Killer (CAR NK) Cells in Cancer Treatment; Recent Advances and Future Prospects

Natural Killer (NK) cells are critical members of the innate immunity lymphocytes and have a critical role in host defense against malignant cells. Adoptive cell therapy (ACT) using chimeric antigen receptor (CAR) redirects the specificity of the immune cell against a target-specific antigen. ACT has recently created an outstanding opportunity for cancer treatment. Unlike CAR-armored T cells which hadnsome shortcomings as the CAR-receiving construct, Major histocompatibility complex (MHC)-independency, shorter lifespan, the potential to produce an off-the-shelf immune product, and potent anti-tumor properties of the NK cells has introduced NK cells as a potent alternative target for expression of CAR. Here, we aim to provide an updated overview on the current improvements in CAR NK design and immunobiology and describe the potential of CAR-modified NK cells as an alternative “off-the-shelf” carrier of CAR. We also provide lists for the sources of NK cells in the process of CAR NK cell production, different methods for transduction of the CAR genetic sequence to NK cells, the differences between CAR T and CAR NK, and CAR NK-targeted tumor antigens in current studies. Additionally, we provide data on recently published preclinical and clinical studies of CAR NK therapy and a list of finished and ongoing clinical trials. For achieving CAR NK products with higher efficacy and safety, we discuss current challenges in transduction and expansion of CAR NK cells, CAR NK therapy side effects, and challenges that limit the optimal efficacy of CAR NK cells and recommend possible solutions to enhance the persistence, function, safety, and efficacy of CAR NK cells with a special focus on solid tumors.

An overview of multiplexed analyses of CAR T-cell therapies: insights and potential

INTRODUCTION

Cancer immunotherapy is a rapidly growing field with exponential advancement in engineered immune cell-based therapies. For instance, an engineered chimeric antigen receptor (CAR) can be introduced in T-cells or other immune cells and adoptively transferred to target and kill cancer cells in hematologic malignancies or solid tumors. The first CAR-T-cell (CAR-T) therapy has been developed against CD19, a B-cell marker expressed on lymphoma and lymphoblastic leukemia. To allow for personalized treatment, proteomics approaches could provide insights into biomarkers for CAR-T therapy efficacy and toxicity.

AREAS COVERED

We researched the most recent technology methods of biomarker evaluation used in the laboratory and clinical setting. Publications of CAR-T biomarkers were then systematically reviewed to provide a narrative of the most validated biomarkers of CAR-T efficacy and toxicity. Examples of biomarkers include CAR-T functionality and phenotype as well as interleukin-6 and other cytokines.

EXPERT COMMENTARY

Biomarkers of CAR-T efficacy and toxicity have been identified, but still need to be validated and standardized across institutions. Moreover, few are used in the clinical setting due to limitations in real-time technology. Expansion of biomarker research could provide better understanding of patient response and risk of life-threatening side effects with potential for improved precision medicine.

Cytolytic Activity of CAR T Cells and Maintenance of Their CD4+ Subset Is Critical for Optimal Antitumor Activity in Preclinical Solid Tumor Models

Simple Summary

Adoptively transferred T cells expressing recombinant chimeric antigen receptors (CAR T cells) have been approved for the therapy of hematological malignancies of the B cell lineage. However, CAR T cell therapy for patients with solid tumors so far has shown limited benefits. Correlative clinical studies of patients with hematological malignancies have suggested that less differentiated CAR T cells have improved anti-leukemic activity. We have therefore investigated the role of differentiation on the anti-tumor activity of CAR T cells targeting the solid tumor antigen HER2 in preclinical models. We utilized different activation/expansion protocols, and explored whether different co-stimulatory domains in the CAR construct influence the short- and long-term efficacy of HER2-CAR T cells. We demonstrate that the CAR T cell product with the highest proportion of effector cells and maintaining a good balance of CD4+/CD8+ cells is the most effective against solid tumors both in vitro and in vivo.

Abstract

Correlative clinical studies of hematological malignancies have implicated that less differentiated, CD8+-dominant CAR T cell products have greater antitumor activity. Here, we have investigated whether the differentiation status of CAR T cell products affects their antitumor activity in preclinical models of solid tumors. We explored if different activation/expansion protocols, as well as different co-stimulatory domains in the CAR construct, influence the short- and long-term efficacy of CAR T cells against HER2-positive tumors. We generated T cell products that range from the most differentiated (CD28.z; OKT3-antiCD28/RPMI expansion) to the least differentiated (41BB.z; OKT3-RetroNectin/LymphoONE expansion), as judged by cell surface expression of the differentiation markers CCR7 and CD45RA. While the effect of differentiation status was variable with regard to antigen-specific cytokine production, the most differentiated CD28.z CAR T cell products, which were enriched in effector memory T cells, had the greatest target-specific cytolytic activity in vitro. These products also had a greater proliferative capacity and maintained CD4+ T cells upon repeated stimulation in vitro. In vivo, differentiated CD28.z CAR T cells also had the greatest antitumor activity, resulting in complete response. Our results highlight that it is critical to optimize CAR T cell production and that optimal product characteristics might depend on the targeted antigen and/or cancer.

Novel strategies for immuno-oncology breakthroughs with cell therapy

Cell therapy has evolved rapidly in the past several years with more than 250 clinical trials ongoing around the world. While more indications of cellular therapy with chimeric antigen receptor - engineered T cells (CAR-T) are approved for hematologic malignancies, new concepts and strategies of cellular therapy for solid tumors are emerging and are discussed. These developments include better selections of targets by shifting from tumor-associated antigens to personalized tumor-specific neoantigens, an enhancement of T cell trafficking by breaking the stromal barriers, and a rejuvenation of exhausted T cells by targeting immunosuppressive mechanisms in the tumor microenvironment (TME). Despite significant remaining challenges, we believe that cell therapy will once again lead and revolutionize cancer immunotherapy before long because of the maturation of technologies in T cell engineering, target selection and T cell delivery. This review highlighted the recent progresses reported at the 2020 China Immuno-Oncology Workshop co-organized by the Chinese American Hematologist and Oncologist Network (CAHON), the China National Medical Product Administration (NMPA), and Tsinghua University.

Emerging therapies for relapsed/refractory multiple myeloma: CAR-T and beyond

The pace of innovation of multiple myeloma therapy in recent years is remarkable with the advent of monoclonal antibodies and the approval of novel agents with new mechanisms of action. Emerging therapies are on the horizon for clinical approval with significant implications in extending patient survival and advancing closer to the goal of a cure, especially in areas of immunotherapy such as chimeric antigen receptor T cells, bispecific T cell engager antibodies, antibody drug conjugates, newer generations of monoclonal antibodies, and small molecule inhibitor and modulators. This review provides an update of current myeloma therapeutics in active preclinical and early clinical development and discusses the mechanism of action of several classes of novel therapeutics.

The role of NFAT2/miR-20a-5p signaling pathway in the regulation of CD8+ naïve T cells activation and differentiation

T cell dysfunction is a common characteristic in leukemia patients that significantly impacts clinical treatment and prognosis. However, the mechanism underlying T cell dysfunction and its reversal remains unclear. In this study, in accordance with our previous findings, we found that the expression of NFAT2 and pri-miR-17 ~ 92 are lower in peripheral blood CD3⁺ T cells from chronic myelogenous leukemia (CML) patients by gene expression analysis. We further demonstrate that the NFAT2-induced activation, differentiation, and expression of cytokines in human umbilical cord blood CD8⁺ naïve T cells are miR-20a-5p dependent. We also preliminarily explored the relationship between NFAT2 and miR-20a-5p in naive T cells. These results suggest that NFAT2 and miR-20a are crucial for regulating functional CD8⁺ T cells. Additionally, their alteration may be related to CD8⁺ T cell dysfunction in CML patients; thus, NFAT2 and miR-20a-5p may be considered potential targets for revising T cell function in leukemia immunotherapy.

Targeting Solid Tumors Using CD3 Bispecific Antibodies

Immunotherapies to treat cancer have made tremendous progress over the past decade. In particular, T cell-directed therapies have gained considerable attention with CD3 bispecific antibodies and CAR T cells showing potent responses against hematologic tumors. At present, the ability to adapt these therapeutics to treat solid tumors is less established. Herein, we discuss recent advances in T cell-engaging CD3 bispecific antibodies targeting solid tumors, potential mechanisms of resistance, and future prospects. A better understanding of the mechanisms of immune evasion in solid tumors will enable the development of strategies to overcome this resistance and inform choices of therapeutic combinations.

TOX as a potential target for immunotherapy in lymphocytic malignancies

TOX (thymocyte selection-associated HMG BOX) is a member of a family of transcriptional factors that contain the highly conserved high mobility group box (HMG-box) region. Increasing studies have shown that TOX is involved in maintaining tumors and promoting T cell exhaustion. In this review, we summarized the biological functions of TOX and its contribution as related to lymphocytic malignancies. We also discussed the potential role of TOX as an immune biomarker and target in immunotherapy for hematological malignancies.