Co-Expansion of Cytokine-Induced Killer Cells and Vγ9Vδ2 T Cells for CAR T-Cell Therapy

Beyond CAR T cells: exploring alternative cell sources for CAR-like cellular therapies

Chimeric antigen receptor (CAR)-T cell therapy has led to remarkable clinical outcomes in the treatment of hematological malignancies. However, challenges remain, such as limited infiltration into solid tumors, inadequate persistence, systemic toxicities, and manufacturing insufficiencies. The use of alternative cell sources for CAR-based therapies, such as natural killer cells (NK), macrophages (MΦ), invariant Natural Killer T (iNKT) cells, γδT cells, neutrophils, and induced pluripotent stem cells (iPSC), has emerged as a promising avenue. By harnessing these cells' inherent cytotoxic mechanisms and incorporating CAR technology, common CAR-T cell-related limitations can be effectively mitigated. We herein present an overview of the tumoricidal mechanisms, CAR designs, and manufacturing processes of CAR-NK cells, CAR-MΦ, CAR-iNKT cells, CAR-γδT cells, CAR-neutrophils, and iPSC-derived CAR-cells, outlining the advantages, limitations, and potential solutions of these therapeutic strategies.

The Spectrum of CAR Cellular Effectors: Modes of Action in Anti-Tumor Immunity

Chimeric antigen receptor-T cells have spearheaded the field of adoptive cell therapy and have shown remarkable results in treating hematological neoplasia. Because of the different biology of solid tumors compared to hematological tumors, response rates of CAR-T cells could not be transferred to solid entities yet. CAR engineering has added co-stimulatory domains, transgenic cytokines and switch receptors to improve performance and persistence in a hostile tumor microenvironment, but because of the inherent cell type limitations of CAR-T cells, including HLA incompatibility, toxicities (cytokine release syndrome, neurotoxicity) and high costs due to the logistically challenging preparation process for autologous cells, the use of alternative immune cells is gaining traction. NK cells and γδ T cells that do not need HLA compatibility or macrophages and dendritic cells with additional properties such as phagocytosis or antigen presentation are increasingly seen as cellular vehicles with potential for application. As these cells possess distinct properties, clinicians and researchers need a thorough understanding of their peculiarities and commonalities. This review will compare these different cell types and their specific modes of action seen upon CAR activation.

CAR-NKT Cells in Asthma: Use of NKT as a Promising Cell for CAR Therapy

NKT cells, unique lymphocytes bridging innate and adaptive immunity, offer significant potential for managing inflammatory disorders like asthma. Activating iNKT induces increasing IFN-γ, TGF-β, IL-2, and IL-10 potentially suppressing allergic asthma. However, their immunomodulatory effects, including granzyme-perforin-mediated cytotoxicity, and expression of TIM-3 and TRAIL warrant careful consideration and targeted approaches. Although CAR-T cell therapy has achieved remarkable success in treating certain cancers, its limitations necessitate exploring alternative approaches. In this context, CAR-NKT cells emerge as a promising approach for overcoming these challenges, potentially achieving safer and more effective immunotherapies. Strategies involve targeting distinct IgE-receptors and their interactions with CAR-NKT cells, potentially disrupting allergen-mast cell/basophil interactions and preventing inflammatory cytokine release. Additionally, targeting immune checkpoints like PDL-2, inducible ICOS, FASL, CTLA-4, and CD137 or dectin-1 for fungal asthma could further modulate immune responses. Furthermore, artificial intelligence and machine learning hold immense promise for revolutionizing NKT cell-based asthma therapy. AI can optimize CAR-NKT cell functionalities, design personalized treatment strategies, and unlock a future of precise and effective care. This review discusses various approaches to enhancing CAR-NKT cell efficacy and longevity, along with the challenges and opportunities they present in the treatment of allergic asthma.

Broadening the horizon: potential applications of CAR-T cells beyond current indications

Engineering immune cells to treat hematological malignancies has been a major focus of research since the first resounding successes of CAR-T-cell therapies in B-ALL. Several diseases can now be treated in highly therapy-refractory or relapsed conditions. Currently, a number of CD19- or BCMA-specific CAR-T-cell therapies are approved for acute lymphoblastic leukemia (ALL), diffuse large B-cell lymphoma (DLBCL), mantle cell lymphoma (MCL), multiple myeloma (MM), and follicular lymphoma (FL). The implementation of these therapies has significantly improved patient outcome and survival even in cases with previously very poor prognosis. In this comprehensive review, we present the current state of research, recent innovations, and the applications of CAR-T-cell therapy in a selected group of hematologic malignancies. We focus on B- and T-cell malignancies, including the entities of cutaneous and peripheral T-cell lymphoma (T-ALL, PTCL, CTCL), acute myeloid leukemia (AML), chronic myeloid leukemia (CML), chronic lymphocytic leukemia (CLL), classical Hodgkin-Lymphoma (HL), Burkitt-Lymphoma (BL), hairy cell leukemia (HCL), and Waldenström's macroglobulinemia (WM). While these diseases are highly heterogenous, we highlight several similarly used approaches (combination with established therapeutics, target depletion on healthy cells), targets used in multiple diseases (CD30, CD38, TRBC1/2), and unique features that require individualized approaches. Furthermore, we focus on current limitations of CAR-T-cell therapy in individual diseases and entities such as immunocompromising tumor microenvironment (TME), risk of on-target-off-tumor effects, and differences in the occurrence of adverse events. Finally, we present an outlook into novel innovations in CAR-T-cell engineering like the use of artificial intelligence and the future role of CAR-T cells in therapy regimens in everyday clinical practice.

Immunotherapies inducing immunogenic cell death in cancer: insight of the innate immune system

Cancer immunotherapies include monoclonal antibodies, cytokines, oncolytic viruses, cellular therapies, and other biological and synthetic immunomodulators. These are traditionally studied for their effect on the immune system's role in eliminating cancer cells. However, some of these therapies have the unique ability to directly induce cytotoxicity in cancer cells by inducing immunogenic cell death (ICD). Unlike general immune stimulation, ICD triggers specific therapy-induced cell death pathways, based on the release of damage-associated molecular patterns (DAMPs) from dying tumour cells. These activate innate pattern recognition receptors (PRRs) and subsequent adaptive immune responses, offering the promise of sustained anticancer drug efficacy and durable antitumour immune memory. Exploring how onco-immunotherapies can trigger ICD, enhances our understanding of their mechanisms and potential for combination strategies. This review explores the complexities of these immunotherapeutic approaches that induce ICD, highlighting their implications for the innate immune system, addressing challenges in cancer treatment, and emphasising the pivotal role of ICD in contemporary cancer research.

Editorial on "Cell Therapy, Bispecific Antibodies and Other Immunotherapies against Cancer"

This Special Issue in Cancers, "Cell Therapy, Bispecific Antibodies and other Immunotherapies Against Cancer", includes interesting reports and reviews on cell therapies and bispecific antibodies [...].

CAR-NKT cell therapy: a new promising paradigm of cancer immunotherapy

Today, cancer treatment is one of the fundamental problems facing clinicians and researchers worldwide. Efforts to find an excellent way to treat this illness continue, and new therapeutic strategies are developed quickly. Adoptive cell therapy (ACT) is a practical approach that has been emerged to improve clinical outcomes in cancer patients. In the ACT, one of the best ways to arm the immune cells against tumors is by employing chimeric antigen receptors (CARs) via genetic engineering. CAR equips cells to target specific antigens on tumor cells and selectively eradicate them. Researchers have achieved promising preclinical and clinical outcomes with different cells by using CARs. One of the potent immune cells that seems to be a good candidate for CAR-immune cell therapy is the Natural Killer-T (NKT) cell. NKT cells have multiple features that make them potent cells against tumors and would be a powerful replacement for T cells and natural killer (NK) cells. NKT cells are cytotoxic immune cells with various capabilities and no notable side effects on normal cells. The current study aimed to comprehensively provide the latest advances in CAR-NKT cell therapy for cancers.

Innate lymphoid cells and innate-like T cells in cancer - at the crossroads of innate and adaptive immunity

Immunotherapies targeting conventional T cells have revolutionized systemic treatment for many cancers, yet only a subset of patients benefit from these approaches. A better understanding of the complex immune microenvironment of tumours is needed to design the next generation of immunotherapeutics. Innate lymphoid cells (ILCs) and innate-like T cells (ILTCs) are abundant, tissue-resident lymphocytes that have recently been shown to have critical roles in many types of cancers. ILCs and ILTCs rapidly respond to changes in their surrounding environment and act as the first responders to bridge innate and adaptive immunity. This places ILCs and ILTCs as pivotal orchestrators of the final antitumour immune response. In this Review, we outline hallmarks of ILCs and ILTCs and discuss their emerging role in antitumour immunity, as well as the pathophysiological adaptations leading to their pro-tumorigenic function. We explore the pleiotropic, in parts redundant and sometimes opposing, mechanisms that underlie the delicate interplay between the different subsets of ILCs and ILTCs. Finally, we highlight their role in amplifying and complementing conventional T cell functions and summarize immunotherapeutic strategies for targeting ILCs and ILTCs in cancer.

CAR γδ T cells for cancer immunotherapy. Is the field more yellow than green?

Engineered immune cell therapy to treat malignancies refractory to conventional therapies is modernizing oncology. Although αβ T cells are time-tested chassis for CAR, potential graft versus host disease (GvHD) apart from cytokine toxicity and antigen escape pose limitations to this approach. αβ T cell malignancy challenges isolation and expansion of therapeutic T cells. Moreover, αβ T cells may pose toxicity risk to inflammation sensitive vital tissues bearing the tumor. The HLA independent, multivalent, versatile and systemic anti-tumor immunity increases the desirability of γδ T cells as an alternate chassis for CAR. Indeed, CD19 γδ CAR T cell therapy to treat advanced lymphoma reached a milestone with the fast track status by FDA. However, reduced tumor-toxicity, homing, in vivo persistence and heterogeneity limits the translation of this therapy. The field is gaining momentum in recent years with optimization of gene delivery approaches and mechanistic insights into co-signaling requirements in γδ T cells. There is a renewed interest in customizing design of CAR guided by the biology of the host immune cells. Progress has been made in the current good manufacturing practice compatible expansion and engineering protocols for the δ1 and δ2 T cells. γδ CAR T cells may find its niche in the clinical situations wherein conventional CAR therapy is less suitable due to propensity for cytokine toxicity or off-tumor effect. As the therapy is moving towards clinical trials, this review chronicles the hitherto progress in the therapeutic engineering of γδ T cells for cancer immunotherapy.

Influence of Culture Conditions on Ex Vivo Expansion of T Lymphocytes and Their Function for Therapy: Current Insights and Open Questions

Ex vivo expansion of T lymphocytes is a central process in the generation of cellular therapies targeted at tumors and other disease-relevant structures, which currently cannot be reached by established pharmaceuticals. The influence of culture conditions on T cell functions is, however, incompletely understood. In clinical applications of ex vivo expanded T cells, so far, a relatively classical standard cell culture methodology has been established. The expanded cells have been characterized in both preclinical models and clinical studies mainly using a therapeutic endpoint, for example antitumor response and cytotoxic function against cellular targets, whereas the influence of manipulations of T cells ex vivo including transduction and culture expansion has been studied to a much lesser detail, or in many contexts remains unknown. This includes the circulation behavior of expanded T cells after intravenous application, their intracellular metabolism and signal transduction, and their cytoskeletal (re)organization or their adhesion, migration, and subsequent intra-tissue differentiation. This review aims to provide an overview of established T cell expansion methodologies and address unanswered questions relating in vivo interaction of ex vivo expanded T cells for cellular therapy.

Vγ9Vδ2 T cells expressing a BCMA—Specific chimeric antigen receptor inhibit multiple myeloma xenograft growth

Vγ9Vδ2 T cells are immune effector cells capable of killing multiple myeloma (MM) cells and have been tested in clinical trials to treat MM patients. To enhance the MM cell killing function of Vγ9Vδ2 T cells, we introduced a BCMA-specific CAR into ex vivo expanded Vγ9Vδ2 T cells through electroporation of the CAR-encoding mRNA. The modified Vγ9Vδ2 T cells displayed a high cytolytic activity against BCMA-expressing MM cell lines in vitro, while sparing BCMA-negative cells, including normal B cells and monocytes. Subsequently, we intravenously injected KMS-11 human MM cells to generate a xenograft mouse model. The treatment of the tumor-bearing mice with Zometa and anti-BCMA CAR- Vγ9Vδ2 T cells resulted in a significant reduction of tumor burden in the femur region, as well as the overall tumor burden. In association with the decrease in tumor burden, the survival of the MM cell-inoculated mice was markedly prolonged. Considering the potential of Vγ9Vδ2 T cells to be used as off-the-shelf products, the modification of these cells with a BCMA-specific CAR could be an attractive option for cancer immunotherapy against bone marrow cancer MM.

CXCR4 and anti-BCMA CAR co-modified natural killer cells suppress multiple myeloma progression in a xenograft mouse model

The highly restricted expression of B-cell maturation antigen (BCMA) on plasma cells makes it an ideal target for chimeric antigen receptor (CAR) immune cell therapy against multiple myeloma (MM), a bone marrow cancer. To improve the infiltration of ex vivo expanded human natural killer (NK) cells into the bone marrow, we electroporated these cells with mRNA encoding the chemokine receptor CXCR4. The CXCR4-modified NK cells displayed increased in vitro migration toward the bone marrow niche-expressing chemokine CXCL12/SDF-1α and augmented infiltration into the bone marrow compartments in mice. We further modified the CXCR4-NK cells by electroporation of mRNA encoding a CAR targeting BCMA. After the intravenous injection of the double-modified NK cells into a xenograft mouse model of MM, we observed significantly reduced tumor burden in the femur region of the living mice and the extended survival of the tumor-bearing mice. Collectively, this study provides the experimental evidence that the co-expression of CXCR4 and anti-BCMA CAR on NK cells is a possible effective way to control MM progression.

Novel insights in CAR-NK cells beyond CAR-T cell technology; promising advantages

CAR-T (chimeric antigen receptor T cell) technology, which has recently showed successful results in the treatment of hematological tumors, has been the focus of attention as one of the most potent approaches in tumor immunotherapy. However, side effects and limitations of this application, such as the risk of graft versus host disease (GvHD), make it challenging to be as accessible as other treatments. Natural killer cells (NK) could be transplanted without alloreactivity, making them as an off-the-shelf product. CAR-NK (chimeric antigen receptor NK cell) therapy can circumvent some serious limitations of CAR-T cell therapy. Application of CAR-NK cells have some considerable advantages over CAR-T cells. These include lack of cytokine release syndrome (CRS), neurotoxicity, and GvHD when using allogenic CAR-T cell. These features lessen the risk of tumor antigen loss and disease relapse. Moreover, NK cells which were derived from different sources, can make the CAR therapy more feasible. In this narrative review, we outlined the key features of CAR-NK cells as an alternative to CAR-T cell therapy in cancer immunotherapy and highlighted the main advantages.

The Current Landscape of NKT Cell Immunotherapy and the Hills Ahead

Simple Summary

Natural killer T (NKT) cells are a subset of lipid-reactive T cells that enhance anti-tumor immunity. While preclinical studies have shown NKT cell immunotherapy to be safe and effective, clinical studies lack predictable therapeutic efficacy and no approved treatments exist. In this review, we outline the current strategies, challenges, and outlook for NKT cell immunotherapy.

Abstract

NKT cells are a specialized subset of lipid-reactive T lymphocytes that play direct and indirect roles in immunosurveillance and anti-tumor immunity. Preclinical studies have shown that NKT cell activation via delivery of exogenous glycolipids elicits a significant anti-tumor immune response. Furthermore, infiltration of NKT cells is associated with a good prognosis in several cancers. In this review, we aim to summarize the role of NKT cells in cancer as well as the current strategies and status of NKT cell immunotherapy. This review also examines challenges and future directions for improving the therapy.

Manufacturing NKG2D CAR-T cells with piggyBac transposon vectors and K562 artificial antigen-presenting cells

Non-viral platforms can be applied rapidly and cost-effectively for chimeric antigen receptor (CAR)-T cell manufacturing. In the present paper, we describe in detail a clinically relevant manufacturing process for NKG2D CAR-T cells through electroporation of CAR-encoding piggyBac transposon plasmids and in vitro expansion with K562 artificial antigen-presenting cells. With an optimized protocol, we generated the final cell therapy products with 89.2% ± 10.2% NKG2D CAR-positive cells and achieved the corresponding antigen-dependent expansion between 50,000 and 60,000 folds within 4 weeks. To facilitate repeated CAR-T cell infusions, we evaluated the practicality of cryopreservation followed by post-thaw expansion and an extended manufacturing process for up to 9 rounds of weekly K562 cell stimulation. We found that neither compromised the in vitro anti-tumor activity of NKG2D CAR-T cells. Interestingly, the expression of T cell exhaustion markers TIGIT, TIM3, and LAG3 was reduced with extended manufacturing. To enhance the safety profile of the NKG2D CAR-T cells, we incorporated a full-length CD20 transgene in tandem with the CAR construct and demonstrated that autologous NK cells could mediate efficient antibody-dependent cell-mediated cytotoxicity to remove these CAR-T cells. Collectively, our study illustrates a protocol that generates large numbers of efficacious NKG2D CAR-T cells suitable for multiple rounds of infusions.

State-of-Art of Cellular Therapy for Acute Leukemia

With recent clinical breakthroughs, immunotherapy has become the fourth pillar of cancer treatment. Particularly, immune cell-based therapies have been envisioned as a promising treatment option with curative potential for leukemia patients. Hence, an increasing number of preclinical and clinical studies focus on various approaches of immune cell-based therapy for treatment of acute leukemia (AL). However, the use of different immune cell lineages and subsets against different types of leukemia and patient disease statuses challenge the interpretation of the clinical applicability and outcome of immune cell-based therapies. This review aims to provide an overview on recent approaches using various immune cell-based therapies against acute B-, T-, and myeloid leukemias. Further, the apparent limitations observed and potential approaches to overcome these limitations are discussed.

Cellular Immunotherapy Targeting Cancer Stem Cells: Preclinical Evidence and Clinical Perspective

The term “cancer stem cells” (CSCs) commonly refers to a subset of tumor cells endowed with stemness features, potentially involved in chemo-resistance and disease relapses. CSCs may present peculiar immunogenic features influencing their homeostasis within the tumor microenvironment. The susceptibility of CSCs to recognition and targeting by the immune system is a relevant issue and matter of investigation, especially considering the multiple emerging immunotherapy strategies. Adoptive cellular immunotherapies, especially those strategies encompassing the genetic redirection with chimeric antigen receptors (CAR), hold relevant promise in several tumor settings and might in theory provide opportunities for selective elimination of CSC subsets. Initial dedicated preclinical studies are supporting the potential targeting of CSCs by cellular immunotherapies, indirect evidence from clinical studies may be derived and new studies are ongoing. Here we review the main issues related to the putative immunogenicity of CSCs, focusing on and highlighting the existing evidence and opportunities for cellular immunotherapy approaches with T and non-T antitumor lymphocytes.

Innate and Innate-Like Cells: The Future of Chimeric Antigen Receptor (CAR) Cell Therapy

Conventional αβ CAR-T cell-based approaches have revolutionized the field of cancer immunotherapy, but hurdles remain, especially for solid tumors. Novel strategies in conjunction with alternative cell types are therefore required for effective CAR-based therapies. In this respect, innate and innate-like cells with unique immune properties, such as natural killer (NK) cells, NKT cells, γδ T cells, and macrophages, are promising alternatives to αβ CAR-T adoptive therapy. We review the applicability of these cells in the context of CAR therapy, focusing on therapies under development, the advantages of these approaches relative to conventional CAR-T cells, and their potential in allogeneic therapies. We also discuss the inherent limitations of these cell types and approaches, and outline numerous strategies to overcome the associated obstacles.

T Cells Expressing NKG2D CAR with a DAP12 Signaling Domain Stimulate Lower Cytokine Production While Effective in Tumor Eradication

Cytokine-related toxicity associated with the use of highly active chimeric antigen receptor T cells (CAR-T cells) is a significant clinical problem. By fusing the natural killer group 2D (NKG2D) ectodomain to 4-1BB and the DAP12 cytoplasmic domain containing only one immunoreceptor tyrosine-based activation motif, we have developed a 2nd-generation (2nd-Gen) NKG2D CAR for stable expression in human T cells. When compared to T cells modified with NKG2D CAR containing the commonly used CD3ζ activation domain, T cells expressing the NKG2D-DAP12 CAR stimulated lower level release of interferon gamma (IFN-γ), tumor necrosis factor alpha (TNF-α), and interleukin (IL)-2 during tumor cell lysis and their proliferative activity was lower upon repeated antigen stimulation, although no difference between the two CARs was observed in mediating in vitro tumor cell lysis. In tumor-bearing NSG mice, both types of CAR-T cells displayed similar anti-tumor activity, being able to completely eradicate established solid tumor xenografts. However, treatment with the NKG2D-CD3ζ CAR-T cells led to the death of most mice from xenogeneic graft versus host disease starting 30 days post-CAR-T cell injection, which was associated with a higher level of cytokine release, whereas all the mice treated with the NKG2D-DAP12 CAR-T cells survived well. Thus, the incorporation of the DAP12 activation domain in a CAR design may possibly provide a potential clinical advantage in mitigating the risk of cytokine release syndrome (CRS).

Experimental treatment of colorectal cancer in mice with human T cells electroporated with NKG2D RNA CAR

Aim: Peritoneal metastasis is often present in end-stage neoplastic diseases, including recurrent colorectal cancer and is associated with decreased overall survival. Novel methods are needed. Materials & methods: We constructed first-, second- and third-generation chimeric antigen receptors (CARs) specific for NKG2D ligands and modified human T cells with mRNA electroporation. Results: NKG2D CAR expression was detectable for at least 6 days postelectroporation and mediated efficient cytotoxicity against NKG2DL+ tumor cells, but not NKG2DL-cells. Multiple infusions of the first-generation CAR-T cells into immunodeficient mice bearing established peritoneal colorectal xenografts led to significantly reduced tumor burden. Conclusion: mRNA CAR is an economical way to test new CARs and potentiates controlling on-target/off-tumor toxicity and cytokine storms. The use of NKG2D RNA CARs to treat colorectal peritoneal metastasis warrants further investigation.

Chronic Viral Liver Diseases: Approaching the Liver Using T Cell Receptor-Mediated Gene Technologies

Chronic infection with viral hepatitis is a major risk factor for liver injury and hepatocellular carcinoma (HCC). One major contributing factor to the chronicity is the dysfunction of virus-specific T cell immunity. T cells engineered to express virus-specific T cell receptors (TCRs) may be a therapeutic option to improve host antiviral responses and have demonstrated clinical success against virus-associated tumours. This review aims to give an overview of TCRs identified from viral hepatitis research and discuss how translational lessons learned from cancer immunotherapy can be applied to the field. TCR isolation pipelines, liver homing signals, cell type options, as well as safety considerations will be discussed herein.

T cell optimization for graft-versus-leukemia responses

Protection from relapse after allogeneic hematopoietic cell transplantation (HCT) is partly due to donor T cell-mediated graft-versus-leukemia (GVL) immune responses. Relapse remains common in HCT recipients, but strategies to augment GVL could significantly improve outcomes after HCT. Donor T cells with αβ T cell receptors (TCRs) mediate GVL through recognition of minor histocompatibility antigens and alloantigens in HLA-matched and -mismatched HCT, respectively. αβ T cells specific for other leukemia-associated antigens, including nonpolymorphic antigens and neoantigens, may also deliver an antileukemic effect. γδ T cells may contribute to GVL, although their biology and specificity are less well understood. Vaccination or adoptive transfer of donor-derived T cells with natural or transgenic receptors are strategies with potential to selectively enhance αβ and γδ T cell GVL effects.

Electroporation of NKG2D RNA CAR Improves Vγ9Vδ2 T Cell Responses against Human Solid Tumor Xenografts

Vγ9Vδ2 T cell-based anticancer immunotherapy has shown some promise in early-phase clinical trials but there is still large room for improvement. Using the extracellular domain of the human NKG2D, a stimulatory receptor expressed by Vγ9Vδ2 T cells, we constructed NKG2D ligand-specific chimeric antigen receptors (CARs). We adopted a non-viral CAR approach via mRNA electroporation to modify Vγ9Vδ2 T cells and demonstrated that, upon interaction with the NKG2D ligand-positive cancer cells, the CARs substantially enhanced the cytotoxic activity of the modified cells toward multiple cultured solid tumor cell lines, including those resistant to Zometa treatment. Repeated doses of the CAR-expressing cells resulted in tumor regression in mice with established tumors, extending median survival time by up to 132% as compared to the PBS control group. The findings suggest clinical potential for RNA CAR-modified Vγ9Vδ2 T cells to treat a wide variety of NKG2D ligand-expressing cancers.

CXCR1 Expression to Improve Anti-Cancer Efficacy of Intravenously Injected CAR-NK Cells in Mice with Peritoneal Xenografts

One reason underlying the failure of current chimeric antigen receptor (CAR) immune therapy to treat solid tumors adequately is insufficient tumor infiltration of CAR immune cells. To address the issue, we electroporated natural killer (NK) cells with two mRNA constructs encoding the chemokine receptor CXCR1 and a CAR targeting tumor-associated NKG2D ligands. The CXCR1-modified NK cells displayed increased migration toward tumor supernatants in vitro and augmented infiltration into human tumors in vivo in subcutaneous and intraperitoneal xenograft models. Most importantly, the cytotoxicity of the CAR-NK cells was not affected by CXCR1 transgene expression, and the enhanced tumor trafficking following intravenous injection resulted in significantly increased antitumor responses in mice carrying established peritoneal ovarian cancer xenografts. Collectively, our findings suggest that the coexpression of CXCR1 and a CAR may provide a novel strategy to enhance therapeutic efficacy of NK cells against solid cancers.

Beta-2 microglobulin knockout K562 cell-based artificial antigen presenting cells for ex vivo expansion of T lymphocytes

Aim: The human K562 leukemia cell line as a scaffold of artificial antigen presenting cells (aAPCs) for ex vivo lymphocyte expansion does not usually express major histocompatibility complex (MHC) molecules. However, when stimulated by supernatants from human T lymphocyte cultures, K562 cells upregulate β-2 microglobulin (B2M) and MHC class I expression, which would induce allo-specific T cells. Methods: We disrupted the B2M locus in K562 cells by CRISPR/Cas9 and achieved MHC class I-negative K562 cells. Results: We further generated K562-based MHC class I-negative aAPC line by zinc-finger nuclease mediated insertion of costimulatory molecules into the AAVS1 locus. This aAPC line could attenuate allogeneic immune responses but support robust antigen-independent and CD19 antigen-specific chimeric antigen receptor-T cell expansion in vitro. Conclusion: B2M-knockout K562 cells provide a new scaffold for aAPC construction and broader application in adoptive immunotherapies.

CAR-Based Strategies beyond T Lymphocytes: Integrative Opportunities for Cancer Adoptive Immunotherapy

Chimeric antigen receptor (CAR)-engineered T lymphocytes (CAR Ts) produced impressive clinical results against selected hematological malignancies, but the extension of CAR T cell therapy to the challenging field of solid tumors has not, so far, replicated similar clinical outcomes. Many efforts are currently dedicated to improve the efficacy and safety of CAR-based adoptive immunotherapies, including application against solid tumors. A promising approach is CAR engineering of immune effectors different from αβT lymphocytes. Herein we reviewed biological features, therapeutic potential, and safety of alternative effectors to conventional CAR T cells: γδT, natural killer (NK), NKT, or cytokine-induced killer (CIK) cells. The intrinsic CAR-independent antitumor activities, safety profile, and ex vivo expansibility of these alternative immune effectors may favorably contribute to the clinical development of CAR strategies. The proper biological features of innate immune response effectors may represent an added value in tumor settings with heterogeneous CAR target expression, limiting the risk of tumor clonal escape. All these properties bring out CAR engineering of alternative immune effectors as a promising integrative option to be explored in future clinical studies.

Single-cell RNA sequencing unveils the shared and the distinct cytotoxic hallmarks of human TCRVδ1 and TCRVδ2 γδ T lymphocytes

γδ T lymphocytes represent ∼1% of human peripheral blood mononuclear cells and even more cells in most tissues of vertebrates. Although they have important anticancer functions, most current single-cell RNA sequencing (scRNA-seq) studies do not identify γδ T lymphocytes because their transcriptomes at the single-cell level are unknown. Here we show that high-resolution clustering of large scRNA-seq datasets and a combination of gene signatures allow the specific detection of human γδ T lymphocytes and identification of their T cell receptor (TCR)Vδ1 and TCRVδ2 subsets in large datasets from complex cell mixtures. In t-distributed stochastic neighbor embedding plots from blood and tumor samples, the few γδ T lymphocytes appear collectively embedded between cytotoxic CD8 T and NK cells. Their TCRVδ1 and TCRVδ2 subsets form close yet distinct subclusters, respectively neighboring NK and CD8 T cells because of expression of shared and distinct cytotoxic maturation genes. Similar pseudotime maturation trajectories of TCRVδ1 and TCRVδ2 γδ T lymphocytes were discovered, unveiling in both subsets an unattended pool of terminally differentiated effector memory cells with preserved proliferative capacity, a finding confirmed by in vitro proliferation assays. Overall, the single-cell transcriptomes of thousands of individual γδ T lymphocytes from different CMV+ and CMV- donors reflect cytotoxic maturation stages driven by the immunological history of donors. This landmark study establishes the rationale for identification, subtyping, and deep characterization of human γδ T lymphocytes in further scRNA-seq studies of complex tissues in physiological and disease conditions.

The making and function of CAR cells

Genetically engineered T cells expressing chimeric antigen receptors (CAR) present a new treatment option for patients with cancer. Recent clinical trials of B cell leukemia have demonstrated a response rate of up to 90%. However, CAR cell therapy is frequently accompanied by severe side effects such as cytokine release syndrome and the development of target cell resistance. Consequently, further optimization of CARs to obtain greater long-term efficacy and increased safety is urgently needed. Here we high-light the various efforts of adjusting the intracellular signaling domains of CARs to these major requirements to eventually obtain high-level target cell cytotoxicity paralleled by the establishment of longevity of the CAR expressing cell types to guarantee for extended tumor surveillance over prolonged periods of time. We are convinced that it will be crucial to identify the molecular pathways and signaling requirements utilized by such ‘efficient CARs’ in order to provide a rational basis for their further hypothesis-based improvement. Furthermore, we here discuss timely attempts of how to: i) control ‘on-tumor off-target’ effects; ii) introduce Signal 3 (cytokine responsiveness of CAR cells) as an important building-block into the CAR concept; iii) most efficiently eliminate CAR cells once full remission has been obtained. We also argue that universal systems for the variable and pharmacokinetically-controlled attachment of extracellular ligand recognition domains of choice along with the establishment of ‘off-the-shelf’ cell preparations with suitability for all patients in need of a highly-potent cellular therapy may become future mainstays of CAR cell therapy. Such therapies would have the attraction to work independent of the patients’ histo-compatibility make-up and the availability of functionally intact patient’s cells. Finally, we summarize the evidence that CAR cells may obtain a prominent place in the treatment of non-malignant and auto-reactive T and B lymphocyte expansions in the near future, e.g., for the alleviation of autoimmune diseases and allergies. After the introduction of red blood cell transfusions, which were made possible by the landmark discoveries of the ABO blood groups by Karl Landsteiner, and the establishment of bone marrow transplantation by E. Donnall Thomas to exchange the entire hematopoietic system of a patient suffering from leukemia, the introduction of patient-tailored cytotoxic cellular populations to eradicate malignant cell populations in vivo pioneered by Carl H. June, represents the third major and broadly applicable milestone in the development of human cellular therapies within the rapidly developing field of applied biomedical research of the last one hundred years.

High-affinity T cell receptors redirect cytokine-activated T cells (CAT) to kill cancer cells

Cytokine-activated T cells (CATs) can be easily expanded and are widely applied to cancer immunotherapy. However, the good efficacy of CATs is rarely reported in clinical applications because CATs have no or very low antigen specificity. The low-efficacy problem can be resolved using T cell antigen receptor-engineered CAT (TCR-CAT). Herein, we demonstrate that NY-ESO-1_157-165 HLA-A*02:01-specific high-affinity TCR (HAT)-transduced CATs can specifically kill cancer cells with good efficacy. With low micromolar range dissociation equilibrium constants, HAT-transduced CATs showed good specificity with no off-target killing. Furthermore, the high-affinity TCR-CATs delivered significantly better activation and cytotoxicity than the equivalent TCR-engineered T cells (TCR-Ts) in terms of interferon-γ and granzyme B production and in vitro cancer cell killing ability. TCR-CAT may be a very good alternative to the expensive TCR-T, which is considered an effective personalized cyto-immunotherapy.

Vγ9Vδ2 T Cells as Strategic Weapons to Improve the Potency of Immune Checkpoint Blockade and Immune Interventions in Human Myeloma

The advent of immune checkpoint (ICP) blockade has introduced an unprecedented paradigm shift in the treatment of cancer. Though very promising, there is still a substantial proportion of patients who do not respond or develop resistance to ICP blockade. In vitro and in vivo models are eagerly needed to identify mechanisms to maximize the immune potency of ICP blockade and overcome primary and acquired resistance to ICP blockade. Vγ9Vδ2 T cells isolated from the bone marrow (BM) from multiple myeloma (MM) are excellent tools to investigate the mechanisms of resistance to PD-1 blockade and to decipher the network of mutual interactions between PD-1 and the immune suppressive tumor microenvironment (TME). Vγ9Vδ2 T cells can easily be interrogated to dissect the progressive immune competence impairment generated in the TME by the long-lasting exposure to myeloma cellss. BM MM Vγ9Vδ2 T cells are PD-1⁺ and anergic to phosphoantigen (pAg) stimulation; notably, single agent PD-1 blockade is insufficient to fully recover their anti-tumor activity in vitro indicating that additional players are involved in the anergy of Vγ9Vδ2 T cells. In this mini-review we will discuss the value of Vγ9Vδ2 T cells as investigational tools to improve the potency of ICP blockade and immune interventions in MM.

Co-culture of dendritic cells and cytokine-induced killer cells effectively suppresses liver cancer stem cell growth by inhibiting pathways in the immune system

BACKGROUND

Application of dendritic cells (DC) for cancer immunotherapy involves tumor-associated immunogenic antigens for effective therapeutic strategies. The present study investigated whether DC co-cultured with autologous cytokine-induced killer cells (CIK) could induce a more specific immune response against liver cancer stem cells (LCSC) generated from human hepatocellular carcinoma (HCC) cells in vitro and in vivo.

METHODS

Human DC and CIK were generated from peripheral blood mononuclear cells (PBMCs) taken from consenting liver cancer patients. Flow cytometry was used to determine the phenotypes of DC and CIK, and cell proliferation. The tumor growth and anti-tumor activity of these cells were further evaluated using a nude mouse tumor model.

RESULTS

We demonstrated that DC and CIK significantly enhanced the apoptosis ratio, depending on DC-CIK cell numbers, by increasing caspase-3 protein expression and reducing proliferating cell nuclear antigen (PCNA) protein expression against LCSC. The in vivo data indicated that DC-CIK exhibited significant LCSC cell-induced tumor growth inhibition in nude mice, which was most significant with LCSC antigen loaded DCs.

CONCLUSIONS

The results showed, that DC-CIK cells could inhibit HCC and LCSC growths in vitro and in vivo and the most successful DC triggering of cell cytotoxic activity could be achieved by their LCSC antigen loading.

NKT cells - New players in CAR cell immunotherapy?

Low levels of peripheral blood natural killer T (NKT) cells in cancer patients and a favorable outcome associated with a high number of tumor-infiltrating NKT cells demonstrated in several studies indicated the important role of these immune cells in the antitumor response. With effective antitumor immunity via direct tumor lysis, cytokine modulation of effector cells and regulation of immunosuppressive cells, type I NKT cells display interesting features/properties for the rapidly developing chimeric antigen receptor (CAR) technology. Due to their restriction to the monomorphic HLA-like molecule CD1d, but not to the polymorphic human leukocyte antigen (HLA), NKT CAR cells show potential for enabling autologous and allogeneic/off-the-shelf cancer immunotherapy. Promising results were obtained in preclinical NKT CAR cell studies, but clinical trials have not yet been conducted. In this review, we summarize the biological features of NKT cells, their role in antitumor immunity and recent advances in the development of NKT CAR cells.

IL-21 Selectively Protects CD62L+ NKT Cells and Enhances Their Effector Functions for Adoptive Immunotherapy

T cells expressing CD19-specific chimeric Ag receptors (CARs) produce high remission rates in B cell lymphoma, but frequent disease recurrence and challenges in generating sufficient numbers of autologous CAR T cells necessitate the development of alternative therapeutic effectors. Vα24-invariant NKTs have intrinsic antitumor properties and are not alloreactive, allowing for off-the-shelf use of CAR-NKTs from healthy donors. We recently reported that CD62L⁺ NKTs persist longer and have more potent antilymphoma activity than CD62L^- cells. However, the conditions governing preservation of CD62L⁺ cells during NKT cell expansion remain largely unknown. In this study, we demonstrate that IL-21 preserves this crucial central memory-like NKT subset and enhances its antitumor effector functionality. We found that following antigenic stimulation with α-galactosylceramide, CD62L⁺ NKTs both expressed IL-21R and secreted IL-21, each at significantly higher levels than CD62L^- cells. Although IL-21 alone failed to expand stimulated NKTs, combined IL-2/IL-21 treatment produced more NKTs and increased the frequency of CD62L⁺ cells versus IL-2 alone. Gene expression analysis comparing CD62L⁺ and CD62L^- cells treated with IL-2 alone or IL-2/IL-21 revealed that the latter condition downregulated the proapoptotic protein BIM selectively in CD62L⁺ NKTs, protecting them from activation-induced cell death. Moreover, IL-2/IL-21-expanded NKTs upregulated granzyme B expression and produced more T_H1 cytokines, leading to enhanced in vitro cytotoxicity of nontransduced and anti-CD19-CAR-transduced NKTs against CD1d⁺ and CD19⁺ lymphoma cells, respectively. Further, IL-2/IL-21-expanded CAR-NKTs dramatically increased the survival of lymphoma-bearing NSG mice compared with IL-2-expanded CAR-NKTs. These findings have immediate translational implications for the development of NKT cell-based immunotherapies targeting lymphoma and other malignancies.

Checkpoint Blockade Rescues the Repressive Effect of Histone Deacetylases Inhibitors on γδ T Cell Function

Histone deacetylases (HDAC) are one of the key epigenetic modifiers that control chromatin accessibility and gene expression. Their role in tumorigenesis is well established and HDAC inhibitors have emerged as an effective treatment modality. HDAC inhibitors have been investigated for their specific antitumor activities and also clinically evaluated in treatment of various malignancies. In the present study, we have investigated the effect of HDAC inhibitors on the effector functions of human γδ T cells. HDAC inhibitors inhibit the antigen-specific proliferative response of γδ T cells and cell cycle progression. In antigen-activated γδ T cells, the expression of transcription factors (Eomes and Tbet) and effector molecules (perforin and granzyme B) were decreased upon treatment with HDAC inhibitors. Treatment with HDAC inhibitors attenuated the antitumor cytotoxic potential of γδ T cells, which correlated with the enhanced expression of immune checkpoints programmed death-1 (PD-1) and programmed death ligand-1 in γδ T cells. Interestingly, PD-1 blockade improves the antitumor effector functions of HDAC inhibitor-treated γδ T cells, which is reflected in the increased expression of Granzyme B and Lamp-1. This study provides a rationale for designing HDAC inhibitor and immune check point blockade as a combinatorial treatment modality for cancer.

Epitopes of MUC1 Tandem Repeats in Cancer as Revealed by Antibody Crystallography: Toward Glycopeptide Signature-Guided Therapy

Abnormally O-glycosylated MUC1 tandem repeat glycopeptide epitopes expressed by multiple types of cancer have long been attractive targets for therapy in the race against genetic mutations of tumor cells. Glycopeptide signature-guided therapy might be a more promising avenue than mutation signature-guided therapy. Three O-glycosylated peptide motifs, PDTR, GSTA, and GVTS, exist in a tandem repeat HGVTSAPDTRPAPGSTAPPA, containing five O-glycosylation sites. The exact peptide and sugar residues involved in antibody binding are poorly defined. Co-crystal structures of glycopeptides and respective monoclonal antibodies are very few. Here we review 3 groups of monoclonal antibodies: antibodies which only bind to peptide portion, antibodies which only bind to sugar portion, and antibodies which bind to both peptide and sugar portions. The antigenicity of peptide and sugar portions of glyco-MUC1 tandem repeat were analyzed according to available biochemical and structural data, especially the GSTA and GVTS motifs independent from the most studied PDTR. Tn is focused as a peptide-modifying residue in vaccine design, to induce glycopeptide-binding antibodies with cross reactivity to Tn-related tumor glycans, but not glycans of healthy cells. The unique requirement for the designs of antibody in antibody-drug conjugate, bi-specific antibodies, and chimeric antigen receptors are also discussed.

Large-scale expansion of Vγ9Vδ2 T cells with engineered K562 feeder cells in G-Rex vessels and their use as chimeric antigen receptor-modified effector cells

Vγ9Vδ2 T cells are a minor subset of lymphocytes in the peripheral blood that has been extensively investigated for their tolerability, safety and anticancer efficacy. A hindrance to the broad application of these cells for adoptive cellular immunotherapy has been attaining clinically appropriate numbers of Vγ9Vδ2 T cells. Furthermore, Vγ9Vδ2 T cells exist at low frequencies among cancer patients. We, therefore, sought to conceive an economical method that allows for a quick and robust large-scale expansion of Vγ9Vδ2 T cells. A two-step protocol was developed, in which peripheral blood mononuclear cells (PBMCs) from healthy donors or cancer patients were activated with Zometa and interleukin (IL)-2, followed by co-culturing with gamma-irradiated, CD64-, CD86- and CD137L-expressing K562 artificial antigen-presenting cells (aAPCs) in the presence of the anti-CD3 antibody OKT3. We optimized the co-culture ratio of K562 aAPCs to immune cells, and migrated this method to a G-Rex cell growth platform to derive clinically relevant cell numbers in a Good Manufacturing Practice (GMP)-compliant manner. We further include a depletion step to selectively remove αβ T lymphocytes. The method exhibited high expansion folds and a specific enrichment of Vγ9Vδ2 T cells. Expanded Vγ9Vδ2 T cells displayed an effector memory phenotype with a concomitant down-regulated expression of inhibitory immune checkpoint receptors. Finally, we ascertained the cytotoxic activity of these expanded cells by using nonmodified and chimeric antigen receptor (CAR)-engrafted Vγ9Vδ2 T cells against a panel of solid tumor cells. Overall, we report an efficient approach to generate highly functional Vγ9Vδ2 T cells in massive numbers suitable for clinical application in an allogeneic setting.

The potential role of γδ T cells after allogeneic HCT for leukemia

Allogeneic hematopoetic stem cell transplantation (HCT) offers an option for patients with hematologic malignancies, in whom conventional standard therapies failed or are not effective enough to cure the disease. Successful HCT can restore functional hematopoiesis and immune function, and the new donor-derived immune system can exert a graft-versus-leukemia (GVL) effect. However, allogenic HCT can also be associated with serious risks for transplantation-related morbidities or mortalities such as graft-versus-host disease (GVHD) or life-threatening infectious complications. GVHD is caused by alloreactive T lymphocytes, which express the αβ T-cell receptor, whereas lymphocytes expressing the γδ T-cell receptor are not alloreactive and do not induce GVHD but can exhibit potent antileukemia and anti-infectious activities. Therefore, γδ T cells are becoming increasingly interesting in allogeneic HCT, and clinical strategies to exploit the full function of these lymphocytes have been and are being developed. Such strategies comprise the in vivo activation of γδ T cells or subsets after HCT by certain drugs or antibodies or the ex vivo expansion and manipulation of either patient-derived or donor-derived γδ T cells and their subsets and the adoptive transfer of the ex vivo-activated lymphocytes. On the basis of the absence of dysregulated alloreactivity, such approaches could induce potent GVL effects in the absence of GVHD. The introduction of large-scale clinical methods to enrich, isolate, expand, and manipulate γδ T cells will facilitate future clinical studies that aim to exploit the full function of these beneficial nonalloreactive lymphocytes.

Gamma-delta (γδ) T cells: friend or foe in cancer development?

BACKGROUND

γδ T cells are a distinct subgroup of T cells containing T cell receptors (TCRs) γ and TCR δ chains with diverse structural and functional heterogeneity. As a bridge between the innate and adaptive immune systems, γδ T cells participate in various immune responses during cancer progression. Because of their direct/indirect antitumor cytotoxicity and strong cytokine production ability, the use of γδ T cells in cancer immunotherapy has received a lot of attention over the past decade.

MAIN TEXT

Despite the promising potential of γδ T cells, the efficacy of γδ T cell immunotherapy is limited, with an average response ratio of only 21%. In addition, research over the past 2 years has shown that γδ T cells could also promote cancer progression by inhibiting antitumor responses, and enhancing cancer angiogenesis. As a result, γδ T cells have a dual effect and can therefore be considered as being both "friends" and "foes" of cancer. In order to solve the sub-optimal efficiency problem of γδ T cell immunotherapy, we review recent observations regarding the antitumor and protumor activities of major structural and functional subsets of human γδ T cells, describing how these subsets are activated and polarized, and how these events relate to subsequent effects in cancer immunity. A mixture of both antitumor or protumor γδ T cells used in adoptive immunotherapy, coupled with the fact that γδ T cells can be polarized from antitumor cells to protumor cells appear to be the likely reasons for the mild efficacy seen with γδ T cells.

CONCLUSION

The future holds the promise of depleting the specific protumor γδ T cell subgroup before therapy, choosing multi-immunocyte adoptive therapy, modifying the cytokine balance in the cancer microenvironment, and using a combination of γδ T cells adoptive immunotherapy with immune checkpoint inhibitors.

The progress and current status of immunotherapy in acute myeloid leukemia

Recently, there has been remarkable progress in basic and preclinical studies of acute myeloid leukemia (AML). The improved outcomes of AML can largely be attributed to advances in supportive care and hematopoietic cell transplantation as opposed to conventional chemotherapy. However, as the 5-year survival rate remains low due to a high incidence of relapse, novel and effective treatments are urgently needed. Increasing attention is focusing on identifying suitable immunotherapeutic strategies for AML. Here, we describe the immunological features, mechanisms of immune escape, and recent progress in immunotherapy for AML. Problems encountered in the clinic will also be discussed. Although current outcomes may be limited, ongoing preclinical or clinical efforts are aimed at improving immunotherapy modalities and designing novel therapies, such as vaccines, monoclonal antibody therapy, chimeric antibody receptor-engineered T cells (CAR-T), TCR-engineered T cells (TCR-T), and checkpoint inhibitors, which may provide promising and effective therapies with higher specificity and efficacy for AML.

Driving better and safer HER2-specific CARs for cancer therapy

Given the clinical efficacy of chimeric antigen receptor (CAR)-based therapy in hematological malignancies, CAR T-cell therapy for a number of solid tumors has been actively investigated. Human epidermal growth factor receptor 2 (HER2) is a well-established therapeutic target in breast, as well as other types of cancer. However, HER2 CAR T cells pose a risk of lethal toxicity including cytokine release syndrome from “on-target, off-tumor” recognition of HER2. In this review, we summarize the development of conventional HER2 CAR technology, the alternative selection of CAR hosts, the novel HER2 CAR designs, clinical studies and toxicity. Furthermore, we also discuss the main strategies for improving the safety of HER2 CAR-based cancer therapies.

Advances in Cancer Immunotherapy in Solid Tumors

Immunotherapy is heralded as one of the most important advances in oncology. Until recently, only limited immunotherapeutic options were available in selected immunogenic cancers like melanoma and renal cell carcinomas. Nowadays, there is an improved understanding that anti-tumor immunity is controlled by a delicate balance in the tumor microenvironment between immune stimulatory and immune inhibitory pathways. Either by blocking the inhibitory pathways or stimulating the activating pathways that regulate cytotoxic lymphocytes, anti-tumor immunity can be enhanced leading to durable anti-tumor responses. Drugs which block the immune regulatory checkpoints namely the PD-1/PDL1 and CTLA 4 pathway have shown tremendous promise in a wide spectrum of solid and hematological malignancies, significantly improving overall survival in newly diagnosed and heavily pretreated patients alike. Hence there is renewed enthusiasm in the field of immune oncology with current research focused on augmenting responses to checkpoint inhibitors by combination therapy as well as studies looking at other immune modulators and adoptive T cell therapy. In this article, we highlight the key clinical advances and concepts in immunotherapy with particular emphasis on checkpoint inhibition as well as the future direction in this field.