Activation-induced cell death in CAR-T cell therapy

Development of bioassay platforms for biopharmaceuticals using Jurkat-CAR cells by AICD

The assessment of bioactivity for therapeutic antibody release assay poses challenges, particularly when targeting immune checkpoints. An in vitro bioassay platform was developed using the chimeric antigen receptor on Jurkat cells (Jurkat-CAR) to analyze antibodies targeting immune checkpoints, such as CD47/SIRPα, VEGF/VEGFR1, PD-1/PD-L1, and CD70/CD27. For CD47/SIRPα, the platform involved a Jurkat-CAR cell line expressing the chimeric SIRPα receptor (CarSIRPα). CarSIRPα was created by sequentially fusing the SIRPα extracellular region with the CD8α hinge region, the transmembrane (TM) and intracellular (IC) domains of CD28, and the intracellular signaling domain of CD3ζ. The resulting Jurkat-CarSIRPα cells can undergo "activation-induced cell death (AICD)" upon incubation with purified or cellular CD47, as evidenced by the upregulation of CD69, IL-2, and IFN-γ. Similar results also appeared in Jurkat CarVEGFR1, Jurkat CarPD1 and Jurkat CARCD27 cells. These cells are perfectly utilized for the bioactivity analysis of therapeutic antibody. Our study indicates that the established in vitro assay platform based on Jurkat-CAR has been confirmed repeatedly and has shown robust reproducibility; thus, this platform can be used for screening or for release assays of given antibody drugs targeting immune checkpoints.

Synergistic effect of chimeric antigen receptor modified with Bcl-2 on enhanced solid tumour targeting

Engineered T cells expressing chimeric antigen receptors (CARs) have shown remarkable therapeutic effects on haematological malignancies. However, CART cells are less effective on solid tumours mainly due to their weak persistence, which might be caused by activation-induced cell death (AICD). To overcome this limitation, CART cell with the antigen, Epidermal growth factor receptor variant III (EGFRvIII), targeting was modified to carry the anti-apoptotic molecule B cell lymphoma 2 (Bcl-2), and the final construct was named as EGFRvIII·CART-Bcl2 cells. Compared with the EGFRvIII·CART cells, EGFRvIII·CART-Bcl2 cells revealed higher capacities of proliferation, anti-apoptosis and tumour cell killing in vitro. Moreover, EGFRvIII·CART-Bcl2 cells had a longer persistence rate and exerted better anti-tumour effects than EGFRvIII·CART cells in cervical carcinoma xenograft model. Taken together, our findings suggest that incorporating anti-apoptotic molecules into CART cells may enhance its therapeutic effects against solid tumours.

Identification of a clinically efficacious CAR T cell subset in diffuse large B cell lymphoma by dynamic multidimensional single-cell profiling

Chimeric antigen receptor (CAR) T cells used for the treatment of B cell malignancies can identify T cell subsets with superior clinical activity. Here, using infusion products of individuals with large B cell lymphoma, we integrated functional profiling using timelapse imaging microscopy in nanowell grids with subcellular profiling and single-cell RNA sequencing to identify a signature of multifunctional CD8+ T cells (CD8-fit T cells). CD8-fit T cells are capable of migration and serial killing and harbor balanced mitochondrial and lysosomal volumes. Using independent datasets, we validate that CD8-fit T cells (1) are present premanufacture and are associated with clinical responses in individuals treated with axicabtagene ciloleucel, (2) longitudinally persist in individuals after treatment with CAR T cells and (3) are tumor migrating cytolytic cells capable of intratumoral expansion in solid tumors. Our results demonstrate the power of multimodal integration of single-cell functional assessments for the discovery and application of CD8-fit T cells as a T cell subset with optimal fitness in cell therapy.

One-carbon metabolism shapes T cell immunity in cancer

One-carbon metabolism (1CM), comprising folate metabolism and methionine metabolism, serves as an important mechanism for cellular energy provision and the production of vital signaling molecules, including single-carbon moieties. Its regulation is instrumental in sustaining the proliferation of cancer cells and facilitating metastasis; in addition, recent research has shed light on its impact on the efficacy of T cell-mediated immunotherapy. In this review, we consolidate current insights into how 1CM affects T cell activation, differentiation, and functionality. Furthermore, we delve into the strategies for modulating 1CM in both T cells and tumor cells to enhance the efficacy of adoptively transferred T cells, overcome metabolic challenges in the tumor microenvironment (TME), and maximize the benefits of T cell-mediated immunotherapy.

Multimodal stimulation screens reveal unique and shared genes limiting T cell fitness

Genes limiting T cell antitumor activity may serve as therapeutic targets. It has not been systematically studied whether there are regulators that uniquely or broadly contribute to T cell fitness. We perform genome-scale CRISPR-Cas9 knockout screens in primary CD8 T cells to uncover genes negatively impacting fitness upon three modes of stimulation: (1) intense, triggering activation-induced cell death (AICD); (2) acute, triggering expansion; (3) chronic, causing dysfunction. Besides established regulators, we uncover genes controlling T cell fitness either specifically or commonly upon differential stimulation. Dap5 ablation, ranking highly in all three screens, increases translation while enhancing tumor killing. Loss of Icam1-mediated homotypic T cell clustering amplifies cell expansion and effector functions after both acute and intense stimulation. Lastly, Ctbp1 inactivation induces functional T cell persistence exclusively upon chronic stimulation. Our results functionally annotate fitness regulators based on their unique or shared contribution to traits limiting T cell antitumor activity.

Mutant KRAS-activated circATXN7 fosters tumor immunoescape by sensitizing tumor-specific T cells to activation-induced cell death

Mutant KRAS (KRASMUT) is often exploited by cancers to shape tumor immunity, but the underlying mechanisms are not fully understood. Here we report that tumor-specific cytotoxic T lymphocytes (CTLs) from KRASMUT cancers are sensitive to activation-induced cell death (AICD). circATXN7, an NF-κB-interacting circular RNA, governs T cell sensitivity to AICD by inactivating NF-κB. Mechanistically, histone lactylation derived from KRASMUT tumor cell-produced lactic acid directly activates transcription of circATXN7, which binds to NF-κB p65 subunit and masks the p65 nuclear localization signal motif, thereby sequestering it in the cytoplasm. Clinically, circATXN7 upregulation in tumor-specific CTLs correlates with adverse clinical outcomes and immunotherapeutic resistance. Genetic ablation of circAtxn7 in CD8+ T cells leads to mutant-selective tumor inhibition, while also increases anti-PD1 efficacy in multiple tumor models in female mice. Furthermore, targeting circATXN7 in adoptively transferred tumor-reactive CTLs improves their antitumor activities. These findings provide insight into how lymphocyte-expressed circRNAs contribute to T-cell fate decisions and anticancer immunotherapies.

Advanced Strategies of CAR-T Cell Therapy in Solid Tumors and Hematological Malignancies

Chimeric antigen receptor T-cells, known as CAR-T cells, represent a promising breakthrough in the realm of adoptive cell therapy. These T-cells are genetically engineered to carry chimeric antigen receptors that specifically target tumors. They have achieved notable success in the treatment of blood-related cancers, breathing new life into this field of medical research. However, numerous obstacles limit chimeric antigen receptors T-cell therapy's efficacy, such as it cannot survive in the body long. It is prone to fatigue and exhaustion, leading to difficult tumor elimination and repeated recurrence, affecting solid tumors and hematological malignancies. The challenges posed by solid tumors, especially in the context of the complex solid-tumor microenvironment, require specific strategies. This review outlines recent advancements in improving chimeric antigen receptors T-cell therapy by focusing on the chimeric antigen receptors protein, modifying T-cells, and optimizing the interaction between T-cells and other components within the tumor microenvironment. This article aims to provide an extensive summary of the latest discoveries regarding CAR-T cell therapy, encompassing its application across various types of human cancers. Moreover, it will delve into the obstacles that have emerged in recent times, offering insights into the challenges faced by this innovative approach. Finally, it highlights novel therapeutic options in treating hematological and solid malignancies with chimeric antigen receptors T-cell therapies.

Cell Therapy Approaches for Articular Cartilage Regeneration

Articular cartilage is a common cartilage type found in a multitude of joints throughout the human body. However, cartilage is limited in its regenerative capacity. A range of methods have been employed to aid adults under the age of 45 with cartilage defects, but other cartilage pathologies such as osteoarthritis are limited to non-steroidal anti-inflammatory drugs and total joint arthroplasty. Cell therapies and synthetic biology can be utilized to assist not only cartilage defects but have the potential as a therapeutic approach for osteoarthritis as well. In this review, we will cover current cell therapy approaches for cartilage defect regeneration with a focus on autologous chondrocyte implantation and matrix autologous chondrocyte implantation. We will then discuss the potential of stem cells for cartilage repair in osteoarthritis and the use of synthetic biology to genetically engineer cells to promote cartilage regeneration and potentially reverse osteoarthritis.

Emerging Therapeutic Targets and Drug Resistance Mechanisms in Immunotherapy of Hematological Malignancies

CAR-T cell therapy has revolutionized the treatment of hematological malignancies with high remission rates in the case of ALL and NHL. This therapy has some limitations such as long manufacturing periods, persistent restricted cell sources and high costs. Moreover, combination regimens increase the risk of immune-related adverse events, so the identification new therapeutic targets is important to minimize the risk of toxicities and to guide more effective approaches. Cancer cells employ several mechanisms to evade immunosurveillance, which causes resistance to immunotherapy; therefore, a very important therapeutic approach is to focus on the development of rational combinations of targeted therapies with non-overlapping toxicities. Recent progress in the development of new inhibitory clusters of differentiation (CDs), signaling pathway molecules, checkpoint inhibitors, and immunosuppressive cell subsets and factors in the tumor microenvironment (TME) has significantly improved anticancer responses. Novel strategies regarding combination immunotherapies with CAR-T cells are the most promising approach to cure cancer.

In vitro assays to evaluate CAR-T cell cytotoxicity

This chapter introduces four commonly used in vitro chimeric antigen receptor (CAR)-T cell cytotoxicity assays (lactate dehydrogenase release assay, 51Cr release assay, IncuCyte live cell killing assay, and xCELLigence real-time analysis) and provides a detailed protocol for xCELLigence real-time analysis. Focusing on in vitro assays, this chapter starts with explaining the mechanisms and discussing the utilization of each assay to quantify T-cell-induced cytotoxicity. Due to the high-throughput quantification and straightforward workflow of xCELLigence real-time analysis, a protocol entailing reagents and equipment, a 3-day step-by-step procedure, and instructions for data analysis are provided.

Targeting CXCL9/10/11-CXCR3 axis: an important component of tumor-promoting and antitumor immunity

Chemokines are chemotactic-competent molecules composed of a family of small cytokines, playing a key role in regulating tumor progression. The roles of chemokines in antitumor immune responses are of great interest. CXCL9, CXCL10, and CXCL11 are important members of chemokines. It has been widely investigated that these three chemokines can bind to their common receptor CXCR3 and regulate the differentiation, migration, and tumor infiltration of immune cells, directly or indirectly affecting tumor growth and metastasis. Here, we summarize the mechanism of how the CXCL9/10/11-CXCR3 axis affects the tumor microenvironment, and list the latest researches to find out how this axis predicts the prognosis of different cancers. In addition, immunotherapy improves the survival of tumor patients, but some patients show drug resistance. Studies have found that the regulation of CXCL9/10/11-CXCR3 on the tumor microenvironment is involved in the process of changing immunotherapy resistance. Here we also describe new approaches to restoring sensitivity to immune checkpoint inhibitors through the CXCL9/10/11-CXCR3 axis.

T lymphocytes expressing the switchable chimeric Fc receptor CD64 exhibit augmented persistence and antitumor activity

Chimeric antigen receptor (CAR) T cell therapy lacks persistent efficacy with "on-target, off-tumor" toxicities for treating solid tumors. Thus, an antibody-guided switchable CAR vector, the chimeric Fc receptor CD64 (CFR64), composed of a CD64 extracellular domain, is designed. T cells expressing CFR64 exert more robust cytotoxicity against cancer cells than CFR T cells with high-affinity CD16 variant (CD16v) or CD32A as their extracellular domains. CFR64 T cells also exhibit better long-term cytotoxicity and resistance to T cell exhaustion compared with conventional CAR T cells. With trastuzumab, the immunological synapse (IS) established by CFR64 is more stable with lower intensity induction of downstream signaling than anti-HER2 CAR T cells. Moreover, CFR64 T cells exhibit fused mitochondria in response to stimulation, while CARH2 T cells contain predominantly punctate mitochondria. These results show that CFR64 T cells may serve as a controllable engineered T cell therapy with prolonged persistence and long-term antitumor activity.

Development of a TGFβ-IL-2/15 Switch Receptor for Use in Adoptive Cell Therapy

Therapy employing T cells modified with chimeric antigen receptors (CARs) is effective in hematological malignancies but not yet in solid cancers. CAR T cell activity in solid tumors is limited by immunosuppressive factors, including transforming growth factor β (TGFβ). Here, we describe the development of a switch receptor (SwR), in which the extracellular domains of the TGFβ receptor are fused to the intracellular domains from the IL-2/15 receptor. We evaluated the SwR in tandem with two variants of a CAR that we have developed against STEAP1, a protein highly expressed in prostate cancer. The SwR-CAR T cell activity was assessed against a panel of STEAP1^+/- prostate cancer cell lines with or without over-expression of TGFβ, or with added TGFβ, by use of flow cytometry cytokine and killing assays, Luminex cytokine profiling, cell counts, and flow cytometry phenotyping. The results showed that the SwR-CAR constructs improved the functionality of CAR T cells in TGFβ-rich environments, as measured by T cell proliferation and survival, cytokine response, and cytotoxicity. In assays with four repeated target-cell stimulations, the SwR-CAR T cells developed an activated effector memory phenotype with retained STEAP1-specific activity. In conclusion, the SwR confers CAR T cells with potent and durable in vitro functionality in TGFβ-rich environments. The SwR may be used as an add-on construct for CAR T cells or other forms of adoptive cell therapy.

Chimeric Antigen Receptor T-Cell Therapy: Current Perspective on T Cell-Intrinsic, T Cell-Extrinsic, and Therapeutic Limitations

ABSTRACT

Genetically engineered chimeric antigen receptor (CAR) T-cell therapy leverages the ability of the immune system to eliminate tumors and redirects cytotoxic functions toward cells expressing specified tumor-restricted antigens. Although 6 CAR T-cell therapies have received Food and Drug Administration (FDA) approval for the treatment of many hematological malignancies, limitations involving T cell-intrinsic, T cell-extrinsic, and therapeutic factors remain in the treatment of both liquid and solid tumors. Chimeric antigen receptor design, signals from the tumor microenvironment, tumor antigen escape mechanisms, and systemic inflammatory consequences of CAR T-cell infusion all influence the efficacy and feasibility of CAR T-cell therapy in different malignancies. Here, we review the core structure of the CAR, the evolution of different CAR generations, CAR T-cell therapy limitations, and current strategies being investigated to overcome the T cell-intrinsic, T cell-independent, and therapeutic barriers to successful CAR T-cell therapy.

Standardized in-vitro evaluation of CAR-T cells using acellular artificial target particles

The horizon of immunotherapy using CAR-T cells is continuously extending to treat solid tumors beyond the success in the treatment of liquid tumors. Precise in-vitro evaluations of CAR-T cells for their phenotypes, quantity and quality of activation in various tumor microenvironments including different antigen densities, and the resulting effector functions are critical for the successful development of CAR-T therapies and safe translation to clinics. Unfortunately, the development of methods and tools to accommodate these needs have been lagging behind. Here, we developed a novel biomaterial platform, acellular artificial target particles (aaTPs) against CAR-T cells, using magnetic microbeads that are already widely employed in the manufacturing of T cell products. By devising a simple and standardized procedure, we precisely controlled the antigen surface densities presented on the aaTPs for a wide range. By co-incubation of aaTPs with CAR-T cells followed by flow cytometry and cytokine assays, we quantitatively determined the antigen-specific and dose-dependent activation of anti-HER2 CAR-T cells. We also demonstrated that the aaTP can serve as a clean target cell in in-vitro assays to prove the proposed mechanism of action of a next-generation CAR-T product. Overall, the simple, inexpensive, modular and precisely controllable synthetic nature of aaTPs enables the development of clean and standardized in-vitro assays for CAR-T cells, which provides critical advantages over the conventional assays using target cell lines. The design of aaTPs can be extended to include other tumor antigens and relevant surface molecules of physiological target cells. Thus, the aaTP platform has great potential as a standardized tool for the development and evaluation of both conventional and new CAR-T products in the context of approval from regulatory agencies and clinical translation.

Neuro faces of beneficial T cells: essential in brain, impaired in aging and neurological diseases, and activated functionally by neurotransmitters and neuropeptides

T cells are essential for a healthy life, performing continuously: immune surveillance, recognition, protection, activation, suppression, assistance, eradication, secretion, adhesion, migration, homing, communications, and additional tasks. This paper describes five aspects of normal beneficial T cells in the healthy or diseased brain. First, normal beneficial T cells are essential for normal healthy brain functions: cognition, spatial learning, memory, adult neurogenesis, and neuroprotection. T cells decrease secondary neuronal degeneration, increase neuronal survival after central nervous system (CNS) injury, and limit CNS inflammation and damage upon injury and infection. Second, while pathogenic T cells contribute to CNS disorders, recent studies, mostly in animal models, show that specific subpopulations of normal beneficial T cells have protective and regenerative effects in several neuroinflammatory and neurodegenerative diseases. These include Multiple Sclerosis (MS), Alzheimer's disease, Parkinson's disease, Amyotrophic Lateral Sclerosis (ALS), stroke, CNS trauma, chronic pain, and others. Both T cell-secreted molecules and direct cell-cell contacts deliver T cell neuroprotective, neuroregenerative and immunomodulatory effects. Third, normal beneficial T cells are abnormal, impaired, and dysfunctional in aging and multiple neurological diseases. Different T cell impairments are evident in aging, brain tumors (mainly Glioblastoma), severe viral infections (including COVID-19), chronic stress, major depression, schizophrenia, Parkinson's disease, Alzheimer's disease, ALS, MS, stroke, and other neuro-pathologies. The main detrimental mechanisms that impair T cell function are activation-induced cell death, exhaustion, senescence, and impaired T cell stemness. Fourth, several physiological neurotransmitters and neuropeptides induce by themselves multiple direct, potent, beneficial, and therapeutically-relevant effects on normal human T cells, via their receptors in T cells. This scientific field is called "Nerve-Driven Immunity". The main neurotransmitters and neuropeptides that induce directly activating and beneficial effects on naïve normal human T cells are: dopamine, glutamate, GnRH-II, neuropeptide Y, calcitonin gene-related peptide, and somatostatin. Fifth, "Personalized Adoptive Neuro-Immunotherapy". This is a novel unique cellular immunotherapy, based on the "Nerve-Driven Immunity" findings, which was recently designed and patented for safe and repeated rejuvenation, activation, and improvement of impaired and dysfunctional T cells of any person in need, by ex vivo exposure of the person's T cells to neurotransmitters and neuropeptides. Personalized adoptive neuro-immunotherapy includes an early ex vivo personalized diagnosis, and subsequent ex vivo → in vivo personalized adoptive therapy, tailored according to the diagnosis. The Personalized Adoptive Neuro-Immunotherapy has not yet been tested in humans, pending validation of safety and efficacy in clinical trials, especially in brain tumors, chronic infectious diseases, and aging, in which T cells are exhausted and/or senescent and dysfunctional.

CAR-T manufactured from frozen PBMC yield efficient function with prolonged in vitro production

Chimeric antigen receptor (CAR)-T cells are engineered to identify and eliminate cells expressing a target antigen. Current manufacturing protocols vary between commercial CAR-T cell products warranting an assessment of these methods to determine which approach optimally balances successful manufacturing capacity and product efficacy. One difference between commercial product manufacturing methods is whether T cell engineering begins with fresh (unfrozen) patient cells or cells that have been cryopreserved prior to manufacture. Starting with frozen PBMC material allows for greater manufacturing flexibility, and the possibility of collecting and storing blood from patients prior to multiple lines of therapy. We prospectively analyzed if second generation anti-CD19 CAR-T cells with either CD28 or 4-1BB co-stimulatory domains have different phenotype or function when prepared side-by-side using fresh or cryopreserved PBMCs. We found that cryopreserved PBMC starting material is associated with slower CAR-T cell expansion during manufacture but does not affect phenotype. We also demonstrate that CAR-T cell activation, cytokine production and in vitro anti-tumor cytotoxicity were not different when CAR-T cells were manufactured from fresh or cryopreserved PBMC. As CAR-T cell therapy expands globally, the need for greater flexibility around the timing of manufacture will continue to grow. This study helps support the concept that cryopreservation of PBMCs could be the solution to these issues without compromising the quality of the final CAR-T product.

Combination strategies to optimize the efficacy of chimeric antigen receptor T cell therapy in haematological malignancies

Chimeric antigen receptor (CAR) T cell therapy has revolutionized the therapeutic landscape of haematological malignancies. However, resistance and relapse remain prominent limitations, and they are related to the limited persistence and efficacy of CAR T cells, downregulation or loss of tumour antigens, intrinsic resistance of tumours to death signalling, and immune suppressive microenvironment. Rational combined modality treatments are regarded as a promising strategy to further unlock the antitumor potential of CAR T cell therapy, which can be applied before CAR T cell infusion as a conditioning regimen or in ex vivo culture settings as well as concomitant with or after CAR T cell infusion. In this review, we summarize the combinatorial strategies, including chemotherapy, radiotherapy, haematopoietic stem cell transplantation, targeted therapies and other immunotherapies, in an effort to further enhance the effectiveness of this impressive therapy and benefit more patients.

Virus-Based Immuno-Oncology Models

Immunotherapy has been extensively explored in recent years with encouraging results in selected types of cancer. Such success aroused interest in the expansion of such indications, requiring a deep understanding of the complex role of the immune system in carcinogenesis. The definition of hot vs. cold tumors and the role of the tumor microenvironment enlightened the once obscure understanding of low response rates of solid tumors to immune check point inhibitors. Although the major scope found in the literature focuses on the T cell modulation, the innate immune system is also a promising oncolytic tool. The unveiling of the tumor immunosuppressive pathways, lead to the development of combined targeted therapies in an attempt to increase immune infiltration capability. Oncolytic viruses have been explored in different scenarios, in combination with various chemotherapeutic drugs and, more recently, with immune check point inhibitors. Moreover, oncolytic viruses may be engineered to express tumor specific pro-inflammatory cytokines, antibodies, and antigens to enhance immunologic response or block immunosuppressive mechanisms. Development of preclinical models capable to replicate the human immunologic response is one of the major challenges faced by these studies. A thorough understanding of immunotherapy and oncolytic viruses’ mechanics is paramount to develop reliable preclinical models with higher chances of successful clinical therapy application. Thus, in this article, we review current concepts in cancer immunotherapy including the inherent and synthetic mechanisms of immunologic enhancement utilizing oncolytic viruses, immune targeting, and available preclinical animal models, their advantages, and limitations.