Synapse-tuned CARs enhance immune cell anti-tumor activity

PDZ domains of PATJ facilitate immunological synapse formation to promote T cell activation

BACKGROUND

The highly organized structures of the immunological synapse (IS) are crucial for T cell activation. PDZ domains might be involved in the formation of the IS by serving as docking sites for protein interactions. In this study, we investigate the role of the PALS1-associated tight junction protein (PATJ), which contains 10 PDZ domains, in the formation of IS and its subsequent impact on T cell activation.

METHODS

To elucidate the function of PATJ, we generated murine models with conditional T cell-specific knockout of Patj and assessed T cell activation both in vitro and in vivo within the context of infection and cancer. We employed confocal microscopy to visualize the formation of IS between T cells and antigen-presenting cells in the absence of Patj. A series of PATJ truncations containing different combinations of PDZ domains was used to identify the minimal domain required for effective T cell receptor signaling. The identified active PDZ domain was then incorporated into mesothelin (MSLN)-specific chimeric antigen receptor (CAR) to evaluate its impact on CAR-T cell cytotoxicity against solid tumors.

RESULTS

We observed a rapid increase in PATJ expression during T cell activation. Conditional knockout of Patj in T cells showed impaired immunity against infection and cancer in murine models. Mechanistically, ablation of Patj impedes IS formation, and thus reduces T cell activation. We further showed that engineering the active PDZ domain of PATJ into CAR structure significantly promoted the effector function of CAR-T cells.

CONCLUSIONS

Our study reveals an important role of PATJ in the formation of IS and provides an approach to improve the efficacy of CAR-T therapy.

Novel strategies to manage CAR-T cell toxicity

The immune-related adverse events associated with chimeric antigen receptor (CAR)-T cell therapy result in substantial morbidity as well as considerable cost to the health-care system, and can limit the use of these treatments. Current therapeutic strategies to manage immune-related adverse events include interleukin-6 receptor (IL-6R) blockade and corticosteroids. However, because these interventions do not always address the side effects, nor prevent progression to higher grades of adverse events, new approaches are needed. A deeper understanding of the cell types involved, and their associated signalling pathways, cellular metabolism and differentiation states, should provide the basis for alternative strategies. To preserve treatment efficacy, cytokine-mediated toxicity needs to be uncoupled from CAR-T cell function, expansion, long-term persistence and memory formation. This may be achieved by targeting CAR or independent cytokine signalling axes transiently, and through novel T cell engineering strategies, such as low-affinity CAR-T cells, reversible on-off switches and versatile adaptor systems. We summarize the current management of cytokine release syndrome and immune effector cell-associated neurotoxicity syndrome, and review T cell- and myeloid cell-intrinsic druggable targets and cellular engineering strategies to develop safer CAR-T cells.

Translational study of the regulatory mechanism by which immune synapses enhance immune cell function

Immune synapses, which were initially discovered at the interface between antigen-presenting cells (APCs) and T cells, are special structures formed at the contact site between antigen-presenting cells and immune cells and constitute the structural basis for immune cells to kill tumours and synthesise antibodies. Their structures are very similar to those of neural synapses in the nervous system, and they contain different functional structural regions. With the development of cell visualization research, scientists have increasingly conducted in-depth research on immune synapses. At present, it is known that T cells, B cells, and NK cells can form different immune synapses with target cells. Immune synapses formed by different cell subsets as well as CAR-T cells have their own characteristics, mainly in terms of their structure, formation process and regulatory mechanism. Therefore, how to enhance immune cell killing function by enhancing immune synaptic function has long been a research hotspot. At present, the killing function of immune cells can be enhanced by influencing the signalling molecules of immune synapses and the cell microenvironment and modifying the structure of immune synapses. Through a review of the factors affecting immune synapses, we can better explore the target for enhancing immune system function.

T cell-based cancer immunotherapy: opportunities and challenges

T cells play a central role in the cancer immunity cycle. The therapeutic outcomes of T cell-based intervention strategies are determined by multiple factors at various stages of the cycle. Here, we summarize and discuss recent advances in T cell immunotherapy and potential barriers to it within the framework of the cancer immunity cycle, including T-cell recognition of tumor antigens for activation, T cell trafficking and infiltration into tumors, and killing of target cells. Moreover, we discuss the key factors influencing T cell differentiation and functionality, including TCR stimulation, costimulatory signals, cytokines, metabolic reprogramming, and mechanistic forces. We also highlight the key transcription factors dictating T cell differentiation and discuss how metabolic circuits and specific metabolites shape the epigenetic program of tumor-infiltrating T cells. We conclude that a better understanding of T cell fate decision will help design novel strategies to overcome the barriers to effective cancer immunity.

Increased functional potency of multi-edited CAR-T cells manufactured by a non-viral transfection system

Chimeric antigen receptor (CAR)-T cell therapy represents a breakthrough for the treatment of hematological malignancies. However, to treat solid tumors and certain hematologic cancers, next-generation CAR-T cells require further genetic modifications to overcome some of the current limitations. Improving manufacturing processes to preserve cell health and function of edited T cells is equally critical. Here, we report that Solupore, a Good Manufacturing Practice-aligned, non-viral physicochemical transfection system, can be used to manufacture multi-edited CAR-T cells using CRISPR-Cas9 ribonucleoproteins while maintaining robust cell functionality. When compared to electroporation, an industry standard, T cells that were triple edited using Solupore had reduced levels of apoptosis and maintained similar proportions of stem cell memory T cells with higher oxidative phosphorylation levels. Following lentiviral transduction with a CD19 CAR, and subsequent cryopreservation, triple-edited CAR-T cells manufactured using Solupore demonstrated improved immunological synapse strength to target CD19+ Raji cells and enhanced cellular cytotoxicity compared with electroporated CAR-T cells. In an in vivo mouse model (NSG), Solupore triple-edited CAR-T cells enhanced tumor growth inhibition by more than 30-fold compared to electroporated cells.

Novel FRET-based Immunological Synapse Biosensor for the Prediction of Chimeric Antigen Receptor-T Cell Function

Chimeric antigen receptor (CAR)-T cell therapy has revolutionized cancer treatment. CARs are activated at the immunological synapse (IS) when their single-chain variable fragment (scFv) domain engages with an antigen, allowing them to directly eliminate cancer cells. Here, an innovative IS biosensor based on fluorescence resonance energy transfer (FRET) for the real-time assessment of CAR-IS architecture and signaling competence is presented. Using this biosensor, scFv variants for mesothelin-targeting CARs and identified as a novel scFv with enhanced CAR-T cell functionality despite its lower affinity than the original screened. The original CAR promoted internalization and trogocytosis, disrupting stable IS formation and impairing functionality are further observed. These findings emphasize the importance of enhancing IS quality rather than maximizing scFv affinity for superior CAR-T cell responses. Therefore, the FRET-based IS biosensor is a powerful tool for predicting CAR-T cell function, enabling the efficient engineering of next-generation CARs with enhanced antitumor potency.

Turning cold into hot: emerging strategies to fire up the tumor microenvironment

The tumor microenvironment (TME) is a complex, highly structured, and dynamic ecosystem that plays a pivotal role in the progression of both primary and metastatic tumors. Precise assessment of the dynamic spatiotemporal features of the TME is crucial for understanding cancer evolution and designing effective therapeutic strategies. Cancer is increasingly recognized as a systemic disease, influenced not only by the TME, but also by a multitude of systemic factors, including whole-body metabolism, gut microbiome, endocrine signaling, and circadian rhythm. In this review, we summarize the intrinsic, extrinsic, and systemic factors contributing to the formation of 'cold' tumors within the framework of the cancer-immunity cycle. Correspondingly, we discuss potential strategies for converting 'cold' tumors into 'hot' ones to enhance therapeutic efficacy.

Advances and challenges in chimeric antigen receptor-natural killer cell immunotherapy for cancer

Chimeric antigen receptor (CAR)-natural killer (NK)-cell therapy has emerged as a promising strategy in the treatment of haematological malignancies and solid cancers. Leveraging the innate immune properties of NK cells, CAR-NK-cell therapies offer potential advantages for cell therapy, including safety of use in the allogeneic setting and reduced risk of toxicity. This Nutshell provides an overview of the latest advancements in CAR-NK-cell therapy and the challenges that remain.

Optimising CAR T therapy for the treatment of solid tumors

INTRODUCTION

Adoptive immunotherapy using chimeric antigen receptor (CAR)-engineered T cells has proven transformative in the management of B cell and plasma cel derived malignancies. However, solid tumors have largely proven to be resistant to this therapeutic modality. Challenges include the paucity of safe target antigens, heterogeneity of target expression within the tumor, difficulty in delivery of CAR T cells to the site of disease, poor penetration within solid tumor deposits and inability to circumvent the array of immunosuppressive and biophysical barriers imposed by the solid tumor microenvironment.

AREAS COVERED

Literature was reviewed on the PubMed database, excluding occasional papers which were not available as open access publications or through other means.

EXPERT OPINION

Here, we have surveyed the large body of technological advances that have been made in the quest to bridge the gap toward successful deployment of CAR T cells for the treatment of solid tumors. These encompass the development of more sophisticated targeting strategies to engage solid tumor cells safely and comprehensively, improved drug delivery solutions, design of novel CAR architectures that achieve improved functional persistence and which resist physical, chemical and biological hurdles present in tumor deposits. Prospects for combination therapies that incorporate CAR T cells are also considered.

Protocol to measure cell avidity between cord blood-derived NK cells and leukemia cell line KG-1a

The avidity between immune cells and target cells is crucial for effective immune responses. Here, we present a protocol to measure single-cell avidity between cord blood-derived natural killer (NK) cells and the human acute myelocytic leukemia cell line KG-1a. We describe the steps for isolating cord blood mononuclear cells, purifying NK cells, and culturing KG-1a cells. We then detail the procedures for detecting cell avidity between NK cells and KG-1a cells using the acoustic force-based z-Movi cell avidity analyzer. For complete details on the use and execution of this protocol, please refer to Wang et al.1.

Phase separation of chimeric antigen receptor promotes immunological synapse maturation and persistent cytotoxicity

Major challenges of chimeric antigen receptor (CAR)-T cell therapy include poor antigen sensitivity and cell persistence. Here, we report a solution to these issues by exploiting CAR phase separation. We found that incorporation of an engineered T cell receptor CD3ε motif, EB6I, into the conventional 28Z or BBZ CAR induced self-phase separation through cation-π interactions. EB6I CAR formed a mature immunological synapse with the CD2 corolla to transduce efficient antigen and costimulatory signaling, although its tonic signaling remained low. Functionally, EB6I CAR-T cells exhibited improved signaling and cytotoxicity against low-antigen tumor cells and persistent tumor-killing function. In multiple primary and relapsed murine tumor models, EB6I CAR-T cells exerted better antitumor functions than conventional CAR-T cells against blood and solid cancers. This study thus unveils a CAR engineering strategy to improve CAR-T cell immunity by leveraging molecular condensation and signaling integration.

CAR-armored-cell therapy in solid tumor treatment

Over the past decade, chimeric antigen receptor (CAR)-T cell therapy has emerged as a revolutionary immunotherapeutic approach to combat cancer. This therapy constructs a CAR on the surface of T cells through genetic engineering techniques. The CAR is formed from a combination of antibody-derived or ligand-derived domains and T-cell receptor (TCR) domains. This enables T cells to specifically bind to and activate against tumor cells. However, the efficacy of CAR-T cells in solid tumors remains inconclusive due to several challenges such as poor tumor trafficking, infiltration, and the immunosuppressive tumor microenvironment (TME). In response, CAR natural killer (CAR-NK) and CAR macrophages (CAR-M) have been developed as complementary strategies for solid tumors. CAR-NK cells do not require HLA compatibility, demonstrate reduced toxicity, and are thus seen as potential substitutes for CAR-T cells. Furthermore, CAR-M immunotherapy is also being researched and has shown phagocytic capabilities and tumor-antigen presentation. This study discusses the features, advantages, and limitations of CAR-T, CAR-NK, and CAR-M cells in the treatment of solid tumors and suggests prospective solutions for enhancing the efficacy of CAR host-cell-based immunotherapy.

TCR-mimicking STAR conveys superior sensitivity over CAR in targeting tumors with low-density neoantigens

Targeting tumor-specific neoantigens holds promise for cancer immunotherapy, but their ultra-low expression on tumor cells poses challenges for T cell therapies. Here, we found that chimeric antigen receptors (CARs) exhibit 10-100 times lower sensitivity than T cell receptors (TCRs) when targeting human leukocyte antigen (HLA) class I-presented p53R175H neoantigen. To enhance CAR functionality, we introduced T cell receptor fusion constructs (TRuCs) and synthetic TCRs and antigen receptors (STARs). Our data show that STARs optimally reproduce TCR antigen sensitivity, outperforming CARs and TRuCs in redirecting CD8+ and CD4+ T cells to recognize HLA class I neoantigens. STAR-T cells demonstrate superior killing of cancer cell lines with low neoantigen density in vitro and improved tumor control in mouse models compared to CAR-T and TRuC-T cells. These findings highlight CAR sensitivity limitations and present STARs as more effective synthetic receptors for T cell-based immunotherapy against tumors with low neoantigen density.

Bottom-up synthetic immunology

Infectious diseases and cancer evade immune surveillance using similar mechanisms. Targeting immune mechanisms using common strategies thus represents a promising avenue to improve prevention and treatment. Synthetic immunology can provide such strategies by applying engineering principles from synthetic biology to immunology. Synthetic biologists engineer cells by top-down genetic manipulation or bottom-up assembly from nanoscale building blocks. Recent successes in treating advanced tumours and diseases using genetically engineered immune cells highlight the power of the top-down synthetic immunology approach. However, genetic immune engineering is mostly limited to ex vivo applications and is subject to complex counter-regulation inherent to immune functions. Bottom-up synthetic biology can harness the rich nanotechnology toolbox to engineer molecular and cellular systems from scratch and equip them with desired functions. These are beginning to be tailored to perform targeted immune functions and should hence allow intervention strategies by rational design. In this Perspective we conceptualize bottom-up synthetic immunology as a new frontier field that uses nanotechnology for crucial innovations in therapy and the prevention of infectious diseases and cancer.

Redirecting B7-H3.CAR T Cells to Chemokines Expressed in Osteosarcoma Enhances Homing and Antitumor Activity in Preclinical Models

PURPOSE

Clinical efficacy of chimeric antigen receptor (CAR) T cells against pediatric osteosarcoma (OS) has been limited. One strategy to improve efficacy may be to drive chemokine-mediated homing of CAR T cells to tumors. We sought to determine the primary chemokines secreted by OS and evaluate the efficacy of B7-H3.CAR T cells expressing the cognate receptors.

EXPERIMENTAL DESIGN

We developed a pipeline to identify chemokines secreted by OS by correlating RNA-seq data with chemokine protein detected in media from fresh surgical specimens. We identified CXCR2 and CXCR6 as promising receptors for enhancing CAR T-cell homing against OS. We evaluated the homing kinetics and efficiency of CXCR2- and CXCR6.T cells and homing, cytokine production, and antitumor activity of CXCR2- and CXCR6.B7-H3.CAR T cells in vitro and in vivo.

RESULTS

T cells transgenically expressing CXCR2 or CXCR6 exhibited ligand-specific enhanced migration over T cells modified with nonfunctional control receptors. Differential homing kinetics were observed, with CXCR2.T-cell homing quickly and plateauing early, whereas CXCR6.T cells took longer to home but achieved a similar plateau. When expressed in B7-H3.CAR T cells, CXCR2- and CXCR6 modification conferred enhanced homing toward OS in vitro and in vivo. CXCR2- and CXCR6-B7-H3.CAR-treated mice experienced prolonged survival in a metastatic model compared with B7-H3.CAR T-cell-treated mice.

CONCLUSIONS

Our patient-based pipeline identified targets for chemokine receptor modification of CAR T cells targeting OS. CXCR2 and CXCR6 expression enhanced the homing and anti-OS activity of B7-H3.CAR T cells. These findings support clinical evaluation of CXCR-modified CAR T cells to improve adoptive cell therapy for patients with OS.

The physical landscape of CAR-T synapse

Chimeric antigen receptor (CAR)-T cells form dynamic immunological synapses with their cancer cell targets. After a CAR-antigen engagement, the CAR-T synapse forms, matures, and finally disassembles, accompanied by substantial remodeling of cell surface proteins, lipids, and glycans. In this review, we provide perspectives for understanding protein distribution, membrane topology, and force transmission across the CAR-T synapse. We highlight the features of CAR-T synapses that differ from T cell receptor synapses, including the disorganized protein pattern, adjustable synapse width, diverse mechano-responding properties, and resulting signaling consequences. Through a range of examples, we illustrate how revealing the biophysical nature of the CAR-T synapse could guide the design of CAR-Ts with improved anti-tumor function.

PostFocus: automated selective post-acquisition high-throughput focus restoration using diffusion model for label-free time-lapse microscopy

MOTIVATION

High-throughput time-lapse imaging is a fundamental tool for efficient living cell profiling at single-cell resolution. Label-free phase-contrast video microscopy enables noninvasive, nontoxic, and long-term imaging. The tradeoff between speed and throughput, however, implies that despite the state-of-the-art autofocusing algorithms, out-of-focus cells are unavoidable due to the migratory nature of immune cells (velocities >10 μm/min). Here, we propose PostFocus to (i) identify out-of-focus images within time-lapse sequences with a classifier, and (ii) deploy a de-noising diffusion probabilistic model to yield reliable in-focus images.

RESULTS

De-noising diffusion probabilistic model outperformed deep discriminative models with a superior performance on the whole image and around cell boundaries. In addition, PostFocus improves the accuracy of image analysis (cell and contact detection) and the yield of usable videos.

AVAILABILITY AND IMPLEMENTATION

Open-source code and sample data are available at: https://github.com/kwu14victor/PostFocus.

Advances in preclinical TCR characterization: leveraging cell avidity to identify functional TCRs

T-cell therapy has emerged as an effective approach for treating viral infections and cancers. However, a significant challenge is the selection of T-cell receptors (TCRs) that exhibit the desired functionality. Conventionally in vitro techniques, such as peptide sensitivity measurements and cytotoxicity assays, provide valuable insights into TCR potency but are labor-intensive. In contrast, measuring ligand binding properties (z-Movi technology) could provide an accelerated processing while showing robust correlations with T-cell functions. In this study, we assessed whether cell avidity can predict functionality also in the context of TCR-engineered T cells. To this end, we developed a flexible system for TCR re-expression by generating a Jurkat-derived T cell clone lacking TCR and CD3 expression through CRISPR-Cas9-mediated TRBC knockout. The knockin of a transgenic TCR into the TRAC locus restored TCR/CD3 expression, allowing for CD3-based purification of TCR-engineered T cells. Subsequently, we characterized these engineered cell lines by functional readouts, and assessment of binding properties through the z-Movi technology. Our findings revealed a strong correlation between the cell avidities and functional sensitivities of Jurkat TCR-T cells. Altogether, by integrating cell avidity measurements with our versatile T cell engineering platform, we established an accelerated system for enhancing the in vitro selection of clinically relevant TCRs.

Generation of non-genetically modified, CAR-like, NK cells

BACKGROUND

Natural killer (NK) cell therapy is considered an attractive and safe strategy for anticancer therapy. Nevertheless, when autologous or allogenic NK cells are used alone, the clinical benefit has been disappointing. This is partially due to the lack of target specificity. Recently, CD19-specific chimeric antigen receptor (CAR)-NK cells have proven to be safe and potent in patients with B-cell tumors. However, the generation of CAR-NK cells is a complicated manufacturing process. We aim at developing a targeted NK cell therapy without the need for cellular genetic modifications. We took advantage of the natural expression of the IgG Fc receptor CD16a (FcγRIIIa) to induce strong antigen-specific effector functions through antibody-dependent cell-mediated cytotoxicity (ADCC). We have generated the new technology "Pin", which enables the arming of modified monoclonal antibodies (mAbs) onto the CD16a of ex vivo expanded NK (eNK) cells. Methods Ex vivo eNK were prepared from umbilical cord blood cells and expanded using interleukin (IL)-2/IL-15 and Epstein-Barr virus (EBV)-transformed B-lymphoblastoid feeder cells. mAbs were engineered with four substitutions called Pin mutations to increase their affinity to CD16a. eNK were incubated with anti-CD20 or anti-CD19 Pin-mAbs to generate "armed" eNK and were used to assess effector functions in vitro on cancer cell lines, lymphoma patient cells and in vivo.

RESULTS

CD16a/Pin-mAb interaction is stable for several days and Pin-mAb eNK inherit the mAb specificity and exclusively induce ADCC against targets expressing the cognate antigen. Hence, Pin-mAbs confer long-term selectivity to eNK, which allows specific elimination of the target cells in several in vivo mouse models. Finally, we showed that it is possible to arm eNK with at least two Pin-mAbs simultaneously, to increase efficacy against heterogenous cancer cell populations.

CONCLUSIONS

The Pin technology provides an off-the-shelf NK cell therapy platform to generate CAR-like NK cells, without genetic modifications, that easily target multiple tumor antigens.

CAR-T cell expansion platforms yield distinct T cell differentiation states

With investigators looking to expand engineered T cell therapies such as CAR-T to new tumor targets and patient populations, a variety of cell manufacturing platforms have been developed to scale manufacturing capacity using closed and/or automated systems. Such platforms are particularly useful for solid tumor targets, which typically require higher CAR-T cell doses. Although T cell phenotype and function are key attributes that often correlate with therapeutic efficacy, how manufacturing platforms influence the final CAR-T cell product is currently unknown. We compared 4 commonly used T cell manufacturing platforms (CliniMACS Prodigy, Xuri W25 rocking platform, G-Rex gas-permeable bioreactor, static bag culture) using identical media, stimulation, culture length, and donor starting material. Selected CD4+CD8+ cells were transduced with lentiviral vector incorporating a CAR targeting FGFR4, a promising target for pediatric sarcoma. We observed significant differences in overall expansion over the 14-day culture; bag cultures had the highest capacity for expansion while the Prodigy had the lowest (481-fold versus 84-fold, respectively). Strikingly, we also observed considerable differences in the phenotype of the final product, with the Prodigy significantly enriched for CCR7+CD45RA+ naïve/stem central memory (Tn/scm)-like cells at 46% compared to bag and G-Rex with 16% and 13%, respectively. Gene expression analysis also showed that Prodigy CAR-Ts are more naïve, less cytotoxic and less exhausted than bag, G-Rex, and Xuri CAR-Ts, and pointed to differences in cell metabolism that were confirmed via metabolic assays. We hypothesized that dissolved oxygen level, which decreased substantially during the final 3 days of the Prodigy culture, may contribute to the observed differences in T cell phenotype. By culturing bag and G-Rex cultures in 1% O2 from day 5 onward, we could generate >60% Tn/scm-like cells, with longer time in hypoxia correlating with a higher percentage of Tn/scm-like cells. Intriguingly, our results suggest that oxygenation is responsible, at least in part, for observed differences in T cell phenotype among bioreactors and suggest hypoxic culture as a potential strategy prevent T cell differentiation during expansion. Ultimately, our study demonstrates that selection of bioreactor system may have profound effects not only on the capacity for expansion, but also on the differentiation state of the resulting CAR-T cells.

CXCR4 has a dual role in improving the efficacy of BCMA-redirected CAR-NK cells in multiple myeloma

Multiple myeloma (MM) is a plasma cell disease with a preferential bone marrow (BM) tropism. Enforced expression of tissue-specific chemokine receptors has been shown to successfully guide adoptively-transferred CAR NK cells towards the malignant milieu in solid cancers, but also to BM-resident AML and MM. For redirection towards BM-associated chemokine CXCL12, we armored BCMA CAR-NK-92 as well as primary NK cells with ectopic expression of either wildtype CXCR4 or a gain-of-function mutant CXCR4R334X. Our data showed that BCMA CAR-NK-92 and -primary NK cells equipped with CXCR4 gained an improved ability to migrate towards CXCL12 in vitro. Beyond its classical role coordinating chemotaxis, CXCR4 has been shown to participate in T cell co-stimulation, which prompted us to examine the functionality of CXCR4-cotransduced BCMA-CAR NK cells. Ectopic CXCR4 expression enhanced the cytotoxic capacity of BCMA CAR-NK cells, as evidenced by the ability to eliminate BCMA-expressing target cell lines and primary MM cells in vitro and through accelerated cytolytic granule release. We show that CXCR4 co-modification prolonged BCMA CAR surface deposition, augmented ZAP-70 recruitment following CAR-engagement, and accelerated distal signal transduction kinetics. BCMA CAR sensitivity towards antigen was enhanced by virtue of an enhanced ZAP-70 recruitment to the immunological synapse, revealing an increased propensity of CARs to become triggered upon CXCR4 overexpression. Unexpectedly, co-stimulation via CXCR4 occurred in the absence of CXCL12 ligand-stimulation. Collectively, our findings imply that co-modification of CAR-NK cells with tissue-relevant chemokine receptors affect adoptive NK cell therapy beyond improved trafficking and retention within tumor sites.

Venetoclax acts as an immunometabolic modulator to potentiate adoptive NK cell immunotherapy against leukemia

Natural killer (NK) cell-based immunotherapy holds promise for cancer treatment; however, its efficacy remains limited, necessitating the development of alternative strategies. Here, we report that venetoclax, an FDA-approved BCL-2 inhibitor, directly activates NK cells, enhancing their cytotoxicity against acute myeloid leukemia (AML) both in vitro and in vivo, likely independent of BCL-2 inhibition. Through comprehensive approaches, including bulk and single-cell RNA sequencing, avidity measurement, and functional assays, we demonstrate that venetoclax increases the avidity of NK cells to AML cells and promotes lytic granule polarization during immunological synapse (IS) formation. Notably, we identify a distinct CD161lowCD218b+ NK cell subpopulation that exhibits remarkable sensitivity to venetoclax treatment. Furthermore, venetoclax promotes mitochondrial respiration and ATP synthesis via the NF-κB pathway, thereby facilitating IS formation in NK cells. Collectively, our findings establish venetoclax as a multifaceted immunometabolic modulator of NK cell function and provide a promising strategy for augmenting NK cell-based cancer immunotherapy.

Molecular pixelation: spatial proteomics of single cells by sequencing

The spatial distribution of cell surface proteins governs vital processes of the immune system such as intercellular communication and mobility. However, fluorescence microscopy has limited scalability in the multiplexing and throughput needed to drive spatial proteomics discoveries at subcellular level. We present Molecular Pixelation (MPX), an optics-free, DNA sequence-based method for spatial proteomics of single cells using antibody-oligonucleotide conjugates (AOCs) and DNA-based, nanometer-sized molecular pixels. The relative locations of AOCs are inferred by sequentially associating them into local neighborhoods using the sequence-unique DNA pixels, forming >1,000 spatially connected zones per cell in 3D. For each single cell, DNA-sequencing reads are computationally arranged into spatial proteomics networks for 76 proteins. By studying immune cell dynamics using spatial statistics on graph representations of the data, we identify known and new patterns of spatial organization of proteins on chemokine-stimulated T cells, highlighting the potential of MPX in defining cell states by the spatial arrangement of proteins.

CAR T cells redirected to B7-H3 for pediatric solid tumors: Current status and future perspectives

Despite intensive therapies, pediatric patients with relapsed or refractory solid tumors have poor outcomes and need novel treatments. Immune therapies offer an alternative to conventional treatment options but require the identification of differentially expressed antigens to direct antitumor activity to sites of disease. B7-H3 (CD276) is an immune regulatory protein that is expressed in a range of malignancies and has limited expression in normal tissues. B7-H3 is highly expressed in pediatric solid tumors including osteosarcoma, rhabdomyosarcoma, Ewing sarcoma, Wilms tumor, neuroblastoma, and many rare tumors. In this article we review B7-H3-targeted chimeric antigen receptor (B7-H3-CAR) T cell therapies for pediatric solid tumors, reporting preclinical development strategies and outlining the landscape of active pediatric clinical trials. We identify challenges to the success of CAR T cell therapy for solid tumors including localizing to and penetrating solid tumor sites, evading the hostile tumor microenvironment, supporting T cell expansion and persistence, and avoiding intrinsic tumor resistance. We highlight strategies to overcome these challenges and enhance the effect of B7-H3-CAR T cells, including advanced CAR T cell design and incorporation of combination therapies.

Chimeric antigen receptor T-cell therapy in childhood acute myeloid leukemia: how far are we from a clinical application?

Recurrent and/or refractory (R/R) pediatric acute myeloid leukemia (AML) remains a recalcitrant disease with poor outcomes. Cell therapy with genetically modified immune effector cells holds the promise to improve outcomes for R/R AML since it relies on cytotoxic mechanisms that are distinct from chemotherapeutic agents. While T cells expressing chimeric antigen receptors (CAR T cells) showed significant anti-AML activity in preclinical models, early phase clinical studies have demonstrated limited activity, irrespective of the targeted AML antigen. Lack of efficacy is most likely multifactorial, including: (i) a limited array of AML-specific targets and target antigen heterogeneity; (ii) the aggressive nature of R/R AML and heavy pretreatment of patients; (iii) T-cell product manufacturing, and (iv) limited expansion and persistence of the CAR T cells, which is in part driven by the immunosuppressive AML microenvironment. Here we review the results of early phase clinical studies with AML-specific CAR T cells, and avenues investigators are exploring to improve their effector function.

Newer generations of multi-target CAR and STAb-T immunotherapeutics: NEXT CART Consortium as a cooperative effort to overcome current limitations

Adoptive T cellular immunotherapies have emerged as relevant approaches for treating cancer patients who have relapsed or become refractory (R/R) to traditional cancer treatments. Chimeric antigen receptor (CAR) T-cell therapy has improved survival in various hematological malignancies. However, significant limitations still impede the widespread adoption of these therapies in most cancers. To advance in this field, six research groups have created the "NEXT Generation CART MAD Consortium" (NEXT CART) in Madrid's Community, which aims to develop novel cell-based immunotherapies for R/R and poor prognosis cancers. At NEXT CART, various basic and translational research groups and hospitals in Madrid concur to share and synergize their basic expertise in immunotherapy, gene therapy, and immunological synapse, and clinical expertise in pediatric and adult oncology. NEXT CART goal is to develop new cell engineering approaches and treatments for R/R adult and pediatric neoplasms to evaluate in multicenter clinical trials. Here, we discuss the current limitations of T cell-based therapies and introduce our perspective on future developments. Advancement opportunities include developing allogeneic products, optimizing CAR signaling domains, combining cellular immunotherapies, multi-targeting strategies, and improving tumor-infiltrating lymphocytes (TILs)/T cell receptor (TCR) therapy. Furthermore, basic studies aim to identify novel tumor targets, tumor molecules in the tumor microenvironment that impact CAR efficacy, and strategies to enhance the efficiency of the immunological synapse between immune and tumor cells. Our perspective of current cellular immunotherapy underscores the potential of these treatments while acknowledging the existing hurdles that demand innovative solutions to develop their potential for cancer treatment fully.

Mechanical force determines chimeric antigen receptor microclustering and signaling

Chimeric antigen receptor (CAR) T cells are activated to trigger the lytic machinery after antigen engagement, and this has been successfully applied clinically as therapy. The mechanism by which antigen binding leads to the initiation of CAR signaling remains poorly understood. Here, we used a set of short double-stranded DNA (dsDNA) tethers with mechanical forces ranging from ∼12 to ∼51 pN to manipulate the mechanical force of antigen tether and decouple the microclustering and signaling events. Our results revealed that antigen-binding-induced CAR microclustering and signaling are mechanical force dependent. Additionally, the mechanical force delivered to the antigen tether by the CAR for microclustering is generated by autonomous cell contractility. Mechanistically, the mechanical-force-induced strong adhesion and CAR diffusion confinement led to CAR microclustering. Moreover, cytotoxicity may have a lower mechanical force threshold than cytokine generation. Collectively, these results support a model of mechanical-force-induced CAR microclustering for signaling.

Evidence and therapeutic implications of biomechanically regulated immunosurveillance in cancer and other diseases

Disease progression is usually accompanied by changes in the biochemical composition of cells and tissues and their biophysical properties. For instance, hallmarks of cancer include the stiffening of tissues caused by extracellular matrix remodelling and the softening of individual cancer cells. In this context, accumulating evidence has shown that immune cells sense and respond to mechanical signals from the environment. However, the mechanisms regulating these mechanical aspects of immune surveillance remain partially understood. The growing appreciation for the 'mechano-immunology' field has urged researchers to investigate how immune cells sense and respond to mechanical cues in various disease settings, paving the way for the development of novel engineering strategies that aim at mechanically modulating and potentiating immune cells for enhanced immunotherapies. Recent pioneer developments in this direction have laid the foundations for leveraging 'mechanical immunoengineering' strategies to treat various diseases. This Review first outlines the mechanical changes occurring during pathological progression in several diseases, including cancer, fibrosis and infection. We next highlight the mechanosensitive nature of immune cells and how mechanical forces govern the immune responses in different diseases. Finally, we discuss how targeting the biomechanical features of the disease milieu and immune cells is a promising strategy for manipulating therapeutic outcomes.

Tunable Cell-Adhesive Surfaces by Surface-Initiated Photoinduced Electron-Transfer-Reversible Addition-Fragmentation Chain-Transfer Polymerization

Cell adhesion involves many interactions between various molecules on the cell membrane (receptors, coreceptors, integrins, etc.) and surfaces or other cells. Cell adhesion plays a crucial role in the analysis of immune response, cancer treatment, tissue engineering, etc. Cell-cell adhesion can be quantified by measuring cell avidity, which defines the total interaction strength of the live cell binding. Typically, those investigations use tailor-made, reusable chips or surfaces onto which cells are cultured to form a monolayer to which other cells can bind. Cell avidity can then be measured by applying a force and quantifying cell-cell bond ruptures. The subsequent cleaning and reactivation of such biochip and biointeractive surfaces often require repeated etching, leading to device damage. Furthermore, it is often of great interest to harvest the cells that remain bound at the end of an avidity experiment for further analysis or use. It is, therefore, advantageous to pursue coating methods that allow tunable cell adhesion. This work presents temperature-switchable poly(di(ethylene glycol) methyl ether methacrylate) brush-based cell-interactive coatings produced by surface-initiated photoinduced electron-transfer reversible addition-fragmentation chain-transfer polymerization. The temperature switch of these brushes was explored by using a quartz crystal microbalance with dissipation monitoring, chemical composition, and physicochemical properties by atom force microscopy, X-ray photoelectron spectroscopy, single-molecule force spectroscopy, and ellipsometry.

Programmable synthetic receptors: the next-generation of cell and gene therapies

Cell and gene therapies hold tremendous promise for treating a range of difficult-to-treat diseases. However, concerns over the safety and efficacy require to be further addressed in order to realize their full potential. Synthetic receptors, a synthetic biology tool that can precisely control the function of therapeutic cells and genetic modules, have been rapidly developed and applied as a powerful solution. Delicately designed and engineered, they can be applied to finetune the therapeutic activities, i.e., to regulate production of dosed, bioactive payloads by sensing and processing user-defined signals or biomarkers. This review provides an overview of diverse synthetic receptor systems being used to reprogram therapeutic cells and their wide applications in biomedical research. With a special focus on four synthetic receptor systems at the forefront, including chimeric antigen receptors (CARs) and synthetic Notch (synNotch) receptors, we address the generalized strategies to design, construct and improve synthetic receptors. Meanwhile, we also highlight the expanding landscape of therapeutic applications of the synthetic receptor systems as well as current challenges in their clinical translation.

Toward the clinical development of synthetic immunity to cancer

Synthetic biology (synbio) tools, such as chimeric antigen receptors (CARs), have been designed to target, activate, and improve immune cell responses to tumors. These therapies have demonstrated an ability to cure patients with blood cancers. However, there are significant challenges to designing, testing, and efficiently translating these complex cell therapies for patients who do not respond or have immune refractory solid tumors. The rapid progress of synbio tools for cell therapy, particularly for cancer immunotherapy, is encouraging but our development process should be tailored to increase translational success. Particularly, next-generation cell therapies should be rooted in basic immunology, tested in more predictive preclinical models, engineered for potency with the right balance of safety, educated by clinical findings, and multi-faceted to combat a range of suppressive mechanisms. Here, we lay out five principles for engineering future cell therapies to increase the probability of clinical impact, and in the context of these principles, we provide an overview of the current state of synbio cell therapy design for cancer. Although these principles are anchored in engineering immune cells for cancer therapy, we posit that they can help guide translational synbio research for broad impact in other disease indications with high unmet need.

Genetic ablation of adhesion ligands averts rejection of allogeneic immune cells

Allogeneic cell therapies hold promise for broad clinical implementation, but face limitations due to potential rejection by the recipient immune system. Silencing of beta-2-microglobulin ( B2M ) expression is commonly employed to evade T cell-mediated rejection, although absence of B2M triggers missing-self responses by recipient natural killer (NK) cells. Here, we demonstrate that deletion of the adhesion ligands CD54 and CD58 on targets cells robustly dampens NK cell reactivity across all sub-populations. Genetic deletion of CD54 and CD58 in B2M -deficient allogeneic chimeric antigen receptor (CAR) T and multi-edited induced pluripotent stem cell (iPSC)-derived NK cells reduces their susceptibility to rejection by NK cells in vitro and in vivo without affecting their anti-tumor effector potential. Thus, these data suggest that genetic ablation of adhesion ligands effectively alleviates rejection of allogeneic immune cells for immunotherapy.

Actin cytoskeleton remodeling at the cancer cell side of the immunological synapse: good, bad, or both?

Cytotoxic lymphocytes (CLs), specifically cytotoxic T lymphocytes and natural killer cells, are indispensable guardians of the immune system and orchestrate the recognition and elimination of cancer cells. Upon encountering a cancer cell, CLs establish a specialized cellular junction, known as the immunological synapse that stands as a pivotal determinant for effective cell killing. Extensive research has focused on the presynaptic side of the immunological synapse and elucidated the multiple functions of the CL actin cytoskeleton in synapse formation, organization, regulatory signaling, and lytic activity. In contrast, the postsynaptic (cancer cell) counterpart has remained relatively unexplored. Nevertheless, both indirect and direct evidence has begun to illuminate the significant and profound consequences of cytoskeletal changes within cancer cells on the outcome of the lytic immunological synapse. Here, we explore the understudied role of the cancer cell actin cytoskeleton in modulating the immune response within the immunological synapse. We shed light on the intricate interplay between actin dynamics and the evasion mechanisms employed by cancer cells, thus providing potential routes for future research and envisioning therapeutic interventions targeting the postsynaptic side of the immunological synapse in the realm of cancer immunotherapy. This review article highlights the importance of actin dynamics within the immunological synapse between cytotoxic lymphocytes and cancer cells focusing on the less-explored postsynaptic side of the synapse. It presents emerging evidence that actin dynamics in cancer cells can critically influence the outcome of cytotoxic lymphocyte interactions with cancer cells.

Application of natural killer immunotherapy in blood cancers and solid tumors

PURPOSE OF REVIEW

Natural killer (NK) cells are innate lymphoid cells characterized by their ability to attack aberrant and cancerous cells. In contrast to the activation of T-cells, NK cell activation is controlled by the interaction of NK cell receptors and their target cells in a manner independent of antigen organization. Due to NK cells' broad array of activation cues, they have gained great attention as a potential therapeutic agent in cancer immunotherapy.

RECENT FINDINGS

Ex vivo activation, expansion, and genetic modifications, such as the addition of a chimeric antigen receptor (CAR), will allow the next generation of NK cells to enhance cytotoxicity, promote survival, and create "off-the-shelf" products. In addition to these that are poised to greatly enhance their clinical activity, the inherent lack of potential for causing graft-versus-host disease (GVHD) and cytokine release syndrome (CRS) suggest that CAR NK cells have the potential to be complementary to CAR-T cells as a component of therapeutic strategies for cancer.

SUMMARY

In this review, we will provide a general understanding of NK cell biology, CAR-NK cell advantages over CAR-T cell therapy, barriers to making NK cell immunotherapy viable, and current NK cell clinical trials for hematological malignancies and solid tumors. The next generation of NK cells has potential to change the circumstances guiding present cancer immunotherapies.