4-1BB enhancement of CAR T function requires NF-κB and TRAFs

From concept to cure: The evolution of CAR-T cell therapy

Chimeric antigen receptor (CAR)-T cell therapy has revolutionized cancer immunotherapy in the 21st century, providing innovative solutions and life-saving therapies for previously untreatable diseases. This approach has shown remarkable success in treating various hematological malignancies and is now expanding into clinical trials for solid tumors, such as prostate cancer and glioblastoma, as well as infectious and autoimmune diseases. CAR-T cell therapy involves harvesting a patient's T cells, genetically engineering them with viral vectors to express CARs targeting specific antigens and reinfusing the modified cells into the patient. These CAR-T cells function independently of major histocompatibility complex (MHC) antigen presentation, selectively identifying and eliminating target cells. This review highlights the key milestones in CAR-T cell evolution, from its invention to its clinical applications. It outlines the historical timeline leading to the invention of CAR-T cells, discusses the major achievements that have transformed them into a breakthrough therapy, and addresses remaining challenges, including high manufacturing costs, limited accessibility, and toxicity issues such as cytokine release syndrome and immune effector cell-associated neurotoxicity syndrome. Additionally, the review explores future directions and advances in the field, such as developing next-generation CAR-T cells aiming to maximize efficacy, minimize toxicity, and broaden therapeutic applications.

Engineering TCR-controlled fuzzy logic into CAR T cells enhances therapeutic specificity

Chimeric antigen receptor (CAR) T cell immunotherapy represents a breakthrough in the treatment of hematological malignancies, but poor specificity has limited its applicability to solid tumors. By contrast, natural T cells harboring T cell receptors (TCRs) can discriminate between neoantigen-expressing cancer cells and self-antigen-expressing healthy tissues but have limited potency against tumors. We used a high-throughput platform to systematically evaluate the impact of co-expressing a TCR and CAR on the same CAR T cell. While strong TCR-antigen interactions enhanced CAR activation, weak TCR-antigen interactions actively antagonized their activation. Mathematical modeling captured this TCR-CAR crosstalk in CAR T cells, allowing us to engineer dual TCR/CAR T cells targeting neoantigens (HHATL8F/p53R175H) and human epithelial growth factor receptor 2 (HER2) ligands, respectively. These T cells exhibited superior anti-cancer activity and minimal toxicity against healthy tissue compared with conventional CAR T cells in a humanized solid tumor mouse model. Harnessing pre-existing inhibitory crosstalk between receptors, therefore, paves the way for the design of more precise cancer immunotherapies.

Mechanisms underlying resistance to CAR-T cell therapy and strategies for enhancement

Chimeric antigen receptor (CAR) T-cell therapy has emerged as a revolutionary approach in the treatment of hematological malignancies, including acute lymphoblastic leukemia, B-cell lymphoma, and multiple myeloma. Despite its promise, the clinical efficacy is often hampered by transient efficacy and subsequent relapse, which curtail the long-term success of this treatment. Current research focuses on overcoming these obstacles by exploring multitarget strategies and optimizing CAR-T cell design. This review summarizes recent insights into the resistance mechanisms associated with CAR-T cell therapy, and delineates emerging strategies for optimized CAR construction, including targeting multiple antigens, improving CAR design, and enhancing T-cell persistence. The goal is to provide a comprehensive overview of the field's current landscape to guide future research and the clinical application of CAR-T cell therapies.

Epigenetic landscapes drive CAR-T cell kinetics and fate decisions: Bridging persistence and resistance

Chimeric antigen receptor-T (CAR-T) cell therapy has revolutionized the treatment paradigm for B-cell malignancies and holds promise for solid tumor immunotherapy. However, CAR-T-cell therapy still faces many challenges, especially primary and secondary resistance. Some mechanisms of resistance, including CAR-T-cell dysfunction, an inhibitory tumor microenvironment, and tumor-intrinsic resistance, have been identified in previous studies. As insights into CAR-T-cell biology have increased, the role of epigenetic reprogramming in influencing the clinical effectiveness of CAR-T cells has become increasingly recognized. An increasing number of direct and indirect epigenetic targeting methods are being developed in combination with CAR-T-cell therapy. In this review, we emphasize the broad pharmacological links between epigenetic therapies and CAR-T-cell therapy, not only within CAR-T cells but also involving tumors and the tumor microenvironment. To elucidate the mechanisms through which epigenetic therapies promote CAR-T-cell therapy, we provide a comprehensive overview of the epigenetic basis of CAR-T-cell kinetics and differentiation, tumor-intrinsic factors and the microenvironment. We also describe some epigenetic strategies that have implications for CAR-T-cell therapy in the present and future. Because targeting epigenetics can have pleiotropic effects, developing more selective and less toxic targeting strategies and determining the optimal administration strategy in clinical trials are the focus of the next phase of research. In summary, we highlight the possible mechanisms and clinical potential of epigenetic regulation in CAR-T-cell therapy.

Immunomodulatory Effects of Curcumin on CAR T-Cell Therapy

Chimeric Antigen Receptor (CAR) T-cell therapy has revolutionized the treatment of hematological malignancies, demonstrating high efficacy in targeting and eliminating cancer cells. However, its clinical application can be associated with the risk of acute adverse effects, including cytokine release syndrome (CRS), a severe inflammatory response caused by excessive cytokine production. While anti-cytokine therapies are available to manage CRS, additional strategies are needed to optimize CAR T-cell efficacy with reduced toxicities. Curcumin, a bioactive polyphenol known for its anti-inflammatory and antioxidant properties, represents a promising adjunct for CAR T-cell therapy. In this study, we investigated the effects of curcumin on anti-CD19 CAR T-cells in vitro. Our results show that curcumin enhances the cytotoxic activity of CAR T-cells against Nalm-6, a B-cell acute lymphoblastic leukemia model, while reducing the production of pro-inflammatory cytokines, including IL-2 and IFN-γ. To explore its underlying mechanisms, network pharmacology and molecular docking analyses were performed, which revealed that curcumin interacts with key signaling pathways involved in T-cell activation and cytokine regulation. These findings support the potential of curcumin as a therapeutic adjunct to improve CAR T-cell efficacy while mitigating inflammatory toxicity.

Targeting BCL11B in CAR-engineered lymphoid progenitors drives NK-like cell development with prolonged anti-leukemic activity

Chimeric antigen receptor (CAR)-induced suppression of the transcription factor B cell CLL/lymphoma 11B (BCL11B) propagates CAR-induced killer (CARiK) cell development from lymphoid progenitors. Here, we show that CRISPR-Cas9-mediated Bcl11b knockout in human and murine early lymphoid progenitors distinctively modulates this process either alone or in combination with a CAR. Upon adoptive transfer into hematopoietic stem cell recipients, Bcl11b-edited progenitors mediated innate-like antigen-independent anti-leukemic immune responses. With CAR expression allowing for additional antigen-specific responses, the progeny of double-edited lymphoid progenitors acquired prolonged anti-leukemic activity in vivo. These findings give important insights into how Bcl11b targeting can be used to tailor anti-leukemia functionality of CAR-engineered lymphoid progenitor cells.

Human Immune Responses to Epstein-Barr Virus Highlighted by Immunodeficiencies

Inborn errors of immunity (IEIs) represent unique in natura models that uncover key components of immunity in humans, in particular those that predispose to infections. Epstein-Barr virus (EBV) is one of the most common opportunistic infectious agents in humans and is responsible for several diseases, including infectious mononucleosis, nonmalignant and malignant lymphoproliferative disorders, hemophagocytic lymphohistiocytosis, and smooth muscle and epithelial tumors. For most individuals, EBV infection persists for life without pathological consequences. IEIs that do not predispose to EBV infection suggest that innate and humoral responses are not necessary or redundant for the immune response to EBV. IEIs associated with high susceptibility to EBV infection provide unequivocal genetic proof of the central role of CD8+ T cell responses in immunity to EBV. They also highlight the distinct steps and pathways required for, on the one hand, the effector cytotoxic functions of CD8+ T cells and, on the other hand, the expansion and maturation of cytotoxic CD8+ T cells.

Advances in CAR optimization strategies based on CD28

Chimeric antigen receptor (CAR)-T cell therapy, which utilizes genetic engineering techniques to modify T-cells to achieve specific targeting of cancer cells, has made significant breakthroughs in cancer treatment in recent years. All marketed CAR-T products are second-generation CAR-T cells containing co-stimulatory structural domains, and co-stimulatory molecules are critical for CAR-T cell activation and function. Although CD28-based co-stimulatory molecules have demonstrated potent cytotoxicity in the clinical application of CAR-T cells, they still suffer from high post-treatment relapse rates, poor efficacy durability, and accompanying severe adverse reactions. In recent years, researchers have achieved specific results in enhancing the anti-tumor function of CD28 by mutating its signaling motifs, combining the co-stimulatory structural domains, and modifying other CAR components besides co-stimulation. This paper reviewed the characteristics and roles of CD28 in CAR-T cell-mediated anti-tumor signaling and activation. We explored potential strategies to enhance CAR-T cell efficacy and reduce side effects by optimizing CD28 motifs and CAR structures, aiming to provide a theoretical basis for further clinical CAR-T cell therapy development.

PD1-TLR10 fusion protein enhances the antitumor efficacy of CAR-T cells in colon cancer

BACKGROUND

The immunosuppressive microenvironment negatively affects the efficacy of chimeric antigen receptor T (CAR-T) cells in solid tumors. Fusion protein that combining extracellular domain of inhibitory checkpoint protein and the cytoplasmic domain of stimulatory molecule may improve the efficacy of CAR-T cells by reversing the suppressive signals.

METHODS

To generate optimal PD1-TLR10 fusion proteins, PD1 extracellular domain and TLR10 intracellular domain were connected by transmembrane domain from PD1, CD28, or TLR10, respectively. The fusion protein was co-expressed with second generation anti-CEA CAR in the same retroviral vector. The effector function and the efficacy of fusion protein armored CAR-T cells was evaluated in vitro and in vivo.

RESULTS

PD1-TLR10 armored CEA CAR-T cells showed stronger cytotoxicity and cytokine release against CEA-positive tumor cells. Specifically, CAR-T cells with fusion protein containing TLR10 transmembrane domain demonstrated better anti-tumor activity in xenograft mouse model.

CONCLUSION

Our study demonstrated that CEA CAR-T armored with rational designed PD1-TLR10 fusion protein had improved efficacy in colon cancer.

Antibiotic-induced loss of gut microbiome metabolic output correlates with clinical responses to CAR T-cell therapy

ABSTRACT

Antibiotic (ABX)-induced microbiome dysbiosis is widespread in oncology, adversely affecting outcomes and side effects of various cancer treatments, including immune checkpoint inhibitors and chimeric antigen receptor T-cell (CAR-T) therapies. In this study, we observed that prior exposure to broad-spectrum ABXs with extended anaerobic coverage such as piperacillin-tazobactam and meropenem was associated with worse anti-CD19 CAR-T therapy survival outcomes in patients with large B-cell lymphoma (N = 422) than other ABX classes. In a discovery subset of these patients (n = 67), we found that the use of these ABXs was in turn associated with substantial dysbiosis of gut microbiome function, resulting in significant alterations of the gut and blood metabolome, including microbial effectors such as short-chain fatty acids (SCFAs) and other anionic metabolites, findings that were largely reproduced in an external validation cohort (n = 58). Broader evaluation of circulating microbial metabolites revealed reductions in indole and cresol derivatives, as well as trimethylamine N-oxide, in patients who received ABX treatment (discovery, n = 40; validation, n = 28). These findings were recapitulated in an immune-competent CAR-T mouse model, in which meropenem-induced dysbiosis led to a systemic dysmetabolome and decreased murine anti-CD19 CAR-T efficacy. Furthermore, we demonstrate that SCFAs can enhance the metabolic fitness of CAR-Ts, leading to improved tumor killing capacity. Together, these results suggest that broad-spectrum ABX deplete metabolically active commensals whose metabolites are essential for enhancing CAR-T efficacy, shedding light on the intricate relationship between ABX exposure, microbiome function and their impact on CAR-T efficacy. This highlights the potential for modulating the microbiome to augment CAR-T immunotherapy. This trial was registered at www.clinicaltrials.gov as #NCT06218602.

Strategies following failure of CAR-T-cell therapy in non-Hodgkin lymphoma

Several CD19 CAR-T-cell drugs are approved for safety and efficacy in advanced B-cell cancers with encouraging results. However, primary refractory and relapse are common. We critically analyze long-term data on efficacy of CD19 CAR-T-cell therapies in B-cell non-Hodgkin lymphomas from clinical trials with those of so-called real world data. We identify co-variates associated with efficacy, discuss mechanisms of relapse, summarize the data on the results of post-failure therapy including allotransplants, monoclonal and bi-specific antibodies, antibody-drug conjugates, immune checkpoint-inhibitors and repeat infusions of CAR-T-cells. We conclude, save for allotransplants, there are few data strongly supporting any of these interventions. Most trial are with few heterogeneously-treated subjects with diverse interventions and brief follow-up. Interventions need to be tailored to the cause(s) of CAR-T-cell failure. Prestly, there is not a convincingly safe and effective therapy of people failing initial CAR-T-cell therapy of B-cell non-Hodgkin lymphoma.

Leucine zipper-based immunomagnetic purification of CAR T cells displaying multiple receptors

Resistance to chimaeric antigen receptor (CAR) T cell therapy develops through multiple mechanisms, most notably antigen loss and tumour-induced immune suppression. It has been suggested that T cells expressing multiple CARs may overcome the resistance of tumours and that T cells expressing receptors that switch inhibitory immune-checkpoint signals into costimulatory signals may enhance the activity of the T cells in the tumour microenvironment. However, engineering multiple features into a single T cell product is difficult because of the transgene-packaging constraints of current gene-delivery vectors. Here we describe a cell-sorting method that leverages leucine zippers for the selective single-step immunomagnetic purification of cells co-transduced with two vectors. Such 'Zip sorting' facilitated the generation of T cells simultaneously expressing up to four CARs and coexpressing up to three 'switch' receptors. In syngeneic mouse models, T cells with multiple CARs and multiple switch receptors eliminated antigenically heterogeneous populations of leukaemia cells coexpressing multiple inhibitory ligands. By combining diverse therapeutic strategies, Zip-sorted multi-CAR multi-switch-receptor T cells can overcome multiple mechanisms of CAR T cell resistance.

Comprehensive analysis of the efficacy and safety of CAR T-cell therapy in patients with relapsed or refractory B-cell acute lymphoblastic leukaemia: a systematic review and meta-analysis

BACKGROUND

Relapse/refractory B-cell acute lymphoblastic leukaemia (r/r B-ALL) represents paediatric cancer with a challenging prognosis. CAR T-cell treatment, considered an advanced treatment, remains controversial due to high relapse rates and adverse events. This study assessed the efficacy and safety of CAR T-cell therapy for r/r B-ALL.

METHODS

The literature search was performed on four databases. Efficacy parameters included minimal residual disease negative complete remission (MRD-CR) and relapse rate (RR). Safety parameters constituted cytokine release syndrome (CRS) and immune effector cell-associated neurotoxicity syndrome (ICANS).

RESULTS

Anti-CD22 showed superior efficacy with the highest MRD-CR event rate and lowest RR, compared to anti-CD19. Combining CAR T-cell therapy with haploidentical stem cell transplantation improved RR. Safety-wise, bispecific anti-CD19/22 had the lowest CRS rate, and anti-CD22 showed the fewest ICANS. Analysis of the costimulatory receptors showed that adding CD28ζ to anti-CD19 CAR T-cell demonstrated superior efficacy in reducing relapses with favorable safety profiles.

CONCLUSION

Choosing a more efficacious and safer CAR T-cell treatment is crucial for improving overall survival in acute leukaemia. Beyond the promising anti-CD22 CAR T-cell, exploring costimulatory domains and new CD targets could enhance treatment effectiveness for r/r B-ALL.

CD28 co-stimulation: novel insights and applications in cancer immunotherapy

Substantial progress in understanding T cell signalling, particularly with respect to T cell co-receptors such as the co-stimulatory receptor CD28, has been made in recent years. This knowledge has been instrumental in the development of innovative immunotherapies for patients with cancer, including immune checkpoint blockade antibodies, adoptive cell therapies, tumour-targeted immunostimulatory antibodies, and immunostimulatory small-molecule drugs that regulate T cell activation. Following the failed clinical trial of a CD28 superagonist antibody in 2006, targeted CD28 agonism has re-emerged as a technologically viable and clinically promising strategy for cancer immunotherapy. In this Review, we explore recent insights into the molecular functions and regulation of CD28. We describe how CD28 is central to the success of current cancer immunotherapies and examine how new questions arising from studies of CD28 as a clinical target have enhanced our understanding of its biological role and may guide the development of future therapeutic strategies in oncology.

Unlocking Apoptotic Pathways: Overcoming Tumor Resistance in CAR-T-Cell Therapy

BACKGROUND

Chimeric antigen receptor (CAR)-T-cell therapy has transformed cancer treatment, leading to remarkable clinical outcomes. However, resistance continues to be a major obstacle, significantly limiting its efficacy in numerous patients.

OBJECTIVES

This review critically examines the challenges associated with CAR-T-cell therapy, with a particular focus on the role of apoptotic pathways in overcoming resistance.

METHODS

We explore various strategies to sensitize tumor cells to CAR-T-cell-mediated apoptosis, including the use of combination therapies with BH3 mimetics, Mcl-1 inhibitors, IAP inhibitors, and HDAC inhibitors. These agents inhibit anti-apoptotic proteins and activate intrinsic mitochondrial pathways, enhancing the susceptibility of tumor cells to apoptosis. Moreover, targeting the extrinsic pathway can increase the expression of death receptors on tumor cells, further promoting their apoptosis. The review also discusses the development of novel CAR constructs that enhance anti-apoptotic protein expression, such as Bcl-2, which may counteract CAR-T cell exhaustion and improve antitumor efficacy. We assess the impact of the tumor microenvironment (TME) on CAR-T cell function and propose dual-targeting CAR-T cells to simultaneously address both myeloid-derived suppressor cells (MDSCs) and tumor cells. Furthermore, we explore the potential of combining agents like PPAR inhibitors to activate the cGAS-STING pathway, thereby improving CAR-T cell infiltration into the tumor.

CONCLUSIONS

This review highlights that enhancing tumor cell sensitivity to apoptosis and increasing CAR-T cell cytotoxicity through apoptotic pathways could significantly improve therapeutic outcomes. Targeting apoptotic proteins, particularly those involved in the intrinsic mitochondrial pathway, constitutes a novel approach to overcoming resistance. The insights presented herein lay a robust foundation for future research and clinical applications aimed at optimizing CAR-T cell therapies.

Novel strategies to assess cytokine release mediated by chimeric antigen receptor T cells based on the adverse outcome pathway concept

The success of cellular immunotherapies such as chimeric antigen receptor (CAR) T cell therapy has led to their implementation as a revolutionary treatment option for cancer patients. However, the safe translation of such novel immunotherapies, from non-clinical assessment to first-in-human studies is still hampered by the lack of suitable in vitro and in vivo models recapitulating the complexity of the human immune system. Additionally, using cells derived from human healthy volunteers in such test systems may not adequately reflect the altered state of the patient's immune system thus potentially underestimating the risk of life-threatening conditions, such as cytokine release syndrome (CRS) following CAR T cell therapy. The IMI2/EU project imSAVAR (immune safety avatar: non-clinical mimicking of the immune system effects of immunomodulatory therapies) aims at creating a platform for novel tools and models for enhanced non-clinical prediction of possible adverse events associated with immunomodulatory therapies. This platform shall in the future guide early non-clinical safety assessment of novel immune therapeutics thereby also reducing the costs of their development. Therefore, we review current opportunities and challenges associated with non-clinical in vitro and in vivo models for the safety assessment of CAR T cell therapy ranging from organ-on-chip models up to advanced biomarker screening.

Co-stimulation of CD28/CD40 signaling molecule potentiates CAR-T cell efficacy and stemness

CD19 chimeric antigen receptor T (CD19CAR-T) cells have achieved promising outcomes in relapsed/refractory B cell malignancies. However, recurrences occur due to the loss of CAR-T cell persistence. We developed dual T/B cell co-stimulatory molecules (CD28 and CD40) in CAR-T cells to enhance intense tumoricidal activity and persistence. CD19.28.40z CAR-T cells promoted pNF-κB and pRelB downstream signaling while diminishing NFAT signaling upon antigen exposure. CD19.28.40z CAR-T cells demonstrated greater proliferation, which translated into effective anti-tumor cytotoxicity in long-term co-culture assay. Repetitive weekly antigen stimulation unveiled continuous CAR-T cell expansion while preserving central memory T cell subset and lower expression of exhaustion phenotypes. The intrinsic genes underlying CD19.28.40z CAR-T cell responses were compared with conventional CARs and demonstrated the up-regulated genes associated with T cell proliferation and memory as well as down-regulated genes related to apoptosis, exhaustion, and glycolysis pathway. Enrichment of genes toward T cell stemness, particularly SELL, IL-7r, TCF7, and KLF2, was observed. Effective and continuing anti-tumor cytotoxicity in vivo was exhibited in both B cell lymphoblastic leukemia and B cell non-Hodgkin lymphoma xenograft models while demonstrating persistent T cell memory signatures. The functional enhancement of CD37.28.40z CAR-T cell activities against CD37+ tumor cells was further validated. The modification of dual T/B cell signaling molecules remarkably maximized the efficacy of CAR-T cell therapy.

Molecular mechanism of co-stimulatory domains in promoting CAR-T cell anti-tumor efficacy

Chimeric antigen receptor (CAR)-engineered T cells have been defined as 'living drug'. Adding a co-stimulatory domain (CSD) has enhanced the anti-hematological effects of CAR-T cells, thereby elevating their viability for medicinal applications. Various CSDs have helped prepare CAR-T cells to study anti-tumor efficacy. Previous studies have described and summarized the anti-tumor efficacy of CAR-T cells obtained from different CSDs. However, the underlying molecular mechanisms by which different CSDs affect CAR-T function have been rarely reported. The role of CSDs in T cells has been significantly studied, but whether they can play a unique role as a part of the CAR structure remains undetermined. Here, we summarized the effects of CSDs on CAR-T signaling pathways based on the limited references and speculated the possible mechanism depending on the specific characteristics of CAR-T cells. This review will help understand the molecular mechanism of CSDs in CAR-T cells that exert different anti-tumor effects while providing potential guidance for further interventions to enhance anti-tumor efficacy in immunotherapy.

Exploring a specialized programmed-cell death patterns to predict the prognosis and sensitivity of immunotherapy in cutaneous melanoma via machine learning

The mortality and therapeutic failure in cutaneous melanoma (CM) are mainly caused by wide metastasis and chemotherapy resistance. Meanwhile, immunotherapy is considered a crucial therapy strategy for CM patients. However, the efficiency of currently available methods and biomarkers in predicting the response of immunotherapy and prognosis of CM is limited. Programmed cell death (PCD) plays a significant role in the occurrence, development, and therapy of various malignant tumors. In this research, we integrated fourteen types of PCD, multi-omics data from TCGA-SKCM and other cohorts in GEO, and clinical CM patients to develop our analysis. Based on significant PCD patterns, two PCD-related CM clusters with different prognosis, tumor microenvironment (TME), and response to immunotherapy were identified. Subsequently, seven PCD-related features, especially CD28, CYP1B1, JAK3, LAMP3, SFN, STAT4, and TRAF1, were utilized to establish the prognostic signature, namely cell death index (CDI). CDI accurately predicted the response to immunotherapy in both CM and other cancers. A nomogram with potential superior predictive ability was constructed, and potential drugs targeting CM patients with specific CDI have also been identified. Given all the above, a novel CDI gene signature was indicated to predict the prognosis and exploit precision therapeutic strategies of CM patients, providing unique opportunities for clinical intelligence and new management methods for the therapy of CM.

4-1BB-encoding CAR causes cell death via sequestration of the ubiquitin-modifying enzyme A20

CD28 and 4-1BB costimulatory endodomains included in chimeric antigen receptor (CAR) molecules play a critical role in promoting sustained antitumor activity of CAR-T cells. However, the molecular events associated with the ectopic and constitutive display of either CD28 or 4-1BB in CAR-T cells have been only partially explored. In the current study, we demonstrated that 4-1BB incorporated within the CAR leads to cell cluster formation and cell death in the forms of both apoptosis and necroptosis in the absence of CAR tonic signaling. Mechanistic studies illustrate that 4-1BB sequesters A20 to the cell membrane in a TRAF-dependent manner causing A20 functional deficiency that in turn leads to NF-κB hyperactivity, cell aggregation via ICAM-1 overexpression, and cell death including necroptosis via RIPK1/RIPK3/MLKL pathway. Genetic modulations obtained by either overexpressing A20 or releasing A20 from 4-1BB by deleting the TRAF-binding motifs of 4-1BB rescue cell cluster formation and cell death and enhance the antitumor ability of 4-1BB-costimulated CAR-T cells.

Alliance between titans: combination strategies of CAR-T cell therapy and oncolytic virus for the treatment of hematological malignancies

There have been several clinical studies using chimeric antigen receptor (CAR)-T cell therapy for different hematological malignancies. It has transformed the therapy landscape for hematologic malignancies dramatically. Nonetheless, in acute myeloid leukemia (AML) and T cell malignancies, it still has a dismal prognosis. Even in the most promising locations, recurrence with CAR-T treatment remains a big concern. Oncolytic viruses (OVs) can directly lyse tumor cells or cause immune responses, and they can be manipulated to create therapeutic proteins, increasing anticancer efficacy. Oncolytic viruses have been proven in a rising number of studies to be beneficial in hematological malignancies. There are limitations that cannot be avoided by using either treatment alone, and the combination of CAR-T cell therapy and oncolytic virus therapy may complement the disadvantages of individual application, enhance the advantages of their respective treatment methods and improve the treatment effect. The alternatives for combining two therapies in hematological malignancies are discussed in this article.

IL-18-secreting multiantigen targeting CAR T cells eliminate antigen-low myeloma in an immunocompetent mouse model

ABSTRACT

Multiple myeloma is a plasma cell malignancy that is currently incurable with conventional therapies. Following the success of CD19-targeted chimeric antigen receptor (CAR) T cells in leukemia and lymphoma, CAR T cells targeting B-cell maturation antigen (BCMA) more recently demonstrated impressive activity in relapsed and refractory myeloma patients. However, BCMA-directed therapy can fail due to weak expression of BCMA on myeloma cells, suggesting that novel approaches to better address this antigen-low disease may improve patient outcomes. We hypothesized that engineered secretion of the proinflammatory cytokine interleukin-18 (IL-18) and multiantigen targeting could improve CAR T-cell activity against BCMA-low myeloma. In a syngeneic murine model of myeloma, CAR T cells targeting the myeloma-associated antigens BCMA and B-cell activating factor receptor (BAFF-R) failed to eliminate myeloma when these antigens were weakly expressed, whereas IL-18-secreting CAR T cells targeting these antigens promoted myeloma clearance. IL-18-secreting CAR T cells developed an effector-like T-cell phenotype, promoted interferon-gamma production, reprogrammed the myeloma bone marrow microenvironment through type-I/II interferon signaling, and activated macrophages to mediate antimyeloma activity. Simultaneous targeting of weakly-expressed BCMA and BAFF-R with dual-CAR T cells enhanced T-cell:target-cell avidity, increased overall CAR signal strength, and stimulated antimyeloma activity. Dual-antigen targeting augmented CAR T-cell secretion of engineered IL-18 and facilitated elimination of larger myeloma burdens in vivo. Our results demonstrate that combination of engineered IL-18 secretion and multiantigen targeting can eliminate myeloma with weak antigen expression through distinct mechanisms.

Metabolic dialogues: regulators of chimeric antigen receptor T cell function in the tumor microenvironment

Tumor-infiltrating lymphocytes (TILs) and chimeric antigen receptor (CAR) T cells have demonstrated remarkable success in the treatment of relapsed/refractory melanoma and hematological malignancies, respectively. These treatments have marked a pivotal shift in cancer management. However, as "living drugs," their effectiveness is dependent on their ability to proliferate and persist in patients. Recent studies indicate that the mechanisms regulating these crucial functions, as well as the T cell's differentiation state, are conditioned by metabolic shifts and the distinct utilization of metabolic pathways. These metabolic shifts, conditioned by nutrient availability as well as cell surface expression of metabolite transporters, are coupled to signaling pathways and the epigenetic landscape of the cell, modulating transcriptional, translational, and post-translational profiles. In this review, we discuss the processes underlying the metabolic remodeling of activated T cells, the impact of a tumor metabolic environment on T cell function, and potential metabolic-based strategies to enhance T cell immunotherapy.

Synthetic dual co-stimulation increases the potency of HIT and TCR-targeted cell therapies

Chimeric antigen receptor T cells have dramatically improved the treatment of hematologic malignancies. T cell antigen receptor (TCR)-based cell therapies are yet to achieve comparable outcomes. Importantly, chimeric antigen receptors not only target selected antigens but also reprogram T cell functions through the co-stimulatory pathways that they engage upon antigen recognition. We show here that a fusion receptor comprising the CD80 ectodomain and the 4-1BB cytoplasmic domain, termed 80BB, acts as both a ligand and a receptor to engage the CD28 and 4-1BB pathways, thereby increasing the antitumor potency of human leukocyte antigen-independent TCR (HIT) receptor- or TCR-engineered T cells and tumor-infiltrating lymphocytes. Furthermore, 80BB serves as a switch receptor that provides agonistic 4-1BB co-stimulation upon its ligation by the inhibitory CTLA4 molecule. By combining multiple co-stimulatory features in a single antigen-agnostic synthetic receptor, 80BB is a promising tool to sustain CD3-dependent T cell responses in a wide range of targeted immunotherapies.

Endogenous CD28 drives CAR T cell responses in multiple myeloma

Recent FDA approvals of chimeric antigen receptor (CAR) T cell therapy for multiple myeloma (MM) have reshaped the therapeutic landscape for this incurable cancer. In pivotal clinical trials B cell maturation antigen (BCMA) targeted, 4-1BB co-stimulated (BBζ) CAR T cells dramatically outperformed standard-of-care chemotherapy, yet most patients experienced MM relapse within two years of therapy, underscoring the need to improve CAR T cell efficacy in MM. We set out to determine if inhibition of MM bone marrow microenvironment (BME) survival signaling could increase sensitivity to CAR T cells. In contrast to expectations, blocking the CD28 MM survival signal with abatacept (CTLA4-Ig) accelerated disease relapse following CAR T therapy in preclinical models, potentially due to blocking CD28 signaling in CAR T cells. Knockout studies confirmed that endogenous CD28 expressed on BBζ CAR T cells drove in vivo anti-MM activity. Mechanistically, CD28 reprogrammed mitochondrial metabolism to maintain redox balance and CAR T cell proliferation in the MM BME. Transient CD28 inhibition with abatacept restrained rapid BBζ CAR T cell expansion and limited inflammatory cytokines in the MM BME without significantly affecting long-term survival of treated mice. Overall, data directly demonstrate a need for CD28 signaling for sustained in vivo function of CAR T cells and indicate that transient CD28 blockade could reduce cytokine release and associated toxicities.

Preclinical evaluation of a novel CAR-T therapy utilizing a scFv antibody highly specific to MAGE-A4p230-239/HLA-A∗02:01 complex

Despite the revolutionary success of chimeric antigen receptor (CAR)-T therapy for hematological malignancies, successful CAR-T therapies for solid tumors remain limited. One major obstacle is the scarcity of tumor-specific cell-surface molecules. One potential solution to overcome this barrier is to utilize antibodies that recognize peptide/major histocompatibility complex (MHCs) in a T cell receptor (TCR)-like fashion, allowing CAR-T cells to recognize intracellular tumor antigens. This study reports a highly specific single-chain variable fragment (scFv) antibody against the MAGE-A4p230-239/human leukocyte antigen (HLA)-A∗02:01 complex (MAGE-A4 pMHC), screened from a human scFv phage display library. Indeed, retroviral vectors encoding CAR, utilizing this scFv antibody as a recognition component, efficiently recognized and lysed MAGA-A4+ tumor cells in an HLA-A∗02:01-restricted manner. Additionally, the adoptive transfer of T cells modified by the CAR-containing glucocorticoid-induced tumor necrosis factor receptor (TNFR)-related receptor (GITR) intracellular domain (ICD), but not CD28 or 4-1BB ICD, significantly suppressed the growth of MAGE-A4+ HLA-A∗02:01+ tumors in an immunocompromised mouse model. Of note, a comprehensive analysis revealed that a broad range of amino acid sequences of the MAGE-A4p230-239 peptide were critical for the recognition of MAGE-A4 pMHC by these CAR-T cells, and no cross-reactivity to analogous peptides was observed. Thus, MAGE-A4-targeted CAR-T therapy using this scFv antibody may be a promising and safe treatment for solid tumors.

Differential protein-protein interactions underlie signaling mediated by the TCR and a 4-1BB domain-containing CAR

Cells rely on activity-dependent protein-protein interactions to convey biological signals. For chimeric antigen receptor (CAR) T cells containing a 4-1BB costimulatory domain, receptor engagement is thought to stimulate the formation of protein complexes similar to those stimulated by T cell receptor (TCR)-mediated signaling, but the number and type of protein interaction-mediating binding domains differ between CARs and TCRs. Here, we performed coimmunoprecipitation mass spectrometry analysis of a second-generation, CD19-directed 4-1BB:ζ CAR (referred to as bbζCAR) and identified 128 proteins that increased their coassociation after target engagement. We compared activity-induced TCR and CAR signalosomes by quantitative multiplex coimmunoprecipitation and showed that bbζCAR engagement led to the activation of two modules of protein interactions, one similar to TCR signaling that was more weakly engaged by bbζCAR as compared with the TCR and one composed of TRAF signaling complexes that was not engaged by the TCR. Batch-to-batch and interindividual variations in production of the cytokine IL-2 correlated with differences in the magnitude of protein network activation. Future CAR T cell manufacturing protocols could measure, and eventually control, biological variation by monitoring these signalosome activation markers.

NF-κB in biology and targeted therapy: new insights and translational implications

NF-κB signaling has been discovered for nearly 40 years. Initially, NF-κB signaling was identified as a pivotal pathway in mediating inflammatory responses. However, with extensive and in-depth investigations, researchers have discovered that its role can be expanded to a variety of signaling mechanisms, biological processes, human diseases, and treatment options. In this review, we first scrutinize the research process of NF-κB signaling, and summarize the composition, activation, and regulatory mechanism of NF-κB signaling. We investigate the interaction of NF-κB signaling with other important pathways, including PI3K/AKT, MAPK, JAK-STAT, TGF-β, Wnt, Notch, Hedgehog, and TLR signaling. The physiological and pathological states of NF-κB signaling, as well as its intricate involvement in inflammation, immune regulation, and tumor microenvironment, are also explicated. Additionally, we illustrate how NF-κB signaling is involved in a variety of human diseases, including cancers, inflammatory and autoimmune diseases, cardiovascular diseases, metabolic diseases, neurological diseases, and COVID-19. Further, we discuss the therapeutic approaches targeting NF-κB signaling, including IKK inhibitors, monoclonal antibodies, proteasome inhibitors, nuclear translocation inhibitors, DNA binding inhibitors, TKIs, non-coding RNAs, immunotherapy, and CAR-T. Finally, we provide an outlook for research in the field of NF-κB signaling. We hope to present a stereoscopic, comprehensive NF-κB signaling that will inform future research and clinical practice.

Recent advances on CAR-T signaling pave the way for prolonged persistence and new modalities in clinic

Chimeric antigen receptor T-cell (CAR-T) therapy has revolutionized the treatment of hematological malignancies. The importance of the receptor costimulatory domain for long-term CAR-T cell engraftment and therapeutic efficacy was demonstrated with second-generation CAR-T cells. Fifth generation CAR-T cells are currently in preclinical trials. At the same time, the processes that orchestrate the activation and differentiation of CAR-T cells into a specific phenotype that predisposes them to long-term persistence are not fully understood. This review highlights ongoing research aimed at elucidating the role of CAR domains and T-cell signaling molecules involved in these processes.

Dual targeting of cancer metabolome and stress antigens affects transcriptomic heterogeneity and efficacy of engineered T cells

Few cancers can be targeted efficiently by engineered T cell strategies. Here, we show that γδ T cell antigen receptor (γδ TCR)-mediated cancer metabolome targeting can be combined with targeting of cancer-associated stress antigens (such as NKG2D ligands or CD277) through the addition of chimeric co-receptors. This strategy overcomes suboptimal γ9δ2 TCR engagement of αβ T cells engineered to express a defined γδ TCR (TEGs) and improves serial killing, proliferation and persistence of TEGs. In vivo, the NKG2D-CD28WT chimera enabled control only of liquid tumors, whereas the NKG2D-4-1BBCD28TM chimera prolonged persistence of TEGs and improved control of liquid and solid tumors. The CD277-targeting chimera (103-4-1BB) was the most optimal co-stimulation format, eradicating both liquid and solid tumors. Single-cell transcriptomic analysis revealed that NKG2D-4-1BBCD28TM and 103-4-1BB chimeras reprogram TEGs through NF-κB. Owing to competition with naturally expressed NKG2D in CD8+ TEGs, the NKG2D-4-1BBCD28TM chimera mainly skewed CD4+ TEGs toward adhesion, proliferation, cytotoxicity and less exhausted signatures, whereas the 103-4-1BB chimera additionally shaped the CD8+ subset toward a proliferative state.

Bispecific CD33/CD123 targeted chimeric antigen receptor T cells for the treatment of acute myeloid leukemia

CD33 and CD123 are expressed on the surface of human acute myeloid leukemia blasts and other noncancerous tissues such as hematopoietic stem cells. On-target off-tumor toxicities may limit chimeric antigen receptor T cell therapies that target both CD33 and CD123. To overcome this limitation, we developed bispecific human CD33/CD123 chimeric antigen receptor (CAR) T cells with an "AND" logic gate. We produced novel CD33 and CD123 scFvs from monoclonal antibodies that bound CD33 and CD123 and activated T cells. Screening of CD33 and CD123 CAR T cells for cytotoxicity, cytokine production, and proliferation was performed, and we selected scFvs for CD33/CD123 bispecific CARs. The bispecific CARs split 4-1BB co-stimulation on one scFv and CD3ζ on the other. In vitro testing of cytokine secretion and cytotoxicity resulted in selecting bispecific CAR 1 construct for in vivo analysis. The CD33/CD123 bispecific CAR T cells were able to control acute myeloid leukemia (AML) in a xenograft AML mouse model similar to monospecific CD33 and CD123 CAR T cells while showing no on-target off-tumor effects. Based on our findings, human CD33/CD123 bispecific CAR T cells are a promising cell-based approach to prevent AML and support clinical investigation.

Dual-inhibitory domain iCARs improve the efficiency of the AND-NOT gate CAR T strategy

CAR (chimeric antigen receptor) T cell therapy has shown clinical success in treating hematological malignancies, but its treatment of solid tumors has been limited. One major challenge is on-target, off-tumor toxicity, where CAR T cells also damage normal tissues that express the targeted antigen. To reduce this detrimental side-effect, Boolean-logic gates like AND-NOT gates have utilized an inhibitory CAR (iCAR) to specifically curb CAR T cell activity at selected nonmalignant tissue sites. However, the strategy seems inefficient, requiring high levels of iCAR and its target antigen for inhibition. Using a TROP2-targeting iCAR with a single PD1 inhibitory domain to inhibit a CEACAM5-targeting CAR (CEACAR), we observed that the inefficiency was due to a kinetic delay in iCAR inhibition of cytotoxicity. To improve iCAR efficiency, we modified three features of the iCAR-the avidity, the affinity, and the intracellular signaling domains. Increasing the avidity but not the affinity of the iCAR led to significant reductions in the delay. iCARs containing twelve different inhibitory signaling domains were screened for improved inhibition, and three domains (BTLA, LAIR-1, and SIGLEC-9) each suppressed CAR T function but did not enhance inhibitory kinetics. When inhibitory domains of LAIR-1 or SIGLEC-9 were combined with PD-1 into a single dual-inhibitory domain iCAR (DiCARs) and tested with the CEACAR, inhibition efficiency improved as evidenced by a significant reduction in the inhibitory delay. These data indicate that a delicate balance between CAR and iCAR signaling strength and kinetics must be achieved to regulate AND-NOT gate CAR T cell selectivity.

Chimeric Antigen Receptor T Cells: Immunotherapy for the Treatment of Leukemia, Lymphoma, and Myeloma

In immunotherapy with T cells genetically modified to express chimeric antigen receptors (CAR), autologous lymphocytes are extracted from the patient, genetically modified to obtain CAR-T cells, and reintroduced into the patient to attack cancer cells. The success of this therapy has been achieved in the area of CD19-positive leukemias and lymphomas, being approved for the treatment of non-Hodgkin's lymphomas, acute lymphoblastic leukemia, and multiple myeloma. CARs are proteins that combine antibody specificity with T-cell cytotoxicity. The most common toxicities associated with therapy were not predicted by preclinical testing and include cytokine release syndrome, neurotoxicity, and cytopenias. These toxicities are usually reversible. One of the main challenges facing the field is the high economic cost that therapy entails, so the search for ways to reduce this cost must be a priority. In addition, other challenges to overcome include the situation that not all patients are supplied with the product and the existence of long waiting times for the start of therapy. The aim of this review is to present the development of the structure of CAR-T cells, the therapies approved to date, the toxicity associated with them, and the advantages and limitations that they present as immunotherapy.

Context-specific synthetic T cell promoters from assembled transcriptional elements

Genetic engineering of human lymphocytes for therapeutic applications is constrained by a lack of transgene transcriptional control, resulting in a compromised therapeutic index. Incomplete understanding of transcriptional logic limits the rational design of contextually responsive genetic modules1. Here, we juxtaposed rationally curated transcriptional response element (TRE) oligonucleotides by random concatemerization to generate a library from which we selected context-specific inducible synthetic promoters (iSynPros). Through functional selection, we screened an iSynPro library for "IF-THEN" logic-gated transcriptional responses in human CD8+ T cells expressing a 4-1BB second generation chimeric antigen receptor (CAR). iSynPros exhibiting stringent off-states in quiescent T cells and CAR activation-dependent transcriptional responsiveness were cloned and subjected to TRE composition and pattern analysis, as well as performance in regulating candidate antitumor potency enhancement modules. These data reveal synthetic TRE grammar can mediate logic-gated transgene transcription in human T cells that, when applied to CAR T cell engineering, enhance potency and improve therapeutic indices.

Monitoring regulatory T cells as a prognostic marker in lung transplantation

Lung transplantation is the major surgical procedure, which restores normal lung functioning and provides years of life for patients suffering from major lung diseases. Lung transplant recipients are at high risk of primary graft dysfunction, and chronic lung allograft dysfunction (CLAD) in the form of bronchiolitis obliterative syndrome (BOS). Regulatory T cell (Treg) suppresses effector cells and clinical studies have demonstrated that Treg levels are altered in transplanted lung during BOS progression as compared to normal lung. Here, we discuss levels of Tregs/FOXP3 gene expression as a crucial prognostic biomarker of lung functions during CLAD progression in clinical lung transplant recipients. The review will also discuss Treg mediated immune tolerance, tissue repair, and therapeutic strategies for achieving in-vivo Treg expansion, which will be a potential therapeutic option to reduce inflammation-mediated graft injuries, taper the toxic side effects of ongoing immunosuppressants, and improve lung transplant survival rates.

In vitro re-challenge of CAR T cells

Chimeric antigen receptor (CAR) T cells (CAR T) have emerged as a potential therapy for cancer patients. CAR T cells are capable of recognizing membrane proteins on cancer cells which initiates a downstream signaling in T cells that ends in cancer cell death. Continuous antigen exposure over time, activation of inhibitory signaling pathways and/or chronic inflammation can lead to CAR T cell exhaustion. In this context, the design of CARs can have a great impact on the functionality of CAR T cells, on their potency and exhaustion. Here, using CD19CAR as model, we provide a re-challenge protocol where CAR T cells are cultured weekly with malignant lymphoid cell lines BL-41 and Nalm-6 to simulate them with continuous antigen pressure over a four-week period. This protocol can be value for assessing CAR T cell functionality and for the comparison of different CAR constructs.

4-1BB Targeting Immunotherapy: Mechanism, Antibodies, and Chimeric Antigen Receptor T

4-1BB (CD137, TNFRSF9) is a type I transmembrane protein which binds its natural ligand, 4-1BBL. This interaction has been exploited to improve cancer immunotherapy. With ligand binding by 4-1BB, the nuclear factor-kappa B signaling pathway is activated, which results in transcription of corresponding genes such as interleukin-2 and interferon-γ, as well as the induction of T cell proliferation and antiapoptotic signals. Moreover, monoclonal antibodies that target-4-1BB, for example, Urelumab and Utomilumab, are widely used in the treatments of B cell non-Hodgkin lymphoma, lung cancer, breast cancer, soft tissue sarcoma, and other solid tumors. Furthermore, 4-1BB as a costimulatory domain, for chimeric antigen receptor T (CAR-T) cells, improves T cell proliferation and survival as well as reduces T cell exhaustion. As such, a deeper understanding of 4-1BB will contribute to improvements in cancer immunotherapy. This review provides a comprehensive analysis of current 4-1BB studies, with a focus on the use of targeting-4-1BB antibodies and 4-1BB activation domains in CAR-T cells for the treatment of cancer.

CD137 (4-1BB) requires physically associated cIAPs for signal transduction and antitumor effects

CD137 (4-1BB) is a member of the TNFR family that mediates potent T cell costimulatory signals upon ligation by CD137L or agonist monoclonal antibodies (mAbs). CD137 agonists attain immunotherapeutic antitumor effects in cancer mouse models, and multiple agents of this kind are undergoing clinical trials. We show that cIAP1 and cIAP2 are physically associated with the CD137 signaling complex. Moreover, cIAPs are required for CD137 signaling toward the NF-κB and MAPK pathways and for costimulation of human and mouse T lymphocytes. Functional evidence was substantiated with SMAC mimetics that trigger cIAP degradation and by transfecting cIAP dominant-negative variants. Antitumor effects of agonist anti-CD137 mAbs are critically dependent on the integrity of cIAPs in cancer mouse models, and cIAPs are also required for signaling from CARs encompassing CD137's cytoplasmic tail.

Type I Interferon Signaling via the EGR2 Transcriptional Regulator Potentiates CAR T Cell-Intrinsic Dysfunction

Chimeric antigen receptor (CAR) T cell therapy has shown promise in treating hematologic cancers, but resistance is common and efficacy is limited in solid tumors. We found that CAR T cells autonomously propagate epigenetically programmed type I interferon signaling through chronic stimulation, which hampers antitumor function. EGR2 transcriptional regulator knockout not only blocks this type I interferon-mediated inhibitory program but also independently expands early memory CAR T cells with improved efficacy against liquid and solid tumors. The protective effect of EGR2 deletion in CAR T cells against chronic antigen-induced exhaustion can be overridden by interferon-β exposure, suggesting that EGR2 ablation suppresses dysfunction by inhibiting type I interferon signaling. Finally, a refined EGR2 gene signature is a biomarker for type I interferon-associated CAR T cell failure and shorter patient survival. These findings connect prolonged CAR T cell activation with deleterious immunoinflammatory signaling and point to an EGR2-type I interferon axis as a therapeutically amenable biological system.

SIGNIFICANCE

To improve CAR T cell therapy outcomes, modulating molecular determinants of CAR T cell-intrinsic resistance is crucial. Editing the gene encoding the EGR2 transcriptional regulator renders CAR T cells impervious to type I interferon pathway-induced dysfunction and improves memory differentiation, thereby addressing major barriers to progress for this emerging class of cancer immunotherapies. This article is highlighted in the In This Issue feature, p. 1501.

Allogeneic chimeric antigen receptor-T cells with CRISPR-disrupted programmed death-1 checkpoint exhibit enhanced functional fitness

BACKGROUND AIMS

Therapeutic disruption of immune checkpoints has significantly advanced the armamentarium of approaches for treating cancer. The prominent role of the programmed death-1 (PD-1)/programmed death ligand-1 axis for downregulating T cell function offers a tractable strategy for enhancing the disease-modifying impact of CAR-T cell therapy.

METHODS

To address checkpoint interference, primary human T cells were genome edited with a next-generation CRISPR-based platform (Cas9 chRDNA) by knockout of the PDCD1 gene encoding the PD-1 receptor. Site-specific insertion of a chimeric antigen receptor specific for CD19 into the T cell receptor alpha constant locus was implemented to drive cytotoxic activity.

RESULTS

These allogeneic CAR-T cells (CB-010) promoted longer survival of mice in a well-established orthotopic tumor xenograft model of a B cell malignancy compared with identically engineered CAR-T cells without a PDCD1 knockout. The persistence kinetics of CB-010 cells in hematologic tissues versus CAR-T cells without PDCD1 disruption were similar, suggesting the robust initial debulking of established tumor xenografts was due to enhanced functional fitness. By single-cell RNA-Seq analyses, CB-010 cells, when compared with identically engineered CAR-T cells without a PDCD1 knockout, exhibited fewer T_reg cells, lower exhaustion phenotypes and reduced dysfunction signatures and had higher activation, glycolytic and oxidative phosphorylation signatures. Further, an enhancement of mitochondrial metabolic fitness was observed, including increased respiratory capacity, a hallmark of less differentiated T cells.

CONCLUSIONS

Genomic PD-1 checkpoint disruption in the context of allogeneic CAR-T cell therapy may provide a compelling option for treating B lymphoid malignancies.

[Recent research on chimeric antigen receptor T cells in children with refractory/relapsed acute lymphoblastic leukemia]

At present, the treatment of refractory/relapsed acute lymphoblastic leukemia is still in a difficult situation, and even if the intensity of chemotherapy is increased or it is combined with hematopoietic stem cell transplantation, some children may have a poor prognosis and a short survival time. Chimeric antigen receptor T-cell (CAR-T) immunotherapy uses genetically engineered T cells and does not rely on the human leukocyte antigen pathway to recognize tumor-specific antigens, and then CAR-T cells bind to target antigen cells to trigger immune response, thereby exerting a sustained anti-leukemia effect. As the most rapidly developed tumor immunotherapy, major breakthroughs have been made for CAR-T cells in the treatment of various hematological tumors, but there still lacks a comprehensive system for the research, development, and production of CAR-T cells and standardized diagnosis and treatment protocols in China. This article reviews the recent research on CAR-T cells in children with refractory/relapsed acute lymphoblastic leukemia.

Costimulatory domains direct distinct fates of CAR-driven T cell dysfunction

Chimeric antigen receptor (CAR) engineered T cells often fail to enact effector functions after infusion into patients. Understanding the biological pathways that lead CAR T cells to failure is of critical importance in the design of more effective therapies. We developed and validated an in vitro model that drives T cell dysfunction through chronic CAR activation and interrogated how CAR costimulatory domains contribute to T cell failure. We found that dysfunctional CD28-based CARs targeting CD19 bear hallmarks of classical T cell exhaustion while dysfunctional 41BB-based CARs are phenotypically, transcriptionally and epigenetically distinct. We confirmed activation of this unique transcriptional program in CAR T cells that failed to control clinical disease. Further, we demonstrate that 41BB-dependent activation of the transcription factor FOXO3 is a significant contributor to this dysfunction and disruption of FOXO3 improves CAR T cell function. These findings identify that chronic activation of 41BB leads to novel state of T cell dysfunction that can be alleviated by genetic modification of FOXO3.

Summary

Chronic stimulation of CARs containing the 41BB costimulatory domain leads to a novel state of T cell dysfunction that is distinct from T cell exhaustion.

TRAF3: Guardian of T lymphocyte functions

Tumor necrosis factor receptor (TNFR)-associated factor 3 (TRAF3) is an adapter protein with many context-specific functions. Early studies of lymphocyte TRAF3 hinted at TRAF3's importance for T cell function, but elucidation of specific mechanisms was delayed by early lethality of globally TRAF3^-/- mice. Development of a conditional TRAF3-deficient mouse enabled important descriptive and mechanistic insights into how TRAF3 promotes optimal T cell function. Signaling through the T cell antigen receptor (TCR) fails to induce normal proliferation and survival in TRAF3 ^-/- T cells, and TCR-activated cells in vitro and in vivo have deficient cytokine production. These defects can be traced to incorrect localization and function of negative regulatory phosphatases acting at different parts of the signaling cascade, as can dysregulated effector responses and memory T cell homeostasis in vivo and an enlarged regulatory T cell (Treg) compartment. The important regulatory activity of TRAF3 is also evident at members of the TNFR superfamily and cytokine receptors. Here, we review significant advances in mechanistic understanding of how TRAF3 regulates T cell differentiation and function, through modulation of signaling through the TCR, costimulatory receptors, and cytokine receptors. Finally, we briefly discuss the recent identification of families carrying single allele loss-of-function mutations in TRAF3, and compare the findings in their T cells with the T cell defects identified in mice whose T cells completely lack T cell TRAF3. Together, the body of work describing TRAF3-mediated regulation of T cell effector function and differentiation frame TRAF3 as an important modulator of T cell signal integration.

Analysis of causes for poor persistence of CAR-T cell therapy in vivo

Chimeric antigen receptor T-cell (CAR-T-cell) therapy has been well researched to date because of its ability to target malignant tumor cells. The most common CAR-T cells are CD19 CAR-T cells, which play a large role in B-cell leukemia treatment. However, most CAR-T cells are associated with relapse after clinical treatment, so the quality and persistence of CAR-T cells need to be improved. With continuous optimization, there have been four generations of CARs and each generation of CARs has better quality and durability than the previous generation. In addition, it is important to increase the proportion of memory cells in CAR-T cells. Studies have shown that an immunosuppressive tumor microenvironment (TME) can lead to dysfunction of CAR-T cells, resulting in decreased cell proliferation and poor persistence. Thus, overcoming the challenges of immunosuppressive molecules and targeting cytokines in the TME can also improve CAR-T cell persistence. In this paper, we explored how to improve the durability of CAR-T cell therapy by improving the structure of CARs, increasing the proportion of memory CAR-T cells and improving the TME.

Enrichment of T-cell proliferation and memory gene signatures of CD79A/CD40 costimulatory domain potentiates CD19CAR-T cell functions

CD19 chimeric antigen receptor (CAR) T-cells have demonstrated remarkable outcomes in B-cell malignancies. Recently, the novel CD19CAR-T cells incorporated with B-cell costimulatory molecules of CD79A/CD40 demonstrated superior antitumor activity in the B-cell lymphoma model compared with CD28 or 4-1BB. Here, we investigated the intrinsic transcriptional gene underlying the functional advantage of CD19.79A.40z CAR-T cells following CD19 antigen exposure using transcriptome analysis compared to CD28 or 4-1BB. Notably, CD19.79A.40z CAR-T cells up-regulated genes involved in T-cell activation, T-cell proliferation, and NF-κB signaling, whereas down-regulated genes associated with T-cell exhaustion and apoptosis. Interestingly, CD19.79A.40z CAR- and CD19.BBz CAR-T cells were enriched in almost similar pathways. Furthermore, gene set enrichment analysis demonstrated the enrichment of genes, which were previously identified to correlate with T-cell proliferation, interferon signaling pathway, and naïve and memory T-cell signatures, and down-regulated T-cell exhaustion genes in CD79A/CD40, compared with the T-cell costimulatory domain. The CD19.79A.40z CAR-T cells also up-regulated genes related to glycolysis and fatty acid metabolism, which are necessary to drive T-cell proliferation and differentiation compared with conventional CD19CAR-T cells. Our study provides a comprehensive insight into the understanding of gene signatures that potentiates the superior antitumor functions by CD19CAR-T cells incorporated with the CD79A/CD40 costimulatory domain.

CAR-T cell therapy for hematological malignancies: Limitations and optimization strategies

In the past decade, the emergence of chimeric antigen receptor (CAR) T-cell therapy has led to a cellular immunotherapy revolution against various cancers. Although CAR-T cell therapies have demonstrated remarkable efficacy for patients with certain B cell driven hematological malignancies, further studies are required to broaden the use of CAR-T cell therapy against other hematological malignancies. Moreover, treatment failure still occurs for a significant proportion of patients. CAR antigen loss on cancer cells is one of the most common reasons for cancer relapse. Additionally, immune evasion can arise due to the hostile immunosuppressive tumor microenvironment and the impaired CAR-T cells in vivo persistence. Other than direct antitumor activity, the adverse effects associated with CAR-T cell therapy are another major concern during treatment. As a newly emerged treatment approach, numerous novel preclinical studies have proposed different strategies to enhance the efficacy and attenuate CAR-T cell associated toxicity in recent years. The major obstacles that impede promising outcomes for patients with hematological malignancies during CAR-T cell therapy have been reviewed herein, along with recent advancements being made to surmount them.

4-1BB: A promising target for cancer immunotherapy

Immunotherapy, powered by its relative efficacy and safety, has become a prominent therapeutic strategy utilized in the treatment of a wide range of diseases, including cancer. Within this class of therapeutics, there is a variety of drug types such as immune checkpoint blockade therapies, vaccines, and T cell transfer therapies that serve the purpose of harnessing the body’s immune system to combat disease. Of these different types, immune checkpoint blockades that target coinhibitory receptors, which dampen the body’s immune response, have been widely studied and established in clinic. In contrast, however, there remains room for the development and improvement of therapeutics that target costimulatory receptors and enhance the immune response against tumors, one of which being the 4-1BB (CD137/ILA/TNFRSF9) receptor. 4-1BB has been garnering attention as a promising therapeutic target in the setting of cancer, amongst other diseases, due to its broad expression profile and ability to stimulate various signaling pathways involved in the generation of a potent immune response. Since its discovery and demonstration of potential as a clinical target, major progress has been made in the knowledge of 4-1BB and the development of clinical therapeutics that target it. Thus, we seek to summarize and provide a comprehensive update and outlook on those advancements in the context of cancer and immunotherapy.

CAR-T Cell Therapy in Hematological Malignancies: Current Opportunities and Challenges

Chimeric antigen receptor T (CAR-T) cell therapy represents a major breakthrough in cancer treatment, and it has achieved unprecedented success in hematological malignancies, especially in relapsed/refractory (R/R) B cell malignancies. At present, CD19 and BCMA are the most common targets in CAR-T cell therapy, and numerous novel therapeutic targets are being explored. However, the adverse events related to CAR-T cell therapy might be serious or even life-threatening, such as cytokine release syndrome (CRS), CAR-T-cell-related encephalopathy syndrome (CRES), infections, cytopenia, and CRS-related coagulopathy. In addition, due to antigen escape, the limited CAR-T cell persistence, and immunosuppressive tumor microenvironment, a considerable proportion of patients relapse after CAR-T cell therapy. Thus, in this review, we focus on the progress and challenges of CAR-T cell therapy in hematological malignancies, such as attractive therapeutic targets, CAR-T related toxicities, and resistance to CAR-T cell therapy, and provide some practical recommendations.

Therapeutic nexus of T cell immunometabolism in improving transplantation immunotherapy

Immunometabolism is a therapeutic strategy to tune immune cells through metabolic reprogramming, which allows immune cells to be differentiated according to their energy requirements. Recent therapeutic strategies targeting immunometabolism suggest that intracellular metabolic reprogramming controls T cell activation, proliferation, and differentiation into effector (Teff) or regulatory (Treg) cells. Immunometabolism is being studied for the treatment of inflammatory diseases, including those associated with solid organ transplantation (SOT). Here, we review immunometabolic regulation of immune cells, with a particular focus on Treg metabolic regulation and liver kinase B1 (LKB1) signaling, which stabilize Tregs and prevent inflammation-associated tissue injuries. All in all, here we discussed how targeting T cell immunometabolism modulates Teff and Treg-mediated immune responses, which can be used to boost Treg differentiation, stability, and ultimately favor immunotolerance in clinical transplants.