Engineering CAR-NK cells to secrete IL-15 sustains their anti-AML functionality but is associated with systemic toxicities

IL-15 transpresentation by ovarian cancer cells improves CD34+ progenitor-derived NK cell's anti-tumor functionality

Ovarian cancer (OC) is the most lethal gynecological malignancy. As high numbers of Natural Killer (NK) cells in ascites associate with improved survival, the adoptive transfer of allogeneic NK cells is an attractive therapeutic strategy. An approach to further improve NK cell expansion and anti-tumor functionality post-infusion includes IL-15 transpresentation (transIL-15), which involves surface expression of the IL-15 cytokine bound to IL-15Rα. However, others have substantiated that systemic administration of ALT/N-803, a soluble molecule mimicking transIL-15, leads to T cell-mediated rejection of the infused allogeneic NK cell product. In addition, whether transIL-15 induce superior expansion and functionality of our hematopoietic progenitor cell-derived NK cells (HPC-NK) remains understudied. Here, we propose to transfect OC cells with IL-15 and IL-15Rα mRNA and evaluate HPC-NK cell stimulation in vitro. Co-transfection of both mRNAs resulted in surface co-expression of both components, thus mimicking the transIL-15. Importantly, co-culture of HPC-NK cells with transIL-15 OC cells resulted in superior proliferation, IFNγ production, cytotoxicity and granzyme B secretion. Furthermore, we observed uptake of IL-15Rα by HPC-NK cells when co-cultured with transIL-15 OC cells, which associates with NK cell long-term proliferation and survival. Superior killing and granzyme B secretion were also observed in transIL-15 OC spheroids. Our results demonstrate that local delivery of IL-15 and IL-15Rα mRNA to OC tumors may be a safer strategy to boost HPC-NK cell therapy of OC through IL-15 transpresentation.

CAR-NK cell therapy: promise and challenges in solid tumors

Over the past few years, cellular immunotherapy has emerged as a promising treatment for certain hematologic cancers, with various CAR-T therapies now widely used in clinical settings. However, challenges related to the production of autologous cell products and the management of CAR-T cell toxicity highlight the need for new cell therapy options that are universal, safe, and effective. Natural killer (NK) cells, which are part of the innate immune system, offer unique advantages, including the potential for off-the-shelf therapy. A recent first-in-human trial of CD19-CAR-NK infusion in patients with relapsed/refractory lymphoid malignancies demonstrated safety and promising clinical activity. Building on these positive clinical outcomes, current research focuses on enhancing CAR-NK cell potency by increasing their in vivo persistence and addressing functional exhaustion. There is also growing interest in applying the successes seen in hematologic malignancies to solid tumors. This review discusses current trends and emerging concepts in the engineering of next-generation CAR- NK therapies. It will cover the process of constructing CAR-NK cells, potential targets for their manufacturing, and their role in various solid tumors. Additionally, it will examine the mechanisms of action and the research status of CAR-NK therapies in the treatment of solid tumors, along with their advantages, limitations, and future challenges. The insights provided may guide future investigations aimed at optimizing CAR-NK therapy for a broader range of malignancies.

Unlocking the Potential of CAR-NK Cell Therapy: Overcoming Barriers and Challenges in the Treatment of Myeloid Malignancies

Myeloid malignancies include various types of cancers that arise from the abnormal development or proliferation of myeloid cells within the bone marrow. Chimeric antigen receptor (CAR) T cell treatments, which show great potential for B cell and plasma cell cancers, face major challenges when used for myeloid malignancies. CAR natural killer (NK) cell-based immunotherapy encounters several challenges in treating myeloid cancers, including (i) poor gene transfer efficiency and expansion platforms in vitro, (ii) limited proliferation and persistence in vivo, (iii) antigenic heterogeneity, and (iv) an immunosuppressive tumor microenvironment. Despite these hurdles, "off-the-shelf" CAR-NK treatments showed encouraging results, marked by enhanced proliferation, prolonged persistence, enhanced tumor infiltration, and improved adaptability. This review offers a summary of the biological traits and cellular sources of NK cells along with a discussion of contemporary CAR designs. Furthermore, it addresses the challenges observed in preclinical research and clinical trials related to CAR-NK cell therapy for myeloid cancers, suggesting enhancement strategies.

Natural killer cells: a new promising source for developing chimeric antigen receptor anti-cancer cells in hematological malignancies

In recent times, the application of CAR-T cell treatment has significantly progressed, showing auspicious treatment outcomes in hematologic malignancies. However, along with these advances, certain limitations and challenges hurdle the widespread utilization of this technology. Recently, CAR-NK cells have gained attention in cancer treatment, as this approach has an important advantage over CART therapy (i.e. no need for HLA matching) for targeting foreign cells. This review aims to explore the benefits of CAR NK cell therapy, and generation strategies, as well as the challenges and limitations hindering the application of CAR NK cells in experimental studies and trials on hematologic malignancies.

The clinical landscape of CAR NK cells

Chimeric antigen receptor (CAR) NK cell therapy has emerged as a promising alternative to CAR T cell therapy, offering significant advantages in terms of safety and versatility. Here we explore the current clinical landscape of CAR NK cells, and their application in hematologic malignancies and solid cancers, as well as their potential for treating autoimmune disorders. Our analysis draws from data collected from 120 clinical trials focused on CAR NK cells, and presents insights into the demographics and characteristics of these studies. We further outline the specific targets and diseases under investigation, along with the major cell sources, genetic modifications, combination strategies, preconditioning- and dosing regimens, and manufacturing strategies being utilized. Initial results from 16 of these clinical trials demonstrate promising efficacy of CAR NK cells, particularly in B cell malignancies, where response rates are comparable to those seen with CAR T cells but with lower rates of severe adverse effects, such as cytokine release syndrome (CRS), immune effector cell-associated neurotoxicity syndrome (ICANS), and graft-versus-host disease (GvHD). However, challenges remain in solid tumor applications, where only modest efficacy has been observed to date. Our analysis reveals that research is increasingly focused on enhancing CAR NK cell persistence, broadening their therapeutic targets, and refining manufacturing processes to improve accessibility and scalability. With recent advancements in NK cell engineering and their increased clinical applications, CAR NK cells are predicted to become an integral component of next-generation immunotherapies, not only for cancer but potentially for immune-mediated diseases as well.

Honing CAR T cells to tackle acute myeloid leukemia

ABSTRACT

Acute myeloid leukemia (AML) remains a dismal disease with poor prognosis, particularly in the relapsed/refractory (R/R) setting. Chimeric antigen receptor (CAR) therapy has yielded remarkable clinical results in other leukemias and thus has, in principle, the potential to achieve similar outcomes in R/R AML. Redirecting the approved CD19-specific CAR designs against the myeloid antigens CD33, CD123, or CLEC12A has occasionally yielded morphologic leukemia-free states but has so far been marred by threatening myeloablation and early relapses. These safety and efficacy limitations are largely due to the challenge of identifying suitable target antigens and designing adequate receptors for effective recognition and safe elimination of AML. Building on lessons learned from the initial clinical attempts, a new wave of CAR strategies relying on alternative target antigens and innovative CAR designs is about to enter clinical evaluation. Adapted multiantigen targeting, logic gating, and emerging cell engineering solutions offer new possibilities to better direct T-cell specificity and sensitivity toward AML. Pharmacologic modulation and genetic epitope engineering may extend these approaches by augmenting target expression in AML cells or minimizing target expression in normal hematopoietic cells. On/off switches or CAR T-cell depletion may curb excessive or deleterious CAR activity. Investigation of AML-intrinsic resistance and leukemic microenvironmental factors is poised to reveal additional targetable AML vulnerabilities. We summarize here the findings, challenges, and new developments of CAR therapy for AML. These illustrate the need to specifically adapt CAR strategies to the complex biology of AML to achieve better therapeutic outcomes.

Efficacy of chimeric antigen receptor engineered natural killer cells in the treatment of hematologic malignancies: a systematic review and meta-analysis of preclinical studies

BACKGROUND

Chimeric antigen receptor (CAR) engineered NK cells (CAR-NK) are a novel approach to the immunotherapy of hematologic malignancies which seeks to overcome some of the challenges faced by CAR-T cells (CAR-T). With few published clinical studies, preclinical studies can identify strategies to accelerate clinical translation. We conducted a systematic review on the preclinical in vivo use of CAR-NK for the treatment of hematologic malignancies to assess these therapies in a holistic and unbiased manner.

METHODS

Our protocol was registered with PROSPERO (ID: CRD42023438375). We performed a search of OVID MEDLINE, OVID Embase, and Embase for animal studies employing human CAR-NK cells in the treatment of hematologic malignancies. Screening of studies for eligibility criteria was performed in duplicate. Our primary outcomes were survival and reduction in tumor volume. Data extraction from individual experiments was performed by one reviewer using DigitizeitTM software and verified by a second reviewer. Meta-analysis and subgroup analyses were performed using Comprehensive Meta-AnalysisTM software. Information for descriptive outcomes was extracted in duplicate by two independent reviewers. Risk of bias was assessed using the SYRCLE Risk of Bias Tool for Animal Studies.

RESULTS

A total of 34 papers met eligibility criteria. Overall, CD19 was the most common antigen targeted however there was substantial diversity in antigenic targets, source material for generating CAR-NK cells, and NK cell modifications. Mice treated with CAR-NK therapy survived significantly longer than untreated mice (median survival ratio of 1.18, 95% CI: 1.10-1.27, P < 0.001), and mice treated with nonengineered NK cells (median survival ratio 1.13, 95% CI: 1.03-1.23, P < 0.001). Similarly, treatment with CAR-NK significantly reduced the tumor burden when compared to untreated mice (ratio of mean tumor volume 0.23, 95% CI: 0.17-0.32, P < 0.001) or mice treated with nonengineered NK cells (ratio of mean tumor volume 0.37, 95% CI: 0.28-0.51, P < 0.001). Subgroup analysis showed that cotreatment with IL-15 reduced tumor volume but did not increase survival. In general, CAR-NK cell persistence was short but was increased by IL-15.

CONCLUSIONS

CAR-NK shows promise for the treatment of hematologic malignancies in preclinical models.

Advancing Natural Killer Cell Therapy: Genetic Engineering Strategies for Enhanced Cancer Immunotherapy

Natural killer (NK) cells are pivotal innate immune system components that exhibit spontaneous cytolytic activity against abnormal cells, such as infected and tumor cells. NK cells have shown significant promise in adoptive cell therapy because of their favorable safety profiles and minimal toxicity in clinical settings. Despite their advantages, the therapeutic application of unmodified NK cells faces challenges, including limited in vivo persistence, particularly in the immunosuppressive tumor microenvironment. Recent advances in genetic engineering have enhanced the therapeutic potential of NK cells by addressing these limitations and improving their therapeutic efficacy. In this review, we have described various methodologies for the genetic modification of NK cells, including viral vectors, electroporation, and nanoparticle-based approaches. The ongoing research on nanomaterialbased approaches highlights their potential to overcome current limitations in NK cell therapy, paving the way for advanced cancer therapy and improved clinical outcomes. In this review, we also emphasize the potential of engineered NK cells in cancer immunotherapy and other clinical applications, highlighting the expanding scope of NK cell-based treatments and the critical role of innovative genetic engineering techniques.

Novel gene manipulation approaches to unlock the existing bottlenecks of CAR-NK cell therapy

Currently, CAR-T cell therapy is known as an efficacious treatment for patients with relapsed/refractory hematologic malignancies. Nonetheless, this method faces several bottlenecks, including low efficacy for solid tumors, lethal adverse effects, high cost of autologous products, and the risk of GvHD in allogeneic settings. As a potential alternative, CAR-NK cell therapy can overcome most of the limitations of CAR-T cell therapy and provide an off-the-shelf, safer, and more affordable product. Although published results from preclinical and clinical studies with CAR-NK cells are promising, several bottlenecks must be unlocked to maximize the effectiveness of CAR-NK cell therapy. These bottlenecks include low in vivo persistence, low trafficking into tumor sites, modest efficacy in solid tumors, and sensitivity to immunosuppressive tumor microenvironment. In recent years, advances in gene manipulation tools and strategies have laid the groundwork to overcome the current bottlenecks of CAR-NK cell therapy. This review will introduce the existing gene manipulation tools and discuss their advantages and disadvantages. We will also explore how these tools can enhance CAR-NK cell therapy's safety and efficacy.

Single-chain variable fragment affinity tuning can optimize anti-AML CAR-NK cell functionality

BACKGROUND

Natural Killer (NK) cells have intrinsic anticancer activity that can be redirected toward acute myeloid leukemia (AML) with chimeric antigen receptor (CAR) engineering. Here, we study the functional consequences of CAR binding affinity and targeted epitope on CAR-NK cell activation, cytolytic synapse formation, and antitumor activity.

METHODS

We characterized NK-92 and primary NK cell populations expressing variant affinity AML-specific CARs containing single-chain variable fragments (scFvs, 26292 or 7G3) targeting two epitopes on CD123. 26292 affinity variants were discovered through directed evolution of an error-prone mutagenic library, while 7G3 affinity variants were previously reported. The resulting CAR-NK cell panel was studied with in vitro binding, activation, and cytotoxicity studies and in mouse xenograft models.

RESULTS

26292 and 7G3 CARs of variable CD123 binding affinities were highly expressed in NK cells and conferred antigen-specific activation in vitro. High-resolution imaging demonstrated greater clustering of high-affinity 7G3 CAR-NK cells and consequent AML target cell death in a short-term time lapse. Low-affinity 7G3 CAR-NK cells exhibited enhanced antigen density discrimination with greater membrane-proximal signaling, cytokine production, and cytotoxicity. In longer-term assays, low-affinity 7G3 CAR-NK cells demonstrated more sustained killing of AML cells. In vivo testing highlighted greater expansion of low-affinity 7G3 CAR-NK cells in two xenograft models.

CONCLUSIONS

Expression of 26292 and 7G3 CARs with a range of CD123 binding affinities in NK cells leads to antigen-specific activation and cytotoxicity against AML. Affinity-based differences in functional activation and antitumor activity are dependent on time course and are scFv/epitope specific.

Preventing postsurgical colorectal cancer relapse: A hemostatic hydrogel loaded with METTL3 inhibitor for CAR-NK cell therapy

Colorectal cancer (CRC) recurrence post-surgery remains a major challenge. While Chimeric Antigen Receptor (CAR)-engineered natural killer (NK) cells hold immense therapeutic potential, their intratumoral infiltration ability remains limited, hampering efficacy. Building upon prior research suggesting that chemokines like C-X-C motif chemokine ligand 9 (CXCL9) and C-X-C motif chemokine ligand 10 (CXCL10) recruit CAR-NK cells, we hypothesized that tumor cell m6A methylation, regulated by Methyltransferase-like 3 (METTL3), influences chemokine secretion. This study aims to elucidate the underlying mechanisms and improve METTL3 inhibition efficiency. We designed an adhesive hemostasis hydrogel loaded with STM2457, a METTL3 inhibitor, aimed at sustained release in the acidic tumor microenvironment. In vitro, the hydrogel promoted CAR-NK cell recruitment and tumor killing via sustained METTL3 inhibition. The hydrogel's Schiff base bonds further enabled intestinal adhesion and hemostasis in an incomplete tumor resection model of CRC. Combining the hydrogel with CAR-NK cell therapy significantly reduced CRC recurrence in vivo. Overall, our study reveals the crucial role of METTL3 in CRC recurrence and proposes a promising, multimodal strategy using STM2457-loaded hydrogel and CAR-NK cells for enhanced therapeutic efficacy.

Imaging of biphasic signalosomes constructed by checkpoint receptor 2B4 in conventional and chimeric antigen receptor-T cells

A co-signaling receptor, 2B4, has dual effects in immune cells, but its actual functions in T cells remain elusive. Here, using super-resolution imaging technology with an immunological synapse model, we showed that 2B4 forms "2B4 microclusters" immediately after 2B4-CD48 binding. A lipid phosphatase, SHIP-1, subsequently combined with 2B4 to form coinhibitory signalosomes, leading to the suppression of cytokine production. An activating adapter, SLAM-associated protein (SAP), attenuated the clustering of SHIP-1 and recruited a kinase, Fyn, enhancing the Vav1 signaling pathway as costimulatory signalosomes. Furthermore, we found that a chimeric antigen receptor with a 2B4 tail (2B4-CAR) retained the original signal transduction mechanism of 2B4. With endogenous levels of SAP expression, 2B4-CAR-T cells exposed sufficient antitumor efficacy in vivo without excess cytokine production. Our results may help explain the biphasic feature of 2B4 in T cell responses from the viewpoint of the signalosome and provide a new candidate for CAR development.

Hyperleukocytosis in a neuroblastoma patient after treatment with natural killer T cells expressing a GD2-specific chimeric antigen receptor and IL-15

The ability of immune cells to expand numerically after infusion distinguishes adoptive immunotherapies from traditional drugs, providing unique therapeutic advantages as well as the potential for unmanageable toxicities. Here, we describe a case of lethal hyperleukocytosis in a patient with neuroblastoma treated on phase 1 clinical trial (NCT03294954) with autologous natural killer T cells (NKTs) expressing a GD2-specific chimeric antigen receptor and cytokine interleukin 15 (GD2-CAR.15). This patient was the first to be treated on dose level (DL) 5 and the first patient whose product was restimulated with K562-derived artificial antigen-presenting cells (aAPCs) instead of autologous peripheral blood mononuclear cells (PBMCs). 12 previously treated patients on DLs 1 through 4 did not experience significant toxicity. Our root-cause analysis revealed no genetic alterations of known clinical significance and excluded the possibility of clonal expansion due to insertional retroviral mutagenesis. We report that the use of aAPCs instead of PBMCs for CAR-NKT restimulation contributed to a hyperproliferative state associated with distinct gene expression that possibly led to explosive lymphocyte expansion and uncontrolled toxicity in the patient. These findings warrant the implementation of measures to control immune cell activation during manufacture of cell therapy products, especially those armed with transgenic cytokines.

Exploring CAR-macrophages in non-tumor diseases: Therapeutic potential beyond cancer

BACKGROUND

After significant advancements in tumor treatment, personalized cell therapy based on chimeric antigen receptors (CAR) holds promise for transforming the management of various diseases. CAR-T therapy, the first approved CAR cell therapy product, has demonstrated therapeutic potential in treating infectious diseases, autoimmune disorders, and fibrosis. CAR-macrophages (CAR-Ms) are emerging as a promising approach in CAR immune cell therapy, particularly for solid tumor treatment, highlighting the feasibility of using macrophages to eliminate pathogens and abnormal cells.

AIM OF REVIEW

This review summarizes the progress of CAR-M therapy in non-tumor diseases and discusses various CAR intracellular activation domain designs and their potential to optimize therapeutic effects by modulating interactions between cellular components in the tissue microenvironment and CAR-M. Additionally, we discuss the characteristics and advantages of CAR-M therapy compared to traditional medicine and CAR-T/NK therapy, as well as the challenges and prospects for the clinical translation of CAR-M.

KEY SCIENTIFIC CONCEPTS OF REVIEW

This review provides a comprehensive understanding of CAR-M for the treatment of non-tumor diseases, analyzes the advantages and characteristics of CAR-M therapy, and highlights the important impact of CAR intracellular domain design on therapeutic efficacy. In addition, the challenges and clinical translation prospects of developing CAR-M as a new cell therapy are discussed.

A framework integrating multiscale in-silico modeling and experimental data predicts CD33CAR-NK cytotoxicity across target cell types

Uncovering mechanisms and predicting tumor cell responses to CAR-NK cytotoxicity is essential for improving therapeutic efficacy. Currently, the complexity of these effector-target interactions and the donor-to-donor variations in NK cell receptor (NKR) repertoire require functional assays to be performed experimentally for each manufactured CAR-NK cell product and target combination. Here, we developed a computational mechanistic multiscale model which considers heterogenous expression of CARs, NKRs, adhesion receptors and their cognate ligands, signal transduction, and NK cell-target cell population kinetics. The model trained with quantitative flow cytometry and in vitro cytotoxicity data accurately predicts the short- and long-term cytotoxicity of CD33CAR-NK cells against leukemia cell lines across multiple CAR designs. Furthermore, using Pareto optimization we explored the effect of CAR proportion and NK cell signaling on the differential cytotoxicity of CD33CAR-NK cells to cancer and healthy cells. This model can be extended to predict CAR-NK cytotoxicity across many antigens and tumor targets.

Chimeric antigen receptor natural killer cell therapy: A systematic review of preclinical studies for hematologic and solid malignancies

Advancements in the field of CAR-T therapy have brought about a revolution in the treatment of numerous types of cancer in the past ten years. However, despite the remarkable success achieved thus far, certain barriers impede the widespread implementation of this therapy such as intricate manufacturing processes and treatment-associated toxicities. As an alternative, chimeric antigen receptor-engineered natural killer cell (CAR-NK) therapy presents a viable opportunity for a simpler and more cost-effective "off-the-shelf" treatment option, which is likely to result in fewer adverse reactions. A total of 71 studies were included in this review. Eligible studies were searched and reviewed from the databases of PubMed, Web of Science and Scopus. Based on data extracted from articles, we concluded that CAR-NK cell efficiency can vary considerably depending on factors such as tumor model, dosage, CAR generation and expansion method. Furthermore, investigating consequences of utilizing various constructs and generations of CAR-NK cells on their anti-tumor activity examined in this review.

The development and application of chimeric antigen receptor natural killer (CAR-NK) cells for cancer therapy: current state, challenges and emerging therapeutic advances

Immunotherapy has transformed the landscape of cancer treatment, with chimeric antigen receptor (CAR)-engineered T (CAR-T) cell therapy emerging as a front runner in addressing some hematological malignancies. Despite its considerable efficacy, the occurrence of severe adverse effects associated with CAR-T cell therapy has limited their scope and prompted the exploration of alternative therapeutic strategies. Natural killer (NK) cells, characterized by both their innate cytotoxicity and ability to lyse target cells without the constraint of peptide specificity conferred by a major histocompatibility complex (MHC), have similarly garnered attention as a viable immunotherapy. As such, another therapeutic approach has recently emerged that seeks to combine the continued success of CAR-T cell therapy with the flexibility of NK cells. Clinical trials involving CAR-engineered NK (CAR-NK) cell therapy have exhibited promising efficacy with fewer deleterious side effects. This review aims to provide a concise overview of the cellular and molecular basis of NK cell biology, facilitating a better understanding of advancements in CAR design and manufacturing. The focus is on current approaches and strategies employed in CAR-NK cell development, exploring at both preclinical and clinical settings. We will reflect upon the achievements, advantages, and challenges intrinsic to CAR-NK cell therapy. Anticipating the maturation of CAR-NK cell therapy technology, we foresee its encouraging prospects for a broader range of cancer patients and other conditions. It is our belief that this CAR-NK progress will bring us closer to making significant strides in the treatment of refractory and recurrent cancers, as well as other immune-mediated disorders.

Comprehensive snapshots of natural killer cells functions, signaling, molecular mechanisms and clinical utilization

Natural killer (NK) cells, initially identified for their rapid virus-infected and leukemia cell killing and tumor destruction, are pivotal in immunity. They exhibit multifaceted roles in cancer, viral infections, autoimmunity, pregnancy, wound healing, and more. Derived from a common lymphoid progenitor, they lack CD3, B-cell, or T-cell receptors but wield high cytotoxicity via perforin and granzymes. NK cells orchestrate immune responses, secreting inflammatory IFNγ or immunosuppressive TGFβ and IL-10. CD56dim and CD56bright NK cells execute cytotoxicity, while CD56bright cells also regulate immunity. However, beyond the CD56 dichotomy, detailed phenotypic diversity reveals many functional subsets that may not be optimal for cancer immunotherapy. In this review, we provide comprehensive and detailed snapshots of NK cells' functions and states of activation and inhibitions in cancer, autoimmunity, angiogenesis, wound healing, pregnancy and fertility, aging, and senescence mediated by complex signaling and ligand-receptor interactions, including the impact of the environment. As the use of engineered NK cells for cancer immunotherapy accelerates, often in the footsteps of T-cell-derived engineering, we examine the interactions of NK cells with other immune effectors and relevant signaling and the limitations in the tumor microenvironment, intending to understand how to enhance their cytolytic activities specifically for cancer immunotherapy.

Evolving strategies to overcome barriers in CAR-T cell therapy for acute myeloid leukemia

INTRODUCTION

Acute myeloid leukemia (AML) is a complex and heterogeneous disease characterized by an aggressive clinical course and limited efficacious treatment options in the relapsed/refractory (R/R) setting. Chimeric antigen receptor (CAR)-modified T (CAR-T) cell immunotherapy is an investigational treatment strategy for R/R AML that has shown some promise. However, obstacles to successful CAR-T cell immunotherapy for AML remain.

AREAS COVERED

In analyses of clinical trials of CAR-T cell therapy for R/R AML, complete responses without measurable residual disease have been reported, but the durability of those responses remains unclear. Significant barriers to successful CAR-T cell therapy in AML include the scarcity of suitable tumor-target antigens (TTA), inherent T cell functional deficits, and the immunoinhibitory and hostile tumor microenvironment (TME). This review will focus on these barriers to successful CAR-T cell therapy in AML, and discuss scientific advancements and evolving strategies to overcome them.

EXPERT OPINION

Achieving durable remissions in R/R AML will likely require a multifaceted approach that integrates advancements in TTA selection, enhancement of the intrinsic quality of CAR-T cells, and development of strategies to overcome inhibitory mechanisms in the AML TME.

A structural, genetic and clinical comparison of CAR-T cells and CAR-NK cells: companions or competitors?

In recent years, following the groundbreaking achievements of chimeric antigen receptor (CAR) T cell therapy in hematological cancers, and advancements in cell engineering technologies, the exploration of other immune cells has garnered significant attention. CAR-Therapy extended beyond T cells to include CAR natural killer (NK) cells and CAR-macrophages, which are firmly established in the clinical trial landscape. Less conventional immune cells are also making their way into the scene, such as CAR mucosal-associated invariant T (MAIT) cells. This progress is advancing precision medicine and facilitating the development of ready-to-use biological treatments. However, in view of the unique features of natural killer cells, adoptive NK cell immunotherapy has emerged as a universal, allogenic, "off-the shelf" therapeutic strategy. CAR-NK cytotoxic cells present targeted tumor specificity but seem to be devoid of the side effects associated with CAR-T cells. CAR-NK cells appear to be potentially promising candidates for cancer immunotherapy. However, their application is hindered by significant challenges, particularly the limited persistence of CAR-NK cells in the body, which poses a hurdle to their sustained effectiveness in treating cancer. Based upon the foregoing, this review discusses the current status and applications of both CAR-T cells and CAR-NK cells in hematological cancers, and provides a comparative analysis of the structure, genetics, and clinical outcomes between these two types of genetically modified immune cells.

Potential alternatives to αβ-T cells to prevent graft-versus-host disease (GvHD) in allogeneic chimeric antigen receptor (CAR)-based cancer immunotherapy: A comprehensive review

Currently, CAR-T cell therapy relies on an individualized manufacturing process in which patient's own T cells are infused back into patients after being engineered and expanded ex vivo. Despite the astonishing outcomes of autologous CAR-T cell therapy, this approach is endowed with several limitations and drawbacks, such as high cost and time-consuming manufacturing process. Switching the armature of CAR-T cell therapy from autologous settings to allogeneic can overcome several bottlenecks of the current approach. Nevertheless, the use of allogeneic CAR-T cells is limited by the risk of life-threatening GvHD. Thus, in recent years, developing a method to move CAR-T cell therapy to allogeneic settings without the risk of GvHD has become a hot research topic in this field. Since the alloreactivity of αβ T-cell receptor (TCR) accounts for developing GvHD, several efforts have been made to disrupt endogenous TCR of allogeneic CAR-T cells using gene editing tools to prevent GvHD. Nonetheless, the off-target activity of gene editing tools and their associated genotoxicities, as well as the negative consequences of endogenous TCR disruption, are the main concerns of using this approach. As an alternative, CAR αβ-T cells can be replaced with other types of CAR-engineered cells that are capable of recognizing and killing malignant cells through CAR while avoiding the induction of GvHD. These alternatives include T cell subsets with restricted TCR repertoire (γδ-T, iNKT, virus-specific T, double negative T cells, and MAIT cells), killer cells (NK and CIK cells), non-lymphocytic cells (neutrophils and macrophages), stem/progenitor cells, and cell-free extracellular vesicles. In this review, we discuss how these alternatives can move CAR-based immunotherapy to allogeneic settings to overcome the bottlenecks of autologous manner without the risk of GvHD. We comprehensively discuss the pros and cons of these alternatives over the traditional CAR αβ-T cells in light of their preclinical studies and clinical trials.

Regulation of CAR transgene expression to design semiautonomous CAR-T

Effective transgene expression is critical for genetically engineered cell therapy. Therefore, one of CAR-T cell therapy's critical areas of interest, both in registered products and next-generation approaches is the expression of transgenes. It turns out that various constitutive promoters used in clinical products may influence CAR-T cell antitumor effectiveness and impact the manufacturing process. Furthermore, next-generation CAR-T starts to install remotely controlled inducible promoters or even autonomous expression systems, opening new ways of priming, boosting, and increasing the safety of CAR-T. In this article, a wide range of constitutive and inducible promoters has been grouped and structured, making it possible to compare their pros and cons as well as clinical usage. Finally, logic gates based on Synthetic Notch have been elaborated, demonstrating the coupling of desired external signals with genetically engineered cellular responses.

Activation of Cell-Intrinsic Signaling in CAR-T Cells via a Chimeric IL7R Domain

Chimeric antigen receptor (CAR) T cells can effectively treat leukemias, but sustained antitumor responses can be hindered by a lack of CAR T-cell persistence. Cytotoxic effector T cells are short-lived, and establishment of CAR-T cells with memory to ensure immune surveillance is important. Memory T cells depend on cytokine support, with IL7 activation of the IL7 receptor (IL7R) being critical. However, IL7R surface expression is negatively regulated by exposure to IL7. We aimed to support CAR T-cell persistence by equipping CAR-T cells with a sustained IL7Rα signal. We engineered T cells to constitutively secrete IL7 or to express an anti-acute myeloid leukemia-targeted IL7Rα-chimeric cytokine receptor (CCR) and characterized the phenotype of these cell types. Canonical downstream signaling was activated in CCR-T cells with IL7R activation. When coexpressed with a cytotoxic CAR, functionality of both the CCR and CAR was maintained. We designed hybrid CAR-CCR and noted membrane proximity of the intracellular domains as vital for signaling. These data show cell-intrinsic cytokine support with canonical signaling, and functionality can be provided via expression of an IL7Rα domain whether independently expressed or incorporated into a cytotoxic CAR for use in anticancer therapy.

SIGNIFICANCE

To improve the phenotype of tumor-directed T-cell therapy, we show that provision of cell-intrinsic IL7R-mediated signaling is preferable to activation of cells with exogenous IL7. We engineer this signaling via independent receptor engineering and incorporation into a CAR and validate maintained antigen-specific cytotoxic activity.

CAR-NK cell therapy in AML: Current treatment, challenges, and advantage

Over the last decade, discovery of novel therapeutic method has been attention by the researchers and has changed the therapeutic perspective of hematological malignancies. Although NK cell play a pivotal role in the elimination of abnormal and cancerous cells, there are evidence that NK cell are disarm in hematological malignancy. Chimeric antigen receptor NK (CAR-NK) cell therapy, which includes the engineering of NK cells to detect tumor-specific antigens and, as a result, clear of cancerous cells, has created various clinical advantage for several human malignancies treatment. In the current review, we summarized NK cell dysfunction and CAR-NK cell based immunotherapy to treat AML patient.

Targeting cytokine and chemokine signaling pathways for cancer therapy

Cytokines are critical in regulating immune responses and cellular behavior, playing dual roles in both normal physiology and the pathology of diseases such as cancer. These molecules, including interleukins, interferons, tumor necrosis factors, chemokines, and growth factors like TGF-β, VEGF, and EGF, can promote or inhibit tumor growth, influence the tumor microenvironment, and impact the efficacy of cancer treatments. Recent advances in targeting these pathways have shown promising therapeutic potential, offering new strategies to modulate the immune system, inhibit tumor progression, and overcome resistance to conventional therapies. In this review, we summarized the current understanding and therapeutic implications of targeting cytokine and chemokine signaling pathways in cancer. By exploring the roles of these molecules in tumor biology and the immune response, we highlighted the development of novel therapeutic agents aimed at modulating these pathways to combat cancer. The review elaborated on the dual nature of cytokines as both promoters and suppressors of tumorigenesis, depending on the context, and discussed the challenges and opportunities this presents for therapeutic intervention. We also examined the latest advancements in targeted therapies, including monoclonal antibodies, bispecific antibodies, receptor inhibitors, fusion proteins, engineered cytokine variants, and their impact on tumor growth, metastasis, and the tumor microenvironment. Additionally, we evaluated the potential of combining these targeted therapies with other treatment modalities to overcome resistance and improve patient outcomes. Besides, we also focused on the ongoing research and clinical trials that are pivotal in advancing our understanding and application of cytokine- and chemokine-targeted therapies for cancer patients.

Model-guided design of microRNA-based gene circuits supports precise dosage of transgenic cargoes into diverse primary cells

To realize the potential of engineered cells in therapeutic applications, transgenes must be expressed within the window of therapeutic efficacy. Differences in copy number and other sources of extrinsic noise generate variance in transgene expression and limit the performance of synthetic gene circuits. In a therapeutic context, supraphysiological expression of transgenes can compromise engineered phenotypes and lead to toxicity. To ensure a narrow range of transgene expression, we design and characterize Compact microRNA-Mediated Attenuator of Noise and Dosage (ComMAND), a single-transcript, microRNA-based incoherent feedforward loop. We experimentally tune the ComMAND output profile, and we model the system to explore additional tuning strategies. By comparing ComMAND to two-gene implementations, we highlight the precise control afforded by the single-transcript architecture, particularly at relatively low copy numbers. We show that ComMAND tightly regulates transgene expression from lentiviruses and precisely controls expression in primary human T cells, primary rat neurons, primary mouse embryonic fibroblasts, and human induced pluripotent stem cells. Finally, ComMAND effectively sets levels of the clinically relevant transgenes FMRP1 and FXN within a narrow window. Together, ComMAND is a compact tool well-suited to precisely specify expression of therapeutic cargoes.

Evolution of natural killer cell-targeted therapy for acute myeloid leukemia

In hematologic oncology, acute myeloid leukemia (AML) presents a significant challenge due to its complex genetic landscape and resistance to conventional therapies. Despite advances in treatment, including intensive chemotherapy and hematopoietic stem cell transplantation (HSCT), the prognosis for many patients with AML remains poor. Recently, immunotherapy has emerged as a promising approach to improve outcomes by augmenting existing treatments. Natural killer (NK) cells, a subset of innate lymphoid cells, have garnered attention for their potent cytotoxic capabilities against AML cells. In this review, we discuss the role of NK cells in AML immunosurveillance, their dysregulation in patients with AML, and various therapeutic strategies leveraging NK cells in AML treatment. We explore the challenges and prospects associated with NK cell therapy, including approaches to enhance NK cell function, overcome immune evasion mechanisms, and optimize treatment efficacy. Finally, we emphasize the importance of further research to validate and refine patient-first NK cell-based immunotherapies for AML.

Efficiently targeting neuroblastoma with the combination of anti-ROR1 CAR NK cells and N-803 in vitro and in vivo in NB xenografts

The prognosis for children with recurrent and/or refractory neuroblastoma (NB) is dismal. The receptor tyrosine kinase-like orphan receptor 1 (ROR1), which is highly expressed on the surface of NB cells, provides a potential target for novel immunotherapeutics. Anti-ROR1 chimeric antigen receptor engineered ex vivo expanded peripheral blood natural killer (anti-ROR1 CAR exPBNK) cells represent this approach. N-803 is an IL-15 superagonist with enhanced biological activity. In this study, we investigated the in vitro and in vivo anti-tumor effects of anti-ROR1 CAR exPBNK cells with or without N-803 against ROR1+ NB models. Compared to mock exPBNK cells, anti-ROR1 CAR exPBNK cells had significantly enhanced cytotoxicity against ROR1+ NB cells, and N-803 further increased cytotoxicity. High-dimensional analysis revealed that N-803 enhanced Stat5 phosphorylation and Ki67 levels in both exPBNK and anti-ROR1 CAR exPBNK cells with or without NB cells. In vivo, anti-ROR1 CAR exPBNK plus N-803 significantly (p < 0.05) enhanced survival in human ROR1+ NB xenografted NSG mice compared to anti-ROR1 CAR exPBNK alone. Our results provide the rationale for further development of anti-ROR1 CAR exPBNK cells plus N-803 as a novel combination immunotherapeutic for patients with recurrent and/or refractory ROR1+ NB.

CD70-specific CAR NK cells expressing IL-15 for the treatment of CD19-negative B-cell malignancy

ABSTRACT

Chimeric antigen receptor (CAR) natural killer (NK) cells can eliminate tumors not only through the ability of the CAR molecule to recognize antigen-expressed cancer cells but also through NK-cell receptors themselves. This overcomes some of the limitations of CAR T cells, paving the way for CAR NK cells for safer and more effective off-the-shelf cellular therapy. In this study, CD70-specific (a pan-target of lymphoma) fourth-generation CAR with 4-1BB costimulatory domain and interleukin-15 (IL-15) was constructed and transduced into cord blood-derived NK cells by Baboon envelope pseudotyped lentiviral vector. CD70-CAR NK cells displayed superior cytotoxic activity in vitro and in vivo against CD19-negative B-cell lymphoma when compared with nontransduced NK cells and CD19-specific CAR NK cells. Importantly, mice that received 2 doses of CD70-CAR NK cells showed effective eradication of tumors, accompanied by increased concentration of plasma IL-15 and enhanced CAR NK cell proliferation and persistence. Our study suggests that repetitive administration-based CAR NK-cell therapy has clinical advantage compared with a single dose of CAR NK cells for the treatment of B-cell lymphoma.

Chimeric antigen receptor-immune cells against solid tumors: Structures, mechanisms, recent advances, and future developments

ABSTRACT

The advent of chimeric antigen receptor (CAR)-T cell immunotherapies has led to breakthroughs in the treatment of hematological malignancies. However, their success in treating solid tumors has been limited. CAR-natural killer (NK) cells have several advantages over CAR-T cells because NK cells can be made from pre-existing cell lines or allogeneic NK cells with a mismatched major histocompatibility complex (MHC), which means they are more likely to become an "off-the-shelf" product. Moreover, they can kill cancer cells via CAR-dependent/independent pathways and have limited toxicity. Macrophages are the most malleable immune cells in the body. These cells can efficiently infiltrate into tumors and are present in large numbers in tumor microenvironments (TMEs). Importantly, CAR-macrophages (CAR-Ms) have recently yielded exciting preclinical results in several solid tumors. Nevertheless, CAR-T, CAR-NK, and CAR-M all have their own advantages and limitations. In this review, we systematically discuss the current status, progress, and the major hurdles of CAR-T cells, CAR-NK cells, and CAR-M as they relate to five aspects: CAR structure, therapeutic mechanisms, the latest research progress, current challenges and solutions, and comparison according to the existing research in order to provide a reasonable option for treating solid tumors in the future.

Preclinical Evaluation of Off-The-Shelf PD-L1+ Human Natural Killer Cells Secreting IL15 to Treat Non-Small Cell Lung Cancer

We described previously a human natural killer (NK) cell population that upregulates PD-L1 expression upon recognizing and reacting to tumor cells or exposure to a combination of IL12, IL18, and IL15. Here, to investigate the safety and efficacy of tumor-reactive and cytokine-activated (TRACK) NK cells, human NK cells from umbilical cord blood were expanded, transduced with a retroviral vector encoding soluble (s) IL15, and further cytokine activated to induce PD-L1 expression. Our results show cryopreserved and thawed sIL15_TRACK NK cells had significantly improved cytotoxicity against non-small cell lung cancer (NSCLC) in vitro when compared with non-transduced (NT) NK cells, PD-L1+ NK cells lacking sIL15 expression (NT_TRACK NK), or NK cells expressing sIL15 without further cytokine activation (sIL15 NK cells). Intravenous injection of sIL15_TRACK NK cells into immunodeficient mice with NSCLC significantly slowed tumor growth and improved survival when compared with NT NK and sIL15 NK cells. The addition of the anti-PD-L1 atezolizumab further improved control of NSCLC growth by sIL15_TRACK NK cells in vivo. Moreover, a dose-dependent efficacy was assessed for sIL15_TRACK NK cells without observed toxicity. These experiments indicate that the administration of frozen, off-the-shelf allogeneic sIL15_TRACK NK cells is safe in preclinical models of human NSCLC and has potent antitumor activity without and with the administration of atezolizumab. A phase I clinical trial modeled after this preclinical study using sIL15_TRACK NK cells alone or with atezolizumab for relapsed or refractory NSCLC is currently underway (NCT05334329).

Identification of a Prognostic Model Based on NK Cell-Related Genes in Multiple Myeloma Using Single-Cell and Transcriptomic Data Analysis

Background

Multiple myeloma (MM), an incurable plasma cell malignancy. The significance of the relationship between natural killer (NK) cell-related genes and clinical factors in MM remains unclear.

Methods

Initially, we extracted NK cell-related genes from peripheral blood mononuclear cells (PBMC) of healthy donors and MM samples by employing single-cell transcriptome data analysis in TISCH2. Subsequently, we screened NK cell-related genes with prognostic significance through univariate Cox regression analysis and protein-protein interaction (PPI) network analysis. Following the initial analyses, we developed potential subtypes and prognostic models for MM using consensus clustering and lasso regression analysis. Additionally, we conducted a correlation analysis to explore the relationship between clinical features and risk scores. Finally, we constructed a weighted gene co-expression network analysis (WGCNA) and identified differentially expressed genes (DEGs) within the MM cohort.

Results

We discovered that 153 NK cell-related genes were significantly associated with the prognosisof MM patients (P <0.05). Patients in NK cluster A exhibited poorer survival outcomes compared to those in cluster B. Furthermore, our NK cell-related genes risk model revealed that patients with a high risk score had significantly worse prognoses (P <0.05). Patients with a high risk score were more likely to exhibit adverse clinical markers. Additionally, the nomogram based on NK cell-related genes demonstrated strong prognostic performance. The enrichment analysis indicated that immune-related pathways were significantly correlated with both the NK subtypes and the NK cell-related genes risk model. Ultimately, through the combined use of WGCNA and DEGs analysis, and by employing Venn diagrams, we determined that ITM2C is an independent prognostic marker for MM patients.

Conclusion

In this study, we developed a novel model based on NK cell-related genes to stratify the prognosis of MM patients. Notably, higher expression levels of ITM2C were associated with more favorable survival outcomes in these patients.

IL-15 as a key regulator in NK cell-mediated immunotherapy for cancer: From bench to bedside

Interleukin 15 (IL-15) has emerged as a crucial factor in the relationship between natural killer (NK) cells and immunotherapy for cancer. This review article aims to provide a comprehensive understanding of the role of IL-15 in NK cell-mediated immunotherapy. First, the key role of IL-15 signaling in NK cell immunity is discussed, highlighting its regulation of NK cell functions and antitumor properties. Furthermore, the use of IL-15 or its analogs in clinical trials as a therapeutic strategy for various cancers, including the genetic modification of NK cells to produce IL-15, has been explored. The potential of IL-15-based therapies, such as chimeric antigen receptor (CAR) T and NK cell infusion along with IL-15 in combination with checkpoint inhibitors and other treatments, has been examined. This review also addresses the challenges and advantages of incorporating IL-15 in cell-based immunotherapy. Additionally, unresolved questions regarding the detection and biological significance of the soluble IL-15/IL-15Rα complex, as well as the potential role of IL-15/IL-15Rα in human cancer and the immunological consequences of prolonged exposure to soluble IL-15 for NK cells, are discussed.

Nanobody-based CAR NK cells for possible immunotherapy of MICA+ tumors

The glycoproteins MICA and MICB are upregulated on the surface of cells undergoing stress, for instance due to (viral) infection or malignant transformation. MICA/B are the ligands for the activating receptor NKG2D, found on cytotoxic immune cells like NK cells, CD8+ T cells, and γδ T cells. Upon engagement of NKG2D, these cells are activated to eradicate the MICA/B-positive targets, assisted by the secretion of cytokines. Nanobodies, or VHHs, are derived from the variable regions of camelid heavy-chain only immunoglobulins. Nanobodies are characterized by their small size, ease of production, stability, and specificity of recognition. We generated nanobodies that recognize membrane-bound MICA with high affinity. Here, we use these nanobodies as building blocks for a chimeric antigen receptor (CAR) to establish VHH-based CAR NK cells. These anti-MICA nanobody-based CAR NK cells recognize and selectively kill MICA-positive tumor cells in vitro and in vivo. We track localization of the VHH-based CAR NK cells to MICA-positive lung metastases by immuno-positron emission tomography imaging.

Chimeric antigen receptor-natural killer cell therapy: current advancements and strategies to overcome challenges

Chimeric antigen receptor-natural killer (CAR-NK) cell therapy is a novel immunotherapy targeting cancer cells via the generation of chimeric antigen receptors on NK cells which recognize specific cancer antigens. CAR-NK cell therapy is gaining attention nowadays owing to the ability of CAR-NK cells to release potent cytotoxicity against cancer cells without side effects such as cytokine release syndrome (CRS), neurotoxicity and graft-versus-host disease (GvHD). CAR-NK cells do not require antigen priming, thus enabling them to be used as "off-the-shelf" therapy. Nonetheless, CAR-NK cell therapy still possesses several challenges in eliminating cancer cells which reside in hypoxic and immunosuppressive tumor microenvironment. Therefore, this review is envisioned to explore the current advancements and limitations of CAR-NK cell therapy as well as discuss strategies to overcome the challenges faced by CAR-NK cell therapy. This review also aims to dissect the current status of clinical trials on CAR-NK cells and future recommendations for improving the effectiveness and safety of CAR-NK cell therapy.

IL-15-secreting CAR natural killer cells directed toward the pan-cancer target CD70 eliminate both cancer cells and cancer-associated fibroblasts

BACKGROUND

It remains challenging to obtain positive outcomes with chimeric antigen receptor (CAR)-engineered cell therapies in solid malignancies, like colorectal cancer (CRC) and pancreatic ductal adenocarcinoma (PDAC). A major obstacle is the lack of targetable surface antigens that are not shared by healthy tissues. CD70 emerges as interesting target, due to its stringent expression pattern in healthy tissue and its apparent role in tumor progression in a considerable amount of malignancies. Moreover, CD70 is also expressed on cancer-associated fibroblasts (CAFs), another roadblock for treatment efficacy in CRC and PDAC. We explored the therapeutic potential of CD70 as target for CAR natural killer (NK) cell therapy in CRC, PDAC, focusing on tumor cells and CAFs, and lymphoma.

METHODS

RNA-seq data and immunohistochemical analysis of patient samples were used to explore CD70 expression in CRC and PDAC patients. In addition, CD70-targeting CAR NK cells were developed to assess cytotoxic activity against CD70+ tumor cells and CAFs, and the effect of cytokine stimulation on their efficacy was evaluated. The in vitro functionality of CD70-CAR NK cells was investigated against a panel of tumor and CAF cell lines with varying CD70 expression. Lymphoma-bearing mice were used to validate in vivo potency of CD70-CAR NK cells. Lastly, to consider patient variability, CD70-CAR NK cells were tested on patient-derived organoids containing CAFs.

RESULTS

In this study, we identified CD70 as a target for tumor cells and CAFs in CRC and PDAC patients. Functional evaluation of CD70-directed CAR NK cells indicated that IL-15 stimulation is essential to obtain effective elimination of CD70+ tumor cells and CAFs, and to improve tumor burden and survival of mice bearing CD70+ tumors. Mechanistically, IL-15 stimulation resulted in improved potency of CD70-CAR NK cells by upregulating CAR expression and increasing secretion of pro-inflammatory cytokines, in a mainly autocrine or intracellular manner.

CONCLUSIONS

We disclose CD70 as an attractive target both in hematological and solid tumors. IL-15 armored CAR NK cells act as potent effectors to eliminate these CD70+ cells. They can target both tumor cells and CAFs in patients with CRC and PDAC, and potentially other desmoplastic solid tumors.

New insights into the stemness of adoptively transferred T cells by γc family cytokines

T cell-based adoptive cell therapy (ACT) has exhibited excellent antitumoral efficacy exemplified by the clinical breakthrough of chimeric antigen receptor therapy (CAR-T) in hematologic malignancies. It relies on the pool of functional T cells to retain the developmental potential to serially kill targeted cells. However, failure in the continuous supply and persistence of functional T cells has been recognized as a critical barrier to sustainable responses. Conferring stemness on infused T cells, yielding stem cell-like memory T cells (TSCM) characterized by constant self-renewal and multilineage differentiation similar to pluripotent stem cells, is indeed necessary and promising for enhancing T cell function and sustaining antitumor immunity. Therefore, it is crucial to identify TSCM cell induction regulators and acquire more TSCM cells as resource cells during production and after infusion to improve antitumoral efficacy. Recently, four common cytokine receptor γ chain (γc) family cytokines, encompassing interleukin-2 (IL-2), IL-7, IL-15, and IL-21, have been widely used in the development of long-lived adoptively transferred TSCM in vitro. However, challenges, including their non-specific toxicities and off-target effects, have led to substantial efforts for the development of engineered versions to unleash their full potential in the induction and maintenance of T cell stemness in ACT. In this review, we summarize the roles of the four γc family cytokines in the orchestration of adoptively transferred T cell stemness, introduce their engineered versions that modulate TSCM cell formation and demonstrate the potential of their various combinations. Video Abstract.

Empowering gene delivery with protein engineering platforms

The repertoire of therapeutic proteins has been substantially augmented by molecular engineering approaches, which have seen remarkable advancement in recent years. In particular, advances in directed evolution technologies have empowered the development of custom-designed proteins with novel and disease-relevant functions. Whereas engineered proteins have typically been administered through systemic injection of the purified molecule, exciting progress in gene delivery affords the opportunity to elicit sustained production of the engineered proteins by targeted cells in the host organism. Combining developments at the leading edge of protein engineering and gene delivery has catapulted a new wave of molecular and cellular therapy approaches, which harbor great promise for personalized and precision medicine. This mini-review outlines currently used display platforms for protein evolution and describes recent examples of how the resulting engineered proteins have been incorporated into DNA- and cell-based therapeutic platforms, both in vitro and in vivo. Collectively, the strategies detailed herein provide a framework for synthesizing molecular engineering workflows with gene therapy systems for a breadth of applications in research and medicine.

CAR NK Cell Therapy for the Treatment of Metastatic Melanoma: Potential & Prospects

Melanoma is among the most lethal forms of cancer, accounting for 80% of deaths despite comprising just 5% of skin cancer cases. Treatment options remain limited due to the genetic and epigenetic mechanisms associated with melanoma heterogeneity that underlie the rapid development of secondary drug resistance. For this reason, the development of novel treatments remains paramount to the improvement of patient outcomes. Although the advent of chimeric antigen receptor-expressing T (CAR-T) cell immunotherapies has led to many clinical successes for hematological malignancies, these treatments are limited in their utility by their immune-induced side effects and a high risk of systemic toxicities. CAR natural killer (CAR-NK) cell immunotherapies are a particularly promising alternative to CAR-T cell immunotherapies, as they offer a more favorable safety profile and have the capacity for fine-tuned cytotoxic activity. In this review, the discussion of the prospects and potential of CAR-NK cell immunotherapies touches upon the clinical contexts of melanoma, the immunobiology of NK cells, the immunosuppressive barriers preventing endogenous immune cells from eliminating tumors, and the structure and design of chimeric antigen receptors, then finishes with a series of proposed design innovations that could improve the efficacy CAR-NK cell immunotherapies in future studies.

Advancing CART therapy for acute myeloid leukemia: recent breakthroughs and strategies for future development

Chimeric antigen receptor (CAR) T therapies are being developed for acute myeloid leukemia (AML) on the basis of the results obtained for other haematological malignancies and the need of new treatments for relapsed and refractory AML. The biggest challenge of CART therapy for AML is to identify a specific target antigen, since antigens expressed in AML cells are usually shared with healthy haematopoietic stem cells (HSC). The concomitant expression of the target antigen on both tumour and HSC may lead to on-target/off-tumour toxicity. In this review, we guide researchers to design, develop, and translate to the clinic CART therapies for the treatment of AML. Specifically, we describe what issues have to be considered to design these therapies; what in vitro and in vivo assays can be used to prove their efficacy and safety; and what expertise and facilities are needed to treat and manage patients at the hospital.

Adoptive NK Cell Therapy - a Beacon of Hope in Multiple Myeloma Treatment

Major advances in the treatment of multiple myeloma (MM) have been achieved by effective new agents such as proteasome inhibitors, immunomodulatory drugs, or monoclonal antibodies. Despite significant progress, MM remains still incurable and, recently, cellular immunotherapy has emerged as a promising treatment for relapsed/refractory MM. The emergence of chimeric antigen receptor (CAR) technology has transformed immunotherapy by enhancing the antitumor functions of T cells and natural killer (NK) cells, leading to effective control of hematologic malignancies. Recent advancements in gene delivery to NK cells have paved the way for the clinical application of CAR-NK cell therapy. CAR-NK cell therapy strategies have demonstrated safety, tolerability, and substantial efficacy in treating B cell malignancies in various clinical settings. However, their effectiveness in eliminating MM remains to be established. This review explores multiple approaches to enhance NK cell cytotoxicity, persistence, expansion, and manufacturing processes, and highlights the challenges and opportunities associated with CAR-NK cell therapy against MM. By shedding light on these aspects, this review aims to provide valuable insights into the potential of CAR-NK cell therapy as a promising approach for improving the treatment outcomes of MM patients.

Off-the-shelf CAR-engineered natural killer cells targeting FLT3 enhance killing of acute myeloid leukemia

The majority of patients with acute myeloid leukemia (AML) succumb to the disease or its complications, especially among older patients. Natural killer (NK) cells have been shown to have antileukemic activity in patients with AML; however, to our knowledge, primary NK cells armed with a chimeric antigen receptor (CAR) targeting antigens associated with AML as an "off-the-shelf" product for disease control have not been explored. We developed frozen, off-the-shelf allogeneic human NK cells engineered with a CAR recognizing FLT3 and secreting soluble interleukin-15 (IL-15) (FLT3 CAR_sIL-15 NK) to improve in vivo NK cell persistence and T-cell activation. FLT3 CAR_sIL-15 NK cells had higher cytotoxicity and interferon gamma secretion against FLT3+ AML cell lines when compared with activated NK cells lacking an FLT3 CAR or soluble IL-15. Frozen and thawed allogeneic FLT3 CAR_sIL-15 NK cells prolonged survival of both the MOLM-13 AML model as well as an orthotopic patient-derived xenograft AML model when compared with control NK cells. FLT3 CAR_sIL-15 NK cells showed no cytotoxicity against healthy blood mononuclear cells or hematopoietic stem cells. Collectively, our data suggest that FLT3 is an AML-associated antigen that can be targeted by frozen, allogeneic, off-the-shelf FLT3 CAR_sIL-15 NK cells that may provide a novel approach for the treatment of AML.

2B4 inhibits the apoptosis of natural killer cells through phosphorylated extracellular signal-related kinase/B-cell lymphoma 2 signal pathway

BACKGROUND AIMS

Decades after the identification of natural killer (NK) cells as potential effector cells against malignantly transformed cells, an increasing amount of research suggests that NK cells are a prospective choice of immunocytes for cancer immunotherapy in addition to T lymphocytes for cancer immunotherapy. Recent studies have led to a breakthrough in the combination of hematopoietic stem-cell transplantation with allogeneic NK cells infusion for the treatment of malignant tumors. However, the short lifespan of NK cells in patients is the major impediment, limiting their efficacy. Therefore, prolonging the survival of NK cells will promote the application of NK-cell immunotherapy. As we have known, NK cells use a "missing-self" mechanism to lyse target cells and exert their functions through a wide array of activating, co-stimulatory and inhibitory receptors. Our previous study has suggested that CD244 (2B4), one of the co-stimulatory receptors, can improve the function of chimeric antigen receptor NK cells. However, the underlying mechanism of how 2B4 engages in the function of NK cells requires further investigation. Overall, we established a feeder cell with the expression of CD48, the ligand of 2B4, to investigate the function of 2B4-CD48 axis in NK cells, and meanwhile, to explore whether the newly generated feeder cell can improve the function of ex vivo-expanded NK cells.

METHODS

First, K562 cells overexpressing 4-1BBL and membrane-bound IL-21 (mbIL-21) were constructed (K562-41BBL-mbIL-21) and were sorted to generate the single clone. These widely used feeder cells (K562-41BBL-mbIL-21) were named as Basic Feeder hereinafter. Based on the Basic feeder, CD48 was overexpressed and named as CD48 Feeder. Then, the genetically modified feeder cells were used to expand primary NK cells from peripheral blood or umbilical cord blood. In vitro experiments were performed to compare proliferation ability, cytotoxicity, survival and activation/inhibition phenotypes of NK cells stimulated via different feeder cells. K562 cells were injected into nude mice subcutaneously with tail vein injection of NK cells from different feeder system for the detection of NK in vivo persistence and function.

RESULTS

Compared with Basic Feeders, CD48 Feeders can promote the proliferation of primary NK cells from peripheral blood and umbilical cord blood and reduce NK cell apoptosis by activating the p-ERK/BCL2 pathway both in vitro and in vivo without affecting overall phenotypes. Furthermore, NK cells expanded via CD48 Feeders showed stronger anti-tumor capability and infiltration ability into the tumor microenvironment.

CONCLUSIONS

In this preclinical study, the engagement of the 2B4-CD48 axis can inhibit the apoptosis of NK cells through the p-ERK/BCL2 signal pathway, leading to an improvement in therapeutic efficiency.

IPSC-derived CAR-NK cells for cancer immunotherapy

Adoptive cell therapies (ACT) based on chimeric antigen receptor (CAR)-modified immune cells have made great progress with six CAR-T cell products approved by the U.S. FDA for hematological malignancies. Compared with CAR-T cells, CAR-NK cells have attracted increasing attention owing to their multiple killing mechanisms, higher safety profile, and broad sources. Induced pluripotent stem cell (iPSC)-derived NK (iPSC-NK) cells possess a mature phenotype and potent cytolytic activity, and can provide a homogeneous population of CAR-NK cells that can be expanded to clinical scale. Thus, iPSC-derived CAR-NK (CAR-iNK) cells could be used as a standardized and "off-the-shelf" product for cancer immunotherapy. In this review, we summarize the current status of the manufacturing techniques, genetic modification strategies, preclinical and clinical evidence of CAR-iNK cells, and discuss the challenges and future prospects of CAR-iNK cell therapy as a novel cellular immunotherapy in cancer.

Immunotherapy in hematologic malignancies: achievements, challenges and future prospects

The immune-cell origin of hematologic malignancies provides a unique avenue for the understanding of both the mechanisms of immune responsiveness and immune escape, which has accelerated the progress of immunotherapy. Several categories of immunotherapies have been developed and are being further evaluated in clinical trials for the treatment of blood cancers, including stem cell transplantation, immune checkpoint inhibitors, antigen-targeted antibodies, antibody-drug conjugates, tumor vaccines, and adoptive cell therapies. These immunotherapies have shown the potential to induce long-term remission in refractory or relapsed patients and have led to a paradigm shift in cancer treatment with great clinical success. Different immunotherapeutic approaches have their advantages but also shortcomings that need to be addressed. To provide clinicians with timely information on these revolutionary therapeutic approaches, the comprehensive review provides historical perspectives on the applications and clinical considerations of the immunotherapy. Here, we first outline the recent advances that have been made in the understanding of the various categories of immunotherapies in the treatment of hematologic malignancies. We further discuss the specific mechanisms of action, summarize the clinical trials and outcomes of immunotherapies in hematologic malignancies, as well as the adverse effects and toxicity management and then provide novel insights into challenges and future directions.

Beyond αβ T cells: NK, iNKT, and γδT cell biology in leukemic patients and potential for off-the-shelf adoptive cell therapies for AML

Acute myeloid leukemia (AML) remains an elusive disease to treat, let alone cure, even after highly intensive therapies such as stem cell transplants. Adoptive cell therapeutic strategies based on conventional alpha beta (αβ)T cells are an active area of research in myeloid neoplasms given their remarkable success in other hematologic malignancies, particularly B-cell-derived acute lymphoid leukemia, myeloma, and lymphomas. Several limitations have hindered clinical application of adoptive cell therapies in AML including lack of leukemia-specific antigens, on-target-off-leukemic toxicity, immunosuppressive microenvironments, and leukemic stem cell populations elusive to immune recognition and destruction. While there are promising T cell-based therapies including chimeric antigen receptor (CAR)-T designs under development, other cytotoxic lymphocyte cell subsets have unique phenotypes and capabilities that might be of additional benefit in AML treatment. Of particular interest are the natural killer (NK) and unconventional T cells known as invariant natural killer T (iNKT) and gamma delta (γδ) T cells. NK, iNKT, and γδT cells exhibit intrinsic anti-malignant properties, potential for alloreactivity, and human leukocyte-antigen (HLA)-independent function. Here we review the biology of each of these unconventional cytotoxic lymphocyte cell types and compare and contrast their strengths and limitations as the basis for adoptive cell therapies for AML.

Chimeric antigen receptor engineered natural killer cells for cancer therapy

Natural killer (NK) cells, a unique component of the innate immune system, are inherent killers of stressed and transformed cells. Based on their potent capacity to kill cancer cells and good tolerance of healthy cells, NK cells have been successfully employed in adoptive cell therapy to treat cancer patients. In recent years, the clinical success of chimeric antigen receptor (CAR)-T cells has proven the vast potential of gene-manipulated immune cells as the main force to fight cancer. Following the lessons learned from mature gene-transfer technologies and advanced strategies in CAR-T therapy, NK cells have been rapidly explored as a promising candidate for CAR-based therapy. An exponentially growing number of studies have employed multiple sources of CAR-NK cells to target a wide range of cancer-related antigens, showing remarkable outcomes and encouraging safety profiles. Clinical trials of CAR-NK cells have also shown their impressive therapeutic efficacy in the treatment of hematological tumors, but CAR-NK cell therapy for solid tumors is still in the initial stages. In this review, we present the favorable profile of NK cells as a potential platform for CAR-based engineering and then summarize the outcomes and strategies of CAR-NK therapies in up-to-date preclinical and clinical investigations. Finally, we evaluate the challenges remaining in CAR-NK therapy and describe existing strategies that can assist us in devising future prospective solutions.

Principles and current clinical landscape of NK cell engaging bispecific antibody against cancer

Monoclonal antibody-based targeted therapies have greatly improved treatment options for patients by binding to the innate immune system. However, the long-term efficacy of such antibodies is limited by mechanisms of drug resistance. Over the last 50 years, with advances in protein engineering technology, more and more bispecific antibody (bsAb) platforms have been engineered to meet diverse clinical needs. Bispecific NK cell engagers (BiKEs) or tri-specific NK cell engagers (TriKEs) allow for direct targeting of immune cells to tumors, and therefore resistance and serious adverse effects are greatly reduced. Many preclinical and clinical trials are currently underway, depicting the promise of antibody-based natural killer cell engager therapeutics. In this review, we compile worldwide efforts to explore the involvement of NK cells in bispecific antibodies. With a particular emphasis on lessons learned, we focus on preclinical and clinical studies in malignancies and discuss the reasons for the limited success of NK-cell engagers against solid tumors, offering plausible new ideas for curing some advanced cancers shortly.

Cell Reprogramming Techniques: Contributions to Cancer Therapy

The reprogramming of terminally differentiated cells over the past few years has become important for induced pluripotent stem cells (iPSCs) in the field of regenerative medicine and disease drug modeling. At the same time, iPSCs have also played an important role in human cancer research. iPSCs derived from cancer patients can be used to simulate the early progression of cancer, for drug testing, and to study the molecular mechanism of cancer occurrence. In recent years, with the application of cellular immunotherapy in cancer therapy, patient-derived iPSC-induced immune cells (T, natural killer, and macrophage cells) solve the problem of immune rejection and have higher immunogenicity, which greatly improves the therapeutic efficiency of immune cell therapy. With the continuous progress of cancer differentiation therapy, iPSC technology can reprogram cancer cells to a more primitive pluripotent undifferentiated state, and successfully reverse cancer cells to a benign phenotype by changing the epigenetic inheritance of cancer cells. This article reviews the recent progress of cell reprogramming technology in human cancer research, focuses on the application of reprogramming technology in cancer immunotherapy and the problems solved, and summarizes the malignant phenotype changes of cancer cells in the process of reprogramming and subsequent differentiation.

Current status and future perspective of natural killer cell therapy for cancer

Natural killer (NK) cells possess innate abilities to effectively eliminate cancer cells. However, because of difficulties of proliferation and easy to be induced dysfunction in the setting of cancer post NK cell therapy, the curative effect of NK cell infusion has been constrained and not been widely applicable in clinical practice. The rapid development of biotechnology has promoted the development of NK cell therapy for cancer treatment. In this review, we will provide a comprehensive analysis of the current status and future prospects of NK cell therapy for cancer, focusing on the biological characteristics of NK cells, as well as strategies to enhance their targeting capabilities and overcome tumor immune suppression within the microenvironment.