Design and analysis of stably integrated reporters for inducible transgene expression in human T cells and CAR NK-cell lines

Engineered CD4 T cells for in vivo delivery of therapeutic proteins

The CD4 T cell, when engineered with a chimeric antigen receptor (CAR) containing specific intracellular domains, has been transformed into a zero-order drug-delivery platform. This introduces the capability of prolonged, disease-specific engineered protein biologics production, at the disease site. Experimental findings demonstrate that CD4 T cells offer a solution when modified with a CAR that includes 4-1BB but excludes CD28 intracellular domain. In this configuration, they achieve ~3X transduction efficiency of CD8 T cells, ~2X expansion rates, generating ~5X more biologic, and exhibit minimal cytolytic activity. Cumulatively, this addresses two main hurdles in the translation of cell-based drug delivery: scaling the production of engineered T cell ex vivo and generating sufficient biologics in vivo. When programmed to induce IFNβ upon engaging the target antigen, the CD4 T cells outperforms CD8 T cells, effectively suppressing cancer cell growth in vitro and in vivo. In summary, this platform enables precise targeting of disease sites with engineered protein-based therapeutics while minimizing healthy tissue exposure. Leveraging CD4 T cells' persistence could enhance disease management by reducing drug administration frequency, addressing critical challenges in cell-based therapy.

Chimeric antigen receptor-based natural killer cell immunotherapy in cancer: from bench to bedside

Immunotherapy has rapidly evolved in the past decades in the battle against cancer. Chimeric antigen receptor (CAR)-engineered T cells have demonstrated significant success in certain hematologic malignancies, although they still face certain limitations, including high costs and toxic effects. Natural killer cells (NK cells), as a vital component of the immune system, serve as the "first responders" in the context of cancer development. In this literature review, we provide an updated understanding of NK cell development, functions, and their applications in disease therapy. Furthermore, we explore the rationale for utilizing engineered NK cell therapies, such as CAR-NK cells, and discuss the differences between CAR-T and CAR-NK cells. We also provide insights into the key elements and strategies involved in CAR design for engineered NK cells. In addition, we highlight the challenges currently encountered and discuss the future directions in NK cell research and utilization, including pre-clinical investigations and ongoing clinical trials. Based on the outstanding antitumor potential of NK cells, it is highly likely that they will lead to groundbreaking advancements in cancer treatment in the future.

Expression of inducible factors reprograms CAR-T cells for enhanced function and safety

Despite the success of CAR-T cell cancer immunotherapy, challenges in efficacy and safety remain. Investigators have begun to enhance CAR-T cells with the expression of accessory molecules to address these challenges. Current systems rely on constitutive transgene expression or multiple viral vectors, resulting in unregulated response and product heterogeneity. Here, we develop a genetic platform that combines autonomous antigen-induced production of an accessory molecule with constitutive CAR expression in a single lentiviral vector called Uni-Vect. The broad therapeutic application of Uni-Vect is demonstrated in vivo by activation-dependent expression of (1) an immunostimulatory cytokine that improves efficacy, (2) an antibody that ameliorates cytokine-release syndrome, and (3) transcription factors that modulate T cell biology. Uni-Vect is also implemented as a platform to characterize immune receptors. Overall, we demonstrate that Uni-Vect provides a foundation for a more clinically actionable next-generation cellular immunotherapy.

Controlling Cell Trafficking: Addressing Failures in CAR T and NK Cell Therapy of Solid Tumours

The precision guiding of endogenous or adoptively transferred lymphocytes to the solid tumour mass is obligatory for optimal anti-tumour effects and will improve patient safety. The recognition and elimination of the tumour is best achieved when anti-tumour lymphocytes are proximal to the malignant cells. For example, the regional secretion of soluble factors, cytotoxic granules, and cell-surface molecule interactions are required for the death of tumour cells and the suppression of neovasculature formation, tumour-associated suppressor, or stromal cells. The resistance of individual tumour cell clones to cellular therapy and the hostile environment of the solid tumours is a major challenge to adoptive cell therapy. We review the strategies that could be useful to overcoming insufficient immune cell migration to the tumour cell mass. We argue that existing 'competitive' approaches should now be revisited as complementary approaches to improve CAR T and NK cell therapy.

NK Cells Armed with Chimeric Antigen Receptors (CAR): Roadblocks to Successful Development

In recent years, cell-based immunotherapies have demonstrated promising results in the treatment of cancer. Chimeric antigen receptors (CARs) arm effector cells with a weapon for targeting tumor antigens, licensing engineered cells to recognize and kill cancer cells. The quality of the CAR-antigen interaction strongly depends on the selected tumor antigen and its expression density on cancer cells. CD19 CAR-engineered T cells approved by the Food and Drug Administration have been most frequently applied in the treatment of hematological malignancies. Clinical challenges in their application primarily include cytokine release syndrome, neurological symptoms, severe inflammatory responses, and/or other off-target effects most likely mediated by cytotoxic T cells. As a consequence, there remains a significant medical need for more potent technology platforms leveraging cell-based approaches with enhanced safety profiles. A promising population that has been advanced is the natural killer (NK) cell, which can also be engineered with CARs. NK cells which belong to the innate arm of the immune system recognize and kill virally infected cells as well as (stressed) cancer cells in a major histocompatibility complex I independent manner. NK cells play an important role in the host’s immune defense against cancer due to their specialized lytic mechanisms which include death receptor (i.e., Fas)/death receptor ligand (i.e., Fas ligand) and granzyme B/perforin-mediated apoptosis, and antibody-dependent cellular cytotoxicity, as well as their immunoregulatory potential via cytokine/chemokine release. To develop and implement a highly effective CAR NK cell-based therapy with low side effects, the following three principles which are specifically addressed in this review have to be considered: unique target selection, well-designed CAR, and optimized gene delivery.

Generation of an NFκB-Driven Alpharetroviral "All-in-One" Vector Construct as a Potent Tool for CAR NK Cell Therapy

Immune cell therapeutics are increasingly applied in oncology. Especially chimeric antigen receptor (CAR) T cells are successfully used to treat several B cell malignancies. Efforts to engineer CAR T cells for improved activity against solid tumors include co-delivery of pro-inflammatory cytokines in addition to CARs, via either constitutive cytokine expression or inducible cytokine expression triggered by CAR recognition of its target antigen-so-called "T cells redirected for universal cytokine-mediated killing" (TRUCKs) or fourth-generation CARs. Here, we tested the hypothesis that TRUCK principles could be expanded to improve anticancer functions of NK cells. A comparison of the functionality of inducible promoters responsive to NFAT or NFκB in NK cells showed that, in contrast to T cells, the inclusion of NFκB-responsive elements within the inducible promoter construct was essential for CAR-inducible expression of the transgene. We demonstrated that GD2CAR-specific activation induced a tight NFκB-promoter-driven cytokine release in NK-92 and primary NK cells together with an enhanced cytotoxic capacity against GD2⁺ target cells, also shown by increased secretion of cytolytic cytokines. The data demonstrate biologically relevant differences between T and NK cells that are important when clinically translating the TRUCK concept to NK cells for the treatment of solid malignancies.

Preclinical studies of chimeric antigen receptor-modified natural killer cells in cancer immunotherapy: a review

INTRODUCTION

As one of the most efficacious methods of cancer immunotherapy, chimeric antigen receptor-modified immune cells have recently drawn enormous attention. After the great success achieved with CAR-T-cells in cancer treatment both in preclinical setting and in the clinic, other types of immune cells, including natural killer (NK)-cells and macrophages, have been evaluated for their anti-cancer effects along with their potential superiority against CAR-T-cells, especially in terms of safety. First introduced by Tran et al. almost 26 years ago, CAR-NK-cells are now being considered as efficient immunotherapeutic modalities in various types of cancers, not only in preclinical setting but also in numerous phase I and II clinical studies.

AREAS COVERED

In this review, we aim to provide a comprehensive survey of the preclinical studies on CAR-NK-cells' development, with an evolutional approach on CAR structures and their associated signaling moieties. Current NK-cell sources and modes of gene transfer are also reviewed.

EXPERT OPINION

CAR-NK-cells have appeared as safe and effective immunotherapeutic tools in preclinical settings; however, designing CAR structures with an eye on their specific biology, along with choosing the optimal cell source and gene transfer method require further investigation to support clinical studies.

Profiling pharmacokinetics of double-negative T cells and cytokines via a single intravenous administration in NSG mice

This study was intended to delineate the profile of double-negative T cells (DNTs) in NOD.Cg-Prkdcscid Il2rgtm1wj /SzJ mice and cytokines released from DNTs in vivo and in vitro. Total 4 × 107 cells of RC1012 injection per mice were intravenously infused. IFN-γ, TNF-α, IL-1β, IL-2, IL-4, IL-6, IL-10 were measured in vivo and in vitro. A quantitative polymerase chain reaction (PCR) was employed to determine the gene copies of Notch2-NLA per DNT cell from collected organs. Cytokines were significantly increased in vitro (4 h) and in vivo (3 h). DNT cells were distributed into the lung, liver, heart, and kidney earlier, and redistributed to lymphocyte homing spleen and bone marrow, which seemed to frame a two-compartment pharmacokinetics (PK) model but more data are needed to confirm this, and the clearance of DNT cells fell into first-order kinetics.

Chimeric antigen receptor natural killer (CAR-NK) cell design and engineering for cancer therapy

Due to their efficient recognition and lysis of malignant cells, natural killer (NK) cells are considered as specialized immune cells that can be genetically modified to obtain capable effector cells for adoptive cellular treatment of cancer patients. However, biological and technical hurdles related to gene delivery into NK cells have dramatically restrained progress. Recent technological advancements, including improved cell expansion techniques, chimeric antigen receptors (CAR), CRISPR/Cas9 gene editing and enhanced viral transduction and electroporation, have endowed comprehensive generation and characterization of genetically modified NK cells. These promising developments assist scientists and physicians to design better applications of NK cells in clinical therapy. Notably, redirecting NK cells using CARs holds important promise for cancer immunotherapy. Various preclinical and a limited number of clinical studies using CAR-NK cells show promising results: efficient elimination of target cells without side effects, such as cytokine release syndrome and neurotoxicity which are seen in CAR-T therapies. In this review, we focus on the details of CAR-NK technology, including the design of efficient and safe CAR constructs and associated NK cell engineering techniques: the vehicles to deliver the CAR-containing transgene, detection methods for CARs, as well as NK cell sources and NK cell expansion. We summarize the current CAR-NK cell literature and include valuable lessons learned from the CAR-T cell field. This review also provides an outlook on how these approaches may transform current clinical products and protocols for cancer treatment.

Synthetic promoters to induce immune-effectors into the tumor microenvironment

Harnessing the immune-system to eradicate cancer is becoming a reality in recent years. Engineered immune cells, such as chimeric antigen receptor (CAR) T cells, are facing the danger of an overt life-threatening immune response due to the ON-target OFF-tumor cytotoxicity and Cytokine Release Syndrome. We therefore developed synthetic promoters for regulation of gene expression under the control of inflammation and Hypoxia-induced signals that are associated with the tumor microenvironment (TME). We termed this methodology as chimeric-antigen-receptor-tumor-induced-vector (CARTIV). For proof of concept, we studied synthetic promoters based on promoter-responsive elements (PREs) of IFNγ, TNFα and hypoxia; triple PRE-based CARTIV promoter manifested a synergistic activity in cell-lines and potent activation in human primary T-cells. CARTIV platform can improve safety of CAR T-cells or other engineered immune-cells, providing TME-focused activity and opening a therapeutic window for many tumor-associated antigens that are also expressed by non-tumor healthy tissues.

Toward Tightly Tuned Gene Expression Following Lentiviral Vector Transduction

Lentiviral vectors are versatile tools for gene delivery purposes. While in the earlier versions of retroviral vectors, transgene expression was controlled by the long terminal repeats (LTRs), the latter generations of vectors, including those derived from lentiviruses, incorporate internal constitutive or regulated promoters in order to regulate transgene expression. This allows to temporally and/or quantitatively control transgene expression, which is required for many applications such as for clinical applications, when transgene expression is required in specific tissues and at a specific timing. Here we review the main systems that have been developed for transgene regulated expression following lentiviral gene transfer. First, the induction of gene expression can be triggered either by external or by internal cues. Indeed, these regulated vector systems may harbor promoters inducible by exogenous stimuli, such as small molecules (e.g., antibiotics) or temperature variations, offering the possibility to tune rapidly transgene expression in case of adverse events. Second, expression can be indirectly adjusted by playing on inserted sequence copies, for instance by gene excision. Finally, synthetic networks can be developed to sense specific endogenous signals and trigger defined responses after information processing. Regulatable lentiviral vectors (LV)-mediated transgene expression systems have been widely used in basic research to uncover gene functions or to temporally reprogram cells. Clinical applications are also under development to induce therapeutic molecule secretion or to implement safety switches. Such regulatable approaches are currently focusing much attention and will benefit from the development of other technologies in order to launch autonomously controlled systems.

shp-2 gene knockout upregulates CAR-driven cytotoxicity of YT NK cells

In Russia, cancer is the second leading cause of death following cardiovascular diseases. Adoptive transfer of NK cells is a promising approach to fight cancer; however, for their successful use in cancer treatment, it is necessary to ensure their robust accumulation at tumor foci, provide resistance to the immunosuppressive tumor microenvironment, and to engineer them with higher cytotoxic activity. NK lymphocytes are known to kill cancer cells expressing a number of stress ligands; and the balance of signals from inhibitory and activating receptors on the surface of the NK cell determines whether a cytotoxic reaction is triggered. We hypothesized that stronger cytotoxicity of NK cells could be achieved via gene editing aimed at enhancing the activating signaling cascades and/or weakening the inhibitory ones, thereby shifting the balance of signals towards NK cell activation and target cell lysis. Here, we took advantage of the CRISPR/Cas9 system to introduce mutations in the coding sequence of the shp-2 (PTPN11) gene encoding the signaling molecule of inhibitory pathways in NK cells. These shp-2 knock-out NK cells were additionally transduced to express a chimeric antigen receptor (CAR) that selectively recognized the antigen of interest on the target cell surface and generated an activating signal. We demonstrate that the combination of shp-2 gene knockout and CAR expression increases the cytotoxicity of effector NK-like YT cells against human prostate cancer cell line Du-145 with ectopic expression of PSMA protein, which is specifically targeted by the CAR.

Design and Characterization of an "All-in-One" Lentiviral Vector System Combining Constitutive Anti-GD2 CAR Expression and Inducible Cytokines

Genetically modified T cells expressing chimeric antigen receptors (CARs) so far have mostly failed in the treatment of solid tumors owing to a number of limitations, including an immunosuppressive tumor microenvironment and insufficient CAR T cell activation and persistence. Next-generation approaches using CAR T cells that secrete transgenic immunomodulatory cytokines upon CAR signaling, known as TRUCKs (“T cells redirected for universal cytokine-mediated killing”), are currently being explored. As TRUCKs were engineered by the transduction of T cells with two separate vectors, we developed a lentiviral modular “all-in-one” vector system that combines constitutive CAR expression and inducible nuclear factor of activated T cells (NFAT)-driven transgene expression for more efficient production of TRUCKs. Activation of the G_D2-specific CAR via GD2⁺ target cells induced NFAT promoter-driven cytokine release in primary human T cells, and indicated a tight linkage of CAR-specific activation and transgene expression that was further improved by a modified NFATsyn promoter. As proof-of-concept, we showed that T cells containing the “all-in-one” vector system secrete the immunomodulatory cytokines interleukin (IL)12 or IL18 upon co-cultivation with primary human GD2⁺ tumor cells, resulting in enhanced effector cell properties and increased monocyte recruitment. This highlights the potential of our system to simplify application of TRUCK-modified T cells in solid tumor therapy.