NKG2D CAR T-cell therapy inhibits the growth of NKG2D ligand heterogeneous tumors

Recent progress in chimeric antigen receptor therapy for acute myeloid leukemia

Although CAR-T cell therapy has been particularly successful as a treatment for B cell malignancies, effectively treating acute myeloid leukemia with CAR remains a greater challenge. Multiple preclinical studies and clinical trials are underway, including on AML-related surface markers that CAR-T cells can target, such as CD123, CD33, NKG2D, CLL1, CD7, FLT3, Lewis Y and CD70, all of which provide opportunities for developing CAR-T therapies with improved specificity and efficacy. We also explored specific strategies for CAR-T cell treatment of AML, including immune checkpoints, suicide genes, dual targeting, genomic tools and the potential for universal CAR. In addition, CAR-T cell therapy for AML still has certain risks and challenges, including cytokine release syndrome (CRS) and haematotoxicity. Despite these challenges, as a new targeting method for AML treatment, CAR-T cell therapy still has great prospects. Ongoing research aims to further optimize this treatment mode.

shRNA-mediated gene silencing of HDAC11 empowers CAR-T cells against prostate cancer

Epigenetic mechanisms are involved in several cellular functions, and their role in the immune system is of prime importance. Histone deacetylases (HDACs) are an important set of enzymes that regulate and catalyze the deacetylation process. HDACs have been proven beneficial targets for improving the efficacy of immunotherapies. HDAC11 is an enzyme involved in the negative regulation of T cell functions. Here, we investigated the potential of HDAC11 downregulation using RNA interference in CAR-T cells to improve immunotherapeutic outcomes against prostate cancer. We designed and tested four distinct short hairpin RNA (shRNA) sequences targeting HDAC11 to identify the most effective one for subsequent analyses. HDAC11-deficient CAR-T cells (shD-NKG2D-CAR-T) displayed better cytotoxicity than wild-type CAR-T cells against prostate cancer cell lines. This effect was attributed to enhanced activation, degranulation, and cytokine release ability of shD-NKG2D-CAR-T when co-cultured with prostate cancer cell lines. Our findings reveal that HDAC11 interference significantly enhances CAR-T cell proliferation, diminishes exhaustion markers PD-1 and TIM3, and promotes the formation of T central memory TCM populations. Further exploration into the underlying molecular mechanisms reveals increased expression of transcription factor Eomes, providing insight into the regulation of CAR-T cell differentiation. Finally, the shD-NKG2D-CAR-T cells provided efficient tumor control leading to improved survival of tumor-bearing mice in vivo as compared to their wild-type counterparts. The current study highlights the potential of HDAC11 downregulation in improving CAR-T cell therapy. The study will pave the way for further investigations focused on understanding and exploiting epigenetic mechanisms for immunotherapeutic outcomes.

Novel and multiple targets for chimeric antigen receptor-based therapies in lymphoma

Chimeric antigen receptor (CAR) T-cell therapy targeting CD19 in B-cell non-Hodgkin lymphoma (NHL) validates the utility of CAR-based therapy for lymphomatous malignancies. Despite the success, treatment failure due to CD19 antigen loss, mutation, or down-regulation remains the main obstacle to cure. On-target, off-tumor effect of CD19-CAR T leads to side effects such as prolonged B-cell aplasia, limiting the application of therapy in indolent diseases such as chronic lymphocytic leukemia (CLL). Alternative CAR targets and multi-specific CAR are potential solutions to improving cellular therapy outcomes in B-NHL. For Hodgkin lymphoma and T-cell lymphoma, several cell surface antigens have been studied as CAR targets, some of which already showed promising results in clinical trials. Some antigens are expressed by different lymphomas and could be used for designing tumor-agnostic CAR. Here, we reviewed the antigens that have been studied for novel CAR-based therapies, as well as CARs designed to target two or more antigens in the treatment of lymphoma.

Role of Immune Cells and Immunotherapy in Multiple Myeloma

The clinical signs of multiple myeloma, a plasma cell (PC) dyscrasia, include bone loss, renal damage, and paraproteinemia. It can be defined as the uncontrolled growth of malignant PCs within the bone marrow. The distinctive bone marrow milieu that regulates the progression of myeloma disease involves interactions between plasma and stromal cells, and myeloid and lymphoid cells. These cells affect the immune system independently or because of a complicated web of interconnections, which promotes disease development and immune evasion. Due to the importance of these factors in the onset of disease, various therapeutic strategies have been created that either target or improve the immunological processes that influence disease progression. The immune system has a role in the mechanism of action of multiple myeloma treatments. The main contributions of immune cells to the bone marrow microenvironment, as well as how they interact and how immune regulation might lead to therapeutic effects, are covered in this study.

CAR-T cell immunotherapy for ovarian cancer: hushing the silent killer

As the most lethal gynecologic oncological indication, carcinoma of the ovary has been ranked as the 5th cause of cancer-related mortality in women, with a high percentage of the patients being diagnosed at late stages of the disease and a five-year survival of ~ 30%. Ovarian cancer patients conventionally undergo surgery for tumor removal followed by platinum- or taxane-based chemotherapy; however, a high percentage of patients experience tumor relapse. Cancer immunotherapy has been regarded as a silver lining in the treatment of patients with various immunological or oncological indications; however, mirvetuximab soravtansine (a folate receptor α-specific mAb) and bevacizumab (a VEGF-A-specific mAb) are the only immunotherapeutics approved for the treatment of ovarian cancer patients. Chimeric antigen receptor T-cell (CAR-T) therapy has achieved tremendous clinical success in the treatment of patients with certain B-cell lymphomas and leukemias, as well as multiple myeloma. In the context of solid tumors, CAR-T therapies face serious obstacles that limit their therapeutic benefit. Such hindrances include the immunosuppressive nature of solid tumors, impaired tumor infiltration, lack of qualified tumor-associated antigens, and compromised stimulation and persistence of CAR-Ts following administration. Over the past years, researchers have made arduous attempts to apply CAR-T therapy to ovarian cancer. In this review, we outline the principles of CAR-T therapy and then highlight its limitations in the context of solid tumors. Ultimately, we focus on preclinical and clinical findings achieved in CAR-T-mediated targeting of different ovarian cancer-associated target antigens.

Chimeric Antigen Receptor T Cells in Acute Myeloid Leukemia

Up to 30% of patients with acute myeloid leukemia (AML) who undergo chimeric antigen receptor (CAR) T-cell therapy have evidence of response, although trials are highly heterogeneous. These responses are rarely deep or durable. CD123, CD33, and CLL-1 have emerged as the most common targets for CAR T cells in AML. CAR T cells against myeloid antigens cause myeloablation as well as cytokine release syndrome, although neurotoxicity is rarely seen. Future efforts should focus on AML-specific antigen discovery or engineering, and on further enhancing the activity of CAR T cells.

CAR-T-Cell Therapy in Multiple Myeloma: B-Cell Maturation Antigen (BCMA) and Beyond

Significant progress has been achieved in the realm of therapeutic interventions for multiple myeloma (MM), leading to transformative shifts in its clinical management. While conventional modalities such as surgery, radiotherapy, and chemotherapy have improved the clinical outcomes, the overarching challenge of effecting a comprehensive cure for patients afflicted with relapsed and refractory MM (RRMM) endures. Notably, adoptive cellular therapy, especially chimeric antigen receptor T-cell (CAR-T) therapy, has exhibited efficacy in patients with refractory or resistant B-cell malignancies and is now also being tested in patients with MM. Within this context, the B-cell maturation antigen (BCMA) has emerged as a promising candidate for CAR-T-cell antigen targeting in MM. Alternative targets include SLAMF7, CD38, CD19, the signaling lymphocyte activation molecule CS1, NKG2D, and CD138. Numerous clinical studies have demonstrated the clinical efficacy of these CAR-T-cell therapies, although longitudinal follow-up reveals some degree of antigenic escape. The widespread implementation of CAR-T-cell therapy is encumbered by several barriers, including antigenic evasion, uneven intratumoral infiltration in solid cancers, cytokine release syndrome, neurotoxicity, logistical implementation, and financial burden. This article provides an overview of CAR-T-cell therapy in MM and the utilization of BCMA as the target antigen, as well as an overview of other potential target moieties.

Acute myeloid leukemia: from NGS, through scRNA-seq, to CAR-T. dissect cancer heterogeneity and tailor the treatment

Acute myeloid leukemia (AML) is a malignant blood cancer with marked cellular heterogeneity due to altered maturation and differentiation of myeloid blasts, the possible causes of which are transcriptional or epigenetic alterations, impaired apoptosis, and excessive cell proliferation. This neoplasm has a high rate of resistance to anticancer therapies and thus a high risk of relapse and mortality because of both the biological diversity of the patient and intratumoral heterogeneity due to the acquisition of new somatic changes. For more than 40 years, the old gold standard "one size fits all" treatment approach included intensive chemotherapy treatment with anthracyclines and cytarabine.The manuscript first traces the evolution of the understanding of the pathology from the 1970s to the present. The enormous strides made in its categorization prove to be crucial for risk stratification, enabling an increasingly personalized diagnosis and treatment approach.Subsequently, we highlight how, over the past 15 years, technological advances enabling single cell RNA sequencing and T-cell modification based on the genomic tools are affecting the classification and treatment of AML. At the dawn of the new millennium, the advent of high-throughput next-generation sequencing technologies has enabled the profiling of patients evidencing different facets of the same disease, stratifying risk, and identifying new possible therapeutic targets that have subsequently been validated. Currently, the possibility of investigating tumor heterogeneity at the single cell level, profiling the tumor at the time of diagnosis or after treatments exist. This would allow the identification of underrepresented cellular subclones or clones resistant to therapeutic approaches and thus responsible for post-treatment relapse that would otherwise be difficult to detect with bulk investigations on the tumor biopsy. Single-cell investigation will then allow even greater personalization of therapy to the genetic and transcriptional profile of the tumor, saving valuable time and dangerous side effects. The era of personalized medicine will take a huge step forward through the disclosure of each individual piece of the complex puzzle that is cancer pathology, to implement a "tailored" therapeutic approach based also on engineered CAR-T cells.

CAR-T Cells in the Treatment of Ovarian Cancer: A Promising Cell Therapy

Ovarian cancer (OC) is among the most common gynecologic malignancies with a poor prognosis and a high mortality rate. Most patients are diagnosed at an advanced stage (stage III or IV), with 5-year survival rates ranging from 25% to 47% worldwide. Surgical resection and first-line chemotherapy are the main treatment modalities for OC. However, patients usually relapse within a few years of initial treatment due to resistance to chemotherapy. Cell-based therapies, particularly adoptive T-cell therapy and chimeric antigen receptor T (CAR-T) cell therapy, represent an alternative immunotherapy approach with great potential for hematologic malignancies. However, the use of CAR-T-cell therapy for the treatment of OC is still associated with several difficulties. In this review, we comprehensively discuss recent innovations in CAR-T-cell engineering to improve clinical efficacy, as well as strategies to overcome the limitations of CAR-T-cell therapy in OC.

Interleukin-15 and chemokine ligand 19 enhance cytotoxic effects of chimeric antigen receptor T cells using zebrafish xenograft model of gastric cancer

Chimeric antigen receptor (CAR) T cells have been proven effective for the treatment of B-cell-mediated malignancies. Currently, the development of efficient tools that supply CAR T cells for the treatment of other malignancies would have great impact. In this study, interleukin (IL)-15 and C-C motif chemokine ligand 19 (CCL19) were introduced into natural killer group 2D (NKG2D)-based CARs to generate 15×19 CAR T cells, which remarkably increased T-cell expansion and promoted the production of central memory T (T_cm) cells. 15×19 CAR T cells showed greater cytotoxicity to gastric cell lines than conventional CAR T cells and produced higher levels of IL-15 and CCL-19, which resulted in increased responder T cell chemotaxis and reduced expression of T cell exhaustion markers. A live zebrafish model was used for single-cell visualization of local cytotoxicity and metastatic cancers. Administration of 15×19 CAR T cells resulted in significant shrinking of gastric cancer xenograft tumors and expansion of 15×19 CAR T cells in zebrafish models. Taken together, these findings demonstrate that 15×19 CAR T cells are highly efficient in killing gastric cancer cells, are effective to avoid off-target effects, and migrate to local and metastatic sites for long-term surveillance of cancers.

The antigen-binding moiety in the driver's seat of CARs

Immuno-oncology has been at the forefront of cancer treatment in recent decades. In particular immune checkpoint and chimeric antigen receptor (CAR)-T cell therapy have achieved spectacular results. Over the years, CAR-T cell development has followed a steady evolutionary path, focusing on increasing T cell potency and sustainability, which has given rise to different CAR generations. However, there was less focus on the mode of interaction between the CAR-T cell and the cancer cell; more specifically on the targeting moiety used in the CAR and its specific properties. Recently, the importance of optimizing this domain has been recognized and the possibilities have been exploited. Over the last 10 years-in addition to the classical scFv-based CARs-single domain CARs, natural receptor-ligand CARs, universal CARs and CARs targeting more than one antigen have emerged. In addition, the specific parameters of the targeting domain and their influence on T cell activation are being examined. In this review, we concisely present the history of CAR-T cell therapy, and then expand on various developments in the CAR ectodomain. We discuss different formats, each with their own advantages and disadvantages, as well as the developments in affinity tuning, avidity effects, epitope location, and influence of the extracellular spacer.

Targeted Therapy in Pediatric AML: An Evolving Landscape

The outcomes associated with pediatric acute myeloid leukemia (AML) have improved over the last few decades, with the implementation of intensive chemotherapy, hematopoietic stem cell transplant, and improved supportive care. However, even with intensive therapy and the use of HSCT, both of which carry significant risks of short- and long-term side effects, approximately 30% of children are not able to be cured. The characterization of AML in pediatrics has evolved over time and it currently involves use of a variety of diagnostic tools, including flow cytometry and comprehensive genomic sequencing. Given the adverse effects of chemotherapy and the need for additional therapeutic options to improve outcomes in these patients, the genomic and molecular architecture is being utilized to inform selection of targeted therapies in pediatric AML. This review provides a summary of current, targeted therapy options in pediatric AML.

Novel CAR T therapy is a ray of hope in the treatment of seriously ill AML patients

Acute myeloid leukemia (AML) is a serious, life-threatening, and hardly curable hematological malignancy that affects the myeloid cell progenies and challenges patients of all ages but mostly occurs in adults. Although several therapies are available including chemotherapy, allogeneic hematopoietic stem cell transplantation (alloHSCT), and receptor-antagonist drugs, the 5-year survival of patients is quietly disappointing, less than 30%. alloHSCT is the major curative approach for AML with promising results but the treatment has severe adverse effects such as graft-versus-host disease (GVHD). Therefore, as an alternative, more efficient and less harmful immunotherapy-based approaches such as the adoptive transferring T cell therapy are in development for the treatment of AML. As such, chimeric antigen receptor (CAR) T cells are engineered T cells which have been developed in recent years as a breakthrough in cancer therapy. Interestingly, CAR T cells are effective against both solid tumors and hematological cancers such as AML. Gradually, CAR T cell therapy found its way into cancer therapy and was widely used for the treatment of hematologic malignancies with successful results particularly with somewhat better results in hematological cancer in comparison to solid tumors. The AML is generally fatal, therapy-resistant, and sometimes refractory disease with a disappointing low survival rate and weak prognosis. The 5-year survival rate for AML is only about 30%. However, the survival rate seems to be age-dependent. Novel CAR T cell therapy is a light at the end of the tunnel. The CD19 is an important target antigen in AML and lymphoma and the CAR T cells are engineered to target the CD19. In addition, a lot of research goes on the discovery of novel target antigens with therapeutic efficacy and utilizable for generating CAR T cells against various types of cancers. In recent years, many pieces of research on screening and identification of novel AML antigen targets with the goal of generation of effective anti-cancer CAR T cells have led to new therapies with strong cytotoxicity against cancerous cells and impressive clinical outcomes. Also, more recently, an improved version of CAR T cells which were called modified or smartly reprogrammed CAR T cells has been designed with less unwelcome effects, less toxicity against normal cells, more safety, more specificity, longer persistence, and proliferation capability. The purpose of this review is to discuss and explain the most recent advances in CAR T cell-based therapies targeting AML antigens and review the results of preclinical and clinical trials. Moreover, we will criticize the clinical challenges, side effects, and the different strategies for CAR T cell therapy.

NKG2D-CAR-transduced natural killer cells efficiently target multiple myeloma

CAR-T-cell therapy against MM currently shows promising results, but usually with serious toxicities. CAR-NK cells may exert less toxicity when redirected against resistant myeloma cells. CARs can be designed through the use of receptors, such as NKG2D, which recognizes a wide range of ligands to provide broad target specificity. Here, we test this approach by analyzing the antitumor activity of activated and expanded NK cells (NKAE) and CD45RA- T cells from MM patients that were engineered to express an NKG2D-based CAR. NKAE cells were cultured with irradiated Clone9.mbIL21 cells. Then, cells were transduced with an NKG2D-4-1BB-CD3z-CAR. CAR-NKAE cells exhibited no evidence of genetic abnormalities. Although memory T cells were more stably transduced, CAR-NKAE cells exhibited greater in vitro cytotoxicity against MM cells, while showing minimal activity against healthy cells. In vivo, CAR-NKAE cells mediated highly efficient abrogation of MM growth, and 25% of the treated mice remained disease free. Overall, these results demonstrate that it is feasible to modify autologous NKAE cells from MM patients to safely express a NKG2D-CAR. Additionally, autologous CAR-NKAE cells display enhanced antimyeloma activity demonstrating that they could be an effective strategy against MM supporting the development of NKG2D-CAR-NK-cell therapy for MM.

Leveraging NKG2D Ligands in Immuno-Oncology

Immune checkpoint inhibitors (ICI) revolutionized the field of immuno-oncology and opened new avenues towards the development of novel assets to achieve durable immune control of cancer. Yet, the presence of tumor immune evasion mechanisms represents a challenge for the development of efficient treatment options. Therefore, combination therapies are taking the center of the stage in immuno-oncology. Such combination therapies should boost anti-tumor immune responses and/or target tumor immune escape mechanisms, especially those created by major players in the tumor microenvironment (TME) such as tumor-associated macrophages (TAM). Natural killer (NK) cells were recently positioned at the forefront of many immunotherapy strategies, and several new approaches are being designed to fully exploit NK cell antitumor potential. One of the most relevant NK cell-activating receptors is NKG2D, a receptor that recognizes 8 different NKG2D ligands (NKG2DL), including MICA and MICB. MICA and MICB are poorly expressed on normal cells but become upregulated on the surface of damaged, transformed or infected cells as a result of post-transcriptional or post-translational mechanisms and intracellular pathways. Their engagement of NKG2D triggers NK cell effector functions. Also, MICA/B are polymorphic and such polymorphism affects functional responses through regulation of their cell-surface expression, intracellular trafficking, shedding of soluble immunosuppressive isoforms, or the affinity of NKG2D interaction. Although immunotherapeutic approaches that target the NKG2D-NKG2DL axis are under investigation, several tumor immune escape mechanisms account for reduced cell surface expression of NKG2DL and contribute to tumor immune escape. Also, NKG2DL polymorphism determines functional NKG2D-dependent responses, thus representing an additional challenge for leveraging NKG2DL in immuno-oncology. In this review, we discuss strategies to boost MICA/B expression and/or inhibit their shedding and propose that combination strategies that target MICA/B with antibodies and strategies aimed at promoting their upregulation on tumor cells or at reprograming TAM into pro-inflammatory macrophages and remodeling of the TME, emerge as frontrunners in immuno-oncology because they may unleash the antitumor effector functions of NK cells and cytotoxic CD8 T cells (CTL). Pursuing several of these pipelines might lead to innovative modalities of immunotherapy for the treatment of a wide range of cancer patients.

CAR-T cells: Early successes in blood cancer and challenges in solid tumors

New approaches to cancer immunotherapy have been developed, showing the ability to harness the immune system to treat and eliminate cancer. For many solid tumors, therapy with checkpoint inhibitors has shown promise. For hematologic malignancies, adoptive and engineered cell therapies are being widely developed, using cells such as T lymphocytes, as well as natural killer (NK) cells, dendritic cells, and potentially others. Among these adoptive cell therapies, the most active and advanced therapy involves chimeric antigen receptor (CAR)-T cells, which are T cells in which a chimeric antigen receptor is used to redirect specificity and allow T cell recognition, activation and killing of cancers, such as leukemia and lymphoma. Two autologous CAR-T products have been approved by several health authorities, starting with the U.S. Food and Drug Administration (FDA) in 2017. These products have shown powerful, inducing, long-lasting effects against B cell cancers in many cases. In distinction to the results seen in hematologic malignancies, the field of using CAR-T products against solid tumors is in its infancy. Targeting solid tumors and trafficking CAR-T cells into an immunosuppressive microenvironment are both significant challenges. The goal of this review is to summarize some of the most recent aspects of CAR-T cell design and manufacturing that have led to successes in hematological malignancies, allowing the reader to appreciate the barriers that must be overcome to extend CAR-T therapies to solid tumors successfully.

CAR-T Cell Therapy for Acute Myeloid Leukemia: Preclinical Rationale, Current Clinical Progress, and Barriers to Success

Chimeric antigen receptor (CAR)-T cell therapy has shown impressive results in chemorefractory B cell malignancies, raising the possibilities of using this immunotherapeutic modality for other devastating hematologic malignancies, such as acute myeloid leukemia (AML). AML is an aggressive hematologic malignancy which, like B cell malignancies, poses several challenges for clinical translation of successful immunotherapy. The antigenic heterogeneity of AML results in a list of potential targets that CAR-T cells could be directed towards, each with advantages and disadvantages. In this review, we provide an up-to-date report of outcomes and adverse effects from published and presented clinical trials of CAR-T cell therapy for AML and provide the preclinical rationale underlying these studies and antigen selection. Comparison across trials is difficult, yet themes emerge with respect to appropriate antigen selection and association of adverse effects with outcomes. We highlight currently active clinical trials and the potential improvements and caveats with these novel approaches. Key hurdles to the successful introduction of CAR-T cell therapy for the treatment of AML include the effect of antigenic heterogeneity and trade-offs between therapy specificity and sensitivity; on-target off-tumor toxicities; the AML tumor microenvironment; and practical considerations for future trials that should be addressed to enable successful CAR-T cell therapy for AML.

Convergent Evolution by Cancer and Viruses in Evading the NKG2D Immune Response

The natural killer group 2 member D (NKG2D) receptor and its family of NKG2D ligands (NKG2DLs) are key components in the innate immune system, triggering NK, γδ and CD8+ T cell-mediated immune responses. While surface NKG2DL are rarely found on healthy cells, expression is significantly increased in response to various types of cellular stress, viral infection, and tumour cell transformation. In order to evade immune-mediated cytotoxicity, both pathogenic viruses and cancer cells have evolved various mechanisms of subverting immune defences and preventing NKG2DL expression. Comparisons of the mechanisms employed following virus infection or malignant transformation reveal a pattern of converging evolution at many of the key regulatory steps involved in NKG2DL expression and subsequent immune responses. Exploring ways to target these shared steps in virus- and cancer-mediated immune evasion may provide new mechanistic insights and therapeutic opportunities, for example, using oncolytic virotherapy to re-engage the innate immune system towards cancer cells.

Chimeric Antigen Receptor T Cells Targeting NKG2D-Ligands Show Robust Efficacy Against Acute Myeloid Leukemia and T-Cell Acute Lymphoblastic Leukemia

CAR T cell approaches to effectively target AML and T-ALL without off-tumor effects on healthy myeloid or T cell compartments respectively are an unmet medical need. NKG2D-ligands are a promising target given their absence on healthy cells and surface expression in a wide range of malignancies. NKG2D-ligand expression has been reported in a substantial group of patients with AML along with evidence for prognostic significance. However, reports regarding the prevalence and density of NKG2D-ligand expression in AML vary and detailed studies to define whether low level expression is sufficient to trigger NKG2D-ligand directed CART cell responses are lacking. NKG2D ligand expression in T-ALL has not previously been interrogated. Here we report that NKG2D-ligands are expressed in T-ALL cell lines and primary T-ALL. We confirm that NKG2D-ligands are frequently surface expressed in primary AML, albeit at relatively low levels. Utilizing CAR T cells incorporating the natural immune receptor NKG2D as the antigen binding domain, we demonstrate striking in vitro activity of CAR T cells targeting NKG2D-ligands against AML and T-ALL cell lines and show that even low-level ligand expression in primary AML targets results in robust NKG2D-CAR activity. We found that NKG2D-ligand expression can be selectively enhanced in low-expressing AML cell lines and primary AML blasts via pharmacologic HDAC inhibition. Such pharmacologic NKG2D-ligand induction results in enhanced NKG2D-CAR anti-leukemic activity without affecting healthy PBMC, thereby providing rationale for the combination of HDAC-inhibitors with NKG2D-CAR T cell therapy as a potential strategy to achieve clinical NKG2D-CAR T cell efficacy in AML.

SJI 2020 special issue: A catalogue of Ovarian Cancer targets for CAR therapy

Ovarian Cancer (OC) is currently difficult to cure, mainly due to its late detection and the advanced state of the disease at the time of diagnosis. Therefore, conventional treatments such as debulking surgery and combination chemotherapy are rarely able to control progression of the tumour, and relapses are frequent. Alternative therapies are currently being evaluated, including immunotherapy and advanced T cell-based therapy. In the present review, we will focus on a description of those Chimeric Antigen Receptors (CARs) that have been validated in the laboratory or are being tested in the clinic. Numerous target antigens have been defined due to the identification of OC biomarkers, and many are being used as CAR targets. We provide an exhaustive list of these constructs and their current status. Despite being innovative and efficient, the OC-specific CARs face a barrier to their clinical efficacy: the tumour microenvironment (TME). Indeed, effector cells expressing CARs have been shown to be severely inhibited, rendering the CAR T cells useless once at the tumour site. Herein, we give a thorough description of the highly immunosuppressive OC TME and present recent studies and innovations that have enabled CAR T cells to counteract this negative environment and to destroy tumours.

Engineering of chimeric natural killer cell receptors to develop precision adoptive immunotherapies for cancer

Natural killer (NK) cells are innate immune effectors which play a crucial role in recognizing and eliminating virally infected and cancerous cells. They effectively distinguish between healthy and distressed self through the integration of signals delivered by germline‐encoded activating and inhibitory cell surface receptors. The frequent up‐regulation of stress markers on genetically unstable cancer cells has prompted the development of novel immunotherapies that exploit such innate receptors. One prominent example entails the development of chimeric antigen receptors (CAR) that detect cell surface ligands bound by NK receptors, coupling this engagement to the delivery of tailored immune activating signals. Here, we review strategies to engineer CARs in which specificity is conferred by natural killer group 2D (NKG2D) or other NK receptor types. Multiple preclinical studies have demonstrated the remarkable ability of chimeric NK receptor‐targeted T cells and NK cells to effectively and specifically eliminate cancer cells and to reject established tumour burdens. Importantly, such systems act not only acutely but, in some cases, they also incite immunological memory. Moreover, CARs targeted with the NKG2D ligand binding domain have also been shown to disrupt the tumour microenvironment, through the targeting of suppressive T regulatory cells, myeloid‐derived suppressor cells and tumour vasculature. Collectively, these findings have led to the initiation of early‐phase clinical trials evaluating both autologous and allogeneic NKG2D‐targeted CAR T cells in the haematological and solid tumour settings.

Experimental treatment of colorectal cancer in mice with human T cells electroporated with NKG2D RNA CAR

Aim: Peritoneal metastasis is often present in end-stage neoplastic diseases, including recurrent colorectal cancer and is associated with decreased overall survival. Novel methods are needed. Materials & methods: We constructed first-, second- and third-generation chimeric antigen receptors (CARs) specific for NKG2D ligands and modified human T cells with mRNA electroporation. Results: NKG2D CAR expression was detectable for at least 6 days postelectroporation and mediated efficient cytotoxicity against NKG2DL+ tumor cells, but not NKG2DL-cells. Multiple infusions of the first-generation CAR-T cells into immunodeficient mice bearing established peritoneal colorectal xenografts led to significantly reduced tumor burden. Conclusion: mRNA CAR is an economical way to test new CARs and potentiates controlling on-target/off-tumor toxicity and cytokine storms. The use of NKG2D RNA CARs to treat colorectal peritoneal metastasis warrants further investigation.

Electroporation of NKG2D RNA CAR Improves Vγ9Vδ2 T Cell Responses against Human Solid Tumor Xenografts

Vγ9Vδ2 T cell-based anticancer immunotherapy has shown some promise in early-phase clinical trials but there is still large room for improvement. Using the extracellular domain of the human NKG2D, a stimulatory receptor expressed by Vγ9Vδ2 T cells, we constructed NKG2D ligand-specific chimeric antigen receptors (CARs). We adopted a non-viral CAR approach via mRNA electroporation to modify Vγ9Vδ2 T cells and demonstrated that, upon interaction with the NKG2D ligand-positive cancer cells, the CARs substantially enhanced the cytotoxic activity of the modified cells toward multiple cultured solid tumor cell lines, including those resistant to Zometa treatment. Repeated doses of the CAR-expressing cells resulted in tumor regression in mice with established tumors, extending median survival time by up to 132% as compared to the PBS control group. The findings suggest clinical potential for RNA CAR-modified Vγ9Vδ2 T cells to treat a wide variety of NKG2D ligand-expressing cancers.

Bispecific NKG2D-CD3 and NKG2D-CD16 fusion proteins for induction of NK and T cell reactivity against acute myeloid leukemia

Background

Monoclonal antibodies (mAbs) mediate their effects in great part by inducing ADCC of NK cells, and multiple efforts aim to increase this function by engineering mAbs optimized Fc-parts. Even more potent antitumor immunity can be induced by strategies to stimulate T cells with their profoundly higher effector potential. However, upon increased immunostimulatory potential, the necessity to target highly tumor-specific antigens becomes critically important to reduce side effects.

Methods

We here report on bispecific fusion proteins (BFP) that target ligands of the immunoreceptor NKG2D (NKG2DL), which are widely expressed on malignant cells but generally absent on healthy tissue. They consist of the extracellular domain of NKG2D as targeting moiety fused to Fab-fragments of CD3 (NKG2D-CD3) or CD16 (NKG2D-CD16) antibodies.

Results

NKG2D-CD16 displayed increased affinity to the FcγRIII on NK cells compared to engineered Fc-parts, which are contained in optimized mAbs that presently undergo clinical evaluation. In line, NKG2D-CD16 induced superior activation, degranulation, IFN-γ production and lysis of acute myeloid leukemia (AML) cell lines and patient AML cells. NKG2D-CD3 in turn potently stimulated T cells, and comparison of efficacy over time revealed that NKG2D-CD16 was superior upon short term application, while NKG2D-CD3 mediated overall more potent effects which manifested after longer times. This can be attributed to treatment-induced proliferation of T cells but not NK cells.

Conclusions

Taken together, we here introduce novel “antibody-like” BFP that take advantage of the highly tumor-restricted expression of NKG2DL and potently activate the reactivity of NK cells or T cells for immunotherapy of AML.

Electronic supplementary material

The online version of this article (10.1186/s40425-019-0606-0) contains supplementary material, which is available to authorized users.

Potential of NK cells in multiple Myeloma therapy

Introduction: Despite rapid advances in myeloma treatment with the development of new drugs, curative therapies remain elusive. Relapsed/refractory disease related to progressive dysregulation of immune system and acquired genetic abnormalities continues to be a major obstacle in achieving cure. Immune-based therapy harnessing the host defense mechanism of natural killer (NK) cells is a promising avenue in the treatment of myeloma. Areas covered: Here, we discuss the biology and cytotoxic activity of NK cells and the potential role of these innate immune cells in defense against cancer and specifically multiple myeloma. We also discuss the role of NK cells in the anti-myeloma effects of autologous and allogeneic stem cell transplantation, various novel drugs, and treatment modalities such as chimeric antigen receptor therapy. Immune evasion, either directly or indirectly involving NK cell dysfunction, may be a key and under-recognized mechanism in myeloma progression. We reviewed extensive literature identified using the keywords immunotherapy, natural killer cells, and multiple myeloma. Expert opinion: Novel treatment approaches in myeloma utilizing the immunomodulatory and cytotoxic properties of NK cells to eradicate resistant and quiescent clones could pave the way for potentially curative interventions.

Adoptive Transfer of NKG2D CAR mRNA-Engineered Natural Killer Cells in Colorectal Cancer Patients

By fusing the extracellular domain of the natural killer (NK) cell receptor NKG2D to DAP12, we constructed a chimeric antigen receptor (CAR) to improve NK cell tumor responses. An RNA electroporation approach that provides transient expression of the CAR was adopted as a risk mitigation strategy. Expression of the NKG2D RNA CAR significantly augmented the cytolytic activity of NK cells against several solid tumor cell lines in vitro and provided a clear therapeutic benefit to mice with established solid tumors. Three patients with metastatic colorectal cancer were then treated with local infusion of the CAR-NK cells. Reduction of ascites generation and a marked decrease in number of tumor cells in ascites samples were observed in the first two patients treated with intraperitoneal infusion of low doses of the CAR-NK cells. The third patient with metastatic tumor sites in the liver was treated with ultrasound-guided percutaneous injection, followed by intraperitoneal infusion of the CAR-NK cells. Rapid tumor regression in the liver region was observed with Doppler ultrasound imaging and complete metabolic response in the treated liver lesions was confirmed by positron emission tomography (PET)- computed tomographic (CT) scanning. Our results highlight a promising therapeutic potential of using RNA CAR-modified NK cells to treat metastatic colorectal cancer.

CAR T-cell bioengineering: Single variable domain of heavy chain antibody targeted CARs

Redirecting the recognition specificity of T lymphocytes to designated tumour cell surface antigens by transferring chimeric antigen receptor (CAR) genes is becoming an effective strategy to combat cancer. Today, CAR T-cell therapy has proven successful in the treatment of haematological malignancies and the first CD19 CAR T-cell products has already entered the market. This success is expanding CAR design for broader malignancies including solid tumours. Nevertheless, CARs such as those built on antigen-specific single chain antibody variable fragment (scFv) may induce some adverse effects. Here, we briefly review CAR T-cell bioengineering and discuss selected important initiatives for improved T-cell reprogramming, function and safety. In this respect, we further elaborate on unconventional CARs structured on single variable domain of heavy chain (VHH) antibodies (single-domain antibodies) as an alternative to scFv, because of their interesting immunological and physicochemical characteristics and unique structure, which shows a high degree of homology with human VH3 gene family.

Cell-based immunotherapy approaches for multiple myeloma

Despite the arrival of novel therapies, multiple myeloma (MM) remains incurable and new treatment options are needed. Chimeric antigen receptor (CAR) T cells are genetically modified T cells that express a CAR directed against specific tumour antigens. CAR T cells are able to kill target tumour cells and may result in long-lasting immune responses in vivo. The rapid development of CAR technologies has led to clinical trials in haematological cancers including MM, and CAR T cells might evolve into a standard treatment in the next few years. Only small patient cohorts with relapsed or refractory disease have so far been investigated, but promising preliminary results with high response rates have been  obtained in phase I clinical trials with B cell maturation antigen (BCMA), CD19, CD38 and κ-light-chain CAR T cells. Additional preclinical studies on CD38 and SLAMF7-CAR T cells in MM treatment yielded preclinical results that merit further investigation. Beyond the T cell approach, recent studies have focussed on CAR natural killer (NK) cells in order to increase the reactivity of these effector cells. Finally, to investigate the targeting of intracellular antigens, cellular therapies based on engineered T cell receptors (TCRs) are in development. In this review, we discuss results from preclinical and early-phase clinical trials testing the feasibility and safety of CAR T cell administration in MM, as well as early studies into approaches that utilise CAR NK cell and genetically modified TCRs.

Phase I Trial of Autologous CAR T Cells Targeting NKG2D Ligands in Patients with AML/MDS and Multiple Myeloma

NKG2D ligands are widely expressed in solid and hematologic malignancies but absent or poorly expressed on healthy tissues. We conducted a phase I dose-escalation study to evaluate the safety and feasibility of a single infusion of NKG2D-chimeric antigen receptor (CAR) T cells, without lymphodepleting conditioning in subjects with acute myeloid leukemia/myelodysplastic syndrome or relapsed/refractory multiple myeloma. Autologous T cells were transfected with a γ-retroviral vector encoding a CAR fusing human NKG2D with the CD3ζ signaling domain. Four dose levels (1 × 10⁶-3 × 10⁷ total viable T cells) were evaluated. Twelve subjects were infused [7 acute myeloid leukemia (AML) and 5 multiple myeloma]. NKG2D-CAR products demonstrated a median 75% vector-driven NKG2D expression on CD3⁺ T cells. No dose-limiting toxicities, cytokine release syndrome, or CAR T cell-related neurotoxicity was observed. No significant autoimmune reactions were noted, and none of the ≥ grade 3 adverse events were attributable to NKG2D-CAR T cells. At the single injection of low cell doses used in this trial, no objective tumor responses were observed. However, hematologic parameters transiently improved in one subject with AML at the highest dose, and cases of disease stability without further therapy or on subsequent treatments were noted. At 24 hours, the cytokine RANTES increased a median of 1.9-fold among all subjects and 5.8-fold among six AML patients. Consistent with preclinical studies, NKG2D-CAR T cell-expansion and persistence were limited. Manufactured NKG2D-CAR T cells exhibited functional activity against autologous tumor cells in vitro, but modifications to enhance CAR T-cell expansion and target density may be needed to boost clinical activity.

Synthetic immunology: T-cell engineering and adoptive immunotherapy

During the past decades, the rapidly-evolving cancer is hard to be thoroughly eliminated even though the radiotherapy and chemotherapy do exhibit efficacy in some degree. However, a breakthrough appeared when the adoptive cancer therapy [1] was developed, especially T cells armed with chimeric antigen receptors (CARs) showed great potential in tumor clinical trials recently. CAR-T cells successfully elevated the efficiency and specificity of cytotoxicity. In this review, we will talk about the design of CAR and CAR-included combinatory therapeutic applications in the principles of systems and synthetic immunology.

Development of NKG2D-based chimeric antigen receptor-T cells for gastric cancer treatment

Gastric cancer is the third leading cause of cancer-related mortalities worldwide and mostly incurable. It remains an urgent need for novel strategies in the management of patients with advanced gastric cancer. Chimeric antigen receptor (CAR) T therapy has shown unprecedented clinical success in hematological malignancies and potential utility is going on various solid tumors like gastric cancer. In this study, a broad expression of NKG2D ligands was observed in gastric cancer cell lines, making them suitable targets for gastric cancer therapy. T cells were engineered with an NKG2D-based second-generation CAR and the resulting NKG2D-CAR-T cells showed significantly increased cytolytic activity against gastric cancer compared to untransduced T cells. In vivo, these cells can significantly suppressed the growth of established gastric cancer xenografts. Besides, cisplatin was shown to upregulate NKG2D ligand expression in gastric cancer cells and enhance the susceptibility to NKG2D-CAR-T-cell-mediated cytotoxicity. In conclusion, NKG2D-based CAR-T cells have potent in vivo and in vitro anti-tumor activities against gastric cancer and could be a new paradigm for patients with gastric cancer, either used alone or combined with chemotherapy.

Application of chimeric antigen receptor-engineered T cells in ovarian cancer therapy

Due to the critical role of T cells in the immune surveillance of ovarian cancer, adoptive T-cell therapies are receiving increased attention as an immunotherapeutic approach for ovarian cancer. Chimeric antigen receptors (CARs), constructed by incorporating the single-chain Fv fragment to a T-cell signaling domain such as CD3 ζ or Fc receptor γ chain, endow T cell with nonmajor histocompatibility complex-restricted specificity. Dual specificity, trans-signaling CARs and affinity-tuned single-chain Fv fragment have broadened the applicability of CAR-engineered T-cell therapy and may be considered preferential to T cell receptor T-cell therapy in clinical care. As new insights into the CAR-engineered T cells have emerged over the last decade, we review the development of CAR T-cell therapy and discuss the progress and safety concerns regarding its translation from basic research into clinical care of ovarian cancer.

Are ovarian cancer stem cells the target for innovative immunotherapy?

Cancer stem cells (CSCs), a subpopulation of cancer cells with the ability of self-renewal and differentiation, are believed to be responsible for tumor generation, progression, metastasis, and relapse. Ovarian cancer, the most malignant gynecological cancer, has consistent pathology behavior with CSC model, which suggests that therapies based on ovarian cancer stem cells (OCSCs) can gain a more successful prognosis. Much evidence has proved that epigenetic mechanism played an important role in tumor formation and sustainment. Since CSCs are generally resistant to conventional therapies (chemotherapy and radiotherapy), immunotherapy is a more effective method that has been implemented in the clinic. Chimeric antigen receptor (CAR)-T cell, an adoptive cellular immunotherapy, which results in apparent elimination of tumor in both hematologic and solid cancers, could be used for ovarian cancer. This review covers the basic conception of CSCs and OCSCs, the implication of epigenetic mechanism underlying cancer evolution considering CSC model, the immunotherapies reported for ovarian cancer targeting OCSCs currently, and the relationship between immune system and hierarchy cancer organized by CSCs. Particularly, the promising prospects and potential pitfalls of targeting OCSC surface markers to design CAR-T cellular immunotherapy are discussed here.

CAR T-cells for cancer therapy

Chimeric antigen receptor (CAR) T-cells are redirected T-cells that can recognize cancer antigens in a major histocompatibility complex (MHC)-independent fashion. A typical CAR is comprised of two main functional domains: an extracellular antigen recognition domain, called a single-chain variable fragment (scFv), and an intracellular signaling domain. Based on the number of intracellular signaling molecules, CARs are categorized into four generations. CAR T-cell therapy has become a promising treatment for hematologic malignancies. However, results of its clinical trials on solid tumors have not been encouraging. Here, we described the structure of CARs and summarized the clinical trials of CD19-targeted CAR T-cells. The side effects, safety management, challenges, and future prospects of CAR T-cells for the treatment of cancer, particularly for solid tumors, were also discussed.

Fusion Proteins of NKG2D/NKG2DL in Cancer Immunotherapy

NKG2D (natural killer group 2, member D) is an important activating receptor in natural killer (NK) cells and some T cells. NKG2D ligands (NKG2DLs) are specifically expressed on most tumor cells. The engagement of these ligands on tumor cells to NKG2D on NK cells will induce cell-mediated cytotoxicity and have target cells destroyed. This gives NKG2D/NKG2DLs great potential in cancer therapeutic application. The creation of NKG2D/NKG2DL-based multi-functional fusion proteins is becoming one of the most promising strategies in immunotherapy for cancer. Antibodies, cytokines, and death receptors have been fused with NKG2D or its ligands to produce many powerful fusion proteins, including NKG2D-based chimeric antigen receptors (CARs). In this article, we review the recent developments of the fusion proteins with NKG2D/NKG2DL ligands in cancer immunotherapy.

Study protocol for THINK: a multinational open-label phase I study to assess the safety and clinical activity of multiple administrations of NKR-2 in patients with different metastatic tumour types

INTRODUCTION

NKR-2 are autologous T cells genetically modified to express a chimeric antigen receptor (CAR) comprising a fusion of the natural killer group 2D (NKG2D) receptor with the CD3ζ signalling domain, which associates with the adaptor molecule DNAX-activating protein of 10 kDa (DAP10) to provide co-stimulatory signal upon ligand binding. NKG2D binds eight different ligands expressed on the cell surface of many tumour cells and which are normally absent on non-neoplastic cells. In preclinical studies, NKR-2 demonstrated long-term antitumour activity towards a breadth of tumour indications, with maximum efficacy observed after multiple NKR-2 administrations. Importantly, NKR-2 targeted tumour cells and tumour neovasculature and the local tumour immunosuppressive microenvironment and this mechanism of action of NKR-2 was established in the absence of preconditioning.

METHODS AND ANALYSIS

This open-label phase I study will assess the safety and clinical activity of NKR-2 treatment administered three times, with a 2-week interval between each administration in different tumour types. The study will contain two consecutive segments: a dose escalation phase followed by an expansion phase. The dose escalation study involves two arms, one in solid tumours (five specific indications) and one in haematological tumours (two specific indications) and will include three dose levels in each arm: 3×10⁸, 1×10⁹ and 3×10⁹ NKR-2 per injection. On the identification of the recommended dose in the first segment, based on dose-limiting toxicity occurrences, the study will expand to seven different cohorts examining the seven different tumour types separately. Clinical responses will be determined according to standard Response Evaluation Criteria In Solid Tumors (RECIST) criteria for solid tumours or international working group response criteria in haematological tumours.

ETHICS APPROVAL AND DISSEMINATION

Ethical approval has been obtained at all sites. Written informed consent will be taken from all participants. The results of this study will be disseminated through presentation at international scientific conferences and reported in peer-reviewed scientific journals.

TRIAL REGISTRATION NUMBER

NCT03018405, EudraCT 2016-003312-12; Pre-result.

TAM receptor tyrosine kinases as emerging targets of innate immune checkpoint blockade for cancer therapy

Cancer immunotherapy utilizing T-cell checkpoint inhibitors has shown tremendous clinical success. Yet, this mode of treatment is effective in only a subset of patients. Unresponsive patients tend to have non-T-cell-inflamed tumors that lack markers associated with the activation of adaptive anti-tumor immune responses. Notably, elimination of cancer cells by T cells is critically dependent on the optimal activity of innate immune cells. Therefore, identifying new targets that regulate innate immune cell function and promote the engagement of adaptive tumoricidal responses is likely to lead to the development of improved therapies against cancer. Here, we review the TAM receptor tyrosine kinases-TYRO3, AXL, and MERTK-as an emerging class of innate immune checkpoints that participate in key steps of anti-tumoral immunity. Namely, TAM-mediated efferocytosis, negative regulation of dendritic cell activity, and dysregulated production of chemokines collectively favor the escape of malignant cells. Hence, disabling TAM signaling may promote engagement of adaptive immunity and complement T-cell checkpoint blockade.

Tumor-targeting domains for chimeric antigen receptor T cells

Immunotherapy with chimeric antigen receptor (CAR) T cells has been advancing steadily in clinical trials. Since the ability of engineered T cells to recognize intended tumor-associated targets is crucial for the therapeutic success, antigen-binding domains play an important role in shaping T-cell responses. Single-chain antibody and T-cell receptor fragments, natural ligands, repeat proteins, combinations of the above and universal tag-specific domains have all been used in the antigen-binding moiety of chimeric receptors. Here we outline the advantages and disadvantages of different domains, discuss the concepts of affinity and specificity, and highlight the recent progress of each targeting strategy.

Exploiting natural killer group 2D receptors for CAR T-cell therapy

Chimeric antigen receptors (CARs) are genetically engineered proteins that combine an extracellular antigen-specific recognition domain with one or several intracellular T-cell signaling domains. When expressed in T cells, these CARs specifically trigger T-cell activation upon antigen recognition. While the clinical proof of principle of CAR T-cell therapy has been established in hematological cancers, CAR T cells are only at the early stages of being explored to tackle solid cancers. This special report discusses the concept of exploiting natural killer cell receptors as an approach that could broaden the specificity of CAR T cells and potentially enhance the efficacy of this therapy against solid tumors. New data demonstrating feasibility of this approach in humans and supporting the ongoing clinical trial are also presented.

Cbx3/HP1γ deficiency confers enhanced tumor-killing capacity on CD8+ T cells

Cbx3/HP1γ is a histone reader whose function in the immune system is not completely understood. Here, we demonstrate that in CD8⁺ T cells, Cbx3/HP1γ insufficiency leads to chromatin remodeling accompanied by enhanced Prf1, Gzmb and Ifng expression. In tumors obtained from Cbx3/HP1γ-insufficient mice or wild type mice treated with Cbx3/HP1γ-insufficient CD8⁺ T cells, there is an increase of CD8⁺ effector T cells expressing the stimulatory receptor Klrk1/NKG2D, a decrease in CD4⁺ CD25⁺ FOXP3⁺ regulatory T cells (Treg cells) as well as CD25⁺ CD4⁺ T cells expressing the inhibitory receptor CTLA4. Together these changes in the tumor immune environment may have mitigated tumor burden in Cbx3/HP1γ-insufficient mice or wild type mice treated with Cbx3/HP1γ-insufficient CD8⁺ T cells. These findings suggest that targeting Cbx3/HP1γ can represent a rational therapeutic approach to control growth of solid tumors.

Generating and Expanding Autologous Chimeric Antigen Receptor T Cells from Patients with Acute Myeloid Leukemia

Adoptive transfer of genetically engineered T cells can lead to profound and durable responses in patients with hematologic malignancies, generating enormous enthusiasm among scientists, clinicians, patients, and biotechnology companies. The success of adoptive cellular immunotherapy depends upon the ability to manufacture good quality T cells. We discuss here the methodologies and reagents that are used to generate T cells for the preclinical study of chimeric antigen receptor T cell therapy for acute myeloid leukemia (AML).

Tumor Regression and Delayed Onset Toxicity Following B7-H4 CAR T Cell Therapy

B7-H4 protein is frequently overexpressed in ovarian cancer. Here, we engineered T cells with novel B7-H4-specific chimeric antigen receptors (CARs) that recognized both human and murine B7-H4 to test the hypothesis that B7-H4 CAR T cell therapy can be applied safely in preclinical models. B7-H4 CAR T cells specifically secreted IFN-γ and lysed B7-H4(+) targets. In vivo, B7-H4 CAR T cells displayed antitumor reactivity against B7-H4(+) human ovarian tumor xenografts. Unexpectedly, B7-H4 CAR T cell treatment reproducibly showed delayed, lethal toxicity 6-8 weeks after therapy. Comprehensive assessment of murine B7-H4 protein distribution uncovered expression in ductal and mucosal epithelial cells in normal tissues. Postmortem analysis revealed the presence of widespread histologic lesions that correlated with B7-H4(+) expression, and were inconsistent with graft versus host disease. Lastly, expression patterns of B7-H4 protein in normal human tissue were comparable to distribution in mice, advancing our understanding of B7-H4. We conclude that B7-H4 CAR therapy mediates control of cancer outgrowth. However, long-term engraftment of B7-H4 CAR T cells mediates lethal, off-tumor toxicity that is likely due to wide expression of B7-H4 in healthy mouse organs. This model system provides a unique opportunity for preclinical evaluation of safety approaches that limit CAR-mediated toxicity after tumor destruction in vivo.

Designing multivalent proteins based on natural killer cell receptors and their ligands as immunotherapy for cancer

INTRODUCTION

Natural killer (NK) cells are an important component of the innate immune system that play a key role in host immunity against cancer. NK cell recognition and activation is based on cell surface receptors recognizing specific ligands that are expressed on many types of tumor cells. Some of these receptors are capable of activating NK cell function while other receptors inhibit NK cell function. Therapeutic approaches to treat cancer have been developed based on preventing NK cell inhibition or using NK cell receptors and their ligands to activate NK cells or T cells to destroy tumor cells.

AREAS COVERED

This article describes the various strategies for targeting NK cell receptors and NK cell receptor ligands using multivalent proteins to activate immunity against cancer.

EXPERT OPINION

NK cell receptors work in synergy to activate NK cell effector responses. Effective anti-cancer strategies will need to not only kill tumor cells but must also lead to the destruction of the tumor microenvironment. Immunotherapy based on NK cells and their receptors has the capacity to accomplish this through triggering lymphocyte cytotoxicity and cytokine production.

How Chimeric Antigen Receptor Design Affects Adoptive T Cell Therapy

Chimeric antigen receptor (CAR) T cells have been developed to treat tumors and have shown great success against B cell malignancies. Exploiting modular designs and swappable domains, CARs can target an array of cell surface antigens and, upon receptor-ligand interactions, direct signaling cascades, thereby driving T cell effector functions. CARs have been designed using receptors, ligands, or scFv binding domains. Different regions of a CAR have each been found to play a role in determining the overall efficacy of CAR T cells. Therefore, this review provides an overview of CAR construction and common designs. Each CAR region is discussed in the context of its importance to a CAR's function. Additionally, the review explores how various engineering strategies have been applied to CAR T cells in order to regulate CAR T cell function and activity. J. Cell. Physiol. 231: 2590-2598, 2016. © 2016 Wiley Periodicals, Inc.

Driving CAR T-cells forward

The engineered expression of chimeric antigen receptors (CARs) on the surface of T cells enables the redirection of T-cell specificity. Early clinical trials using CAR T cells for the treatment of patients with cancer showed modest results, but the impressive outcomes of several trials of CD19-targeted CAR T cells in the treatment of patients with B-cell malignancies have generated an increased enthusiasm for this approach. Important lessons have been derived from clinical trials of CD19-specific CAR T cells, and ongoing clinical trials are testing CAR designs directed at novel targets involved in haematological and solid malignancies. In this Review, we discuss these trials and present strategies that can increase the antitumour efficacy and safety of CAR T-cell therapy. Given the fast-moving nature of this field, we only discuss studies with direct translational application currently or soon-to-be tested in the clinical setting.

Treatment of solid tumors with chimeric antigen receptor-engineered T cells: current status and future prospects

Chimeric antigen receptors (CARs) are artificial recombinant receptors that generally combine the antigen-recognition domain of a monoclonal antibody with T cell activation domains. Recent years have seen great success in clinical trials employing CD19-specific CAR-T cell therapy for B cell leukemia. Nevertheless, solid tumors remain a major challenge for CAR-T cell therapy. This review summarizes the preclinical and clinical studies on the treatment of solid tumors with CAR-T cells. The major hurdles for the success of CAR-T and the novel strategies to address these hurdles have also been described and discussed.