Blocking expression of inhibitory receptor NKG2A overcomes tumor resistance to NK cells

The soldiers needed to be awakened: Tumor-infiltrating immune cells

In the tumor microenvironment, tumor-infiltrating immune cells (TIICs) are a key component. Different types of TIICs play distinct roles. CD8+ T cells and natural killer (NK) cells could secrete soluble factors to hinder tumor cell growth, whereas regulatory T cells (Tregs) and myeloid-derived suppressor cells (MDSCs) release inhibitory factors to promote tumor growth and progression. In the meantime, a growing body of evidence illustrates that the balance between pro- and anti-tumor responses of TIICs is associated with the prognosis in the tumor microenvironment. Therefore, in order to boost anti-tumor response and improve the clinical outcome of tumor patients, a variety of anti-tumor strategies for targeting TIICs based on their respective functions have been developed and obtained good treatment benefits, including mainly immune checkpoint blockade (ICB), adoptive cell therapies (ACT), chimeric antigen receptor (CAR) T cells, and various monoclonal antibodies. In recent years, the tumor-specific features of immune cells are further investigated by various methods, such as using single-cell RNA sequencing (scRNA-seq), and the results indicate that these cells have diverse phenotypes in different types of tumors and emerge inconsistent therapeutic responses. Hence, we concluded the recent advances in tumor-infiltrating immune cells, including functions, prognostic values, and various immunotherapy strategies for each immune cell in different tumors.

Immunoglobulin-like transcript 2 blockade restores antitumor immune responses in glioblastoma

Glioblastoma stands as the most frequent primary brain tumor. Despite the multimodal therapy for glioblastoma patients, the survival rate is very low, highlighting the need for novel therapies that improve patient outcomes. Immune checkpoint blockade strategies are achieving promising results in a myriad of tumors and several studies have reported its efficacy in glioblastoma at a preclinical level. ILT2 is a novel immune checkpoint that exerts an inhibitory effect via the interaction with classical and non-classical HLA class-I molecules. Herein, we report that ILT2 blockade promotes antitumor responses against glioblastoma. In silico and immunohistochemical analyses revealed that the expression of ILT2 and its ligands HLA-A, -B, -C, and -E are highly expressed in patients with glioblastoma. Disruption of ILT2 with blocking monoclonal antibodies increased natural killer cell-mediated IFN-γ production and cytotoxicity against glioblastoma, partially reverting the immunosuppression linked to this malignancy. In addition, co-treatment with temozolomide strengthened the antitumor capacity of anti-ILT2-treated immune cells. Collectively, our results establish the basis for future studies regarding the clinical potential of ILT2 blockade alone or in combination regimens in glioblastoma.

The new progress in cancer immunotherapy

The cross talk between immune and non-immune cells in the tumor microenvironment leads to immunosuppression, which promotes tumor growth and survival. Immunotherapy is an advanced treatment that boosts humoral and cellular immunity rather than using chemotherapy or radiation-based strategy associated with non-specific targets and toxic effects on normal cells. Immune checkpoint inhibitors and T cell-based immunotherapy have already exhibited significant effects against solid tumors and leukemia. Tumor cells that escape immune surveillance create a major obstacle to acquiring an effective immune response in cancer patients. Tremendous progress had been made in recent years on a wide range of innate and adaptive immune checkpoints which play a significant role to prevent tumorigenesis, and might therefore be potential targets to suppress tumor cells growth. This review aimed to summarize the underlying molecular mechanisms of existing immunotherapy approaches including T cell and NK-derived immune checkpoint therapy, as well as other intrinsic and phagocytosis checkpoints. Together, these insights will pave the way for new innate and adaptive immunomodulatory targets for the development of highly effective new therapy in the future.

Emerging Trends in Immunotherapy for Cancer

Recent advances in cancer immunology have enabled the discovery of promising immunotherapies for various malignancies that have shifted the cancer treatment paradigm. The innovative research and clinical advancements of immunotherapy approaches have prolonged the survival of patients with relapsed or refractory metastatic cancers. Since the U.S. FDA approved the first immune checkpoint inhibitor in 2011, the field of cancer immunotherapy has grown exponentially. Multiple therapeutic approaches or agents to manipulate different aspects of the immune system are currently in development. These include cancer vaccines, adoptive cell therapies (such as CAR-T or NK cell therapy), monoclonal antibodies, cytokine therapies, oncolytic viruses, and inhibitors targeting immune checkpoints that have demonstrated promising clinical efficacy. Multiple immunotherapeutic approaches have been approved for specific cancer treatments, while others are currently in preclinical and clinical trial stages. Given the success of immunotherapy, there has been a tremendous thrust to improve the clinical efficacy of various agents and strategies implemented so far. Here, we present a comprehensive overview of the development and clinical implementation of various immunotherapy approaches currently being used to treat cancer. We also highlight the latest developments, emerging trends, limitations, and future promises of cancer immunotherapy.

Phase I study of expanded natural killer cells in combination with cetuximab for recurrent/metastatic nasopharyngeal carcinoma

BACKGROUND

Nasopharyngeal carcinoma (NPC) cells express high levels of epidermal growth factor receptor (EGFR). Cetuximab is an anti-EGFR monoclonal antibody that promotes natural killer (NK) cell-mediated antibody-dependent cellular cytotoxicity (ADCC) via engagement of CD16. We studied safety and efficacy of combining cetuximab with autologous expanded NK cells in patients with recurrent and/or metastatic NPC who had failed at least two prior lines of chemotherapy.

METHODS

Seven subjects (six patients) received cetuximab every 3 weeks (six doses maximum) in the pre-trial phase. Autologous NK cells, expanded by co-culture with irradiated K562-mb15-41BBL cells, were then infused on the day after administration of cetuximab. Primary and secondary objectives were to determine safety of this combination therapy and to assess tumor responses, respectively.

RESULTS

Median NK cell expansion from peripheral blood mononucleated cells after 10 days of culture with K562-mb15-41BBL was 274-fold (range, 36-534, n = 10), and the median expression of CD16 was 98.4% (range, 67.8-99.7%). Skin rash, the commonest side effect of cetuximab in the pre-trial phase, was not exacerbated by NK cell infusion. No intolerable side effects were observed. Stable disease was observed in four subjects and progressive disease in three subjects. Three patients who received NK cells twice had time to disease progression of 12, 13, and 19 months.

CONCLUSION

NK cells with high ADCC potential can be expanded from patients with heavily pre-treated NPC. The safety profile and encouraging clinical responses observed after combining these cells with cetuximab warrant further studies of this approach. (clinicalTrials.gov NCT02507154, 23/07/2015).

PRECIS

Engaging NK cell-mediated ADCC using cetuximab plus autologous NK cells in EGFR-positive NPC was well tolerated among heavily pre-treated recurrent NPC. Promising results were observed with 3 out of 7 subjects demonstrating durable stable disease.

The application of the natural killer cells, macrophages and dendritic cells in treating various types of cancer

Innate immune cells such as natural killer (NK) cells, macrophages and dendritic cells (DCs) are involved in the surveillance and clearance of tumor. Intensive research has exposed the mechanisms of recognition and elimination of tumor cells by these immune cells as well as how cancers evade immune response. Hence, harnessing the immune cells has proven to be an effective therapy in treating a variety of cancers. Strategies aimed to harness and augment effector function of these cells for cancer therapy have been the subject of intense researches over the decades. Different immunotherapeutic possibilities are currently being investigated for anti-tumor activity. Pharmacological agents known to influence immune cell migration and function include therapeutic antibodies, modified antibody molecules, toll-like receptor agonists, nucleic acids, chemokine inhibitors, fusion proteins, immunomodulatory drugs, vaccines, adoptive cell transfer and oncolytic virus–based therapy. In this review, we will focus on the preclinical and clinical applications of NK cell, macrophage and DC immunotherapy in cancer treatment.

Checkpoint molecules on infiltrating immune cells in colorectal tumor microenvironment

Colorectal cancer (CRC) is one of the most prevalent cancer types worldwide, with a high mortality rate due to metastasis. The tumor microenvironment (TME) contains multiple interactions between the tumor and the host, thus determining CRC initiation and progression. Various immune cells exist within the TME, such as tumor-infiltrating lymphocytes (TILs), tumor-associated macrophages (TAMs), and tumor-associated neutrophils (TANs). The immunotherapy approach provides novel opportunities to treat solid tumors, especially toward immune checkpoints. Despite the advances in the immunotherapy of CRC, there are still obstacles to successful treatment. In this review, we highlighted the role of these immune cells in CRC, with a particular emphasis on immune checkpoint molecules involved in CRC pathogenesis.

Implications of NKG2A in immunity and immune-mediated diseases

In recent studies, NKG2A is revealed to be a key immune checkpoint for both natural killer (NK) cells and CD8⁺ T cells. It form heterodimer receptors with CD94, and targets the peptide-presenting human leukocyte antigen-E (HLA-E) molecules. Upon crosslinking, NKG2A/CD94 delivers inhibitory signals for NK cells and CD8⁺ T cells, while blocking NKG2A can effectively unleash functions of these cytotoxic lymphocytes. The interaction between NKG2A and HLA-E contributes to tumor immune escape, and NKG2A-mediated mechanisms are currently being exploited to develop potential antitumor therapeutic strategies. In addition, growing evidence shows that NKG2A also plays important roles in other immune-related diseases including viral infections, autoimmune diseases, inflammatory diseases, parasite infections and transplant rejection. Therefore, the current work focuses on describing the effect of NKG2A on immune regulation and exploring its potential role in immune-mediated disorders.

Overcoming tumor resistance mechanisms in CAR-NK cell therapy

Despite the impressive results of autologous CAR-T cell therapy in refractory B lymphoproliferative diseases, CAR-NK immunotherapy emerges as a safer, faster, and cost-effective approach with no signs of severe toxicities as described for CAR-T cells. Permanently scrutinized for its efficacy, recent promising data in CAR-NK clinical trials point out the achievement of deep, high-quality responses, thus confirming its potential clinical use. Although CAR-NK cell therapy is not significantly affected by the loss or downregulation of its CAR tumor target, as in the case of CAR-T cell, a plethora of common additional tumor intrinsic or extrinsic mechanisms that could also disable NK cell function have been described. Therefore, considering lessons learned from CAR-T cell therapy, the emergence of CAR-NK cell therapy resistance can also be envisioned. In this review we highlight the processes that could be involved in its development, focusing on cytokine addiction and potential fratricide during manufacturing, poor tumor trafficking, exhaustion within the tumor microenvironment (TME), and NK cell short in vivo persistence on account of the limited expansion, replicative senescence, and rejection by patient’s immune system after lymphodepletion recovery. Finally, we outline new actively explored alternatives to overcome these resistance mechanisms, with a special emphasis on CRISPR/Cas9 mediated genetic engineering approaches, a promising platform to optimize CAR-NK cell function to eradicate refractory cancers.

Natural killer cells: the next wave in cancer immunotherapy

Immunotherapies focusing on rejuvenating T cell activities, like PD-1/PD-L1 and CTLA-4 blockade, have unprecedentedly revolutionized the landscape of cancer treatment. Yet a previously underexplored component of the immune system - natural killer (NK) cell, is coming to the forefront of immunotherapeutic attempts. In this review, we discuss the contributions of NK cells in the success of current immunotherapies, provide an overview of the current preclinical and clinical strategies at harnessing NK cells for cancer treatment, and highlight that NK cell-mediated therapies emerge as a major target in the next wave of cancer immunotherapy.

Immune correlates of HIV-1 reservoir cell decline in early-treated infants

Initiation of antiretroviral therapy (ART) in infected neonates within hours after birth limits viral reservoir seeding but does not prevent long-term HIV-1 persistence. Here, we report parallel assessments of HIV-1 reservoir cells and innate antiviral immune responses in a unique cohort of 37 infected neonates from Botswana who started ART extremely early, frequently within hours after birth. Decline of genome-intact HIV-1 proviruses occurs rapidly after initiation of ART and is associated with an increase in natural killer (NK) cell populations expressing the cytotoxicity marker CD57 and with a decrease in NK cell subsets expressing the inhibitory marker NKG2A. Immune perturbations in innate lymphoid cells, myeloid dendritic cells, and monocytes detected at birth normalize after rapid institution of antiretroviral therapy but do not notably influence HIV-1 reservoir cell dynamics. These results suggest that HIV-1 reservoir cell seeding and evolution in early-treated neonates is markedly influenced by antiviral NK cell immune responses.

Recruited and Tissue-Resident Natural Killer Cells in the Lung During Infection and Cancer

Natural killer (NK) cells are an important component of the innate immune system, and have a key role in host defense against infection and in tumor surveillance. Tumors and viruses employ remarkably similar strategies to avoid recognition and killing by NK cells and so much can be learnt by comparing NK cells in these disparate diseases. The lung is a unique tissue environment and immune cells in this organ, including NK cells, exist in a hypofunctional state to prevent activation against innocuous stimuli. Upon infection, rapid NK cell infiltration into the lung occurs, the amplitude of which is determined by the extent of inflammation and damage. Activated NK cells kill infected cells and produce pro-inflammatory cytokines and chemokines to recruit cells of the adaptive immune system. More recent evidence has shown that NK cells also play an additional role in resolution of inflammation. In lung cancer however, NK cell recruitment is impaired and those that are present have reduced functionality. The majority of lung NK cells are circulatory, however recently a small population of tissue-resident lung NK cells has been described. The specific role of this subset is yet to be determined, but they show similarity to resident memory T cell subsets. Whether resident or recruited, NK cells are important in the control of pulmonary infections, but equally, can drive excessive inflammation if not regulated. In this review we discuss how NK cells are recruited, controlled and retained in the specific environment of the lung in health and disease. Understanding these mechanisms in the context of infection may provide opportunities to promote NK cell recruitment and function in the lung tumor setting.

What Inhibits Natural Killers’ Performance in Tumour

Natural killer cells are innate lymphocytes with the ability to lyse tumour cells depending on the balance of their activating and inhibiting receptors. Growing numbers of clinical trials show promising results of NK cell-based immunotherapies. Unlike T cells, NK cells can lyse tumour cells independent of antigen presentation, based simply on their activation and inhibition receptors. Various strategies to improve NK cell-based therapies are being developed, all with one goal: to shift the balance to activation. In this review, we discuss the current understanding of ways NK cells can lyse tumour cells and all the inhibitory signals stopping their cytotoxic potential.

Gene-Based Natural Killer Cell Therapies for the Treatment of Pediatric Hematologic Malignancies

Pediatric blood cancers are among the most common malignancies that afflict children. Intensive chemotherapy is not curative in many cases, and novel therapies are urgently needed. NK cells hold promise for use as immunotherapeutic effectors due to their favorable safety profile, intrinsic cytotoxic properties, and potential for genetic modification that can enhance specificity and killing potential. NK cells can be engineered to express CARs targeting tumor-specific antigens, to downregulate inhibitory and regulatory signals, to secrete cytokine, and to optimize interaction with small molecule engagers. Understanding NK cell biology is key to designing immunotherapy for clinical translation.

Natural killer cells and acute myeloid leukemia: promises and challenges

Acute myeloid leukemia (AML) is considered as one of the most malignant conditions of the bone marrow. Over the past few decades, despite substantial progresses in the management of AML, relapse remission remains a major problem. Natural killer cells (NK cells) are known as a unique component of the innate immune system. Due to swift tumor detection, distinct cytotoxic action, and extensive immune interaction, NK cells have been used in various cancer settings for decades. It has been a growing knowledge of therapeutic magnitudes ranging from adoptive NK cell transfer to chimeric antigen receptor NK cells, aiming to achieve better therapeutic responses in patients with AML. In this article, the potentials of NK cells for treatment of AML are highlighted, and challenges for such therapeutic methods are discussed. In addition, the clinical application of NK cells, mainly in patients with AML, is pictured according to the existing evidence.

PRDM1 Drives Human Primary T Cell Hyporesponsiveness by Altering the T Cell Transcriptome and Epigenome

T cell hyporesponsiveness is crucial for the functional immune system and prevents the damage induced by alloreactive T cells in autoimmune pathology and transplantation. Here, we found low expression of PRDM1 in T cells from donor and recipients both related to the occurrence of acute graft-versus-host disease (aGVHD). Our systematic multiomics analysis found that the transcription factor PRDM1 acts as a master regulator during inducing human primary T cell hyporesponsiveness. PRDM1-overexpression in primary T cells expanded Treg cell subset and increased the expression level of FOXP3, while decreased expression had the opposite effects. Moreover, the binding motifs of key T cell function regulators, such as FOS, JUN and AP-1, were enriched in PRDM1 binding sites and that PRDM1 altered the chromatin accessibility of these regions. Multiomics analysis showed that PRDM1 directly upregulated T cell inhibitory genes such as KLF2 and KLRD1 and downregulated the T cell activation gene IL2, indicating that PRDM1 could promote a tolerant transcriptional profile. Further analysis showed that PRDM1 upregulated FOXP3 expression level directly by binding to FOXP3 upstream enhancer region and indirectly by upregulating KLF2. These results indicated that PRDM1 is sufficient for inducing human primary T cell hyporesponsiveness by transcriptomic and epigenetic manners.

The Dynamic Role of NK Cells in Liver Cancers: Role in HCC and HBV Associated HCC and Its Therapeutic Implications

Hepatocellular carcinoma (HCC) remains an important complication of chronic liver disease, especially when cirrhosis occurs. Existing treatment strategies include surgery, loco-regional techniques, and chemotherapy. Natural killer cells are distinctive cytotoxic lymphocytes that play a vital role in fighting tumors and infections. As an important constituent of the innate immune system against cancer, phenotypic and functional deviations of NK cells have been demonstrated in HCC patients who also exhibit perturbation of the NK-activating receptor/ligand axis. The rate of recurrence of tumor-infiltrating and circulating NK cells are positively associated with survival benefits in HCC and have prognostic significance, suggesting that NK cell dysfunction is closely related to HCC progression. NK cells are the first-line effector cells of viral hepatitis and play a significant role by directly clearing virus-infected cells or by activating antigen-specific T cells by producing IFN-γ. In addition, chimeric antigen receptor (CAR) engineered NK cells suggest an exclusive opportunity to produce CAR-NKs with several specificities with fewer side effects. In the present review, we comprehensively discuss the innate immune landscape of the liver, particularly NK cells, and the impact of tumor immune microenvironment (TIME) on the function of NK cells and the biological function of HCC. Furthermore, the role of NK cells in HCC and HBV-induced HCC has also been comprehensively elaborated. We also elaborate on available NK cell-based immunotherapeutic approaches in HCC treatment and summarize current advancements in the treatment of HCC. This review will facilitate researchers to understand the importance of the innate immune landscape of NK cells and lead to devising innovative immunotherapeutic strategies for the systematic treatment of HCC.

Risk Factors and Biomarkers for Immune-Related Adverse Events: A Practical Guide to Identifying High-Risk Patients and Rechallenging Immune Checkpoint Inhibitors

Immune-related adverse events (irAEs) are a range of complications associated with the use of immune-checkpoint inhibitors (ICIs). Two major classes of ICIs widely used are Cytotoxic T-Lymphocyte Antigen 4 (CTLA4) and Programmed Cell death-1 (PD-1)/Programmed death-ligand 1 (PD-L1) inhibitors. High-grade irAEs are life-threatening and often cause a severe decline in performance status in such that patients do not qualify for any further anticancer treatments. It is difficult to generalize the evidence in the current literature on risk factors or biomarkers for the entire class of ICIs as the studies so far are either disease-specific (e.g., lung cancer or melanoma) or ICI agent-specific (e.g., pembrolizumab, ipilimumab) or irAE-specific (e.g., pneumonitis or gastritis). In this review, risk factors and biomarkers to consider before initiating or monitoring ICI are listed with a practical purpose in day-to-day practice. Risk factors are grouped into demographics and social history, medical history, and medication history, tumor-specific and agent-specific risk factors. A higher risk of irAE is associated with age <60 years, high body mass index, women on CTLA4 and men on PD-1/PD-L1 agents, and chronic smokers. Patients with significant kidney (Stage IV-V), cardiac (heart failure, coronary artery disease, myocardial infarction, hypertension), and lung (asthma, pulmonary fibrosis, and chronic obstructive pulmonary disease) are at a higher risk of respective organ-specific irAEs. Pre-existing autoimmune disease and chronic use of certain drugs (proton pump inhibitors, diuretics, anti-inflammatory drugs) also increase the irAE-risk. Biomarkers are categorized into circulating blood counts, cytokines, autoantibodies, HLA genotypes, microRNA, gene expression profiling, and serum proteins. The blood counts and certain protein markers (albumin and thyroid-stimulating hormone) are readily accessible in current practice. High neutrophil-lymphocyte ratio, eosinophil/monocyte/lymphocyte counts; TSH and troponins at diagnosis and drop in the white count and lymphocyte count can predict irAE. Other biomarkers with limited evidence are cytokines, autoantibodies, HLA genotypes, microRNA, and gene expression profiling. With fast-expanding approvals for ICIs in various cancer types, knowledge on risk factors and biomarkers can help providers assess the irAE-risk of their patients. Prospective disease and agent-specific studies are needed to provide further insight on this essential aspect of ICI therapy.

CRISPR Gene Editing of Human Primary NK and T Cells for Cancer Immunotherapy

Antitumor activity of immune cells such as T cells and NK cells has made them auspicious therapeutic regimens for adaptive cancer immunotherapy. Enhancing their cytotoxic effects against malignancies and overcoming their suppression in tumor microenvironment (TME) may improve their efficacy to treat cancers. Clustered, regularly interspaced short palindromic repeats (CRISPR) genome editing has become one of the most popular tools to enhance immune cell antitumor activity. In this review we highlight applications and practicability of CRISPR/Cas9 gene editing and engineering strategies for cancer immunotherapy. In addition, we have reviewed several approaches to study CRISPR off-target effects.

Taking Lessons from CAR-T Cells and Going Beyond: Tailoring Design and Signaling for CAR-NK Cells in Cancer Therapy

Cancer immunotherapies utilize the capabilities of the immune system to efficiently target malignant cells. In recent years, chimeric antigen receptor (CAR) equipped T cells showed promising results against B cell lymphomas. Autologous CAR-T cells require patient-specific manufacturing and thus extensive production facilities, resulting in high priced therapies. Along with potentially severe side effects, these are the major drawbacks of CAR-T cells therapies. Natural Killer (NK) cells pose an alternative for CAR equipped immune cells. Since NK cells can be safely transferred from healthy donors to cancer patients, they present a suitable platform for an allogeneic “off-the-shelf” immunotherapy. However, administration of activated NK cells in cancer therapy has until now shown poor anti-cancer responses, especially in solid tumors. Genetic modifications such as CARs promise to enhance recognition of tumor cells, thereby increasing anti-tumor effects and improving clinical efficacy. Although the cell biology of T and NK cells deviates in many aspects, the development of CAR-NK cells frequently follows within the footsteps of CAR-T cells, meaning that T cell technologies are simply adopted to NK cells. In this review, we underline the unique properties of NK cells and their potential in CAR therapies. First, we summarize the characteristics of NK cell biology with a focus on signaling, a fine-tuned interaction of activating and inhibitory receptors. We then discuss why tailored NK cell-specific CAR designs promise superior efficacy compared to designs developed for T cells. We summarize current findings and developments in the CAR-NK landscape: different CAR formats and modifications to optimize signaling, to target a broader pool of antigens or to increase in vivo persistence. Finally, we address challenges beyond NK cell engineering, including expansion and manufacturing, that need to be addressed to pave the way for CAR-NK therapies from the bench to the clinics.

Natural killer cell therapy: A new frontier for obesity-associated cancer

Natural killer (NK) cell infiltration of solid tumours is associated with better outcomes, placing augmentation of NK cell abundance in tumours as an attractive immunotherapeutic approach. The unique ability of NK cells to target cancer cells without antigen specificity increases their versatility and applicability as an immunotherapeutic tool. However, successful utilisation of NK cell-based therapies in solid tumours is still at an early stage. Obesity has become a global health epidemic, and the prevalence of obesity-associated cancers has significantly increased. Obesity-associated malignancies provide a unique challenge for the successful application of cell-based immunotherapies including NK cell-based therapies because significant numbers of NK and T cells are recruited to the visceral adipose tissue at the expense of successful tumour infiltration and eradication. As such, immunotherapy efficacy has been disappointing for obesity-associated malignancies such as oesophageal and gastric adenocarcinoma. Therefore, immunotherapies for obesity-associated cancers warrant our further attention. Indeed, it is becoming ever more obvious that more innovative approaches are needed to re-invigorate anti-tumour immunity and overcome immune exclusion in such tumours. In this review, we briefly summarise the dysfunctionality of NK cells in obesity-associated cancer. We outline the NK cell-based immunotherapeutic approaches which hold promise as effective treatments in this disease space, including CAR-NK cells. Furthermore, we suggest future avenues which possess the potential to transform immunotherapy and specifically NK cell therapy efficacy for obesity-associated cancer.

Natural Killer Cells in the Malignant Niche of Multiple Myeloma

Natural killer (NK) cells represent a subset of CD3- CD7+ CD56+/dim lymphocytes with cytotoxic and suppressor activity against virus-infected cells and cancer cells. The overall potential of NK cells has brought them to the spotlight of targeted immunotherapy in solid and hematological malignancies, including multiple myeloma (MM). Nonetheless, NK cells are subjected to a variety of cancer defense mechanisms, leading to impaired maturation, chemotaxis, target recognition, and killing. This review aims to summarize the available and most current knowledge about cancer-related impairment of NK cell function occurring in MM.

HLA-E and HLA-F Are Overexpressed in Glioblastoma and HLA-E Increased After Exposure to Ionizing Radiation

BACKGROUND/AIM

Glioblastoma (GBM) is one of the deadliest human cancers responding very poorly to therapy. Although the central nervous system has been traditionally considered an immunologically privileged site with an enhanced immune response, GBM appears to benefit from this immunosuppressive milieu. Immunomodulatory molecules play an important role in immune tumor-host interactions. Non-classical human leukocyte antigens (HLA) class Ib molecules HLA-E, HLA-F, and HLA-G have been previously described to be involved in protecting semi-allogeneic fetal allografts from the maternal immune response and in transplant tolerance as well as tumoral immune escape. Unfortunately, their role in GBM remains poorly understood. Our study, therefore, aimed to characterize the relationship between the expression of these molecules in GBM on the transcriptional level and clinicopathological and molecular features of GBM as well as the effect of ionizing radiation.

MATERIALS AND METHODS

We performed the analysis of HLA-E, HLA-F, and HLA-G mRNA expression in 69 GBM tissue samples and 21 non-tumor brain tissue samples (controls) by reverse transcription polymerase chain reaction. Furthermore, two primary GBM cell cultures had been irradiated to identify the effect of ionizing radiation on the expression of non-classical HLA molecules.

RESULTS

Analyses revealed that both HLA-E and HLA-F are significantly up-regulated in GBM samples. Subsequent survival analysis showed a significant association between low expression of HLA-E and shorter survival of GBM patients. The dysregulated expression of both molecules was also observed between patients with methylated and unmethylated O-6-methylguanine-DNA methyltransferase (MGMT) promoter. Finally, we showed that ionizing radiation increased HLA-E expression level in GBM cells in vitro.

CONCLUSION

HLA-E and HLA-F play an important role in GBM biology and could be used as diagnostic biomarkers, and in the case of HLA-E also as a prognostic biomarker.

Aggressive Natural Killer Cell Leukemia: A Brief Overview of Its Genomic Landscape, Histological Features, and Current Management

Aggressive natural killer-cell leukemia (ANKL) is a rare hematological malignancy characterized by the abnormal proliferation of natural killer (NK) cells. There are currently no therapies approved by the US Food and Drug Administration (FDA) for the treatment of ANKL, but advancements in genomics are assisting in the unraveling of this rare malignancy. We selected 37 articles that contained information on genomics, immunohistochemistry, and/or current clinical trials relating to the treatment and survival of ANKL. Current therapeutic strategies have been subdivided into (1) concurrent chemoradiation, (2) sequential chemoradiation, and (3) sandwich chemoradiation. These methods have been developed to reduce toxicity while still producing a pathologic response. Concurrent chemoradiation with VIDL (etoposide, ifosfamide, dexamethasone, and L-asparaginase) produced an excellent clinical response, while sequential chemoradiation with SMILE (steroid dexamethasone, methotrexate, ifosfamide, L-asparaginase, and etoposide) showed an adequate response, but with severe hematologic toxicity. The efficacy of L-asparaginase in chemotherapeutic regimens and its association with NK-cell apoptosis have led to its inclusion in all standard regimens. Future studies are focusing on the addition of a programmed death-ligand 1 (PD-L1) inhibitor and hematopoietic stem cell transplant (HSCT).

Engineered NK Cells Against Cancer and Their Potential Applications Beyond

Cell therapy is an innovative therapeutic concept where viable cells are implanted, infused, or grafted into a patient to treat impaired or malignant tissues. The term was first introduced circa the 19th century and has since resulted in multiple breakthroughs in different fields of medicine, such as neurology, cardiology, and oncology. Lately, cell and gene therapy are merging to provide cell products with additional or enhanced properties. In this context, adoptive transfer of genetically modified cytotoxic lymphocytes has emerged as a novel treatment option for cancer patients. To this day, five cell therapy products have been FDA approved, four of which for CD19-positive malignancies and one for B-cell maturation antigen (BCMA)-positive malignancies. These are personalized immunotherapies where patient T cells are engineered to express chimeric antigen receptors (CARs) with the aim to redirect the cells against tumor-specific antigens. CAR-T cell therapies show impressive objective response rates in clinical trials that, in certain instances, may reach up to 80%. However, the life-threatening side effects associated with T cell toxicity and the manufacturing difficulties of developing personalized therapies hamper their widespread use. Recent literature suggests that Natural Killer (NK) cells, may provide a safer alternative and an 'off-the-shelf' treatment option thanks to their potent antitumor properties and relatively short lifespan. Here, we will discuss the potential of NK cells in CAR-based therapies focusing on the applications of CAR-NK cells in cancer therapy and beyond.

Correlation of Human Leukocyte Antigen-E Genomic Polymorphism with Leukemia and Functional Study of Human Leukocyte Antigen-E Different Type Promoters

Human leukocyte antigen (HLA)-E is one of the least polymorphic nonclassical major histocompatibility complex (MHC) I genes; its nucleotide variability can affect immune response. In this study, we assess the correlation between HLA-E polymorphism and leukemia and further study the transcriptional activity of promoter variation at nucleotide position-26. A total of 142 healthy blood donors and 111 leukemia patients were collected. The genomic sequence of HLA-E was amplified by high-fidelity reaction system and identified by Sanger and cloning sequencing. The dual luciferase reporter gene assay was used to detect the transcription activity of promoter variation at nucleotide position-26. In the HLA-E genomic sequence results, a total of 16 alleles and 32 genotypes were detected; the HLA-E*01:01:01:06 allele had a significantly lower frequency in leukemia patients than in healthy participants (p = 0.026 < 0.05). And the HLA-E*01:03:02:01, *01:03:02:01 genotype showed the greatest difference in frequency between the two groups of participants (p = 0.028 < 0.05). Eight HLA-E alleles were first reported worldwide in Chinese individuals. The results of the dual luciferase reporter gene experiment showed that the transcription activity of the mutant-type promoter (HLA-E*01:01:01:06 with "T" allele at nucleotide position-26) was significantly lower compared with the wild-type promoter (HLA-E*01:01:01:01 with "G" allele at nucleotide position-26) (p = 0.0242 < 0.05). HLA-E*01:01:01:06 allele has a protective effect against leukemia through decreasing transcription activity by "T" variation at nucleotide position-26.

Sweet Immune Checkpoint Targets to Enhance T Cell Therapy

Despite tremendous success against hematological malignancies, the performance of chimeric Ag receptor T cells against solid tumors remains poor. In such settings, the lack of success of this groundbreaking immunotherapy is in part mediated by ligand engagement of immune checkpoint molecules on the surface of T cells in the tumor microenvironment. Although CTLA-4 and programmed death-1 (PD-1) are well-established checkpoints that inhibit T cell activity, the engagement of glycans and glycan-binding proteins are a growing area of interest due to their immunomodulatory effects. This review discusses exemplary strategies to neutralize checkpoint molecules through an in-depth overview of genetic engineering approaches aimed at overcoming the inhibitory programmed death ligand-1 (PD-L1)/PD-1 axis in T cell therapies and summarizes current knowledge on glycoimmune interactions that mediate T cell immunosuppression.

Back to the Future: Spatiotemporal Determinants of NK Cell Antitumor Function

NK cells play a crucial role in host protection during tumorigenesis. Throughout tumor development, however, NK cells become progressively dysfunctional through a combination of dynamic tissue-specific and systemic factors. While a number of immunosuppressive mechanisms present within the tumor microenvironment have been characterized, few studies have contextualized the spatiotemporal dynamics of these mechanisms during disease progression and across anatomical sites. Understanding how NK cell immunosuppression evolves in these contexts will be necessary to optimize NK cell therapy for solid and metastatic cancers. Here, we outline the spatiotemporal determinants of antitumor NK cell regulation, including heterogeneous tumor architecture, temporal disease states, diverse cellular communities, as well as the complex changes in NK cell states produced by the sum of these higher-order elements. Understanding of the signals encountered by NK cells across time and space may reveal new therapeutic targets to harness the full potential of NK cell therapy for cancer.

CAR-NK Cells: From Natural Basis to Design for Kill

Chimeric antigen receptors (CARs) are fusion proteins with an extracellular antigen recognition domain and numerous intracellular signaling domains that have been genetically modified. CAR-engineered T lymphocyte-based therapies have shown great success against blood cancers; however, potential fatal toxicity, such as in cytokine release syndrome, and high costs are some shortcomings that limit the clinical application of CAR-engineered T lymphocytes and remain to overcome. Natural killer (NK) cells are the focal point of current immunological research owing to their receptors that prove to be promising immunotherapeutic candidates for treating cancer. However, to date, manipulation of NK cells to treat malignancies has been moderately successful. Recent progress in the biology of NK cell receptors has greatly transformed our understanding of how NK cells recognize and kill tumor and infected cells. CAR-NK cells may serve as an alternative candidate for retargeting cancer because of their unique recognition mechanisms, powerful cytotoxic effects especially on cancer cells in both CAR-dependent and CAR-independent manners and clinical safety. Moreover, NK cells can serve as an ‘off-the-shelf product’ because NK cells from allogeneic sources can also be used in immunotherapies owing to their reduced risk of alloreactivity. Although ongoing fundamental research is in the beginning stages, this review provides an overview of recent developments implemented to design CAR constructs to stimulate NK activation and manipulate NK receptors for improving the efficiency of immunotherapy against cancer, summarizes the preclinical and clinical advances of CAR-NK cells against both hematological malignancies and solid tumors and confronts current challenges and obstacles of their applications. In addition, this review provides insights into prospective novel approaches that further enhance the efficiency of CAR-NK therapies and highlights potential questions that require to be addressed in the future.

Gene Transduction of Natural Killer Cells for Clinical Application

Autologous T cells expressing chimeric antigen receptor (CAR) have produced a spectacular response in hematological malignancies. This success of cellular therapy has inspired the exploration of the therapeutic potential of other immune cell types. In this regard, natural killer (NK) cells hold great potential as they can identify tumor cells by mechanisms that are different from those used by T cells and have a high cytotoxic capacity. Their capacity to recognize tumors and killing potency can be further enhanced by genetic modification. Our laboratory has developed a clinically adaptable method to manufacture genetically modified NK cells using retroviral vectors in compliance with current good manufacturing practice regulations. Here, we describe relevant technical procedures, including isolation of peripheral blood mononucleated cells from a leukapheresis product, T-cell depletion, stimulation and transduction of NK cells, and preparation of transduced NK cells for infusion.

Perspective of HLA-G Induced Immunosuppression in SARS-CoV-2 Infection

COVID-19, the disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has threatened public health worldwide. Host antiviral immune responses are essential for viral clearance and disease control, however, remarkably decreased immune cell numbers and exhaustion of host cellular immune responses are commonly observed in patients with COVID-19. This is of concern as it is closely associated with disease severity and poor outcomes. Human leukocyte antigen-G (HLA-G) is a ligand for multiple immune inhibitory receptors, whose expression can be upregulated by viral infections. HLA-G/receptor signalling, such as engagement with immunoglobulin-like transcript 2 (ILT-2) or ILT-4, not only inhibit T and natural killer (NK) cell immune responses, dendritic cell (DC) maturation, and B cell antibody production. It also induces regulatory cells such as myeloid-derived suppressive cells (MDSCs), or M2 type macrophages. Moreover, HLA-G interaction with CD8 and killer inhibitory receptor (KIR) 2DL4 can provoke T cell apoptosis and NK cell senescence. In this context, HLA-G can induce profound immune suppression, which favours the escape of SARS-CoV-2 from immune attack. Although detailed knowledge on the clinical relevance of HLA-G in SARS-CoV-2 infection is limited, we herein review the immunopathological aspects of HLA-G/receptor signalling in SARS-CoV-2 infection, which could provide a better understanding of COVID-19 disease progression and identify potential immunointerventions to counteract SARS-CoV-2 infection.

Barriers to Immunotherapy in Ovarian Cancer: Metabolic, Genomic, and Immune Perturbations in the Tumour Microenvironment

A lack of explicit early clinical signs and effective screening measures mean that ovarian cancer (OC) often presents as advanced, incurable disease. While conventional treatment combines maximal cytoreductive surgery and platinum-based chemotherapy, patients frequently develop chemoresistance and disease recurrence. The clinical application of immune checkpoint blockade (ICB) aims to restore anti-cancer T-cell function in the tumour microenvironment (TME). Disappointingly, even though tumour infiltrating lymphocytes are associated with superior survival in OC, ICB has offered limited therapeutic benefits. Herein, we discuss specific TME features that prevent ICB from reaching its full potential, focussing in particular on the challenges created by immune, genomic and metabolic alterations. We explore both recent and current therapeutic strategies aiming to overcome these hurdles, including the synergistic effect of combination treatments with immune-based strategies and review the status quo of current clinical trials aiming to maximise the success of immunotherapy in OC.

The importance of immune checkpoints in immune monitoring: A future paradigm shift in the treatment of cancer

The growth and development of cancer are directly correlated to the suppression of the immune system. A major breakthrough in cancer immunotherapy depends on various mechanisms to detect immunosuppressive factors that inhibit anti-tumor immune responses. Immune checkpoints are expressed on many immune cells such as T-cells, regulatory B cells (Bregs), dendritic cells (DCs), natural killer cells (NKs), regulatory T (Tregs), M2-type macrophages, and myeloid-derived suppressor cells (MDSCs). Immune inhibitory molecules, including CTLA-4, TIM-3, TIGIT, PD-1, and LAG-3, normally inhibit immune responses via negatively regulating immune cell signaling pathways to prevent immune injury. However, the up-regulation of inhibitory immune checkpoints during tumor progression on immune cells suppresses anti-tumor immune responses and promotes immune escape in cancer. It has recently been indicated that cancer cells can up-regulate various pathways of the immune checkpoints. Therefore, targeting immune inhibitory molecules through antibodies or miRNAs is a promising therapeutic strategy and shows favorable results. Immune checkpoint inhibitors (ICIs) are introduced as a new immunotherapy strategy that enhance immune cell-induced antitumor responses in many patients. In this review, we highlighted the function of each immune checkpoint on different immune cells and therapeutic strategies aimed at using monoclonal antibodies and miRNAs against inhibitory receptors. We also discussed current challenges and future strategies for maximizing these FDA-approved immunosuppressants' effectiveness and clinical success in cancer treatment.

Immune Profiling of Cord Blood From Preterm and Term Infants Reveals Distinct Differences in Pro-Inflammatory Responses

Background

Preterm infants are highly vulnerable to infectious disease. While many factors are likely to contribute to this enhanced susceptibility, the immature nature of the preterm immune system is postulated as one key factor.

Methods

In our study, we used high-dimensional flow cytometry and cytokine assays to characterise the immune profiles in 25 preterm (range: 30.4-34.1 weeks gestational age) and 25 term infant (range: 37-40 weeks gestational age) cord blood samples.

Results

We found that preterm infants exhibit reduced frequencies of monocytes, CD56^bright NK cells, CD8+ T-cells, γδ T-cells and an increased frequency of intermediate monocytes, CD4+ T-cells, central memory CD4+ and CD8+ T-cells, Tregs and transitional B-cells compared to term infants. Pro-inflammatory cytokines IL-1β, IL-6 and IL-17A were lower in preterm infants in addition to chemokines IL-8, eotaxin, MIP-1α and MIP-1β. However, IL-15 and MCP-1 were higher in preterm infants.

Conclusion

Overall, we identify key differences in pro-inflammatory immune profiles between preterm and term infants. These findings may help to explain why preterm infants are more susceptible to infectious disease during early life and facilitate the development of targeted interventions to protect this highly vulnerable group.

Alteration of the Immune Microenvironment in HBsAg and HBeAg Dual-Positive Pregnant Women Presenting a High HBV Viral Load

Purpose

The aim of this study was to compare the differences in the immune microenvironment between HBV-infected pregnant women with a high HBV viral load and healthy pregnant women, with an emphasis on T cell subset alteration.

Patients and Methods

We compared the differences of cellular and molecular signatures between HBV-infected and healthy pregnant women by performing single-cell RNA and T cell receptor sequencing of peripheral blood mononuclear cells from 51,836 women in the mid-trimester pregnancy stage. Specific trajectories of the different T clusters throughout the course of T cell differentiation were investigated. Flow cytometry was used to validate the proportion of different T cell subtypes.

Results

We identified nine cellular subtypes and found an increased proportion of effector/memory CD8+ T cells in HBV-infected pregnant women. Both CD4+ and CD8+ effector/memory T cells in HBV-related samples expressed higher levels of metallothionein (MT)-related genes (MT2A, MTIE, MTIF, MTIX), metal ion pathways, and multiple inflammatory responses. Among CD8+ T cell clusters, we identified a particular subset of effector/memory CD8+ T cells (CD8-cluster 2) with MTs as the top-ranking genes, which may be enriched in HBV-related samples. These cells showed an increased clonal expansion in HBV infection. Moreover, we found more active immune responses, according to cellular interaction patterns, between immune cell subsets in HBV-infected samples.

Conclusion

This study shows significant differences between HBV-infected and healthy samples, including cell clusters, dominant gene sets, T cell function, clonal expansion, and V/J gene usage of T cell clonotypes, and identifies a distinct CD8+ T cell cluster with immune-active and antiviral properties. These findings pave the way for a deeper understanding of the impact of HBV infection on the immune microenvironment during pregnancy.

Radioimmunotherapy in Oncology: Overview of the Last Decade Clinical Trials

Simple Summary

Monoclonal antibody-bearing radionuclides have been under clinical investigation over the last two decades for their use in theranostic (diagnostic and therapeutic) applications in cancer. However, despite the numerous trials that have been conducted, only two radioimmunotherapies (RIT) have been approved by the FDA for the targeted therapy of hematologic tumors expressing CD20 antigens. Moreover, RIT applications for solid cancers faced major issues—such as radiotoxicity due to low antibodies penetrance requiring substantial curative dose—where new discoveries concerning antibody engineering or radionuclides are trying to overcome. Here, we performed an overview of the last 11-year clinical trials involving RIT for solid and non-solid cancers conducted either with full antibodies or antibody fragments. We discussed the low-to-moderate efficiency of RIT compared to conventional therapies and described the last advances in clinic for antibodies carriers (F(ab′)₂, Fab′, ScFv). Finally, we discussed about the complexity of RIT as a therapy and depicted both the issues and the prospects of such a strategy.

Abstract

The specific irradiation of tumors with selective radiolabeled antibodies constitutes an attractive therapeutic approach. Consequent preclinical research has been conducted by both biologists to identify pertinent targets and to select corresponding antibodies (mAb) and by radiochemists to radiolabel mAbs. These numerous preclinical investigations have ascertained the therapeutic interest of radioimmunotherapy (RIT) protocols in mice models. Here, we summarize the clinical studies that have been performed the last decade, including clinical trials (phases I, II, and III), prospective and retrospective studies, and cases series. We thereby reported 92 clinical studies. Among them, 62 concern the treatment of hematological malignancies, and 30 concern solid tumors. For hematologic diseases, the analysis was complex due to the high discrepancy of therapeutic strategies (first-line therapy, consolidation, stem cell transplantation conditioning) as well as the high variety of malignancies that were treated. The clinical studies from the last decade failed to expand anti-CD20 RIT indications but confirmed that RIT using radiolabeled anti-CD20 remains a pertinent choice for patients with relapse follicular lymphomas. For solid tumors, the positive benefit of RIT is more mitigated, apart for few malignancies that can be treated locally. Clinical trials also demonstrated the potential of some antibody formats, such as F(ab′)₂, which has already been approved by the China State FDA under the trend name Licartin®. Despite disparate results, mAb fragments are an interesting prospect for the improvement of RIT efficiency as well as for pretargeted strategies that delay the injection of radioactive treatments from the mAb ones.

Engineered Removal of PD-1 From the Surface of CD19 CAR-T Cells Results in Increased Activation and Diminished Survival

CAR-T cell therapy is the most advanced way to treat therapy resistant hematologic cancers, in particular B cell lymphomas and leukemias, with high efficiency. Donor T cells equipped ex vivo with chimeric receptor recognize target tumor cells and kill them using lytic granules. CAR-T cells that recognize CD19 marker of B cells (CD19 CAR-T) are considered the gold standard of CAR-T therapy and are approved by FDA. But in some cases, CD19 CAR-T cell therapy fails due to immune suppressive microenvironment. It is shown that tumor cells upregulate expression of PD-L1 surface molecule that binds and increases level and signal provided by PD-1 receptor on the surface of therapeutic CAR-T cells. Induction of this negative signaling results in functional impairment of cytotoxic program in CAR-T cells. Multiple attempts were made to block PD-1 signaling by reducing binding or surface level of PD-1 in CAR-T cells by various means. In this study we co-expressed CD19-CAR with PD-1-specific VHH domain of anti-PD-1 nanobody to block PD-1/PD-L1 signaling in CD19 CAR-T cells. Unexpectedly, despite increased activation of CAR-T cells with low level of PD-1, these T cells had reduced survival and diminished cytotoxicity. Functional impairment caused by disrupted PD-1 signaling was accompanied by faster maturation and upregulation of exhaustion marker TIGIT in CAR-T cells. We conclude that PD-1 in addition to its direct negative effect on CAR-induced signaling is required for attenuation of strong stimulation leading to cell death and functional exhaustion. These observations suggest that PD-1 downregulation should not be considered as the way to improve the quality of therapeutic CAR-T cells.

Pre-clinical development and molecular characterization of an engineered type 1 regulatory T-cell product suitable for immunotherapy

BACKGROUND AIMS

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is a curative therapeutic approach for many hematological disorders. However, allo-HSCT is frequently accompanied by a serious side effect: graft-versus-host disease (GVHD). The clinical use of allo-HSCT is limited by the inability of current immunosuppressive regimens to adequately control GvHD without impairing the graft-versus-leukemia effect (GvL) conferred by transplanted healthy immune cells. To address this, the authors have developed an engineered type 1 regulatory T-cell product called CD4IL-10 cells. CD4IL-10 cells are obtained through lentiviral transduction, which delivers the human IL10 gene into purified polyclonal CD4+ T cells. CD4IL-10 cells may provide an advantage over standard-of-care immunosuppressants because of the ability to suppress GvHD through continuous secretion of IL-10 and enhance the GvL effect in myeloid malignancies through targeted killing of malignant myeloid cells.

METHODS

Here the authors established a production process aimed at current Good Manufacturing Practice (cGMP) production for CD4IL-10 cells.

RESULTS

The authors demonstrated that the CD4IL-10 cell product maintains the suppressive and cytotoxic functions of previously described CD4IL-10 cells. In addition, RNA sequencing analysis of CD4IL-10 identified novel transcriptome changes, indicating that CD4IL-10 cells primarily upregulate cytotoxicity-related genes. These include four molecules with described roles in CD8+ T and natural killer cell-mediated cytotoxicity: CD244, KLRD1, KLRC1 and FASLG. Finally, it was shown that CD4IL-10 cells upregulate IL-22, which mediates wound healing and tissue repair, particularly in the gut.

CONCLUSIONS

Collectively, these results pave the way toward clinical translation of the cGMP-optimized CD4IL-10 cell product and uncover new molecules that have a role in the clinical application of CD4IL-10 cells.

Engineering the next generation of CAR-NK immunotherapies

Over the past few years, cellular immunotherapy has emerged as a novel treatment option for certain forms of hematologic malignancies with multiple CAR-T therapies now routinely administered in the clinic. The limitations of generating an autologous cell product and the challenges of toxicity with CAR-T cells underscore the need to develop novel cell therapy products that are universal, safe, and potent. Natural killer (NK) cells are part of the innate immune system with 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 proved safe with promising clinical activity. Building on these encouraging clinical responses, research is now actively exploring ways to further enhance CAR-NK cell potency by prolonging in vivo persistence and overcoming mechanisms of functional exhaustion. Besides these strategies to modulate CAR-NK cell intrinsic properties, there are increasing efforts to translate the successes seen in hematologic malignancies to the solid tumor space. This review will provide an overview on current trends and evolving concepts to genetically engineer the next generation of CAR-NK therapies. Emphasis will be placed on innovative multiplexed engineering approaches including CRISPR/Cas9 to overcome CAR-NK functional exhaustion and reprogram immune cell metabolism for enhanced potency.

NKG2A is a late immune checkpoint on CD8 T cells and marks repeated stimulation and cell division

The surface inhibitory receptor NKG2A forms heterodimers with the invariant CD94 chain and is expressed on a subset of activated CD8 T cells. As antibodies to block NKG2A are currently tested in several efficacy trials for different tumor indications, it is important to characterize the NKG2A⁺ CD8 T cell population in the context of other inhibitory receptors. Here we used a well‐controlled culture system to study the kinetics of inhibitory receptor expression. Naïve mouse CD8 T cells were synchronously and repeatedly activated by artificial antigen presenting cells in the presence of the homeostatic cytokine IL‐7. The results revealed NKG2A as a late inhibitory receptor, expressed after repeated cognate antigen stimulations. In contrast, the expression of PD‐1, TIGIT and LAG‐3 was rapidly induced, hours after first contact and subsequently down regulated during each resting phase. This late, but stable expression kinetics of NKG2A was most similar to that of TIM‐3 and CD39. Importantly, single‐cell transcriptomics of human tumor‐infiltrating lymphocytes (TILs) showed indeed that these receptors were often coexpressed by the same CD8 T cell cluster. Furthermore, NKG2A expression was associated with cell division and was promoted by TGF‐β in vitro, although TGF‐β signaling was not necessary in a mouse tumor model in vivo. In summary, our data show that PD‐1 reflects recent TCR triggering, but that NKG2A is induced after repeated antigen stimulations and represents a late inhibitory receptor. Together with TIM‐3 and CD39, NKG2A might thus mark actively dividing tumor‐specific TILs.

The Biological Role and Therapeutic Potential of NK Cells in Hematological and Solid Tumors

NK cells are an attractive target for cancer immunotherapy due to their potent antitumor activity. The main advantage of using NK cells as cytotoxic effectors over T cells is a reduced risk of graft versus host disease. At present, several variants of NK-cell-based therapies are undergoing clinical trials and show considerable effectiveness for hematological tumors. In these types of cancers, the immune cells themselves often undergo malignant transformation, which determines the features of the disease. In contrast, the current use of NK cells as therapeutic agents for the treatment of solid tumors is much less promising. Most studies are at the stage of preclinical investigation, but few progress to clinical trials. Low efficiency of NK cell migration and functional activity in the tumor environment are currently considered the major barriers to NK cell anti-tumor therapies. Various therapeutic combinations, genetic engineering methods, alternative sources for obtaining NK cells, and other techniques are aiming at the development of promising NK cell anticancer therapies, regardless of tumorigenesis. In this review, we compare the role of NK cells in the pathogenesis of hematological and solid tumors and discuss current prospects of NK-cell-based therapy for hematological and solid tumors.

Chimeric Antigen Receptor-Engineered Natural Killer (CAR NK) Cells in Cancer Treatment; Recent Advances and Future Prospects

Natural Killer (NK) cells are critical members of the innate immunity lymphocytes and have a critical role in host defense against malignant cells. Adoptive cell therapy (ACT) using chimeric antigen receptor (CAR) redirects the specificity of the immune cell against a target-specific antigen. ACT has recently created an outstanding opportunity for cancer treatment. Unlike CAR-armored T cells which hadnsome shortcomings as the CAR-receiving construct, Major histocompatibility complex (MHC)-independency, shorter lifespan, the potential to produce an off-the-shelf immune product, and potent anti-tumor properties of the NK cells has introduced NK cells as a potent alternative target for expression of CAR. Here, we aim to provide an updated overview on the current improvements in CAR NK design and immunobiology and describe the potential of CAR-modified NK cells as an alternative “off-the-shelf” carrier of CAR. We also provide lists for the sources of NK cells in the process of CAR NK cell production, different methods for transduction of the CAR genetic sequence to NK cells, the differences between CAR T and CAR NK, and CAR NK-targeted tumor antigens in current studies. Additionally, we provide data on recently published preclinical and clinical studies of CAR NK therapy and a list of finished and ongoing clinical trials. For achieving CAR NK products with higher efficacy and safety, we discuss current challenges in transduction and expansion of CAR NK cells, CAR NK therapy side effects, and challenges that limit the optimal efficacy of CAR NK cells and recommend possible solutions to enhance the persistence, function, safety, and efficacy of CAR NK cells with a special focus on solid tumors.

Targeting immune dysfunction in aging

Human aging is a multifactorial phenomenon that affects numerous organ systems and cellular processes, with the immune system being one of the most dysregulated. Immunosenescence, the gradual deterioration of the immune system, and inflammaging, a chronic inflammatory state that persists in the elderly, are among the plethora of immune changes that occur during aging. Almost all populations of immune cells change with age in terms of numbers and/or activity. These alterations are in general highly detrimental, resulting in an increased susceptibility to infections, reduced healing abilities, and altered homeostasis that promote the emergence of age-associated diseases such as cancer, diabetes, and other diseases associated with inflammation. Thanks to recent developments, several strategies have been proposed to target central immunological processes or specific immune subpopulations affected by aging. These therapeutic approaches could soon be applied in the clinic to slow down or even reverse specific age-induced immune changes in order to rejuvenate the immune system and prevent or reduce the impact of various diseases. Due to its systemic nature and interconnection with all the other systems in the body, the immune system is an attractive target for aging intervention because relatively targeted modifications to a small set of cells have the potential to improve the health of multiple organ systems. Therefore, anti-aging immune targeting therapies could represent a potent approach for improving healthspan. Here, we review aging changes in the major components of the immune system, we summarize the current immune-targeting therapeutic approaches in the context of aging and discuss the future directions in the field of immune rejuvenation.

Natural killer (NK) cell-based immunotherapies and the many faces of NK cell memory: A look into how nanoparticles enhance NK cell activity

Natural killer (NK) cells are lymphocytes able to exert potent antitumor and antiviral functions by different means. Besides their classification as innate lymphoid cells (ILCs), NK cells exhibit memory-like and memory responses after cytokine preactivation, viral infections and hapten exposure. Multiple NK cell-based immunotherapies have been developed and are currently being tested, including the possibility to translate the NK cell memory responses into the clinic. Nevertheless, still there is a need to improve these therapies, especially for the treatment of solid tumors, and nanotechnology represents an attractive option to increase NK cell effector functions against transformed cells. In this article, we review the basis of NK cell activity, the diversity of the NK cell memory responses and the current NK cell-based immunotherapies that are being used in the clinic. Furthermore, we take a look into nanotechnology-based strategies targeting NK cells to modulate their responses for effective immunotherapy.

Bi-specific and Tri-specific NK Cell Engagers: The New Avenue of Targeted NK Cell Immunotherapy

Natural killer (NK) cell-mediated cancer immunotherapy has grown significantly over the past two decades. More recently, multi-specific engagers have been developed as cancer therapeutics to effectively arm endogenous NK cells to more potently induce specific cytolytic responses against tumor targets. This review explores the bi- and tri-specific NK/tumor engagers that are emerging as a new generation of immunotherapeutics. These molecules vary in configuration, but they typically have small molecular weights and domains that engage specific tumor antigens and NK cell-activating receptors such as CD16, NKp30, NKp46, and NKG2D. They have demonstrated compelling potential in boosting NK cell cytotoxicity against specific tumor targets. This highly adaptable off-the-shelf platform, which in some formats also integrates cytokines, is poised to revolutionize targeted NK cell immunotherapy, either as a monotherapy or in combination with other effective anti-cancer therapies.

High-grade serous ovarian tumor cells modulate NK cell function to create an immune-tolerant microenvironment

Tubo-ovarian high-grade serous carcinoma (HGSC) is unresponsive to immune checkpoint blockade despite significant frequencies of exhausted T cells. Here we apply mass cytometry and uncover decidual-like natural killer (dl-NK) cell subpopulations (CD56+CD9+CXCR3+KIR+CD3-CD16-) in newly diagnosed HGSC samples that correlate with both tumor and transitioning epithelial-mesenchymal cell abundance. We show different combinatorial expression patterns of ligands for activating and inhibitory NK receptors within three HGSC tumor compartments: epithelial (E), transitioning epithelial-mesenchymal (EV), and mesenchymal (vimentin expressing [V]), with a more inhibitory ligand phenotype in V cells. In cocultures, NK-92 natural killer cells acquire CD9 from HGSC tumor cells by trogocytosis, resulting in reduced anti-tumor cytokine production and cytotoxicity. Cytotoxicity in these cocultures is restored with a CD9-blocking antibody or CD9 CRISPR knockout, thereby identifying mechanisms of immune suppression in HGSC. CD9 is widely expressed in HGSC tumors and so represents an important new therapeutic target with immediate relevance for NK immunotherapy.

DDX39 as a predictor of clinical prognosis and immune checkpoint therapy efficacy in patients with clear cell renal cell carcinoma

DEAD-box protein 39 (DDX39) has been demonstrated to be a tumorigenic gene in multiple tumor types, but its role in the progression and immune microenvironment of clear cell renal cell cancer (ccRCC) remains unclear. The aim of the present study was to investigate the role of DDX39 in the ccRCC tumor progression, immune microenvironment and efficacy of immune checkpoint therapy.

The DDX39 expression level was first detected in tumors in the public data and then verified in ccRCC samples from Changzheng Hospital. The prognostic value of DDX39 expression was assessed in the Cancer Genome Atlas (TCGA) and ccRCC patients from Changhai Hospital. The role of DDX39 in promoting ccRCC was analyzed by bioinformatic analysis and in vitro experiments. The association between DDX39 expression and immune cell infiltration and immune inhibitory markers was analyzed, and its value in predicting the immune checkpoint therapy efficacy in ccRCC were evaluated in the public database. DDX39 expression was elevated in Oncomine, GEO and TCGA ccRCC databases, as well as in Changzheng ccRCC samples. In TCGA ccRCC patients, increased DDX39 expression predicted worse overall survival (OS) (p<0.0001) and progression-free interval (PFI) (p<0.0001), and was shown as an independent predictive factor for OS (p=0.002). These findings were consistent with those from Changhai ccRCC patients. In addition, GO and GSEA analysis identified DDX39 as a pro-ccRCC gene. In vitro experiments confirmed the role of DDX39 in promoting ccRCC cell. Finally, DDX39 was found to be positively correlated with a variety of immune inhibitory markers, and could predict the adverse efficacy of immune checkpoint therapy in TIDE analysis. In conclusion, Increased DDX39 in ccRCC patients predicted worse clinical prognosis, promoted ccRCC cell proliferation, migration and invasion, and also predicted adverse efficacy of immune checkpoint therapy.