Natural killer cells produce T cell-recruiting chemokines in response to antibody-coated tumor cells

Adoptive NK cell therapy: a potential revolutionary approach in longevity therapeutics

The aging process intricately involves immune system dynamics, with a crucial role in managing senescent cells (SNCs) and their senescence-associated secretory phenotypes (SASPs). Unfortunately, immunosenescence, a progressively dysregulated immunity with age, hampers effective SNC elimination, leading to accumulation, coupled with the release of SASPs, which, in turn, inhibits immunity and heightened susceptibility to aging-associated diseases (AADs). Natural killer (NK) cells, integral to the innate immune system, play a pivotal role in addressing SNCs swiftly. These cells also coordinate with other components of both innate and adaptive immunity to surveil and eliminate these cells. Accordingly, preserving NK cell function during aging is crucial for evading AADs and promoting healthy aging. Alternatively, NK-cell-based therapies present promising avenues for addressing the challenges associated with aging. Notable, recent studies in adoptive NK cell therapy have shown promise in rejuvenating immunosenescence, eliminating SNCs, and alleviating SASPs. This progress provides the proof-concept of adoptive NK cell therapy for senotherapy and holds promise as an emerging revolution in longevity therapeutics.

Prognostic and Predictive Potential of CCL5 Expression in Muscle-Invasive Bladder Cancer Patients

Bladder cancer (BC) is the 12th most commonly diagnosed cancer worldwide. Although there are several well-established molecular and immunological classifications, prognostic and predictive markers for tumor cells and immune cells are still needed. Using a tissue microarray, we analyzed the expression of the chemokine CC motif ligand 5 (CCL5) by immunohistochemistry (IHC) in 175 muscle-invasive BC samples. The application of a single cutoff for the staining status of tumor cells (TCs; positive vs. negative) and immune cells (ICs; positive vs. negative) revealed 75 patients (42.9%) and 123 patients (70.3%) with CCL5-positive TCs or ICs, respectively. IHC results were associated with prognostic and predictive data. Multivariate Cox regression analysis revealed that positive CCL5 staining in TCs was associated with significantly shorter disease-specific survival (DSS; RR = 1.51; p = 0.047), but CCL5-negative ICs were associated with significantly shorter overall survival (OS; RR = 1.66; p = 0.005), DSS (RR = 2.02; p = 0.001) and recurrence-free survival (RFS; RR = 1.94; p = 0.002). Adjuvant chemotherapy was favorable for patients with CCL5-negative ICs for OS (RR = 0.30; p = 0.006), DSS (RR = 0.36; p = 0.022) and RFS (RR = 0.41; p = 0.046) but not for patients with CCL5-positive ICs, except in the subgroup of N1 + N2 patients, where it was associated with better OS. We suggest that CCL5 expression can be a prognostic and predictive marker for muscle-invasive bladder cancer patients.

A new perspective on hematological malignancies: m6A modification in immune microenvironment

Immunotherapy for hematological malignancies is a rapidly advancing field that has gained momentum in recent years, primarily encompassing chimeric antigen receptor T-cell (CAR-T) therapies, immune checkpoint inhibitors, and other modalities. However, its clinical efficacy remains limited, and drug resistance poses a significant challenge. Therefore, novel immunotherapeutic targets and agents need to be identified. Recently, N6-methyladenosine (m6A), the most prevalent RNA epitope modification, has emerged as a pivotal factor in various malignancies. Reportedly, m6A mutations influence the immunological microenvironment of hematological malignancies, leading to immune evasion and compromising the anti-tumor immune response in hematological malignancies. In this review, we comprehensively summarize the roles of the currently identified m6A modifications in various hematological malignancies, with a particular focus on their impact on the immune microenvironment. Additionally, we provide an overview of the research progress made in developing m6A-targeted drugs for hematological tumor therapy, to offer novel clinical insights.

PM21-particle stimulation augmented with cytokines enhances NK cell expansion and confers memory-like characteristics with enhanced survival

NK cell therapeutics have gained significant attention as a potential cancer treatment. Towards therapeutic use, NK cells need to be activated and expanded to attain high potency and large quantities for an effective dosage. This is typically done by ex vivo stimulation with cytokines to enhance functionality or expansion for 10-14 days to increase both their activity and quantity. Attaining a robust methodology to produce large doses of potent NK cells for an off-the-shelf product is highly desirable. Notably, past reports have shown that stimulating NK cells with IL-12, IL-15, and IL-18 endows them with memory-like properties, better anti-tumor activity, and persistence. While this approach produces NK cells with clinically favorable characteristics supported by encouraging early results for the treatment of hematological malignancies, its limited scalability, variability in initial doses, and the necessity for patient-specific production hinder its broader application. In this study, stimulation of NK cells with PM21-particles derived from K562-41BBL-mbIL21 cells was combined with memory-like induction using cytokines IL-12, IL-15, and IL-18 to produce NK cells with enhanced anti-tumor function. The use of cytokines combined with PM21-particles (cytokine and particle, CAP) significantly enhanced NK cell expansion, achieving a remarkable 8,200-fold in 14 days. Mechanistically, this significant improvement over expansion with PM21-particles alone was due to the upregulation of receptors for key stimulating ligands (4-1BBL and IL-2), resulting in a synergy that drives substantial NK cell growth, showcasing the potential for more effective therapeutic applications. The therapeutic potential of CAP-NK cells was demonstrated by the enhanced metabolic fitness, persistence, and anti-tumor function both in vitro and in vivo. Finally, CAP-NK cells were amenable to current technologies used in developing therapeutic NK cell products, including CRISPR/Cas9-based techniques to generate a triple-gene knockout or a gene knock-in. Taken together, these data demonstrate that the addition of cytokines enhanced the already effective method of ex vivo generation of therapeutic NK cells with PM21-particles, yielding a superior NK cell product for manufacturing efficiency and potential therapeutic applications.

The Role of Fc Receptors in the Innate Immune System of Flounders Purported to Be Homologs of FcγRII and FcγRIII

FcγR is a significant opsonin receptor located on the surface of immune cells, playing a crucial role in Ab-dependent cell-mediated immunity. Our previous work revealed opposite expression trends of FcγRII and FcγRIII in flounder mIgM+ B lymphocytes after phagocytosis of antiserum-opsonized Edwardsiella tarda. This observation suggests that FcγRII and FcγRIII might serve distinct functions in Ig-opsonized immune responses. In this study, we prepared rFcγRIII as well as its corresponding Abs to investigate the potential roles of FcγRII and FcγRIII in the Ab-dependent immune response of IgM+ B cells. Our findings indicate that, unlike FcγRII, FcγRIII does not participate in Ab-dependent cellular phagocytosis. Instead, it is involved in cytokine production and bacterial killing in mIgM+ B lymphocytes. Additionally, we identified platelet-derived ADAM17 as a key factor in regulating FcγRIII shedding and cytokine release in mIgM+ B lymphocytes. These results elucidate the functions of FcγRII and FcγRIII in the innate immunology of mIgM+ B lymphocytes and contribute to an improved understanding of the regulatory roles of FcγRs in the phagocytosis of teleost B lymphocytes.

Cereblon-Targeting Ligase Degraders in Myeloma: Mechanisms of Action and Resistance

Cereblon-targeting degraders, including immunomodulatory imide drugs lenalidomide and pomalidomide alongside cereblon E3 ligase modulators like iberdomide and mezigdomide, have demonstrated significant anti-myeloma effects. These drugs play a crucial role in diverse therapeutic approaches for multiple myeloma (MM), emphasizing their therapeutic importance across various disease stages. Despite their evident efficacy, approximately 5% to 10% of MM patients exhibit primary resistance to lenalidomide, and resistance commonly develops over time. Understanding the intricate mechanisms of action and resistance to this drug class becomes imperative for refining and advancing novel therapeutic combinations.

Efbalropendekin Alfa enhances human natural killer cell cytotoxicity against tumor cell lines in vitro

IL-15 has shown preclinical activity by enhancing the functional maturation of natural killer (NK) cells. Clinical evaluation of the potential anticancer activity of most cytokines, including IL-15, has been limited by low tolerability and rapid in vivo clearance. Efbalropendekin Alfa (XmAb24306) is a soluble IL15/IL15-receptor alpha heterodimer complex fused to a half-life extended Fc domain (IL15/IL15Rα-Fc), engineered with mutations to reduce IL-15 affinity for CD122. Reduced affinity drives lower potency, leading to prolonged pharmacodynamic response in cynomolgus monkeys. We show that in vitro, human NK cells treated with XmAb24306 demonstrate enhanced cytotoxicity against various tumor cell lines. XmAb24306-treated NK cells also exhibit enhanced killing of 3D colorectal cancer spheroids. Daratumumab (dara), a monoclonal antibody (mAb) that targets CD38 results in antibody-dependent cellular cytotoxicity (ADCC) of both multiple myeloma (MM) cells and NK cells. Addition of XmAb24306 increases dara-mediated NK cell ADCC against various MM cell lines in vitro. Because NK cells express CD38, XmAb24306 increases dara-mediated NK cell fratricide, but overall does not negatively impact the ADCC activity against a MM cell line likely due to increased NK cell activity of the surviving cells. These data show that XmAb24306 increases direct and ADCC-mediated human NK cell cytotoxicity in vitro.

Targeting natural killer cells: from basic biology to clinical application in hematologic malignancies

Natural killer (NK) cell belongs to innate lymphoid cell family that contributes to host immunosurveillance and defense without pre-immunization. Emerging studies have sought to understand the underlying mechanism behind NK cell dysfunction in tumor environments, and provide numerous novel therapeutic targets for tumor treatment. Strategies to enhance functional activities of NK cell have exhibited promising efficacy and favorable tolerance in clinical treatment of tumor patients, such as immune checkpoint blockade (ICB), chimeric antigen receptor NK (CAR-NK) cell, and bi/trispecific killer cell engager (BiKE/TriKE). Immunotherapy targeting NK cell provides remarkable advantages compared to T cell therapy, including a decreased rate of graft versus-host disease (GvHD) and neurotoxicity. Nevertheless, advanced details on how to support the maintenance and function of NK cell to obtain better response rate and longer duration still remain to be elucidated. This review systematically summarizes the profound role of NK cells in tumor development, highlights up-to-date advances and current challenges of therapy targeting NK cell in the clinical treatment of hematologic malignancies.

Study of alloferon, a novel immunomodulatory antimicrobial peptide (AMP), and its analogues

Antimicrobial peptides (AMPs) are widely distributed throughout the biosphere and represent a class of conserved peptide molecules with intrinsic antimicrobial properties. Their broad-spectrum antimicrobial activity and low risk to induce resistance have led to increased interest in AMPs as potential alternatives to traditional antibiotics. Among the AMPs, alloferon has been addressed due to its immunomodulatory properties that augment both innate and adaptive immune responses against various pathogens. Alloferon and its analogues have demonstrated pharmaceutical potential through their ability to enhance Natural Killer (NK) cell cytotoxicity and stimulate interferon (IFN) synthesis in both mouse and human models. Additionally, they have shown promise in augmenting antiviral and antitumor activities in mice. In this article, we provide a comprehensive review of the biological effects of alloferon and its analogues, incorporating our own research findings as well. These insights may contribute to a deeper understanding of the therapeutic potential of these novel AMPs.

Unveiling the role of NK cells, NKT-like cells, and γδ cells in pathogenesis of type 1 reactions in leprosy

Leprosy is a disease with spectral clinical manifestations along with two types of reactions, type 1 reaction (T1R) and type 2 reaction (T2R). T1R especially occurs because of the defensive upgradation of cell-mediated immunity (CMI) to M. leprae antigens. T1R is the main cause of disability in leprosy. The role of conventional adaptive T cells has been well studied to understand T1R. A comprehensive understanding of the role of unconventional T cells in the manifestation of inflammation during T1R is crucial and has not been studied. In our study, we found significantly higher plasma levels of TNFα, IL1β, IL17, and IP10 in T1R when compared to non-reaction (NR). Gene expression for cytokines in blood circulation by qPCR showed significantly higher expression of IFNγ, IP10, TNFα, IL6, IL17A and chemokines CCL3, CCR1, CCR5, and CXCR3 in T1R as compared to NR. Frequencies of NKT-like cells (48.7 %) and NK cells (22.3 %) were found significantly higher in T1R in comparison to NR (36.9 %, 18.3 %, respectively) (p = 0.0001). Significantly lower levels of γδT cells (3.32 %) were observed in T1R in comparison to NR (5.16 %). The present study has provided evidence for the first time on the role of plausible unconventional T cells in the immunopathogenesis of T1R in leprosy.

Effector and cytolytic function of natural killer cells in anticancer immunity

Adaptive immune cells play an important role in mounting antigen-specific antitumor immunity. The contribution of innate immune cells such as monocytes, macrophages, natural killer (NK) cells, dendritic cells, and gamma-delta T cells is well studied in cancer immunology. NK cells are innate lymphoid cells that show effector and regulatory function in a contact-dependent and contact-independent manner. The cytotoxic function of NK cells plays an important role in killing the infected and transformed host cells and controlling infection and tumor growth. However, several studies have also ascribed the role of NK cells in inducing pathophysiology in autoimmune diseases, promoting immune tolerance in the uterus, and antitumor function in the tumor microenvironment. We discuss the fundamentals of NK cell biology, its distribution in different organs, cellular and molecular interactions, and its cytotoxic and noncytotoxic functions in cancer biology. We also highlight the use of NK cell-based adoptive cellular therapy in cancer.

Single-cell functional genomics reveals determinants of sensitivity and resistance to natural killer cells in blood cancers

Cancer cells can evade natural killer (NK) cell activity, thereby limiting anti-tumor immunity. To reveal genetic determinants of susceptibility to NK cell activity, we examined interacting NK cells and blood cancer cells using single-cell and genome-scale functional genomics screens. Interaction of NK and cancer cells induced distinct activation and type I interferon (IFN) states in both cell types depending on the cancer cell lineage and molecular phenotype, ranging from more sensitive myeloid to less sensitive B-lymphoid cancers. CRISPR screens in cancer cells uncovered genes regulating sensitivity and resistance to NK cell-mediated killing, including adhesion-related glycoproteins, protein fucosylation genes, and transcriptional regulators, in addition to confirming the importance of antigen presentation and death receptor signaling pathways. CRISPR screens with a single-cell transcriptomic readout provided insight into underlying mechanisms, including regulation of IFN-γ signaling in cancer cells and NK cell activation states. Our findings highlight the diversity of mechanisms influencing NK cell susceptibility across different cancers and provide a resource for NK cell-based therapies.

Knockout of the inhibitory receptor TIGIT enhances the antitumor response of ex vivo expanded NK cells and prevents fratricide with therapeutic Fc-active TIGIT antibodies

BACKGROUND

Inhibitory receptor T-cell Immunoreceptor with Ig and ITIM domains (TIGIT) expressed by Natural Killer (NK) and T cells regulates cancer immunity and has been touted as the next frontier in the development of cancer immunotherapeutics. Although early results of anti-TIGIT and its combinations with antiprogrammed death-ligand 1 were highly exciting, results from an interim analysis of phase III trials are disappointing. With mixed results, there is a need to understand the effects of therapeutic anti-TIGIT on the TIGIT+ immune cells to support its clinical use. Most of the TIGIT antibodies in development have an Fc-active domain, which binds to Fc receptors on effector cells. In mouse models, Fc-active anti-TIGIT induced superior immunity, while Fc receptor engagement was required for its efficacy. NK-cell depletion compromised the antitumor immunity of anti-TIGIT indicating the essential role of NK cells in the efficacy of anti-TIGIT. Since NK cells express TIGIT and Fc-receptor CD16, Fc-active anti-TIGIT may deplete NK cells via fratricide, which has not been studied.

METHODS

CRISPR-Cas9-based TIGIT knockout (KO) was performed in expanded NK cells. Phenotypic and transcriptomic properties of TIGIT KO and wild-type (WT) NK cells were compared with flow cytometry, CyTOF, and RNA sequencing. The effect of TIGIT KO on NK-cell cytotoxicity was determined by calcein-AM release and live cell imaging-based cytotoxicity assays. The metabolic properties of TIGIT KO and WT NK cells were compared with a Seahorse analyzer. The effect of the Fc-component of anti-TIGIT on NK-cell fratricide was determined by co-culturing WT and TIGIT KO NK cells with Fc-active and Fc-inactive anti-TIGIT.

RESULTS

TIGIT KO increased the cytotoxicity of NK cells against multiple cancer cell lines including spheroids. TIGIT KO NK cells upregulated mTOR complex 1 (mTORC1) signaling and had better metabolic fitness with an increased basal glycolytic rate when co-cultured with cancer cells compared with WT NK cells. Importantly, TIGIT KO prevented NK-cell fratricide when combined with Fc-active anti-TIGIT.

CONCLUSIONS

TIGIT KO in ex vivo expanded NK cells increased their cytotoxicity and metabolic fitness and prevented NK-cell fratricide when combined with Fc-active anti-TIGIT antibodies. These fratricide-resistant TIGIT KO NK cells have therapeutic potential alone or in combination with Fc-active anti-TIGIT antibodies to enhance their efficacy.

NK Cell Therapeutics for Hematologic Malignancies: from Potential to Fruition

PURPOSE OF REVIEW

The current review focuses on the preclinical development and clinical advances of natural killer (NK) cell therapeutics for hematologic malignancies and offers perspective on the unmet challenges that will direct future discovery in the field.

RECENT FINDINGS

Approaches to improve or re-direct NK cell anti-tumor functions against hematologic malignancies have included transgenic expression of chimeric antigen receptors (CARs), administration of NK cell engagers including BiKEs and TriKEs that enhance antibody-dependent cellular cytotoxicity (ADCC) by co-engaging NK cell CD16 and antigens on tumors, incorporation of a non-cleavable CD16 that results in enhanced ADCC, use of induced memory-like NK cells alone or in combination with CARs, and blockade of NK immune checkpoints to enhance NK cytotoxicity. Recently reported and ongoing clinical trials support the feasibility and safety of these approaches. NK cell-based therapeutic strategies hold great promise as cost-effective, off-the-shelf cell therapies for patients with relapsed and refractory hematologic diseases.

Challenges and solutions for therapeutic TCR-based agents

Recent development of methods to discover and engineer therapeutic T-cell receptors (TCRs) or antibody mimics of TCRs, and to understand their immunology and pharmacology, lag two decades behind therapeutic antibodies. Yet we have every expectation that TCR-based agents will be similarly important contributors to the treatment of a variety of medical conditions, especially cancers. TCR engineered cells, soluble TCRs and their derivatives, TCR-mimic antibodies, and TCR-based CAR T cells promise the possibility of highly specific drugs that can expand the scope of immunologic agents to recognize intracellular targets, including mutated proteins and undruggable transcription factors, not accessible by traditional antibodies. Hurdles exist regarding discovery, specificity, pharmacokinetics, and best modality of use that will need to be overcome before the full potential of TCR-based agents is achieved. HLA restriction may limit each agent to patient subpopulations and off-target reactivities remain important barriers to widespread development and use of these new agents. In this review we discuss the unique opportunities for these new classes of drugs, describe their unique antigenic targets, compare them to traditional antibody therapeutics and CAR T cells, and review the various obstacles that must be overcome before full application of these drugs can be realized.

A chimeric antigen receptor uniquely recognizing MICA/B stress proteins provides an effective approach to target solid tumors

BACKGROUND

The advent of chimeric antigen receptor (CAR) T cell therapies has transformed the treatment of hematological malignancies; however, broader therapeutic success of CAR T cells has been limited in solid tumors because of their frequently heterogeneous composition. Stress proteins in the MICA and MICB (MICA/B) family are broadly expressed by tumor cells following DNA damage but are rapidly shed to evade immune detection.

METHODS

We have developed a novel CAR targeting the conserved α3 domain of MICA/B (3MICA/B CAR) and incorporated it into a multiplexed-engineered induced pluripotent stem cell (iPSC)-derived natural killer (NK) cell (3MICA/B CAR iNK) that expressed a shedding-resistant form of the CD16 Fc receptor to enable tumor recognition through two major targeting receptors.

FINDINGS

We demonstrated that 3MICA/B CAR mitigates MICA/B shedding and inhibition via soluble MICA/B while simultaneously exhibiting antigen-specific anti-tumor reactivity across an expansive library of human cancer cell lines. Pre-clinical assessment of 3MICA/B CAR iNK cells demonstrated potent antigen-specific in vivo cytolytic activity against both solid and hematological xenograft models, which was further enhanced in combination with tumor-targeted therapeutic antibodies that activate the CD16 Fc receptor.

CONCLUSIONS

Our work demonstrated 3MICA/B CAR iNK cells to be a promising multi-antigen-targeting cancer immunotherapy approach intended for solid tumors.

FUNDING

Funded by Fate Therapeutics and NIH (R01CA238039).

TIGIT Expression on Activated NK Cells Correlates with Greater Anti-Tumor Activity but Promotes Functional Decline upon Lung Cancer Exposure: Implications for Adoptive Cell Therapy and TIGIT-Targeted Therapies

Treatments targeting TIGIT have gained a lot of attention due to strong preclinical and early clinical results, particularly with anti-PD-(L)1 therapeutics. However, this combination has failed to meet progression-free survival endpoints in phase III trials. Most of our understanding of TIGIT comes from studies of T cell function. Yet, this inhibitory receptor is often upregulated to the same, or higher, extent on NK cells in cancers. Studies in murine models have demonstrated that TIGIT inhibits NK cells and promotes exhaustion, with its effects on tumor control also being dependent on NK cells. However, there are limited studies assessing the role of TIGIT on the function of human NK cells (hNK), particularly in lung cancer. Most studies used NK cell lines or tested TIGIT blockade to reactivate exhausted cells obtained from cancer patients. For therapeutic advancement, a better understanding of TIGIT in the context of activated hNK cells is crucial, which is different than exhausted NK cells, and critical in the context of adoptive NK cell therapeutics that may be combined with TIGIT blockade. In this study, the effect of TIGIT blockade on the anti-tumor activities of human ex vivo-expanded NK cells was evaluated in vitro in the context of lung cancer. TIGIT expression was higher on activated and/or expanded NK cells compared to resting NK cells. More TIGIT⁺ NK cells expressed major activating receptors and exerted anti-tumor response as compared to TIGIT^- cells, indicating that NK cells with greater anti-tumor function express more TIGIT. However, long-term TIGIT engagement upon exposure to PVR⁺ tumors downregulated the cytotoxic function of expanded NK cells while the inclusion of TIGIT blockade increased cytotoxicity, restored the effector functions against PVR-positive targets, and upregulated immune inflammation-related gene sets. These combined results indicate that TIGIT blockade can preserve the activation state of NK cells during exposure to PVR⁺ tumors. These results support the notion that a functional NK cell compartment is critical for anti-tumor response and anti-TIGIT/adoptive NK cell combinations have the potential to improve outcomes.

The natural killer cell immunotherapy platform: an overview of the landscape of clinical trials in liquid and solid tumors

The translation of natural killer (NK) cells to the treatment of malignant disease has made significant progress in the last few decades. With a variety of available sources and improvements in both in vitro and in vivo NK cell expansion, the NK cell immunotherapy platform has come into its own. The enormous effort continues to further optimize this platform, including ways to enhance NK cell persistence, trafficking to the tumor microenvironment, and cytotoxicity. As this effort bears fruit, it is translated into a plethora of clinical trials in patients with advanced malignancies. The adoptive transfer of NK cells, either as a standalone therapy or in combination with other immunotherapies, has been applied for the treatment of both liquid and solid tumors, with numerous early-phase trials showing promising results. This review aims to summarize the key advantages of NK cell immunotherapy, highlight several of the current approaches being taken for its optimization, and give an overview of the landscape of clinical trials translating this platform into clinic.

Human natural killer cells: Form, function, and development

Human natural killer (NK) cells are innate lymphoid cells that mediate important effector functions in the control of viral infection and malignancy. Their ability to distinguish "self" from "nonself" and lyse virally infected and tumorigenic cells through germline-encoded receptors makes them important players in maintaining human health and a powerful tool for immunotherapeutic applications and fighting disease. This review introduces our current understanding of NK cell biology, including key facets of NK cell differentiation and the acquisition and execution of NK cell effector function. Further, it addresses the clinical relevance of NK cells in both primary immunodeficiency and immunotherapy. It is intended to provide an up-to-date and comprehensive overview of this important and interesting innate immune effector cell subset.

Reactivation of natural killer cells with monoclonal antibodies in the microenvironment of malignant neoplasms

Natural killer cells are critical players in the antitumor immune response due to their ability to destroy target cells through cytotoxic activity and other means. However, this response is inhibited in the tumor microenvironment, where a crippling hypoxic environment and several inhibitory molecules bind to NK cells to trigger an anergic state. Inhibitory receptors such as PD-1, NK2GA, KIR, TIGIT, and LAG-3 have been associated with inhibition of NK cells in multiple cancer types. Binding to these receptors leads to loss of cytotoxicity, lower proliferation and metabolic rates, and even apoptosis. While these receptors are important for avoiding auto-immunity, in a pathological setting like malignant neoplasms they are disadvantageous for the individual's immune system to combat cancer cells. The use of monoclonal antibodies to block these receptors contributes to cancer therapy by preventing the inhibition of NK cells. In this review, the impact of NK cell inhibition and activation on cancer therapy was summarized and an overview of the blockade of inhibitory pathways by monoclonal antibodies was provided.

Targeting immune checkpoints: how to use natural killer cells for fighting against solid tumors

Natural killer (NK) cells are unique innate immune cells that mediate anti-viral and anti-tumor responses. Thus, they might hold great potential for cancer immunotherapy. NK cell adoptive immunotherapy in humans has shown modest efficacy. In particular, it has failed to demonstrate therapeutic efficiency in the treatment of solid tumors, possibly due in part to the immunosuppressive tumor microenvironment (TME), which reduces NK cell immunotherapy's efficiencies. It is known that immune checkpoints play a prominent role in creating an immunosuppressive TME, leading to NK cell exhaustion and tumor immune escape. Therefore, NK cells must be reversed from their dysfunctional status and increased in their effector roles in order to improve the efficiency of cancer immunotherapy. Blockade of immune checkpoints can not only rescue NK cells from exhaustion but also augment their robust anti-tumor activity. In this review, we discussed immune checkpoint blockade strategies with a focus on chimeric antigen receptor (CAR)-NK cells to redirect NK cells to cancer cells in the treatment of solid tumors.

Inflammatory-driven NK cell maturation and its impact on pathology

NK cells are innate lymphocytes involved in a large variety of contexts and are crucial in the immunity to intracellular pathogens as well as cancer due to their ability to kill infected or malignant cells. Thus, they harbor a strong potential for clinical and therapeutic use. NK cells do not require antigen exposure to get activated; their functional response is rather based on a balance between inhibitory/activating signals and on the diversity of germline-encoded receptors they express. In order to reach optimal functional status, NK cells go through a step-wise development in the bone marrow before their egress, and dissemination into peripheral organs via the circulation. In this review, we summarize bone marrow NK cell developmental stages and list key factors involved in their differentiation before presenting newly discovered and emerging factors that regulate NK cell central and peripheral maturation. Lastly, we focus on the impact inflammatory contexts themselves can have on NK cell development and functional maturation.

Protein phosphatases regulate the liver microenvironment in the development of hepatocellular carcinoma

The liver is a complicated heterogeneous organ composed of different cells. Parenchymal cells called hepatocytes and various nonparenchymal cells, including immune cells and stromal cells, are distributed in liver lobules with hepatic architecture. They interact with each other to compose the liver microenvironment and determine its characteristics. Although the liver microenvironment maintains liver homeostasis and function under healthy conditions, it also shows proinflammatory and profibrogenic characteristics that can induce the progression of hepatitis and hepatic fibrosis, eventually changing to a protumoral microenvironment that contributes to the development of hepatocellular carcinoma (HCC). According to recent studies, phosphatases are involved in liver diseases and HCC development by regulating protein phosphorylation in intracellular signaling pathways and changing the activities and characteristics of liver cells. Therefore, this review aims to highlight the importance of protein phosphatases in HCC development and in the regulation of the cellular components in the liver microenvironment and to show their significance as therapeutic targets.

Tumor microenvironment: barrier or opportunity towards effective cancer therapy

Tumor microenvironment (TME) is a specialized ecosystem of host components, designed by tumor cells for successful development and metastasis of tumor. With the advent of 3D culture and advanced bioinformatic methodologies, it is now possible to study TME’s individual components and their interplay at higher resolution. Deeper understanding of the immune cell’s diversity, stromal constituents, repertoire profiling, neoantigen prediction of TMEs has provided the opportunity to explore the spatial and temporal regulation of immune therapeutic interventions. The variation of TME composition among patients plays an important role in determining responders and non-responders towards cancer immunotherapy. Therefore, there could be a possibility of reprogramming of TME components to overcome the widely prevailing issue of immunotherapeutic resistance. The focus of the present review is to understand the complexity of TME and comprehending future perspective of its components as potential therapeutic targets. The later part of the review describes the sophisticated 3D models emerging as valuable means to study TME components and an extensive account of advanced bioinformatic tools to profile TME components and predict neoantigens. Overall, this review provides a comprehensive account of the current knowledge available to target TME.

Aurantii Fructus Immaturus enhances natural killer cytolytic activity and anticancer efficacy in vitro and in vivo

Aurantii Fructus Immaturus (AFI), extensively used in traditional herbal medicine, is known to have diverse physiological effects against various diseases, including obesity, diabetes, and cardiovascular disease. However, the effects of AFI on the immune system, especially natural killer (NK) cells, remain largely unknown. We aimed to investigate the effect of AFI on NK cell activity in vitro and in vivo and to elucidate the underlying mechanisms. Further, we verified the anticancer efficacy of AFI in a mouse lung metastasis model, underscoring the therapeutic potential of AFI in cancer therapy. Our results revealed that AFI significantly enhanced the cytolytic activity of NK cells in a dose-dependent manner, accompanied by an increase in the expression of NK cell-activating receptors, especially NKp30 and NKp46. AFI treatment also increased the expression of cytolytic granules, including granzyme B and perforin. Furthermore, the expression of CD107a, a degranulation marker, was increased upon treatment with AFI. A signaling study using western blot analysis demonstrated that the phosphorylation of extracellular signal-regulated kinase (ERK) was involved in increasing the NK cell activity following AFI treatment. In the in vivo study performed in mice, oral administration of AFI markedly enhanced the cytotoxic activity of spleen mononuclear cells against YAC-1 cells, which was accompanied by NKp46 upregulation. In addition, we confirmed that cancer metastasis was inhibited in a mouse cancer metastasis model, established using the mouse melanoma B16F10 cell line, by the administration of AFI in vivo. Collectively, these results indicate that AFI enhances NK cell-mediated cytotoxicity in vitro and in vivo via activation of the ERK signaling pathway and suggest that AFI could be a potential supplement for cancer immunotherapy.

Biodegradable nanoparticles induce cGAS/STING-dependent reprogramming of myeloid cells to promote tumor immunotherapy

Cancer treatment utilizing infusion therapies to enhance the patient's own immune response against the tumor have shown significant functionality in a small subpopulation of patients. Additionally, advances have been made in the utilization of nanotechnology for the treatment of disease. We have previously reported the potent effects of 3-4 daily intravenous infusions of immune modifying poly(lactic-co-glycolic acid) (PLGA) nanoparticles (IMPs; named ONP-302) for the amelioration of acute inflammatory diseases by targeting myeloid cells. The present studies describe a novel use for ONP-302, employing an altered dosing scheme to reprogram myeloid cells resulting in significant enhancement of tumor immunity. ONP-302 infusion decreased tumor growth via the activation of the cGAS/STING pathway within myeloid cells, and subsequently increased NK cell activation via an IL-15-dependent mechanism. Additionally, ONP-302 treatment increased PD-1/PD-L1 expression in the tumor microenvironment, thereby allowing for functionality of anti-PD-1 for treatment in the B16.F10 melanoma tumor model which is normally unresponsive to monotherapy with anti-PD-1. These findings indicate that ONP-302 allows for tumor control via reprogramming myeloid cells via activation of the STING/IL-15/NK cell mechanism, as well as increasing anti-PD-1 response rates.

Crosstalk between angiogenesis and immune regulation in the tumor microenvironment

Cancer creates a complex tumor microenvironment (TME) composed of immune cells, stromal cells, blood vessels, and various other cellular and extracellular elements. It is essential for the development of anti-cancer combination therapies to understand and overcome this high heterogeneity and complexity as well as the dynamic interactions between them within the TME. Recent treatment strategies incorporating immune-checkpoint inhibitors and anti-angiogenic agents have brought many changes and advances in clinical cancer treatment. However, there are still challenges for immune suppressive tumors, which are characterized by a lack of T cell infiltration and treatment resistance. In this review, we will investigate the crosstalk between immunity and angiogenesis in the TME. In addition, we will look at strategies designed to enhance anti-cancer immunity, to convert “immune suppressive tumors” into “immune activating tumors,” and the mechanisms by which these strategies enhance effector immune cell infiltration.

Off-the-Shelf Chimeric Antigen Receptor Immune Cells from Human Pluripotent Stem Cells

Autologous chimeric antigen receptor (CAR) T cells have expanded the scope and therapeutic potential of anti-cancer therapy. Nevertheless, autologous CAR-T therapy has been challenging due to labor some manufacturing processes for every patient, and the cost due to the complexity of the process. Moreover, T cell dysfunction results from the immunosuppressive tumor microenvironment in certain patients. Considering technical challenges in autologous donors, the development of safe and efficient allogeneic CAR-T therapy will address these issues. Since the advent of the generation of immune cells from pluripotent stem cells (PSCs), numerous studies focus on the off-the-shelf generation of CAR-immune cells derived from the universal donor PSCs, which simplifies the manufacturing process and standardizes CAR-T products. In this review, we will discuss advances in the generation of immune cells from PSCs, together with the potential and perspectives of CAR-T, CAR-macrophages, and CAR-natural killer (NK) cells in cancer treatment. The combination of PSC-derived immune cells and CAR engineering will pave the way for developing next-generation cancer immunotherapy.

Inhibition of O-GlcNAcylation Decreases the Cytotoxic Function of Natural Killer Cells

Natural killer (NK) cells mediate killing of malignant and virus-infected cells, a property that is explored as a cell therapy approach in the clinic. Various cell intrinsic and extrinsic factors affect NK cell cytotoxic function, and an improved understanding of the mechanism regulating NK cell function is necessary to accomplish better success with NK cell therapeutics. Here, we explored the role of O-GlcNAcylation, a previously unexplored molecular mechanism regulating NK cell function. O-GlcNAcylation is a post-translational modification mediated by O-GlcNAc transferase (OGT) that adds the monosaccharide N-acetylglucosamine to serine and threonine residues on intracellular proteins and O-GlcNAcase (OGA) that removes the sugar. We found that stimulation of NK cells with the cytokines interleukin-2 (IL-2) and IL-15 results in enhanced O-GlcNAcylation of several cellular proteins. Chemical inhibition of O-GlcNAcylation using OSMI-1 was associated with a decreased expression of NK cell receptors (NKG2D, NKG2A, NKp44), cytokines [tumor necrosis factor (TNF)-α, interferon (IFN-γ)], granulysin, soluble Fas ligand, perforin, and granzyme B in NK cells. Importantly, inhibition of O-GlcNAcylation inhibited NK cell cytotoxicity against cancer cells. However, increases in O-GlcNAcylation following OGA inhibition using an OGA inhibitor or shRNA-mediated suppression did not alter NK cell cytotoxicity. Finally, we found that NK cells pretreated with OSMI-1 to inhibit O-GlcNAcylation showed compromised cytotoxic activity against tumor cells in vivo in a lymphoma xenograft mouse model. Overall, this study provides the seminal insight into the role of O-GlcNAcylation in regulating NK cell cytotoxic function.

Differential effects on natural killer cell production by membrane-bound cytokine stimulations

Robust manufacturing production of natural killer (NK) cells has been challenging in allogeneic NK cell-based therapy. Here, we compared the impact of cytokines on NK cell expansion by developing recombinant K562 feeder cell lines expressing membrane-bound cytokines, mIL15, mIL21, and 41BBL, individually or in combination. We found that 41BBL played a dominant role in promoting up to 500,000-fold of NK cell expansion after a 21-day culture process without inducing exhaustion. However, 41BBL stimulation reduced the overall cytotoxic activity of NK cells when combined with mIL15 and mIL21. Additionally, long-term stimulation with mIL15 and mIL21, but not 41BBL, increased CD56 expression and CD56bright population, which is unexpectedly correlated with the NK cell cytotoxicity. By conducting single-cell sequencing, we identified distinct subpopulations of NK cells induced by different cytokines, including an adaptive-like CD56brightCD16-CD49a+ subset induced by mIL15. Through gene expression analysis, we found that cytokines modulated signaling pathways and target genes involved in cell cycle, senescence, self-renewal, migration, and maturation, in a different manner. Together, our study demonstrated cytokine signal pathways play different roles in NK cell expansion and differentiation, which shed light on NK cell process design to improve productivity and product quality. This article is protected by copyright. All rights reserved.

Browning Epicardial Adipose Tissue: Friend or Foe?

The epicardial adipose tissue (EAT) is the visceral fat depot of the heart which is highly plastic and in direct contact with myocardium and coronary arteries. Because of its singular proximity with the myocardium, the adipokines and pro-inflammatory molecules secreted by this tissue may directly affect the metabolism of the heart and coronary arteries. Its accumulation, measured by recent new non-invasive imaging modalities, has been prospectively associated with the onset and progression of coronary artery disease (CAD) and atrial fibrillation in humans. Recent studies have shown that EAT exhibits beige fat-like features, and express uncoupling protein 1 (UCP-1) at both mRNA and protein levels. However, this thermogenic potential could be lost with age, obesity and CAD. Here we provide an overview of the physiological and pathophysiological relevance of EAT and further discuss whether its thermogenic properties may serve as a target for obesity therapeutic management with a specific focus on the role of immune cells in this beiging phenomenon.

Mass Cytometry Exploration of Immunomodulatory Responses of Human Immune Cells Exposed to Silver Nanoparticles

Increasing production and application of silver nanoparticles (Ag NPs) have raised concerns on their possible adverse effects on human health. However, a comprehensive understanding of their effects on biological systems, especially immunomodulatory responses involving various immune cell types and biomolecules (e.g., cytokines and chemokines), is still incomplete. In this study, a single-cell-based, high-dimensional mass cytometry approach is used to investigate the immunomodulatory responses of Ag NPs using human peripheral blood mononuclear cells (hPBMCs) exposed to poly-vinyl-pyrrolidone (PVP)-coated Ag NPs of different core sizes (i.e., 10-, 20-, and 40-nm). Although there were no severe cytotoxic effects observed, ^PVPAg¹⁰ and ^PVPAg²⁰ were excessively found in monocytes and dendritic cells, while ^PVPAg⁴⁰ displayed more affinity with B cells and natural killer cells, thereby triggering the release of proinflammatory cytokines such as IL-2, IL-17A, IL-17F, MIP1β, TNFα, and IFNγ. Our findings indicate that under the exposure conditions tested in this study, Ag NPs only triggered the inflammatory responses in a size-dependent manner rather than induce cytotoxicity in hPBMCs. Our study provides an appropriate ex vivo model to better understand the human immune responses against Ag NP at a single-cell level, which can contribute to the development of targeted drug delivery, vaccine developments, and cancer radiotherapy treatments.

Natural killer cell-targeted immunotherapy for cancer

Natural killer (NK) cells were initially described in the early 1970s as major histocompatibility complex unrestricted killers due to their ability to spontaneously kill certain tumor cells. In the past decade, the field of NK cell-based treatment has been accelerating exponentially, holding a dominant position in cancer immunotherapy innovation. Generally, research on NK cell-mediated antitumor therapies can be categorized into three areas: choosing the optimal source of allogenic NK cells to yield massively amplified "off-the-shelf" products, improving NK cell cytotoxicity and longevity, and engineering NK cells with the ability of tumor-specific recognition. In this review, we focused on NK cell manufacturing techniques, some auxiliary methods to enhance the therapeutic efficacy of NK cells, chimeric antigen receptor NK cells, and monoclonal antibodies targeting inhibitory receptors, which can significantly augment the antitumor activity of NK cells. Notably, emerging evidence suggests that NK cells are a promising constituent of multipronged therapeutic strategies, strengthening immune responses to cancer.

Kinetic, imaging based assay to measure NK cell cytotoxicity against adherent cells

Natural Killer cells (NK cells) are a key component of the innate immune system and are key effectors of immunosurveillance. NK cells not only have the inherent ability to directly kill malignant, compromised, or virally infected cells, but also recruit and coordinate responses by other immune cells to prime the adaptive immune response. Given this potent anti-tumor response and good safety profile, adoptive NK cell therapy is an emerging cancer treatment modality. Direct killing of tumor cells is major mode of action for NK cell anti-tumor activity and measuring changes in NK cell cytotoxic response in vitro is a critical step in pre-clinical evaluation of novel NK cellular products. Here, we provide a detailed protocol for a live-cell imaging assay for testing NK cell cytotoxicity against a broad range of adherent and 3D in vitro tumor models. Compared to other methods for measuring in vitro cytotoxicity, this method offers real-time dynamic tracking of and provides a multiparameter readout for more robust understanding of NK cell tumor killing.

Targeting ADCC: A different approach to HER2 breast cancer in the immunotherapy era

The clinical outcome of patients with human epidermal growth factor receptor 2 (HER2) amplified breast carcinoma (BC) has improved with the development of anti-HER2 targeted therapies. However, patients can experience disease recurrence after curative intent and disease progression in the metastatic setting. In the current era of evolving immunotherapy agents, the understanding of the immune response against HER2 tumor cells developed by anti-HER2 antibodies (Abs) is rapidly evolving. Trastuzumab therapy promotes Natural Killer (NK) cell activation in patients with BC overexpressing HER2, indicating that the efficacy of short-term trastuzumab monotherapy, albeit direct inhibition of HER, could also be related with antibody-dependent cell-mediated cytotoxicity (ADCC). Currently, dual HER2 blockade using trastuzumab and pertuzumab is the standard of care in early and advanced disease as this combination could confer an additive effect in ADCC. In patients with disease relapse or progression, ADCC may be hampered by several factors such as FcγRIIIa polymorphism and an immunosuppressive environment, among others. Hence, new drug development strategies are being investigated aiming to boost the ADCC response triggered by anti-HER2 therapy. In this review, we summarize these strategies and the rationale, through mAbs engineering and combinatorial strategies, focusing on clinical results and ongoing trials.

Heparanase is a regulator of natural killer cell activation and cytotoxicity

Heparanase is the only mammalian enzyme capable of cleaving heparan sulfate, a glycosaminoglycan of the extracellular matrix and cell surfaces. Most immune cells express heparanase that contributes to a range of functions including cell migration and cytokine expression. Heparanase also promotes natural killer (NK) cell migration; however, its role in other NK cell functions remains to be defined. In this study, heparanase-deficient (Hpse^-/- ) mice were used to assess the role of heparanase in NK cell cytotoxicity, activation, and cytokine production. Upon challenge with the immunostimulant polyinosinic:polycytidylic acid (poly(I:C)), NK cells isolated from Hpse^-/- mice displayed impaired cytotoxicity against EO771.LMB cells and reduced levels of activation markers CD69 and NKG2D. However, in vitro cytokine stimulation of wild-type and Hpse^-/- NK cells resulted in similar CD69 and NKG2D expression, suggesting the impaired NK cell activation in Hpse^-/- mice results from elements within the in vivo niche. NK cells are activated in vivo by dendritic cells (DCs) in response to poly(I:C). Poly(I:C)-stimulated Hpse^-/- bone marrow DCs (BMDCs) expressed less IL-12, and when cultured with Hpse^-/- NK cells, less MCP-1 mRNA and protein was detected. Although cell-cell contact is important for DC-mediated NK cell activation, co-cultures of Hpse^-/- BMDCs and NK cells showed similar levels of contact to wild-type cells, suggesting heparanase contributes to NK cell activation independently of cell-cell contact with DCs. These observations define a role for heparanase in NK cell cytotoxicity and activation and have important implications for how heparanase inhibitors currently in clinical trials for metastatic cancer may impact NK cell immunosurveillance.

Myeloid-Derived Suppressor Cells Restrain Natural Killer Cell Activity in Acute Coxsackievirus B3-Induced Myocarditis

Murine models of coxsackievirus B3 (CVB3)-induced myocarditis well represent the different outcomes of this inflammatory heart disease. Previously, we found that CVB3-infected A.BY/SnJ mice, susceptible for severe acute and chronic myocarditis, have lower natural killer (NK) cell levels than C57BL/6 mice, with mild acute myocarditis. There is evidence that myeloid-derived suppressor cells (MDSC) may inhibit NK cells, influencing the course of myocarditis. To investigate the MDSC/NK interrelationship in acute myocarditis, we used CVB3-infected A.BY/SnJ mice. Compared to non-infected mice, we found increased cell numbers of MDSC in the spleen and heart of CVB3-infected A.BY/SnJ mice. In parallel, S100A8 and S100A9 were increased in the heart, spleen, and especially in splenic MDSC cells compared to non-infected mice. In vitro experiments provided evidence that MDSC disrupt cytotoxic NK cell function upon co-culturing with MDSC. MDSC-specific depletion by an anti-Ly6G antibody led to a significant reduction in the virus load and injury in hearts of infected animals. The decreased cardiac damage in MDSC-depleted mice was associated with fewer Mac3⁺ macrophages and CD3⁺ T lymphocytes and a reduced cardiac expression of S100A8, S100A9, IL-1β, IL-6, and TNF-α. In conclusion, impairment of functional NK cells by MDSC promotes the development of chronic CVB3 myocarditis in A.BY/SnJ mice.

Natural Killer Cells: The Linchpin for Successful Cancer Immunotherapy

Cancer immunotherapy is a highly successful and rapidly evolving treatment modality that works by augmenting the body’s own immune system. While various immune stimulation strategies such as PD-1/PD-L1 or CTLA-4 checkpoint blockade result in robust responses, even in patients with advanced cancers, the overall response rate is low. While immune checkpoint inhibitors are known to enhance cytotoxic T cells’ antitumor response, current evidence suggests that immune responses independent of cytotoxic T cells, such as Natural Killer (NK) cells, play crucial role in the efficacy of immunotherapeutic interventions. NK cells hold a distinct role in potentiating the innate immune response and activating the adaptive immune system. This review highlights the importance of the early actions of the NK cell response and the pivotal role NK cells hold in priming the immune system and setting the stage for successful response to cancer immunotherapy. Yet, in many patients the NK cell compartment is compromised thus lowering the chances of successful outcomes of many immunotherapies. An overview of mechanisms that can drive NK cell dysfunction and hinder immunotherapy success is provided. Rather than relying on the likely dysfunctional endogenous NK cells to work with immunotherapies, adoptive allogeneic NK cell therapies provide a viable solution to increase response to immunotherapies. This review highlights the advances made in development of NK cell therapeutics for clinical application with evidence supporting their combinatorial application with other immune-oncology approaches to improve outcomes of immunotherapies.

Targeting NK Cells to Enhance Melanoma Response to Immunotherapies

Natural killer (NK) cells are a key component of an innate immune system. They are important not only in initiating, but also in augmenting adaptive immune responses. NK cell activation is mediated by a carefully orchestrated balance between the signals from inhibitory and activating NK cell receptors. NK cells are potent producers of proinflammatory cytokines and are also able to elicit strong antitumor responses through secretion of perforin and granzyme B. Tumors can develop many mechanisms to evade NK cell antitumor responses, such as upregulating ligands for inhibitory receptors, secreting anti-inflammatory cytokines and recruiting immunosuppressive cells. Enhancing NK cell responses will likely augment the effectiveness of immunotherapies, and strategies to accomplish this are currently being evaluated in clinical trials. A comprehensive understanding of NK cell biology will likely provide additional opportunities to further leverage the antitumor effects of NK cells. In this review, we therefore sought to highlight NK cell biology, tumor evasion of NK cells and clinical trials that target NK cells.

Immunomodulatory Role of NK Cells during Antiviral Antibody Therapy

Monoclonal antibodies (mAbs) are now considered as a therapeutic approach to prevent and treat severe viral infections. Using a mouse retroviral model, we showed that mAbs induce protective immunity (vaccinal effects). Here, we investigated the role of natural killer (NK) cells on this effect. NK cells are effector cells that are crucial to control viral propagation upon mAb treatment. However, their immunomodulatory activity during antiviral mAb immunotherapies has been little studied. Our data reveal that the mAb treatment of infected mice preserves the functional activation of NK cells. Importantly, functional NK cells play an essential role in preventing immune dysfunction and inducing antiviral protective immunity upon mAb therapy. Thus, NK cell depletion in mAb-treated, viral-infected mice leads to the upregulation of molecules involved in immunosuppressive pathways (i.e., PD-1, PD-L1 and CD39) on dendritic cells and T cells. NK cell depletion also abrogates the vaccinal effects induced by mAb therapy. Our data also reveal a role for IFNγ-producing NK cells in the enhancement of the B-cell responses through the potentiation of the B-cell helper properties of neutrophils. These findings suggest that preserved NK cell functions and counts might be required for achieving mAb-induced protective immunity. They open new prospects for improving antiviral immunotherapies.

NK cell-based cancer immunotherapy: from basic biology to clinical development

Natural killer (NK) cell is a specialized immune effector cell type that plays a critical role in immune activation against abnormal cells. Different from events required for T cell activation, NK cell activation is governed by the interaction of NK receptors with target cells, independent of antigen processing and presentation. Due to relatively unsophisticated cues for activation, NK cell has gained significant attention in the field of cancer immunotherapy. Many efforts are emerging for developing and engineering NK cell-based cancer immunotherapy. In this review, we provide our current understandings of NK cell biology, ongoing pre-clinical and clinical development of NK cell-based therapies and discuss the progress, challenges, and future perspectives.

The role of NK cells in fighting the virus infection and sepsis

Natural killer cells, one of the important types of innate immune cells, play a pivotal role in the antiviral process in vivo. It has been shown that increasing NK cell activity may promote the alleviation of viral infections, even severe infection-induced sepsis. Given the current state of the novel coronavirus (SARS-CoV-2) global pandemic, clarifying the anti-viral function of NK cells would be helpful for revealing the mechanism of host immune responses and decipher the progression of COVID-19 and providing important clues for combating this pandemic. In this review, we summarize the roles of NK cells in viral infection and sepsis as well as the potential possibilities of NK cell-based immunotherapy for treating COVID-19.

Design and Implementation of NK Cell-Based Immunotherapy to Overcome the Solid Tumor Microenvironment

Natural killer (NK) cells are innate immune effectors capable of broad cytotoxicity via germline-encoded receptors and can have conferred cytotoxic potential via the addition of chimeric antigen receptors. Combined with their reduced risk of graft-versus-host disease (GvHD) and cytokine release syndrome (CRS), NK cells are an attractive therapeutic platform. While significant progress has been made in treating hematological malignancies, challenges remain in using NK cell-based therapy to combat solid tumors due to their immunosuppressive tumor microenvironments (TMEs). The development of novel strategies enabling NK cells to resist the deleterious effects of the TME is critical to their therapeutic success against solid tumors. In this review, we discuss strategies that apply various genetic and non-genetic engineering approaches to enhance receptor-mediated NK cell cytotoxicity, improve NK cell resistance to TME effects, and enhance persistence in the TME. The successful design and application of these strategies will ultimately lead to more efficacious NK cell therapies to treat patients with solid tumors. This review outlines the mechanisms by which TME components suppress the anti-tumor activity of endogenous and adoptively transferred NK cells while also describing various approaches whose implementation in NK cells may lead to a more robust therapeutic platform against solid tumors.

Immunological and Virological Responses in Older HIV-Infected Adults Receiving Antiretroviral Therapy: An Evidence-Based Meta-Analysis

BACKGROUND

Millions of people living with the HIV have received antiretroviral therapy (ART). Older adults make up a significant portion of these individuals; however, the immunological and virological responses to ART for older patients still need to be clarified.

DESIGN

Meta-analysis.

METHODS

In this article, we systematically reviewed research articles published between 2001 and 2018 that reported immunological and virological responses and AIDS-related mortality among HIV- infected adults (including individuals aged 50 years and older) receiving ART, using meta-analysis. ART efficiency was measured using 3 outcomes: (1) immunological response, (2) virological response, and (3) mortality.

RESULTS

We identified 4937 citations, and 40 studies were eventually selected to investigate ART efficiency in older HIV-infected patients, comprising more than 888,151 patients initiating ART. We report that older patients showed poor immunological responses, with CD4 counts and the restoration of CD4 counts after ART initiation being significantly lower than seen in younger patients. However, older patients exhibited better viral suppression rates (risk ratio: 1.04; 95% confidence intervals: 1.01 to 1.08) after 36 months following ART initiation. In addition, older adults had a higher risk of AIDS-related death (adjusted hazard ratio: 1.44, 95% confidence interval: 1.30 to 1.60).

CONCLUSIONS

Older age after ART initiation was associated with a poorer immunological response and a higher risk of mortality, suggesting the need to increase early diagnosis and treatment among older HIV patients.

Improving Tumor Retention of Effector Cells in Adoptive Cell Transfer Therapies by Magnetic Targeting

Adoptive cell transfer therapy is a promising anti-tumor immunotherapy in which effector immune cells are transferred to patients to treat tumors. However, one of its main limitations is the inefficient trafficking of inoculated effector cells to the tumor site and the small percentage of effector cells that remain activated when reaching the tumor. Multiple strategies have been attempted to improve the entry of effector cells into the tumor environment, often based on tumor types. It would be, however, interesting to develop a more general approach, to improve and facilitate the migration of specific activated effector lymphoid cells to any tumor type. We and others have recently demonstrated the potential for adoptive cell transfer therapy of the combined use of magnetic nanoparticle-loaded lymphoid effector cells together with the application of an external magnetic field to promote the accumulation and retention of lymphoid cells in specific body locations. The aim of this review is to summarize and highlight the recent findings in the field of magnetic accumulation and retention of effector cells in tumors after adoptive transfer, and to discuss the possibility of using this approach for tumor targeting with chimeric antigen receptor (CAR) T-cells.

Oncolytic Measles Virus Encoding Interleukin-12 Mediated Antitumor Activity and Immunologic Control of Colon Cancer In Vivo and Ex Vivo

Background: In this study, we used an oncolytic measles virus encoding interleukin 12 (IL-12) to treat colon cancer in vivo and ex vivo to investigate its effect on the viability and apoptosis of colon cancer cells. Method: A rat model was established to evaluate the immunostimulatory capabilities and therapeutic efficacy of vectors encoding an IL-12 fusion protein (MeVac FmIL-12 vectors). TUNEL staining, western blot, and enzyme-linked immunosorbent assay were performed to examine the impacts of MeVac FmIL-12 on the expression of inflammatory cytokines. Cell transfection was carried out to validate the anti-tumor role of MeVac FmIL-12 in vitro. Flow cytometry and MTT assay were performed to assess the effects of MeVac FmIL-12 on cell apoptosis and viability. Result: High concentrations (10-1000 ng/mL) of murine IL-12 fusion protein (FmIL-12) decreased the production of interferon γ (IFN-γ) in a concentration-dependent manner and reflected FmIL-12-induced overstimulation. Rats treated with MeVac vectors encoding FmIL-12 showed a significantly increased level of FmIL-12 overtime and a concentration-dependent (0.01-10 ng/mL) increase in IFN-γ production. MeVac FmIL-12 also increased the expression of inflammatory cytokines (IFN-γ, tumor necrosis factor α, and IL-6) both in vivo and in vitro. MeVac FmIL-12 promoted cell apoptosis and reduced cell viability, which helped to trigger a systemic anti-tumor immune response, both in vivo and in vitro. Conclusion: In this study, we suggested that MeVac FmIL-12 enhanced the therapeutic efficacy of tumor treatment by improving anti-tumor immunity.

Considerations of Antibody Geometric Constraints on NK Cell Antibody Dependent Cellular Cytotoxicity

It has been well-established that antibody isotype, glycosylation, and epitope all play roles in the process of antibody dependent cellular cytotoxicity (ADCC). For natural killer (NK) cells, these phenotypes are linked to cellular activation through interaction with the IgG receptor FcγRIIIa, a single pass transmembrane receptor that participates in cytoplasmic signaling complexes. Therefore, it has been hypothesized that there may be underlying spatial and geometric principles that guide proper assembly of an activation complex within the NK cell immune synapse. Further, synergy of antibody phenotypic properties as well as allosteric changes upon antigen binding may also play an as-of-yet unknown role in ADCC. Understanding these facets, however, remains hampered by difficulties associated with studying immune synapse dynamics using classical approaches. In this review, I will discuss relevant NK cell biology related to ADCC, including the structural biology of Fc gamma receptors, and how the dynamics of the NK cell immune synapse are being studied using innovative microscopy techniques. I will provide examples from the literature demonstrating the effects of spatial and geometric constraints on the T cell receptor complex and how this relates to intracellular signaling and the molecular nature of lymphocyte activation complexes, including those of NK cells. Finally, I will examine how the integration of high-throughput and "omics" technologies will influence basic NK cell biology research moving forward. Overall, the goal of this review is to lay a basis for understanding the development of drugs and therapeutic antibodies aimed at augmenting appropriate NK cell ADCC activity in patients being treated for a wide range of illnesses.

Engineered Three-Dimensional Tumor Models to Study Natural Killer Cell Suppression

A critical hurdle associated with natural killer (NK) cell immunotherapies is inadequate infiltration and function in the solid tumor microenvironment. Well-controlled 3D culture systems could advance our understanding of the role of various biophysical and biochemical cues that impact NK cell migration in solid tumors. The objectives of this study were to establish a biomaterial which (i) supports NK cell migration and (ii) recapitulates features of the in vivo solid tumor microenvironment, to study NK infiltration and function in a 3D system. Using peptide-functionalized poly(ethylene glycol)-based hydrogels, the extent of NK-92 cell migration was observed to be largely dependent on the density of integrin binding sites and the presence of matrix metalloproteinase degradable sites. When lung cancer cells were encapsulated into the hydrogels to create tumor microenvironments, the extent of NK-92 cell migration and functional activity was dependent on the cancer cell type and duration of 3D culture. NK-92 cells showed greater migration into the models consisting of nonmetastatic A549 cells relative to metastatic H1299 cells, and reduced migration in both models when cancer cells were cultured for 7 days versus 1 day. In addition, the production of NK cell-related pro-inflammatory cytokines and chemokines was reduced in H1299 models relative to A549 models. These differences in NK-92 cell migration and cytokine/chemokine production corresponded to differences in the production of various immunomodulatory molecules by the different cancer cells, namely, the H1299 models showed increased stress ligand shedding and immunosuppressive cytokine production, particularly TGF-β. Indeed, inhibition of TGF-β receptor I in NK-92 cells restored their infiltration in H1299 models to levels similar to that in A549 models and increased overall infiltration in both models. Relative to conventional 2D cocultures, NK-92 cell mediated cytotoxicity was reduced in the 3D tumor models, suggesting the hydrogel serves to mimic some features of the biophysical barriers in in vivo tumor microenvironments. This study demonstrates the feasibility of a synthetic hydrogel system for investigating the biophysical and biochemical cues impacting NK cell infiltration and NK cell-cancer cell interactions in the solid tumor microenvironment.

Comparison of Sheep, Goats, and Calves as Infection Models for Mycobacterium avium subsp. paratuberculosis

Animal infection models to study Mycobacterium avium subsp. paratuberculosis (MAP) infection are useful for evaluating the efficacy of vaccines and other therapeutics for the prevention or treatment of infection. The goal of the present study was to compare smaller ruminants, sheep and goats, with calves as infection models. Neonatal sheep, goats, and calves (n = 4) received 10⁹ cfu of a cattle isolate of MAP in milk replacer on days 0, 3 and 6 in a 12-month study and sampled monthly thereafter. Results demonstrated a robust antigen-specific IFN-γ response at 90 days post-inoculation for sheep and goats, with lower responses noted for calves. By 360 days, IFN-γ responses were 50 and 82% higher for calves than for goats and sheep, respectively. Although MAP-specific antibody responses were first observed in sheep at 90 days, calves had higher antibody responses throughout the remainder of the study. Following pass-through shedding on day 7, fecal shedding was fairly negligible across treatments but remained higher for calves throughout the study. Colonization of tissues was variable within treatment group and was higher for calves and sheep for the majority of tissues. Upon antigen stimulation of PBMCs, higher populations of CD4 + T cells cells and lower populations of γδ TCR + and NK cells were observed for goats and calves compared to sheep. Relative gene expression of IL-4, IL-12, and IL-17 in PBMCs was higher in goats, corresponding to lower tissue colonization with MAP. These data suggest that ruminant species are fairly comparable as infection models for MAP, but discrete differences in host responses to MAP infection exist between species.