The Natural Cytotoxicity Receptors in Health and Disease

Multiple O- and an N-glycosylation of the stalk region of the NK cell activation receptor NKp46 mediates its interaction with the Candida glabrata epithelial adhesin 1

Natural killer (NK) cells are critical components of the innate immune system. Their primary role is to induce apoptosis in target cells, such as cancerous or virally infected cells. These targets are recognized through interactions between activating or inhibitory receptors on the NK cell surface. Among the activating receptors is the natural cytotoxicity receptor NKp46. Several ligands for this receptor have been identified, including the epithelial adhesin Epa1 from the yeast Candida glabrata. Invasive candidiasis caused by this yeast is a significant complication for patients with hematological diseases. The interaction between NKp46 and Epa1 is thought to depend specifically on an O-glycan at threonine 225 of NKp46. To elucidate the molecular details of this interaction, we optimized the recombinant production of soluble NKp46 and Epa1, generated glycosylation variants of multiple NKp46 mutants, and evaluated the role of NKp46 glycosylation in Epa1 binding using microscale thermophoresis and isothermal titration calorimetry. Additionally, for the first time, we provide a comprehensive glycosylation profile of NKp46, determined through mass spectrometry of intact glycopeptides obtained by O-glycoprotease and trypsin proteolysis. Our findings demonstrate that the NKp46 stalk is glycosylated at multiple sites, involving both an N-glycan and more than one O-glycan. These glycans are critical for the interaction with Epa1, providing NK cells with enhanced sensitivity to Candida glabrata epitopes.

Senescence, NK cells, and cancer: navigating the crossroads of aging and disease

Cellular senescence, a state of stable cell cycle arrest, acts as a double-edged sword in cancer biology. In young organisms, it acts as a barrier against tumorigenesis, but in the aging population, it may facilitate tumor growth and metastasis through the senescence-associated secretory phenotype (SASP). Natural killer (NK) cells play a critical role in the immune system, particularly in the surveillance, targeting, and elimination of malignant and senescent cells. However, age-related immunosenescence is characterized by declining NK cell function resulting in diminished ability to fight infection, eliminate senescent cells and suppress tumor development. This implies that preserving or augmenting NK cell function may be central to defense against age-related degenerative and malignant diseases. This review explores the underlying mechanisms behind these interactions, focusing on how aging influences the battle between the immune system and cancer, the implications of senescent NK cells in disease progression, and the potential of adoptive NK cell therapy as a countermeasure to these age-related immunological challenges.

Understanding the interplay between oHSV and the host immune system: Implications for therapeutic oncolytic virus development

Oncolytic herpes simplex viruses (oHSV) preferentially replicate in cancer cells while inducing antitumor immunity, and thus, they are often referred to as in situ cancer vaccines. OHSV infection of tumors elicits diverse host immune responses comprising both innate and adaptive components. Although the innate and adaptive immune responses primarily target the tumor, they also contribute to antiviral immunity, limiting viral replication/oncolysis. OHSV-encoded proteins use various mechanisms to evade host antiviral pathways and immune recognition, favoring oHSV replication, oncolysis, and spread. In general, oHSV infection and replication within tumors results in a series of sequential events, such as oncolysis and release of tumor and viral antigens, dendritic cell-mediated antigen presentation, T cell priming and activation, T cell trafficking and infiltration to tumors, and T cell recognition of cancer cells, leading to tumor (and viral) clearance. These sequential events align with all steps of the cancer-immunity cycle. However, a comprehensive understanding of the interplay between oHSV and host immune responses is crucial to optimize oHSV-induced antitumor immunity and efficacy. Therefore, this review aims to elucidate oHSV's communication with innate and adaptive immune systems and use such interactions to improve oHSV's potential as a potent immunovirotherapeutic agent against cancer.

γδT cells, a key subset of T cell for cancer immunotherapy

γδT cells represent a unique and versatile subset of T cells characterized by the expression of T-cell receptors (TCRs) composed of γ and δ chains. Unlike conventional αβT cells, γδT cells do not require major histocompatibility complex (MHC)-dependent antigen presentation for activation, enabling them to recognize and respond to a wide array of antigens, including phosphoantigens, stress-induced ligands, and tumor-associated antigens. While γδT cells are relatively rare in peripheral blood, they are enriched in peripheral tissues such as the skin, intestine, and lung. These cells play a crucial role in tumor immunotherapy by exerting direct cytotoxicity through the production of inflammatory cytokines (e.g., interferon-gamma (IFN-γ), tumor necrosis factor-alpha (TNF-α), and interleukin-17 (IL-17)) and cytotoxic molecules (e.g., perforin and granzyme). Recent advances in γδT cell research have elucidated their mechanisms of tumor recognition, including the detection of phosphoantigens and stress-induced ligands like MICA (MHC class I polypeptide-related sequence A), MICB (MHC class I polypeptide-related sequence B), and ULBP (UL16-binding protein). Furthermore, various strategies to enhance γδT cell-based tumor immunotherapy have been developed, such as in vitro expansion using phosphoantigen-based therapies, cytokine stimulation, and chimeric antigen receptor (CAR)-γδT cell engineering. These advancements have shown promising results in both preclinical and clinical settings, paving the way for γδT cells to become a powerful tool in cancer immunotherapy. This review highlights the key mechanisms, functions, and strategies to harness the potential of γδT cells for effective tumor immunotherapy.

Gamma delta T cells and their immunotherapeutic potential in cancer

Gamma-delta (γδ) T cells are a unique subset of T lymphocytes that play diverse roles in immune responses, bridging innate and adaptive immunity. With growing interest in their potential for cancer immunotherapy, a comprehensive and inclusive exploration of γδ T cell families, their development, activation mechanisms, functions, therapeutic implications, and current treatments is essential. This review aims to provide an inclusive and thorough discussion of these topics. Through our discussion, we seek to uncover insights that may harbinger innovative immunotherapeutic strategies. Beginning with an overview of γδ T cell families including Vδ1, Vδ2, and Vδ3, this review highlights their distinct functional properties and contributions to anti-tumor immunity. Despite γδ T cells exhibiting both anti-tumor and pro-tumor activities, our review elucidates strategies to harness the anti-tumor potential of γδ T cells for therapeutic benefit. Moreover, our paper discusses the structural intricacies of the γδ T cell receptor and its significance in tumor recognition. Additionally, this review examines conventional and emerging γδ T cell therapies, encompassing both non-engineered and engineered approaches, with a focus on their efficacy and safety profiles in clinical trials. From multifunctional capabilities to diverse tissue distribution, γδ T cells play a pivotal role in immune regulation and surveillance. By analyzing current research findings, this paper offers insights into the dynamic landscape of γδ T cell-based immunotherapies, underscoring their promise as a potent armamentarium against cancer. Furthermore, by dissecting the complex biology of γδ T cells, we learn valuable information about the anti-cancer contributions of γδ T cells, as well as potential targets for immunotherapeutic interventions.

C. S, Devkota HP, Khadka D. Immune Modulation and Immunotherapy in Solid Tumors: Mechanisms of Resistance and Potential Therapeutic Strategies

Understanding the modulation of specific immune cells within the tumor microenvironment (TME) offers new hope in cancer treatments, especially in cancer immunotherapies. In recent years, immune modulation and resistance to immunotherapy have become critical challenges in cancer treatments. However, novel strategies for immune modulation have emerged as promising approaches for oncology due to the vital roles of the immunomodulators in regulating tumor progression and metastasis and modulating immunological responses to standard of care in cancer treatments. With the progress in immuno-oncology, a growing number of novel immunomodulators and mechanisms are being uncovered, offering the potential for enhanced clinical immunotherapy in the near future. Thus, gaining a comprehensive understanding of the broader context is essential. Herein, we particularly summarize the paradoxical role of tumor-related immune cells, focusing on how targeted immune cells and their actions are modulated by immunotherapies to overcome immunotherapeutic resistance in tumor cells. We also highlight the molecular mechanisms employed by tumors to evade the long-term effects of immunotherapeutic agents, rendering them ineffective.

Enhancing NK cell-mediated tumor killing of B7-H6+ cells with bispecific antibodies targeting allosteric sites of NKp30

In this work, we report the discovery and engineering of allosteric variable domains of the heavy chain (VHHs) derived from camelid immunization targeting NKp30, an activating receptor on natural killer (NK) cells. The aim was to enhance NK cell-mediated killing capacities by identifying VHHs that do not compete with the natural ligand of NKp30:B7-H6, thereby maximizing the recognition of B7-H6+ tumor cells. By relying on the DuoBody technology, bispecific therapeutic antibodies were engineered, creating a panel of bispecific antibodies against NKp30xEGFR (cetuximab moiety) or NKp30xHER2 (trastuzumab moiety), called natural killer cell engagers (NKCEs). These NKCEs were assessed for their killing capacities on B7-H6-expressing tumor cells. The results demonstrated an enhancement in NK killing capacities for both EGFR-expressing (HeLa) and HER2-expressing (SK-BR-3) cells, indicating the significance of the natural NKp30/B7-H6 axis in tumor recognition by the immune system. Notably, engineering NKCEs to allow natural recognition of B7-H6 was found to be more effective in promoting NKCE-mediated killing of B7-H6+ tumor cells via enhancement of cytokine release. This study highlights the potential of an enhanced-targeting approach, wherein tumor cell surface antigens are targeted while still enabling the natural recognition of the activating ligand (B7-H6) by the immune cells.

Emerging role of natural killer cells in non-AIDS comorbidities during suppressive antiretroviral therapy

PURPOSE OF REVIEW

Despite decades of insights about the role of natural killer (NK) cells in HIV infection, their persistent dysregulation despite antiretroviral therapy (ART) and its pathological consequences have been incompletely delineated. In this review, we highlight recent findings on the immunophenotypic and functional alterations of NK cells during virally suppressed HIV infection and explore their potential impact on promoting non-AIDS related comorbidities among people living with HIV (PLWH).

RECENT FINDINGS

Of note are the apparent persistent activated profiles of NK cells and pathophysiological events such as endoplasmic reticulum (ER) stress in potentially driving NK cell derived inflammation and tissue destruction. Additionally, recent interest in trained immunity is discussed as a potential mediator of ongoing NK cell dysregulation, contributing to comorbidities such as cardiovascular disease and neurocognitive disorders, both with an inflammatory etiology.

SUMMARY

Clinical and mechanistic evidence suggests persistent activation and dysregulation of the innate immune system are major drivers of non-AIDS comorbidities during virally suppressed HIV infection. Delineating the mechanistic role of specific components of innate immunity such as NK cells in inducing these pathologies will lead to the identification of novel therapeutic/prophylactic strategies to improve the overall health of PLWH.

Natural Killer Cell Infiltration in Prostate Cancers Predict Improved Patient Outcomes

BACKGROUND

Natural killer (NK) cells are non-antigen specific innate immune cells that can be redirected to targets of interest using multiple strategies, although none are currently FDA-approved. We sought to evaluate NK cell infiltration into tumors to develop an improved understanding of which histologies may be most amenable to NK cell-based therapies currently in the developmental pipeline.

METHODS

DNA (targeted/whole-exome) and RNA (whole-transcriptome) sequencing was performed from tumors from 45 cancer types (N = 90,916 for all cancers and N = 3365 for prostate cancer) submitted to Caris Life Sciences. NK cell fractions and immune deconvolution were inferred from RNA-seq data using quanTIseq. Real-world overall survival (OS) and treatment status was determined and Kaplan-Meier estimates were calculated. Statistical significance was determined using X2 and Mann-Whitney U tests, with corrections for multiple comparisons where appropriate.

RESULTS

In both a pan-tumor and prostate cancer (PCa) -specific setting, we demonstrated that NK cells represent a substantial proportion of the total cellular infiltrate (median range 2-9% for all tumors). Higher NK cell infiltration was associated with improved OS in 28 of 45 cancer types, including (PCa). NK cell infiltration was negatively correlated with common driver mutations and androgen receptor variants (AR-V7) in primary prostate biopsies, while positively correlated with negative immune regulators. Higher levels of NK cell infiltration were associated with patterns consistent with a compensatory anti-inflammatory response.

CONCLUSIONS

Using the largest available dataset to date, we demonstrated that NK cells infiltrate a broad range of tumors, including both primary and metastatic PCa. NK cell infiltration is associated with improved PCa patient outcomes. This study demonstrates that NK cells are capable of trafficking to both primary and metastatic PCa and are a viable option for immunotherapy approaches moving forward. Future development of strategies to enhance tumor-infiltrating NK cell-mediated cytolytic activity and activation while limiting inhibitory pathways will be key.

CD8α and CD70 mark human natural killer cell populations which differ in cytotoxicity

Natural Killer (NK) cells are innate immune cells that can directly detect and kill cancer cells. Understanding the molecular determinants regulating human NK cell cytotoxicity could help harness these cells for cancer therapies. To this end, we compared the transcriptome of NK cell clones derived from human peripheral blood, which were strongly or weakly cytotoxic against 721.221 and other target cells. After one month of culture, potent NK cell clones showed a significant upregulation in genes involved in cell cycle progression, suggesting that proliferating NK cells were particularly cytotoxic. Beyond two months of culture, NK cell clones which were strongly cytotoxic varied in their expression of 28 genes, including CD8Α and CD70; NK cells with high levels of CD70 expression were weakly cytotoxic while high CD8Α correlated with strong cytotoxicity. Thus, NK cells were cultured and sorted for expression of CD70 and CD8α, and in accordance with the transcriptomic data, CD70+ NK cells showed low cytotoxicity against 721.221 and K562 target cells. Cytotoxicity of CD70+ NK cells could be enhanced using blocking antibodies against CD70, indicating a direct role for CD70 in mediating low cytotoxicity. Furthermore, time-lapse microscopy of NK cell-target cell interactions revealed that CD8α+ NK cells have an increased propensity to sequentially engage and kill multiple target cells. Thus, these two markers relate to NK cell populations which are capable of potent killing (CD70-) or serial killing (CD8α+).

Regulation of NK cell development, maturation, and antitumor responses by the nuclear receptor NR2F6

Natural killer (NK) cell development and functionality rely on precise regulation by specific transcription factors (TFs). Our study demonstrates that the nuclear orphan receptor NR2F6 represses the expression of the activating receptor NKp46, an established key player in NK cell-mediated cytotoxicity during infection and tumor rejection. Despite normal NK cell development in the bone marrow, germline Nr2f6-deficient mice exhibit impaired terminal maturation of NK cells in the periphery. Short-term NK cell responses to lipopolysaccharide (LPS) activation, independent of NKp46, are subsequently reduced in Nr2f6-deficient mice. Conventional type 1 dendritic cells (cDC1) and macrophage populations are decreased in spleens of Nr2f6-deficient mice, subsequently, IL-15-dependent NK cell priming is limited. Administration of exogenous IL-15 in vitro and as IL-15 complex in vivo can compensate for these deficits, promoting terminal maturation of NK cells in Nr2f6-deficient mice. Subsequent transcriptome analysis reveals significant changes in gene expression profiles of NK cells from IL-15 complex treated Nr2f6-deficient mice, with notable alterations in essential NK genes such as Klrg1, Prdm1, Stat5a, Zeb2, and Prf1. Consequently, Nr2f6-deficient IL-15 complex-treated NK cells raise enhanced effector responses of IFNγ, Perforin, and Granzyme B upon ex vivo activation. Of importance, Nr2f6-deficient mice are protected against MHC-I negative B16-F10 melanoma lung metastasis formation, especially with IL-15 complex treatment, indicating the potential of NR2F6 to affect NKp46-dependent NK cell-mediated tumor surveillance. The therapeutic targeting of NR2F6 may be a promising strategy for boosting NKp46-dependent NK-cell-mediated tumor surveillance and metastasis.

Antitumor effects of natural killer cells derived from gene-engineered human-induced pluripotent stem cells on hepatocellular carcinoma

Mortality and recurrence rates of hepatocellular carcinoma (HCC) remain high despite the use of various treatment methods. Recently, cell-based immunotherapy using natural killer (NK) cells has attracted considerable attention in cancer immunotherapy. NK cells generated from induced pluripotent stem cells (iPSCs) are a new option for use as an NK cell resource. The eNK cells (HLCN061, developed by HEALIOS K.K.) are human iPSC-derived NK cells differentiated from clinical-grade iPSCs in which IL-15, CCR2B, CCL19, CD16a, and NKG2D have been introduced. In this study, we aimed to evaluate the potential of eNK cell therapy for HCC treatment. The analysis of eNK cells for cell surface and intracellular molecules revealed that antitumor-related surface molecules (TRAIL, CD226, and CD16) and intracellular cytotoxic factors (perforin, granzyme B, TNFα, and IFNγ) were highly expressed. In addition, eNK cells exhibited high cytotoxicity against HCC cell lines (HepG2, HuH7, and SNU-423), which are sensitive to NKG2D, TRAIL, and CD226. The TRAIL and perforin/granzyme B pathways are largely involved in this cytotoxic mechanism, as indicated by the reduction in cytotoxicity induced by TRAIL inhibitory antibodies and concanamycin A, which inhibits perforin/granzyme B-mediated cytotoxicity. Our data suggest that eNK cells, whose functions have been enhanced by genetic engineering, have the potential to improve HCC treatment.

Adoptive Cell Therapy from the Dish: Potentiating Induced Pluripotent Stem Cells

Background

The clinical success of autologous adoptive cell therapy (ACT) is substantial but wide application is challenged by the quality and quantity of the patient's immune cells and the need for personalized manufacturing processes. Induced pluripotent stem cells (iPSCs) can be differentiated into immune effectors and thus provide an alternative, allogeneic cell source for ACT. Here, we compare iPSC-derived immune effectors to their PBMC-derived counterparts and review iPSC-derived ACT products currently under preclinical and clinical development.

Summary

iPSC-derived T cells, NK cells, macrophages, and neutrophils largely mimic their PBMC-derived counterparts in terms of cell-surface marker expression and cytotoxic effector functions. iPSC-derived immune effectors can be engineered with chimeric antigen receptors and other activating receptors to redirect their cytotoxic potential specifically to tumor-associated antigens (TAAs). However, several differences between iPSC- and PBMC-derived immune effectors remain and have inspired additional engineering strategies to enhance the antitumor capacity of iPSC-derived immune effectors.

Key Messages

iPSCs can be engineered to facilitate the generation of immune effectors with homogenous specificity for TAAs and enhanced effector functions. TAA-specific and functionally enhanced iPSC-derived T and NK cells are currently undergoing clinical evaluation in phase 1 trials. Engineered iPSC-derived macrophages and neutrophils are in preclinical development.

Natural killer cell engagers for cancer immunotherapy

This review article explores the rapidly evolving field of bi-, tri-, and multi-specific NK cell engagers (NKCEs), highlighting their potential as a cutting-edge approach in cancer immunotherapy. NKCEs offer a significant advancement over conventional monoclonal antibodies (mAbs) by enhancing Antibody-Dependent Cellular Cytotoxicity (ADCC). They achieve this by stably and selectively binding to both NK cell activating receptors and tumor-associated antigens (TAAs). Unlike traditional mAbs, which depend on the relatively transient interaction between their Fc region and CD16a, NKCEs establish more robust connections with a range of activating receptors (e.g., CD16a, NKG2D, NKp30, NKp46, NKG2C) and inhibitory receptors (e.g., Siglec-7) on NK cells, thereby increasing cancer cell killing efficacy and specificity. This review article critically examines the strategies for engineering bi-, tri-, and multi-specific NKCEs for cancer immunotherapy, providing an in-depth analysis of the latest advancements in NKCE platform technologies currently under development by pharmaceutical and biotech companies and discussing the preclinical and clinical progress of these products. While NKCEs show great promise, the review underscores the need for continued research to optimize their therapeutic efficacy and to overcome obstacles related to NK cell functionality in cancer patients. Ultimately, this article presents an overview of the current landscape and future prospects of NKCE-based cancer immunotherapy, emphasizing its potential to revolutionize cancer treatment.

Natural killer cell-based therapies in neuroblastoma

Neuroblastoma (NB) is the most common extracranial solid tumor of childhood forming around 15 % of all pediatric tumors. Despite advances in the treatment of NB, high-risk patients still face a grave prognosis. Adoptive cell therapies based on NK cells are becoming an assistive treatment for such cases. Moreover, there is also evidence that NKT-based therapies have promising results in the management of NB. Lower complications in comparison with adoptive T cell therapies, various cell sources, and miscellaneous tumor recognition mechanisms are some of the advantages of NK- and NKT-based therapies. This review is dedicated to searching for recent advances in this field.

From LAL-D to MASLD: Insights into the role of LAL and Kupffer cells in liver inflammation and lipid metabolism

Metabolic dysfunction-associated steatotic liver disease (MASLD) is a prevalent liver pathology worldwide, closely associated with obesity and metabolic disorders. Increasing evidence suggests that macrophages play a crucial role in the development of MASLD. Several human studies have shown an inverse correlation between circulating lysosomal acid lipase (LAL) activity and MASLD. LAL is the sole enzyme known to degrade cholesteryl esters (CE) and triacylglycerols in lysosomes. Consequently, these substrates accumulate when their enzymatic degradation is impaired due to LAL deficiency (LALD). This study aimed to investigate the role of hepatic LAL activity and liver-resident macrophages (i.e., Kupffer cells (KC)) in MASLD. To this end, we analyzed lipid metabolism in hepatocyte-specific (hep)Lal-/- mice and depleted KC with clodronate treatment. When fed a high-fat/high-cholesterol diet (HF/HCD), hepLal-/- mice exhibited CE accumulation and an increased number of macrophages in the liver and significant hepatic inflammation. KC were depleted upon clodronate administration, whereas infiltrating/proliferating CD68-expressing macrophages were less affected. This led to exacerbated hepatic CE accumulation and dyslipidemia, as evidenced by increased LDL-cholesterol concentrations. Along with proteomic analysis of liver tissue, these findings indicate that hepatic LAL-D in HF/HCD-fed mice leads to macrophage infiltration into the liver and that KC depletion further exacerbates hepatic CE concentrations and dyslipidemia.

IL-27-engineered CAR.19-NK-92 cells exhibit enhanced therapeutic efficacy

Chimeric antigen receptor (CAR) engineering of natural killer (NK) cells has shown promising results in early-phase clinical studies. However, advancing CAR-NK cell therapeutic efficacy is imperative. In this study, we investigated the impact of a fourth-generation CD19-targeted CAR (CAR.19) coexpressing IL-27 on NK-92 cells. We observed a significant improvement in NK-92 cell proliferation and cytotoxicity activity against B-cell cancer cell lines, both in vitro and in a xenograft mouse B-cell lymphoma model. Our systematic transcriptome analysis of the activated NK-92 CAR variants further supports the potential of IL-27 in fourth-generation CARs to overcome limitations of NK cell-based targeted tumor therapies by providing essential growth and activation signals. Integrating IL-27 into CAR-NK cells emerges as a promising strategy to enhance their therapeutic potential and elicit robust responses against cancer cells. These findings contribute substantially to the mounting evidence supporting the potential of fourth-generation CAR engineering in advancing NK cell-based immunotherapies.

State of the Field: Cytotoxic Immune Cell Responses in C. neoformans and C. deneoformans Infection

Cryptococcus neoformans is an environmental pathogen that causes life-threatening disease in immunocompromised persons. The majority of immunological studies have centered on CD4+ T-cell dysfunction and associated cytokine signaling pathways, optimization of phagocytic cell function against fungal cells, and identification of robust antigens for vaccine development. However, a growing body of literature exists regarding cytotoxic cells, specifically CD8+ T-cells, Natural Killer cells, gamma/delta T-cells, NK T-cells, and Cytotoxic CD4+ T-cells, and their role in the innate and adaptive immune response during C. neoformans and C. deneoformans infection. In this review, we (1) provide a comprehensive report of data gathered from mouse and human studies on cytotoxic cell function and phenotype, (2) discuss harmonious and conflicting results on cellular responses in mice models and human infection, (3) identify gaps of knowledge in the field ripe for exploration, and (4) highlight how innovative immunological tools could enhance the study of cytotoxic cells and their potential immunomodulation during cryptococcosis.

The Role of Natural Killer Cells and Their Metabolism in HIV-1 Infection

Natural killer (NK) cells are multifaceted innate effector cells that critically influence antiviral immunity, and several protective NK cell features that modulate HIV-1 acquisition and viral control have been described. Chronic HIV-1 infection leads to NK cell impairment that has been associated with metabolic dysregulations. Therapeutic approaches targeting cellular immune metabolism represent potential novel interventions to reverse defective NK cell function in people living with HIV.

Current Developments in NK Cell Engagers for Cancer Immunotherapy: Focus on CD16A and NKp46

NK cells are specialized immune effector cells crucial for triggering immune responses against aberrant cells. Although recent advancements have concentrated on creating or releasing T-cell responses specific to tumor Ags, the clinical advantages of this approach have been limited to certain groups of patients and tumor types. This emphasizes the need for alternative strategies. One pioneering approach involves broadening and enhancing anti-tumor immune responses by targeting innate immunity. Consequently, the advent of bi-, tri-, and multi-specific Abs has facilitated the advancement of targeted cancer immunotherapies by redirecting immune effector cells to eradicate tumor cells. These Abs enable the simultaneous binding of surface Ags on tumor cells and the activation of receptors on innate immune cells, such as NK cells, with the ability to facilitate Ab-dependent cellular cytotoxicity to enhance their immunotherapeutic effectiveness in patients with solid tumors. Here, we review the recent advances in NK cell engagers (NKCEs) focusing on NK cell-activating receptors CD16A and NKp46. In addition, we provide an overview of the ongoing clinical trials investigating the safety, efficacy, and potential of NKCEs.

CAR-T and CAR-NK as cellular cancer immunotherapy for solid tumors

In the past decade, chimeric antigen receptor (CAR)-T cell therapy has emerged as a promising immunotherapeutic approach for combating cancers, demonstrating remarkable efficacy in relapsed/refractory hematological malignancies in both pediatric and adult patients. CAR-natural killer (CAR-NK) cell complements CAR-T cell therapy by offering several distinct advantages. CAR-NK cells do not require HLA compatibility and exhibit low safety concerns. Moreover, CAR-NK cells are conducive to "off-the-shelf" therapeutics, providing significant logistic advantages over CAR-T cells. Both CAR-T and CAR-NK cells have shown consistent and promising results in hematological malignancies. However, their efficacy against solid tumors remains limited due to various obstacles including limited tumor trafficking and infiltration, as well as an immuno-suppressive tumor microenvironment. In this review, we discuss the recent advances and current challenges of CAR-T and CAR-NK cell immunotherapies, with a specific focus on the obstacles to their application in solid tumors. We also analyze in depth the advantages and drawbacks of CAR-NK cells compared to CAR-T cells and highlight CAR-NK CAR optimization. Finally, we explore future perspectives of these adoptive immunotherapies, highlighting the increasing contribution of cutting-edge biotechnological tools in shaping the next generation of cellular immunotherapy.

Harnessing B7-H6 for Anticancer Immunotherapy: Expression, Pathways, and Therapeutic Strategies

Cancer therapies have evolved from traditional chemotherapy to more precise molecular-targeted immunotherapies, which have been associated with improved side effects and outcomes. These modern strategies rely on cancer-specific biomarkers that differentiate malignant from normal cells. The B7 family of immune checkpoint molecules is crucial for cancer immune evasion and a prime therapeutic target. B7-H6, a recently identified member of the B7 family, has emerged as a promising therapeutic target. Unlike other B7 proteins, B7-H6 is not expressed in healthy tissues but is upregulated in several cancers. It binds to NKp30, activating natural killer (NK) cells and triggering immune responses against cancer cells. This review explores the expression of B7-H6 in different cancers, the factors that regulate its expression, and its intrinsic and extrinsic pathways. Additionally, we discuss potential anticancer therapies targeting B7-H6, highlighting its significance in advancing precision medicine. Understanding the role of B7-H6 in cancer immunity may inform the development of appropriate therapies that exploit its cancer-specific expression.

Biomaterials-Boosted Immunotherapy for Osteosarcoma

Osteosarcoma (OS) is a primary malignant bone tumor that emanates from mesenchymal cells, commonly found in the epiphyseal end of long bones. The highly recurrent and metastatic nature of OS poses significant challenges to the efficacy of treatment and negatively affects patient prognosis. Currently, available clinical treatment strategies primarily focus on maximizing tumor resection and reducing localized symptoms rather than the complete eradication of malignant tumor cells to achieve ideal outcomes. The biomaterials-boosted immunotherapy for OS is characterized by high effectiveness and a favorable safety profile. This therapeutic approach manipulates the tumor microenvironments at the cellular and molecular levels to impede tumor progression. This review delves into the mechanisms underlying the treatment of OS, emphasizing biomaterials-enhanced tumor immunity. Moreover, it summarizes the immune cell phenotype and tumor microenvironment regulation, along with the ability of immune checkpoint blockade to activate the autoimmune system. Gaining a profound comprehension of biomaterials-boosted OS immunotherapy is imperative to explore more efficacious immunotherapy protocols and treatment options in this setting.

Natural killer cells: a future star for immunotherapy of head and neck squamous cell carcinoma

The interplay between immune components and the epithelium plays a crucial role in the development and progression of head and neck squamous cell carcinoma (HNSCC). Natural killer (NK) cells, one of the main tumor-killing immune cell populations, have received increasing attention in HNSCC immunotherapy. In this review, we explore the mechanism underlying the interplay between NK cells and HNSCC. A series of immune evasion strategies utilized by cancer cells restrict HNSCC infiltration of NK cells. Overcoming these limitations can fully exploit the antineoplastic potential of NK cells. We also investigated the tumor-killing efficacy of NK cell-based immunotherapies, immunotherapeutic strategies, and new results from clinical trials. Notably, cetuximab, the most essential component of NK cell-based immunotherapy, inhibits the epidermal growth factor receptor (EGFR) signaling pathway and activates the immune system in conjunction with NK cells, inducing innate effector functions and improving patient prognosis. In addition, we compiled information on other areas for the improvement of patient prognosis using anti-EGFR receptor-based monoclonal antibody drugs and the underlying mechanisms and prognoses of new immunotherapeutic strategies for the treatment of HNSCC.

NK cells modulate in vivo control of SARS-CoV-2 replication and suppression of lung damage

Natural killer (NK) cells play a critical role in virus control. However, it has remained largely unclear whether NK cell mobilization in SARS-CoV-2 infections is beneficial or pathologic. To address this deficit, we employed a validated experimental NK cell depletion non-human primate (NHP) model with SARS-CoV-2 Delta variant B.1.617.2 challenge. Viral loads (VL), NK cell numbers, activation, proliferation, and functional measures were evaluated in blood and tissues. In non-depleted (control) animals, infection rapidly induced NK cell expansion, activation, and increased tissue trafficking associated with VL. Strikingly, we report that experimental NK cell depletion leads to higher VL, longer duration of viral shedding, significantly increased levels of pro-inflammatory cytokines in the lungs, and overt lung damage. Overall, we find the first significant and conclusive evidence for NK cell-mediated control of SARS-CoV-2 virus replication and disease pathology. These data indicate that adjunct therapies for infection could largely benefit from NK cell-targeted approaches.

Natural Killer-Based Therapy: A Prospective Thought for Cancer Treatment Related to Diversified Drug Delivery Pathways

Immunotherapy has been a research hotspot due to its low side effects, long-lasting efficacy, and wide anti-tumor spectrum. Recently, NK cell-based immunotherapy has gained broad attention for its unique immunological character of tumor identification and eradication and low risk of graft-versus-host disease and cytokine storm. With the cooperation of a drug delivery system (DDS), NK cells activate tumoricidal activity by adjusting the balance of the activating and inhibitory signals on their surface after drug-loaded DDS administration. Moreover, NK cells or NK-derived exosomes can also be applied as drug carriers for distinct modification to promote NK activation and exert anti-tumor effects. In this review, we first introduce the source and classification of NK cells and describe the common activating and inhibitory receptors on their surface. Then, we summarize the strategies for activating NK cells in vivo through various DDSs. Finally, the application prospects of NK cells in tumor immunotherapy are also discussed.

NKp30 and NKG2D contribute to natural killer recognition of HIV-infected cells

Natural killer (NK) cells respond rapidly in early HIV-1 infection. HIV-1 prevention and control strategies harnessing NK cells could be enabled by mechanistic understanding of how NK cells recognize HIV-infected T cells. Here, we profiled the phenotype of human primary NK cells responsive to autologous HIV-1-infected CD4 + T cells in vitro. We characterized the patterns of NK cell ligand expression on CD4 + T cells at baseline and after infection with a panel of transmitted/founder HIV-1 strains to identify key receptor-ligand pairings. CRISPR editing of CD4 + T cells to knockout the NKp30 ligand B7-H6, or the NKG2D ligands MICB or ULBP2 reduced NK cell responses to HIV-infected cells in some donors. In contrast, overexpression of NKp30 or NKG2D in NK cells enhanced their targeting of HIV-infected cells. Collectively, we identified receptor-ligand pairs including NKp30:B7-H6 and NKG2D:MICB/ULBP2 that contribute to NK cell recognition of HIV-infected cells.

New Insights on Genes, Gluten, and Immunopathogenesis of Celiac Disease

Celiac disease (CeD) is a gluten-induced enteropathy that develops in genetically susceptible individuals upon consumption of cereal gluten proteins. It is a unique and complex immune disorder to study as the driving antigen is known and the tissue targeted by the immune reaction can be interrogated. This review integrates findings gained from genetic, biochemical, and immunologic studies, which together have revealed mechanisms of gluten peptide modification and HLA binding, thereby enabling a maladapted anti-gluten immune response. Observations in human samples combined with experimental mouse models have revealed that the gluten-induced immune response involves CD4+ T cells, cytotoxic CD8+ T cells, and B cells; their cross-talks are critical for the tissue-damaging response. The emergence of high-throughput technologies is increasing our understanding of the phenotype, location, and presumably function of the gluten-specific cells, which are all required to identify novel therapeutic targets and strategies for CeD.

ITAM-based receptors in natural killer cells

The ability of cells of the immune system to acquire features such as increased longevity and enhanced secondary responses was long thought to be restricted to cells of the adaptive immune system. Natural killer (NK) cells have challenged this notion by demonstrating that they can also gain adaptive features. This has been observed in both humans and mice during infection with cytomegalovirus (CMV). The generation of adaptive NK cells requires antigen-specific recognition of virally infected cells through stimulatory NK receptors. These receptors lack the ability to signal on their own and rather rely on adaptor molecules that contain ITAMs for driving signals. Here, we highlight our understanding of how these receptors influence the production of adaptive NK cells and propose areas in the field that merit further investigation.

A specific natural killer cells phenotypic signature associated to long term elite control of HIV infection

Elite controllers (ECs) are an exceptional group of people living with HIV (PLWH) that control HIV replication without therapy. Among the mechanisms involved in this ability, natural killer (NK)-cells have recently gained much attention. We performed an in-deep phenotypic analysis of NK-cells to search for surrogate markers associated with the long term spontaneous control of HIV. Forty-seven PLWH (22 long-term EC [PLWH-long-term elite controllers (LTECs)], 15 noncontrollers receiving antiretroviral treatment [ART] [PLWH-onART], and 10 noncontrollers cART-naïve [PLWH-offART]), and 20 uninfected controls were included. NK-cells homeostasis was analyzed by spectral flow cytometry using a panel of 15 different markers. Data were analyzed using FCSExpress and R software for unsupervised multidimensional analysis. Six different subsets of NK-cells were defined on the basis of CD16 and CD56 expression, and the multidimensional analysis revealed the existence of 68 different NK-cells clusters based on the expression levels of the 15 different markers. PLWH-offART presented the highest disturbance of NK-cells homeostasis and this was not completely restored by long-term ART. Interestingly, long term spontaneous control of HIV (PLWH-LTEC group) was associated with a specific profile of NK-cells homeostasis disturbance, characterized by an increase of CD16dimCD56dim subset when compared to uninfected controls (UC) group and also to offART and onART groups (p < 0.0001 for the global comparison), an increase of clusters C16 and C26 when compared to UC and onART groups (adjusted p-value < 0.05 for both comparisons), and a decrease of clusters C10 and C20 when compared to all the other groups (adjusted p-value < 0.05 for all comparisons). These findings may provide clues to elucidate markers of innate immunity with a relevant role in the long-term control of HIV.

Composition of fatty acids in a high-fat diet affects adipose tissue inflammation by inducing calreticulin on adipocytes and activating group 1 innate lymphoid cells

Obesity-induced adipose tissue inflammation plays a critical role in the development of metabolic diseases. For example, NK1.1+ group 1 innate lymphoid cells (G1-ILCs) in adipose tissues are activated in the early stages of inflammation in response to a high-fat diet (HFD). In this study, we examined whether the composition of fatty acids affected adipose inflammatory responses induced by an HFD. Mice were fed a stearic acid (C18:0)-rich HFD (HFD-S) or a linoleic acid (C18:2)-rich HFD (HFD-L). HFD-L-fed mice showed significant obesity compared with HFD-S-fed mice. Visceral and subcutaneous fat pads were enlarged and contained more NK1.1+KLRG1+ cells, indicating that G1-ILCs were activated in HFD-L-fed mice. We examined early changes in adipose tissues during the first week of HFD intake, and found that mice fed HFD-L showed increased levels of NK1.1+CD11b+KLRG1+ cells in adipose tissues. In adipose tissue culture, addition of 4-hydroxynonenal, the most frequent product of lipid peroxidation derived from unsaturated fatty acids, induced NK1.1+CD11b+CD27- cells. We found that calreticulin, a ligand for the NK activating receptor, was induced on the surface of adipocytes after exposure to 4-hydroxynonenal or a 1-week feeding with HFD-L. Thus, excess fatty acid intake and the activation of G1-ILCs initiate and/or modify adipose inflammation.

Tumor immunity: A brief overview of tumor‑infiltrating immune cells and research advances into tumor‑infiltrating lymphocytes in gynecological malignancies (Review)

Tumor immunity is a promising topic in the area of cancer therapy. The 'soil' function of the tumor microenvironment (TME) for tumor growth has attracted wide attention from scientists. Tumor-infiltrating immune cells in the TME, especially the tumor-infiltrating lymphocytes (TILs), serve a key role in cancer. Firstly, relevant literature was searched in the PubMed and Web of Science databases with the following key words: 'Tumor microenvironment'; 'TME'; 'tumor-infiltrating immunity cells'; 'gynecologic malignancies'; 'the adoptive cell therapy (ACT) of TILs'; and 'TIL-ACT' (https://pubmed.ncbi.nlm.nih.gov/). According to the title and abstract of the articles, relevant items were screened out in the preliminary screening. The most relevant selected items were of two types: All kinds of tumor-infiltrating immune cells; and advanced research on TILs in gynecological malignancies. The results showed that the subsets of TILs were various and complex, while each subpopulation influenced each other and their effects on tumor prognosis were diverse. Moreover, the related research and clinical trials on TILs were mostly concentrated in melanoma and breast cancer, but relatively few focused on gynecological tumors. In conclusion, the present review summarized the biological classification of TILs and the mechanisms of their involvement in the regulation of the immune microenvironment, and subsequently analyzed the development of tumor immunotherapy for TILs. Collectively, the present review provides ideas for the current treatment dilemma of gynecological tumor immune checkpoints, such as adverse reactions, safety, personal specificity and efficacy.

SUMMIT-FA: a new resource for improved transcriptome imputation using functional annotations

Transcriptome-wide association studies (TWAS) integrate gene expression prediction models and genome-wide association studies (GWAS) to identify gene-trait associations. The power of TWAS is determined by the sample size of GWAS and the accuracy of the expression prediction model. Here, we present a new method, the Summary-level Unified Method for Modeling Integrated Transcriptome using Functional Annotations (SUMMIT-FA), which improves gene expression prediction accuracy by leveraging functional annotation resources and a large expression quantitative trait loci (eQTL) summary-level dataset. We build gene expression prediction models in whole blood using SUMMIT-FA with the comprehensive functional database MACIE and eQTL summary-level data from the eQTLGen consortium. We apply these models to GWAS for 24 complex traits and show that SUMMIT-FA identifies significantly more gene-trait associations and improves predictive power for identifying "silver standard" genes compared to several benchmark methods. We further conduct a simulation study to demonstrate the effectiveness of SUMMIT-FA.

Building a Better Defense: Expanding and Improving Natural Killer Cells for Adoptive Cell Therapy

Natural killer (NK) cells have gained attention as a promising adoptive cell therapy platform for their potential to improve cancer treatments. NK cells offer distinct advantages over T-cells, including major histocompatibility complex class I (MHC-I)-independent tumor recognition and low risk of toxicity, even in an allogeneic setting. Despite this tremendous potential, challenges persist, such as limited in vivo persistence, reduced tumor infiltration, and low absolute NK cell numbers. This review outlines several strategies aiming to overcome these challenges. The developed strategies include optimizing NK cell expansion methods and improving NK cell antitumor responses by cytokine stimulation and genetic manipulations. Using K562 cells expressing membrane IL-15 or IL-21 with or without additional activating ligands like 4-1BBL allows "massive" NK cell expansion and makes multiple cell dosing and "off-the-shelf" efforts feasible. Further improvements in NK cell function can be reached by inducing memory-like NK cells, developing chimeric antigen receptor (CAR)-NK cells, or isolating NK-cell-based tumor-infiltrating lymphocytes (TILs). Memory-like NK cells demonstrate higher in vivo persistence and cytotoxicity, with early clinical trials demonstrating safety and promising efficacy. Recent trials using CAR-NK cells have also demonstrated a lack of any major toxicity, including cytokine release syndrome, and, yet, promising clinical activity. Recent data support that the presence of TIL-NK cells is associated with improved overall patient survival in different types of solid tumors such as head and neck, colorectal, breast, and gastric carcinomas, among the most significant. In conclusion, this review presents insights into the diverse strategies available for NK cell expansion, including the roles played by various cytokines, feeder cells, and culture material in influencing the activation phenotype, telomere length, and cytotoxic potential of expanded NK cells. Notably, genetically modified K562 cells have demonstrated significant efficacy in promoting NK cell expansion. Furthermore, culturing NK cells with IL-2 and IL-15 has been shown to improve expansion rates, while the presence of IL-12 and IL-21 has been linked to enhanced cytotoxic function. Overall, this review provides an overview of NK cell expansion methodologies, highlighting the current landscape of clinical trials and the key advancements to enhance NK-cell-based adoptive cell therapy.

Engineered 3D ex vivo models to recapitulate the complex stromal and immune interactions within the tumor microenvironment

Cancer thrives in a complex environment where interactions between cellular and acellular components, surrounding the tumor, play a crucial role in disease development and progression. Despite significant progress in cancer research, the mechanism driving tumor growth and therapeutic outcomes remains elusive. Two-dimensional (2D) cell culture assays and in vivo animal models are commonly used in cancer research and therapeutic testing. However, these models suffer from numerous shortcomings including lack of key features of the tumor microenvironment (TME) & cellular composition, cost, and ethical clearance. To that end, there is an increased interest in incorporating and elucidating the influence of TME on cancer progression. Advancements in 3D-engineered ex vivo models, leveraging biomaterials and microengineering technologies, have provided an unprecedented ability to reconstruct native-like bioengineered cancer models to study the heterotypic interactions of TME with a spatiotemporal organization. These bioengineered cancer models have shown excellent capabilities to bridge the gap between oversimplified 2D systems and animal models. In this review article, we primarily provide an overview of the immune and stromal cellular components of the TME and then discuss the latest state-of-the-art 3D-engineered ex vivo platforms aiming to recapitulate the complex TME features. The engineered TME model, discussed herein, are categorized into three main sections according to the cellular interactions within TME: (i) Tumor-Stromal interactions, (ii) Tumor-Immune interactions, and (iii) Complex TME interactions. Finally, we will conclude the article with a perspective on how these models can be instrumental for cancer translational studies and therapeutic testing.

The role of CD56bright NK cells in neurodegenerative disorders

Emerging evidence suggests a potential role for natural killer (NK) cells in neurodegenerative diseases, such as multiple sclerosis, Alzheimer's disease, Parkinson's disease and amyotrophic lateral sclerosis. However, the precise function of NK cells in these diseases remains ambiguous. The existence of two NK cell subsets, CD56bright and CD56dim NK cells, complicates the understanding of the contribution of NK cells in neurodegeneration as their functions within the context of neurodegenerative diseases may differ significantly. CD56bright NK cells are potent cytokine secretors and are considered more immunoregulatory and less terminally differentiated than their mostly cytotoxic CD56dim counterparts. Hence, this review focusses on NK cells, specifically on CD56bright NK cells, and their role in neurodegenerative diseases. Moreover, it explores the mechanisms underlying their ability to enter the central nervous system. By consolidating current knowledge, we aim to provide a comprehensive overview on the role of CD56bright NK cells in neurodegenerative diseases. Elucidating their impact on neurodegeneration may have implications for future therapeutic interventions, potentially ameliorating disease pathogenesis.

Cytotoxic CD8+ Temra cells show loss of chromatin accessibility at genes associated with T cell activation

As humans age, their memory T cell compartment expands due to the lifelong exposure to antigens. This expansion is characterized by terminally differentiated CD8+ T cells (Temra), which possess NK cell-like phenotype and are associated with chronic inflammatory conditions. Temra cells are predominantly driven by the sporadic reactivation of cytomegalovirus (CMV), yet their epigenomic patterns and cellular heterogeneity remain understudied. To address this gap, we correlated their gene expression profiles with chromatin openness and conducted single-cell transcriptome analysis, comparing them to other CD8+ subsets and CMV-responses. We confirmed that Temra cells exhibit high expression of genes associated with cytotoxicity and lower expression of costimulatory and chemokine genes. The data revealed that CMV-responsive CD8+ T cells (Tcmv) were predominantly derived from a mixed population of Temra and memory cells (Tcm/em) and shared their transcriptomic profiles. Using ATAC-seq analysis, we identified 1449 differentially accessible chromatin regions between CD8+ Temra and Tcm/em cells, of which only 127 sites gained chromatin accessibility in Temra cells. We further identified 51 gene loci, including costimulatory CD27, CD28, and ICOS genes, whose chromatin accessibility correlated with their gene expression. The differential chromatin regions Tcm/em cells were enriched in motifs that bind multiple transcriptional activators, such as Jun/Fos, NFkappaB, and STAT, whereas the open regions in Temra cells mainly contained binding sites of T-box transcription factors. Our single-cell analysis of CD8+CCR7loCD45RAhi sorted Temra population showed several subsets of Temra and NKT-like cells and CMC1+ Temra populations in older individuals that were shifted towards decreased cytotoxicity. Among CD8+CCR7loCD45RAhi sorted cells, we found a decreased proportion of IL7R+ Tcm/em-like and MAIT cells in individuals with high levels of CMV antibodies (CMVhi). These results shed new light on the molecular and cellular heterogeneity of CD8+ Temra cells and their relationship to aging and CMV infection.

An engineered NKp46 antibody for construction of multi-specific NK cell engagers

Recent developments in cancer immunotherapy have highlighted the potential of harnessing natural killer (NK) cells in the treatment of neoplastic malignancies. Of these, bispecific antibodies, and NK cell engager (NKCE) protein therapeutics in particular, have been of interest. Here, we used phage display and yeast surface display to engineer RLN131, a unique cross-reactive antibody that binds to human, mouse, and cynomolgus NKp46, an activating receptor found on NK cells. RLN131 induced proliferation and activation of primary NK cells, and was used to create bispecific NKCE constructs of varying configurations and valency. All NKCEs were able to promote greater NK cell cytotoxicity against tumor cells than an unmodified anti-CD20 monoclonal antibody, and activity was observed irrespective of whether the constructs contained a functional Fc domain. Competition binding and fine epitope mapping studies were used to demonstrate that RLN131 binds to a conserved epitope on NKp46, underlying its species cross-reactivity.

Genomic Features of Homologous Recombination Deficiency in Breast Cancer: Impact on Testing and Immunotherapy

Genomic instability is one of the well-established hallmarks of cancer. The homologous recombination repair (HRR) pathway plays a critical role in correcting the double-stranded breaks (DSB) due to DNA damage in human cells. Traditionally, the BRCA1/2 genes in the HRR pathway have been tested for their association with breast cancer. However, defects in the HRR pathway (HRD, also termed 'BRCAness'), which has up to 50 genes, have been shown to be involved in tumorigenesis and treatment susceptibility to poly-ADP ribose polymerase inhibitors (PARPis), platinum-based chemotherapy, and immune checkpoint inhibitors (ICIs). A reliable consensus on HRD scores is yet to be established. Emerging evidence suggests that only a subset of breast cancer patients benefit from ICI-based immunotherapy. Currently, albeit with limitations, the expression of programmed death-ligand 1 (PDL1) and tumor mutational burden (TMB) are utilized as biomarkers to predict the favorable outcomes of ICI therapy in breast cancer patients. Preclinical studies demonstrate an interplay between the HRR pathway and PDL1 expression. In this review, we outline the current understanding of the role of HRD in genomic instability leading to breast tumorigenesis and delineate outcomes from various clinical trials. Furthermore, we discuss potential strategies for combining HRD-targeted therapy with immunotherapy to achieve the best healthcare outcomes in breast cancer patients.

Natural Killer Cells and Cytotoxic T Cells: Complementary Partners against Microorganisms and Cancer

Natural killer (NK) cells and cytotoxic T (CD8+) cells are two of the most important types of immune cells in our body, protecting it from deadly invaders. While the NK cell is part of the innate immune system, the CD8+ cell is one of the major components of adaptive immunity. Still, these two very different types of cells share the most important function of destroying pathogen-infected and tumorous cells by releasing cytotoxic granules that promote proteolytic cleavage of harmful cells, leading to apoptosis. In this review, we look not only at NK and CD8+ T cells but also pay particular attention to their different subpopulations, the immune defenders that include the CD56+CD16dim, CD56dimCD16+, CD57+, and CD57+CD16+ NK cells, the NKT, CD57+CD8+, and KIR+CD8+ T cells, and ILCs. We examine all these cells in relation to their role in the protection of the body against different microorganisms and cancer, with an emphasis on their mechanisms and their clinical importance. Overall, close collaboration between NK cells and CD8+ T cells may play an important role in immune function and disease pathogenesis. The knowledge of how these immune cells interact in defending the body against pathogens and cancers may help us find ways to optimize their defensive and healing capabilities with methods that can be clinically applied.

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.

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

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

Immunoregulatory functions and therapeutic potential of natural killer cell-derived extracellular vesicles in chronic diseases

Extracellular vesicles (EVs) have been proven to play a significant immunoregulatory role in many chronic diseases, such as cancer and immune disorders. Among them, EVs derived from NK cells are an essential component of the immune cell functions. These EVs have been demonstrated to carry a variety of toxic proteins and nucleic acids derived from NK cells and play a therapeutic role in diseases like malignancies, liver fibrosis, and lung injury. However, natural NK-derived EVs (NKEVs) have certain limitations in disease treatment, such as low yield and poor targeting. Concurrently, NK cells exhibit characteristics of memory-like NK cells, which have stronger proliferative capacity, increased IFN-γ production, and enhanced cytotoxicity, making them more advantageous for disease treatment. Recent research has shifted its focus towards engineered extracellular vesicles and their potential to improve the efficiency, specificity, and safety of disease treatments. In this review, we will discuss the characteristics of NK-derived EVs and the latest advancements in disease therapy. Specifically, we will compare different cellular sources of NKEVs and explore the current status and prospects of memory-like NK cell-derived EVs and engineered NKEVs.

NK cell-based tumor immunotherapy

Natural killer (NK) cells display a unique inherent ability to identify and eliminate virus-infected cells and tumor cells. They are particularly powerful for elimination of hematological cancers, and have attracted considerable interests for therapy of solid tumors. However, the treatment of solid tumors with NK cells are less effective, which can be attributed to the very complicated immunosuppressive microenvironment that may lead to the inactivation, insufficient expansion, short life, and the poor tumor infiltration of NK cells. Fortunately, the development of advanced nanotechnology has provided potential solutions to these issues, and could improve the immunotherapy efficacy of NK cells. In this review, we summarize the activation and inhibition mechanisms of NK cells in solid tumors, and the recent advances in NK cell-based tumor immunotherapy boosted by diverse nanomaterials. We also propose the challenges and opportunities for the clinical application of NK cell-based tumor immunotherapy.

Impact of antibody architecture and paratope valency on effector functions of bispecific NKp30 x EGFR natural killer cell engagers

Natural killer (NK) cells emerged as a promising effector population that can be harnessed for anti-tumor therapy. In this work, we constructed NK cell engagers (NKCEs) based on NKp30-targeting single domain antibodies (sdAbs) that redirect the cytotoxic potential of NK cells toward epidermal growth factor receptor (EGFR)-expressing tumor cells. We investigated the impact of crucial parameters such as sdAb location, binding valencies, the targeted epitope on NKp30, and the overall antibody architecture on the redirection capacity. Our study exploited two NKp30-specific sdAbs, one of which binds a similar epitope on NKp30 as its natural ligand B7-H6, while the other sdAb addresses a non-competing epitope. For EGFR-positive tumor targeting, humanized antigen-binding domains of therapeutic antibody cetuximab were used. We demonstrate that NKCEs bivalently targeting EGFR and bivalently engaging NKp30 are superior to monovalent NKCEs in promoting NK cell-mediated tumor cell lysis and that the architecture of the NKCE can substantially influence killing capacities depending on the NKp30-targeting sdAb utilized. While having a pronounced impact on NK cell killing efficacy, the capabilities of triggering antibody-dependent cellular phagocytosis or complement-dependent cytotoxicity were not significantly affected comparing the bivalent IgG-like NKCEs with cetuximab. However, the fusion of sdAbs can have a slight impact on the NK cell release of immunomodulatory cytokines, as well as on the pharmacokinetic profile of the NKCE due to unfavorable spatial orientation within the molecule architecture. Ultimately, our findings reveal novel insights for the engineering of potent NKCEs triggering the NKp30 axis.

Altered NCR3 Splice Variants May Result in Deficient NK Cell Function in Renal Cell Carcinoma Patients

BACKGROUND/AIM

The natural killer (NK) cell function of patients with malignant tumours may be suppressed by deficiency, and the poor prognosis of renal cell carcinoma (RCC) patients may be due to escape from NK cell cytotoxicity, especially with respect to natural cytotoxicity receptors (NCRs) on the NK cell surface. However, the specific mechanism remains unclear. Therefore, in this study, we sought to explore the role of NCR, especially NCR3 splice variants, in the process of NK cell deficiency in RCC patients.

MATERIALS AND METHODS

We used flow cytometry to analyse the phenotype of NK cells from the peripheral blood and kidney tumour tissue of RCC patients. The NKp30-mediated NK cell killing function was measured by antibody-dependent cell-mediated cytotoxicity (ADCC) in NK and RCC cell coincubation. We extracted RNA from the peripheral blood mononuclear cells (PBMCs) of RCC patients and renal carcinoma tissue and carried out real-time quantitative PCR to detect the mRNA levels of NKp30a, NKp30b and NKp30c. mRNA expression levels of cytokines (IL-6, IL-8, IL-10, IL-18 and TGF-β) based on RNA extracted from renal carcinoma tissue and adjacent normal kidney tissues were also measured by real-time quantitative PCR.

RESULTS

Regarding the phenotype of NK cells in RCC patients, the proportion of NK cells in tumour tissue was significantly reduced, with changes in the NK cell proportion being most obvious in NKp30+ NK cells. Furthermore, the results of the ADCC function assay showed limited NKp30+ NK cell-mediated cytotoxicity in RCC patients. Through real-time quantitative PCR, we found lower expression of NKp30a and NKp30b, the immunostimulatory splice variants of NCR3 encoding NKp30, in RCC patients. Moreover, expression of activating cytokines (IL-6 and IL-8) in renal cancer tissue was decreased, though inhibitory cytokine (TGF-β) expression remained unchanged, which may result in an immunosuppressive cytokine microenvironment.

CONCLUSION

Decreased expression of immunostimulatory NCR3 splice variants and the inhibitory cytokine microenvironment in RCC patients may contribute to deficient NK cell cytotoxicity and renal carcinoma cell immune escape from NK cell killing, which may provide a theoretical basis for finding new immunotherapeutic targets for RCC.

OMIP-098: A 26 parameter, 24 color flow cytometry panel for human memory NK cell phenotyping

This 26-parameter flow cytometry panel has been developed and optimized to analyze NK cell phenotype, using cryopreserved peripheral blood mononuclear cells (PBMCs) from people living with and without human immunodeficiency virus (PLWH, PWOH). Our panel is designed for the analysis of several parameters of total NK cells and memory NK cell subsets including markers of maturation, activation, and proliferation, as well as activating and inhibitory receptors. Other tissues have not been tested (Table 1 ).

Killer instincts: natural killer cells as multifactorial cancer immunotherapy

Natural killer (NK) cells integrate heterogeneous signals for activation and inhibition using germline-encoded receptors. These receptors are stochastically co-expressed, and their concurrent engagement and signaling can adjust the sensitivity of individual cells to putative targets. Against cancers, which mutate and evolve under therapeutic and immunologic pressure, the diversity for recognition provided by NK cells may be key to comprehensive cancer control. NK cells are already being trialled as adoptive cell therapy and targets for immunotherapeutic agents. However, strategies to leverage their naturally occurring diversity and agility have not yet been developed. In this review, we discuss the receptors and signaling pathways through which signals for activation or inhibition are generated in NK cells, focusing on their roles in cancer and potential as targets for immunotherapies. Finally, we consider the impacts of receptor co-expression and the potential to engage multiple pathways of NK cell reactivity to maximize the scope and strength of antitumor activities.

Immunotherapies inducing immunogenic cell death in cancer: insight of the innate immune system

Cancer immunotherapies include monoclonal antibodies, cytokines, oncolytic viruses, cellular therapies, and other biological and synthetic immunomodulators. These are traditionally studied for their effect on the immune system's role in eliminating cancer cells. However, some of these therapies have the unique ability to directly induce cytotoxicity in cancer cells by inducing immunogenic cell death (ICD). Unlike general immune stimulation, ICD triggers specific therapy-induced cell death pathways, based on the release of damage-associated molecular patterns (DAMPs) from dying tumour cells. These activate innate pattern recognition receptors (PRRs) and subsequent adaptive immune responses, offering the promise of sustained anticancer drug efficacy and durable antitumour immune memory. Exploring how onco-immunotherapies can trigger ICD, enhances our understanding of their mechanisms and potential for combination strategies. This review explores the complexities of these immunotherapeutic approaches that induce ICD, highlighting their implications for the innate immune system, addressing challenges in cancer treatment, and emphasising the pivotal role of ICD in contemporary cancer research.

Similarities and divergences in the metabolism of immune cells in cancer and helminthic infections

Energetic and nutritional requirements play a crucial role in shaping the immune cells that infiltrate tumor and parasite infection sites. The dynamic interaction between immune cells and the microenvironment, whether in the context of tumor or helminth infection, is essential for understanding the mechanisms of immunological polarization and developing strategies to manipulate them in order to promote a functional and efficient immune response that could aid in the treatment of these conditions. In this review, we present an overview of the immune response triggered during tumorigenesis and establishment of helminth infections, highlighting the transition to chronicity in both cases. We discuss the energetic demands of immune cells under normal conditions and in the presence of tumors and helminths. Additionally, we compare the metabolic changes that occur in the tumor microenvironment and the infection site, emphasizing the alterations that are induced to redirect the immune response, thereby promoting the survival of cancer cells or helminths. This emerging discipline provides valuable insights into disease pathogenesis. We also provide examples of novel strategies to enhance immune activity by targeting metabolic pathways that shape immune phenotypes, with the aim of achieving positive outcomes in cancer and helminth infections.