A Fusion Protein Complex that Combines IL-12, IL-15, and IL-18 Signaling to Induce Memory-Like NK Cells for Cancer Immunotherapy

The power and the promise of CAR-mediated cell immunotherapy for clinical application in pancreatic cancer

BACKGROUND

Pancreatic cancer, referred to as the "monarch of malignancies," is a neoplastic growth mostly arising from the epithelial cells of the pancreatic duct and acinar cells. This particular neoplasm has a highly unfavorable prognosis due to its marked malignancy, inconspicuous initial manifestation, challenging early detection, rapid advancement, and limited survival duration. Cellular immunotherapy is the ex vivo culture and expansion of immune effector cells, granting them the capacity to selectively target malignant cells using specialized techniques. Subsequently, these modified cells are reintroduced into the patient's organism with the purpose of eradicating tumor cells and providing therapeutic intervention for cancer.

PRESENT SITUATION

Presently, the primary cellular therapeutic modalities employed in the treatment of pancreatic cancer encompass CAR T-cell therapy, TCR T-cell therapy, NK-cell therapy, and CAR NK-cell therapy.

AIM OF REVIEW

This review provides a concise overview of the mechanisms and primary targets associated with various cell therapies. Additionally, we will explore the prospective outlook of cell therapy in the context of treating pancreatic cancer.

Natural killer cell memory: challenges and opportunities for cancer immunotherapy

Substantial advancements have been made in recent years in comprehending immune memory, which enhances the secondary response through prior infections. The ability of vertebrate T and B lymphocytes to exhibit classic recall responses has long been regarded as a distinguishing characteristic. However, natural killer (NK) cells have been found to acquire immunological memory in a manner akin to T and B cells. The fundamental principles derived from the investigation of NK cell memory offer novel insights into innate immunity and have the potential to pave the way for innovative strategies to enhance therapeutic interventions against multiple diseases including cancer. Here, we reviewed the fundamental characteristics, memory development and regulatory mechanism of NK cell memory. Moreover, we will conduct a comprehensive evaluation of the accomplishments, obstacles, and future direction pertaining to the utilization of NK cell memory in the field of cancer immunotherapy.

DNMT1 inhibition improves the activity of memory-like natural killer cells by enhancing the level of autophagy

BACKGROUND

Acute myeloid leukemia (AML) is a common hematological tumor, but it is difficult to treat. DNMT1 is a DNA methyltransferase whose main function is to maintain stable DNA methylation during the DNA replication process. DNMT1 also plays an important role in AML, but its function in cytokine-induced memory-like natural killer (CIML NK) cell activity remains unclear.

METHODS AND RESULTS

In this study, we isolated primary NK cells from the peripheral blood of healthy volunteers and AML patients and treated them with 10 ng/mL IL-12, 50 ng/mL IL-15 and 50 ng/mL IL-18 to promote their differentiation into CIML NK cells. The activity of CIML NK cells was evaluated by RT‒qPCR, western blotting, ELISAs, and flow cytometry. DNMT1 was highly expressed in NK cells from AML patients. Knocking down DNMT1 significantly increased the expression of CD25, CD137, CD107a, IFN-γ, and TNF-α and increased the activity of CIML NK cells. Mechanistically, knocking down DNMT1 promoted autophagy by activating the AMPK/mTOR signaling pathway, thereby enhancing the activity of CIML NK cells and alleviating the progression of AML.

CONCLUSIONS

Our study revealed that the downregulation of DNMT expression may be a new target for the treatment of AML.

Nanoenabled IL-15 Superagonist via Conditionally Stabilized Protein-Protein Interactions Eradicates Solid Tumors by Precise Immunomodulation

Protein complexes are crucial structures that control many biological processes. Harnessing these structures could be valuable for therapeutic therapy. However, their instability and short lifespans need to be addressed for effective use. Here, we propose an innovative approach based on a functional polymeric cloak that coordinately anchors different domains of protein complexes and assembles them into a stabilized nanoformulation. As the polymer-protein association in the cloak is pH sensitive, the nanoformulation also allows targeting the release of the protein complexes to the acidic microenvironment of tumors for aiding their therapeutic performance. Building on this strategy, we developed an IL-15 nanosuperagonist (Nano-SA) by encapsulating the interleukin-15 (IL-15)/IL-15 Receptor α (IL-15Rα) complex (IL-15cx) for fostering synergistic transpresentation in tumors. Upon intravenous administration, Nano-SA stably circulated in the bloodstream, safeguarding the integrity of IL-15cx until reaching the tumor site, where it selectively released the active complex. Thus, Nano-SA significantly amplified the antitumor immune signals while diminishing systemic off-target effects. In murine colon cancer models, Nano-SA achieved potent immunotherapeutic effects, eradicating tumors without adverse side effects. These findings highlight the transformative potential of nanotechnology for advancing protein complex-based therapies.

Natural killer cell-based cancer immunotherapy: from basics to clinical trials

Cellular immunotherapy exploits the capacity of the human immune system in self-protection and surveillance to achieve the anti-tumor effects. Natural killer (NK) cells are lymphocytes of innate immune system and they display a unique inherent ability to identify and eliminate tumor cells. In this review, we first introduce the basic characteristics of NK cells in the physiological and pathological milieus, followed by a discussion of their effector function and immunosuppression in the tumor microenvironment. Clinical strategies and reports regarding NK cellular therapy are analyzed in the context of tumor treatment, especially against solid tumors. Given the widely studied T-cell therapy in the recent years, particularly the chimeric antigen receptor (CAR) T-cell therapy, we compare the technical features of NK- and T-cell based tumor therapies at the clinical front. Finally, the technical challenges and potential solutions for both T and NK cell-based immunotherapies in treating tumor malignancies are delineated. By overviewing its clinical applications, we envision the NK-cell based immunotherapy as an up-and-comer in cancer therapeutics.

Anatomical classification of advanced biliary tract cancer predicts programmed cell death protein 1 blockade efficacy

Background

Immune checkpoint blockade (ICB)-based immunotherapy has inspired new hope for advanced biliary tract cancer (BTC) treatment; however, there are no prior studies that primarily focus on different anatomical types of unresectable BTCs reacting differently to ICB.

Methods

We retrospectively collected data on advanced BTC patients who received anti-programmed cell death protein 1 (anti-PD1) therapy from two affiliated hospitals of Sun Yat-Sen university. The effects of anti-PD1 were compared for different anatomical sites. The GSE32225 and GSE132305 datasets were used to further analyze differences in the immune microenvironments between intrahepatic cholangiocarcinoma (ICC) and extrahepatic cholangiocarcinoma (ECC).

Results

A total of 198 advanced BTC patients were enrolled in this study, comprising 142 patients with ICC and 56 with other cancer types ("Others" group), including ECC and gallbladder cancer. In the anti-PD1 treated patients, the ICC group (n = 90) achieved longer median progression-free survival (mPFS) (9.5 vs. 6.2 months, p = 0.02) and median overall survival (mOS) (15.1 vs. 10.7 months, p = 0.02) than the Others group (n = 26). However, chemotherapy did not show different effects between the two groups (mOS: 10.6 vs. 12.1 months, p = 0.20; mPFS: 4.9 vs. 5.7 months, p = 0.83). For the first-line anti-PD1 therapy, the ICC group (n = 70) achieved higher mOS (16.0 vs. 11.8 months, p = 0.04) than the Others group (n = 19). Moreover, most chemokines, chemokine receptors, major histocompatibility complex molecules, immunostimulators, and immunoinhibitors were stronger in ICC than ECC; furthermore, CD8+ T cells and M1 macrophages were higher in ICC than ECC for most algorithms. The immune differential genes were mainly enriched in antigen processing and presentation as well as the cytokine receptors.

Conclusions

This study shows that the efficacy of anti-PD1 therapy was higher in ICC than in other types of BTCs. Differences in the immune-related molecules and cells between ICC and ECC indicate that ICC could benefit more from immunotherapy.

A "Prime and Expand" strategy using the multifunctional fusion proteins to generate memory-like NK cells for cell therapy

Adoptive cellular therapy (ACT) using memory-like (ML) natural killer (NK) cells, generated through overnight ex vivo activation with IL-12, IL-15, and IL-18, has shown promise for treating hematologic malignancies. We recently reported that a multifunctional fusion molecule, HCW9201, comprising IL-12, IL-15, and IL-18 domains could replace individual cytokines for priming human ML NK cell programming ("Prime" step). However, this approach does not include ex vivo expansion, thereby limiting the ability to test different doses and schedules. Here, we report the design and generation of a multifunctional fusion molecule, HCW9206, consisting of human IL-7, IL-15, and IL-21 cytokines. We observed > 300-fold expansion for HCW9201-primed human NK cells cultured for 14 days with HCW9206 and HCW9101, an IgG1 antibody, recognizing the scaffold domain of HCW9206 ("Expand" step). This expansion was dependent on both HCW9206 cytokines and interactions of the IgG1 mAb with CD16 receptors on NK cells. The resulting "Prime and Expand" ML NK cells exhibited elevated metabolic capacity, stable epigenetic IFNG promoter demethylation, enhanced antitumor activity in vitro and in vivo, and superior persistence in NSG mice. Thus, the "Prime and Expand" strategy represents a simple feeder cell-free approach to streamline manufacturing of clinical-grade ML NK cells to support multidose and off-the-shelf ACT.

Cytokines drive the formation of memory-like NK cell subsets via epigenetic rewiring and transcriptional regulation

Activation of natural killer (NK) cells with the cytokines interleukin-12 (IL-12), IL-15, and IL-18 induces their differentiation into memory-like (ML) NK cells; however, the underlying epigenetic and transcriptional mechanisms are unclear. By combining ATAC-seq, CITE-seq, and functional analyses, we discovered that IL-12/15/18 activation results in two main human NK fates: reprogramming into enriched memory-like (eML) NK cells or priming into effector conventional NK (effcNK) cells. eML NK cells had distinct transcriptional and epigenetic profiles and enhanced function, whereas effcNK cells resembled cytokine-primed cNK cells. Two transcriptionally discrete subsets of eML NK cells were also identified, eML-1 and eML-2, primarily arising from CD56bright or CD56dim mature NK cell subsets, respectively. Furthermore, these eML subsets were evident weeks after transfer of IL-12/15/18-activated NK cells into patients with cancer. Our findings demonstrate that NK cell activation with IL-12/15/18 results in previously unappreciated diverse cellular fates and identifies new strategies to enhance NK therapies.

IL-15 as a key regulator in NK cell-mediated immunotherapy for cancer: From bench to bedside

Interleukin 15 (IL-15) has emerged as a crucial factor in the relationship between natural killer (NK) cells and immunotherapy for cancer. This review article aims to provide a comprehensive understanding of the role of IL-15 in NK cell-mediated immunotherapy. First, the key role of IL-15 signaling in NK cell immunity is discussed, highlighting its regulation of NK cell functions and antitumor properties. Furthermore, the use of IL-15 or its analogs in clinical trials as a therapeutic strategy for various cancers, including the genetic modification of NK cells to produce IL-15, has been explored. The potential of IL-15-based therapies, such as chimeric antigen receptor (CAR) T and NK cell infusion along with IL-15 in combination with checkpoint inhibitors and other treatments, has been examined. This review also addresses the challenges and advantages of incorporating IL-15 in cell-based immunotherapy. Additionally, unresolved questions regarding the detection and biological significance of the soluble IL-15/IL-15Rα complex, as well as the potential role of IL-15/IL-15Rα in human cancer and the immunological consequences of prolonged exposure to soluble IL-15 for NK cells, are discussed.

Memory-like differentiation enhances NK cell responses against colorectal cancer

Metastatic (m) colorectal cancer (CRC) is an incurable disease with a poor prognosis and thus remains an unmet clinical need. Immune checkpoint blockade (ICB)-based immunotherapy is effective for mismatch repair-deficient (dMMR)/microsatellite instability-high (MSI-H) mCRC patients, but it does not benefit the majority of mCRC patients. NK cells are innate lymphoid cells with potent effector responses against a variety of tumor cells but are frequently dysfunctional in cancer patients. Memory-like (ML) NK cells differentiated after IL-12/IL-15/IL-18 activation overcome many challenges to effective NK cell anti-tumor responses, exhibiting enhanced recognition, function, and in vivo persistence. We hypothesized that ML differentiation enhances the NK cell responses to CRC. Compared to conventional (c) NK cells, ML NK cells displayed increased IFN-γ production against both CRC cell lines and primary patient-derived CRC spheroids. ML NK cells also exhibited improved killing of CRC target cells in vitro in short-term and sustained cytotoxicity assays, as well as in vivo in NSG mice. Mechanistically, enhanced ML NK cell responses were dependent on the activating receptor NKG2D as its blockade significantly decreased ML NK cell functions. Compared to cNK cells, ML NK cells exhibited greater antibody-dependent cytotoxicity when targeted against CRC by cetuximab. ML NK cells from healthy donors and mCRC patients exhibited increased anti-CRC responses. Collectively, our findings demonstrate that ML NK cells exhibit enhanced responses against CRC targets, warranting further investigation in clinical trials for mCRC patients, including those who have failed ICB.

Cancer immunity by tissue-resident type 1 innate lymphoid cells and killer innate-like T cells

Cancer progression can be restrained by tumor-infiltrating lymphocytes in a process termed cancer immunosurveillance. Based on how lymphocytes are activated and recruited to the tumor tissue, cancer immunity is either pre-wired, in which innate lymphocytes and innate-like T cells are directly recruited to and activated in tumors following their differentiation in primary lymphoid organs; or priming-dependent, in which conventional adaptive T cells are first primed by cognate antigens in secondary lymphoid organs before homing to and reactivated in tumors. While priming-dependent cancer immunity has been a focus of cancer immunology research for decades, in part due to historical preconception of cancer theory and tumor model choice as well as clinical success of conventional adaptive T cell-directed therapeutic programs, recent studies have revealed that pre-wired cancer immunity mediated by tissue-resident type 1 innate lymphoid cells (ILC1s) and killer innate-like T cells (ILTCKs) is an integral component of the cancer immunosurveillance process. Herein we review the distinct ontogenies and cancer-sensing mechanisms of ILC1s and ILTCKs in murine genetic cancer models as well as the conspicuously conserved responses in human malignancies. How ILC1s and ILTCKs may be targeted to broaden the scope of cancer immunotherapy beyond conventional adaptive T cells is also discussed.

Novel insights into TCR-T cell therapy in solid neoplasms: optimizing adoptive immunotherapy

Adoptive immunotherapy in the T cell landscape exhibits efficacy in cancer treatment. Over the past few decades, genetically modified T cells, particularly chimeric antigen receptor T cells, have enabled remarkable strides in the treatment of hematological malignancies. Besides, extensive exploration of multiple antigens for the treatment of solid tumors has led to clinical interest in the potential of T cells expressing the engineered T cell receptor (TCR). TCR-T cells possess the capacity to recognize intracellular antigen families and maintain the intrinsic properties of TCRs in terms of affinity to target epitopes and signal transduction. Recent research has provided critical insight into their capability and therapeutic targets for multiple refractory solid tumors, but also exposes some challenges for durable efficacy. In this review, we describe the screening and identification of available tumor antigens, and the acquisition and optimization of TCRs for TCR-T cell therapy. Furthermore, we summarize the complete flow from  laboratory to clinical applications of TCR-T cells. Last, we emerge future prospects for improving therapeutic efficacy in cancer world with combination therapies or TCR-T derived products. In conclusion, this review depicts our current understanding of TCR-T cell therapy in solid neoplasms, and provides new perspectives for expanding its clinical applications and improving therapeutic efficacy.

Bioengineering strategies to enhance the interleukin-18 bioactivity in the modern toolbox of cancer immunotherapy

Cytokines are the first modern immunotherapeutic agents used for activation immunotherapy. Interleukin-18 (IL-18) has emerged as a potent anticancer immunostimulatory cytokine over the past three decades. IL-18, structurally is a stable protein with very low toxicity at biological doses. IL-18 promotes the process of antigen presentation and also enhances innate and acquired immune responses. It can induce the production of proinflammatory cytokines and increase tumor infiltration of effector immune cells to revert the immunosuppressive milieu of tumors. Furthermore, IL-18 can reduce tumorigenesis, suppress tumor angiogenesis, and induce tumor cell apoptosis. These characteristics present IL-18 as a promising option for cancer immunotherapy. Although several preclinical studies have reported the immunotherapeutic potential of IL-18, clinical trials using it as a monotherapy agent have reported disappointing results. These results may be due to some biological characteristics of IL-18. Several bioengineering approaches have been successfully used to correct its defects as a bioadjuvant. Currently, the challenge with this anticancer immunotherapeutic agent is mainly how to use its capabilities in a rational combinatorial therapy for clinical applications. The present study discussed the strengths and weaknesses of IL-18 as an immunotherapeutic agent, followed by comprehensive review of various promising bioengineering approaches that have been used to overcome its disadvantages. Finally, this study highlights the promising application of IL-18 in modern combinatorial therapies, such as chemotherapy, immune checkpoint blockade therapy, cell-based immunotherapy and cancer vaccines to guide future studies, circumventing the barriers to administration of IL-18 for clinical applications, and bring it to fruition as a potent immunotherapy agent in cancer treatment.

Advances in screening, synthesis, modification, and biomedical applications of peptides and peptide aptamers

Peptides and peptide aptamers have emerged as promising molecules for a wide range of biomedical applications due to their unique properties and versatile functionalities. The screening strategies for identifying peptides and peptide aptamers with desired properties are discussed, including high-throughput screening, display screening technology, and in silico design approaches. The synthesis methods for the efficient production of peptides and peptide aptamers, such as solid-phase peptide synthesis and biosynthesis technology, are described, along with their advantages and limitations. Moreover, various modification techniques are explored to enhance the stability, specificity, and pharmacokinetic properties of peptides and peptide aptamers. This includes chemical modifications, enzymatic modifications, biomodifications, genetic engineering modifications, and physical modifications. Furthermore, the review highlights the diverse biomedical applications of peptides and peptide aptamers, including targeted drug delivery, diagnostics, and therapeutic. This review provides valuable insights into the advancements in screening, synthesis, modification, and biomedical applications of peptides and peptide aptamers. A comprehensive understanding of these aspects will aid researchers in the development of novel peptide-based therapeutics and diagnostic tools for various biomedical challenges.

Natural killer cells immunosenescence and the impact of lifestyle management

Natural killer cells (NKs) are lymphocytes of the innate immune system that quickly respond to viruses, infections, and tumors during their short cell life cycle. However, it was recently found that NKs undergo quantitative, distributional, structural, and functional phenotypic changes during aging that suppress immune responses, which is known as immunosenescence. The aging host environment, cytokine regulation, cytomegalovirus status, and hypothalamic‒pituitary‒adrenal axis have significant effects on NK function. Different lifestyle management interventions modulate the number and cytotoxic activity of NKs, which are essential for rebuilding the immune barrier against pathogens in elderly individuals. Based on recent studies, we review the phenotypic changes of and potential threats of NKs during aging and explore the underlying mechanisms. By summarizing the effects of lifestyle management on NKs and their application prospects, we aim to provide evidence for enhancing immune system function against immune diseases in elderly individuals.

The role of pyroptosis and gasdermin family in tumor progression and immune microenvironment

Pyroptosis, an inflammatory programmed cell death, distinguishes itself from apoptosis and necroptosis and has drawn increasing attention. Recent studies have revealed a correlation between the expression levels of many pyroptosis-related genes and both tumorigenesis and progression. Despite advancements in cancer treatments such as surgery, radiotherapy, chemotherapy, and immunotherapy, the persistent hallmark of cancer enables malignant cells to elude cell death and develop resistance to therapy. Recent findings indicate that pyroptosis can overcome apoptosis resistance amplify treatment-induced tumor cell death. Moreover, pyroptosis triggers antitumor immunity by releasing pro-inflammatory cytokines, augmenting macrophage phagocytosis, and activating cytotoxic T cells and natural killer cells. Additionally, it transforms "cold" tumors into "hot" tumors, thereby enhancing the antitumor effects of various treatments. Consequently, pyroptosis is intricately linked to tumor development and holds promise as an effective strategy for boosting therapeutic efficacy. As the principal executive protein of pyroptosis, the gasdermin family plays a pivotal role in influencing pyroptosis-associated outcomes in tumors and can serve as a regulatory target. This review provides a comprehensive summary of the relationship between pyroptosis and gasdermin family members, discusses their roles in tumor progression and the tumor immune microenvironment, and analyses the underlying therapeutic strategies for tumor treatment based on pyroptotic cell death.

Cytokine-Induced Memory-Like NK Cells: Emerging strategy for AML immunotherapy

Acute myeloid leukemia (AML) is a heterogeneous disease developed from the malignant expansion of myeloid precursor cells in the bone marrow and peripheral blood. The implementation of intensive chemotherapy and hematopoietic stem cell transplantation (HSCT) has improved outcomes associated with AML, but relapse, along with suboptimal outcomes, is still a common scenario. In the past few years, exploring new therapeutic strategies to optimize treatment outcomes has occurred rapidly. In this regard, natural killer (NK) cell-based immunotherapy has attracted clinical interest due to its critical role in immunosurveillance and their capabilities to target AML blasts. NK cells are cytotoxic innate lymphoid cells that mediate anti-viral and anti-tumor responses by producing pro-inflammatory cytokines and directly inducing cytotoxicity. Although NK cells are well known as short-lived innate immune cells with non-specific responses that have limited their clinical applications, the discovery of cytokine-induced memory-like (CIML) NK cells could overcome these challenges. NK cells pre-activated with the cytokine combination IL-12/15/18 achieved a long-term life span with adaptive immunity characteristics, termed CIML-NK cells. Previous studies documented that using CIML-NK cells in cancer treatment is safe and results in promising outcomes. This review highlights the current application, challenges, and opportunities of CIML-NK cell-based therapy in AML.

Memory-like Differentiation, Tumor-Targeting mAbs, and Chimeric Antigen Receptors Enhance Natural Killer Cell Responses to Head and Neck Cancer

PURPOSE

Head and neck squamous cell carcinoma (HNSCC) is an aggressive tumor with low response rates to frontline PD-1 blockade. Natural killer (NK) cells are a promising cellular therapy for T cell therapy-refractory cancers, but are frequently dysfunctional in patients with HNSCC. Strategies are needed to enhance NK cell responses against HNSCC. We hypothesized that memory-like (ML) NK cell differentiation, tumor targeting with cetuximab, and engineering with an anti-EphA2 (Erythropoietin-producing hepatocellular receptor A2) chimeric antigen receptor (CAR) enhance NK cell responses against HNSCC.

EXPERIMENTAL DESIGN

We generated ML NK and conventional (c)NK cells from healthy donors, then evaluated their ability to produce IFNγ, TNF, degranulate, and kill HNSCC cell lines and primary HNSCC cells, alone or in combination with cetuximab, in vitro and in vivo using xenograft models. ML and cNK cells were engineered to express anti-EphA2 CAR-CD8A-41BB-CD3z, and functional responses were assessed in vitro against HNSCC cell lines and primary HNSCC tumor cells.

RESULTS

Human ML NK cells displayed enhanced IFNγ and TNF production and both short- and long-term killing of HNSCC cell lines and primary targets, compared with cNK cells. These enhanced responses were further improved by cetuximab. Compared with controls, ML NK cells expressing anti-EphA2 CAR had increased IFNγ and cytotoxicity in response to EphA2+ cell lines and primary HNSCC targets.

CONCLUSIONS

These preclinical findings demonstrate that ML differentiation alone or coupled with either cetuximab-directed targeting or EphA2 CAR engineering were effective against HNSCCs and provide the rationale for investigating these combination approaches in early phase clinical trials for patients with HNSCC.

STING signaling promotes NK cell antitumor immunity and maintains a reservoir of TCF-1+ NK cells

Natural killer (NK) cells are cytotoxic innate lymphocytes that eradicate tumor cells. Inducing durable antitumor immune responses by NK cells represents a major priority of cancer immunotherapy. While cytosolic DNA sensing plays an essential role in initiating antitumor immunity, the role of NK cell-intrinsic STING signaling remains unclear. Here, we find that NK cell-intrinsic STING promotes antitumor responses and maintains a reservoir of TCF-1+ NK cells. In contrast, tumor cell-intrinsic cGAS and mtDNA are required for NK cell antitumor activity, indicating that tumor mtDNA recognition by cGAS partially triggers NK cell-intrinsic STING activation. Moreover, addition of cGAMP enables STING activation and type I interferon production in NK cells, thereby supporting the activation of NK cells in vitro. In humans, STING agonism promotes the expansion of TCF-1+ NK cells. This study provides insight into understanding how STING signaling drives NK cell antitumor immunity and the development of NK cell-based cancer immunotherapy.

The screening, identification, design and clinical application of tumor-specific neoantigens for TCR-T cells

Recent advances in neoantigen research have accelerated the development of tumor immunotherapies, including adoptive cell therapies (ACTs), cancer vaccines and antibody-based therapies, particularly for solid tumors. With the development of next-generation sequencing and bioinformatics technology, the rapid identification and prediction of tumor-specific antigens (TSAs) has become possible. Compared with tumor-associated antigens (TAAs), highly immunogenic TSAs provide new targets for personalized tumor immunotherapy and can be used as prospective indicators for predicting tumor patient survival, prognosis, and immune checkpoint blockade response. Here, the identification and characterization of neoantigens and the clinical application of neoantigen-based TCR-T immunotherapy strategies are summarized, and the current status, inherent challenges, and clinical translational potential of these strategies are discussed.

Research progress of interleukin-15 in cancer immunotherapy

Interleukin-15 (IL-15) is a cytokine that belongs to the interleukin-2 (IL-2) family and is essential for the development, proliferation, and activation of immune cells, including natural killer (NK) cells, T cells and B cells. Recent studies have revealed that interleukin-15 also plays a critical role in cancer immunotherapy. Interleukin-15 agonist molecules have shown that interleukin-15 agonists are effective in inhibiting tumor growth and preventing metastasis, and some are undergoing clinical trials. In this review, we will summarize the recent progress in interleukin-15 research over the past 5 years, highlighting its potential applications in cancer immunotherapy and the progress of interleukin-15 agonist development.

Allogeneic natural killer cell therapy

Interest in adoptive cell therapy for treating cancer is exploding owing to early clinical successes of autologous chimeric antigen receptor (CAR) T lymphocyte therapy. However, limitations using T cells and autologous cell products are apparent as they (1) take weeks to generate, (2) utilize a 1:1 donor-to-patient model, (3) are expensive, and (4) are prone to heterogeneity and manufacturing failures. CAR T cells are also associated with significant toxicities, including cytokine release syndrome, immune effector cell-associated neurotoxicity syndrome, and prolonged cytopenias. To overcome these issues, natural killer (NK) cells are being explored as an alternative cell source for allogeneic cell therapies. NK cells have an inherent ability to recognize cancers, mediate immune functions of killing and communication, and do not induce graft-versus-host disease, cytokine release syndrome, or immune effector cell-associated neurotoxicity syndrome. NK cells can be obtained from blood or cord blood or be derived from hematopoietic stem and progenitor cells or induced pluripotent stem cells, and can be expanded and cryopreserved for off-the-shelf availability. The first wave of point-of-care NK cell therapies led to the current allogeneic NK cell products being investigated in clinical trials with promising preliminary results. Basic advances in NK cell biology and cellular engineering have led to new translational strategies to block inhibition, enhance and broaden target cell recognition, optimize functional persistence, and provide stealth from patients' immunity. This review details NK cell biology, as well as NK cell product manufacturing, engineering, and combination therapies explored in the clinic leading to the next generation of potent, off-the-shelf cellular therapies for blood cancers.

Differential Expression of LLT1, SLAM Receptors CS1 and 2B4 and NCR Receptors NKp46 and NKp30 in Pediatric Acute Lymphoblastic Leukemia (ALL)

Acute lymphoblastic leukemia (ALL) represents the most common pediatric cancer. Most patients (85%) develop B-cell ALL; however, T-cell ALL tends to be more aggressive. We have previously identified 2B4 (SLAMF4), CS1 (SLAMF7) and LLT1 (CLEC2D) that can activate or inhibit NK cells upon the interaction with their ligands. In this study, the expression of 2B4, CS1, LLT1, NKp30 and NKp46 was determined. The expression profiles of these immune receptors were analyzed in the peripheral blood mononuclear cells of B-ALL and T-ALL subjects by single-cell RNA sequencing data obtained from the St. Jude PeCan data portal that showed increased expression of LLT1 in B-ALL and T-ALL subjects. Whole blood was collected from 42 pediatric ALL subjects at diagnosis and post-induction chemotherapy and 20 healthy subjects, and expression was determined at the mRNA and cell surface protein level. A significant increase in cell surface LLT1 expression in T cells, monocytes and NK cells was observed. Increased expression of CS1 and NKp46 was observed on monocytes of ALL subjects at diagnosis. A decrease of LLT1, 2B4, CS1 and NKp46 on T cells of ALL subjects was also observed post-induction chemotherapy. Furthermore, mRNA data showed altered expression of receptors in ALL subjects pre- and post-induction chemotherapy treatment. The results indicate that the differential expression of the receptors/ligand may play a role in the T-cell- and NK-cell-mediated immune surveillance of pediatric ALL.

A novel interleukin-2-based fusion molecule, HCW9302, differentially promotes regulatory T cell expansion to treat atherosclerosis in mice

Atherosclerosis is a chronic inflammatory disease caused by deposition of oxidative low-density lipoprotein (LDL) in the arterial intima which triggers the innate immune response through myeloid cells such as macrophages. Regulatory T cells (Tregs) play an important role in controlling the progression or regression of atherosclerosis by resolving macrophage-mediated inflammatory functions. Interleukin-2 (IL-2) signaling is essential for homeostasis of Tregs. Since recombinant IL-2 has an unfavorable pharmacokinetic profile limiting its therapeutic use, we constructed a fusion protein, designated HCW9302, containing two IL-2 domains linked by an extracellular tissue factor domain. We found that HCW9302 exhibited a longer serum half-life with an approximately 1000-fold higher affinity for the IL-2Rα than IL-2. HCW9302 could be administered to mice at a dosing range that expanded and activated Tregs but not CD4⁺ effector T cells. In an ApoE^-/- mouse model, HCW9302 treatment curtailed the progression of atherosclerosis through Treg activation and expansion, M2 macrophage polarization and myeloid-derived suppressor cell induction. HCW9302 treatment also lessened inflammatory responses in the aorta. Thus, HCW9302 is a potential therapeutic agent to expand and activate Tregs for treatment of inflammatory and autoimmune diseases.

Metabolic regulation of NK cell function: implications for immunotherapy

Natural killer (NK) cells are innate immune lymphocytes capable of rapidly responding to tumors and infection without prior sensitization. There is increasing interest and success in harnessing NK cell function for the treatment of disease, in particular cancers. NK cell activation is dependent on integration of signals through cytokine and germline-encoded activating and inhibitory receptors. The availability of metabolic fuels and pathways is required for NK effector functions including proliferation, killing, and production of interferon gamma (IFN-γ). An understanding of NK cell immunometabolism is thus essential for developing immunotherapy approaches that will allow for optimal effector functions in patients. Studies in mice and humans have demonstrated stimulation-dependent metabolic changes that are required for NK cell function. Here we review the most recent findings in NK cell immunometabolism relevant to disease models and translation to therapy of patients.

Contribution of natural killer cells in innate immunity against colorectal cancer

Natural killer cells are members of the innate immune system and promote cytotoxic activity against tumor or infected cells independently from MHC recognition. NK cells are modulated by the expression of activator/inhibitory receptors. The ratio of this activator/inhibitory receptors is responsible for the cytotoxic activity of NK cells toward the target cells. Owing to the potent anti-tumor properties of NK cells, they are considered as interesting approach in tumor treatment. Colorectal cancer (CRC) is the second most common cause of death in the world and the incidence is about 2 million new cases per year. Metastatic CRC is accompanied by a poor prognosis with less than three years of overall survival. Chemotherapy and surgery are the most adopted treatments. Besides, targeted therapy and immune checkpoint blockade are novel approach to CRC treatment. In these patients, circulating NK cells are a prognostic marker. The main target of CRC immune cell therapy is to improve the tumor cell's recognition and elimination by immune cells. Adaptive NK cell therapy is the milestone to achieve the purpose. Allogeneic NK cell therapy has been widely investigated within clinical trials. In this review, we focus on the NK related approaches including CAR NK cells, cell-based vaccines, monoclonal antibodies and immunomodulatory drugs against CRC tumoral cells.

Metabolic hallmarks of natural killer cells in the tumor microenvironment and implications in cancer immunotherapy

Natural killer (NK) cells belong to the early responder group against cancerous cells and viral infection. Emerging evidence reveals that distinct metabolic reprogramming occurs concurrently with activation and memory formation of NK cells. However, metabolism of NK cells is disturbed in the tumor immune microenvironment, which may promote tumor progression while limiting immunotherapy responses. In this review, we highlight how cell metabolism influences NK cell activity, the key molecular regulators of NK cell metabolism, and emerging strategies to alter metabolism to improve cytotoxicity of NK cells to kill tumor cells for cancer patients.

The application of Interleukin-2 family cytokines in tumor immunotherapy research

The Interleukin-2 Family contains six kinds of cytokines, namely IL-2, IL-15, IL-4, IL-7, IL-9, and IL-21, all of which share a common γ chain. Many cytokines of the IL-2 family have been reported to be a driving force in immune cells activation. Therefore, researchers have tried various methods to study the anti-tumor effect of cytokines for a long time. However, due to the short half-life, poor stability, easy to lead to inflammatory storms and narrow safety treatment window of cytokines, this field has been tepid. In recent years, with the rapid development of protein engineering technology, some engineered cytokines have a significant effect in tumor immunotherapy, showing an irresistible trend of development. In this review, we will discuss the current researches of the IL-2 family and mainly focus on the application and achievements of engineered cytokines in tumor immunotherapy.

Breast cancer combined prognostic model based on lactate metabolism genes

To investigate the impact of lactate metabolism genes, lactate metabolism-related genes (LMRG), and immune infiltrating cells on the prognosis of breast cancer. LMRG was identified via single-cell sequencing. Immune cell infiltration was obtained by the CIBERSORT method. The prognostic genes were chosen by cox regression and the least absolute selection operator approach. lactate metabolism-associated immune-infiltrating cells was determined by difference analysis. The GSE20685 dataset was used as an external validation cohort. The model's prognostic usefulness was evaluated utilizing survival, immunological microenvironment, and drug sensitivity assessments. NDUFAF6 was most associated with breast cancer prognosis. We obtained a total of 450 LMRG. SUSD3, IL18, MAL2, and CDKN1C comprised the Model2. NK cell activation was most relevant to lactate metabolism. The combined prognostic model outperformed the individual model, with the area under the curve ranging from 0.7 to 0.8 in all three cohorts. The lactate metabolism-related combination model assisted in evaluating breast cancer prognosis, providing new insights for treatment, particularly immunotherapy.

Down-regulation of IL-32γ expression reduces killing effect of natural killer cells on esophageal carcinoma cells

BACKGROUND

Interleukin (IL)-32γ is highly expressed in activated natural killer (NK) cells in esophageal cancer. However, it is not clear whether the expression level of IL-32γ in NK cells affects their killing effect on esophageal cancer cells.

AIM

To investigate the role of IL-32γ in the anti-tumor effect of NK cells in esophageal cancer.

METHODS

After transfecting NK-92 cells with shRNA targeting IL-32γ (shIL-32γ), the NK-92 cells were co-cultured with esophageal cancer cells EC9706 and TE-1, respectively. EC9706 and TE-1 cells were then collected; cell viability was measured by cell counting kit-8 (CCK-8) assay, cell proliferation was detected by 5-ethynyl-2'-deoxyuridine (EDU) assay, cell apoptosis was detected by flow cytometry, and the expression of apoptosis-related proteins B-cell lymphoma-2 (Bcl-2), Bcl-2-associated X (Bax), cleaved cysteine-containing aspartate-specific proteases 3 (caspase 3), tumor necrosis factor receptor superfamily member 6 (FAS), death receptor 3 (DR3), and tumor necrosis factor receptor 2 (TNFR2) was detected by Western blot.

RESULTS

After IL-32γ deletion in NK-92 cells, the cell viability and the EDU positive cells in EC9706 and TE-1 cells in the co-culture system were increased (P < 0.01), the expression level of Bcl-2 was increased (P < 0.01), and the expression levels of Bax, cleaved-caspase 3, FAS, DR3, and TNFR2 were all decreased (P < 0.01).

CONCLUSION

Knockdown of IL-32γ attenuates the anti-tumor effect of NK-92 cells, which may be related to the inhibition of death receptor expression and caspase-3 activation in esophageal cancer cells.

Natural killer cells in clinical development as non-engineered, engineered, and combination therapies

Natural killer (NK) cells are unique immune effectors able to kill cancer cells by direct recognition of surface ligands, without prior sensitization. Allogeneic NK transfer is a highly valuable treatment option for cancer and has recently emerged with hundreds of clinical trials paving the way to finally achieve market authorization. Advantages of NK cell therapies include the use of allogenic cell sources, off-the-shelf availability, and no risk of graft-versus-host disease (GvHD). Allogeneic NK cell therapies have reached the clinical stage as ex vivo expanded and differentiated non-engineered cells, as chimeric antigen receptor (CAR)-engineered or CD16-engineered products, or as combination therapies with antibodies, priming agents, and other drugs. This review summarizes the recent clinical status of allogeneic NK cell-based therapies for the treatment of hematological and solid tumors, discussing the main characteristics of the different cell sources used for NK product development, their use in cell manufacturing processes, the engineering methods and strategies adopted for genetically modified products, and the chosen approaches for combination therapies. A comparative analysis between NK-based non-engineered, engineered, and combination therapies is presented, examining the choices made by product developers regarding the NK cell source and the targeted tumor indications, for both solid and hematological cancers. Clinical trial outcomes are discussed and, when available, assessed in comparison with preclinical data. Regulatory challenges for product approval are reviewed, highlighting the lack of specificity of requirements and standardization between products. Additionally, the competitive landscape and business field is presented. This review offers a comprehensive overview of the effort driven by biotech and pharmaceutical companies and by academic centers to bring NK cell therapies to pivotal clinical trial stages and to market authorization.

Heparin and Heparin-Based Drug Delivery Systems: Pleiotropic Molecular Effects at Multiple Drug Resistance of Osteosarcoma and Immune Cells

One of the main problems of modern health care is the growing number of oncological diseases both in the elderly and young population. Inadequately effective chemotherapy, which remains the main method of cancer control, is largely associated with the emergence of multidrug resistance in tumor cells. The search for new solutions to overcome the resistance of malignant cells to pharmacological agents is being actively pursued. Another serious problem is immunosuppression caused both by the tumor cells themselves and by antitumor drugs. Of great interest in this context is heparin, a biomolecule belonging to the class of glycosaminoglycans and possessing a broad spectrum of biological activity, including immunomodulatory and antitumor properties. In the context of the rapid development of the new field of “osteoimmunology,” which focuses on the collaboration of bone and immune cells, heparin and delivery systems based on it may be of intriguing importance for the oncotherapy of malignant bone tumors. Osteosarcoma is a rare but highly aggressive, chemoresistant malignant tumor that affects young adults and is characterized by constant recurrence and metastasis. This review describes the direct and immune-mediated regulatory effects of heparin and drug delivery systems based on it on the molecular mechanisms of (multiple) drug resistance in (onco) pathological conditions of bone tissue, especially osteosarcoma.

Harnessing IL-15 signaling to potentiate NK cell-mediated cancer immunotherapy

Natural killer (NK) cells, a crucial component of the innate immune system, have long been of clinical interest for their antitumor properties. Almost every aspect of NK cell immunity is regulated by interleukin-15 (IL-15), a cytokine in the common γ-chain family. Several current clinical trials are using IL-15 or its analogs to treat various cancers. Moreover, NK cells are being genetically modified to produce membrane-bound or secretory IL-15. Here, we discuss the key role of IL-15 signaling in NK cell immunity and provide an up-to-date overview of IL-15 in NK cell therapy.

Therapeutic strategies for gastric cancer targeting immune cells: Future directions

Gastric cancer (GC) is a malignancy with a high incidence and mortality, and the emergence of immunotherapy has brought survival benefits to GC patients. Compared with traditional therapy, immunotherapy has the advantages of durable response, long-term survival benefits, and lower toxicity. Therefore, targeted immune cells are the most promising therapeutic strategy in the field of oncology. In this review, we introduce the role and significance of each immune cell in the tumor microenvironment of GC and summarize the current landscape of immunotherapy in GC, which includes immune checkpoint inhibitors, adoptive cell therapy (ACT), dendritic cell (DC) vaccines, reduction of M2 tumor-associated macrophages (M2 TAMs), N2 tumor-associated neutrophils (N2 TANs), myeloid-derived suppressor cells (MDSCs), effector regulatory T cells (eT_regs), and regulatory B cells (B_regs) in the tumor microenvironment and reprogram TAMs and TANs into tumor killer cells. The most widely used immunotherapy strategies are the immune checkpoint inhibitor programmed cell death 1/programmed death-ligand 1 (PD-1/PD-L1) antibody, cytotoxic T lymphocyte–associated protein 4 (CTLA-4) antibody, and chimeric antigen receptor T (CAR-T) in ACT, and these therapeutic strategies have significant anti-tumor efficacy in solid tumors and hematological tumors. Targeting other immune cells provides a new direction for the immunotherapy of GC despite the relatively weak clinical data, which have been confirmed to restore or enhance anti-tumor immune function in preclinical studies and some treatment strategies have entered the clinical trial stage, and it is expected that more and more effective immune cell–based therapeutic methods will be developed and applied.

Cytokine-Induced Memory-Like NK Cells: From the Basics to Clinical Applications

Natural killer (NK) cells are lymphocytes with a key role in the defense against viral infections and tumor cells. Although NK cells are classified as innate lymphoid cells (ILCs), under certain circumstances they exhibit adaptive and memory-like features. The latter may be achieved, among others, by a brief stimulation with interleukin (IL)-12, IL-15 and IL-18. These cytokine-induced memory-like (CIML) NK cells resemble the trained immunity observed in myeloid cells. CIML NK cells undergo transcriptional, epigenetic and metabolic reprogramming that, along with changes in the expression of cell surface receptors and components of cytotoxic granules, are responsible for their enhanced effector functions after a resting period. In addition, these memory-like NK cells persist for a long time, which make them a good candidate for cancer immunotherapy. Currently, several clinical trials are testing CIML NK cells infusions to treat tumors, mostly hematological malignancies. In relapse/refractory acute myeloid leukemia (AML), the adoptive transfer of CIML NK cells is safe and complete clinical remissions have been observed. In our review, we sought to summarize the current knowledge about the generation and molecular basis of NK cell memory-like responses and the up-to-date results from clinical trials with CIML NK cells.

Advances of research of Fc-fusion protein that activate NK cells for tumor immunotherapy

The rapid development of bioengineering technology has introduced Fc-fusion proteins, representing a novel kind of recombinant protein, as promising biopharmaceutical products in tumor therapy. Numerous related anti-tumor Fc-fusion proteins have been investigated and are in different stages of development. Fc-fusion proteins are constructed by fusing the Fc-region of the antibody with functional proteins or peptides. They retain the bioactivity of the latter and partial properties of the former. This structural and functional advantage makes Fc-fusion proteins an effective tool in tumor immunotherapy, especially for the recruitment and activation of natural killer (NK) cells, which play a critical role in tumor immunotherapy. Even though tumor cells have developed mechanisms to circumvent the cytotoxic effect of NK cells or induce defective NK cells, Fc-fusion proteins have been proven to effectively activate NK cells to kill tumor cells in different ways, such as antibody-dependent cell-mediated cytotoxicity (ADCC), activate NK cells in different ways in order to promote killing of tumor cells. In this review, we focus on NK cell-based immunity for cancers and current research progress of the Fc-fusion proteins for anti-tumor therapy by activating NK cells.

Immunotherapeutic HCW9218 augments anti-tumor activity of chemotherapy via NK cell-mediated reduction of therapy-induced senescent cells

Therapy induced senescence (TIS) in tumors and TIS cancer cells secrete proinflammatory senescence-associated secretory phenotype (SASP) factors. SASP factors promote TIS cancer cells to re-enter the growth cycle with stemness characteristics, resulting in chemo-resistance and disease relapse. Herein, we show that the immunotherapeutic HCW9218, comprising transforming growth factor-β (TGF-β) receptor II and interleukin (IL)-15/IL-15 receptor α domains, enhances metabolic and cytotoxic activities of immune cells and reduces TIS tumor cells in vivo to improve the efficacy of docetaxel and gemcitabine plus nab-paclitaxel against B16F10 melanoma and SW1990 pancreatic tumors, respectively. Mechanistically, HCW9218 treatment reduces the immunosuppressive tumor microenvironment and enhances immune cell infiltration and cytotoxicity in the tumors to eliminate TIS cancer cells. Immuno-depletion analysis suggests that HCW9218-activated natural killer cells play a pivotal role in TIS cancer cell removal. HCW9218 treatment following docetaxel chemotherapy further enhances efficacy of tumor antigen-specific and anti-programmed death-ligand 1 (PD-L1) antibodies in B16F10 tumor-bearing mice. We also show that HCW9218 treatment decreases TIS cells and lowers SASP factors in off-target tissues caused by chemotherapy of tumor-bearing mice. Collectively, HCW9218 has the potential to significantly enhance anti-tumor efficacy of chemotherapy, therapeutic antibodies, and checkpoint blockade by eliminating TIS cancer cells while reducing TIS-mediated proinflammatory side effects in normal tissues.

Natural Killer Cells: the Missing Link in Effective Treatment for High-Grade Serous Ovarian Carcinoma

OPINION STATEMENT

Ovarian cancer (OC), especially high-grade serous cancer (HGSC), is a highly heterogeneous malignancy with limited options for curative treatment and a high frequency of relapse. Interactions between OC and the immune system may permit immunoediting and immune escape, and current standard of care therapies can influence immune cell infiltration and function within the tumor microenvironment. Natural killer (NK) cells are involved in cancer immunosurveillance and immunoediting and can be activated by therapy, but deliberate approaches to maximize NK cell reactivity for treatment of HGSC are in their infancy. NK cells may be the ideal target for immunotherapy of HGSC. The diverse functions of NK cells, and their established roles in immunosurveillance, make them attractive candidates for more precise and effective HGSC treatment. NK cells' functional capabilities differ because of variation in receptor expression and genetics, with meaningful impacts on their anticancer activity. Studying HGSC:NK cell interactions will define the features that predict the best outcomes for patients with the disease, but the highly diverse nature of HGSC will likely require combination therapies or approaches to simultaneously target multiple, co-existing features of the tumor to avoid tumor escape and relapse. We expect that the ideal therapy will enable NK cell infiltration and activity, reverse immunosuppression within the tumor microenvironment, and enable effector functions against the diverse subpopulations that comprise HGSC.

Selinexor Enhances NK Cell Activation Against Malignant B Cells via Downregulation of HLA-E

Selinexor is an FDA approved selective inhibitor of the nuclear export protein exportin-1 (XPO1) and causes specific cancer cell death via nuclear accumulation of tumor suppressor proteins. Design of rational studies for the use of selinexor in combination with other therapeutic agents, such as immunotherapies, requires a fundamental understanding of the effects of selinexor on the immune system. One important emerging area of immunotherapy are natural killer (NK) cell based therapeutics. NK cell function is tightly regulated by a balance of signals derived from multiple activating and inhibitory receptors. Thus in cancer, up-regulation of stress ligands recognised by activating receptors or down-regulation of HLA class I recognised by inhibitory receptors can result in an anti-cancer NK cell response. Changes in XPO1 function therefore have the potential to affect NK cell function through shifting this balance. We therefore sought to investigate how selinexor may affect NK cell function. Selinexor pre-treatment of lymphoma cells significantly increased NK cell mediated cytotoxicity against SU-DHL-4, JeKo-1 and Ramos cells, concurrent with increased CD107a and IFNγ expression on NK cells. In addition, selinexor enhanced ADCC against lymphoma cells coated with the anti-CD20 antibodies rituximab and obinutuzumab. In probing the likely mechanism, we identified that XPO1 inhibition significantly reduced the surface expression of HLA-E on lymphoma cell lines and on primary chronic lymphocytic leukemia cells. HLA-E binds the inhibitory receptor NKG2A and in accordance with this, selinexor selectively increased activation of NKG2A+ NK cells. Our data reveals that selinexor, in addition to its direct cytotoxic activity, also activates an anti-cancer immune response via disruption of the inhibitory NKG2A:HLA-E axis.

Crosstalk between macrophages and natural killer cells in the tumor microenvironment

The tumor microenvironment (TME) is jointly constructed by a variety of cell types, including tumor cells, immune cells, fibroblasts, and epithelial cells, among others. The cells within the TME interact with each other and with tumor cells to influence tumor development and progression. As the most abundant immune cells in the TME, macrophages regulate the immune network by not only secreting a large amount of versatile cytokines but also expressing a series of ligands or receptors on the surface to interact with other cells directly. Due to their strong plasticity, they exert both immunostimulatory and immunosuppressive effects in the complex TME. The major effector cells of the immune system that directly target cancer cells include but are not limited to natural killer cells (NKs), dendritic cells (DCs), macrophages, polymorphonuclear leukocytes, mast cells, and cytotoxic T lymphocytes (CTLs). Among them, NK cells are the predominant innate lymphocyte subsets that mediate antitumor and antiviral responses. The activation and inhibition of NK cells are regulated by cytokines and the balance between activating and inhibitory receptors. There is an inextricable regulatory relationship between macrophages and NK cells. Herein, we systematically elaborate on the regulatory network between macrophages and NK cells through soluble mediator crosstalk and cell-to-cell interactions. We believe that a better understanding of the crosstalk between macrophages and NKs in the TME will benefit the development of novel macrophage- or NK cell-focused therapeutic strategies with superior efficacies in cancer therapy.

Bifunctional TGF-β trap/IL-15 Protein Complex Elicits Potent NK Cell and CD8+ T Cell Immunity Against Solid Tumors

Advances in immunostimulatory and anti-immunosuppressive therapeutics have revolutionized cancer treatment. However, novel immunotherapeutics with these dual functions are not frequently reported. Here we describe the creation of a heterodimeric bifunctional fusion molecule, HCW9218, constructed using our soluble tissue factor-based scaffold technology. This complex comprises extracellular domains of the human transforming growth factor-β (TGF-β) receptor II and a human interleukin (IL)-15/IL-15 receptor α complex. HCW9218 can be readily expressed in CHO cells and purified using antibody-based affinity chromatography in a large-scale manufacturing setting. HCW9218 potently activates mouse natural killer (NK) cells and CD8⁺ T cells in vitro and in vivo to enhance cell proliferation, metabolism and antitumor cytotoxic activities. Similarly, human immune cells become activated with increased cytotoxicity following incubation with HCW9218. This fusion complex also exhibits TGF-β neutralizing activity in vitro and sequesters plasma TGF-β in vivo. In a syngeneic B16F10 melanoma model, HCW9218 displayed strong antitumor activity mediated by NK cells and CD8⁺ T cells, and increased their infiltration into tumors. Repeat-dose subcutaneous administration of HCW9218 was well tolerated by mice, with a half-life sufficient to provide long lasting biological activity. Thus, HCW9218 may serve as a novel therapeutic to simultaneously provide immunostimulation and lessen immunosuppression associated with tumors.