Natural Killer Target Cells Research Articles

Current progress in cancer immunotherapy based on natural killer cells.

One of the most common diseases in the present era is cancer. The common treatment methods used to control cancer include surgery, chemotherapy, and radiotherapy. Despite progress in the treatment of cancers, there still isno definite therapeutic approach. Among the currently proposed strategies, immunotherapy is a new approach that can provide better outcomes compared with existing therapies. Employing natural killer (NK) cells is one of the meansof immunotherapy. As innate lymphocytes, NKcells are capable of rapidly responding to cancer cells without being sensitized or restricted to the cognate antigen in advance, as compared to T cells that are tumor antigen-specific. Latest insights into thebiology of NK cells have clarified the underlying molecular mechanisms of NK cell maturation and differentiation, as well as controlling their effector functions through the investigation of the ligands and receptors engaged in recognizing cancer cells by NK cells. Elucidating the fact that NK cells recognize cancer cells could similarly show the mechanism through which cancer cells possibly avoid NK cell-dependent immune surveillance. Additionally, the expectations for novel immunotherapies by targeting NK cells have increased through the latest clinical outcomes of T-cell-targeted cancer immunotherapy. For this emerging method, researchers are still attempting to develop protocols for conferring the best proliferation and expansion medium, activation pathways, utilization dosage, transferring methods, as well as reducing possible side effects in cancer therapy. This study reviews the NK cells, their proliferation and expansion methods, and their recent applications in cancer immunotherapy.

NKG7 - regulating endosomal pathways?

Ng et al. have identified NKG7 as a regulator of inflammation in response to diverse immunological challenges. While NKG7 was required for the degranulation of cytotoxic cells, additional defects including reduced expansion and trafficking of CD8 T cells, and altered antigen presentation, were noted in NKG7-deficient mice. The precise mechanism by which NKG7 mediates its effects has not been resolved but may involve regulation of endosomal vesicle trafficking.

In vivo Anti-Cancer Effects of Resveratrol Mediated by NK Cell Activation

Natural killer (NK) cells are innate immune lymphocytes that play an important role in anti-viral and anti-tumour immune responses. Several cancer immunotherapy approaches targeting NK cells are currently in clinical or preclinical development. Here, we aimed to find food nutrients that activate NK cells and determine their usefulness as candidates for anti-cancer and anti-metastatic drugs. Resveratrol appeared to activate NK cells most effectively among the substances tested and synergistically increased IFN-γ secretion and NK cell cytotoxicity with interleukin-2 (IL-2). CD107a, NKp30, and NKG2D expression levels were upregulated on the surface of NK cells upon treatment with resveratrol in combination with IL-2 compared with treatment with IL-2 alone. Moreover, NK cell activity in human and mouse whole blood was enhanced upon treatment with resveratrol. Most importantly, administration of resveratrol effectively inhibited tumour growth and metastasis in mice. In conclusion, we suggest that resveratrol may represent a candidate anti-cancer drug that acts by activating NK cells in vivo.

The mechanisms of cellular crosstalk between mesenchymal stem cells and natural killer cells: Therapeutic implications.

Mesenchymal stem cells (MSCs) are mesenchymal precursors of various origins, with well-known immunomodulatory effects. Natural killer (NK) cells, the major cells of the innate immune system, are critical for the antitumor and antiviral defenses; however, in certain cases, they may be the main culprits in the pathogenesis of some NK-related conditions such as autoimmunities and hematological malignancies. On the other hand, these cells seem to be the major responders in beneficial phenomena like graft versus leukemia. Substantial data suggest that MSCs can variably affect NK cells and can be affected by these cells. Accordingly, acquiring a profound understanding of the crosstalk between MSCs and NK cells and the involved mechanisms seems to be a necessity to develop therapeutic approaches based on such interactions. Therefore, in this study, we made a thorough review of the existing literature on the interactions between MSCs and NK cells with a focus on the underlying mechanisms. The current knowledge herein suggests that MSCs possess a great potential to be used as tools for therapeutic targeting of NK cells in disease context and that preconditioning of MSCs, as well as their genetic manipulation before administration, may provide a wider variety of options in terms of eliciting more specific and desirable therapeutic outcomes. Nevertheless, our knowledge regarding the effects of MSCs on NK cells is still in its infancy, and further studies with well-defined conditions are warranted herein.

Skipped Over: Tuning Natural Killer Cells Toward HIV Through Alternative Splicing.

Natural killer (NK) cells provide some of the earliest immune responses to infection, but when viruses manipulate or perturb the immune environment to alter NK cell function, this places the host at a disadvantage. Indeed, others and we observe that in the context of HIV/simian immunodeficiency virus (SIV) infection, although NK cells are not infected, they can become dysfunctional over time. Several studies have characterized protein and transcriptional profiles of NK cells during HIV/SIV infection, but none have examined whether the production of alternative transcripts and corresponding isoforms is modulated. This phenomenon occurs broadly in normal biology and in other disease states, and could provide a novel avenue of investigation that may yield better targets to restore or augment NK cell responses to HIV/SIV. Herein, we briefly summarize published and new data that may provide a perspective on how to target NK cell splice variants.

Abstract LB-076: Targeted Natural Killer (NK) cell based adoptive immunotherapy for the treatment of patients with non-small cell lung cancer (NSCLC) after radiochemotherapy - results of a randomized phase II clinical trial (NSCLC-TKD/IL-2) (Eudra-CT Number 2008-002130-30)

Abstract Membrane-bound heat shock protein 70 (mHsp70) is indicative for high-risk tumors with negative prognosis but also serves as a target for NK cells that are stimulated with Hsp70 peptide TKD and low dose IL-2 (TKD/IL-2). Herein, the efficacy of ex vivo TKD/IL-2 activated, autologous NK cells was tested in a randomized, investigator initiated phase II clinical trial in patients with mHsp70 positive advanced stage NSCLC after radiochemotherapy (RCT, 60-70 Gy, platinum-based chemotherapy). The interventional (INT) group received 4 cycles TKD/IL-2 activated, autologous NK cells every 2-6 weeks subsequent to standard RCT and the control (CTRL) group received best supportive care. The primary objective of the study was to examine whether the adjuvant treatment of NSCLC patients with TKD/IL-2 activated NK cells is feasible and effective with respect to progression-free survival (PFS). Secondary objectives were the assessment of treatment and biological responses, toxicity, quality-of-life (QoL, QLQ-LC13). Eight patients were randomized into the INT and eight into the CTRL arm. None of the patients died between randomization and final tumor assessment 18 months after randomization. In the INT group one patient had complete response (CR), one patient partial response (PR), two patients stable disease (SD) and one patient progressive disease (PD) at the last documented visit, whereas in the CTRL group only 2 patients showed clinical responses (PR, SD) and five patients had PD. The clinical response of patients in the INT group appeared to be mediated by activated NK cells whereas in the CTRL group by CD8+ T cells. The NK cell therapy after RCT was well tolerated, no differences in QoL were observed between both study groups. Citation Format: Gabriele Multhoff, Stephanie E. Combs, Sophie Seier, Stefan Stangl, Wolfgang Sievert, Maxim Shevtsov, Christiane Blankenstein, Martin Hildebrandt, Konrad Kokowski, Matthias Hautmann, Hubert Hautmann, Claus Roedel, Rainer Fietkau, Rudolf M. Huber, Bernhard Haller, Christina Ertl, Michal Devecka, Robert Offner, Norbert Ahrens. Targeted Natural Killer (NK) cell based adoptive immunotherapy for the treatment of patients with non-small cell lung cancer (NSCLC) after radiochemotherapy - results of a randomized phase II clinical trial (NSCLC-TKD/IL-2) (Eudra-CT Number 2008-002130-30) [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr LB-076.

Abstract 1723: Trispecific natural killer cell nanoengagers for targeted chemoimmunotherapy

Abstract Background: Activation of the innate immune system and natural killer (NK) cells has been a key effort in cancer immunotherapy research. Several NK-cell-targeted therapeutics are under clinical investigation. Current research is focused on bispecific antibodies that can bind to and target both tumor cells and NK cells. However, NK activation remains a key challenge. One approach is to simultaneously co-activate more than one NK cell stimulatory molecule, such as 4-1BB and CD16 (FcγRIII), to increase immune activation. To achieve this, we developed a new nanoparticle (NP)-based trispecific NK cell engager (nano-TriNKE) platform that can target epidermal growth factor receptor (EGFR) overexpressing tumors and promote the recruitment and activation of NK cells to eradicate these cancer cells. Moreover, the nanoengager platform allows the targeted delivery of chemotherapeutics such as epirubicin (EPI) to further improve the therapeutic efficacy. Methods: EGFR-targeted drug-free/EPI-encapsulated nano-TriNKEs were prepared by conjugating cetuximab (anti-EGFR), anti-4-BB, and anti-CD16 agonistic antibodies to PEG-PLGA NPs. Their binding specificities were evaluated in expanded murine NK cells, EGFR-overexpressed A431 (epidermoid carcinoma), MB468 (mammary gland adenocarcinoma), and HT29 (colorectal adenocarcinoma) cells in vitro. The in vitro NK cell anticancer activities in nano-TriNKE-pretreated A431, MB468, and HT29 cells were evaluated via viability assays. We also performed comprehensive in vivo efficacy studies in A431, MB468, and HT29 tumor model to investigate the anticancer activities of EGFR-targeted drug-free/EPI-encapsulated nano-TriNKEs. Further biodistribution and mechanistic studies were performed to verify the anticancer activities of nano-TriNKEs. Results: In vitro binding assay confirmed that the EGFR-targeted nano-TriNKEs bind selectively to EGFR-overexpressed cancer cells. In vitro anticancer activity studies demonstrated that effective NK cell activation can be achieved by spatiotemporal co-activation of CD16 and 4-1BB stimulatory molecules on NK cells with nanoengagers, and that the nanoengagers are more effective than free antibodies. Comprehensive in vivo efficacy studies in A431, MB468, and HT29 tumor models demonstrated that the EGFR-targeted nano-TriNKEs can augment both NK activating agents and chemotherapy as highly effective anticancer agents, providing robust chemoimmunotherapy against a broad range of EGFR-overexpressed cancers. Conclusions: Our data demonstrated that nano-TriNKEs are more effective in NK activation than free agonistic antibodies, and that the nanoengager platform provides more effective biological targeting, which is critical in NK-mediated cancer immunotherapy. Citation Format: Kin Man Au, Steven Park, Andrew Wang. Trispecific natural killer cell nanoengagers for targeted chemoimmunotherapy [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 1723.

NK Cell Development in Times of Innate Lymphoid Cell Diversity

After being described in the 1970s as cytotoxic cells that do not require MHC-dependent pre-activation, natural killer (NK) cells remained the sole member of innate lymphocytes for decades until lymphoid tissue-inducer cells in the 1990s and helper-like innate lymphoid lineages from 2008 onward completed the picture of innate lymphoid cell (ILC) diversity. Since some of the ILC members, such as ILC1s and CCR6− ILC3s, share specific markers previously used to identify NK cells, these findings provoked the question of how to delineate the development of NK cell and helper-like ILCs and how to properly identify and genetically interfere with NK cells. The description of eomesodermin (EOMES) as a lineage-specifying transcription factor of NK cells provided a candidate that may serve as a selective marker for the genetic targeting and identification of NK cells. Unlike helper-like ILCs, NK cell activation is, to a large degree, regulated by the engagement of activating and inhibitory surface receptors. NK cell research has revealed some elegant mechanisms of immunosurveillance, coined “missing-self” and “induced-self” recognition, thus complementing “non-self recognition”, which is predominantly utilized by adaptive lymphocytes and myeloid cells. Notably, the balance of activating and inhibitory signals perceived by surface receptors can be therapeutically harnessed for anti-tumor immunity mediated by NK cells. This review aims to summarize the similarities and the differences in development, function, localization, and phenotype of NK cells and helper-like ILCs, with the purpose to highlight the unique feature of NK cell development and regulation.

The cancer-natural killer cell immunity cycle.

Immunotherapy with checkpoint blockade induces rapid and durable immune control of cancer in some patients and has driven a monumental shift in cancer treatment. Neoantigen-specific CD8+ T cells are at the forefront of current immunotherapy strategies, and the majority of drug discovery and clinical trials revolve around further harnessing these immune effectors. Yet the immune system contains a diverse range of antitumour effector cells, and these must function in a coordinated and synergistic manner to overcome the immune-evasion mechanisms used by tumours and achieve complete control with tumour eradication. A key antitumour effector is the natural killer (NK) cells, cytotoxic innate lymphocytes present at high frequency in the circulatory system and identified by their exquisite ability to spontaneously detect and lyse transformed or stressed cells. Emerging data show a role for intratumoural NK cells in driving immunotherapy response and, accordingly, there have been renewed efforts to further elucidate and target the pathways controlling NK cell antitumour function. In this Review, we discuss recent clinical evidence that NK cells are a key immune constituent in the protective antitumour immune response and highlight the major stages of the cancer-NK cell immunity cycle. We also perform a new analysis of publicly available transcriptomic data to provide an overview of the prognostic value of NK cell gene expression in 25 tumour types. Furthermore, we discuss how the role of NK cells evolves with tumour progression, presenting new opportunities to target NK cell function to enhance cancer immunotherapy response rates across a more diverse range of cancers.

Targeting NK Cell Checkpoint Receptors or Molecules for Cancer Immunotherapy.

Checkpoint blockade therapy, for example using antibodies against CTLA-4 and PD-1/PD-L1, relieves T cells from the suppression by inhibitory checkpoints in the tumor microenvironment; thereby achieving good outcomes in the treatment of different cancer types. Like T cells, natural killer (NK) cell inhibitory receptors function as checkpoints for NK cell activation. Upon interaction with their cognate ligands on infected cells, tumor cells, dendritic cells and regulatory T cells, signals from these receptors severely affect NK cells' activation and effector functions, resulting in NK cell exhaustion. Checkpoint inhibition with antagonistic antibodies (Abs) can rescue NK cell exhaustion and arouse their robust anti-tumor capacity. Most notably, the response to anti-PD-1 therapy can be enhanced by the increased frequency and activation of NK cells, thereby increasing the overall survival of patients with multiple types of cancer. In addition, rescue of NK cell activity could enhance adaptive T cells' anti-tumor activity. Some antagonistic Abs (e.g., anti-TIGIT and anti-NKG2A monoclonal Abs) have extraordinary potential in cancer therapy, as evidenced by their induction of potent anti-tumor immunity through recovering both NK and T cell function. In this review, we summarize the dysfunction of NK cells in the tumor microenvironment and the key NK cell checkpoint receptors or molecules that control NK cell function. We particularly focus on recent advances in the most promising strategies through blockade of NK cell checkpoints or their combination with other approaches to more effectively reject tumors.

Functional and metabolic targeting of natural killer cells to solid tumors.

The unique ability of NK cells to target cancer cells without antigen specificity makes them an attractive prospect for immunotherapy of solid tumors. However, the complexity of the tumor microenvironment (TME), particularly its heterogeneity and associated immunosuppressive properties, enables solid tumor cells to escape NK cell immune-surveillance by impairing their infiltration and cytotoxic functions. As a result, NK cells that have been able to infiltrate solid tumors are dysfunctional, exhausted and metabolically and functionally impaired. Understanding the status of NK cells in solid tumors and the interplay between the tumor-promoting functions of the TME and the immunometabolic reprogramming events that NK cells endure as a result is essential to developing approaches to improve the clinical outcome of NK cell-based immunotherapies against solid tumors. In this review, we address the current knowledge on the presence and immunometabolic roles of NK cells in solid tumors as well as the strategies developed to restore NK cell activities in these conditions, with the ultimate goal of enhancing persistence, trafficking, cytotoxicity and metabolic functions.

Targeting Natural Killer Cells for Improved Immunity and Control of the Adaptive Immune Response.

Natural killer (NK) cells are critical for targeting and killing tumor, virus-infected and stressed cells as a member of the innate immune system. Recently, NK cells have also emerged as key regulators of adaptive immunity and have become a prominent therapeutic target for cancer immunotherapy and infection control. NK cells display a diverse array of phenotypes and function. Determining how NK cells develop and are regulated is critical for understanding their role in both innate and adaptive immunity. In this review we discuss current research approaches into NK cell adaptive immunity and how these cells are being harnessed for improving cancer and vaccination outcomes.

Pharmacological targeting of natural killer cells for cancer immunotherapy.

Natural killer (NK) cells are innate lymphocytes that rapidly respond to cancer cells without prior sensitization or restriction to the cognate antigen in comparison with tumor antigen‐specific T cells. Recent advances in understanding NK‐cell biology have elucidated the molecular mechanisms underlying the differentiation and maturation of NK cells, in addition to the control of their effector functions by investigating the receptors and ligands involved in the recognition of cancer cells by NK cells. Such clarification of NK‐cell recognition of cancer cells also revealed the mechanism by which cancer cells potentially evade NK–cell‐dependent immune surveillance. Furthermore, the recent clinical results of T–cell‐targeted cancer immunotherapy have increased the expectations for new immunotherapies by targeting NK cells. However, the potential use of NK cells in cancer immunotherapy is not fully understood. In this review, we discuss the current evidence and future potential of pharmacological targeting of NK cells in cancer immunotherapy.

Role of the KLRG1 pathway during the immune response to cancer

Abstract Immunotherapy drugs targeting T cells have been successfully developed for a variety of different cancers. In contrast, comparably less work has been done on targeting natural killer (NK) cells for immunotherapy. NK cells are intriguing targets for a number of different reasons, including their cytotoxic abilities and relatively lower autoimmunity risks. Thus, treatments that target NK cells, either alone or in conjunction with T cells, should be explored for the development of new treatments. One of the most well-known immunotherapy targets, programmed death-1 (PD-1) has recently been implicated in modulating NK cell function in cancer and demonstrates that targeting NK cells is an important aspect of cancer treatment. In addition to PD-1, there are many checkpoint molecules that may be capable of impacting NK cell function. One such target is KLRG1, a well conserved C-type lectin inhibitory receptor expressed on NK cells, which contains an ITIM in its cytoplasmic domain. To determine the role of KLRG1, and expand on the role of PD-1, as potential NK cell checkpoints, we developed a series of mice deficient for KLRG1 and PD-1, and took advantage of the NK sensitive cancer model B16. Following administration of B16-E-cadherin, we found that KLRG1 deficient animals had significantly fewer tumors in the lung tissue, compared to wild type controls. In addition, B16-E-cadherin resulted in a higher number of tumors in wild-type mice, compared to the parental B16 cell line. Altogether, these data suggest that KLRG1 is a checkpoint target candidate.

Enhancing natural killer cell function with gp41-targeting bispecific antibodies to combat HIV infection.

The aim of this study was to develop and evaluate the activity of bispecific antibodies (bsAbs) to enhance natural killer (NK) cell antibody-dependent cellular cytotoxicity (ADCC) against HIV-infected cells. These bsAbs are based on patient-derived antibodies targeting the conserved gp41 stump of HIV Env, and also incorporate a high-affinity single chain variable fragment (scFv) targeting the activating receptor CD16 on NK cells. Overall, we expect the bsAbs to provide increased affinity and avidity over their corresponding mAbs, allowing for improved ADCC activity against Env-expressing target cells. bsAbs and their corresponding mAbs were expressed in 293T cells and purified. The binding of bsAbs and mAbs to their intended targets was determined using Bio-Layer Interferometry, as well as flow cytometry based binding assays on in-vitro infected cells. The ability of these bsAbs to improve NK cell activity against HIV-infected cells was tested using in-vitro co-culture assays, using flow cytometry and calcein release to analyse NK cell degranulation and target cell killing, respectively. The bsAbs-bound gp41 with similar affinity to their corresponding mAbs had increased affinity for CD16. The bsAbs also bound to primary CD4 T cells infected in vitro with two different strains of HIV. In addition, the bsAbs induce increased NK cell degranulation and killing of autologous HIV-infected CD4 T cells. On the basis of their in-vitro killing efficacy, bsAbs may provide a promising strategy to improve NK-mediated immune targeting of infected cells during HIV infection.

Natural Killer Cell Responses in Hepatocellular Carcinoma: Implications for Novel Immunotherapeutic Approaches.

Hepatocellular carcinoma (HCC) still represents a significant complication of chronic liver disease, particularly when cirrhosis ensues. Current treatment options include surgery, loco-regional procedures and chemotherapy, according to specific clinical practice guidelines. Immunotherapy with check-point inhibitors, aimed at rescuing T-cells from exhaustion, has been applied as second-line therapy with limited and variable success. Natural killer (NK) cells are an essential component of innate immunity against cancer and changes in phenotype and function have been described in patients with HCC, who also show perturbations of NK activating receptor/ligand axes. Here we discuss the current status of NK cell treatment of HCC on the basis of existing evidence and ongoing clinical trials on adoptive transfer of autologous or allogeneic NK cells ex vivo or after activation with cytokines such as IL-15 and use of antibodies to target cell-expressed molecules to promote antibody-dependent cellular cytotoxicity (ADCC). To this end, bi-, tri- and tetra-specific killer cell engagers are being devised to improve NK cell recognition of tumor cells, circumventing tumor immune escape and efficiently targeting NK cells to tumors. Moreover, the exciting technique of chimeric antigen receptor (CAR)-engineered NK cells offers unique opportunities to create CAR-NK with multiple specificities along the experience gained with CAR-T cells with potentially less adverse effects.

Time- and Dose-Dependent Effects of Ionizing Irradiation on the Membrane Expression of Hsp70 on Glioma Cells.

The major stress-inducible protein Hsp70 (HSPA1A) is overexpressed in the cytosol of many highly aggressive tumor cells including glioblastoma multiforme and presented on their plasma membrane. Depending on its intracellular or membrane localization, Hsp70 either promotes tumor growth or serves as a target for natural killer (NK) cells. The kinetics of the membrane Hsp70 (mHsp70) density on human glioma cells (U87) was studied after different irradiation doses to define the optimal therapeutic window for Hsp70-targeting NK cells. To maintain the cells in the exponential growth phase during a cultivation period of 7 days, different initial cell counts were seeded. Although cytosolic Hsp70 levels remained unchanged on days 4 and 7 after a sublethal irradiation with 2, 4 and 6 Gy, a dose of 2 Gy resulted in an upregulated mHsp70 density in U87 cells which peaked on day 4 and started to decline on day 7. Higher radiation doses (4 Gy, 6 Gy) resulted in an earlier and more rapid onset of the mHsp70 expression on days 2 and 1, respectively, followed by a decline on day 5. Membrane Hsp70 levels were higher on cells in G2/M than in G1; however, an irradiation-induced cell cycle arrest on days 4 and 7 was not associated with an increase in the mHsp70 density. Extracellular Hsp70 concentrations in the supernatant of irradiated cells were significantly higher than sham (0 Gy) irradiated cells on days 4 and 7, but not on day 1. Functionally, elevated mHsp70 densities were associated with a significantly better lysis by Hsp70-targeting NK cells. In summary, the kinetics of changes in the mHsp70 density upon irradiation on tumor cells is time- and dose-dependent.

Mechanisms of Resistance to NK Cell Immunotherapy.

Immunotherapy has recently been a major breakthrough in cancer treatment. Natural killer (NK) cells are suitable targets for immunotherapy owing to their potent cytotoxic activity that may target cancer cells in a major histocompatibility complex (MHC) and antigen-unrestricted manner. Current therapies targeting NK cells include monoclonal antibodies that promote NK cell antibody-dependent cell-mediated cytotoxicity (ADCC), hematopoietic stem cell transplantation (HSCT), the adoptive transfer of NK cells, the redirection of NK cells using chimeric antigen receptor (CAR)-NK cells and the use of cytokines and immunostimulatory drugs to boost the anti-tumor activity of NK cells. Despite some encouraging clinical results, patients receiving these therapies frequently develop resistance, and a myriad of mechanisms of resistance affecting both the immune system and cancer cells have been reported. A first contributing factor that modulates the efficacy of the NK cell therapy is the genetic profile of the individual, which regulates all aspects of NK cell biology. Additionally, the resistance of cancer cells to apoptosis and the immunoediting of cancer cells, a process that decreases their immunogenicity and promotes immunosuppression, are major determinants of the resistance to NK cell therapy. Consequently, the efficacy of NK cell anti-tumor therapy is specific to each patient and disease. The elucidation of such immunosubversive mechanisms is crucial to developing new procedures and therapeutic strategies to fully harness the anti-tumor potential of NK cells.

Abstract A21: Engineering antigen-specific natural killer cells against the melanoma-associated antigen tyrosinase via TCR gene transfer

Abstract Introduction of chimeric antigen receptors (CARs) to natural killer (NK) cells has so far been the only practical method for specific targeting of NK cells against surface antigens. In contrast, T-cell receptor (TCR) gene therapy can supply large populations of cytotoxic T-lymphocytes (CTL) genetically modified to express a TCR that can also target intracellular antigens. However, the mispairing of endogenous and genetically transferred TCR subunits constitutes a bottleneck in the development of safe therapies as it often leads to formation of TCRs with unknown specificity. In order to overcome this obstacle and enable intracellular antigen targeting, we propose the use of NK cells for TCR gene therapy. In this study, we approach the obstacles associated with TCR gene therapy from a unique perspective that results in MHC-I-restricted epitope-specific targeting of tumors cells through expression of a functional TCR complex on NK cells. Our results show that the ectopic expression of CD3δ, CD3γ, and CD3ϵ chains along with TCR α/β gene delivery to NK cells enables the functional expression of a TCR specific to the HLA-A2-restiricted tyrosinase-derived melanoma epitope, Tyr368-379. NK cells expressing a functional TCR exhibit the capacity to degranulate in an antigen-specific manner in response to engagement of the cognate peptide/MHC ligand on target cells. In addition, upon engagement of their TCR, NK cells are fully capable of producing proinflammatory cytokines IFNγ and TNF-α, a signature mark of NK cell activation and immune cell recruitment. Finally, NK-TCR cells exhibit MHC-I-restricted antigen detection and antigen-specific lysis of tumor cells both in vitro and in vivo. Antigen-specific targeting of NK cells via TCR gene delivery stands out as a unique discovery providing a novel tool in the field of adoptive immunotherapy that can also overcome the major hurdle of “mispairing” in TCR gene therapy. Clinical trials using NK cells, including genetically modified NK cells expressing activating receptors or CARs, have clearly demonstrated a significant benefit in patients with various malignancies. The overall safety profile and promising clinical benefits of NK cells combined with the exclusive antigen specificity of the TCR, all together provide a novel approach in the design of efficient antigen-specific adoptive immunotherapy. Citation Format: Ayhan Parlar, Ece C. Sayitoglu, Cevriye Pamukcu, Anna-Maria Georgoudaki, Didem Ozkazanc, Mertkaya Aras, Benjamin Josey, Michael Chrobok, Suzanne Branecki, Pegah Zahedimaram, Lolai Ikromzoda, Evren Alici, Batu Erman, Tolga Sutlu, Adil D. Duru. Engineering antigen-specific natural killer cells against the melanoma-associated antigen tyrosinase via TCR gene transfer [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2018 Nov 27-30; Miami Beach, FL. Philadelphia (PA): AACR; Cancer Immunol Res 2020;8(4 Suppl):Abstract nr A21.

Targeting Natural Killer Cells for Tumor Immunotherapy.

Natural killer (NK) cells are important innate cytotoxic lymphocytes with a rapid and efficient capacity to recognize and kill tumor cells. In recent years, adoptive transfer of autologous- or allogeneic-activated NK cells has become a promising cellular therapy for cancer. However, the therapeutic efficiency is encouraging in hematopoietic malignancies, but disappointing in solid tumors, for which the use of NK-cell-based therapies presents considerable challenges. It is difficult for NK cells to traffic to, and infiltrate into, tumor sites. NK cell function, phenotype, activation, and persistence are impaired by the tumor microenvironment, even leading to NK cell dysfunction or exhaustion. Many strategies focusing on improving NK cells' durable persistence, activation, and cytolytic activity, including activation with cytokines or analogs, have been attempted. Modifying them with chimeric antigen receptors further increases the targeting specificity of NK cells. Checkpoint blockades can relieve the exhausted state of NK cells. In this review, we discuss how the cytolytic and effector functions of NK cells are affected by the tumor microenvironment and summarize the various immunotherapeutic strategies based on NK cells. In particular, we discuss recent advances in overcoming the suppressive effect of the tumor microenvironment with the aim of enhancing the clinical outcome in solid tumors treated with NK-cell-based immunotherapy.