Manufacturing Natural Killer Cells as Medicinal Products

Bulk RNA sequencing reveals the comprehensive genetic characteristics of human cord blood-derived natural killer cells

Introduction

Innate immune cells are important in tumor immunotherapy. Natural killer cells (NKCs) are also categorized as innate immune cells and can control tumor growth and metastatic spread. Glioblastoma (GBM) is the most common and aggressive primary brain tumor in adults. NKC-based immunotherapy is a promising treatment strategy against GBM. We previously reported a feeder-free expansion system that yielded large-scale highly purified and cytotoxic NKCs derived from human cord blood (CB). In the present study, we performed comprehensive genomic analyses of NKCs generated from human CB (CBNKCs) as compared those from human peripheral blood (PB) (PBNKCs).

Methods

Frozen T cell-free CB mononuclear cells were cultured with recombinant human interleukin (rhIL)-18 and rhIL-2 in anti-NKp46 and anti-CD16 antibody immobilization settings. After 14-day expansion, the total RNA of the CBNKCs or PBNKCs was extracted and transcriptomic analyses was performed to determine their similarities and differences. We also examined CBNKC and PBNKC activity against a GBM cell line.

Results

Differential expression gene analysis revealed that some NK activating and inhibitory receptors were significantly downregulated in the CBNKCs compared to PBNKCs. Furthermore, genes related to anti-apoptosis and proliferation were upregulated in the CBNKCs. Enrichment analysis determined that the gene sets related to immune response and cytokines were enriched in the CBNKCs. Gene set enrichment analysis demonstrated that the immune response pathway was upregulated in the CBNKCs. Cytotoxic assays using impedance-based cell analyzer revealed that the CBNKCs enhanced NKC-mediated cytotoxicity on GBM cells as compared to the PBNKCs.

Conclusions

We demonstrated the characteristics of human CBNKCs. Cell-based therapy using the CBNKCs is promising for treating GBM.

Successful targeting of PD-1/PD-L1 with chimeric antigen receptor-natural killer cells and nivolumab in a humanized mouse cancer model

In recent decades, chimeric antigen receptor (CAR)-engineered immune effector cells have demonstrated promising antileukemic activity. Nevertheless, their efficacy remains unsatisfactory on solid cancers, plausibly due to the influence of tumor microenvironments (TME). In a novel mouse cancer model with a humanized immune system, tumor-infiltrating immunosuppressive leukocytes and exhausted programmed death protein-1 (PD-1)^high T cells were found, which better mimic patient TME, allowing the screening and assessment of immune therapeutics. Particularly, membrane-bound programmed death ligand 1 (PD-L1) level was elevated on a tumor cell surface, which serves as an attractive target for natural killer (NK) cell-mediated therapy. Hematopoietic stem cell-derived CAR-NK (CAR pNK) cells targeting the PD-L1 showed enhanced in vitro and in vivo anti-solid tumor function. The CAR pNK cells and nivolumab resulted in a synergistic anti-solid tumor response. Together, our study highlights a robust platform to develop and evaluate the antitumor efficacy and safety of previously unexplored therapeutic regimens.

Preclinical and clinical studies of CAR-NK-cell therapies for malignancies

The development of chimeric antigen receptor T (CAR-T) cell therapy, a specific type of immunotherapy, in recent decades was a fantastic breakthrough for the treatment of hematological malignancies. However, difficulties in collecting normal T cells from patients and the time cost of manufacturing CAR-T cells have limited the application of CAR-T-cell therapy. In addition, the termination of related clinical trials on universal CAR-T cell therapy has made further research more difficult. Natural killer (NK) cells have drawn great attention in recent years. Chimeric antigen receptor-NK (CAR-NK) cell therapy is a promising strategy in the treatment of malignant tumors because of its lack of potential for causing graft-versus-host disease (GVHD). In this review, we will address the advances in and achievements of CAR-NK cell therapy.

Advances in NK cell production

Immunotherapy based on natural killer (NK) cells is a promising approach for treating a variety of cancers. Unlike T cells, NK cells recognize target cells via a major histocompatibility complex (MHC)-independent mechanism and, without being sensitized, kill the cells directly. Several strategies for obtaining large quantities of NK cells with high purity and high cytotoxicity have been developed. These strategies include the use of cytokine-antibody fusions, feeder cells or membrane particles to stimulate the proliferation of NK cells and enhance their cytotoxicity. Various materials, including peripheral blood mononuclear cells (PBMCs), umbilical cord blood (UCB), induced pluripotent stem cells (iPSCs) and NK cell lines, have been used as sources to generate NK cells for immunotherapy. Moreover, genetic modification technologies to improve the proliferation of NK cells have also been developed to enhance the functions of NK cells. Here, we summarize the recent advances in expansion strategies with or without genetic manipulation of NK cells derived from various cellular sources. We also discuss the closed, automated and GMP-controlled large-scale expansion systems used for NK cells and possible future NK cell-based immunotherapy products.

Identifying SARS-CoV-2 'memory' NK cells from COVID-19 convalescent donors for adoptive cell therapy

COVID-19 disease is the manifestation of syndrome coronavirus 2 (SARS-CoV-2) infection, which is causing a worldwide pandemic. This disease can lead to multiple and different symptoms, being lymphopenia associated with severity one of the most persistent. Natural killer cells (NK cells) are part of the innate immune system, being fighting against virus-infected cells one of their key roles. In this study, we determined the phenotype of NK cells after COVID-19 and the main characteristic of SARS-CoV-2-specific-like NK population in the blood of convalescent donors. CD57+ NKG2C+ phenotype in SARS-CoV-2 convalescent donors indicates the presence of 'memory'/activated NK cells as it has been shown for cytomegalovirus infections. Although the existence of this population is donor dependent, its expression may be crucial for the specific response against SARS-CoV-2, so that, it gives us a tool for selecting the best donors to produce off-the-shelf living drug for cell therapy to treat COVID-19 patients under the RELEASE clinical trial (NCT04578210).

The Dual Role of Innate Lymphoid and Natural Killer Cells in Cancer. from Phenotype to Single-Cell Transcriptomics, Functions and Clinical Uses

Simple Summary

Innate lymphoid cells (ILCs), a family of innate immune cells including natural killers (NKs), play a multitude of roles in first-line cancer control, in escape from immunity and in cancer progression. In this review, we summarize preclinical and clinical data on ILCs and NK cells concerning their phenotype, function and clinical applications in cellular therapy trials. We also describe how single-cell transcriptome sequencing has been used and forecast how it will be used to better understand ILC and NK involvement in cancer control and progression as well as their therapeutic potential.

Abstract

The role of innate lymphoid cells (ILCs), including natural killer (NK) cells, is pivotal in inflammatory modulation and cancer. Natural killer cell activity and count have been demonstrated to be regulated by the expression of activating and inhibitory receptors together with and as a consequence of different stimuli. The great majority of NK cell populations have an anti-tumor activity due to their cytotoxicity, and for this reason have been used for cellular therapies in cancer patients. On the other hand, the recently classified helper ILCs are fundamentally involved in inflammation and they can be either helpful or harmful in cancer development and progression. Tissue niche seems to play an important role in modulating ILC function and conversion, as observed at the transcriptional level. In the past, these cell populations have been classified by the presence of specific cellular receptor markers; more recently, due to the advent of single-cell RNA sequencing (scRNA-seq), it has been possible to also explore them at the transcriptomic level. In this article we review studies on ILC (and NK cell) classification, function and their involvement in cancer. We also summarize the potential application of NK cells in cancer therapy and give an overview of the most recent studies involving ILCs and NKs at scRNA-seq, focusing on cancer. Finally, we provide a resource for those who wish to start single-cell transcriptomic analysis on the context of these innate lymphoid cell populations.

Natural killer cell‑based immunotherapy for lung cancer: Challenges and perspectives (Review)

Despite the marked success of molecular targeted therapy in lung cancer in this era of personalized medicine, its efficacy has been limited by the presence of resistance mechanisms. The prognosis of patients with lung cancer remains poor, and there is an unmet need to develop more effective therapies to improve clinical outcomes. The increasing insight into the human immune system has led to breakthroughs in immunotherapy and has prompted research interest in employing immunotherapy to treat lung cancer. Natural killer (NK) cells, which serve as the first line of defense against tumors, can induce the innate and adaptive immune responses. Therefore, the use of NK cells for the development of novel lung-cancer immunotherapy strategies is promising. A growing number of novel approaches that boost NK cell antitumor immunity and expand NK cell populations ex vivo now provide a platform for the development of antitumor immunotherapy. The present review outlined the biology of NK cells, summarized the role of NK cells in lung cancer and the effect of the tumor microenvironment on NK cells, highlighted the potential of NK cell-based immunotherapy as an effective therapeutic strategy for lung cancer and discussed future directions.

Extracellular mRNA transported to the nucleus exerts translation-independent function

RNA in extracellular vesicles (EVs) are uptaken by cells, where they regulate fundamental cellular functions. EV-derived mRNA in recipient cells can be translated. However, it is still elusive whether “naked nonvesicular extracellular mRNA” (nex-mRNA) that are not packed in EVs can be uptaken by cells and, if so, whether they have any functions in recipient cells. Here, we show the entrance of nex-mRNA in the nucleus, where they exert a translation-independent function. Human nex-interleukin-1β (IL1β)-mRNA outside cells proved to be captured by RNA-binding zinc finger CCCH domain containing protein 12D (ZC3H12D)-expressing human natural killer (NK) cells. ZC3H12D recruited to the cell membrane binds to the 3′-untranslated region of nex-IL1β-mRNA and transports it to the nucleus. The nex-IL1β-mRNA in the NK cell nucleus upregulates antiapoptotic gene expression, migration activity, and interferon-γ production, leading to the killing of cancer cells and antimetastasis in mice. These results implicate the diverse actions of mRNA.

Nonvesicular extracellular RNA (nex-RNA) that are not packed in extracellular vesicles is detected outside the cell, but it is poorly understood. Here the authors report that nex-RNA is captured by a zinc finger protein and transported to the nucleus to enhance antimetastatic characters of the cell.

Chimeric antigen receptor (CAR) natural killer (NK)-cell therapy: leveraging the power of innate immunity

Chimeric antigen receptor (CAR) T cells are a rapidly emerging form of cancer treatment, and have resulted in remarkable responses in refractory lymphoid malignancies. However, their widespread clinical use is limited by toxicity related to cytokine release syndrome and neurotoxicity, the logistic complexity of their manufacturing, cost and time-to-treatment for autologous CAR-T cells, and the risk of graft-versus-host disease (GvHD) associated with allogeneic CAR-T cells. Natural killer (NK) cells have emerged as a promising source of cells for CAR-based therapies due to their ready availability and safety profile. NK cells are part of the innate immune system, providing the first line of defence against pathogens and cancer cells. They produce cytokines and mediate cytotoxicity without the need for prior sensitisation and have the ability to interact with, and activate other immune cells. NK cells for immunotherapy can be generated from multiple sources, such as expanded autologous or allogeneic peripheral blood, umbilical cord blood, haematopoietic stem cells, induced pluripotent stem cells, as well as cell lines. Genetic engineering of NK cells to express a CAR has shown impressive preclinical results and is currently being explored in multiple clinical trials. In the present review, we discuss both the preclinical and clinical trial progress made in the field of CAR NK-cell therapy, and the strategies to overcome the challenges encountered.

Generating natural killer cells for adoptive transfer: expanding horizons

Natural killer (NK) cells are unique innate lymphoid cells that have therapeutic potential in adoptive cell transfer-based cancer immunotherapy that has been established across a range of early-phase clinical trials. NK cells for use in adoptive transfer therapies are obtained from various sources, including primary NK cells from peripheral blood or apheresis products (autologous or allogeneic) and umbilical cord blood. NK cells have also been generated from CD34+ hematopoietic progenitors, induced pluripotent stem cells, embryonic stem cells and malignant cell lines. Apheresis-derived NK cell products are often administered after brief cytokine-based ex vivo activation, ideally aiming for in vivo expansion and proliferation. NK cells from other sources or from smaller volumes of blood require a longer period of expansion prior to therapeutic use. Although ex vivo NK cell expansion introduces a concern for senescence and exhaustion, there is also an opportunity to achieve higher NK cell doses, modulate NK cell activation characteristics and apply genetic engineering approaches, ultimately generating potent effector cells from small volumes of readily available starting materials. Herein the authors review the field of clinical-grade NK cell expansion, explore the desirable features of an idealized NK cell expansion approach and focus on techniques used in recently published clinical trials.

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

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

Cord-Blood Natural Killer Cell-Based Immunotherapy for Cancer

Natural killer (NK) cells are a predominant part of innate immune cells and play a crucial role in anti-cancer immunity. NK cells can kill target cells nonspecifically, and their recognition of target cells is not restricted by the major histocompatibility complex. NK cells also fight against tumor cells independently of antibodies and prior activation. Of note, umbilical cord blood (UCB) is a rich source of NK cells. Immunotherapies based on UCB-derived NK cells are becoming increasingly researched, and the investigations are producing encouraging results. In recent years, non-modified and modified UCB-derived NK cells have been successfully developed to fight against tumor cells. Herein, UCB-derived NK cell-based immunotherapy is a potential strategy for the treatment of cancer in the future. In this review, we focus on discussing the biological characteristics of UCB-derived NK cells and their application prospects in anti-tumor immunotherapy, including the latest preclinical and clinical researches.

The Antitumor Effect of Heparin is not Mediated by Direct NK Cell Activation

Natural killer (NK) cells are innate lymphocytes responsible for the elimination of infected or transformed cells. The activation or inhibition of NK cells is determined by the balance of target cell ligand recognition by stimulatory and inhibitory receptors on their surface. Previous reports have suggested that the glycosaminoglycan heparin is a ligand for the natural cytotoxicity receptors NKp30, NKp44 (human), and NKp46 (both human and mouse). However, the effects of heparin on NK cell homeostasis and function remain unclear. Here, we show that heparin does not enhance NK cell proliferation or killing through NK cell activation. Alternatively, in mice models, heparin promoted NK cell survival in vitro and controlled B16-F10 melanoma metastasis development in vivo. In human NK cells, heparin promisingly increased interferon (IFN)-γ production in synergy with IL-12, although the mechanism remains elusive. Our data showed that heparin is not able to increase NK cell cytotoxicity.

Validation of a flow cytometry-based method to quantify viable lymphocyte subtypes in fresh and cryopreserved hematopoietic cellular products

BACKGROUND AIMS

Adoptive cellular therapy with immune effector cells (IECs) has shown promising efficacy against some neoplastic diseases as well as potential in immune regulation. Both inherent variability in starting material and variations in cell composition produced by the manufacturing process must be thoroughly evaluated with a validated method established to quantify viable lymphocyte subtypes. Currently, commercialized immunophenotyping methods determine cell viability with significant errors in thawed products since they do not include any viability staining. We hereby report on the validation of a flow cytometry-based method for quantifying viable lymphocyte immunophenotypes in fresh and cryopreserved hematopoietic cellular products.

METHODS

Using fresh or frozen cellular products and stabilized blood, we report on the validation parameters accuracy, uncertainty, precision, sensitivity, robustness and contamination between samples for quantification of viable CD3+, CD4+ T cells, CD8+ T cells, CD3-CD56+CD16+/- NK cells, CD19+ B cells and CD14+ monocytes of relevance to fresh and cryopreserved hematopoietic cellular products using the Cytomics FC500 cytometer (Beckman Coulter).

RESULTS

The acceptance criteria set in the validation plan were all met. The method is able to accommodate the variability in absolute numbers of cells in starting materials collected or cryopreserved from patients or healthy donors (uncertainty of ≤20% at three different concentrations), stability over time (compliance over 3 years during regular inter-laboratory comparisons) and confidence in meaningful changes during cell processing and manufacturing (intra-assay and intermediate precision of 10% coefficient of variation). Furthermore, the method can accurately report on the efficacy of cell depletion since the lower limit of quantification was established (CD3+, CD4+ and CD8+ cells at 9, 8 and 8 cells/µL, respectively). The method complies with Foundation for the Accreditation of Cellular Therapy (FACT) standards for IEC, FACT-Joint Accreditation Committee of ISCT-EBMT (JACIE) hematopoietic cell therapy standards, International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use Q2(R1) and International Organization for Standardization 15189 standards. Furthermore, it complies with Ligand Binding Assay Bioanalytical Focus Group/American Association of Pharmaceutical Scientists, International Council for Standardization of Hematology/International Clinical Cytometry Society and European Bioanalysis Forum recommendations for validating such methods.

CONCLUSIONS

The implications of this effort include standardization of viable cell immunophenotyping of starting material for cell manufacturing, cell selection and in-process quality controls or dosing of IECs. This method also complies with all relevant standards, particularly FACT-JACIE standards, in terms of enumerating and reporting on the viability of the "clinically relevant cell populations."

Directed Differentiation of Mobilized Hematopoietic Stem and Progenitor Cells into Functional NK cells with Enhanced Antitumor Activity

Obtaining sufficient numbers of functional natural killer (NK) cells is crucial for the success of NK-cell-based adoptive immunotherapies. While expansion from peripheral blood (PB) is the current method of choice, ex vivo generation of NK cells from hematopoietic stem and progenitor cells (HSCs) may constitute an attractive alternative. Thereby, HSCs mobilized into peripheral blood (PB-CD34⁺) represent a valuable starting material, but the rather poor and donor-dependent differentiation of isolated PB-CD34⁺ cells into NK cells observed in earlier studies still represents a major hurdle. Here, we report a refined approach based on ex vivo culture of PB-CD34⁺ cells with optimized cytokine cocktails that reliably generates functionally mature NK cells, as assessed by analyzing NK-cell-associated surface markers and cytotoxicity. To further enhance NK cell expansion, we generated K562 feeder cells co-expressing 4-1BB ligand and membrane-anchored IL-15 and IL-21. Co-culture of PB-derived NK cells and NK cells that were ex-vivo-differentiated from HSCs with these feeder cells dramatically improved NK cell expansion, and fully compensated for donor-to-donor variability observed during only cytokine-based propagation. Our findings suggest mobilized PB-CD34⁺ cells expanded and differentiated according to this two-step protocol as a promising source for the generation of allogeneic NK cells for adoptive cancer immunotherapy.

Donor Lymphocyte-Derived Natural Killer Cells Control MHC Class I-Negative Melanoma

Natural killer (NK) cells provide a natural defense against MHC-I-negative tumors, such as melanoma. Donor lymphocyte infusion (DLI) containing NK cells, a form of adoptive immunotherapy used after allogenic bone marrow transplantation (allo-BMT), promotes antitumor immune responses but is often associated with life-threatening complications such as graft-versus-host disease (GvHD). Here, we showed that without prior allo-BMT, DLI provoked melanoma control associated with the infiltration and persistence of the transferred NK cells. This allograft acceptance did not correlate with an increase of GvHD; instead it correlated with the expansion and activation of tumor-infiltrating NK cells that expressed the cytotoxic molecules (e.g., IFNγ and granzyme B) and maturation signatures (e.g., CD11b^hiCD27^lo and KLRG^hi/CD43^hi). The development of beneficial tumor-infiltrating NK cells of DLI origin required host CD4⁺ T-cell help in part by producing IL2, as well as by limiting regulatory CD4⁺ T cells (Treg). IL2 blockade impaired the NK-dependent melanoma control, which could not be rescued by IL2 administration beyond CD4⁺ T-cell help. Our findings linked NK allograft acceptance-CD4⁺ T-cell help crosstalk to melanoma development without the need of allo-BMT. We thereby helped define that tumor-infiltrating NK cells of DLI origin may serve as effective therapeutic targets for controlling melanoma.

NK Cell-Based Immunotherapies in Cancer

With the development of technologies that can transform immune cells into therapeutic modalities, immunotherapy has remarkably changed the current paradigm of cancer treatment in recent years. NK cells are components of the innate immune system that act as key regulators and exhibit a potent tumor cytolytic function. Unlike T cells, NK cells exhibit tumor cytotoxicity by recognizing non-self, without deliberate immunization or activation. Currently, researchers have developed various approaches to improve the number and anti-tumor function of NK cells. These approaches include the use of cytokines and Abs to stimulate the efficacy of NK cell function, adoptive transfer of autologous or allogeneic ex vivo expanded NK cells, establishment of homogeneous NK cell lines using the NK cells of patients with cancer or healthy donors, derivation of NK cells from induced pluripotent stem cells (iPSCs), and modification of NK cells with cutting-edge genetic engineering technologies to generate chimeric Ag receptor (CAR)-NK cells. Such NK cell-based immunotherapies are currently reported as being promising anti-tumor strategies that have shown enhanced functional specificity in several clinical trials investigating malignant tumors. Here, we summarize the recent advances in NK cell-based cancer immunotherapies that have focused on providing improved function through the use of the latest genetic engineering technologies. We also discuss the different types of NK cells developed for cancer immunotherapy and present the clinical trials being conducted to test their safety and efficacy.

Non-Genetically Improving the Natural Cytotoxicity of Natural Killer (NK) Cells

The innate lymphocyte lineage natural killer (NK) is now the target of multiple clinical applications, although none has received an agreement from any regulatory agency yet. Transplant of naïve NK cells has not proven efficient enough in the vast majority of clinical trials. Hence, new protocols wish to improve their medical use by producing them from stem cells and/or modifying them by genetic engineering. These techniques have given interesting results but these improvements often hide that natural killers are mainly that: natural. We discuss here different ways to take advantage of NK physiology to improve their clinical activity without the need of additional modifications except for in vitro activation and expansion and allograft in patients. Some of these tactics include combination with monoclonal antibodies (mAb), drugs that change metabolism and engraftment of specific NK subsets with particular activity. Finally, we propose to use specific NK cell subsets found in certain patients that show increase activity against a specific disease, including the use of NK cells derived from patients.

Natural Killer Cell Expansion with Autologous Feeder Layer and Anti-CD3 Antibody for Immune Cell Therapy of Hepatocellular Carcinoma

Background:

one of the promising approaches for treatment of some cancers is adoptive cell therapy using natural killer (NK) cells. Various methods have been investigated for ex vivo expansion of NK cells in large-scale, but most of them involved cancer or genetically modified cells as feeder layer and also some of them have the risk of T cell contamination and graft-versus-host disease (GVHD).

Method:

In this study, irradiated autologous peripheral blood mononuclear cells (PBMCs) as feeder layer with an anti-CD3 monoclonal antibody (mAb) were used. For activation and expansion of NK cells, human recombinant IL2 and IL15 were used. After co-culturing of expanded NK cells (eNKC) and isolated NK cells (iNKC) with hepatocellular carcinoma (HCC) cells, the viability of eNKC in compared to iNKC were analyzed by CCK-8 assay and degranulation of NK cells after co-culturing was assayed by measuring CD107a expression. Enzyme-Linked Immunosorbent Assay (ELISA) assay was used for the ability of NK cells to secretion of IFN-γ (interferon-γ) and TNF-α (Tumor Necrosis Factor-α) after co-culture with HCC cells. Real Time PCR analysis was used for expression of human Perforin and Granzyme B genes in the NK cells exposed to target HepG2 cells.

Result:

This method strongly expanded highly purified NK cells with powerful cytotoxicity against HCC cells. The expanded NK cells showed high level of expression of degranulation marker and human Perforin and Granzyme B genes, and also was secreted larger amounts of TNF-α and IFN-γ compared with fresh isolated NK cells.

Conclusion:

we proposed an effective method for expansion of cytotoxic NK cells using irradiated autologous PBMC as feeder layer for more successful transfer of allogeneic NK cell in immuno cell therapy of HCC.

A simple method for in vitro preparation of natural killer cells from cord blood

Background

Cord Blood (CB) has been considered a promising source of natural killer (NK) cells for cellular immunotherapy. However, it is difficult to expand the large numbers of highly pure NK cells from CB without cell sorting and feeder cells/multiple cytokines. In this study, we try to develop a simple, safe and economical method for ex vivo expansion and purification of NK cells from CB without cell sorting and feeder cells/multiple cytokines.

Results

The large numbers (mean: 1.59 × 10¹⁰) of highly pure (≥90%) NK cells from CB could be obtained through interleukin-2, group A streptococcus and zoledronate stimulation of mononuclear cells using the 21-day culture approach. When compared to resting NK cells, expanded NK cells were a higher expression of activating receptors CD16, NKG2D, NKp30, NKp44, NKp46 and activating markers CD62L and CD69, while the inhibitory receptors, CD158a and CD158b remained largely unchanged. In addition, these cells showed a higher concentration of IFN-γ, TNF-α and GM-CSF secretion and cytotoxicity to K562 cells and acute myeloid leukemia targets than resting NK cells.

Conclusion

We develop a simple, safe and economical method to obtain high yield, purity, and functionality NK cells from CB without cell sorting and feeder cells/multiple cytokines.

Hepatic Natural Killer Cells: Organ-Specific Sentinels of Liver Immune Homeostasis and Physiopathology

The liver is considered a preferential tissue for NK cells residency. In humans, almost 50% of all intrahepatic lymphocytes are NK cells that are strongly imprinted in a liver-specific manner and show a broad spectrum of cellular heterogeneity. Hepatic NK (he-NK) cells play key roles in tuning liver immune response in both physiological and pathological conditions. Therefore, there is a pressing need to comprehensively characterize human he-NK cells to better understand the related mechanisms regulating their effector-functions within the dynamic balance between immune-tolerance and immune-surveillance. This is of particular relevance in the liver that is the only solid organ whose parenchyma is constantly challenged on daily basis by millions of foreign antigens drained from the gut. Therefore, the present review summarizes our current knowledge on he-NK cells in the light of the latest discoveries in the field of NK cell biology and clinical relevance.

Scaling up the Manufacturing Process of Adoptive T Cell Immunotherapy

Adoptive T cell immunotherapy, involving the reprogramming of immune cells to target specific cancer or virus-infected cells, has been recognized as a promising novel approach for the treatment of complex diseases. The impressive global momentum of this therapeutic approach has highlighted the urgent need for establishing it as an effective and standardized onco-therapeutic approach in a large manufacturing scale. However, given its heterogeneity and uncertainty in nature, adoptive T cell immunotherapy is associated with a high failure rate that restricts its manufacturing to a limited number of institutions worldwide. It is undoubted that quite a few major challenges must be met before engineered T cells can be considered as a reliable, safe, and effective remedy for a broad range of diseases with global-wise patient benefits. Here, the fundamental challenges that as yet remain unsolved in the manufacturing process before adoptive T cell therapy can be considered as a key element in the next generation of precision medicine is reviewed. It is proposed that it is necessary to adopt a closed system, automation, cost-effective manufacturing model, and quality-by-design (QbD) strategy to enable scaled up manufacturing of adoptive T cell immunotherapy; and it is challenging to choose appropriate bioreactors, parameters, and infrastructure in this process.

Challenges of NK cell-based immunotherapy in the new era

Natural killer cells (NKs) have a great potential for cancer immunotherapy because they can rapidly and directly kill transformed cells in the absence of antigen presensitization. Various cellular sources, including peripheral blood mononuclear cells (PBMCs), stem cells, and NK cell lines, have been used for producing NK cells. In particular, NK cells that expanded from allogeneic PBMCs exhibit better efficacy than those that did not. However, considering the safety, activities, and reliability of the cell products, researchers must develop an optimal protocol for producing NK cells from PBMCs in the manufacture setting and clinical therapeutic regimen. In this review, the challenges on NK cell-based therapeutic approaches and clinical outcomes are discussed.

In vitro-induced M2 type macrophages induces the resistance of prostate cancer cells to cytotoxic action of NK cells

Previous reports, including our experimental results, showed that macrophages migrate to prostate cancer (PCa) cells. We tested whether the migrated macrophages affect the susceptibility of castration-resistant PCa (CRPC) cells to cytotoxic actions of natural killer (NK) cells. We found treatment of tumor cells with the conditioned media (CM) of the PMA/IL-4 treated THP-1 cells (M2 type macrophages) (THP-1 CM) decreased the susceptibility of tumor cells to NK cell cytotoxicity, as a result of increased programmed death receptor ligand 1 (PD-L1) and decreased NK group 2D (NKG2D) ligands in CRPC cells. Meanwhile, the decreased susceptibility of tumor cells was also detected when NK cells were treated with THP-1 CM and used in NK cell cytotoxicity tests. Therefore, we observed higher resistance of CRPC cells when both tumor and NK cells were treated with THP-1 CM than when tumor cells or NK cells were individually treated. We further discovered that the PMA/IL-4 treated THP-1 cells secrete a high level of IL-6, so blocking the IL-6 action significantly decreased the PD-L1 level while recovering the NKG2D ligands, thus increasing the susceptibility of CRPC cells to NK cell action. Moreover, we discovered that JAK-Stat3 is the most critical IL-6 downstream signaling in triggering the THP-1 CM effect. Consequently, we found the susceptibility of CRPC cells to NK cells was increased when either JAK or Stat 3 inhibitor was added when tumor cells were treated with THP-1 CM, and that the best effect was observed when the JAK inhibitor and PD-L1 Ab were added together.

Anticancer cellular immunotherapies derived from umbilical cord blood

INTRODUCTION

The lack of highly effective drugs in many malignancies has prompted scientific interest in the development of alternative treatment strategies. Cellular immunotherapy involving the adoptive transfer of immune cells that potently recognize and eliminate malignantly transformed cells has become a promising new tool in the anticancer armory. Studies suggest that the unique biological properties of umbilical cord blood (UCB) cells could precipitate enhanced anticancer activity; hence, UCB could be an optimal source for immunotherapy with the potential to provide products with 'off-the-shelf' availability.

AREAS COVERED

In this review, the authors summarize data on the transfer of naturally occurring or genetically modified UCB cells to treat cancer. The focus within is on the phenotypic and functional differences compared to other sources, the alloreactive and anticancer properties, and manufacturing of these products. Therapies utilizing cytokine-induced killer (CIK) cells, natural killer (NK) cells and chimeric antigen receptor (CAR) T-cells, are discussed.

EXPERT OPINION

The cellular immunotherapy field has become a growing, exciting area that has generated much enthusiasm. There is evidence that anticancer immunotherapy with UCB-derived products is feasible and safe; however, considering the limited number of clinical trials using UCB-derived products, further studies are warranted to facilitate translation into clinical practice.

Influence of Irradiated Peripheral Blood Mononuclear Cells on Both Ex Vivo Proliferation of Human Natural Killer Cells and Change in Cellular Property

Clinical studies with adoptive immunotherapy using allogeneic natural killer (NK) cells showed feasibility, but also limitation regarding the transfused absolute cell numbers. First promising results with peripheral blood mononuclear cells (PBMCs) as feeder cells to improve the final cell number need further optimization and investigation of the unknown controlling mechanism in the cross-talk to NK cells. We investigated the influence of irradiated autologous PBMCs to boost NK cell proliferation in the presence of OKT3 and IL-2. Our findings demonstrate a requirement for receptor-ligand interactions between feeders and NK cells to produce soluble factors that can sustain NK cell proliferation. Thus, both physical contact between feeder and NK cells, and soluble factors produced in consequence, are required to fully enhance NK cell ex vivo proliferation. This occurred with an indispensable role of the cross-talk between T cells, monocytes, and NK cells, while B cells had no further influence in supporting NK cell proliferation under these co-culture conditions. Moreover, gene expression analysis of highly proliferating and non-proliferating NK cells revealed important phenotypic changes on 5-day cultured NK cells. Actively proliferating NK cells have reduced Siglec-7 and -9 expression compared with non-proliferating and resting NK cells (day 0), independently of the presence of feeder cells. Interestingly, proliferating NK cells cultured with feeder cells contained increased frequencies of cells expressing RANKL, B7-H3, and HLA class II molecules, particularly HLA-DR, compared with resting NK cells or expanded with IL-2 only. A subset of HLA-DR expressing NK cells, co-expressing RANKL, and B7-H3 corresponded to the most proliferative population under the established co-culture conditions. Our results highlight the importance of the crosstalk between T cells, monocytes, and NK cells in autologous feeder cell-based ex vivo NK cell expansion protocols, and reveal the appearance of a highly proliferative subpopulation of NK cells (HLA-DR⁺RANKL⁺B7-H3⁺) with promising characteristics to extend the therapeutic potential of NK cells.

Shaping of Natural Killer Cell Antitumor Activity by Ex Vivo Cultivation

Natural killer (NK) cells are a promising tool for the use in adoptive immunotherapy, since they efficiently recognize and kill tumor cells. In this context, ex vivo cultivation is an attractive option to increase NK cells in numbers and to improve their antitumor potential prior to clinical applications. Consequently, various strategies to generate NK cells for adoptive immunotherapy have been developed. Here, we give an overview of different NK cell cultivation approaches and their impact on shaping the NK cell antitumor activity. So far, the cytokines interleukin (IL)-2, IL-12, IL-15, IL-18, and IL-21 are used to culture and expand NK cells. The selection of the respective cytokine combination is an important factor that directly affects NK cell maturation, proliferation, survival, distribution of NK cell subpopulations, activation, and function in terms of cytokine production and cytotoxic potential. Importantly, cytokines can upregulate the expression of certain activating receptors on NK cells, thereby increasing their responsiveness against tumor cells that express the corresponding ligands. Apart from using cytokines, cocultivation with autologous accessory non-NK cells or addition of growth-inactivated feeder cells are approaches for NK cell cultivation with pronounced effects on NK cell activation and expansion. Furthermore, ex vivo cultivation was reported to prime NK cells for the killing of tumor cells that were previously resistant to NK cell attack. In general, NK cells become frequently dysfunctional in cancer patients, for instance, by downregulation of NK cell activating receptors, disabling them in their antitumor response. In such scenario, ex vivo cultivation can be helpful to arm NK cells with enhanced antitumor properties to overcome immunosuppression. In this review, we summarize the current knowledge on NK cell modulation by different ex vivo cultivation strategies focused on increasing NK cytotoxicity for clinical application in malignant diseases. Moreover, we critically discuss the technical and regulatory aspects and challenges underlying NK cell based therapeutic approaches in the clinics.