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

Natural killer cell-related anti-tumour adoptive cell immunotherapy

Chimeric antigen receptor- (CAR-)modified T cells have been successfully used to treat blood cancer. With the improved research on anti-tumour adoptive cell therapy, researchers have focused on immune cells other than T lymphocytes. Natural killer (NK) cells have received widespread attention as barriers to natural immunity. Compared to T lymphocyte-related adoptive cell therapy, the use of NK cells to treat tumours does not cause graft-versus-host disease, significantly improving immunity. Moreover, NK cells have more sources than T cells, and the related modified cells are less expensive. NK cells function through several pathways in anti-tumour mechanisms. Currently, many anti-tumour clinical trials have used NK cell-related adoptive cell therapies. In this review, we have summarized the recent progress in NK cell-related adoptive cellular immunotherapy for tumour treatment and propose the current challenges faced by CAR-NK cell therapy.

An efficient feeder-free and chemically-defined expansion strategy for highly purified natural killer cells derived from human cord blood

Introduction

Natural killer cells (NKCs) are immune cells that can attack cancer cells through the direct recognition of ligands without prior sensitization. Cord blood-derived NKCs (CBNKCs) represent a promising tool for allogenic NKC-based cancer immunotherapy. Efficient NKC expansion and decreased T cell inclusion are crucial for the success of allogeneic NKC-based immunotherapy without inducing graft-versus-host reactions. We previously established an efficient ex vivo expansion system consisting of highly purified-NKCs derived from human peripheral blood. Herein, we evaluated the performance of the NKC expansion system using CB and characterized the expanded populations.

Methods

Frozen CB mononuclear cells (CBMCs), with T cells removed, were cultured with recombinant human interleukin (rhIL)-18 and rhIL-2 under conditions where anti-NKp46 and anti-CD16 antibodies were immobilized. Following 7, 14, and 21 days of expansion, the purity, fold-expansion rates of NKCs, and the expression levels of NK activating and inhibitory receptors were assessed. The ability of these NKCs to inhibit the growth of T98G, a glioblastoma (GBM) cell line sensitive to NK activity, was also examined.

Results

All expanded T cell-depleted CBMCs were included in over 80%, 98%, and 99% of CD3^-CD56⁺ NKCs at 7, 14, and 21 days of expansion, respectively. The NK activating receptors LFA-1, NKG2D, DNAM-1, NKp30, NKp44, NKp46, FcγRIII and NK inhibitory receptors TIM-3, TIGIT, TACTILE, NKG2A were expressed on the expanded-CBNKCs. Two out of three of the expanded-CBNKCs weakly expressed PD-1, yet gradually expressed PD-1 according to expansion period. One of the three expanded CBNKCs almost lacked PD-1 expression during the expansion period. LAG-3 expression was variable among donors, and no consistent changes were identified during the expansion period. All of the expanded CBNKCs elicited distinct cytotoxicity-mediated growth inhibition on T98G cells. The level of cytotoxicity was gradually decreased based on the prolonged expansion period.

Conclusions

Our established feeder-free expansion system yielded large scale highly purified and cytotoxic NKCs derived from human CB. The system provides a stable supply of clinical grade off-the-shelf NKCs and may be feasible for allogeneic NKC-based immunotherapy for cancers, including GBM.

Comparison of cytotoxic potency between freshly cultured and freshly thawed cytokine-induced killer cells from human umbilical cord blood

Immune cell therapy has been incorporated into cancer therapy over the past few years. Chimeric antigen receptor T cells (Car-T cells) transplantation is a novel and promising therapy for cancer treatment and introduces a new age of immune cell therapy. However, the expensive nature of genetic modification procedures limits the accessibility of Car-T cells for cancer treatment. Cytokine-induced killer cells (CIKs) can kill the target cells in an MHC-non-restricted manner; these cells can be developed to "off-the-shelf" immune cell products for cancer treatment. However, the anti-tumor potency of freshly thawed CIKs is not well documented. This study aimed to fill this gap, evaluating the anti-tumor potency of freshly thawed CIKs compared to that of freshly cultured CIKs. CIKs were produced from the human umbilical cord blood in accordance with published protocols. CIKs were cryopreserved in xeno-free cryomedium that contains 5% DMSO, 10% human serum in phosphate buffer saline at - 86 °C. These cells were thawed and immediately utilized in assays (called freshly thawed CIKs) with freshly cultured cells are control. The expression of the surface markers of CIKs, cytokine production, and in vitro anti-tumor cytotoxic cells of freshly thawed CIKs were evaluated and compared to freshly cultured CIKs. Additionally, the freshly thawed CIKs were injected into the breast of tumor-bearing mice to assess the anti-tumor potency in vivo. The results obtained in freshly thawed CIKs and freshly cultured CIKs demonstrated that the expression of CD3, and CD56 were comparable in both cases. The production of TNF-α, IFN-γ, and IL-10 was slightly reduced in freshly thawed cells compared to the freshly cultured cells. The in vitro lysis toward MCF-7 cancer cells was similar between freshly thawed and freshly cultured CIKs. Moreover, the freshly thawed CIKs displayed anti-breast tumor activity in the breast tumor-bearing mice. The volume of tumors significantly reduced in the mice grafted with freshly thawed CIKs while, conversely, the tumor volume in mice of the placebo group gradually increased. This study substantiated that freshly thawed CIKs preserved their anti-tumor potency in both in vitro and in vivo conditions. The results initially revealed the great potential of UCB-CIKs for "off-the-shelf" CIK product manufacturing. However, further studies on the effects of cryomedia, freezing rate, and thawing procedure should be undertaken before freshly thawed off-the-shelf UCB-CIKs are utilized in clinical trials.

Current status in cellular-based therapies for prevention and treatment of COVID-19

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the pathogen responsible for the coronavirus disease 2019 (COVID-19) outbreaks that resulted in a catastrophic threat to global health, with more than 500 million cases detected and 5.5 million deaths worldwide. Patients with a COVID-19 infection presented with clinical manifestations ranging from asymptomatic to severe symptoms, resulting in acute lung injury, acute respiratory distress syndrome, and even death. Immune dysregulation through delayed innate immune response or impairment of the adaptive immune response is the key contributor to the pathophysiology of COVID-19 and SARS-CoV-2-induced cytokine storm. Symptomatic and supportive therapy is the fundamental strategy in treating COVID-19 infection, including antivirals, steroid-based therapies, and cell-based immunotherapies. Various studies reported substantial effects of immune-based therapies for patients with COVID-19 to modulate the over-activated immune system while simultaneously refining the body's ability to destroy the virus. However, challenges may arise from the complexity of the disease through the genetic variance of the virus itself and patient heterogeneity, causing increased transmissibility and heightened immune system evasion that rapidly change the intervention and prevention measures for SARS-CoV-2. Cell-based therapy, utilizing stem cells, dendritic cells, natural killer cells, and T cells, among others, are being extensively explored as other potential immunological approaches for preventing and treating SARS-CoV-2-affected patients the similar process was effectively proven in SARS-CoV-1 and MERS-CoV infections. This review provides detailed insights into the innate and adaptive immune response-mediated cell-based immunotherapies in COVID-19 patients. The immune response linking towards engineered autologous or allogenic immune cells for either treatment or preventive therapies is subsequently highlighted in an individual study or in combination with several existing treatments. Up-to-date data on completed and ongoing clinical trials of cell-based agents for preventing or treating COVID-19 are also outlined to provide a guide that can help in treatment decisions and future trials.

Current Progress of CAR-NK Therapy in Cancer Treatment

Simple Summary

Chimeric antigen receptor (CAR)-T and -natural killer (NK) therapies are promising in cancer treatment. CAR-NK therapy gains great attention due to the lack of adverse effects observed in CAR-T therapies and to the NK cells’ unique mechanisms of recognizing target cells. Off-the-shelf products are in urgent need, not only for good yields, but also for lower cost and shorter preparation time. The current progress of CAR-NK therapy is discussed.

Abstract

CD8⁺ T cells and natural killer (NK) cells eliminate target cells through the release of lytic granules and Fas ligand (FasL)-induced target cell apoptosis. The introduction of chimeric antigen receptor (CAR) makes these two types of cells selective and effective in killing cancer cells. The success of CAR-T therapy in the treatment of acute lymphoblastic leukemia (ALL) and other types of blood cancers proved that the immunotherapy is an effective approach in fighting against cancers, yet adverse effects, such as graft versus host disease (GvHD) and cytokine release syndrome (CRS), cannot be ignored for the CAR-T therapy. CAR-NK therapy, then, has its advantage in lacking these adverse effects and works as effective as CAR-T in terms of killing. Despite these, NK cells are known to be hard to transduce, expand in vitro, and sustain shorter in vivo comparing to infiltrated T cells. Moreover, CAR-NK therapy faces challenges as CAR-T therapy does, e.g., the time, the cost, and the potential biohazard due to the use of animal-derived products. Thus, enormous efforts are needed to develop safe, effective, and large-scalable protocols for obtaining CAR-NK cells. Here, we reviewed current progress of CAR-NK therapy, including its biological properties, CAR compositions, preparation of CAR-NK cells, and clinical progresses. We also discussed safety issues raised from genetic engineering. We hope this review is instructive to the research community and a broad range of readers.

CAR NK cell therapy in hematologic malignancies and solid tumors; obstacles and strategies to overcome the challenges

Adoptive cell treatment (ACT) utilizing chimeric antigen receptors (CAR) diverts the specificity of safe cells against a target-specific antigen and portrays exceptional potential for cancer treatment. While CAR T cell treatment has risen as a breakthrough with unprecedented results within the therapeutic procedures of human malignancies, different deficiencies including challenging and costly generation processes, strict patient qualification criteria, and undesirable toxicity have ruined its application. Unlike T cells, the application of natural killer (NK) cells has attracted consideration as a reasonable alternative owing to the major histocompatibility complex (MHC)-independency, shorter life expectancy, the potential to create an off-the-shelf immune product, and potent antitumor properties. In this article, we provide an updated review of the differences between CAR T and CAR NK cells, current enhancements in CAR NK design, the available sources for collecting NK cells, and strategies for the transduction step of the CARs to NK cells. Furthermore, we focus on the published and ongoing preclinical and clinical studies of CAR NK treatment strategies both in hematologic malignancies and solid tumors. We also discuss limitations and plausible solutions to improve the perseverance, function, safety, and efficacy of CAR NK cells with a special focus on solid tumors.

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.

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

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

Feeder Cells at the Interface of Natural Killer Cell Activation, Expansion and Gene Editing

Genome engineered natural killer (NK) cell therapies are emerging as a promising cancer immunotherapy platform with potential advantages and remaining uncertainties. Feeder cells induce activation and proliferation of NK cells via cell surface receptor-ligand interactions, supported by cytokines. Feeder cell expanded NK cell products have supported several NK cell adoptive transfer clinical trials over the past decade. Genome engineered NK cell therapies, including CAR-NK cells, seek to combine innate and alloreactive NK cell anti-tumor activity with antigen specific targeting or additional modifications aimed at improving NK cell persistence, homing or effector function. The profound activating and expansion stimulus provided by feeder cells is integral to current applications of clinical-scale genome engineering approaches in donor-derived, primary NK cells. Herein we explore the complex interactions that exist between feeder cells and both viral and emerging non-viral genome editing technologies in NK cell engineering. We focus on two established clinical-grade feeder systems; Epstein-Barr virus transformed lymphoblastoid cell lines and genetically engineered K562.mbIL21.4-1BBL feeder cells.

Overcoming the UCB HSCs -Derived NK cells Dysfunction through Harnessing RAS/MAPK, IGF-1R and TGF-β Signaling Pathways

Background

The natural killer (NK) cells differentiated from umbilical cord blood (UCB) hematopoietic stem cells (HSCs) may be more suitable for cell-based immunotherapy compared to the NK cells from adult donors. This is due to the possibility to choose alloreactive donors and potentially more robust in vivo expansion. However, the cytotoxicity of UCB-HSC-derived NK cells against cancer cells might be suboptimal. To overcome this obstacle, we attempted to generate NK cells with potent antitumor activity by targeting RAS/MAPK, IGF-1R and TGF-β signaling pathways using IL-15, IGF-1 and SIS3 respectively.

Methods

The CD34 + cells were isolated from human UCB mononuclear cells through magnetic activation cell sorting (MACS) with purity of (≥ 90%) and were subjected to differentiate into NK cells. After 21 days of induction with SFTG36 (SCF, FLt-3L, TPO, GM-CSF, IL-3 and IL-6), IS721 (IGF-1, SIS3, IL-7 and IL-21) and IL-15/Hsp70 media, NK cells phenotypes were studied and their cytotoxicity against K562 human erythroleukemia cells and SKOV3 ovarian carcinoma cells was analyzed.

Results

The NK cells induced in SFTG36/IS721 medium were selected for activation due to their higher expression of CD56 + 16 + CD3 −  (93.23% ± 0.75) and mean fluorescence intensity (MFI) of NKG2D + (168.66 ± 20.00) and also a higher fold expansion potential (11.893 ± 1.712) compared to the other groups. These cells once activated with IL-15, demonstrated a higher cytotoxicity against K562 (≥ 90%; P ≤ 0.001) and SKOV3 tumor cells (≥ 65%; P ≤ 0.001) compared to IL-15/Hsp70-activated NK cells.

Conclusions

The differentiation of ex vivo expanded CD34 + cells through manipulation of RAS/MAPK, IGF-1R and TGF-β signaling pathways is an efficient approach for generating functional NK cells that can be used for cancer immunotherapy.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12935-021-01983-z.

HLA Class I Knockout Converts Allogeneic Primary NK Cells Into Suitable Effectors for "Off-the-Shelf" Immunotherapy

Cellular immunotherapy using chimeric antigen receptors (CARs) so far has almost exclusively used autologous peripheral blood-derived T cells as immune effector cells. However, harvesting sufficient numbers of T cells is often challenging in heavily pre-treated patients with malignancies and perturbed hematopoiesis and perturbed hematopoiesis. Also, such a CAR product will always be specific for the individual patient. In contrast, NK cell infusions can be performed in non-HLA-matched settings due to the absence of alloreactivity of these innate immune cells. Still, the infused NK cells are subject to recognition and rejection by the patient's immune system, thereby limiting their life-span in vivo and undermining the possibility for multiple infusions. Here, we designed genome editing and advanced lentiviral transduction protocols to render primary human NK cells unsusceptible/resistant to an allogeneic response by the recipient's CD8+ T cells. After knocking-out surface expression of HLA class I molecules by targeting the B2M gene via CRISPR/Cas9, we also co-expressed a single-chain HLA-E molecule, thereby preventing NK cell fratricide of B2M-knockout (KO) cells via "missing self"-induced lysis. Importantly, these genetically engineered NK cells were functionally indistinguishable from their unmodified counterparts with regard to their phenotype and their natural cytotoxicity towards different AML cell lines. In co-culture assays, B2M-KO NK cells neither induced immune responses of allogeneic T cells nor re-activated allogeneic T cells which had been expanded/primed using irradiated PBMNCs of the respective NK cell donor. Our study demonstrates the feasibility of genome editing in primary allogeneic NK cells to diminish their recognition and killing by mismatched T cells and is an important prerequisite for using non-HLA-matched primary human NK cells as readily available, "off-the-shelf" immune effectors for a variety of immunotherapy indications in human cancer.

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.