Immunoprofiling of cell lines derived from natural killer-cell and natural killer-like T-cell leukemia-lymphoma

Oncogenic alterations in KIR3DL1 in cutaneous acral CD8+ lymphoproliferative disorder

BACKGROUND

Primary cutaneous acral CD8+ T-cell lymphoproliferative disorder (TLPD) is a rare and indolent lymphoma entity. Although TLPD was first identified many years ago, the molecular pathogenesis is still not fully understood.

OBJECTIVES

In order to better understand the molecular pathogenesis of cutaneous acral CD8+ TLPD and to identify further discriminatory markers to differentiate this lymphoma subtype from other CD8+ cutaneous lymphomas, we analysed five cases of cutaneous acral CD8+ TLPD for putative molecular alterations.

METHODS

Somatic alterations were assessed using whole-exome and targeted sequencing of paraffin-embedded tissue. Results were evaluated using immunohistochemical staining of respective relevant proteins. CD8+ cutaneous T-cell lymphomas (n = 12) served as control for KIR3DL1 staining.

RESULTS

Copy number variation analysis revealed a homozygous deletion of the KIR3DL1 gene in two of the analysed cases. This resulted in loss of KIR3DL1 protein expression, which was observed in all cases of cutaneous acral CD8+ TLPD. In contrast, KIR3DL1 expression was more variable in other CD8+ cutaneous T-cell lymphomas with 50% of analysed cases (n = 12) found to be positive. In addition, one further case of acral CD8+ TLPD harboured a loss-of-function mutation in the PIK3R1 gene, presumably activating the phosphoinositide 3-kinase-AKT pathway.

CONCLUSIONS

Alterations of the KIR3DL1 gene may be of pathogenetic relevance for acral CD8+ TLPD. Loss of KIR3DL1 protein expression may support the diagnosis of this indolent lymphoma entity; however, this is not a subtype-specific discriminative feature.

Mnox Nanoenzyme Armed CAR-NK Cells Enhance Solid Tumor Immunotherapy by Alleviating the Immunosuppressive Microenvironment

Adoptively transferred cells usually suffer from exhaustion, limited expansion, and poor infiltration, partially attributing to the complicated immunosuppressive microenvironment of solid tumors. Therefore, it is necessary to explore more effective strategies to improve the poor tumor microenvironment (TME) to efficaciously deliver and support extrinsic effector cells in vivo. Herein, an intelligent biodegradable hollow manganese dioxide nanoparticle (MnOX) that possesses peroxidase activity to catalyze excess H2O2 in the TME to produce oxygen and relieve the hypoxia of solid tumors is developed. MnOX nanoenzymes modified with CD56 antibody could specifically bind CAR-NK (chimeric antigen receptor modified natural killer) cells. It is demonstrated that CAR-NK cells incorporated with MnOX nanoenzymes effectively infiltrate into tumor tissues with an improved TME, which results in superior antitumor activity in solid tumor-bearing mice. The antibody connection between MnOX nanoenzymes and CAR-NK endows the lowest efficient dosage of MnOX. This study features a smart synergistic immunotherapy approach for solid tumors using MnOX nanoenzyme-armed CAR-NK cells, which would provide a valuable tool for immunocyte therapy in solid tumors.

Gene-Based Natural Killer Cell Therapies for the Treatment of Pediatric Hematologic Malignancies

Pediatric blood cancers are among the most common malignancies that afflict children. Intensive chemotherapy is not curative in many cases, and novel therapies are urgently needed. NK cells hold promise for use as immunotherapeutic effectors due to their favorable safety profile, intrinsic cytotoxic properties, and potential for genetic modification that can enhance specificity and killing potential. NK cells can be engineered to express CARs targeting tumor-specific antigens, to downregulate inhibitory and regulatory signals, to secrete cytokine, and to optimize interaction with small molecule engagers. Understanding NK cell biology is key to designing immunotherapy for clinical translation.

Comparable transforming growth factor beta-mediated immune suppression in ex vivo-expanded natural killer cells from cord blood and peripheral blood: implications for adoptive immunotherapy

T cell-based therapies like genetically modified immune cells expressing chimeric antigen receptors have shown robust anti-cancer activity in vivo, especially in patients with blood cancers. However, extending this approach to an "off-the-shelf" setting can be challenging, as allogeneic T cells carry a significant risk of graft-versus-host disease (GVHD). By contrast, allogeneic natural killer (NK) cells recognize malignant cells without the need for prior antigen exposure and have been used safely in multiple cancer settings without the risk of GVHD. However, similar to T cells, NK cell function is negatively impacted by tumor-induced transforming growth factor beta (TGF-β) secretion, which is a ubiquitous and potent immunosuppressive mechanism employed by most malignancies. Allogeneic NK cells for adoptive immunotherapy can be sourced from peripheral blood (PB) or cord blood (CB), and the authors' group and others have previously shown that ex vivo expansion and gene engineering can overcome CB-derived NK cells' functional immaturity and poor cytolytic activity, including in the presence of exogenous TGF-β.  However, a direct comparison of the effects of TGF-β-mediated immune suppression on ex vivo-expanded CB- versus PB-derived NK cell therapy products has not previously been performed. Here the authors show that PB- and CB-derived NK cells have distinctive gene signatures that can be overcome by ex vivo expansion. Additionally, exposure to exogenous TGF-β results in an upregulation of inhibitory receptors on NK cells, a novel immunosuppressive mechanism not previously described. Finally, the authors provide functional and genetic evidence that both PB- and CB-derived NK cells are equivalently susceptible to TGF-β-mediated immune suppression. The authors believe these results provide important mechanistic insights to consider when using ex vivo-expanded, TGF-β-resistant PB- or CB-derived NK cells as novel immunotherapy agents for cancer.

Engineering CAR-NK cells: how to tune innate killer cells for cancer immunotherapy

Cell therapy is an innovative approach that permits numerous possibilities in the field of cancer treatment. CAR-T cells have been successfully used in patients with hematologic relapsed/refractory. However, the need for autologous sources for T cells is still a major drawback. CAR-NK cells have emerged as a promising resource using allogeneic cells that could be established as an off-the-shelf treatment. NK cells can be obtained from various sources, such as peripheral blood (PB), bone marrow, umbilical cord blood (CB), and induced pluripotent stem cells (iPSC), as well as cell lines. Genetic engineering of NK cells to express different CAR constructs for hematological cancers and solid tumors has shown promising preclinical results and they are currently being explored in multiple clinical trials. Several strategies have been employed to improve CAR-NK-cell expansion and cytotoxicity efficiency. In this article, we review the latest achievements and progress made in the field of CAR-NK-cell therapy.

Surface specifically modified NK-92 cells with CD56 antibody conjugated superparamagnetic Fe3O4 nanoparticles for magnetic targeting immunotherapy of solid tumors

Although there has been significant progress in the development of tumor immunotherapies, many challenges still exist for the treatment of solid tumors. Natural killer (NK) cells possess broad-spectrum cytotoxicity against tumors, but their limited migration and infiltration abilities restrict their application in solid tumor therapies. Here, we combined a facile and efficient magnetic-targeting strategy with NK cell-based therapy to develop a novel immunotherapy approach for treating solid tumors. Anti-CD56 antibodies were conjugated with Fe₃O₄ nanoparticles, which could specifically bind with NK-92 cells endowing them with a magnetic field driven targeting ability. These NK-Fe₃O₄ biohybrid nanoparticles were able to facilitate directional migration to the tumor site in vivo under external magnetic field guidance and efficiently inhibit tumor growth. These functionalized NK cells represent a novel approach for solid tumor therapy and may provide a promising modality for cancer interventions in the future.

Chimeric antigen receptor-engineered natural killer cells: a promising cancer immunotherapy

Introduction:Widespread success of CD19 chimeric antigen receptor (CAR) T cells for the treatment of hematological malignancies have shifted the focus from conventional cancer treatments toward adoptive immunotherapy. There are major efforts to improve CAR constructs and to identify new target antigens. Even though the Food and Drug Administration has approved commercialization of some CD19 CART cell therapies, there are still some limitations that restrict their widespread clinical use. The manufacture of autologous products for individual patients is logistically cumbersome and expensive and allogeneic T cell products may pose an appreciable risk of graft-versus-host disease (GVHD).Areas covered:Natural killer (NK) cells are an attractive alternative for CART-based immunotherapies. They have the innate ability to detect and eliminate malignant cells and are safer in the 'off-the-shelf' setting. This review discusses the current progress within the CAR NK cell field, including the challenges, and future prospects. Gene engineered NK cells was used as the search term in PubMed and Google Scholar through to December 2020.Expert opinion:CAR NK cell therapies hold promise as an 'off-the-shelf' cell therapy for cancer. It is hoped that an enhanced understanding of their immunobiology and molecular mechanisms of action will improve their in vivo potency.

Proposal for the designation of the natural killer antigens-positive γδ T-cell subset as γδ NKT-cells: nomenclature based on immunoprofile

Natural killer T (NKT)-cells with both T- and NK-cell antigens can be classified into αβ or γδ type according to the TCR gene expression. The WHO classification of lymphoid neoplasms did not further subdivide the above-mentioned NKT-cell malignancies according to the expression of these TCR types. γδ T-cells can be stimulated and expanded by Zoledronic acid, usually carrying Vγ9 Vδ2 TCR and various NK-associated receptors (NKR) such as CD56, CD94, CD158a, CD158b, CD161, etc. In contrast, αβ T-type NKT-cells are positive for Vα24 Vβ11 TCR. NKR positive γδ T-cells have clearly different features than the NKT-cells with Vα24 Vβ11 TCR type, αβ NKT. NKT-cells carrying γδ TCR should be classified and named as γδ NKT-cells to distinguish the cells explicitly from αβ NKT-cells.

Design and Implementation of NK Cell-Based Immunotherapy to Overcome the Solid Tumor Microenvironment

Natural killer (NK) cells are innate immune effectors capable of broad cytotoxicity via germline-encoded receptors and can have conferred cytotoxic potential via the addition of chimeric antigen receptors. Combined with their reduced risk of graft-versus-host disease (GvHD) and cytokine release syndrome (CRS), NK cells are an attractive therapeutic platform. While significant progress has been made in treating hematological malignancies, challenges remain in using NK cell-based therapy to combat solid tumors due to their immunosuppressive tumor microenvironments (TMEs). The development of novel strategies enabling NK cells to resist the deleterious effects of the TME is critical to their therapeutic success against solid tumors. In this review, we discuss strategies that apply various genetic and non-genetic engineering approaches to enhance receptor-mediated NK cell cytotoxicity, improve NK cell resistance to TME effects, and enhance persistence in the TME. The successful design and application of these strategies will ultimately lead to more efficacious NK cell therapies to treat patients with solid tumors. This review outlines the mechanisms by which TME components suppress the anti-tumor activity of endogenous and adoptively transferred NK cells while also describing various approaches whose implementation in NK cells may lead to a more robust therapeutic platform against solid tumors.

CAR-expressing NK cells for cancer therapy: a new hope

Since the approval in 2017 and the amazing achievement of Kymriah and Yescarta, the number of basic researchers and clinical trials investigating the safety and efficacy of chimeric antigen receptor-expressing T cells (CAR-T cells) has been relentlessly increasing. Up to now, more than 200 clinical trials are listed on clinical trial database of NIH and the basic research is countless. However, the production of allogeneic CAR-T cells products is still expensive and has toxicity. Thus, more effort is needed to develop reliable off-the-shelf cellular therapeutic methods with safety and efficiency for the treatment of patients with cancer. As a kind of innate effector lymphocyte with potent antitumor activity, natural killer cells (NK cells) have attracted much attention. Until now, basic and clinical research has shown that chimeric antigen receptor-expressing NK cell (CAR-NK) therapy may play a significant anti-tumor role and its safety is higher than CAR-T cell therapy. In this review, we discuss advantages and shortages of employing CAR-NK cells as a novel cellular therapy against cancer.

Engineering the Bridge between Innate and Adaptive Immunity for Cancer Immunotherapy: Focus on γδ T and NK Cells

Most studies on genetic engineering technologies for cancer immunotherapy based on allogeneic donors have focused on adaptive immunity. However, the main limitation of such approaches is that they can lead to severe graft-versus-host disease (GvHD). An alternative approach would bolster innate immunity by relying on the natural tropism of some subsets of the innate immune system, such as γδ T and natural killer (NK) cells, for the tumor microenvironment and their ability to kill in a major histocompatibility complex (MHC)-independent manner. γδ T and NK cells have the unique ability to bridge innate and adaptive immunity while responding to a broad range of tumors. Considering these properties, γδ T and NK cells represent ideal sources for developing allogeneic cell therapies. Recently, significant efforts have been made to exploit the intrinsic anti-tumor capacity of these cells for treating hematologic and solid malignancies using genetic engineering approaches such as chimeric antigen receptor (CAR) and T cell receptor (TCR). Here, we review over 30 studies on these two approaches that use γδ T and NK cells in adoptive cell therapy (ACT) for treating cancer. Based on those studies, we propose several promising strategies to optimize the clinical translation of these approaches.

Sialylation of Human Natural Killer (NK) Cells is Regulated by IL-2

Sialic acids are terminal sugars on the cell surface that are found on all cell types including immune cells like natural killer (NK) cells. The attachment of sialic acids to different glycan structures is catalyzed by sialyltransferases in the Golgi. However, the expression pattern of sialyltransferases in NK cells and their expression after activation has not yet been analyzed. Therefore, the present study determines which sialyltransferases are expressed in human NK cells and if activation with IL-2 changes the sialylation of NK cells. The expression of sialyltransferases was analyzed in the three human NK cell lines NK-92, NKL, KHYG-1 and primary NK cells. NK-92 cells were cultured in the absence or presence of IL-2, and changes in the sialyltransferase expression were measured by qPCR. Furthermore, specific sialylation was investigated by flow cytometry. In addition, polySia and NCAM were measured by Western blot analyses. IL-2 leads to a reduced expression of ST8SIA1, ST6GAL1 and ST3GAL1. α-2,3-Sialylation remained unchanged, while α-2,6-sialylation was increased after IL-2 stimulation. Moreover, an increase in the amount of NCAM and polySia was observed in IL-2-activated NK cells, whereas GD3 ganglioside was decreased. In this study, all sialyltransferases that were expressed in NK cells could be identified. IL-2 regulates the expression of some sialyltransferases and leads to changes in the sialylation of NK cells.

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.

A research-driven approach to the identification of novel natural killer cell deficiencies affecting cytotoxic function

Natural killer cell deficiencies (NKDs) are an emerging phenotypic subtype of primary immune deficiency. NK cells provide a defense against virally infected cells using a variety of cytotoxic mechanisms, and patients who have defective NK cell development or function can present with atypical, recurrent, or severe herpesviral infections. The current pipeline for investigating NKDs involves the acquisition and clinical assessment of patients with a suspected NKD followed by subsequent in silico, in vitro, and in vivo laboratory research. Evaluation involves initially quantifying NK cells and measuring NK cell cytotoxicity and expression of certain NK cell receptors involved in NK cell development and function. Subsequent studies using genomic methods to identify the potential causative variant are conducted along with variant impact testing to make genotype-phenotype connections. Identification of novel genes contributing to the NKD phenotype can also be facilitated by applying the expanding knowledge of NK cell biology. In this review, we discuss how NKDs that affect NK cell cytotoxicity can be approached in the clinic and laboratory for the discovery of novel gene variants.

Genome-wide analyses and functional profiling of human NK cell lines

Natural killer (NK) cell lines, including YTS, NK92, NK3.3, and NKL, represent excellent models for the study of human natural killer cells. While phenotypic and functional differences between these cell lines have been reported, a multi-parametric study, encompassing genomic, phenotypic, and functional assays, has not been performed. Here, using a combination of techniques including microarray and copy number analyses, flow cytometry, and functional assays, we provide in-depth genetic, functional, and phenotypic comparison of YTS, NK92, NK3.3, and NKL cell lines. Specifically, we found that while the cell lines shared similarities in enrichment of growth and survival pathways, they had differential expression of 557 genes, including genes related to NK cell development, survival, and function. In addition, we provide genetic and phenotypic analyses that demonstrate distinct developmental origins of NK92, YTS, and NKL cell lines. Specifically, NK92 has a phenotype associated with the CD56bright NK cell subset, while both YTS and NKL appear more CD56dim-like. Finally, by classifying cell lines based on their lytic potential, we identified genes differentially expressed between NK cell lines with high and low lytic function. Taken together, these data provide the first comprehensive genetic, phenotypic, and functional analyses of these commonly used NK cell lines and provides deeper understanding into their origins and function. This will ultimately improve their use as models for human NK cell biology.

Discovery of a novel natural killer cell line with distinct immunostimulatory and proliferative potential as an alternative platform for cancer immunotherapy

BACKGROUND

Human natural killer (NK) cell lines serve as an attractive source for adoptive immunotherapy, but NK-92 remains the only cell line being assessed in the clinic. Here, we established a novel NK cell line, NK101, from a patient with extra-nodal natural killer/T-cell lymphoma and examined its phenotypic, genomic and functional characteristics.

METHODS

Single cell suspensions from lymphoma tissue were expanded with anti-NKp46/anti-CD2-coated beads in the presence of IL-2. A continuously growing CD56⁺ cell clone was selected and designated as NK101. Flow cytometry and RNA sequencing were used to characterize phenotypic and genomic features of NK101. In vitro cytotoxicity and IFN-γ/TNF-α secretion were measured by flow cytometry-based cytotoxicity assay and enzyme-linked immunosorbent assay, respectively, after direct co-culture with tumor cells. Immunomodulatory potential of NK101 was assessed in an indirect co-culture system using conditioned medium. Finally, in vivo antitumor efficacy was evaluated in an immunocompetent, syngeneic 4T1 mammary tumor model.

RESULTS

NK101 displayed features of CD56^dimCD62L⁺ intermediate stage NK subset with the potential to simultaneously act as a cytokine producer and a cytotoxic effector. Comparative analysis of NK101 and NK-92 revealed that NK101 expressed lower levels of perforin and granzyme B that correlated with weaker cytotoxicity, but produced higher levels of pro-inflammatory cytokines including IFN-γ and TNF-α. Contrarily, NK-92 produced greater amounts of anti-inflammatory cytokines, IL-1 receptor antagonist and IL-10. Genome-wide analysis revealed that genes associated with positive regulation of leukocyte proliferation were overexpressed in NK101, while those with opposite function were highly enriched in NK-92. The consequence of such expressional and functional discrepancies was well-represented in (i) indirect co-culture system where conditioned medium derived from NK101 induced greater proliferation of human peripheral blood mononuclear cells and (ii) immunocompetent 4T1 tumor model where peritumoral injections of NK101 displayed stronger anti-tumor activities by inducing higher tumor-specific immune responses. In a manufacturing context, NK101 not only required shorter recovery time after thawing, but also exhibited faster growth profile than NK-92, yielding more than 200-fold higher cell numbers after 20-day culture.

CONCLUSION

NK101 is a unique NK cell line bearing strong immunostimulatory potential and substantial scalability, providing an attractive source for adoptive cancer immunotherapy.

CAR-Expressing Natural Killer Cells for Cancer Retargeting

Since the approval in 2017 and the outstanding success of Kymriah® and Yescarta®, the number of clinical trials investigating the safety and efficacy of chimeric antigen receptor-modified autologous T cells has been constantly rising. Currently, more than 200 clinical trials are listed on clinicaltrial.gov. In contrast to CAR-T cells, natural killer (NK) cells can be used from allogeneic donors as an "off the shelf product" and provide alternative candidates for cancer retargeting. This review summarises preclinical results of CAR-engineered NK cells using both primary human NK cells and the cell line NK-92, and provides an overview about the first clinical CAR-NK cell studies targeting haematological malignancies and solid tumours, respectively.

Chimeric antigen receptor expression in natural killer cell line NK-92 by transduction with lentiviral particles pseudotyped with the surface glycoproteins of the measles virus vaccine strain

Cancer immunotherapy with T-cells that carry chimeric antigen receptors is currently on cutting edge of modern oncology. Autotransplantation of T-lymphocytes with chimeric receptor specific for certain tumor antigen proves to be clinically effective, but costly. Linear carriers of chimeric antigen receptors based on natural killer NK-92 cell culture may be an affordable alternative, however, this culture is resistant to lentiviral transduction. Recently, lentiviral vectors, pseudotyped with surface glycoproteins of the measles virus vaccine strain, have recently been successfully applied for transduction of primary immune cells. The aim of the work was to assess the efficiency of transduction of NK-92 cells with lentivirus vectors, pseudotyped with measles F and H surface glycoproteins, as well as to establish optimal conditions for selection of NK-92 transduced with the chimeric receptor against CD20 and to evaluate the culture’s cytotoxic potential. The results showed that the maximum infectious titer is achieved using the H∆18 variant in combination with F∆30, and the use of the TBK1/IKKɛ inhibitor BX795 results in additional 3-fold increase in the infectious titer. CAR-expressing NK-92 were able to suppress the proliferation of CD20+ cell line Raji in lower effector-to-target ratios than unmodified NK-92.

Chimeric Antigen Receptor Expressing Natural Killer Cells for the Immunotherapy of Cancer

Adoptive cell therapy has emerged as a powerful treatment for advanced cancers resistant to conventional agents. Most notable are the remarkable responses seen in patients receiving autologous CD19-redirected chimeric antigen receptor (CAR) T cells for the treatment of B lymphoid malignancies; however, the generation of autologous products for each patient is logistically cumbersome and has restricted widespread clinical use. A banked allogeneic product has the potential to overcome these limitations, yet allogeneic T-cells (even if human leukocyte antigen-matched) carry a major risk of graft-versus-host disease (GVHD). Natural killer (NK) cells are bone marrow-derived innate lymphocytes that can eliminate tumors directly, with their activity governed by the integration of signals from activating and inhibitory receptors and from cytokines including IL-15, IL-12, and IL-18. NK cells do not cause GVHD or other alloimmune or autoimmune toxicities and thus, can provide a potential source of allogeneic “off-the-shelf” cellular therapy, mediating major anti-tumor effects without inducing potentially lethal alloreactivity such as GVHD. Given the multiple unique advantages of NK cells, researchers are now exploring the use of CAR-engineered NK cells for the treatment of various hematological and non-hematological malignancies. Herein, we review preclinical data on the development of CAR-NK cells, advantages, disadvantages, and current obstacles to their clinical use.

Epigenetic and Posttranscriptional Regulation of CD16 Expression during Human NK Cell Development

The surface receptor FcγRIIIA (CD16a) is encoded by the FCGR3A gene and is acquired by human NK cells during maturation. NK cells bind the Fc portion of IgG via CD16a and execute Ab-dependent cell-mediated cytotoxicity, which is critical for the effectiveness of several antitumor mAb therapies. The role of epigenetic regulatory mechanisms controlling transcriptional and posttranscriptional CD16 expression in NK cells is unknown. In this study, we compared specific patterns of DNA methylation and expression of FCGR3A with FCGR3B, which differ in cell type-specific expression despite displaying nearly identical genomic sequences. We identified a sequence within the FCGR3A promoter that selectively exhibits reduced methylation in CD16a+ NK cells versus CD16a- NK cells and neutrophils. This region contained the transcriptional start site of the most highly expressed CD16a isoform in NK cells. Luciferase assays revealed remarkable cell-type specificity and methylation-dependent activity of FCGR3A- versus FCGR3B-derived sequences. Genomic differences between FCGR3A and FCGR3B are enriched at CpG dinucleotides, and mutation of variant CpGs reversed cell-type specificity. We further identified miR-218 as a posttranscriptional negative regulator of CD16a in NK cells. Forced overexpression of miR-218 in NK cells knocked down CD16a mRNA and protein expression. Moreover, miR-218 was highly expressed in CD16a- NK cells compared with CD16a+ NK cells. Taken together, we propose a system of FCGR3A regulation in human NK cells in which CpG dinucleotide sequences and concurrent DNA methylation confer developmental and cell type-specific transcriptional regulation, whereas miR-218 provides an additional layer of posttranscriptional regulation during the maturation process.

Chimeric antigen receptor-engineered natural killer and natural killer T cells for cancer immunotherapy

Natural killer (NK) cells of the innate immune system and natural killer T (NKT) cells, which have roles in both the innate and adaptive responses, are unique lymphocyte subsets that have similarities in their functions and phenotypes. Both cell types can rapidly respond to the presence of tumor cells and participate in immune surveillance and antitumor immune responses. This has incited interest in the development of novel cancer therapeutics based on NK and NKT cell manipulation. Chimeric antigen receptors (CARs), generated through the fusion of an antigen-binding region of a monoclonal antibody or other ligand to intracellular signaling domains, can enhance lymphocyte targeting and activation toward diverse malignancies. Most of the CAR studies have focused on their expression in T cells; however, the functional heterogeneity of CAR T cells limits their therapeutic potential and is associated with toxicity. CAR-modified NK and NKT cells are becoming more prevalent because they provide a method to direct these cells more specifically to target cancer cells, with less risk of adverse effects. This review will outline current NK and NKT cell CAR constructs and how they compare to conventional CAR T cells, and discuss future modifications that can be explored to advance adoptive cell transfer of NK and NKT cells.

Id2 Collaborates with Id3 To Suppress Invariant NKT and Innate-like Tumors

Inhibitor of DNA binding (Id) proteins, including Id1-4, are transcriptional regulators involved in promoting cell proliferation and survival in various cell types. Although upregulation of Id proteins is associated with a broad spectrum of tumors, recent studies have identified that Id3 plays a tumor-suppressor role in the development of Burkitt's lymphoma in humans and hepatosplenic T cell lymphomas in mice. In this article, we report rapid lymphoma development in Id2/Id3 double-knockout mice that is caused by unchecked expansion of invariant NKT (iNKT) cells or a unique subset of innate-like CD1d-independent T cells. These populations began to expand in neonatal mice and, upon malignant transformation, resulted in mortality between 3 and 11 mo of age. The malignant cells also gave rise to lymphomas upon transfer to Rag-deficient and wild-type hosts, reaffirming their inherent tumorigenic potential. Microarray analysis revealed a significantly modified program in these neonatal iNKT cells that ultimately led to their malignant transformation. The lymphoma cells demonstrated chromosome instability along with upregulation of several signaling pathways, including the cytokine-cytokine receptor interaction pathway, which can promote their expansion and migration. Dysregulation of genes with reported driver mutations and the NF-κB pathway were found to be shared between Id2/Id3 double-knockout lymphomas and human NKT tumors. Our work identifies a distinct premalignant state and multiple tumorigenic pathways caused by loss of function of Id2 and Id3. Thus, conditional deletion of Id2 and Id3 in developing T cells establishes a unique animal model for iNKT and relevant innate-like lymphomas.

Diagnostic and Biological Significance of KIR Expression Profile Determined by RNA-Seq in Natural Killer/T-Cell Lymphoma

Natural killer/T-cell lymphoma (NKTCL) is a rare, aggressive form of non-Hodgkin lymphoma that is generally incurable at more advanced stages with systemic involvement. Clonal diagnostic markers (eg, unique T- or B-cell receptor rearrangements) are not available for NKTCLs. Killer cell immunoglobulin like receptors (KIRs) are a family of type I transmembrane glycoproteins involved in the inhibition or activation of NK cells. A restricted expression profile of KIRs has been proposed as clonal markers of NK-cell proliferations. Here we evaluated the transcription profile of all KIR family genes and C-type lectin receptor genes using RNA sequencing on NKTCL cases (n = 17) and NK-cell lines (n = 3). The expression of all KIRs tended to be markedly reduced or absent in NKTCL, except for the KIR family member killer Ig-like receptor 2DL4 (KIR2DL4; alias CD158D), which was selectively overexpressed in the majority (59%) of cases. No specific expression pattern was observed for C-type lectin receptors. KIR2DL4 is an unusual member of the KIR family that recognizes human leukocyte antigen G and mediates NK-cell activation through inducing proliferation and survival pathways such as AKT and NF-κB. Stable knockdown of KIR2DL4 in two malignant NK-cell lines with high KIR2DL4 expression significantly reduced cell growth. Selective overexpression of KIR2DL4 and down-regulation of inhibitory KIRs may contribute to NKTCL pathogenesis.

NK-92: an 'off-the-shelf therapeutic' for adoptive natural killer cell-based cancer immunotherapy

Natural killer (NK) cells are increasingly considered as immunotherapeutic agents in particular in the fight against cancers. NK cell therapies are potentially broadly applicable and, different from their T cell counterparts, do not cause graft-versus-host disease. Efficacy and clinical in vitro or in vivo expansion of primary NK cells will however always remain variable due to individual differences of donors or patients. Long-term storage of clinical NK cell lots to allow repeated clinical applications remains an additional challenge. In contrast, the established and well-characterized cell line NK-92 can be easily and reproducibly expanded from a good manufacturing practice (GMP)-compliant cryopreserved master cell bank. Moreover, no cost-intensive cell purification methods are required. To date, NK-92 has been intensively studied. The cells displayed superior cytotoxicity against a number of tumor types tested, which was confirmed in preclinical mouse studies. Subsequent clinical testing demonstrated safety of NK-92 infusions even at high doses. Despite the phase I nature of the trials conducted so far, some efficacy was noted, particularly against lung tumors. Furthermore, to overcome tumor resistance and for specific targeting, NK-92 has been engineered to express a number of different chimeric antigen receptors (CARs), including targeting, for example, CD19 or CD20 (anti-B cell malignancies), CD38 (anti-myeloma) or human epidermal growth factor receptor 2 (HER2; ErbB2; anti-epithelial cancers). The concept of an NK cell line as an allogeneic cell therapeutic produced 'off-the-shelf' on demand holds great promise for the development of effective treatments.

Downregulation of miR-15a due to LMP1 promotes cell proliferation and predicts poor prognosis in nasal NK/T-cell lymphoma

Nasal NK/T-cell lymphoma (NNKTL) is an Epstein-Barr virus (EBV)-associated malignancy and has distinct clinical and histological features. However, its genetic features are hitherto unclear. MicroRNAs (miRNAs) play a crucial role in the pathogenesis of several malignancies via regulating gene expression. In this study, we investigated whether the specific microRNAs were related to the tumor behaviors in NNKTL. MiRNA array and Quantitative RT-PCR analyses revealed that miR-15a was expressed at a much lower level in NNKTL cells (SNK-1, SNK-6, and SNT-8) than in normal peripheral NK cells and EBV-negative NK cell line KHYG-1. Quantitative PCR and western blot analyses showed that the expression of MYB and cyclin D1, which are validated targets of miR-15a, was higher in NNKTL cells. Transfection of NNKTL cells (SNK-6 and SNT-8) with a miR-15a precursor decreased MYB and cyclin D1 levels, thereby blocking G1/S transition and cell proliferation. Knockdown of EBV-encoded latent membrane protein 1 (LMP1) significantly increased miR-15a expression in SNK-6 cells. In NNKTL tissues, we found that reduced miR-15a expression, which correlated with MYB and cyclin D1 expression, was associated with poor prognosis of NNKTL patients. These data suggest that downregulation of miR-15a, possibly due to LMP1, implicates in the pathogenesis of NNKTL by inducing cell proliferation via MYB and cyclin D1. Thus, miR-15a could be a potential target for antitumor therapy and a prognostic predictor for NNKTL.

Expression of CD70 in nasal natural killer/T cell lymphoma cell lines and patients; its role for cell proliferation through binding to soluble CD27

Nasal natural killer (NK)/T cell lymphoma (NNKTL) is associated with Epstein-Barr virus (EBV). The present study analysed gene expression patterns of the NNKTL cell lines SNK6, SNK1 and SNT8, which are positive for EBV and latent membrane protein (LMP)-1, using a complementary DNA array analysis. We found that CD70 was specifically expressed in SNK6 and SNT8. Reverse transcription polymerase chain reaction and flow cytometric analyses confirmed that CD70 was expressed in all 3 NNKTL cell lines, but not in the other EBV-positive NK-cell lines. In vitro studies showed that NNKTL cell lines proliferated, in a dose-dependent fashion, in response to exogenous soluble CD27, which is the ligand for CD70. In NNKTL patients, we confirmed that the CD70 was expressed on the lymphoma cells in NNKTL tissues and that soluble CD27 was present in sera at higher levels as compared to healthy individuals. Finally, complement-dependent cytotoxicity assay showed that anti-CD70 antibody mediated effective complement-dependent killing of NNKTL cells and the affected target CD70 expression on the cells. These results suggest that CD70 acts as a functional receptor binding to soluble CD27, resulting in lymphoma progression and that immunotherapy using anti-CD70 antibody may be a potential candidate for treatment for NNKTL.

Dysregulated microRNAs affect pathways and targets of biologic relevance in nasal-type natural killer/T-cell lymphoma

We performed a comprehensive genome-wide miRNA expression profiling of extranodal nasal-type natural killer/T-cell lymphoma (NKTL) using formalin-fixed paraffin-embedded tissue (n = 30) and NK cell lines (n = 6) compared with normal NK cells, with the objective of understanding the pathogenetic role of miRNA deregulation in NKTL. Compared with normal NK cells, differentially expressed miRNAs in NKTL are predominantly down-regulated. Re-expression of down-regulated miRNAs, such as miR-101, miR-26a, miR26b, miR-28-5, and miR-363, reduced the growth of the NK cell line and modulated the expression of their predicted target genes, suggesting the potential functional role of the deregulated miRNAs in the oncogenesis of NKTL. Taken together, the predicted targets whose expression is inversely correlated with the expression of deregulated miRNA in NKTL are significantly enriched for genes involved in cell cycle-related, p53, and MAPK signaling pathways. We also performed immunohistochemical validation for selected target proteins and found overexpression of MUM1, BLIMP1, and STMN1 in NKTL, and notably, a corresponding increase in MYC expression. Because MYC is known to cause repression of miRNA expression, it is possible that MYC activation in NKTL may contribute to the suppression of the miRNAs regulating MUM1, BLIMP1, and STMN1.

Interleukin-2 induces NF-kappaB activation through BCL10 and affects its subcellular localization in natural killer lymphoma cells

Deregulation of nuclear factor (NF)-kappaB signalling is common in cancers and is essential for tumourigenesis. Constitutive NF-kappaB activation in extranodal natural killer (NK)-cell lymphoma, nasal type (ENKL) is known to be associated with aberrant nuclear translocation of BCL10. Here we investigated the mechanisms leading to NF-kappaB activation and BCL10 nuclear localization in ENKLs. Given that ENKLs are dependent on T-cell-derived interleukin-2 (IL2) for cytotoxicity and proliferation, we investigated whether IL2 modulates NF-kappaB activation and BCL10 subcellular localization in ENKLs. In the present study, IL2-activated NK lymphoma cells were found to induce NF-kappaB activation via the PI3K/Akt pathway, leading to an increase in the entry of G(2)/M phase and concomitant transcription of NF-kappaB-responsive genes. We also found that BCL10, a key mediator of NF-kappaB signalling, participates in the cytokine receptor-induced activation of NF-kappaB. Knockdown of BCL10 expression resulted in deficient NF-kappaB signalling, whereas Akt activation was unaffected. Our results suggest that BCL10 plays a role downstream of Akt in the IL2-triggered NF-kappaB signalling pathway. Moreover, the addition of IL2 to NK cells led to aberrant nuclear translocation of BCL10, which is a pathological feature of ENKLs. We further show that BCL10 can bind to BCL3, a transcriptional co-activator and nuclear protein. Up-regulation of BCL3 expression was observed in response to IL2. Similar to BCL10, the expression and nuclear translocation of BCL3 were induced by IL2 in an Akt-dependent manner. The nuclear translocation of BCL10 was also dependent on BCL3 because silencing BCL3 by RNA interference abrogated this translocation. We identified a critical role for BCL10 in the cytokine receptor-induced NF-kappaB signalling pathway, which is essential for NK cell activation. We also revealed the underlying mechanism that controls BCL10 nuclear translocation in NK cells. Our findings provide insight into a molecular network within the NF-kappaB signalling pathway that promotes the pathogenesis of NK cell lymphomas.

Irradiated KHYG-1 retains cytotoxicity: Potential for adoptive immunotherapy with a natural killer cell line

PURPOSE

To evaluate gamma-irradiation on KHYG-1, a highly cytotoxic natural killer (NK) cell line and potential candidate for cancer immunotherapy.

METHODS AND MATERIALS

The NK cell line KHYG-1 was irradiated at 1 gray (Gy) to 50 Gy with gamma-irradiation, and evaluated for cell proliferation, cell survival, and cytotoxicity against tumor targets.

RESULTS

We showed that a dose of at least 10 Gy was sufficient to inhibit proliferation of KHYG-1 within the first day but not its cytolytic activity. While 50 Gy had an apoptotic effect in the first hours after irradiation, the killing of K562 and HL60 targets was not different from non-irradiated cells but was reduced for the Ph + myeloid leukemia lines, EM-2 and EM-3.

CONCLUSIONS

gamma-irradiation (at least 10 Gy) of KHYG-1 inhibits cell proliferation but does not diminish its enhanced cytolytic activity against several tumor targets. This study suggests that KHYG-1 may be a feasible immunotherapeutic agent in the treatment of cancers.

Cell death by bortezomib-induced mitotic catastrophe in natural killer lymphoma cells

The proteasome inhibitor bortezomib (PS-341/Velcade) is used for the treatment of relapsed and refractory multiple myeloma and mantle-cell lymphoma. We recently reported its therapeutic potential against natural killer (NK)-cell neoplasms. Here, we investigated the molecular mechanisms of bortezomib-induced cell death in NK lymphoma cells. NK lymphoma cell lines (SNK-6 and NK-YS) and primary cultures of NK lymphomas treated with bortezomib were examined for alterations in cell viability, apoptosis, cellular senescence, and cell cycle status. Bortezomib primarily induced mitochondrial apoptosis in NK-YS cells and in primary lymphoma cells at the same concentration as reported in myeloma cells. Unexpectedly, SNK-6 cells required a significantly higher median inhibitory concentration of bortezomib (23 nmol/L) than NK-YS and primary lymphoma cells (6-13 nmol/L). Apoptosis was limited in SNK-6 cells due to the extensively delayed turnover of Bcl-2 family members. These cells were killed by bortezomib, albeit at higher pharmacologic concentrations, via mitotic catastrophe-a mitotic cell death associated with M-phase arrest, cyclin B1 accumulation, and increased CDC2/CDK1 activity. Our results suggest that, in addition to cell death by apoptosis at lower bortezomib concentrations, NK lymphoma cells resistant to bortezomib-induced apoptosis can be killed via mitotic catastrophe, an alternative cell death mechanism, at higher pharmacologic concentrations of bortezomib. Hence, activating mitotic catastrophe by bortezomib may provide a novel therapeutic approach for treating apoptosis-resistant NK-cell malignancies and other cancers.

An Epstein-Barr virus positive natural killer lymphoma xenograft derived for drug testing

Natural killer (NK) lymphomas occurring more frequently in the Far East and South America respond poorly to anthracycline-based regimens. Here we report an in vivo NK lymphoma xenograft (NK-S1) derived from the testicular metastasis of a patient with an extranodal NK lymphoma (nasal type). The NK-S1 xenograft, established in severe combined immune deficient (SCID) mice retained the same imunophenotypic features as the original tumor. NK-S1 disseminated intra-abdominally to the testis, intestine and liver. Although doxorubicin, rapamycin, bevacizumab, rapamycin-doxorubicin, and bevacizumab-doxorubicin had no effects on the growth of subcutaneous NK-S1 xenografts, intraperitoneal (IP) delivery of cyclophosphamide caused complete tumor regression; this tumor regression was associated with apoptosis, upregulation of activated caspase-3, and cleaved Poly(ADP-ribose) polymerase (PARP). In an IP model of NK lymphoma, cyclophosphamide also prolonged the survival of mice and potently inhibited tumor dissemination and ascites formation. Our data suggest that the NK-S1 xenograft is a useful tool for screening preclinical drugs, and cyclophosphamide may be a useful drug for the treatment of this disease.

Transcription Factor Expression in Cell Lines Derived from Natural Killer-Cell and Natural Killer-Like T-Cell Leukemia-Lymphoma

Although a number of transcription factors (TFs) have been identified that play a pivotal role in the development of hematopoietic lineages, only little is known about factors that may influence development and lineage commitment of natural killer (NK) or NK-like T (NKT)-cells. Obviously to fully appreciate the NK- and NKT-cell differentiation process, it is important to identify and characterize the TFs effecting the NK- and NKT-cell lineage. Furthermore, these TFs may play a role in NK- or NKT-cell leukemias, in which the normal differentiation program is presumably disturbed. The present study analyzed the expression of the following 13 TFs: AML1, CEBPA, E2A, ETS1, GATA1, GATA2, GATA3, IKAROS, IRF1, PAX5, PU1, TBET and TCF1 in 7 malignant NK-cell lines together with 5 malignant NKT-cell lines, 5 T-cell acute lymphoblastic leukemia (ALL) cell lines including 3 gamma/delta T-cell receptor (TCR) type and 2 alpha/beta TCR type, and 3 B-cell precursor (BCP) leukemia cell lines. AML1, E2A, ETS1, IKAROS and IRF1 were found to be positive for all cell lines tested whereas GATA1 turned out to be universally negative. CEBPA, PAX5 and PU1 were negative for all cell lines tested except in the three positive BCP-cell lines. GATA2 was positive for 3/5 T-cell lines but negative for the other cell lines. GATA3 was positive for 7/7 NK-, 4/5 NKT-, 5/5 T- and 2/3 BCP-cell lines. TBET was positive for all NK- and NKT-cell lines and negative for all T- and BCP-cell lines except one BCP-cell line. In contrast to the expression of TBET, TCF1 was negative for all NK- and NKT-cell lines, being positive for 4/5 T- and 1/3 BCP-cell lines. Expression analysis of TFs revealed that NK- and NKT-cell lines showed identical profiles, clearly distinct from those of the other T-ALL or BCP-ALL leukemia-derived cell lines..

Epstein-Barr virus–associated lymphoproliferative disorders

Epstein-Barr virus (EBV) is a member of the human herpesvirus family that was initially isolated from a cultured Burkitt lymphoma cell line by Epstein et al in 1964. Subsequent studies have proven that it is the causative agent in most cases of infectious mononucleosis. Primary infection is usually asymptomatic in childhood; but in adulthood, it is associated with a self-limiting infectious mononucleosis syndrome in approximately one third of the cases. EBV has been linked to many human neoplasms including hematopoietic, epithelial, and mesenchymal tumors. In this review, we will only discuss the EBV-associated lymphoproliferative disorders, dividing them into B-cell, T/NK-cell, and HIV-related lymphoproliferative disorders.

Genomic analysis of CD8+ NK/T cell line, 'SRIK-NKL', with array-based CGH (aCGH), SKY/FISH and molecular mapping

We performed aCGH, SKY/FISH, molecular mapping and expression analyses on a permanent CD8+ NK/T cell line, 'SRIK-NKL' established from a lymphoma (ALL) patient, in attempt to define the fundamental genetic profile of its unique NK phenotypes. aCGH revealed hemizygous deletion of 6p containing genes responsible for hematopoietic functions. The SKY demonstrated that a constitutive reciprocal translocation, rcpt(5;14)(p13.2;q11) is a stable marker. Using somatic hybrids containing der(5) derived from SRIK-NKL, we found that the breakpoint in one homologue of no. 5 is located upstream of IL7R and also that the breakpoint in no. 14 is located within TRA@. The FISH analysis using a BAC which contains TRA@ and its flanking region further revealed a approximately 231kb deletion within 14q11 in the der(5) but not in the normal homologue of no. 14. The RT-PCR analysis detected mRNA for TRA@ transcripts which were extending across, but not including, the deleted region. IL7R was detected at least at mRNA levels. These findings were consistent with the immunological findings that TRA@ and IL7R are both expressed at mRNA levels and TRA@ at cytoplasmic protein levels in SRIK-NKL cells. In addition to rcpt(5;14), aCGH identified novel copy number abnormalities suggesting that the unique phenotype of the SRIK-NKL cell line is not solely due to the TRA@ rearrangement. These findings provide supportive evidence for the notion that SRIK-NKL cells may be useful for studying not only the function of NK cells but also genetic deregulations associated with leukemiogenesis.

Concomitant increase of LMP1 and CD25 (IL-2-receptor alpha) expression induced by IL-10 in the EBV-positive NK lines SNK6 and KAI3

Extranodal, nasal NK/T-cell lymphomas are regularly Epstein-Barr virus (EBV)-positive, with a type II latency pattern, expressing thus EBNA-1 and LMP1. The contribution of EBV to the tumor development is not known. Similarly to normal natural killer (NK) cells, cell lines derived from malignancies with a NK phenotype require IL-2 for in vitro proliferation. In our effort to explore the contribution of EBV, particularly the role of the LMP1 protein, to the pathogenesis of the NK lymphoma we found that its expression, studied in the NK-lines SNK6 and KAI3, depended on the supply of IL-2 or other cytokines. In the absence of IL-2 other cytokines, such as IL-10 and IFN-gamma, could maintain LMP1, but the cells did not proliferate. When grown in IL-2, the SNK6 cells produced IL-10 and IFN-gamma, and these cytokines mediated the expression of LMP1. IL-10 treatment enhanced, while IFN-gamma receptor blocking antibody reduced, the expression of CD25 and CD54 in the EBV-positive, but not in the EBV-negative lines. IL-10 treated cells required lower amount of IL-2 for proliferation compared to the untreated cells. This effect was seen only with the EBV-positive NK lines in which LMP1 and CD25 were concomitantly upregulated. By this mechanism EBV could have an important role in the development of NK lymphoma since the inflammatory component in the tumor tissue can provide these cytokines.

Impairment of double-strand breaks repair and aberrant splicing of ATM and MRE11 in leukemia-lymphoma cell lines with microsatellite instability

Mutations of DNA double-strand breaks (DSB) repair genes, ATM, MRE11, RAD50, NBS1 and ATR, are postulated to play a role in the development of gastrointestinal malignancies with an impaired mismatch repair (MMR) function. In the present study, mutations of these genes together with the presence of microsatellite instability (MSI) were examined in 50 leukemia-lymphoma cell lines. MSI was detected in 13 (26%) lines. Mutations of intronic mononucleotide repeats in ATM and MRE11 were found in nine and six lines, respectively, whereas mutations of mononucleotide repeats of RAD50 were found in only one line, and none were found in either NBS1 or ATR. Frequencies of ATM and MRE11 mutations were significantly higher in MSI-positive than MSI-negative lines. These mutations generated aberrant splicing in both genes. The intensity of the aberrant transcript of ATM (497del22) was stronger in five lines harboring mononucleotide mutations of 2 bp or more than in the lines without or with a 1-bp mutation. The intensity of the aberrant transcript of MRE11 (315del88) was stronger in four lines with mononucleotide mutations than in lines without. The expression levels of ATM and MRE11 transcripts in MSI-positive lines were significantly higher than those in MSI-negative lines. MSI-positive cell lines showed delay or abrogation of DSB repair. The present study suggests that impairment of the MMR system causes aberrant transcripts in the DSB repair genes ATM and MRE11. This might result in inactivation of the DSB repair system, thus inducing an acceleration of genome instability and accumulation of genetic damage.

KHYG-1, a model for the study of enhanced natural killer cell cytotoxicity

OBJECTIVE

To compare the cytotoxicity of KHYG-1 with other natural killer (NK)/NK T-cell lines and identify molecules that may be associated with enhanced cytotoxicity, thereby eventually leading to improved NK cell-mediated cancer immunotherapy.

MATERIALS AND METHODS

NK/NK T-cell lines KHYG-1, NK-92, YT, and SNT-8 were compared with a novel flow cytometric cytotoxicity assay under different culture conditions. Transcription, expression, and phosphorylation studies were performed using polymerase chain reaction sequence-specific primers, reverse transcription polymerase chain reaction, immunoblotting, and flow cytometry.

RESULTS

KHYG-1 is a highly cytotoxic cell line, exceeding the cytolytic capacity of the other cell lines against K562. KHYG-1 is also highly cytotoxic against the leukemia cell lines EM2, EM3, and HL60. The novel activation receptor NKp44 and its adaptor, DAP12, NKG2D, and constitutively phosphorylated ERK2 may be associated with the enhanced cytotoxicity of KHYG-1. This cell line most likely mediates cytolysis by granzyme M (but not granzymes A and B) together with perforin, which is constitutively fully cleaved to the 60-kD form, in contrast to the other cell lines.

CONCLUSION

KHYG-1 is a valuable model for the study of enhanced cytotoxicity by NK cells. In addition to the activation of NKp44, KHYG-1 may induce apoptosis of tumor cells by the newly described granzyme M/perforin pathway. Targeted modifications of effector molecules demonstrated in this model could generate NK cells with even greater killing ability that may be particularly attractive for clinical application. Moreover, our demonstration of greater cytotoxicity of KHYG-1 versus NK-92 cells, already in clinical trials, suggests a direct therapeutic role for KHYG-1.

Establishment and characterization of SRIK-NKL: a novel CD8+ natural killer/T cell line derived from a patient with leukemic phase of acute lymphoblastic lymphoma

The distinction between T cells and NK cells is difficult, and becoming more complex, as the diversity of the human lymphocyte repertoire is evident. We report the establishment of a permanent CD8+ NK/T cell line (SRIK-NKL) from a patient with leukemic phase of acute lymphoblastic lymphoma having characteristics of both NK and T cells, and extensively describe its phenotype, including cytotoxic activity, NK cell receptor expression, and other molecules critical for immune function. We further compare SRIK-NKL to other available NK/NK-T cell lines. SRIK-NKL may be useful for studying NK cell development, functions, and modulation, leading to novel strategies for treatment of autoimmune disease, infection, and cancer.

Highly efficient delivery of p16 antitumor peptide into aggressive leukemia/lymphoma cells using a novel transporter system

Molecular targeting of hematopoietic malignancies has been generally hindered by technological obstacles to gene delivery in the neoplastic cells. The development of peptide delivery systems based on protein transduction domains has recently gained attention as a means of potentially overcoming these impediments. Here, we present a novel peptide transporter system that increases the efficiency of peptide delivery more than 10 times compared with the previous methods. The transporter, Wr-T, has an enlarged hydrophobic pocket consisting of triple tryptophan-rich domains fused with nine d-enantiomer polyarginines (r9) via Gly-Pro-Gly spacer, which serves to augment delivery of a cargo peptide. Wr-T–mediated transport of p16INK4a functional peptide dramatically inhibits growth of highly aggressive leukemia/lymphomas by up to 80% through restoration of p16 function. The Wr-T system thus represents a highly effective approach to cargo peptide delivery with the potential for substantially developing p16 peptide–based therapy for hematopoietic malignancies.