Calcineurin-dependent lytic granule exocytosis in NK-92 natural killer cells

Cytotoxic T cells (CTLs) and natural killer cells (NKs) both kill virus-infected cells and tumor cells by releasing the cytoxic contents of their lytic granules. We recently demonstrated a role for calcineurin in lytic granule exocytosis in TALL-104 human leukemic CTLs [M.J. Grybko, J.P. Bartnik, G.A. Wurth, A.T. Pores-Fernando, A. Zweifach, Calcineurin activation is only one calcium-dependent step in cytotoxic T lymphocyte granule exocytosis, J. Biol. Chem. 282 (2007) 18009-18017]. However, whether calcineurin plays a similar role in NK lytic granule release is not known. We tested whether calcineurin is involved in lytic granule exocytosis in human leukemic NK-92 cells using immunosuppressive drugs that block calcineurin function and by overexpressing a constitutively active calcineurin fusion protein. Our results indicate that calcineurin does play a role in lytic granule exocytosis in NK-92 cells, and suggest that, as was the case in TALL-104 cells, there are likely to be multiple calcium-dependent steps.     

Toxicological and immunological evaluation of the MHC-non-restricted cytotoxic T cell line TALL-104

 The human MHC-non-restricted cytotoxic T cell line TALL-104 has been shown to display potent antitumor effects in several animal models with spontaneous and induced malignancies. In view of its potential future use in cancer therapy, we investigated the tolerability and target-organ toxicity of these cells in various animal species. The acute toxicity of TALL-104 cell administrations was evaluated in: (a) healthy immunocompetent mice and immunodeficient (SCID) mice bearing human tumors using multiple (up to 15) intraperitoneal (i.p.) injections, and (b) healthy dogs, tumor-bearing dogs, and healthy monkeys using multiple (up to 17) intravenous (i.v.) injections. TALL-104 cells were γ-irradiated (40 Gy) prior to administration to mice and dogs, but administered without irradiation in monkeys. Cell doses ranged from 5×10⁷/kg to 10¹⁰/kg for each injection. All regimens were well tolerated, the main clinical signs observed being transient gastrointestinal effects. Moderate and transient increases in liver transaminase levels were observed in all animal species. Discrete and transient leukocytosis with neutrophilia was also noted in dogs and monkeys after i.v injections of TALL-104 cells. Histological analysis revealed foci of hepatic necrosis with lympho-/mono-/granulocytic infiltration in immunocompetent mice injected i.p. with 5×10⁹ – 10¹⁰ cells/kg. In the same mice, the colon showed an increased number of muciparous cells and alterations in the villi structure: these alterations were completely reversed by 72 h after the last injection, while liver alterations reversed more slowly (1 week). No delayed or chronic toxicity was observed in any of the animals even when non-irradiated TALL-104 cells were administered: both immunocompetent mice and healthy dogs were found to be grossly and histopathologically normal when sacrificed (1 year and 1 month after the last TALL-104 injection respectively). TALL-104 cells did not persist in these hosts. In addition, monkeys showed no molecular signs of TALL-104-cell-induced leukemia in their blood 1 year after the last cell injection. Despite immunosuppression, most of the tumor-bearing dogs as well as the healthy dogs and monkeys developed both humoral and cellular immune responses against TALL-104 cells. The data derived from these preclinical studies suggest that administration of high doses of irradiated TALL-104 cells is well tolerated and would be unlikely to induce severe toxicity if applied in clinical trials to the treatment of patients with refractory cancer. Received: 8 September 1996 / Accepted: 28 January 1997     

Cytotoxic immunotherapy strategies for cancer: mechanisms and clinical development

Traditional therapies for cancer include surgery, chemotherapy, and radiation. Chemotherapy has widespread systemic cytotoxic effects against tumor cells but also affects normal cells. Radiation has more targeted local cytotoxicity but is limited to killing cells in the radiation field. Immunotherapy has the potential for systemic, specific killing of tumor cells. However, if the immune response is specific to a single antigen, tumor evasion can occur by down-regulation of that antigen. An immunotherapy approach that induces polyvalent immunity to autologous tumor antigens can provide a personalized vaccine with less potential for immunologic escape. A cytotoxic immunotherapy strategy creates such a tumor vaccine in situ. Immunogenic tumor cell death provides tumor antigen targets for the adaptive immune response and stimulates innate immunity. Attraction and activation of antigen presenting cells such as dendritic cells is important to process and present tumor antigens to T cells. These include cytotoxic T cells that kill tumor cells and T cells which positively and negatively regulate immunity. Tipping the balance in favor of anti-tumor immunity is an important aspect of an effective strategy. Clinically, immunotherapies may be most effective when combined with standard therapies in a complimentary way. An example is gene-mediated cytotoxic immunotherapy (GMCI) which uses an adenoviral vector, AdV-tk, to deliver a cytotoxic and immunostimulatory gene to tumor cells in vivo in combination with standard therapies creating an immunostimulatory milieu. This approach, studied extensively in animal models and early stage clinical trials, is now entering a definitive Phase 3 trial for prostate cancer.     

Enhanced therapeutic anti-tumor immunity induced by co-administration of 5-fluorouracil and adenovirus expressing CD40 ligand

Bystander immune activation by chemotherapy has recently gained extensive interest and provided support for the clinical use of chemotherapeutic agents in combination with immune enhancers. The CD40 ligand (CD40L; CD154) is a potent regulator of the anti-tumor immune response and recombinant adenovirus (RAd)-mediated CD40L gene therapy has been effective in various cancer models and in man. In this study we have assessed the combined effect of local RAd-CD40L and 5-fluorouracil (5-FU) administration on a syngeneic MB49 mouse bladder tumor model. Whereas MB49 cells implanted into immunocompetent mice responded poorly to RAd-CD40L or 5-FU alone, administration of both agents dramatically decreased tumor growth, increased survival of the mice and induced systemic MB49-specific immunity. This combination treatment was ineffective in athymic nude mice, highlighting an important role for T cell mediated anti-tumor immunity for full efficacy. 5-FU up-regulated the expression of Fas and immunogenic cell death markers in MB49 cells and cytotoxic T lymphocytes from mice receiving RAd-CD40L immunotherapy efficiently lysed 5-FU treated MB49 cells in a Fas ligand-dependent manner. Furthermore, local RAd-CD40L and 5-FU administration induced a shift of myeloid-derived suppressor cell phenotype into a less suppressive population. Collectively, these data suggest that RAd-CD40L gene therapy is a promising adjuvant treatment to 5-FU for the management of bladder cancer.     

Active immunotherapy of L1210 leukemia with neuraminidase-treated,drug-resistant L1210 sublines

Summary The effectiveness of neuraminidase-treated, drug-resistant L1210 sublines in active immunotherapy of L1210 leukemia was evaluated. Optimal conditions for the establishment of in vitro, drug-resistant cells included (a) proper drug concentration, (b) the use of logarithmic-phase cultures in fresh medium, containing 5 or 10% serum, and (c) continual exposure to drug. Active immunotherapy, after tumor burden was reduced with chemotherapy, with neuraminidase-treated cells alone was either effective or deleterious, depending upon the drug-resistant subline used for immunization. The combination of BCG and neuraminidase-treated cells was superior to treatment with chemotherapy only. Optimal response was observed with the use of parental L1210 cells, combined with BCG, in immunotherapy of parental L1210 tumor. The results emphasize that an important prerequisite to successful immunotherapy is that tumor vaccines must elicit immunologic products which are cytotoxic for residual tumor.Submitted in partial fulfillment of the requirements for the Masters of Science Degree, University of Oklahoma     

Effects of lethal irradiation and cyclosporin A treatment on the growth and tumoricidal activity of a T cell clone potentially useful in cancer therapy

The TALL-104 cell line, originally derived from a patient with T cell leukemia, can be maintained indefinitely in culture in the presence of interleukin-2 (IL-2) and is endowed with a highly potent major-histocompatibilitycomplex (MHC)-non-restricted tumoricidal activity both in vitro and in animal models. The present study analyzes in detail the short- and long-term effects of irradiation and cyclosporin A (CsA) treatment on the growth and tumoricidal function of this T cell clone as compared to polyclonal lymphokine-activated killer (LAK) cell preparations from healthy donors. DNA and RNA syntheses by both TALL-104 and LAK cells were irreversibly arrested a few hours after irradiation with 40 Gy. However, 4-h⁵¹Cr-release assays, performed on different days (day 1 to day 7) after irradiation, showed that the cytotoxic efficiency of TALL-104 cells against hematopoietic and solid tumor targets was only modestly reduced, whereas that of LAK cells was severely inhibited. Moreover, the cytotoxic responses to recombinant human IL-2 and IL-12, measured 18 h after irradiation and cytokine addition, were normal in the case of TALL-104 cells but were abolished in the case of LAK cells. Co-culture of IL-2-or IL-12-preactivated TALL-104 cells with a tumor target for 5 days in the absence of cytokines resulted in a lower efficiency of lysis, as compared to the non-irradiated effectors, especially if the initial stimulus was IL-12. These findings suggest the requirement of multiple cytokine stimulation for optimal expression of tumoricidal activity by lethally irradiated TALL-104 cells. CsA, while abrogating TALL-104 cell proliferation at the low dose of 0.5 g/ml, inhibited their cytotoxic function marginally only at high doses (100 g/ml). By contrast, CsA reduced dose-dependently the cytotoxicity of LAK cells starting at very low doses (0.5 g/ml). CsA did not impair the ability of TALL-104 and LAK cells to produce interferon (IFN), tumor necrosis factor (TNF) , and granulocyte/macrophage-colony-stimulatory factor (GM-CSF) in response to IL-2, IL-12, or tumor targets. Irradiation reduced drastically IFN production by LAK, but not TALL-104 cells; release of TNF and GM-CSF by either type of effector was inhibited by 10%–50%, depending on the stimulus. The high resistance of the TALL-104 cells' tumoricidal function to irradiation and immunosuppressive drugs renders this immortal T cell clone a potentially safe and effective reagent for new adoptive-transfer approaches to cancer in MHC-incompatible recipients.     

Polarization of endosomal SNX27 in migrating and tumor-engaged natural killer cells

Polarization is a critical mechanism for the proper functioning of many cell types. For lymphocytes, it is essential in a variety of processes, including migration from the blood to other tissue sites and vice versa. In NK cells and CTLs, the cytotoxic granule delivery mechanism requires polarization for granule movement to the immunological synapse (IS), in killing tumor and virus-infected cells. Recently, it has become apparent that endosomes are also involved in the cytotoxic mechanism. Using an in vitro conjugation approach, we show that in NK-92 cells, endosomal Sorting Nexin 27 (SNX27) polarizes to the IS during tumor cell engagement in a distinct compartment adjacent to the cytotoxic granules. We also show that SNX27 polarizes to the apical membrane, opposite the uropod, during NK cell migration. These previously unreported results indicate that SNX27 is a participant in NK cell polarization, as a mediator or target of the mechanism.     

A novel combination immunotherapy for cancer by IL-13Rα2-targeted DNA vaccine and immunotoxin in murine tumor models

Optimum efficacy of therapeutic cancer vaccines may require combinations that generate effective antitumor immune responses, as well as overcome immune evasion and tolerance mechanisms mediated by progressing tumor. Previous studies showed that IL-13Rα2, a unique tumor-associated Ag, is a promising target for cancer immunotherapy. A targeted cytotoxin composed of IL-13 and mutated Pseudomonas exotoxin induced specific killing of IL-13Rα2(+) tumor cells. When combined with IL-13Rα2 DNA cancer vaccine, surprisingly, it mediated synergistic antitumor effects on tumor growth and metastasis in established murine breast carcinoma and sarcoma tumor models. The mechanism of synergistic activity involved direct killing of tumor cells and cell-mediated immune responses, as well as elimination of myeloid-derived suppressor cells and, consequently, regulatory T cells. These novel results provide a strong rationale for combining immunotoxins with cancer vaccines for the treatment of patients with advanced cancer.     

Topotecan enhances immune clearance of gliomas

Despite aggressive surgery, radiation therapy, and chemotherapy, glioblastoma multiforme (GBM) is refractory to therapy, recurs quickly, and results in a median survival time of only 14 months. The modulation of the apoptotic receptor Fas with cytotoxic agents could potentiate the response to therapy. However, Fas ligand (FasL) is not expressed in the brain and therefore this Fas-inducing cell death mechanism cannot be utilized. Vaccination of patients with gliomas has shown promising responses. In animal studies, brain tumors of vaccinated mice were infiltrated with activated T cells. Since activated immune cells express FasL, we hypothesized that combination of immunotherapy with chemotherapy can activate Fas signaling, which could be responsible for a synergistic or additive effect of the combination. When we treated the human glioma cell line U-87 and GBM tumor cells isolated from patients with TPT, Fas was up regulated. Subsequent administration of soluble Fas ligand (sFasL) to treated cells significantly increased their cell death indicating that these Fas receptors were functional. Similar effect was observed when CD3⁺ T cells were used as a source of the FasL, indicating that the up regulated Fas expression on glioma cells increases their susceptibility to cytotoxic T cell killing. This additive effect was not observed when glioma cells were pre-treated with temozolomide, which was unable to increase Fas expression in tumor. Inhibition of FasL activity with the antagonistic antibody Nok-1 mitigated these effects confirming that these responses were specifically mediated by the Fas-FasL interaction. Furthermore, the CD3⁺ T cells co-cultured with topotecan treated U-87 and autologous GBM tumor cells showed a significant increase in expression in IFN-γ, a key cytokine produced by activated T cells, and accordingly enhanced tumor cytotoxicity. Based on our data we conclude that drugs, such as topotecan, which cause up regulation of Fas on glioma cells can be potentially exploited with immunotherapy to enhance immune clearance of tumors via Fas signaling. Jun Wei and Guillermo DeAngulo are Co-lead authors.     

Immune-based mechanisms of cytotoxic chemotherapy: implications for the design of novel and rationale-based combined treatments against cancer

Conventional anticancer chemotherapy has been historically thought to act through direct killing of tumor cells. This concept stems from the fact that cytotoxic drugs interfere with DNA synthesis and replication. Accumulating evidence, however, indicates that the antitumor activities of chemotherapy also rely on several off-target effects, especially directed to the host immune system, that cooperate for successful tumor eradication. Chemotherapeutic agents stimulate both the innate and adaptive arms of the immune system through several modalities: (i) by promoting specific rearrangements on dying tumor cells, which render them visible to the immune system; (ii) by influencing the homeostasis of the hematopoietic compartment through transient lymphodepletion followed by rebound replenishment of immune cell pools; (iii) by subverting tumor-induced immunosuppressive mechanisms and (iv) by exerting direct or indirect stimulatory effects on immune effectors. Among the indirect ways of immune cell stimulation, some cytotoxic drugs have been shown to induce an immunogenic type of cell death in tumor cells, resulting in the emission of specific signals that trigger phagocytosis of cell debris and promote the maturation of dendritic cells, ultimately resulting in the induction of potent antitumor responses. Here, we provide an extensive overview of the multiple immune-based mechanisms exploited by the most commonly employed cytotoxic drugs, with the final aim of identifying prerequisites for optimal combination with immunotherapy strategies for the development of more effective treatments against cancer.     

NK cells engineered to express a GD2 -specific antigen receptor display built-in ADCC-like activity against tumour cells of neuroectodermal origin

Treatment of high-risk neuroblastoma (NB) represents a major challenge in paediatric oncology. Alternative therapeutic strategies include antibodies targeting the disialoganglioside GD(2) , which is expressed at high levels on NB cells, and infusion of donor-derived natural killer (NK) cells. To combine specific antibody-mediated recognition of NB cells with the potent cytotoxic activity of NK cells, here we generated clonal derivatives of the clinically applicable human NK cell line NK-92 that stably express a GD(2) -specific chimeric antigen receptor (CAR) comprising an anti-GD(2) ch14.18 single chain Fv antibody fusion protein with CD3-ζ chain as a signalling moiety. CAR expression by gene-modified NK cells facilitated effective recognition and elimination of established GD(2) expressing NB cells, which were resistant to parental NK-92. In the case of intrinsically NK-sensitive NB cell lines, we observed markedly increased cell killing activity of retargeted NK-92 cells. Enhanced cell killing was strictly dependent on specific recognition of the target antigen and could be blocked by GD(2) -specific antibody or anti-idiotypic antibody occupying the CAR's cell recognition domain. Importantly, strongly enhanced cytotoxicity of the GD(2) -specific NK cells was also found against primary NB cells and GD(2) expressing tumour cells of other origins, demonstrating the potential clinical utility of the retargeted effector cells.     

Use of the anti-inflammatory cytokine interleukin-11 to reverse HIV-1gp120 repression of a natural killer cell line

Enhancing natural killer (NK) cell activation has been associated with protection from human immunodeficiency virus-1 (HIV-1) infections and slowed onset of immunodeficiency. However, soluble HIV-1 envelope protein, gp120, has been shown to impair NK cell cytokine secretion and cell-mediated cytotoxicity. Here we show that gp120 suppressed IFN-γ production and cytotoxic function of a human NK cell line NK-92MI. We furthermore demonstrated that an anti-inflammatory cytokine interleukin-11 can restore effector functions to repressed NK-92MI cells. These studies support the notion that IL-11 administration may reduce HIV-1-mediated immune activation and exhaustion while achieving elimination of virally-infected cells through restored NK cell function.     

Clonogenic assays measure leukemia stem cell killing not detectable by chromium release and flow cytometric cytotoxicity assays

Background aimsNK-92, a permanent natural killer (NK) cell line, shows cytotoxicity against a variety of tumors and has been tested in a phase I trial. We tested the toxicity of NK-92 and chemotherapy drugs against the stem cell capacity of the acute leukemia cell line, KG1. While the chromium-release assay is the most common method for assessing cytotoxicity of immune effectors, and flow cytometry is increasingly used, the relationship of either assay to clonogenic readouts remains unknown.MethodsKG1 was assessed for stem cell frequency by serial dilution, single-cell sorting and colony growth in methylcellulose. KG1 was sorted into CD34⁺ CD38⁺ and CD34⁺ CD38^? populations and recultured in liquid medium or methylcellulose to determine the proliferative capacity of each fraction. Cytotoxicity of NK-92, daunorubicin and cytarabine against KG1 was measured using the chromium-release assay, flow cytometry and clonogenic assays.ResultsThe culture-initiating cell frequency of whole KG1 was between 1 in 100 to 1000 by serial dilution and single-cell sorting. Although a rare (1–3%) CD34⁺ CD38^? population could be demonstrated in KG1, both fractions had equivalent proliferative capacity. The cumulative flow cytotoxicity assay was more sensitive than the chromium-release assay in detecting target cell killing. At a 10:1 ratio NK-92 eliminated the clonogenic capacity of KG1, which was not predicted by the chromium-release assay.ConclusionsClonogenic assays provide a more sensitive means of assessing the effect of a cytotoxic agent against putative cancer stem cells within cell lines, provided that they grow well in liquid culture medium or methylcellulose.     

Th-1 lymphocytes induce dendritic cell tumor killing activity by an IFN-γ-dependent mechanism

Dendritic cells (DCs) encompass a heterogeneous population of cells capable of orchestrating innate and adaptive immune responses. The ability of DCs to act as professional APCs has been the foundation for the development and use of these cells as vaccines in cancer immunotherapy. DCs are also endowed with the nonconventional property of directly killing tumor cells. The current study investigates the regulation of murine DC cytotoxic function by T lymphocytes. We provide evidence that CD4(+) Th-1, but not Th-2, Th-17 cells, or regulatory T cells, are capable of inducing DC cytotoxic function. IFN-γ was identified as the major factor responsible for Th-1-induced DC tumoricidal activity. Tumor cell killing mediated by Th-1-activated killer DCs was dependent on inducible NO synthase expression and NO production. Importantly, Th-1-activated killer DCs were capable of presenting the acquired Ags from the killed tumor cells to T lymphocytes in vitro or in vivo. These observations offer new possibilities for the application of killer DCs in cancer immunotherapy.     

Galectin-1-mediated biochemical controls of melanoma and glioma aggressive behavior

Gliomas and melanomas are associated with dismal prognosis because of their marked intrinsic resistance to proapoptotic stimuli,such as conventional chemotherapy and radiotherapy,as well as their ability to escape immune cell attacks.In addition,gliomas and melanomas display pronounced neoangiogenesis.Galectin-1 is a hypoxia-sensitive protein,which is abundantly secreted by glioma and melanoma cells,which displays marked proangiogenic effects.It also provides immune tolerogenic environments to melanoma and glioma cells through the killing of activated T cells that attack these tumor cells.Galectin-1 protects glioma and melanoma cells against cytotoxic insults(including chemotherapy and radiotherapy) through a direct role in the unfolded protein response.Altogether,these facts clearly point to galectin-1 as an important target to be combated in gliomas and melanomas in order to:(1) weaken the defenses of these two types of cancers against radiotherapy,chemotherapy and immunotherapy/vaccine therapy;and(2) reinforce antiangiogenic therapies.In the present article,we review the biochemical and molecular biology-related pathways controlled by galectin-1,which are actually beneficial for melanoma and glioma cells,and therefore detrimental for melanoma and glioma patients.     

Cytotoxic dendritic cells generated from cancer patients

Known for years as professional APCs, dendritic cells (DCs) are also endowed with tumoricidal activity. This dual role of DC as killers and messengers may have important implications for tumor immunotherapy. However, the tumoricidal activity of DCs has mainly been investigated in animal models. Cancer cells inhibit antitumor immune responses using numerous mechanisms, including the induction of immunosuppressive/ tolerogenic DCs that have lost their ability to present Ags in an immunogenic manner. In this study, we evaluated the possibility of generating tumor killer DCs from patients with advanced-stage cancers. We demonstrate that human monocyte-derived DCs are endowed with significant cytotoxic activity against tumor cells following activation with LPS. The mechanism of DC-mediated tumor cell killing primarily involves peroxynitrites. This observed cytotoxic activity is restricted to immature DCs. Additionally, after killing, these cytotoxic DCs are able to activate tumor Ag-specific T cells. These observations may open important new perspectives for the use of autologous cytotoxic DCs in cancer immunotherapy strategies.     

胃癌的过继性免疫治疗研究进展

胃癌是目前世界上发病率及致死率较高的恶性肿瘤之一,在东亚地区尤其显著。针对胃癌的治疗手段仍是传统的手术联合化疗、放疗为主,尽管靶向药物治疗提供了新的选择,但其对晚期胃癌的疗效仍然有限。胃癌的免疫治疗作为独特的治疗手段,在近十多年发展较为活跃,特别是过继性免疫治疗手段不断有创新。过继性免疫治疗主要依赖回输具有抗肿瘤活性的细胞,目前回输的细胞由具有非特异性抗肿瘤作用向具有特异性抗肿瘤作用演变,特别是嵌合性抗原T细胞治疗的出现,为进展期胃癌患者提供了有一种潜在的选择。本文对胃癌过继性免疫治疗中采用的不同免疫活性细胞的作用机制、临床应用等进行总结,并针对其不足提出利用基因工程技术增强治疗靶向性、降低免疫逃逸的研究方向。     

Adoptive immunotherapy of a newly induced sarcoma: immunologic characteristics of effector cells

A newly induced syngeneic transplantable sarcoma, MCA 105, was used for studies of the biologic characteristics of fresh noncultured and secondarily in vitro sensitized (IVS) cells with antitumor reactivity. Fresh spleen cells harvested from mice immunized to the MCA 105 tumor by a mixture of viable tumor cells and Corynebacterium parvum exhibited no detectable cytotoxic activity to MCA 105 tumor targets in a 4-hr chromium-release assay, and adoptive transfer of these cells mediated the specific regression of established MCA 105 tumors. Phenotypic analysis of fresh, noncultured immune cells revealed that the therapeutically effective cells expressed both the Lyt-1 and the Lyt-2 T cell differentiation antigens. The therapeutic efficacy of fresh noncultured immune cells was not augmented by the concomitant administration of exogeneous interleukin 2 (IL 2). Secondary IVS of fresh immune cells with irradiated MCA 105 tumor stimulator cells resulted in the generation of tumor-specific cytotoxic effector cells. The generation of cytotoxic effector cells required Lyt-1+, 2+ cytotoxic precursor cells. Effective adoptive immunotherapy with these IVS immune cells, unlike fresh noncultured immune cells, depended on the concomitant administration of IL 2. Furthermore, the generation of therapeutically effective cells did not require the specific stimulation by MCA 105 tumor cells, because cultures of MCA 105 immune spleen cells with FBL-3 lymphoma cells in vitro also contained in vivo functional immune effector cells. These cells, however, possessed no detectable MCA 105 cytotoxic activity in vitro. Although this observation suggests that a noncytotoxic cell population is sufficient to initiate tumor regression in vivo, it does not exclude the possibility that cytolytic cells are generated in vivo after adoptive transfer of these cells. As a whole, our results indicate that secondary IVS functional immune effector cells are characteristically distinct from freshly harvested immune cells.     

The human natural killer cytotoxic cell line NK-92, once armed with a murine CD16 receptor,represents a convenient cellular tool for the screening of mouse mAbs according to their ADCC potential

To take advantage of the large number of well-characterized mouse immunoglobulins (IgGs) for the study of antibody-dependent cell-mediated cytotoxicity (ADCC) in human cells, we armed human cytotoxic lymphocytes with a mouse receptor for the Fc portion of IgG antibodies. The human ΝΚ−92 natural killer cell line was transduced with a mouse receptor gene (mCD16), which was stably expressed on the cell surface (referred to as NK-92^mCD16). When tested against a B-lymphoblastoid cell line (BLCL) coated with mouse anti-CD20 IgG1, IgG2a or IgG2b monoclonal antibodies (mAbs), the newly expressed mouse Fc receptor enabled the NK-92^mCD16 cells to kill the BLCL by ADCC. Next, using the NK-92^mCD16 we compared mouse mAbs directed at B lineage specific CD antigens for their ability to induce ADCC against human Epstein-Barr virus- infected B lymphoblastoid (for anti-CD19, -CD20 and -CD21) or against myeloma (for anti-CD38 and –CD138) target cells. Our results demonstrated that the “NK-92^mCD16 assay” allows convenient and sensitive discrimination of mouse mAbs for their ability to mediate ADCC in a human cellular system. In addition, our results provide examples of dissociation between opsonization and target cell killing through ADCC. These “murinized” human effector cells thus represent a convenient cellular tool for the study of ADCC.     

5-氟尿嘧啶增强HeLa细胞对自然杀伤细胞敏感性研究

目的用5-氟尿嘧啶（5-fluorouracil,5-FU）处理HeLa细胞,检测其NKG2D配体MICA的表达及其对NK92细胞杀伤敏感性的变化。方法不同浓度的5-Fu处理HeLa细胞,在不同时间点用半定量PCR及流式细胞术检测HeLa细胞表面的NKG2D配体MICA在RNA及蛋白水平的表达变化情况,用MTT法检测NKG2D抗体封闭NK92细胞的NKG2D受体前后,NK92细胞对HeLa细胞的杀伤作用。结果不同浓度的5．Fu作用于HeLa细胞后,半定量RT—PCR结果显示MICA表达随5-Fu作用浓度增加逐渐增高。而且40μg／ml5．Fu作用于HeLa细胞后随着作用时间的延长（0、8、16、24h）MICA表达增加,流式细胞术检测结果表明,MICA表达的增加主要依赖于未凋亡细胞的MICA表达。在40μg／ml5-FU作用24h,效靶比为2．5：1,5：1,10：1,20：1时都检测到NK92细胞对HeLa细胞的杀伤增强,杀伤作用可部分被NKG2D抗体抑制。结论5-FU能够上调HeLa细胞表面NKG2D配体MICA的表达,增强HeLa细胞对NK92细胞的敏感性,提示化疗联合NK细胞免疫治疗宫颈癌可产生协同作用,提高治疗效果。