Ataxia–telangiectasia mutated kinase‐mediated upregulation of NKG2D ligands on leukemia cells by resveratrol results in enhanced natural killer cell susceptibility

The powerful activating receptor NKG2D is expressed by natural killer (NK) cells and promotes cytotoxic lysis of cancer cells expressing NKG2D ligands (NKG2D‐Ls). We report the effective induction of NKG2D‐Ls, achieved with the naturally occurring polyphenol resveratrol, in a broad range of leukemia cells. In this study, resveratrol upregulated the NKG2D‐Ls MHC class I chain‐related proteins MICA and MICB, and UL16‐binding proteins ULBP1, ULBP2, and ULBP3 in most of the leukemia cells analyzed. Ligand upregulation induced by resveratrol was impaired by pharmacological and genetic disruption of ataxia–telangiectasia mutated kinase, the main regulator of NKG2D‐L expression. Leukemia cells treated with resveratrol were more susceptible to killing by NK cells than untreated cells, and the enhanced cytotoxicity of NK cells was blocked by treatment of NK cells with anti‐NKG2D mAbs. Interestingly, resveratrol consistently upregulated the NKG2D receptor expression and enhanced NKG2D‐mediated functions in resting NK cells obtained from healthy individuals. Therefore, resveratrol has attractive immunotherapeutic potential.     

Major histocompatibility complex class I-related chain A and UL16-binding protein expression on tumor cell lines of different histotypes: analysis of tumor susceptibility to NKG2D-dependent natural killer cell cytotoxicity

NKG2D, together with NKp46 and NKp30, represents a major triggering receptor involved in the induction of cytotoxicity by both resting and activated human natural killer cells. In this study, we analyzed the expression and the functional relevance of MHC class I-related chain A (MICA) and UL16 binding protein (ULBP), the major cellular ligands for human NKG2D, in human tumor cell lines of different histological origin. We show that MICA and ULBP are frequently coexpressed by carcinoma cell lines, whereas MICA is expressed more frequently than ULBP by melanoma cell lines. Interestingly, the MICA(-) ULBP(+) phenotype was detected in most T cell leukemia cell lines, whereas the MICA(-) ULBP(-) phenotype characterized all acute myeloid leukemia and most B-cell lymphoma cell lines analyzed. These results, together with functional experiments, based on monoclonal antibody-mediated blocking of either NKG2D or its ligands, showed that killing of certain MICA(-) cell tumors is at least in part NKG2D dependent. Indeed, leukemic T cells as well as certain B-cell lymphomas were killed in a NKG2D-dependent fashion upon recognition of ULBP molecules. Moreover, ULBP could induce NKG2D-mediated NK cell triggering also in tumors coexpressing MICA. Our data suggest that the involvement of NKG2D in natural killer cell-mediated cytotoxicity strictly correlates with the expression and the surface density of MICA and ULBP on target cell tumors of different histotypes.     

Proteolytic release of soluble UL16-binding protein 2 from tumor cells

The MHC class I-related ligands of the immunoreceptor NKG2D are frequently expressed by tumor cells and stimulate tumor immunity mediated by CD8 T cells and natural killer (NK) cells. In humans, NKG2D ligands (NKG2DL) are encoded by the MHC-encoded MIC and non-MHC-encoded UL16-binding protein (ULBP) families of proteins. Recently, we and others showed that tumor cells release soluble MICA (sMICA), thereby counteracting NKG2D-mediated tumor immunosurveillance. Here, we now report that ULBP2 molecules are likewise released from tumor cells in a processed soluble form, and that soluble ULBP2 (sULBP2) can be detected in sera of some patients with hematopoietic malignancies. Tumor cell-derived sULBP2 as opposed to cell-bound ULBP2 does not down-regulate NKG2D on NK cells. Unexpectedly, the glycosylphosphatidylinositol-anchored ULBP2 molecules are not released by phospholipases but by the action of metalloproteases. Proteolytic shedding of both NKG2D ligands MICA and ULBP2 by tumor cells was strongly enhanced after phorbol 12-myristate 13-acetate treatment and paralleled by a markedly reduced susceptibility to NKG2D-mediated cytotoxicity. Shedding of MICA and ULBP2 can be blocked by the same inhibitors, suggesting the involvement of related metalloproteases. Thus, our data suggest that reducing NKG2DL surface densities is due to a common cleavage process executed by metalloproteases that promotes escape of tumors from NKG2D-mediated immunosurveillance.     

顺铂对鼻咽癌细胞NKG2D配体表达和NK细胞杀伤活性的增强作用

 目的 研究顺铂(Cisplatin, DDP)作用前后人鼻咽癌细胞CNE2 NKG2D配体和HLA-Ⅰ类分子表达的改变及NK细胞杀伤活性的变化。 方法 MTT法测定DDP对CNE2细胞的50%抑制量（IC₅₀）;以此浓度DDP作用CNE2细胞24h,乳酸脱氢酶释放法检测效靶比20∶1时,NK细胞对DDP作用前后的CNE2细胞的杀伤活性;流式细胞仪检测DDP作用前后的CNE2细胞表面NKG2D配体(MICA/B、ULBP1、ULBP2、 ULBP3)和HLA-Ⅰ类分子表达的变化。 结果 DDP对CNE2细胞的IC₅₀为5mg/L。效靶比20∶1时,NK细胞对5mg/L DDP作用前后的CNE2细胞的杀伤活性分别为 （38.11±1.41）%,（47.71±1.53）%,差异有统计学意义（P＜0.05）,DDP作用后CNE2细胞表面MICA/B、ULBP1、 ULBP3表达显著升高,与作用前相比差异有统计学意义（P＜0.05）。ULBP2、HLA-Ⅰ类分子无明显变化(P＞0.05)。 结论 DDP能提高CNE2细胞NKG2D配体(MICA/B、ULBP1、ULBP3)的表达,从而增强CNE2细胞对NK细胞杀伤的敏感度。     

Tumor suppressive microRNAs miR-34a/c control cancer cell expression of ULBP2, a stress-induced ligand of the natural killer cell receptor NKG2D

Malignant cells express ligands for the natural killer cell immunoreceptor NKG2D, which sensitizes to early recognition and elimination by cytotoxic lymphocytes and provides an innate barrier against tumor development. However, the mechanisms that control NKG2D ligand (NKG2DL) expression in tumor cells remain unknown. We recently identified the NKG2DL ULBP2 as strong prognostic marker in human malignant melanoma. Here, we provide evidence that the tumor-suppressive microRNAs (miRNA) miR-34a and miR-34c control ULBP2 expression. Reporter gene analyses revealed that both miRNAs directly targeted the 3'-untranslated region of ULBP2 mRNA and that levels of miR-34a inversely correlated with expression of ULBP2 surface molecules. Accordingly, treatment of cancer cells with miRNA inhibitors led to upregulation of ULBP2, whereas miR-34 mimics led to downregulation of ULBP2, diminishing tumor cell recognition by NK cells. Treatment with the small molecule inhibitor Nutlin-3a also decreased ULBP2 levels in a p53-dependent manner, which was due to a p53-mediated increase in cellular miR-34 levels. Taken together, our study shows that tumor-suppressive miR-34a and miR-34c act as ULBP2 repressors. These findings also implicate p53 in ULBP2 regulation, emphasizing the role of the specific NKG2DL in tumor immune surveillance.     

Valproic Acid Upregulates NKG2D Ligand Expression through an ERK-dependent Mechanism and Potentially Enhances NK Cell-mediated Lysis of Myeloma

Modulation of the antitumor immune response through the engagement of NKG2D receptors with their ligands (L) on targets represents a promising therapeutic approach against cancer. In this study, we tested the effect of valproic acid (VPA), a histone deacetylase (HDAC) inhibitor, on the expression of NKG2D ligands in myeloma cells. We demonstrated that VPA was able to upregulate both protein and mRNA expression of major histocompatibility complex class I-related chain (MIC) A/B and UL16-binding protein (ULBP) 2 without any significant effect on the expression of ULBP1, ULBP3, and ULBP4 or induction of other natural killer (NK) cell ligands, such as NKp30-L, NKp44-L, and NKp46-L in myeloma cells. A ⁵¹Cr release assay and degranulation assay indicated that the induction of MICA/B and ULBP2 augmented NK cell-mediated lysis of myeloma cells, which was abolished by the addition of a blocking NKG2D antibody. Activation of constitutively phosphorylated extracellular signal-regulated kinase (ERK) by VPA is essential for the up-regulation of MICA/B and ULBP2 expressions. Inhibition of ERK using ERK inhibitor PD98059 decreased both MICA/B and ULBP2 expressions and NK cell cytotoxicity. Furthermore, overexpression of constitutively active ERK in ARK resulted in increased MICA/B and ULBP2 expressions and enhanced NK cell lysis. These data indicate that increased sensitivity of VPA-treated myeloma cells to NK cell lysis is caused by higher NKG2D ligand expression, resulting from more active ERK signaling pathway. Our results provide evidence that targeting ERK signaling pathway may be an additional mechanism supporting the antimyeloma activity of HDAC inhibitors and suggest its possible immunotherapeutic value for myeloma treatment.     

Regulation Roles of MICA and NKG2D in Human Renal Cancer Cells

Objective: Our aim was to investigation the roles of MHC class I chain-related gene A(MICA) and naturalkiller cell group 2D(NKG2D) in human renal cancer cells. Materials and Methods: The expression of membraneMICA (mMICA) on renal cells and NKG2D on NK cells were detected by flow cytometry (FCM); the contentof sMICA were detected by enzyme linked immunosorbent assay (ELISA) and the distribution of mMICA onrenal tumor tissues by immunohistochemistry; the interaction between MICA and NKG2D was observed byantibody closed method. Results: Our results showed that the expression of mMICA in renal cancer tissues wassignificantly higher than in controls, where the soluble MICA was not expressed. Cytotoxic activity of NK cellswas significantly reduced after exposure to NKG2D and MICA antibodies (P<0.05), and serum containing sMICAcan obviously lower the function of NKG2D (P<0.05). Conclusions: The interaction of mMICA and NKG2Dplay important roles in mediation of cytotoxicity of NK cells in RCC. On the other hand, sMICA may mediatetumor immune escape through down- regulated NKG2D expression.     

NKG2D介导NK 细胞对鼻咽癌细胞杀伤作用的体外研究

 目的 探讨鼻咽癌CNE2细胞表面HLA-Ⅰ类分子表型和NKG2D配体的表达情况，进一步了解其对同种异体NK细胞杀伤活性的影响。方法 流式细胞仪检测NKG2D的配体MICA、MICB、ULBP1、ULBP2、ULBP3在K562、CNE2细胞的表达情况。PCR-SSP法分析CNE2细胞HLA-A、B、Cw分型和NK细胞KIR分型。LDH释放法测定5例健康者NK细胞在不同效靶比时对K562、CNE2细胞的杀伤活性，效靶比20：1时观察抗NKG2D配体的单抗对NK细胞杀伤K562、CNE2细胞活性的影响。结果 CNE2细胞表达MICA、MICB、ULBP2，不表达ULBP1、ULBP3。K562细胞表面表达MICA、MICB、ULBP1、ULBP2、ULBP3。5例健康者NK细胞抑制性KIR与CNE2细胞表面的HLA-Ⅰ类分子之间存在错配。效靶比5：1、10：1、20：1、30：1时NK细胞对K562、CNE2细胞的杀伤活性分别为（29．02±0．45）％、（10．50±2．17）％；（44．43±1．36）％、（27．68±1．47）％；（57．82±1．35）％、（36．99±3．13）％：（71．24±2．36）％、（55．00±2．20）％，在各效靶比时NK细胞对K562细胞的杀伤活性较CNE2细胞明显增强（P=0．000）；在效靶比20：1时anti-MICA、anti-MICB、anti-ULBP1、anti—ULBP2、anti-ULBP3可明显抑制NK细胞对K562细胞的杀伤活性，与阻断前相比有显著性差异（P=0．000）；anti—MICA、anti—MICB、anti—ULBP2可明显抑制NK细胞对CNE2细胞的杀伤活性，与阻断前相比有显著性差异（P〈0．01），但anti—ULBP1、anti—ULBP3不能阻断NK细胞对CNE2细胞的杀伤活性。结论 NKG2D配体影响NK细胞对靶细胞的杀伤活性，提高NKG2D配体的表达有可能提高NK细胞的抗肿瘤活性。     

NKG2D配体在13种肿瘤细胞系中的表达及意义

背景与目的:NKG2D及其配体的相互作用在肿瘤免疫监视中起着非常重要的作用。本研究探讨NKG2D配体在13种肿瘤细胞系中的表达及其意义。方法:采用半定量RT-PCR法检测肿瘤细胞系中NKG2D配体的mRNA表达。应用MTT法检测人NK细胞对肿瘤细胞的杀伤活性,免疫组织化学技术和Western blot法检测肿瘤细胞中MHCⅠ类相关蛋白A(MHC classⅠchain-related A)蛋白表达情况。结果:13种肿瘤细胞系表达不同水平的NKG2D配体mRNA。其中Hep2细胞中MICA强阳性表达,HeLa、HepG2、MDA231、HT29、SGC7901、M21、K562、Jurkat细胞MICA表达阳性,而Caski、PG、HL-60和Raji细胞中MICA mRNA阴性。MICA和MICB的表达水平与NK细胞杀伤活性具有高度相关性(r=0.851,P<0.001;r=0.652,P<0.05)。除ULBP3外,其余ULBP成员的表达水平与NK细胞杀伤均无相关性。结论:在6种人NKG2D配体中,MICA的表达水平与肿瘤细胞对NK细胞杀伤的敏感性关系最为密切,肿瘤细胞MICA的表达水平可能决定着机体NK细胞抗肿瘤免疫应答的强弱。     

Downregulation of miR-302c and miR-520c by 1,25(OH)2D3 treatment enhances the susceptibility of tumour cells to natural killer cell-mediated cytotoxicity

Background:

NKG2D recognises several ligands, including polymorphic major histocompatibility complex class I chain-related chain-related proteins A and B (MICA/B) and unique long 16-binding proteins (ULBPs). These ligands are present on cancer cells and are recognised by NKG2D in a cell-structure-sensing manner, triggering natural killer (NK) cell cytotoxicity. However, the mechanisms that control the expression of NKG2D ligands in malignant cells are poorly understood. 1-α,25-Dihydroxyvitamin D3 (1,25(OH)2D3) was recently shown to enhance the susceptibility of melanoma cells to the cytotoxicity of NK cells. However, the function of 1,25(OH)2D3 in other cancers and its potential mechanisms of action remain unknown.

Methods:

The expression levels of miR-302c and miR-520c in Kasumi-1, K562, MCF7 and MDA-MB-231 cells were evaluated using quantitative real-time PCR. The targets of miR-302c and miR-520c were confirmed by luciferase reporter assay. The killing effects of NK92 cells against Kasumi-1, K562, MCF7 and MDA-MB-231 cells were examined using the CytoTox 96 Non-Radioactive Cytotoxicity Assay. The levels of cytokines IFN-γ and granzyme B, which indicate the activation of NK cells, were also measured by enzyme-linked immunosorbent assay.

Results:

Treatment with 1,25(OH)2D3 enhanced the susceptibility of both the haematological tumour cell line Kasumi-1 and solid tumour cell line MDA-MB-231 to NK92 cells. miR-302c and miR-520c expression was induced, and their levels inversely correlated with the levels of NKG2D ligands MICA/B and ULBP2 upon 1,25(OH)2D3 treatment. A luciferase reporter assay revealed that miR-302c and miR-520c directly targeted the 3′-UTRs of MICA/B and ULBP2 and negatively regulated the expression of MIA/B and ULBP2. Moreover, upregulation of miR-302c or miR-520c by transfection of their mimics remarkably reduced the viability of Kasumi-1 cells upon NK cell co-incubation. By contrast, the suppression of the activity of miR-302c or miR-520c by their respective antisense oligonucleotides improved the resistance of Kasumi-1 cells to NK cells.

Conclusion:

1,25(OH)2D3 facilitates the immuno-attack of NK cells against malignant cells partly through downregulation of miR-302c and miR-520c and hence upregulation of the NKG2D ligands MICA/B and ULBP2.     

An Fc‐optimized NKG2D‐immunoglobulin G fusion protein for induction of natural killer cell reactivity against leukemia

Recruitment of Fc‐receptor‐bearing effector cells, such as natural killer (NK) cells, is a feature critical for the therapeutic success of antitumor antibodies and can be improved by the modifications of an antibody's Fc part. The various ligands of the activating immunoreceptor NKG2D, NKG2DL) are selectively expressed on malignant cells including leukemia. We here took advantage of the tumor‐associated expression of NKG2DL for targeting leukemic cells by NKG2D–immunoglobulin G (IgG)1 fusion proteins containing modified Fc parts. Compared to NKG2D–Fc containing a wild‐type Fc part (NKG2D–Fc–WT), our mutants (S239D/I332E and E233P/L234V/L235A/ΔG236/A327G/A330S) displayed highly enhanced (NKG2D–Fc–ADCC) and abrogated (NKG2D–Fc–KO) affinity to the NK cell Fc receptor, respectively. Functional analyses with allogenic as well as autologous NK cells and primary malignant cells of leukemia patients revealed that NKG2D–Fc–KO significantly reduced NK reactivity by blocking immunostimulatory NKG2D–NKG2DL interaction. NKG2D–Fc–WT already enhanced antileukemia reactivity by inducing antibody‐dependent cellular cytotoxicity (ADCC) with NKG2D–Fc–ADCC mediating significantly stronger effects. Parallel application of NKG2D–Fc–ADCC with Rituximab caused additive effects in lymphoid leukemia. In line with the tumor‐associated expression of NKG2DL, no NK cell ADCC against resting healthy blood cells was induced. Thus, NKG2D–Fc–ADCC potently enhances NK antileukemia reactivity despite the inevitable reduction of activating signals upon binding to NKG2DL and may constitute an attractive means for immunotherapy of leukemia.     

Activating NK cell receptor ligands are differentially expressed during progression to cervical cancer

Human papillomavirus-induced cervical carcinomas often show impaired expression of MHC class I molecules resulting in the inability of tumor cells to directly present viral peptides to cytotoxic T lymphocytes. Loss of MHC class I expression combined with the expression of activating NK cell receptor ligands renders tumor cells potentially susceptible to NK cell attack. Thus, in this study, we analyzed the expression of activating NK cell receptor ligands, NK cell accumulation and activation status in situ in normal ectocervical tissue (NCT), cervical intraepithelial neoplasia (CIN) and squamous cervical carcinoma (CxCa). We observed that expression of the DNAM-1 ligand CD155 was frequently upregulated in CxCa, but not in CIN. The NKG2D ligand MICA was upregulated in fewer CxCa biopsies. In contrast, another NKG2D ligand ULBP2 was preferentially expressed in differentiated epithelial cells of NCT. Increased numbers of NK cells were detected in CIN as compared to NCT and CxCa. Expression of activating NK cell receptor ligands combined with loss of MHC class I was not correlated with enhanced NK cell accumulation or activation status. Furthermore, we demonstrate that cervical cancer cell lines are killed by the NK cell line, NKL, in a NKG2D- and DNAM-1-dependent manner in vitro. Since a significant number of CxCa biopsies showed low MHC class I expression combined with high expression of one or more of the tested activating NK cell receptor ligands, we conclude that CxCa might be a promising target for NK cell-based adoptive immunotherapy.     

Inhibition of mitogen‐activated protein kinase pathway can induce upregulation of human leukocyte antigen class I without PD‐L1‐upregulation in contrast to interferon‐γ treatment

Recently, we reported that human leukocyte antigen (HLA) class I expression is predominantly regulated by the mitogen‐activated protein kinase (MAPK) pathway as one of the oncogenic regulations of HLA class I expression. In the present study, we examined mechanisms of how HLA class I and PD‐L1 are regulated by MAPK inhibitors and interferon‐γ (IFN‐γ). Furthermore, we evaluated the expression of major signal transduction molecules by Western blot and anti‐tumor CTL activity by a cytotoxic assay when HLA class I and PD‐L1 were modulated by MAPK inhibitors and/or IFN‐γ. As a result, we confirmed, as a more general phenomenon, that the inhibition of MAPK could upregulate HLA class I expression in a panel of human solid tumors (n = 26). Of note, we showed that MAPK inhibitors act on the upregulation of HLA class I expression through a different pathway from IFN‐γ; there was an additive effect in the upregulation of HLA class I when treated with the combination of MAPK inhibitors and IFN‐γ, and there was no overlapping activation of JAK2/STAT1 and Erk1/2 molecules when treated with either IFN‐γ or MAPK inhibitors. Furthermore, we showed that IFN‐γ–treatment impaired the tumor‐specific CTL activity due to the upregulation of PD‐L1 in spite of the upregulation of HLA class I, while MAPK inhibitors can augment the tumor‐specific CTL activity due to the upregulated HLA class I without PD‐L1 alterations. In conclusion, in addition to the original anti‐proliferative activity, MAPK inhibitors may work toward the enhancement of T‐cell‐mediated anti‐tumor immunity through the upregulation of HLA class I without the upregulation of PD‐L1.     

Overexpression of natural killer group 2 member D ligands predicts favorable prognosis in cholangiocarcinoma

The natural killer group 2 member D (NKG2D) receptor and its ligands are important mediators of immune responses to tumors. NKG2D ligands are overexpressed in several malignant tumor types; however, the prognostic value of these ligands is unclear. Here, we aimed to elucidate the role of NKG2D ligands in extrahepatic cholangiocarcinoma (EHCC). We therefore investigated the expression of the NKG2D receptor and its ligands MHC class I chain‐related proteins A and B (MICA/B), unique long 16 binding protein (ULBP) 1, and ULBP2/5/6 in resected specimens from 82 patients with EHCC. All NKG2D ligands were highly expressed in EHCC. High expression of MICA/B or ULBP2/5/6 correlated with overall and disease‐free survival. In contrast, high expression of ULBP1 was significantly associated with improved overall survival, but not disease‐free survival. Concurrent high expression of multiple NKG2D ligands revealed significantly better overall and disease‐free survival than that observed with the overexpression of any one NKG2D ligand. Co‐expression of multiple NKG2D ligands was an independent prognostic indicator of improved survival. Furthermore, co‐overexpression of multiple NKG2D ligands was significantly correlated with high expression of the NKG2D receptor. Inhibiting interactions between multiple NKG2D ligands and the NKG2D receptor might be a promising approach for controlling cancer progression and improving patient prognosis in EHCC.     

MICA/NKG2D-mediated immunogene therapy of experimental gliomas

The failure of conventional cancer therapy renders glioblastoma an attractive target for immunotherapy. Tumor cells expressing ligands of the activating immunoreceptor NKG2D stimulate tumor immunity mediated by natural killer (NK), gammadelta T, and CD8(+) T cells. We report that human glioma cells express the NKG2D ligands MICA, MICB, and members of the UL16-binding protein family constitutively. However, glioma cells resist NK cell cytolysis because of high MHC class I antigen expression. Plasmid-mediated or adenovirus-mediated overexpression of MICA in glioma cells enhances their sensitivity to NK and T-cell responses in vitro and markedly delays the growth of s.c. and intracerebral LN-229 human glioma cell xenografts in nude mice and of SMA-560 gliomas in syngeneic VMDk mice. Glioma cells forming progressive tumors after implantation of stably MICA-transfected human LN-229 cells lost MICA expression, indicating a strong selection against MICA expression in vivo. Rejection of MICA-expressing SMA-560 cells in VMDk mice resulted in protective immunity to a subsequent challenge with wild-type tumor cells. Finally, the growth of syngeneic intracerebral SMA-560 tumors is inhibited by peripheral vaccination with adenovirus-mediated, MICA-infected irradiated tumor cells, and vaccination results in immune cell activation in the NK and T-cell compartments in vivo. These data commend MICA immunogene therapy as a novel experimental treatment for human malignant gliomas.     

耐地塞米松B细胞淋巴瘤细胞逃逸同种异体NK细胞的杀伤及其机制

目的:观察地塞米松耐药的人B细胞淋巴瘤细胞系对NK细胞杀伤敏感性的变化,并探讨其作用机制。方法:20μg/ml地塞米松(dexamethasone,DXM)诱导B细胞淋巴瘤细胞系SU-DHL-4(简称SU细胞)发生耐药,建立多药耐药细胞系SU/DXM。流式细胞术分选健康人外周血NK细胞,流式细胞术检测效靶比20∶1时,NK细胞对SU和SU/DXM细胞的杀伤效应。实时定量PCR检测SU和SU/DXM细胞表面NK细胞活化性受体(soluble NK group 2 member D,NKG2D)配体基因[可溶性MHCⅠ类分子相关A/B(MHC classⅠchain-related molecules A/B,MICA/B)及人UL16结合蛋白(UL16 binding protein,ULBP)1、2、3]的表达。结果:成功建立多药耐药细胞系SU/DXM。与SU细胞相比,SU/DXM细胞对NK细胞杀伤的敏感性明显下降[SU细胞为(11.38±3.51)%,SU/DXM细胞为(3.57±4.22)%,P<0.05],细胞表面NKG2D配体基因MICA、MICB、ULBP2 mRNA表达量降低(SU细胞分别为1.014±0.121、1.009±0.092、0.993±0.108,SU/DXM细胞分别为0.017±0.006、0.682±0.063、0.773±0.066,P<0.05或P<0.01)。结论:地塞米松能诱导B细胞淋巴瘤SU细胞发生多药耐药,多药耐药SU/DXM细胞能够抵抗NK细胞的杀伤,其机制可能与NKG2D配体基因表达量下降有关。