Enhancing T Cell Chemotaxis and Infiltration in Glioblastoma
NK cells impede glioblastoma virotherapy through NKp30 and NKp46 natural cytotoxicity receptors
11
ARTICLES NATURE MEDICINE VOLUME 18 | NUMBER 12 | DECEMBER 2012 1827 The current standard of therapy for glioblastoma is palliative 1 . Attempts to improve survival involve various new approaches, including oncolytic virotherapy 2 . In virotherapy, naturally occur- ring or genetically engineered viruses selectively replicate in and lyse tumor cells while engendering an immune response to both virally infected and uninfected tumors. One such virus is oHSV, which is genetically modified to replicate in and lyse tumor cells through multiple rounds of viral replication 2 . To date, oHSV injected into human glioblastomas has been well tolerated, but efforts to dem- onstrate efficacy in early phase trials have been disappointing 3 . We have hypothesized that the host immune response to oHSV therapy for glioblastoma is a barrier to achieving clinical success 4 . This hypothesis is based on mouse and rat studies in which transient depletion of phagocytic macrophage populations or pharmacologic suppression of immunity improved the effect of oHSV 5–7 . However, the hypothesis that innate immunity is deleterious to virotherapy 5–11 runs counter to the argument that immune responses are benefi- cial to antitumor efficacy. In fact, the host immune response after oHSV administration in vivo has been shown to provoke an anti- tumor immune response against oHSV-infected cells and unin- fected bystander tumor cells 12–15 . Resolution of these apparently discordant views 16,17 is important, as one would attempt to either evade or increase immunity to improve efficacy. In this context, NK cells are the perfect foe or friend of virotherapy. NK cells are rapidly recruited to the site of viral infection and mediate viral clearance, thus making them a foe 11 . However, they also possess tumor-clearing properties whereby stimulating NK cell infiltration by oHSV could facilitate antitumor efficacy 18–22 . In the context of oHSV therapy, the antiviral compared to the antitumor role of NK cells has not been defined. The mechanisms by which NK cells eradi- cate virally infected cells are currently under intense investigation 23 . Human NK cells express a variety of receptors, including the NCRs NKp30, NKp44 and NKp46 that mediate NK cell cytotoxic functions. However, the key receptor-ligand interactions that coordinate the NK cell cytotoxic functions are not known. In this report, we show that oHSV infection of experimental glioblastoma is characterized by rapid recruitment to the brain of NK cells with an activated phenotype. This response does not facili- tate antitumor effects; rather, it leads to premature viral clearance and limits oHSV anticancer efficacy. In vitro, NK cell–mediated killing was primarily dependent on NKp30 and NKp46, which recog- nize ligands upregulated in oHSV-infected human glioblastoma cell 1 Medical Scientist Training Program, Ohio State University Medical Center and James Cancer Hospital and Solove Research Institute, Columbus, Ohio, USA. 2 Dardinger Laboratory for Neuro-oncology and Neurosciences, Department of Neurological Surgery, Ohio State University Medical Center and James Cancer Hospital and Solove Research Institute, Columbus, Ohio, USA. 3 Division of Hematology, Ohio State University Medical Center and James Cancer Hospital and Solove Research Institute, Columbus, Ohio, USA. 4 Comprehensive Cancer Center, Ohio State University, Ohio State University Medical Center and James Cancer Hospital and Solove Research Institute, Columbus, Ohio, USA. 5 Center for Biostatistics, Ohio State University Medical Center and James Cancer Hospital and Solove Research Institute, Columbus, Ohio, USA. 6 Centre d’Immunologie de Marseille-Luminy, Université de la Méditerranée, INSERM, U631, Marseille, France. 7 The Lautenberg Center for General and Tumor Immunology, Institute for Medical Research Israel-Canada, Hebrew University-Hadassah Medical School, Jerusalem, Israel. 8 Dipartimento di Medicina Sperimentale e Centro di Eccellenza per le Ricerche Biomediche, Università degli Studi di Genova, Genova, Italy. 9 Department of Neurosurgery, Brigham and Women’s Hospital/Dana-Farber Cancer Institute/Harvard Medical School, Boston, Massachusetts, USA. 10 These authors contributed equally to this work. Correspondence should be addressed to E.A.C. ([email protected]) or M.A.C. ([email protected]). Received 25 June; accepted 16 October; published online 25 November 2012; corrected after print 7 October 2013; doi:10.1038/nm.3013 NK cells impede glioblastoma virotherapy through NKp30 and NKp46 natural cytotoxicity receptors Christopher A Alvarez-Breckenridge 1,2,10 , Jianhua Yu 3,4,10 , Richard Price 1,2 , Jeffrey Wojton 2 , Jason Pradarelli 2 , Hsiaoyin Mao 4 , Min Wei 4 , Yan Wang 2 , Shun He 4 , Jayson Hardcastle 2 , Soledad A Fernandez 4,5 , Balveen Kaur 2,4 , Sean E Lawler 2 , Eric Vivier 6 , Ofer Mandelboim 7 , Alessandro Moretta 8 , Michael A Caligiuri 3,4 & E Antonio Chiocca 2,4,9 The role of the immune response to oncolytic Herpes simplex viral (oHSV) therapy for glioblastoma is controversial because it might enhance or inhibit efficacy. We found that within hours of oHSV infection of glioblastomas in mice, activated natural killer (NK) cells are recruited to the site of infection. This response substantially diminished the efficacy of glioblastoma virotherapy. oHSV-activated NK cells coordinated macrophage and microglia activation within tumors. In vitro, human NK cells preferentially lysed oHSV-infected human glioblastoma cell lines. This enhanced killing depended on the NK cell natural cytotoxicity receptors (NCRs) NKp30 and NKp46, whose ligands are upregulated in oHSV-infected glioblastoma cells. We found that HSV titers and oHSV efficacy are increased in Ncr1 –/– mice and a Ncr1 –/– NK cell adoptive transfer model of glioma, respectively. These results demonstrate that glioblastoma virotherapy is limited partially by an antiviral NK cell response involving specific NCRs, uncovering new potential targets to enhance cancer virotherapy. npg © 2013 Nature America, Inc. All rights reserved.
Transcript of NK cells impede glioblastoma virotherapy through NKp30 and NKp46 natural cytotoxicity receptors
a r t i c l e s
nature medicine VOLUME 18 | NUMBER 12 | DECEMBER 2012 1827
The current standard of therapy for glioblastoma is palliative1. Attempts to improve survival involve various new approaches, including oncolytic virotherapy2. In virotherapy, naturally occur-ring or genetically engineered viruses selectively replicate in and lyse tumor cells while engendering an immune response to both virally infected and uninfected tumors. One such virus is oHSV, which is genetically modified to replicate in and lyse tumor cells through multiple rounds of viral replication2. To date, oHSV injected into human glioblastomas has been well tolerated, but efforts to dem-onstrate efficacy in early phase trials have been disappointing3. We have hypothesized that the host immune response to oHSV therapy for glioblastoma is a barrier to achieving clinical success4. This hypothesis is based on mouse and rat studies in which transient depletion of phagocytic macrophage populations or pharmacologic suppression of immunity improved the effect of oHSV5–7. However, the hypothesis that innate immunity is deleterious to virotherapy5–11 runs counter to the argument that immune responses are benefi-cial to antitumor efficacy. In fact, the host immune response after oHSV administration in vivo has been shown to provoke an anti-tumor immune response against oHSV-infected cells and unin-fected bystander tumor cells12–15. Resolution of these apparently
discordant views16,17 is important, as one would attempt to either evade or increase immunity to improve efficacy.
In this context, NK cells are the perfect foe or friend of virotherapy. NK cells are rapidly recruited to the site of viral infection and mediate viral clearance, thus making them a foe11. However, they also possess tumor-clearing properties whereby stimulating NK cell infiltration by oHSV could facilitate antitumor efficacy18–22. In the context of oHSV therapy, the antiviral compared to the antitumor role of NK cells has not been defined. The mechanisms by which NK cells eradi-cate virally infected cells are currently under intense investigation23. Human NK cells express a variety of receptors, including the NCRs NKp30, NKp44 and NKp46 that mediate NK cell cytotoxic functions. However, the key receptor-ligand interactions that coordinate the NK cell cytotoxic functions are not known.
In this report, we show that oHSV infection of experimental glioblastoma is characterized by rapid recruitment to the brain of NK cells with an activated phenotype. This response does not facili-tate antitumor effects; rather, it leads to premature viral clearance and limits oHSV anticancer efficacy. In vitro, NK cell–mediated killing was primarily dependent on NKp30 and NKp46, which recog-nize ligands upregulated in oHSV-infected human glioblastoma cell
1Medical Scientist Training Program, Ohio State University Medical Center and James Cancer Hospital and Solove Research Institute, Columbus, Ohio, USA. 2Dardinger Laboratory for Neuro-oncology and Neurosciences, Department of Neurological Surgery, Ohio State University Medical Center and James Cancer Hospital and Solove Research Institute, Columbus, Ohio, USA. 3Division of Hematology, Ohio State University Medical Center and James Cancer Hospital and Solove Research Institute, Columbus, Ohio, USA. 4Comprehensive Cancer Center, Ohio State University, Ohio State University Medical Center and James Cancer Hospital and Solove Research Institute, Columbus, Ohio, USA. 5Center for Biostatistics, Ohio State University Medical Center and James Cancer Hospital and Solove Research Institute, Columbus, Ohio, USA. 6Centre d’Immunologie de Marseille-Luminy, Université de la Méditerranée, INSERM, U631, Marseille, France. 7The Lautenberg Center for General and Tumor Immunology, Institute for Medical Research Israel-Canada, Hebrew University-Hadassah Medical School, Jerusalem, Israel. 8Dipartimento di Medicina Sperimentale e Centro di Eccellenza per le Ricerche Biomediche, Università degli Studi di Genova, Genova, Italy. 9Department of Neurosurgery, Brigham and Women’s Hospital/Dana-Farber Cancer Institute/Harvard Medical School, Boston, Massachusetts, USA. 10These authors contributed equally to this work. Correspondence should be addressed to E.A.C. ([email protected]) or M.A.C. ([email protected]).
Received 25 June; accepted 16 October; published online 25 November 2012; corrected after print 7 October 2013; doi:10.1038/nm.3013
NK cells impede glioblastoma virotherapy through NKp30 and NKp46 natural cytotoxicity receptorsChristopher A Alvarez-Breckenridge1,2,10, Jianhua Yu3,4,10, Richard Price1,2, Jeffrey Wojton2, Jason Pradarelli2, Hsiaoyin Mao4, Min Wei4, Yan Wang2, Shun He4, Jayson Hardcastle2, Soledad A Fernandez4,5, Balveen Kaur2,4, Sean E Lawler2, Eric Vivier6, Ofer Mandelboim7, Alessandro Moretta8, Michael A Caligiuri3,4 & E Antonio Chiocca2,4,9
The role of the immune response to oncolytic Herpes simplex viral (oHSV) therapy for glioblastoma is controversial because it might enhance or inhibit efficacy. We found that within hours of oHSV infection of glioblastomas in mice, activated natural killer (NK) cells are recruited to the site of infection. This response substantially diminished the efficacy of glioblastoma virotherapy. oHSV-activated NK cells coordinated macrophage and microglia activation within tumors. In vitro, human NK cells preferentially lysed oHSV-infected human glioblastoma cell lines. This enhanced killing depended on the NK cell natural cytotoxicity receptors (NCRs) NKp30 and NKp46, whose ligands are upregulated in oHSV-infected glioblastoma cells. We found that HSV titers and oHSV efficacy are increased in Ncr1–/– mice and a Ncr1–/– NK cell adoptive transfer model of glioma, respectively. These results demonstrate that glioblastoma virotherapy is limited partially by an antiviral NK cell response involving specific NCRs, uncovering new potential targets to enhance cancer virotherapy.
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lines. These findings were supported by studies in mice lacking NKp46 (Ncr1−/− mice) that showed the antiviral role of NKp46. These results demonstrate that the initial in vivo antiviral NK cell response to oHSV is detrimental in mouse models and suggests NKp30 and NKp46 as potential clinical targets to improve virotherapy.
RESULTSoHSV induces rapid NK cell recruitment and activationWe first investigated whether there was an increase in NK cell infil-tration after administering the oHSV, rQNestin34.5 (ref. 24) into orthotopic human glioblastoma (U87dEGFR) xenografts and syn-geneic mouse glioblastoma (KR158dEGFR). rQNestin34.5 selec-tively replicates based on the mutational insertion of GFP into the Herpes simplex virus 1 (HSV-1) ICP6 locus, providing selectivity
for p16−/− cells25, and on transcriptional regulation of the HSV-1 gene product ICP34.5 by the nestin promoter, providing selectivity for nestin-positive glioblastomas24. We found a significant increase in the total number of NK cells 2 h after oHSV infection (Fig. 1a). Compared to mice treated with HBSS or heat-inactivated oHSV, NK cell recruitment required viral replication and increased for up to 72 h in mice treated with rQNestin34.5 (Fig. 1b,c and Supplementary Fig. 1a–c). We confirmed the presence of NK cells in the brains of rQNestin34.5-treated mice that were perfused before mononuclear cell isolation (Supplementary Fig. 1b). NK cell recruitment also occurred after intracranial administration of wild-type (WT) HSV-1 (Supplementary Fig. 1b). These results thus showed that active oHSV replication elicited a rapid elevation in the number of NK cells into xenograft and syngeneic mouse glioblastomas.
Figure 1 oHSV administration induces NK cell recruitment to the tumor-bearing brain. (a) Fluorescence-activated cell sorting (FACS) quantification of NK cells in the brains of athymic mice bearing U87dEGFR tumors 2 h after inoculation with rQNestin34.5 or vehicle (veh.) (n = 3 mice per group). (b) FACS quantification of the total number of NK cells in tumor-bearing hemispheres at 6, 24 or 72 h after inoculation with rQNestin34.5, heat-inactivated oHSV or vehicle in athymic mice bearing U87dEGFR tumors (n = 4–5 mice per group). (c) NK cell quantification in the brains of mice after rQNestin34.5 injection into intracranial U87dEGFR xenografts or WT HSV-1 in the brains of mice with no tumor, in tumor-bearing mice treated with vehicle or in untreated tumor-bearing mice (n = 3–5 mice per group). *P < 0.05, ***P < 0.001; Student’s t test was used to calculate statistical significance in a and c, and two-way analysis of variance (ANOVA) and pairwise comparisons were used in b. Error bars, s.d.
a b
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71%MFI: 211
51%MFI: 31
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Figure 2 NK cells are activated after oHSV therapy. (a) FACS assessment of the mean fluorescent intensities (MFI) and percentage of NK cells (CD3−DX5+) expressing various NK cell activation markers (CD69, CD62L, NKG2D, CD27 or Ly49d) 72 h after intracranial inoculation of rQNestin34.5 or vehicle (veh.) into athymic mice bearing U87dEGFR human glioblastomas. Additionally, FACS quantification of the same markers is shown in KR158dEGFR syngeneic tumors and after WT HSV-1 infection in the brains of athymic mice lacking glioblastoma (glioblastoma free). Supplementary Table 1 lists the average and ranges summarizing the total number of experiments. (b,c) FACS analysis of the NK cell markers CD11bhighCD27high (cytotoxic) or CD11blowCD27high (immature) compared to CD11bhighCD27low (senescent) 72 h after rQNestin34.5 or vehicle inoculation in both xenograft and syngeneic tumor models, in addition to WT HSV-1 infection in the brains of athymic mice lacking glioblastoma. These findings are presented as representative dot plots (b), where the percentage of cells in each quadrant is indicated by a red number and as a fold increase in the expression of each NK cell population compared to vehicle-treated mice (c). (n = 4–6 mice per group). **P < 0.01, ***P < 0.001 by two-way ANOVA. Error bars, s.d. (d) Percentage positivity and fold increase (in parentheses) of the degranulation marker CD107a in the CD11bhighCD27high and CD11bhighCD27low NK cell subsets 72 h after rQNestin34.5 or vehicle treatment of mice with glioblastoma xenografts.
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We next characterized the activation status of recruited NK cells by evaluating the expression of 11 different surface antigens. oHSV admin-istration induced a unique phenotype in NK cells recruited to the site of infection (Fig. 2a and Supplementary Table 1a) that was not present in peripheral NK cells (Supplementary Fig. 2). The expression levels of CD27 and CD11b denote three distinct NK cell functional subpopula-tions26: immature CD11blowCD27high, cytotoxic CD11bhighCD27high and senescent CD11bhighCD27low. Although NK cells recruited to tumors in vehicle-treated mice were mostly CD11bhighCD27low, oHSV administra-tion resulted in recruitment of CD11bhighCD27high or CD11blowCD27high NK cells (Fig. 2b,c and Supplementary Table 1b). oHSV infection induced a threefold and a sevenfold increase in the expression of the degranula-tion marker CD107a in CD11bhighCD27low and CD11bhighCD27high NK cells, respectively (Fig. 2d). Therefore, oHSV enhances the recruitment of distinct NK cell subsets expressing cytotoxic NK cell markers.
Macrophage activation occurs in a NK cell–dependent mannerBecause NK cells are thought to coordinate macrophage activa-tion27, we examined whether recruited NK cells orchestrate this response in the context of virotherapy. oHSV treatment reduced the percentage of CD115+CD45lowCD11b+ cells (microglia) and con-comitantly increased both CD115+CD45highCD11b+ mononuclear (macrophages) and CD115+CD45highCD11blow lymphocyte popula-tions compared to HBSS treatment (Fig. 3a). We further found that CD115+CD45highCD11b+ cells showed markedly enhanced expres-sion of macrophage activation markers. However, NK cell depletion28 attenuated this response (Fig. 3b and Supplementary Fig. 3a). To assess the retention of macrophages and microglia after NK cell depletion, we gated on CD115, a marker for monocyte-derived cells29. We then quantified the total numbers of CD115+CD45lowCD11b+ and CD115+CD45highCD11b+ cells. Notably, NK cell depletion with
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Figure 3 NK cells mediate macrophage and microglia activation after oHSV therapy. (a) FACS of time-dependent changes in CD115+CD45highCD11b+, CD115+CD45high CD11blow and CD115+CD45lowCD11b+ cells in glioblastomas after rQNestin34.5 treatment (n = 4–6 mice per group). (b) FACS of CD115+CD45highCD11b+ cells expressing macrophage activation markers (MHC-II, Ly-6C or CD86) 72 h after vehicle (veh.) or rQNestin34.5 infection as a function of NK cell presence (n = 4 mice per group). (c) FACS of CD115+CD45lowCD11b+ or CD115+CD45high CD11b+ cells 72 h after rQNestin34.5 inoculation as a function of NK cell presence. Asialo, antibodies to asialo-GM1. (d) Nos2 and Tnf expression in tumor-bearing hemispheres 72 h after vehicle or rQNestin34.5 inoculation in the presence or absence of NK cells (n = 4–5 mice per group). (e) Nos2 and Tnf expression as a function of NK cell depletion in FACS-sorted CD115+CD45lowCD11b+ or CD115+CD45highCD11b+ cells 72 h after rQNestin34.5 inoculation of U87dEGFR tumors. (f,g) Intracellular protein staining with FACS quantification (f) and Nos2 mRNA expression (g) in intracranial KR158dEGFR tumors 72 h after rQNestin34.5 inoculation as a function of NK cell presence and Ifng production. (h) FACS of intracellular Tnf 72 h after rQNestin34.5 treatment of U87dEGFR tumors as a function of NK cell presence. (i,j) Cxcl9, Cxcl10 and Cxcl11 expression 72 h after rQNestin34.5 treatment of xenograft (i) and syngeneic (j) tumors as a function of NK cell presence (n = 3–5 mice per group). The dependence on the expression of Ifng within the KR158dEGFR tumor was also assessed in j. *P < 0.05, **P < 0.01, ***P < 0.001 by Student’s t test. Error bars, s.d.
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antibodies to either asialo-GM1 or TMβ1 before oHSV inocula-tion did not alter the total number of CD115+CD45lowCD11b+ and CD115+CD45highCD11b+ cells in the tumor compared to mock-depleted mice (Fig. 3c). We further confirmed an equal number of intracranial macrophages and microglia after NK cell depletion by staining for CD45+F4/80+Gr1+ cells (Supplementary Fig. 3b). Therefore, NK cell depletion attenuated the expression of macro-phage and microglia activation markers, rather than reducing their cell numbers, in tumors in response to oHSV infection.
We then analyzed markers of macrophage and microglia activation. oHSV infection of glioblastoma in vivo significantly increased the gene expression and protein production of nitric oxide synthase 2 (Nos2) and tumor necrosis factor (Tnf), whereas NK cell depletion attenuated this response (Fig. 3d–h). By adoptively transferring WT NK cells into Ifng−/− mice, we demonstrated that Nos2 induction depended on NK cell–derived Ifng gene expression (Fig. 3f,g and Supplementary Fig. 3c). In addition, expression of the genes encoding the interferon γ (Ifng)-inducible chemokines (IIC) Cxcl9, Cxcl10 and Cxcl11 signifi-cantly increased after oHSV therapy (Fig. 3i,j). This increase did not occur if NK cells were depleted or in Ifng−/− mice (Fig. 3i,j). Consistent with the notion that IIC expression is associated with macrophage and microglia activation but is not necessarily derived from these cells, IIC expression was not significantly altered within these cell popula-tions after NK cell depletion (Supplementary Fig. 3d). Together, these results show that virotherapy results in NK cell–mediated macrophage and microglia activation, which has been reported to correlate, in general, with both anticancer and antiviral properties30.
Depletion of NK cells in vivo enhances efficacy of oHSVThe observed NK-cell and macrophage activation could potentially hinder virotherapy by eliminating oHSVs. After confirming our ability
to deplete NK cells in glioblastoma-bearing mice (Supplementary Fig. 4a–c), we found that NK cell depletion led to significantly elevated titers of rQNestin34.5 compared to NK-replete mice (Fig. 4a). Notably, NK cell depletion (by antibodies to either asialo-GM1 or TMβ1) significantly increased the survival of mice bearing orthotopic glioblastoma xenografts treated with oHSV (Fig. 4b). We recapitu-lated these findings by depleting NK cells with either antibodies to TMβ1 or NK1.1 in a mouse syngeneic model31 (Fig. 4c,d).
To assess the inflammatory response induced by oHSV, we used a mouse inflammatory gene expression array. We found significantly induced gene expression in 30 out of 84 genes in tumors treated with oHSV. This included over 100-fold induction of the expression of Cxcl9, Cxcl10, Cxcl11, Ccl2 and Ccl7. NK cell depletion reduced the induction of all 30 genes by oHSV (Fig. 4e,f and Supplementary Table 2). These results indicate that NK cell recruitment after oHSV infection of gliomas leads to a significant increase in inflammatory gene expression that can be reduced almost back to baseline with NK cell depletion.
NKp30 and NKp46 are mediators of oHSV viral clearanceAs interleukin-15 (IL-15) was upregulated by oHSV in tumors (Supplementary Fig. 5a), we assessed the cytotoxicity of IL-15–activated human NK cells. IL-15–activated human NK cells showed enhanced toxicity against oHSV-infected human glioblastoma cells compared to uninfected glioblastoma cells (Fig. 5a). Unstimulated NK cells were also more cytotoxic against oHSV-infected compared to uninfected glioblastoma cells, albeit to a reduced degree than the cytotoxicity shown by IL-15–activated NK cells against infected tumor cells (Supplementary Fig. 5b). IL-15–activated mouse NK cells also preferentially killed oHSV-infected glioblastoma cells (Fig. 5b). Notably, this antiviral response was unique to NK cells, as cytotoxic
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Figure 4 NK cell depletion enhances oHSV efficacy. (a) Viral titers as a function of NK cell depletion 72 h after inoculation with rQNestin34.5 or rQNestin34.5 plus antibodies to asialo-GM1 (asialo) into athymic mice bearing U87dEGFR glioma (n = 4–5 mice per group). *P < 0.05 by Student’s t test. Error bars, s.d. (b) Kaplan-Meier survival curves for athymic mice bearing U87dEGFR tumors treated with rQNestin34.5 or vehicle (veh.) and antibody to either asialo-GM1 or TMβ1 as a function of NK cell depletion (n = 5 mice per group). The P values shown indicate comparison of U87dEGFR + rQNestin34.5 to U87dEGFR + rQNestin34.5 + asialo or U87dEGFR + rQNestin34.5 + TMβ1. (c,d) Kaplan-Meier survival curves for the syngeneic 4C8 mouse glioblastoma model in which NK cell depletion was carried out with TMβ1-specific antibody (c) or NK1.1-specific antibody (d) before rQNestin34.5 or vehicle inoculation into brain tumors (n = 8–14 mice per group). For c, the P value shown indicates the comparison of 4C8 + rQNestin34.5 to 4C8 + rQNestin34.5 + TMβ1; for d, the P value shown indicates the comparison of 4C8 + rQNestin34.5 to 4C8 + rQNestin34.5 + NK1.1. (e,f) Differences in gene expression of 84 mouse inflammatory genes in the presence (e) or absence (f) of NK cells 72 h after intracranial inoculation of rQNestin34.5 into athymic mice bearing U87dEGFR cells (n = 4–5 mice per group). Each row and column is represented by a unique number denoting a different transcript. The identity of the transcript after tumor treatment is listed in Supplementary Table 2a (for vehicle compared to rQNestin34.5 treatment) and b (for antibody to asialo-GM1 plus rQNestin34.5 compared to rQNestin34.5 treatment).
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T lymphocytes (CTLs) from human donors were unable to recapitulate this cytotoxicity profile (Supplementary Fig. 5c). Collectively, activated and unstimulated NK cells were more cytotoxic against oHSV-infected than uninfected glioblastoma cells.
To further explore the mechanism of enhanced cytotoxicity, we found that oHSV infection led to cell contact–dependent and perforin-dependent32,33 killing (Supplementary Fig. 6a), minor alterations in human leukocyte antigen (HLA)-ABC staining (Supplementary Fig. 6b) and no change in the expression of the NK cell–activating receptors DNAM-1 and NKG2D (Supplementary Fig. 6c). Blockade of NKG2D inhibited killing of one of four glioblastoma cell lines, but this effect was not significant when all glioblastoma cell lines were analyzed collectively (P = 0.34) (Supplementary Fig. 6a). DNAM-1 blockade achieved moderate inhibition of cell killing in both oHSV- (P = 0.03) and mock-infected cells (P = 0.01) (Supplementary Fig. 6d). Therefore, it seemed that NK cell cytotoxicity was only partially dependent on canonical NK cell receptor recognition of oHSV-infected tumor cell lines.
We thus determined whether NCRs mediated the lysis of oHSV-infected glioblastoma cells34,35. We significantly inhibited NK cell–mediated in vitro killing using blocking antibodies to either NKp30 (P = 0.003) or NKp46 (P = 0.02) (Fig. 6a). In a mouse in vitro model, NKp46 (the only NCR in mice) mediated NK cell killing of oHSV-infected glioblastoma cells (Supplementary Fig. 6e). Moreover, we showed enhanced NCR ligand expression in oHSV-infected glio-blastoma cells in vitro, measured by using the NCR fusion protein NKp30-immunoglobulin (Fig. 6b). GFP is used to detect rQNes-tin34.5 infection, and the highly infected (GFPhigh) cell population also had maximum NKp30 ligand staining compared to uninfected cells (Fig. 6c). Similarly, there was enhanced NCR ligand expres-sion in oHSV-infected glioblastoma cells in vitro, assayed by using the NCR fusion protein NKp46-immunoglobulin (Fig. 6d), and the highly infected (GFPhigh) cell population also had maximum NKp46 ligand staining compared to uninfected cells (Fig. 6e). Notably, the upregulated NCR ligands were not the recently described NKp30 ligand B7-H6 (ref. 36 and data not shown).
We also investigated whether NCR ligands were upregulated after various modes of cellular stress, including exposure to temozolomide (TMZ), which is the chemotherapeutic agent used in the treatment
of glioblastoma. Although radiation or hypoxia induced moderate expression of NKp30 ligand but not the NKp46 ligand, TMZ induced the expression of both NKp30 and the NKp46 ligand to the same levels as did oHSV (Fig. 6f,g). Therefore, NK cell–mediated cytotoxicity of oHSV-treated glioblastoma cells is coordinated primarily through the NK cell receptors NKp30 and NKp46, which recognize cognate ligands on tumor cells that are upregulated by oHSV or TMZ.
To assess the role of NKp46 in viral clearance in vivo, we quantified WT HSV-1 replication after intracerebral inoculation in the brains of Ncr1−/− and WT mice. Compared to those in WT mice, WT HSV-1 titers were significantly enhanced in Ncr1−/− mice (Fig. 6h). We next investigated whether NKp46-deficient NK cells would lead to improved survival in our virotherapy tumor model. We adoptively transferred enriched NK cells from WT or Ncr1−/− mice into sublethally irra-diated severe combined immunodeficient (SCID)-γcnull mice (lack-ing host B, T and NK cells) and then performed intracranial tumor implantation. We found that oHSV treatment led to prolonged sur-vival in glioma-bearing SCID mice transplanted with NKp46-deficient NK cells compared to glioma-bearing SCID mice transplanted with WT NK cells (Fig. 6i), thus showing the importance of NKp46 in the ability of NK cells to impede the antitumor action of oHSV.
DISCUSSIONHere we explored the response of innate immunity to oHSV therapy of glioblastoma. We discovered a rapid NK cell response to tumor infection with oHSV. This in vivo antiviral NK cell response depends on specific cytotoxic NK cell subsets in the brain that also coordinate macrophage activation and leads to rapid killing of oHSV-infected glioblastoma cells. NK cell depletion improves the survival of glioblastoma-bearing mice treated with oHSV. We have discovered that oHSV-infected human glioblastomas upregulate ligands for the NK cell natural cytotoxicity receptors NKp30 and NKp46 in vitro. Recognition of these ligands is crucial for NK cell–mediated cyto-toxicity directed against oHSV-infected cells and viral clearance in vivo.
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Figure 5 IL-15–stimulated NK cells preferentially lyse oHSV-infected human and mouse glioblastoma. (a) NK cell–mediated cytotoxicity (measured as the percentage of glioblastoma lysis resulting from infection with rQNestin34.5 and coculture with IL-15–stimulated human NK cells compared to mock infection and coculture with IL-15–stimulated NK cells) in glioblastoma cell lines (U87dEGFR, Gli36dEGFR or U251) or primary human glioblastoma cells enriched for stem cell–like properties (X12). (b) IL-15–stimulated mouse NK cell–mediated cytotoxicity using splenocyte-derived mouse NK cells from athymic mice or from WT C57BL/6 mice, cocultured with KR158dEGFR or U87dEGFR glioblastomas, respectively. In a and b, NK cell–mediated killing was tested at varying effector-to-target ratios. Error bars, s.d.
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Collectively, we demonstrate that the rapid NK cell response to oHSV therapy cooperates with other innate immune cells to reduce, rather than enhance, the efficacy of oHSV treatment through NKp30 and NKp46. We argue that these findings, combined with clinical reports of patients with deficiencies in NK cell function being susceptible to HSV-1 encephalitis37, suggest that NK cells represent a substantial barrier to oHSV therapy of glioblastoma.
The role of NK cells in mediating the efficacy of virotherapy is contro-versial. Most studies show enhanced oHSV efficacy by eliciting an
NK cell–mediated antitumor response18–21. Only one previous study described the antiviral properties of NK cells as being detrimental to vesicular stomatitis virus therapy for hepatocellular carcinoma38. Our evidence shows that NK cells rapidly responding to oHSV infection of glioblastoma constitute a barrier to therapeutic efficacy. First, there is a decline in viral titers within days of oHSV administration5–8. Second, in preclinical studies, the clearance of oHSV approaches 80%, corresponding to rapid peripheral macrophage recruitment into the site of viral infection5,7, suggesting a mechanism of oHSV clearance.
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Figure 6 NKp30 and NKp46 orchestrate NK cell–mediated killing of oHSV-infected glioblastoma cells in vitro, and NKp46 mediates viral clearance in vivo. (a) NK cell–mediated killing of glioblastoma cell lines (U87dEGFR, Gli36dEGFR or U251) or primary human glioblastoma cells enriched for stem cell–like properties (X12) infected with rQNestin34.5 or vehicle before coculturing with IL-15–stimulated human NK cells at a ratio of 12.5:1. The effect of blocking antibodies to NKp30, NKp46 and NKp44 was also assessed. (b–e) FACS assessing ligand expression for NKp30 (b,c) and NKp46 (d,e) after infection with rQNestin34.5 or mock infection. Additionally, the expression of GFP by rQNestin34.5 was also assayed in virally infected cells as a function of NKp30 or NKp46 ligand expression (c,e). (f,g) NKp30 or NKp46 ligand expression in glioma cells in response to TMZ, radiation (10 Gy), hypoxia (f) or rQNestin34.5 infection (g). (h) WT HSV-1 titers in Ncr1−/− mice compared to WT C57BL/6 mice 72 h after infection (n = 3–4 mice per group). (i) Kaplan-Meier survival curves for U87dEGFR brain tumor–bearing SCID-γcnull mice adoptively transferred with either Ncr1−/− or WT NK cells and intracranially inoculated with rQNestin34.5 (n = 5 mice per group). *P < 0.05, **P < 0.01, ***P < 0.001 by Student’s t test. Error bars, s.d.
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These findings were validated through a study demonstrating that macrophage depletion enhanced the efficacy of oHSV therapy in glio-blastoma5. Third, a recent clinical trial of oHSV for glioblastoma noted prominent inflammatory infiltration within the tumor, correlating with reduced oHSV replication3. Fourth, mathematical model-ing has previously shown that the timing of the antiviral innate immune response is detrimental to oHSV therapy9. Collectively, this evidence strongly suggests that an initial innate immunity to oHSV therapy is detrimental to anticancer efficacy. However, other studies have shown that immune responses to vesicular stomatitis virus virotherapy for metastatic non–central nervous system tumors are highly desirable20,39,40. Therefore, the effect of immunity on the efficacy of virotherapy may require a balance between virus repli-cation and antitumor responses that may differ on the basis of the oncolytic virus and tumor.
For the first time, to our knowledge, we show that mouse NK cells recruited to an oHSV-infected brain tumor upregulate mark-ers of an activated phenotype. Knowing that NK cells produce sub-stantial amounts of Ifng and oHSV replication is enhanced in both Ifng- and macrophage-depleted mice5,7 led us to hypothesize that NK cells mediate oHSV-induced macrophage and microglia activa-tion41. We demonstrated that this activation, occurring after oHSV administration, is NK-cell and Ifng dependent. Our results argue that the reduction of macrophage and microglia activation markers, including Nos2, Tnf and IIC, in oHSV-infected tumors was prob-ably caused by the loss of NK cell–mediated activation (in the setting of NK cell depletion with NK antibodies) rather than by the loss of macrophage and microglia cell numbers. Notably, oHSV infection led to a robust NK cell–dependent and Ifng-dependent induction of Cxcl9, Cxcl10 and Cxcl11 expression. These chemokines are associated with macrophage activation and herpes encephalitis41. Future clinical studies should assess whether the recruitment of IFNG-producing CD3−CD56brightCD94bright human NK cells42 is associated with both oHSV inoculation and the activation of macrophages and micro-glia. Similarly, the CD3−CD56dimCD94dim NK cell subset42, which is associated with cell-mediated killing, may translate into prefer-ential killing of virally infected glioblastoma cells before efficacious oncolysis has occurred. Future clinical trials should clarify the NK cell subsets by examining CD56 and CD94 expression42, along with their associated functional properties.
We also assessed the effect of NK cell depletion in a fully immuno-competent mouse model. After screening several mouse glioblasto-mas, the KR158dEGFR glioblastoma line showed oHSV replication and cytotoxicity in vitro approximating that of human glioblastomas (data not shown). However, KR158dEGFR is syngeneic to C57BL/6 mice, a strain that is notoriously impervious to HSV-1 infection43. Because of minimal in vivo viral replication in this model (data not shown), we instead used the mouse 4C8 model31. Although oHSV replicates about 1.5 log times less in 4C8 cells than in human glioma cells (data not shown), the syngeneic B6D2F1/J mouse strain is more sensitive to HSV-1 infection than the C57BL/6 strain15. Yet, even in this model, we found significant survival from syngeneic gliomas with oHSV treatment only in the absence of NK cells, further underscoring the importance of NK cells in limiting glioma virotherapy.
A common feature of glioblastoma is the endogenous expression of ligands for activating NK cell receptors34,35. Recent studies have explored the role of HSV-1 infection in modulating the expression of NK cell–activating ligands. In human glioblastoma cell lines infected with oHSV, we observed upregulation of ligands for NKp46 and NKp30. Blockade of these two receptors significantly reduced NK
cell cytotoxicity. Increases in tumor cell ligand expression occur with oHSV infection or treatment with TMZ but not with other methods of tumor killing. These data argue for a relatively specific increased recognition of the ligands for NKp30 and NKp46.
The identity of ligands for NCRs is a field of intense investigation44, with influenza hemagglutinin having been identified as an activating ligand for NKp46 and NKp44 (ref. 45). NKp30 is involved in viral eradication by binding to an unknown ligand on immature dendritic cells46 and in viral evasion through its recognition of the human cytomegalovirus tegument protein pp65 (refs. 47,48). Additionally, NKp30 recognizes B7-H6 (ref. 36), a cell-surface protein that is asso-ciated with tumor formation, and Bat3 (ref. 49), a released cellular stress protein. Although NKp30 and NKp46 mediated NK cell lysis of oHSV-infected glioblastoma, B7-H6 did not seem to be involved. Moreover, cell-surface expression of the NKp30 and NKp46 ligands was similar after either oHSV infection or treatment with TMZ. These findings suggest that the ligands for NKp30 and NKp46 are of cellular rather than viral origin. Once the identities of the NKp30 and NKp46 ligands are uncovered, future work will investigate whether they can predict sensitivity to oncolysis for personalized treatment.
As NCR expression is differentially regulated to high (NCRbright) or low levels (NCRdim) of expression (ref. 50), future clinical stud-ies should examine the NCR phenotype after oHSV treatment and assess whether the expression of NCRs correlates with diminished viral replication. By clarifying the crucial receptor-ligand interactions that mediate human NK cell killing of oHSV-infected glioblastoma, we have uncovered a potential therapeutic target that, when blocked in vivo, could limit NK cell clearance of these infected cells in future clinical trials.
METHODSMethods and any associated references are available in the online version of the paper.
Note: Supplementary information is available in the online version of the paper.
ACKnOWLEdgMEntSThis work was supported by US National Institutes of Health grants 7U01NS061811 (to E.A.C.), CA069246 (to E.A.C.), CA068458 (to M.A.C.), CA095426 (to M.A.C.), TL1RR025753 (to C.A.A.-B.) and CA163205 (to E.A.C., M.A.C. and B.K.). C.A.A.-B. was supported by an American Medical Association Foundation Seed Grant. This work was also supported by the Dardinger Neuro-oncology Laboratory.
AUtHOR COntRIBUtIOnSC.A.A.-B., J.Y., R.P., J.W., J.P., H.M., M.W., Y.W., S.H. and J.H. performed experiments. C.A.A.-B., J.Y., B.K., S.E.L., A.M., M.A.C. and E.A.C. conceived the experimental approach, directed experiments and interpreted data. S.A.F. performed statistical analysis. E.V., O.M. and A.M. provided reagents. C.A.A.-B., J.Y., M.A.C. and E.A.C. wrote the manuscript.
COMPEtIng FInAnCIAL IntEREStSThe authors declare no competing financial interests.
Published online at http://www.nature.com/doifinder/10.1038/nm.3013. Reprints and permissions information is available online at http://www.nature.com/reprints/index.html.
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ONLINE METHODSCell culture. We used human glioblastoma cell lines (U87dEGFR, U251 and Gli36dEGFR), primary human glioblastoma cells enriched for stem cell–like properties (X12 (ref. 51)), mouse glioblastoma cell lines (KR158dEGFR52 and 4C8 (ref. 15)) and African green monkey kidney (Vero) cells. We cultured cells in DMEM (Invitrogen) supplemented with 10% FBS, penicillin (100 U ml−1), and streptomycin (100 µg ml−1). We cultured human- and mouse-derived NK cells in RPMI-1640 (Invitrogen) supplemented with 10% FBS, penicillin (100 U ml−1), and streptomycin (100 µg ml−1). We cultured cells at 37 °C sup-plemented with 5% CO2.
Mouse studies. The Institutional Animal Care and Use Committee at Ohio State University approved all mouse experiments and care. We anesthetized athymic, C57BL/6 (Charles River Laboratories), B6.129S7-Ifngtm1Ts/J (Ifng−/−), B6D2F1/J and nonobese diabetic (NOD)-SCID IL-2Rγnull (SCID-γcnull) 8-week-old female mice53 (The Jackson Laboratory) with intraperitoneal ketamine (100 mg per kg body weight) or xylazine (20 mg per kg body weight) and stereotactically injected glioblastoma cells into the right frontal lobe (2 mm lateral and 1 mm anterior to bregma at a depth of 3 mm). We injected a total of 1 × 105 human U87dEGFR, 4 × 105 mouse KR158dEGFR and 2 × 105 mouse 4C8 glioblastoma cells. For NK cell depletion experiments, either 200 µg of TMβ1-specific (ref. 54) or 50 µl asialo-GM1–specific antibody combined with 50 µl water (Wako, 986-10001) was injected intraperitoneally 2 d before oHSV administration. For NK1.1 depletion, we injected 200 µg of antibody (PK136) (Bio X Cell, West Lebanon, NH, BE0036, stock: 12.42 µg/µl) intravenously 4 d before, 1 d before and 2 d after virus inocula-tion55. We allowed U87dEGFR cells to grow for 9 d, the KR158dEGFR cells for 10 d and the 4C8 cells for 21 d. After that, we injected the mice intratumorally with either rQNestin34.5 or HBSS. For experiments with WT HSV-1 (F Strain), we injected 104 plaque-forming units of virus into the right frontal lobe.
Adoptive transfer experiments. For adoptive transfer into Ifng−/− mice, we prepared donor NK cells using 8-week-old Ly5.1 WT and Ly5.2 Ifng−/− female mice. We enriched NK cells from splenocytes using the NK Cell Isolation Kit (Miltenyi Biotech), and we purified these cells by FACS by sorting CD3-FITC (17A2) and NK1.1-phycoerythrin (PE) (PK136) (BD) with antibody dilutions of 1:200. We used Ly5.2 Ifng−/− mice as recipients that received 2.2 million puri-fied NK cells per mouse from either Ly5.1 WT or Ly5.2 Ifng−/− mice 4 h after 4 Gy irradiation (RS 2000 X-Ray Irradiator, Rad Source Technologies, Inc.). For adoptive transfer into SCID-γcnull mice, we treated splenocytes from Ncr1−/− (ref. 56) and WT C57BL/6 mice with NK Negative Selection Cocktails (Miltenyi Biotech) and MACS LS Column purification. We then transplanted the isolated NK cells into irradiated SCID-γcnull mice (1.5 Gy dose) with 5 million cells per mouse. We then implanted tumors 4 weeks after transplantation.
Flow cytometric analysis. We isolated mononuclear cells from oHSV-infected brains using a previously described procedure57. For analysis of splenocyte-derived NK cell levels, we collected and homogenized tissues through a 70-µm strainer. We lysed erythrocytes using RBC Lysis Buffer (Biolegend). We treated cells, isolated from either the brain or the spleen, with Fc Block (BD). We then stained cells with mouse-specific immune cell surface markers for 30 min at 4 °C. We used mouse-specific antibodies to the following at a dilution of 1:200: CD3-FITC (17A2), CD49b-PE (DX5), CD3-PercP (145-2C11), CD62L-allophycocyanin (APC) (MEL-14), CD11b-PE (M1/70), CD27-PE (LG.3A10) and Nos2-FITC (6/iNOS/NOS Type II) (BD); CD62L-FITC (MEL-14), CD69-FITC (H1.2F3), NKG2D-APC (CX5), CD27-FITC (LG.7F9), Ly49d-APC (4E5), CD94-FITC (18d3), NKp46-FITC (29A1.4), CD127-FITC (A7R34), CD117-FITC (2B8), NKG2A-FITC (20d5), MHC-II–FITC (M5/114.15.2), CD86-PercP (GL1), CD11b-PercP (M1/70), CD3-APC (17A2), CD45-APC (30-F11), Tnf-FITC (MP6-XT22) and CD107a-FITC (1D4B) (eBioscience); Ly-6c–FITC (HK1.4) (Biolegend); and CD49b-APC (DX5) (Miltenyi Biotec). For CD107a staining, we cultured mononuclear cells in 10% RPMI with monensin (eBio-science) for 4 h before cell-surface staining. For Tnf staining, we cultured mono-nuclear cells in 10% RPMI with Golgi-Plug (BD) for 4 h before intracellular staining. For staining of both Tnf and Nos2, we followed the initial cell-surface staining with Cytofix/Cytoperm (BD) and then with intracellular staining. A FACS Calibur (Becton Dickinson) was used for analysis.
Viral yield assay. We measured titers of infectious virus particles recovered from virus-inoculated brains as follows. We inoculated athymic mice bearing 9-day-old U87dEGFR tumors intratumorally with 5 × 105 plaque-forming units of rQNestin34.5. C57BL/6 or Ncr1−/− mice were intracranially inoculated with 104 plaque-forming units of WT HSV-1. Seventy-two hours later, we recovered the titers of infectious virus particles as described5.
Quantitative real-time RT-PCR. We isolated total RNA from tumor-bearing hem-ispheres using the RNeasy Lipid Tissue Midi kit (Qiagen) with quantitative real-time PCR performed as previously described using the SYBR Green PCR Master Mix and an ABI PRISM 7500 sequence detection system (Applied Biosystems)8. We used the following primers: 5′-GAACGGAGATCAAACCTGCCT-3′ and 5′-TGTAGTCTTCCTTGAACGACGA-3′ for Cxcl9; 5′-TGGAGGAACT GGCAAAAGGA-3′ and 5′-TGTTGCTGATGGCCTGATTG-3′ for Ifng; 5′-CAGCTGGGCTGTACAAACCTT-3′ and 5′-CATTGGAAGTGAAGCGTT TCG-3′ for Nos2; 5′-CATATGGAATCCAACTGGATAGATGTAAGATA-3′ and 5′-CATATGCTCGAGGGACGTGTTGATGAACAT-3′ for Il15; 5′-AAGCC TGTAGCCCACGTCGTA-3′ and 5′- GGCACCACTAGTTGGTTGTCTTTG-3′ for Tnf; 5′- TGAATCCGGAATCTAAGACCATCAA-3′ and 5′- AGGACTAGCCATCCACTGGGTAAAG-3′ for Cxcl10; 5′- GGCTGCGACAAAGTTGAAG TGA-3′ and 5′-TCCTGGCACAGAGTTCTTATTGGAG-3′ for Cxcl11; and 5′-AAATGGTGAAGGTCGGTGTG-3′ and 5′-TGAAGGGGTCGTTGATGG-3′ for the internal control, glyceraldehyde-3-phosphate dehydrogenase (GAPDH). We sorted brain leukocytes with antibodies to mouse CD45-APC and CD11b-PE using FACS (BD FACSAria). We isolated total RNA from 20,000 cells of each population with the RNeasy Micro Kit (Invitrogen) and analyzed them by quan-titative real-time RT-PCR. To assess inflammatory gene expression, we used the Mouse Inflammatory Cytokines and Receptors RT2 Profiler PCR Array (Super Array Bioscience Corporation) following the manufacturer’s instructions.
NK cell isolation. We enriched NK cells or CTLs from peripheral blood leu-kopacks of healthy donors (American Red Cross, Columbus, Ohio) using RosetteSep cocktail (StemCell Technologies) and either CD56 or CD8 mag-netic bead sorting (Miltenyi Biotec). Isolation was performed after approval of a human subject protocol by the Institutional Review Board of the James Cancer Hospital at the Ohio State University (protocol number: 2009A0033; protocol name: Immunology of Cancer and Inflammation). Mouse NK cells were isolated from mouse splenocytes using positive selection bead sorting for DX5.
Cytotoxicity assay. We plated a panel of human glioblastoma cells overnight and infected them the next day with rQNestin34.5 (multiplicity of infection, 1.0) or mock infected them. Eight hours later, we added human NK cells or CTLs at different effector-to-target ratios in the presence of human IL-15 (for NK cells) or IL-2 (for CTLs) (Miltenyi Biotec). The coculture was allowed to proceed for 4 h at 37 °C. We assessed glioblastoma lysis with the Vybrant Cytotoxicity Assay Kit (Molecular Probes). For studies evaluating pharmacological inhibitors of cytolysis, we preincubated NK cells for 1 h with: EGTA/Mg2+ (2 mM/4 mM) or chloroquine (100 µg ml−1). For NCR masking experiments, we preincubated NK cells for 1 h with the appropriate blocking antibody. We treated human NK cells with blocking antibodies (provided by A.M.) to the following at 10 µg ml−1: DNAM-1 (F5), NKp30 (F252), NKp44 (KS38), NKp46 (KL247) and NKG2D (BAT221)58. Mouse NK cells were treated with blocking antibody to mouse NKp46 (29A1.4) at 10 µg ml−1 (ref. 59) (provided by E.V.). We then added NK cells to infected or mock-infected glioblastomas and cocultured them for 4 h at 37 °C.
Analysis of NK cell ligand expression. We used recombinant human NKp30-IgG or NKp46-IgG fusion proteins (R&D Systems) to investigate the expression of NK cell ligands on glioblastoma cells 8 h after oHSV infection or after treat-ment with TMZ (200 µM), 10 Gy radiation or hypoxia (1% O2 and 5% CO2). We stained for NK cell ligands by the addition of 10 µl of reconstituted IgG fusion proteins followed by incubation with APC-conjugated mouse antibody to human IgGfc (Jackson ImmunoResearch, 109-136-098) at a 1:100 dilution35. We also analyzed the expression of B7-H6 after oHSV infection of glioblastoma. Eight hours after infection, we also tested B7-H6 expression with 10 µg ml−1 of mouse antibody to human B7-H6 (gift from ZymoGenetics). We assessed
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cell-surface staining of oHSV- or mock-infected glioblastoma with human-specific antibodies to the following at a dilution of 1:10: MICA/B-PE (159207), ULBP-1–PE (170818), ULBP-2–PE (165903) and CD155-PE (300907) (R&D); HLA-ABC–PE (W6/32) (eBioscience); and CD48-PE (BJ40) and CD112-PE (TX31) (Biolegend).
Statistical analyses. All statistical tests were two sided. We used ANOVA models or t tests to study group differences for all the continuous outcome variables. A χ2 test was used to compare counts or proportions. We used log-rank tests to compare group effects on time-to-event variables. Total NK cells and per-centages of NK cells were log transformed (natural log) to achieve normality. We used two-way ANOVA models to study the association between groups (U87dEGFR plus vehicle, U87dEGFR plus rQNestin34.5 and U87dEGFR plus heat-inactivated rQNestin34.5), time and the total number or percentage of NK cells. The interaction term treatment × time was also included in the models. The interaction term was significant in the model for Figure 1b and Supplementary Figure 1a, and this is because of the larger slope or rate of increase in the total number and percentage of NK cells, respectively, across time observed in the U87dEGFR plus rQNestin34.5 treatment group. We performed pairwise com-parisons when the group main effect was significant in the ANOVA model (Fig. 1b and Supplementary Fig. 1a). We used two-sample t tests to compare outcome variables between groups (Figs. 1c and 3b,d,e,g,i,j, Supplementary Figs. 1c and 2b,c and Supplementary Tables 1a,b and 2a,b). We used two-way ANOVA to compare the NK cell fold increase (natural log) across different phenotypes and different groups. The interaction term was included and found
to be highly significant (Fig. 2c). We compared the percentage of glioblastoma lysis using pairwise comparisons (chloroquine or EGTA/Mg2+ compared to untreated) and found it to be significant (Supplementary Fig. 6a). We used χ2 tests (3 × 2 tables) to study the differences in cell type proportions between groups (treated or untreated) at each time point (6, 24 and 72 h).
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Corrigendum: NK cells impede glioblastoma virotherapy through NKp30 and NKp46 natural cytotoxicity receptorsChristopher A Alvarez-Breckenridge, Jianhua Yu, Richard Price, Jeffrey Wojton, Jason Pradarelli, Hsiaoyin Mao, Min Wei, Yan Wang, Shun He, Jayson Hardcastle, Soledad A Fernandez, Balveen Kaur, Sean E Lawler, Eric Vivier, Ofer Mandelboim, Alessandro Moretta, Michael A Caligiuri & E Antonio ChioccaNat. Med. 18, 1827–1834 (2012); published online 25 November 2012; corrected after print 7 October 2013
In the version of this article initially published, the Online Methods incorrectly stated that mouse NK cells were treated with a blocking antibody to mouse NKp46 called BAB281. The correct antibody used to treat the cells was 29A1.4. The error has been corrected in the HTML and PDF versions of the article.
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