Microenvironment and Immunology TGFb Treatment Enhances Glioblastoma Virotherapy by Inhibiting the Innate Immune Response

Oncolytic viruses, including oncolytic herpes simplex virus (oHSV), have produced provocative therapeutic responses in patients with glioblastoma, the most aggressive brain tumor. Paradoxically, innate immune responses mediated by natural killer (NK) cells and macrophages/microglia appear to limit oHSV efficacy. Therefore, we investigated whether pretreatment with an immunosuppressive cytokine, TGFb, might reverse these effects and thereby potentiate oHSV efficacy. TGFb treatment of NK cells rendered them less cytolytic against oHSV-infected glioblastoma cells and stem-like cells in vitro. Furthermore, TGFb treatment of NK cells, macrophages, or microglia increased viral titers of oHSV in cocultures with glioblastoma cells. In a syngeneic mouse model of glioblastoma, administering TGFb prior to oHSV injection inhibited intracranial infiltration and activation of NK cells and macrophages. Notably, a single administration of TGFb prior to oHSV therapy was sufficient to phenocopy NK-cell depletion and suppress tumor growth and prolong survival in both xenograft and syngeneic models of glioblastoma. Collectively, our findings show how administering a single dose of TGFb prior to oncolytic virus treatment of glioblastoma can transiently inhibit innate immune cells that limit efficacy, thereby improving therapeutic responses and survival outcomes. Cancer Res; 75(24); 1–10. 2015 AACR. Introduction Glioblastoma is the most common and aggressive primary brain tumor in adults (1). The current standard treatment for glioblastoma consists of surgical resection followed by radiotherapy and chemotherapy. However, even with this multipronged approach, the median overall survival of patients with glioblastoma is only 14.6 months due to the highly infiltrative nature of glioblastoma that prevents effective resection (2). Therefore, there is an urgent need to develop novel and effective therapies for this devastating malignancy. Oncolytic viruses are viruses genetically engineered to selectively replicate in tumor cells and trigger tumor cell lysis while sparing normal cells (3). Importantly, this activity is also associated with the enhancement of antitumor immune responses, introducing the potential for extended disease control (4, 5). Oncolytic herpes simplex viruses (oHSV) have been shown to be effective for the treatment of various cancers especially when combined with other reagents, and an oHSV-expressing granulocyte macrophage colony-stimulating factor has demonstrated improvement in durable response rates with a tolerable safety profile in phase III malignant melanoma trials (6). Oncolytic viruses have attracted particular attention as distinctive antiglioblastoma biologic agents, due not only to the relatively restricted localization of glioblastoma in the brain but also to the fact that the surrounding normal cells are postmitotic and thus less susceptible to nonselective viral infection and lysis (7). However, the host innate immune response to oHSV has been shown to impair efficient virus replication and spread within tumor tissues following initial infection, which results in compromised therapeutic efficacy of oHSV against glioblastoma (8, 9). We previously demonstrated that administration of oHSV in the brain induced rapid recruitment and activation of natural killer (NK) cells, which substantially increased viral clearance and limited antitumor efficacy of oHSV in both athymic and immunocompetent mouse models (10). In addition, oHSV-activated NK cells coordinatedmacrophage andmicroglia activationwithin tumors, thereby facilitating their viral clearance properties. NKcell depletion prolonged overall survival of glioblastoma-bearing mice in a xenograft U87DeltaEGFR (U87dEGFR) model and a syngeneic 4C8 model (10). Suppression of initial innate antiviral defense responses is thus predicted to augment virus replication and tumor lysis, prior to eventual tumor clearance by multiple mechanisms, including later stage host antitumor immune Division of Hematology, Department of Internal Medicine, College of Medicine,The Ohio State University, Columbus, Ohio. The Ohio State University Comprehensive Cancer Center, Columbus, Ohio. Department of Neurological Surgery, The Ohio State University, Columbus, Ohio. Center for Biostatistics, The Ohio State University, Columbus, Ohio. Department of Biomedical Engineering, The Ohio State University, Columbus, Ohio. Department of Radiology, College of Medicine, The Ohio State University, Columbus, Ohio. Department of Neurosurgery, Brigham and Women's Hospital and Harvey Cushing Neuro-oncology Laboratories, Harvard Medical School, Boston, Massachusetts. Note: Supplementary data for this article are available at Cancer Research Online (http://cancerres.aacrjournals.org/). J. Han and X. Chen contributed equally to this article. Corresponding Author: Jianhua Yu, The Ohio State University Wexner Medical Center, 460 West 12th Avenue, BRT 816, Columbus, OH 43210. Phone: 614-2931471; Fax: 614-688-4028; E-mail: [email protected] doi: 10.1158/0008-5472.CAN-15-0894 2015 American Association for Cancer Research. Cancer Research www.aacrjournals.org OF1 Research. on April 14, 2017. © 2015 American Association for Cancer cancerres.aacrjournals.org Downloaded from Published OnlineFirst December 2, 2015; DOI: 10.1158/0008-5472.CAN-15-0894