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      Antitumor effects of oncolytic herpes simplex virus type 2 against colorectal cancer in vitro and in vivo

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          Abstract

          Background

          The incidence of colorectal cancer (CRC) is on the rise. Furthermore, late-stage diagnoses and limited efficacious treatment options make CRC a complex clinical challenge. Therefore, a new therapeutic regimen with a completely novel therapeutic mechanism is necessary for CRC. In the present study, the therapeutic efficacy of oncolytic herpes simplex virus type 2 (oHSV2) in CRC was assessed in vitro and in vivo. oHSV2 is an oncolytic agent derived from herpes simplex virus type 2 that encodes granulocyte-macrophage colony-stimulating factor.

          Materials and methods

          We investigated the cytopathic effects of oHSV2 in CRC cell lines using the MTT assay. Then, cell cycle progression and apoptosis of oHSV2 were examined by flow cytometry. We generated a model of CRC with mouse CRC cell CT26 in BALB/c mice. The antitumor effects and adaptive immune response of oHSV2 were assessed in tumor-bearing mice. The therapeutic efficacy of oHSV2 was compared with the traditional chemotherapeutic agent, 5-fluorouracil.

          Results

          The in vitro data showed that oHSV2 infected the CRC cell lines successfully and that the tumor cells formed a significant number of syncytiae postinfection. The oHSV2 killed cancer cells independent of the cell cycle and mainly caused tumor cells necrosis. The in vivo results showed that oHSV2 significantly inhibited tumor growth and prolonged survival of tumor-bearing mice without weight loss. With virus replication, oHSV2 not only resulted in a reduction of myeloid-derived suppressor cells and regulatory T cells in the spleen, but also increased the number of mature dendritic cells in tumor-draining lymph nodes and the effective CD4 +T and CD8 +T-cells in the tumor microenvironment.

          Conclusion

          Our study provides the first evidence that oHSV2 induces cell death in CRC in vitro and in vivo. These findings indicate that oHSV2 is an effective therapeutic cancer candidate that causes an oncolytic effect and recruits adaptive immune responses for an enhanced therapeutic impact, thus providing a potential therapeutic tool for treatment of CRC.

          Most cited references43

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          ONCOLYTIC VIROTHERAPY

          Oncolytic virotherapy is an emerging treatment modality which uses replication competent viruses to destroy cancers. Advances in the past two years include preclinical proof of feasibility for a single-shot virotherapy cure, identification of drugs that accelerate intratumoral virus propagation, new strategies to maximize the immunotherapeutic potential of oncolytic virotherapy, and clinical confirmation of a critical viremic thereshold for vascular delivery and intratumoral virus replication. The primary clinical milestone was completion of accrual in a phase III trial of intratumoral herpes simplex virus therapy using talimogene laherparepvec for metastatic melanoma. Challenges for the field are to select ‘winners’ from a burgeoning number of oncolytic platforms and engineered derivatives, to transiently suppress but then unleash the power of the immune system to maximize both virus spread and anticancer immunity, to develop more meaningful preclinical virotherapy models and to manufacture viruses with orders of magnitude higher yields compared to established vaccine manufacturing processes.
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            Vaccination with irradiated tumor cells engineered to secrete murine granulocyte-macrophage colony-stimulating factor stimulates potent, specific, and long-lasting anti-tumor immunity.

            To compare the ability of different cytokines and other molecules to enhance the immunogenicity of tumor cells, we generated 10 retroviruses encoding potential immunomodulators and studied the vaccination properties of murine tumor cells transduced by the viruses. Using a B16 melanoma model, in which irradiated tumor cells alone do not stimulate significant anti-tumor immunity, we found that irradiated tumor cells expressing murine granulocyte-macrophage colony-stimulating factor (GM-CSF) stimulated potent, long-lasting, and specific anti-tumor immunity, requiring both CD4+ and CD8+ cells. Irradiated cells expressing interleukins 4 and 6 also stimulated detectable, but weaker, activity. In contrast to the B16 system, we found that in a number of other tumor models, the levels of anti-tumor immunity reported previously in cytokine gene transfer studies involving live, transduced cells could be achieved through the use of irradiated cells alone. Nevertheless, manipulation of the vaccine or challenge doses made it possible to demonstrate the activity of murine GM-CSF in those systems as well. Overall, our results have important implications for the clinical use of genetically modified tumor cells as therapeutic cancer vaccines.
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              Local and distant immunity induced by intralesional vaccination with an oncolytic herpes virus encoding GM-CSF in patients with stage IIIc and IV melanoma.

              An oncolytic herpes simplex virus engineered to replicate selectively in tumor cells and to express granulocyte-macrophage colony-stimulating factor (GMCSF) was tested as a direct intralesional vaccination in melanoma patients. The work reported herein was performed to better characterize the effect of vaccination on local and distant antitumor immunity. Metastatic melanoma patients with accessible lesions were enrolled in a multicenter 50-patient phase II clinical trial of an oncolytic herpesvirus encoding GM-CSF (Oncovex(GM-CSF)). An initial priming dose of 10(6) pfu vaccine was given by intratumoral injection, followed by 10(8) pfu every 2 weeks to 24 total doses. Peripheral blood and tumor tissue were collected for analysis of effector T cells, CD4(+)FoxP3(+) regulatory T cells (Treg), CD8(+)FoxP3(+) suppressor T cells (Ts), and myeloid-derived suppressive cells (MDSC). Phenotypic analysis of T cells derived from tumor samples suggested distinct differences from peripheral blood T cells. There was an increase in melanomaassociated antigen recognized by T cells (MART-1)-specific T cells in tumors undergoing regression after vaccination compared with T cells derived from melanoma patients not treated with vaccine. There was also a significant decrease in Treg and Ts cells in injected lesions compared with noninjected lesions in the same and different melanoma patients. Similarly MDSC were increased in melanoma lesions but underwent a significant decrease only in vaccinated lesions. Melanoma patients present with elevated levels of Tregs, Ts, and MDSC within established tumors. Direct injection of Oncovex(GM-CSF) induces local and systemic antigen-specific T cell responses and decreases Treg, Ts, and MDSC in patients exhibiting therapeutic responses.
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                Author and article information

                Journal
                Ther Clin Risk Manag
                Ther Clin Risk Manag
                Therapeutics and Clinical Risk Management
                Therapeutics and Clinical Risk Management
                Dove Medical Press
                1176-6336
                1178-203X
                2017
                07 February 2017
                : 13
                : 117-130
                Affiliations
                [1 ]School of Medicine and Life Sciences, University of Jinan-Shandong Academy of Medical Sciences, Jinan
                [2 ]Department of Gastrointestinal Cancer Surgery, Shandong Cancer Hospital Affiliated to Shandong University, Shandong Academy of Medical Sciences, Jinan
                [3 ]Department of Gastrointestinal Surgery, The Affiliated Hospital of Shandong Academy of Medical Sciences, Jinan
                [4 ]Department of General Surgery, The Sixth People’s Hospital of Jinan, Jinan, People’s Republic of China
                Author notes
                Correspondence: Yanlai Sun, Department of Gastrointestinal Cancer Surgery, Shandong Cancer Hospital Affiliated to Shandong University, Shandong Academy of Medical Sciences, 440 Jiyan Road, Jinan 250117, People’s Republic of China, Email sunyanlai@ 123456126.com
                Zhongfa Xu, Department of Gastrointestinal Surgery, The Affiliated Hospital of Shandong Academy of Medical Sciences, 38 Wuyingshan Road, Jinan 250031, People’s Republic of China, Email xzfa2216@ 123456163.com
                Article
                tcrm-13-117
                10.2147/TCRM.S128575
                5308569
                28223815
                17801a5c-12c2-4317-8bcc-01102e413845
                © 2017 Yin et al. This work is published and licensed by Dove Medical Press Limited

                The full terms of this license are available at https://www.dovepress.com/terms.php and incorporate the Creative Commons Attribution – Non Commercial (unported, v3.0) License ( http://creativecommons.org/licenses/by-nc/3.0/). By accessing the work you hereby accept the Terms. Non-commercial uses of the work are permitted without any further permission from Dove Medical Press Limited, provided the work is properly attributed.

                History
                Categories
                Original Research

                Medicine
                colorectal cancer,oncolytic virus,herpes simplex virus type 2,granulocyte,macrophage colony-stimulating factor,immunotherapy,gene therapy

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