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1.  Immune Suppression during Oncolytic Virotherapy for High-Grade Glioma; Yes or No? 
Journal of Cancer  2015;6(3):203-217.
Oncolytic viruses have been seriously considered for glioma therapy over the last 20 years. The oncolytic activity of several oncolytic strains has been demonstrated against human glioma cell lines and in in vivo xenotransplant models. So far, four of these stains have additionally completed the first phase I/II trials in relapsed glioma patients. Though safety and feasibility have been demonstrated, therapeutic efficacy in these initial trials, when described, was only minor. The role of the immune system in oncolytic virotherapy for glioma remained much less studied until recent years. When investigated, the immune system, adept at controlling viral infections, is often hypothesized to be a strong hurdle to successful oncolytic virotherapy. Several preclinical studies have therefore aimed to improve oncolytic virotherapy efficacy by combining it with immune suppression or evasion strategies. More recently however, a new paradigm has developed in the oncolytic virotherapy field stating that oncolytic virus-mediated tumor cell death can be accompanied by elicitation of potent activation of innate and adaptive anti-tumor immunity that greatly improves the efficacy of certain oncolytic strains. Therefore, it seems the three-way interaction between oncolytic virus, tumor and immune system is critical to the outcome of antitumor therapy. In this review we discuss the studies which have investigated how the immune system and oncolytic viruses interact in models of glioma. The novel insights generated here hold important implications for future research and should be incorporated into the design of novel clinical trials.
doi:10.7150/jca.10640
PMCID: PMC4317755  PMID: 25663937
glioblastoma; oncolytic virotherapy; antitumor immunity
2.  Targeting of Interferon-Beta to Produce a Specific, Multi-Mechanistic Oncolytic Vaccinia Virus 
PLoS Medicine  2007;4(12):e353.
Background
Oncolytic viruses hold much promise for clinical treatment of many cancers, but a lack of systemic delivery and insufficient tumor cell killing have limited their usefulness. We have previously demonstrated that vaccinia virus strains are capable of systemic delivery to tumors in mouse models, but infection of normal tissues remains an issue. We hypothesized that interferon-beta (IFN-β) expression from an oncolytic vaccinia strain incapable of responding to this cytokine would have dual benefits as a cancer therapeutic: increased anticancer effects and enhanced virus inactivation in normal tissues. We report the construction and preclinical testing of this virus.
Methods and Findings
In vitro screening of viral strains by cytotoxicity and replication assay was coupled to cellular characterization by phospho-flow cytometry in order to select a novel oncolytic vaccinia virus. This virus was then examined in vivo in mouse models by non-invasive imaging techniques. A vaccinia B18R deletion mutant was selected as the backbone for IFN-β expression, because the B18R gene product neutralizes secreted type-I IFNs. The oncolytic B18R deletion mutant demonstrated IFN-dependent cancer selectivity and efficacy in vitro, and tumor targeting and efficacy in mouse models in vivo. Both tumor cells and tumor-associated vascular endothelial cells were targeted. Complete tumor responses in preclinical models were accompanied by immune-mediated protection against tumor rechallenge. Cancer selectivity was also demonstrated in primary human tumor explant tissues and adjacent normal tissues. The IFN-β gene was then cloned into the thymidine kinase (TK) region of this virus to create JX-795 (TK−/B18R−/IFN-β+). JX-795 had superior tumor selectivity and systemic intravenous efficacy when compared with the TK−/B18R− control or wild-type vaccinia in preclinical models.
Conclusions
By combining IFN-dependent cancer selectivity with IFN-β expression to optimize both anticancer effects and normal tissue antiviral effects, we were able to achieve, to our knowledge for the first time, tumor-specific replication, IFN-β gene expression, and efficacy following systemic delivery in preclinical models.
Stephen Thorne and colleagues describe, in a mouse model, an oncolytic vaccinia virus with interferon-dependent cancer selectivity that allows tumor-specific replication; it also expresses the IFN-β gene and hence has efficacy against tumors.
Editors' Summary
Background.
Normally, throughout life, cell division (which produces new cells) and cell death are carefully balanced to keep the body in good working order. But sometimes cells acquire changes (mutations) in their genetic material that allow them to divide uncontrollably to form cancers—disorganized masses of cells. Cancers can develop anywhere in the body and, as they develop, their cells acquire other genetic changes that enable them to move and start new tumors (metastases) elsewhere. Chemotherapy drugs kill rapidly dividing cancer cells but, because some normal cells are also sensitive to these drugs, it is hard to destroy the cancer without causing serious side effects. Consequently, researchers are trying to develop “targeted” therapies that attack the changes in cancer cells that allow them to divide uncontrollably but leave normal cells unscathed. One promising class of targeted therapies is oncolytic viruses. These viruses make numerous copies of themselves inside cancer cells (but not inside normal cells). Eventually the cancer cell bursts open (lyses), releases more of the therapeutic agent, and dies.
Why Was This Study Done?
Existing oncolytic viruses have two major disadvantages: they have to be injected directly into tumors, and therefore they can't destroy distant metastases; and they don't kill cancer cells particularly efficiently. In this study, the researchers have tried to adapt vaccinia virus (a virus that infects humans and which has recently been shown to kill tumor cells when injected into the bloodstream) in two ways: to both infect cancer cells selectively and then to kill them effectively.
They hypothesized that putting a gene that causes expression of a protein called interferon-beta (IFN-β) in a particular virus strain that is itself incapable of responding to IFN-β might achieve these aims. Human cells infected with viruses usually release IFNs, which induce an antiviral state in nearby cells. But vaccinia virus makes anti-IFN proteins that prevent IFN release. If the viral genes that encode these proteins are removed from the virus, the virus cannot spread through normal cells. However, many cancer cells have defective IFN signaling pathways so the virus can spread through them. IFN-β expression by the virus, however, should improve its innate anticancer effects because IFN-β stops cancer cells dividing, induces an antitumor immune response, and stops tumors developing good blood supplies.
What Did the Researchers Do and Find?
The researchers selected a vaccinia virus strain called WR-delB18R in which the B18R gene, which encodes an anti-IFN protein, had been removed from the virus. (WR is a wild-type virus.) In laboratory experiments, IFN treatment blocked the spread of WR-delB18R in normal human cells but not in human tumor cells. After being injected into the veins of tumor-bearing mice, WR-delB18R was rapidly cleared from normal tissues but persisted in the tumors. A single injection of WR-delB18R directly into the tumor killed most of the tumor cells. A similar dose injected into a vein was less effective but nevertheless increased the survival time of some of the mice by directly killing the tumor cells, by targeting the blood supply of the tumors, and by inducing antitumor immunity. Finally, when the researchers inserted the IFN-β gene into this WR-delB18R, the new virus—JX-795—was much better at killing tumors after intravenous injection than either WR or WR-delB18R.
What Do These Findings Mean?
These findings indicate that the vaccinia virus can be adapted so that it replicates only in tumor cells and kills these cells effectively after intravenous injection. In particular, they show that the strategy adopted by the researchers both optimizes the anticancer effects of the virus and minimizes viral replication in normal tissues. JX-795 is a promising oncolytic virus, therefore, particularly since vaccinia virus has been safely used for many years to vaccinate people against smallpox. Nevertheless, it will be some years before JX-795 can be used clinically. Vaccinia virus constructs like this need to be tested extensively in the laboratory and in animals before any attempt is made to test them in people and, even if they passes all these preclinical tests with flying colors, only clinical trials will reveal whether they can treat human cancer. Several related strains of vaccinia virus are currently undergoing clinical testing.
Additional Information.
Please access these Web sites via the online version of this summary at http://dx.doi.org/:10.1371/journal.pmed.0040353.
The US National Cancer Institute provides information on all aspects of cancer (in English and Spanish)
CancerQuest, from Emory University, provides information on all aspects of cancer (in several languages)
The UK charity Cancerbackup also provides information on all aspects of cancer
Wikipedia has a page on oncolytic viruses (note that Wikipedia is a free online encyclopedia that anyone can edit; available in several languages)
A short interview about oncolytic viruses with researcher Dr. John Bell is available on the Insidermedicine Web site
The Oncolytic virus Web page provides lists of oncolytic viruses classified by type
doi:10.1371/journal.pmed.0040353
PMCID: PMC2222946  PMID: 18162040
3.  Antiglioma oncolytic virotherapy: unattainable goal or a success story in the making? 
Future virology  2013;8(7):675-693.
Initial observations from as early as the mid-1800s suggested that patients suffering from hematological malignancies would transiently go into remission upon naturally contracting viral infections laid the foundation for the oncolytic virotherapy research field. Since then, research focusing on anticancer oncolytic virotherapy has rapidly evolved. Today, oncolytic viral vectors have been engineered to stimulate and manipulate the host immune system, selectively targeting tumor tissues while sparing non-neoplastic cells. Glioblastoma multiforme, the most common adult primary brain tumor, has a disasterous history. It is one of the most deadly cancers known to humankind. Over the last century our understanding of this disease has grown exponentially. However, the median survival of patients suffering from this disease has only been extended by a few months. Even with the best, most aggressive modern therapeutic approaches available, malignant gliomas are still virtually 100% fatal. Motivated by the desperate need to find effective treatment strategies, more investments have been applied to oncolytic virotherapy preclinical and clinical studies. In this review we will discuss the antiglioma oncolytic virotherapy research field. We will survey its history and the principles laid down to serve as basis for preclinical works. We will also debate the variety of viral vectors used, their clinical applications, the lessons learned from clinical trials and possible future directions.
doi:10.2217/fvl.13.47
PMCID: PMC4043995  PMID: 24910708
glioblastoma multiforme; malignant glioma; oncolytic virus; virotherapy
4.  Prospect and progress of oncolytic viruses for treating peripheral nerve sheath tumors 
Expert opinion on orphan drugs  2015;4(2):129-138.
Introduction
Peripheral nerve sheath tumors (PNSTs) are an assorted group of neoplasms originating from neuroectoderm and growing in peripheral nerves. Malignant transformation leads to a poor prognosis and is often lethal. Current treatment of PNSTs is predominantly surgical, which is often incomplete or accompanied by significant loss of function, in conjunction with radiotherapy and/or chemotherapy, for which the benefits are inconclusive. Oncolytic viruses (OVs) efficiently kill tumor cells while remaining safe for normal tissues, and are a novel antitumor therapy for patients with PNSTs.
Areas covered
Because of the low efficacy of current treatments, new therapies for PNSTs are needed. Pre-clinically, OVs have demonstrated efficacy in treating PNSTs and perineural tumor invasion, as well as safety. We will discuss the various PNSTs and their preclinical models, and the OVs being tested for their treatment, including oncolytic herpes simplex virus (HSV), adenovirus (Ad), and measles virus (MV). OVs can be ‘armed’ to express therapeutic transgenes or combined with other therapeutics to enhance their activity.
Expert opinion
Preclinical testing of OVs in PNST models has demonstrated their therapeutic potential and provided support for clinical translation. Clinical studies with other solid tumors have provided evidence that OVs are safe in patients and efficacious. The recent successful completion of a phase III clinical trial of oncolytic HSV paves the way for oncolytic virotherapy to enter clinical practice.
doi:10.1517/21678707.2016.1128322
PMCID: PMC5111812  PMID: 27867771
virotherapy; MPNST; HSV; soft tissue sarcoma
5.  Oncolytic Poxviruses 
Annual review of virology  2014;1(1):119-141.
Current standard treatments of cancer can prolong survival of many cancer patients but usually do not effectively cure the disease. Oncolytic virotherapy is an emerging therapeutic for the treatment of cancer that exploits replication-competent viruses to selectively infect and destroy cancerous cells while sparing normal cells and tissues. Clinical and/or preclinical studies on oncolytic viruses have revealed that the candidate viruses being tested in trials are remarkably safe and offer potential for treating many classes of currently incurable cancers. Among these candidates are vaccinia and myxoma viruses, which belong to the family Poxviridae and possess promising oncolytic features. This article describes poxviruses that are being developed for oncolytic virotherapy and summarizes the outcomes of both clinical and preclinical studies. Additionally, studies demonstrating superior efficacy when poxvirus oncolytic virotherapy is combined with conventional therapies are described.
doi:10.1146/annurev-virology-031413-085442
PMCID: PMC4380149  PMID: 25839047
vaccinia virus; myxoma virus; virus tropism; oncolytic; virotherapeutics; virotherapy
6.  Stem Cell-Based Cell Carrier for Targeted Oncolytic Virotherapy: Translational Opportunity and Open Questions 
Viruses  2015;7(12):6200-6217.
Oncolytic virotherapy for cancer is an innovative therapeutic option where the ability of a virus to promote cell lysis is harnessed and reprogrammed to selectively destroy cancer cells. Such treatment modalities exhibited antitumor activity in preclinical and clinical settings and appear to be well tolerated when tested in clinical trials. However, the clinical success of oncolytic virotherapy has been significantly hampered due to the inability to target systematic metastasis. This is partly due to the inability of the therapeutic virus to survive in the patient circulation, in order to target tumors at distant sites. An early study from various laboratories demonstrated that cells infected with oncolytic virus can protect the therapeutic payload form the host immune system as well as function as factories for virus production and enhance the therapeutic efficacy of oncolytic virus. While a variety of cell lineages possessed potential as cell carriers, copious investigation has established stem cells as a very attractive cell carrier system in oncolytic virotherapy. The ideal cell carrier desire to be susceptible to viral infection as well as support viral infection, maintain immunosuppressive properties to shield the loaded viruses from the host immune system, and most importantly possess an intrinsic tumor homing ability to deliver loaded viruses directly to the site of the metastasis—all qualities stem cells exhibit. In this review, we summarize the recent work in the development of stem cell-based carrier for oncolytic virotherapy, discuss the advantages and disadvantages of a variety of cell carriers, especially focusing on why stem cells have emerged as the leading candidate, and finally propose a future direction for stem cell-based targeted oncolytic virotherapy that involves its establishment as a viable treatment option for cancer patients in the clinical setting.
doi:10.3390/v7122921
PMCID: PMC4690850  PMID: 26633462
cell carrier; oncolytic virus; stem cell
7.  Mitophagy Enhances Oncolytic Measles Virus Replication by Mitigating DDX58/RIG-I-Like Receptor Signaling 
Journal of Virology  2014;88(9):5152-5164.
ABSTRACT
The success of future clinical trials with oncolytic viruses depends on the identification and the control of mechanisms that modulate their therapeutic efficacy. In particular, little is known about the role of autophagy in infection by attenuated measles virus of the Edmonston strain (MV-Edm). We investigated the interaction between autophagy, innate immune response, and oncolytic activity of MV-Edm, since the antiviral immune response is a known factor limiting virotherapies. We report that MV-Edm exploits selective autophagy to mitigate the innate immune response mediated by DDX58/RIG-I like receptors (RLRs) in non-small cell lung cancer (NSCLC) cells. Both RNA interference (RNAi) and overexpression approaches demonstrate that autophagy enhances viral replication and inhibits the production of type I interferons regulated by RLRs. We show that MV-Edm unexpectedly triggers SQSTM1/p62-mediated mitophagy, resulting in decreased mitochondrion-tethered mitochondrial antiviral signaling protein (MAVS) and subsequently weakening the innate immune response. These results unveil a novel infectious strategy based on the usurpation of mitophagy leading to mitigation of the innate immune response. This finding provides a rationale to modulate autophagy in oncolytic virotherapy.
IMPORTANCE In vitro studies, preclinical experiments in vivo, and clinical trials with humans all indicate that oncolytic viruses hold promise for cancer therapy. Measles virus of the Edmonston strain (MV-Edm), which is an attenuated virus derived from the common wild-type measles virus, is paradigmatic for therapeutic oncolytic viruses. MV-Edm replicates preferentially in and kills cancer cells. The efficiency of MV-Edm is limited by the immune response of the host against viruses. In our study, we revealed that MV-Edm usurps a homeostatic mechanism of intracellular degradation of mitochondria, coined mitophagy, to attenuate the innate immune response in cancer cells. This strategy might provide a replicative advantage for the virus against the development of antiviral immune responses by the host. These findings are important since they may not only indicate that inducers of autophagy could enhance the efficacy of oncolytic therapies but also provide clues for antiviral therapy by targeting SQSTM1/p62-mediated mitophagy.
doi:10.1128/JVI.03851-13
PMCID: PMC3993837  PMID: 24574393
8.  Oncolytic Myxoma Virus: The path to clinic 
Vaccine  2013;31(39):4252-4258.
Many common neoplasms are still noncurative with current standards of cancer therapy. More therapeutic modalities need to be developed to significantly prolong the lives of patients and eventually cure a wider spectrum of cancers. Oncolytic virotherapy is one of the promising new additions to clinical cancer therapeutics. Successful oncolytic virotherapy in the clinic will be those strategies that best combine tumor cell oncolysis with enhanced immune responses against tumor antigens. The current candidate oncolytic viruses all share the common property that they are relatively nonpathogenic to humans, yet they have the ability to replicate selectively in human cancer cells and induce cancer regression by direct oncolysis and/or induction of improved anti-tumor immune responses. Many candidate oncolytic viruses are in various stages of clinical and preclinical development. One such preclinical candidate is myxoma virus (MYXV), a member of the Poxviridae family that, in its natural setting, exhibits a very restricted host range and is only pathogenic to European rabbits. Despite its narrow host range in nature, MYXV has been shown to productively infect various classes of human cancer cells. Several preclinical in vivo modeling studies have demonstrated that MYXV is an attractive and safe candidate oncolytic virus, and hence, MYXV is currently being developed as a potential therapeutic for several cancers, such as pancreatic cancer, glioblastoma, ovarian cancer, melanoma, and hematologic malignancies. This review highlights the preclinical cancer models that have shown the most promise for translation of MYXV into human clinical trials.
doi:10.1016/j.vaccine.2013.05.056
PMCID: PMC3755036  PMID: 23726825
Myxoma Virus; Oncolytic Virotherapy; Hematological Malignancies; Pancreatic Cancer
9.  Oncolytic herpes simplex virus vectors and chemotherapy: are combinatorial strategies more effective for cancer? 
Despite aggressive treatments, including chemotherapy and radiotherapy, cancers often recur owing to resistance to conventional therapies. Oncolytic viruses such as oncolytic herpes simplex virus (oHSV) represent an exciting biological approach to cancer therapy. A range of viral mutations has been engineered into HSV to engender oncolytic activity. While oHSV as a single agent has been tested in a number of cancer clinical trials, preclinical studies have demonstrated enhanced efficacy when it is combined with cytotoxic anticancer drugs. Among the strategies that will be discussed in this article are combinations with standard-of-care chemotherapeutics, expression of prodrug-activating enzymes to enhance chemotherapy and small-molecule inhibitors. The combination of oHSV and chemotherapy can achieve much more efficient cancer cell killing than either single agent alone, often through synergistic interactions. This can be clinically important not just for improving efficacy but also for permitting lower and less toxic chemotherapeutic doses. The viral mutations in an oHSV vector often determine the favorability of its interactions with chemotherapy, just as different cancer cells, due to genetic alterations, vary in their response to chemotherapy. As chemotherapeutics are often the standard of care, combining them with an investigational new drug, such as oHSV, is clinically easier than combining multiple novel agents. As has become clear for most cancer therapies, multimodal treatments are usually more effective. In this article, we will discuss the recent progress of these combinatorial strategies between virotherapy and chemotherapy and future directions.
doi:10.2217/fon.10.18
PMCID: PMC2904234  PMID: 20373873
cancer drug; chemotherapeutics; combination therapy; herpes simplex virus; oncolytic virus; prodrug activation; virotherapy
10.  Trial watch 
Oncoimmunology  2013;2(6):e24612.
Oncolytic virotherapy is emerging as a promising approach for the treatment of several neoplasms. The term “oncolytic viruses” is generally employed to indicate naturally occurring or genetically engineered attenuated viral particles that cause the demise of malignant cells while sparing their non-transformed counterparts. From a conceptual standpoint, oncolytic viruses differ from so-called “oncotropic viruses” in that only the former are able to kill cancer cells, even though both display a preferential tropism for malignant tissues. Of note, such a specificity can originate at several different steps of the viral cycle, including the entry of virions (transductional specificity) as well as their intracellular survival and replication (post-transcriptional and transcriptional specificity). During the past two decades, a large array of replication-competent and replication-incompetent oncolytic viruses has been developed and engineered to express gene products that would specifically promote the death of infected (cancer) cells. However, contrarily to long-standing beliefs, the antineoplastic activity of oncolytic viruses is not a mere consequence of the cytopathic effect, i.e., the lethal outcome of an intense, productive viral infection, but rather involves the elicitation of an antitumor immune response. In line with this notion, oncolytic viruses genetically modified to drive the local production of immunostimulatory cytokines exert more robust therapeutic effects than their non-engineered counterparts. Moreover, the efficacy of oncolytic virotherapy is significantly improved by some extent of initial immunosuppression (facilitating viral replication and spread) followed by the administration of immunostimulatory molecules (boosting antitumor immune responses). In this Trial Watch, we will discuss the results of recent clinical trials that have evaluated/are evaluating the safety and antineoplastic potential of oncolytic virotherapy.
doi:10.4161/onci.24612
PMCID: PMC3716755  PMID: 23894720
GM-CSF; HSV; immunotherapy; JX594; reolysin; talimogene laherparepvec
11.  Progress in oncolytic virotherapy for the treatment of thyroid malignant neoplasm 
Thyroid malignant neoplasm develops from follicular or parafollicular thyroid cells. A higher proportion of anaplastic thyroid cancer has an adverse prognosis. New drugs are being used in clinical treatment. However, for advanced thyroid malignant neoplasm such as anaplastic thyroid carcinoma, the major impediment to successful control of the disease is the absence of effective therapies. Oncolytic virotherapy has significantly progressed as therapeutics in recent years. The advance is that oncolytic viruses can be designed with biological specificity to infect, replicate and lyse tumor cells. Significant advances in virotherapy have being achieved to improve the accessibility, safety and efficacy of the treatment. Therefore, it is necessary to summarize and bring together the main areas covered by these investigations for the virotherapy of thyroid malignant neoplasm. We provide an overview of the progress in virotherapy research and clinical trials, which employ virotherapy for thyroid malignant neoplasm as well as the future prospect for virotherapy of thyroid malignant neoplasms.
doi:10.1186/s13046-014-0091-8
PMCID: PMC4242545  PMID: 25366264
Oncolytic virotherapy; Thyroid malignant neoplasm; Thyroid cell biomarker
12.  Clinical testing of engineered oncolytic measles virus strains in the treatment of cancer: An overview 
Viruses have adapted through millennia of evolution to effectively invade and lyse cells through diverse mechanisms. Strains of the attenuated measles virus Edmonston (MV-Edm) vaccine lineage can preferentially infect and destroy cancerous cells while sparing the surrounding tissues. This specificity is predominantly due to overexpression of the measles virus receptor CD46 in tumor cells. To facilitate in vivo monitoring of viral gene expression and replication, these oncolytic strains have been engineered to either express soluble marker peptides, such as the human carcinoembryonic antigen (CEA; MV-CEA virus), or genes that facilitate imaging and therapy, such as the human thyroidal sodium iodide symporter (NIS) gene (MV-NIS). Preclinical efficacy and safety data for engineered oncolytic MV-Edm derivatives that led to their clinical translation are discussed in this review, and an overview of the early experience in three ongoing clinical trials of patients with ovarian cancer, glioblastoma multiforme and multiple myeloma is provided. The information obtained from these ongoing trials will guide the future clinical application and further development of MV strains as anticancer agents.
PMCID: PMC2717625  PMID: 19169959
Brain tumor; clinical trial; measles virus; multiple myeloma; ovarian cancer; virotherapy
13.  Replicating viral vectors for cancer therapy: strategies to synergize with host immune responses 
Microbial biotechnology  2012;5(2):251-259.
Summary
Tumour‐specific replicating (oncolytic) viruses are novel anticancer agents, currently under intense investigation in preclinical studies and phase I–III clinical trials. Until recently, most studies have focused on the direct antitumour properties of these viruses. There is now an increasing body of evidence indicating that host immune responses may be critical to the efficacy of oncolytic virotherapy. Although the immune response to oncolytic viruses can rapidly restrict viral replication, thereby limiting the efficacy of therapy, oncolytic virotherapy also has the potential to induce potent antitumoural immune effectors that destroy those cancer cells, which are not directly lysed by virus. In this review, we discuss the role of the immune system in terms of antiviral and antitumoural responses, as well as strategies to evade or promote these responses in favour of improved therapeutic potentials.
doi:10.1111/j.1751-7915.2011.00296.x
PMCID: PMC3815785  PMID: 21923638
14.  Novel oncolytic viral therapies in patients with thoracic malignancies 
Oncolytic Virotherapy  2016;6:1-9.
Oncolytic virotherapy is the use of replication-competent viruses to treat malignancies. The potential of oncolytic virotherapy as an approach to cancer therapy is based on historical evidence that certain viral infections can cause spontaneous remission of both hematologic and solid tumor malignancies. Oncolytic virotherapy may eliminate cancer cells through either direct oncolysis of infected tumor cells or indirect immune-mediated oncolysis of uninfected tumor cells. Recent advances in oncolytic virotherapy include the development of a wide variety of genetically attenuated RNA viruses with precise cellular tropism and the identification of cell-surface receptors that facilitate viral transfer to the tissue of interest. Current research is also focused on targeting metastatic disease by sustaining the release of progeny viruses from infected tumor cells and understanding indirect tumor cell killing through immune-mediated mechanisms of virotherapy. The purpose of this review is to critically evaluate recent evidence on the clinical development of tissue-specific viruses capable of targeting tumor cells and eliciting secondary immune responses in lung cancers and mesothelioma.
doi:10.2147/OV.S116012
PMCID: PMC5189707  PMID: 28053943
lung cancer; mesothelioma; VSV; adenovirus; measles
15.  Potent systemic therapy of Multiple Myeloma utilizing Oncolytic Vesicular stomatitis virus coding for Interferon-beta 
Cancer gene therapy  2012;19(7):443-450.
Multiple myeloma (MM) is an incurable malignancy of plasma secreting B-cells disseminated in the bone marrow. Successful utilization of oncolytic virotherapy for myeloma treatment requires a systemically administered virus that selectively destroys disseminated myeloma cells in an immune-competent host. Vesicular stomatitis virus (VSV) expressing Interferon-β (IFNβ) is a promising new oncolytic agent that exploits tumor-associated defects in innate immune signaling pathways to specifically destroy cancer cells. We demonstrate here that a single, intravenous dose of VSV-IFNβ specifically destroys subcutaneous and disseminated 5TGM1 myeloma in an immune competent myeloma model. VSV-IFN treatment significantly prolonged survival in mice bearing orthotopic myeloma. Viral murine IFNβ expression further delayed myeloma progression and significantly enhanced survival compared to VSV expressing human IFNβ. Evaluation of VSV-IFNβ oncolytic activity in human myeloma cell lines and primary patient samples confirmed myeloma specific oncolytic activity but revealed variable susceptibility to VSV-IFNβ oncolysis. The results indicate that VSV-IFNβ is a potent, safe oncolytic agent that can be systemically administered to effectively target and destroy disseminated myeloma in immune competent mice. IFNβ expression improves cancer specificity and enhances VSV therapeutic efficacy against disseminated myeloma. These data show VSV-IFNβ to be a promising vector for further development as a potential therapy for treatment of Multiple myeloma.
doi:10.1038/cgt.2012.14
PMCID: PMC3380174  PMID: 22522623
Oncolytic; virotherapy; myeloma; Vesicular stomatitis virus; systemic
16.  Economic evaluation of therapies for patients suffering from relapsed-refractory multiple myeloma in Greece 
Background
Multiple myeloma is a hematologic malignancy that incurs a substantial economic burden in care management. Since most patients with multiple myeloma eventually relapse or become refractory to current therapies (rrMM), the aim of this study was to assess the cost-effectiveness of the combination of lenalidomide–dexamethasone, relative to bortezomib alone, in patients suffering from rrMM in Greece.
Methods
An international discrete event simulation model was locally adapted to estimate differences in overall survival and treatment costs associated with the two alternative treatment options. The efficacy data utilized came from three international trials (MM-009, MM-010, APEX). Quality of life data were extracted from the published literature. Data on resource use and prices came from relevant local sources and referred to 2012. The perspective of the analysis was that of public providers. Total costs for monitoring and administration of therapy to patients, management of adverse events, and cost of medication were captured. A 3.5% discount rate was used for costs and health outcomes. A Monte Carlo simulation was used to estimate probabilistic results with 95% uncertainty intervals (UI) and a cost-effectiveness acceptability curve.
Results
The mean number of quality-adjusted life years (QALYs) was 3.01 (95% UI 2.81–3.20) and 2.22 (95% UI 2.02–2.41) for lenalidomide–dexamethasone and bortezomib, respectively, giving an incremental gain of 0.79 (95% UI 0.49–1.06) QALYs in favor of lenalidomide–dexamethasone. The mean cost of therapy per patient was estimated at €80;77,670 (95% UI €80;76,509–€80;78,900) and €80;48,928 (95% UI €80;48,300–€80;49,556) for lenalidomide–dexamethasone and bortezomib, respectively. The incremental cost per life year gained with lenalidomide–dexamethasone was estimated at €80;29,415 (95% UI €80;23,484–€80;37,583) and the incremental cost per QALY gained at €80;38,268 (95% UI €80;27,001–€80;58,065). The probability of lenalidomide–dexamethasone being a cost-effective therapy option at a threshold three times the per capita income (€80;60,000 per QALY) was higher than 95%. The results remained constant, without altering the conclusions, under several hypothetical scenarios.
Conclusion
The combination of lenalidomide and dexamethasone may represent a cost-effective choice relative to bortezomib monotherapy for patients in Greece with previously treated multiple myeloma.
doi:10.2147/CMAR.S43373
PMCID: PMC3627436  PMID: 23596356
multiple myeloma; economic evaluation; lenalidomide; dexamethasone; bortezomib
17.  Oncolytic virotherapy for human malignant mesothelioma: recent advances 
Oncolytic Virotherapy  2015;4:133-140.
Cancer virotherapy is an attractive alternative to conventional treatments because it offers a wide range of antitumor effects due to 1) the diversity of the oncolytic viruses that are now available and 2) their multifaceted activities against both tumor cells and tumor vessels, in addition to their ability to induce antitumor immune responses. In this review, we summarize preclinical and clinical data regarding the targeting of malignant mesothelioma (MM) by oncolytic viruses. We also discuss the potential of other oncolytic viruses that have already shown antitumor effects against several malignancies in advanced clinical trials but are yet to be tested against MM cells. Finally, we review how the activation of the immune system and combinations with other types of anticancer treatments could support the development of oncolytic virotherapy for the treatment of MM.
doi:10.2147/OV.S66091
PMCID: PMC4918388  PMID: 27512676
oncolytic viruses; cancer virotherapy; malignant mesothelioma; antitumor immune responses; immunotherapy
18.  Treatment of medulloblastoma with oncolytic measles viruses expressing the angiogenesis inhibitors endostatin and angiostatin 
BMC Cancer  2014;14:206.
Background
Medulloblastoma is the most common type of pediatric brain tumor. Although numerous factors influence patient survival rates, more than 30% of all cases will ultimately be refractory to conventional therapies. Current standards of care are also associated with significant morbidities, giving impetus for the development of new treatments. We have previously shown that oncolytic measles virotherapy is effective against medulloblastoma, leading to significant prolongation of survival and even cures in mouse xenograft models of localized and metastatic disease. Because medulloblastomas are known to be highly vascularized tumors, we reasoned that the addition of angiogenesis inhibitors could further enhance the efficacy of oncolytic measles virotherapy. Toward this end, we have engineered an oncolytic measles virus that express a fusion protein of endostatin and angiostatin, two endogenous and potent inhibitors of angiogenesis.
Methods
Oncolytic measles viruses encoding human and mouse variants of a secretable endostatin/angiostatin fusion protein were designed and rescued according to established protocols. These viruses, known as MV-hE:A and MV-mE:A respectively, were then evaluated for their anti-angiogenic potential and efficacy against medulloblastoma cell lines and orthotopic mouse models of localized disease.
Results
Medulloblastoma cells infected by MV-E:A readily secrete endostatin and angiostatin prior to lysis. The inclusion of the endostatin/angiostatin gene did not negatively impact the measles virus’ cytotoxicity against medulloblastoma cells or alter its growth kinetics. Conditioned media obtained from these infected cells was capable of inhibiting multiple angiogenic factors in vitro, significantly reducing endothelial cell tube formation, viability and migration compared to conditioned media derived from cells infected by a control measles virus. Mice that were given a single intratumoral injection of MV-E:A likewise showed reduced numbers of tumor-associated blood vessels and a trend for increased survival compared to mice treated with the control virus.
Conclusions
These data suggest that oncolytic measles viruses encoding anti-angiogenic proteins may have therapeutic benefit against medulloblastoma and support ongoing efforts to target angiogenesis in medulloblastoma.
doi:10.1186/1471-2407-14-206
PMCID: PMC3995427  PMID: 24646176
Oncolytic measles virus; Angiogenesis; Endostatin; Angiostatin; Medulloblastoma
19.  Oncosuppressive Suicide Gene Virotherapy “PVH1-yCD/5-FC” for Pancreatic Peritoneal Carcinomatosis Treatment: NFκB and Akt/PI3K Involvement 
PLoS ONE  2013;8(8):e70594.
Peritoneal carcinomatosis is common in advanced pancreatic cancer. Despite current standard treatment, patients with this disease until recently were considered incurable. Cancer gene therapy using oncolytic viruses have generated much interest over the past few years. Here, we investigated a new gene directed enzyme prodrug therapy (GDEPT) approach for an oncosuppressive virotherapy strategy using parvovirus H1 (PV-H1) which preferentially replicates and kills malignant cells. Although, PV-H1 is not potent enough to destroy tumors, it represents an attractive vector for cancer gene therapy. We therefore sought to determine whether the suicide gene/prodrug system, yCD/5-FC could be rationally combined to PV-H1 augmenting its intrinsic oncolytic activity for pancreatic cancer prevention and treatment. We showed that the engineered recombinant parvovirus rPVH1-yCD with 5-FC treatment increased significantly the intrinsic cytotoxic effect and resulted in potent induction of apoptosis and tumor growth inhibition in chemosensitive and chemoresistant cells. Additionally, the suicide gene-expressing PV-H1 infection reduced significantly the constitutive activities of NFκB and Akt/PI3K. Combination of their pharmacological inhibitors (MG132 and LY294002) with rPVH1-yCD/5-FC resulted in substantial increase of antitumor activity. In vivo, high and sustained expression of NS1 and yCD was observed in the disseminated tumor nodules and absent in normal tissues. Treatment of mice bearing intraperitoneal pancreatic carcinomatosis with rPVH1-yCD/5-FC resulted in a drastic inhibition of tumor cell spreading and subsequent increase in long-term survival. Together, the presented data show the improved oncolytic activity of wPV-H1 by yCD/5-FC and thus provides valuable effective and promising virotherapy strategy for prevention of tumor recurrence and treatment. In the light of this study, the suicide gene parvovirotherapy approach represents a new weapon in the war against pancreatic cancer. Moreover, these preliminary accomplishments are opening new field for future development of new combined targeted therapies to have a meaningful impact on advanced cancer.
doi:10.1371/journal.pone.0070594
PMCID: PMC3743896  PMID: 23967078
20.  Targeting tumor vasculature through oncolytic virotherapy: recent advances 
Oncolytic Virotherapy  2015;4:169-181.
The oncolytic virotherapy field has made significant advances in the last decade, with a rapidly increasing number of early- and late-stage clinical trials, some of them showing safety and promising therapeutic efficacy. Targeting tumor vasculature by oncolytic viruses (OVs) is an attractive strategy that offers several advantages over nontargeted viruses, including improved tumor viral entry, direct antivascular effects, and enhanced antitumor efficacy. Current understanding of the biological mechanisms of tumor neovascularization, novel vascular targets, and mechanisms of resistance has allowed the development of oncolytic viral vectors designed to target tumor neovessels. While some OVs (such as vaccinia and vesicular stomatitis virus) can intrinsically target tumor vasculature and induce vascular disruption, the majority of reported vascular-targeted viruses are the result of genetic manipulation of their viral genomes. Such strategies include transcriptional or transductional endothelial targeting, “armed” viruses able to downregulate angiogenic factors, or to express antiangiogenic molecules. The above strategies have shown preclinical safety and improved antitumor efficacy, either alone, or in combination with standard or targeted agents. This review focuses on the recent efforts toward the development of vascular-targeted OVs for cancer treatment and provides a translational/clinical perspective into the future development of new generation biological agents for human cancers.
doi:10.2147/OV.S66045
PMCID: PMC4918394  PMID: 27512680
vascular targeting; oncolytic virus; tumor angiogenesis
21.  Oncolytic virus therapy: A new era of cancer treatment at dawn 
Cancer Science  2016;107(10):1373-1379.
Oncolytic virus therapy is perhaps the next major breakthrough in cancer treatment following the success in immunotherapy using immune checkpoint inhibitors. Oncolytic viruses are defined as genetically engineered or naturally occurring viruses that selectively replicate in and kill cancer cells without harming the normal tissues. T‐Vec (talimogene laherparepvec), a second‐generation oncolytic herpes simplex virus type 1 (HSV‐1) armed with GM‐CSF, was recently approved as the first oncolytic virus drug in the USA and Europe. The phase III trial proved that local intralesional injections with T‐Vec in advanced malignant melanoma patients can not only suppress the growth of injected tumors but also act systemically and prolong overall survival. Other oncolytic viruses that are closing in on drug approval in North America and Europe include vaccinia virus JX‐594 (pexastimogene devacirepvec) for hepatocellular carcinoma, GM‐CSF‐expressing adenovirus CG0070 for bladder cancer, and Reolysin (pelareorep), a wild‐type variant of reovirus, for head and neck cancer. In Japan, a phase II clinical trial of G47∆, a third‐generation oncolytic HSV‐1, is ongoing in glioblastoma patients. G47∆ was recently designated as a “Sakigake” breakthrough therapy drug in Japan. This new system by the Japanese government should provide G47∆ with priority reviews and a fast‐track drug approval by the regulatory authorities. Whereas numerous oncolytic viruses have been subjected to clinical trials, the common feature that is expected to play a major role in prolonging the survival of cancer patients is an induction of specific antitumor immunity in the course of tumor‐specific viral replication. It appears that it will not be long before oncolytic virus therapy becomes a standard therapeutic option for all cancer patients.
doi:10.1111/cas.13027
PMCID: PMC5084676  PMID: 27486853
Clinical trial; G47∆; herpes simplex virus; oncolytic immunotherapy; oncolytic virus
22.  ONCOLYTIC VIROTHERAPY 
Nature biotechnology  2012;30(7):658-670.
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.
doi:10.1038/nbt.2287
PMCID: PMC3888062  PMID: 22781695
23.  Use of lenalidomide in the management of relapsed or refractory multiple myeloma: expert recommendations in Korea 
Blood research  2015;50(1):7-18.
Multiple myeloma (MM) is the third most common hematologic malignancy in Korea. Historically, the incidence of MM in Korea has been lower than that in Western populations, although there is growing evidence that the incidence of MM in Asian populations, including Korea, is increasing rapidly. Despite advances in the management of MM, patients will ultimately relapse or become refractory to their current treatment, and alternative therapeutic options are required in the relapsed/refractory setting. In Korea, although lenalidomide/dexamethasone is indicated for the treatment of relapsed or refractory MM (RRMM) in patients who have received at least one prior therapy, lenalidomide is reimbursable specifically only in patients with RRMM who have failed bortezomib-based treatment. Based on evidence from pivotal multinational clinical trials as well as recent studies in Asia, including Korea, lenalidomide/dexamethasone is an effective treatment option for patients with RRMM, regardless of age or disease status. Adverse events associated with lenalidomide/dexamethasone, including hematologic toxicity, venous thromboembolism, fatigue, rash, infection, and muscle cramps, are largely predictable and preventable/manageable with appropriate patient monitoring and/or the use of standard supportive medication and dose adjustment/interruption. Lenalidomide/dexamethasone provides an optimal response when used at first relapse, and treatment should be continued long term until disease progression. With appropriate modification of the lenalidomide starting dose, lenalidomide/dexamethasone is effective in patients with renal impairment and/or cytopenia. This review presents updated evidence from the published clinical literature and provides recommendations from an expert panel of Korean physicians regarding the use of lenalidomide/dexamethasone in patients with RRMM.
doi:10.5045/br.2015.50.1.7
PMCID: PMC4377347  PMID: 25830125
Guideline; Korea; Lenalidomide; Multiple myeloma; Refractory; Relapsed
24.  Applications of coxsackievirus A21 in oncology 
Oncolytic Virotherapy  2014;3:47-55.
The clinical management of cancer continues to be dominated by macroscopic surgical resection, radiotherapy, and cytotoxic drugs. The major challenge facing oncology is to achieve more selective, less toxic and effective methods of targeting disseminated tumors, a challenge oncolytic virotherapy may be well-placed to meet. Characterization of coxsackievirus A21 (CVA21) receptor-based mechanism of virus internalization and lysis in the last decade has suggested promise for CVA21 as a virotherapy against malignancies which overexpress those receptors. Preclinical studies have demonstrated proof of principle, and with the results of early clinical trials awaited, CVA21 may be one of the few viruses to demonstrate benefit for patients. This review outlines the potential of CVA21 as an oncolytic agent, describing the therapeutic development of CVA21 in preclinical studies and early stage clinical trials. Preclinical evidence supports the potential use of CVA21 across a range of malignancies. Malignant melanoma is the most intensively studied cancer, and may represent a “test case” for future development of the virus. Although there are theoretical barriers to the clinical utility of oncolytic viruses like CVA21, whether these will block the efficacy of the virus in clinical practice remains to be established, and is a question which can only be answered by appropriate trials. As these data become available, the rapid journey of CVA21 from animal studies to clinical trials may offer a model for the translation of other oncolytic virotherapies from laboratory to clinic.
doi:10.2147/OV.S56322
PMCID: PMC4918364  PMID: 27512662
coxsackievirus A21; CVA21; cavatak; oncolytic virotherapy
25.  Oncolytic Polio Virotherapy of Cancer 
Cancer  2014;120(21):3277-3286.
Recently, the century-old idea of targeting cancer with viruses (‘oncolytic viruses’) has come of age, with promise documented in early-stage and several late-stage clinical trials in a variety of cancers. While originally prized for their direct tumor cytotoxicity (‘oncolytic virotherapy’), recently, the pro-inflammatory and immunogenic effects of viral tumor infection (‘oncolytic immunotherapy’) have come into focus. Indeed, a capacity for eliciting broad, sustained anti-neoplastic effects stemming from combined direct viral cytotoxicity, innate antiviral activation, stromal pro-inflammatory stimulation and recruitment of adaptive immune effector responses is the greatest asset of oncolytic viruses. However, it also is the source for enormous mechanistic complexity that must be considered for successful clinical translation. Due to fundamentally different relationships with their hosts (malignant or not), diverse replication strategies and distinct modes of tumor cytotoxicity/ killing, oncolytic viruses should not be referred to collectively. These agents must be evaluated based on their individual merits. In this review, we highlight key mechanistic principles of cancer treatment with the polio:rhinovirus chimera PVSRIPO, and their implications for oncolytic immunotherapy in the clinic.
doi:10.1002/cncr.28862
PMCID: PMC4205207  PMID: 24939611
poliovirus; oncolytic virus; IRES; Necl5; CD155; translation; innate antiviral response; interferon; eIF4G

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