Chimeric HCMV/HSV-1 and Δγ134.5 oncolytic herpes simplex virus elicit immune mediated antigliomal effect and antitumor memory

CAR T-cell and oncolytic virus dynamics and determinants of combination therapy success for glioblastoma

Glioblastoma is a highly aggressive and treatment-resistant primary brain cancer. While chimeric antigen receptor (CAR) T-cell therapy has demonstrated promising results in targeting these tumors, it has not yet been curative. An innovative approach to improve CAR T-cell efficacy is to combine them with other immune modulating therapies. In this study, we investigate in vitro combination of IL-13Rα2 targeted CAR T-cells with an oncolytic virus (OV) and study the complex interplay between tumor cells, CAR T-cells, and OV dynamics with a novel mathematical model. We fit the model to data collected from experiments with each therapy individually and in combination to reveal determinants of therapy synergy and improved efficacy. Our analysis reveals that the virus bursting size is a critical parameter in determining the net tumor infection rate and overall combination treatment efficacy. Moreover, the model predicts that administering the oncolytic virus simultaneously with, or prior to, CAR T-cells could maximize therapeutic efficacy.

Understanding the interplay between oHSV and the host immune system: Implications for therapeutic oncolytic virus development

Oncolytic herpes simplex viruses (oHSV) preferentially replicate in cancer cells while inducing antitumor immunity, and thus, they are often referred to as in situ cancer vaccines. OHSV infection of tumors elicits diverse host immune responses comprising both innate and adaptive components. Although the innate and adaptive immune responses primarily target the tumor, they also contribute to antiviral immunity, limiting viral replication/oncolysis. OHSV-encoded proteins use various mechanisms to evade host antiviral pathways and immune recognition, favoring oHSV replication, oncolysis, and spread. In general, oHSV infection and replication within tumors results in a series of sequential events, such as oncolysis and release of tumor and viral antigens, dendritic cell-mediated antigen presentation, T cell priming and activation, T cell trafficking and infiltration to tumors, and T cell recognition of cancer cells, leading to tumor (and viral) clearance. These sequential events align with all steps of the cancer-immunity cycle. However, a comprehensive understanding of the interplay between oHSV and host immune responses is crucial to optimize oHSV-induced antitumor immunity and efficacy. Therefore, this review aims to elucidate oHSV's communication with innate and adaptive immune systems and use such interactions to improve oHSV's potential as a potent immunovirotherapeutic agent against cancer.

Enhanced IL-12 transgene expression improves oncolytic viroimmunotherapy

Introduction

Malignant peripheral nerve sheath tumors (MPNSTs) are aggressive sarcomas with unacceptably low cure rates occurring often in patients with neurofibromatosis 1 defects. To investigate oncolytic Herpes Simplex Virus (oHSV) as an immunotherapeutic approach, we compared viral replication, functional activity, and immune response between unarmed and interleukin 12 (IL-12)-armed oncolytic viruses in virus-permissive (B109) and -resistant (67C-4) murine MPNSTs.

Methods

This study compared two attenuated IL-12-oHSVs with γ134.5 gene deletions (Δγ134.5) and the same transgene expression cassette. The primary difference in the IL-12-oHSVs was in their ability to counter the translational arrest response in infected cells. Unlike M002 (Δγ134.5, mIL-12), C002 (Δγ134.5, mIL-12, IRS1) expresses an HCMV IRS1 gene and evades dsRNA activated translational arrest in infected cells.

Results and discussion

Our results show that oHSV replication and gene expression results in vitro were not predictive of oHSV direct oncolytic activity in vivo. Tumors that supported viral replication in cell culture studies resisted viral replication by both oHSVs and restricted M002 transgene expression in vivo. Furthermore, two IL-12-oHSVs with equivalent transcriptional activity differed in IL-12 protein production in vivo, and the differences in IL-12 protein levels were reflected in immune infiltrate activity changes as well as tumor growth suppression differences between the IL-12-oHSVs. C002-treated tumors exhibited sustained IL-12 production with improved dendritic cells, monocyte-macrophage activity (MHCII, CD80/CD86 upregulation) and a polyfunctional Th1-cell response in the tumor infiltrates.

Conclusion

These results suggest that transgene protein production differences between oHSVs in vivo, in addition to replication differences, can impact OV-therapeutic activity.

OV Modulators of the Paediatric Brain TIME: Current Status, Combination Strategies, Limitations and Future Directions

Oncolytic viruses (OVs) are characterised by their preference for infecting and replicating in tumour cells either naturally or after genetic modification, resulting in oncolysis. Furthermore, OVs can elicit both local and systemic anticancer immune responses while specifically infecting and lysing tumour cells. These characteristics render them a promising therapeutic approach for paediatric brain tumours (PBTs). PBTs are frequently marked by a cold tumour immune microenvironment (TIME), which suppresses immunotherapies. Recent preclinical and clinical studies have demonstrated the capability of OVs to induce a proinflammatory immune response, thereby modifying the TIME. In-depth insights into the effect of OVs on different cell types in the TIME may therefore provide a compelling basis for using OVs in combination with other immunotherapy modalities. However, certain limitations persist in our understanding of oncolytic viruses' ability to regulate the TIME to enhance anti-tumour activity. These limitations primarily stem from the translational limitations of model systems, the difficulties associated with tracking reliable markers of efficacy throughout the course of treatment and the role of pre-existing viral immunity. In this review, we describe the different alterations observed in the TIME in PBTs due to OV treatment, combination therapies of OVs with different immunotherapies and the hurdles limiting the development of effective OV therapies while suggesting future directions based on existing evidence.

Joining Forces: The Combined Application of Therapeutic Viruses and Nanomaterials in Cancer Therapy

Cancer, on a global scale, presents a monumental challenge to our healthcare systems, posing a significant threat to human health. Despite the considerable progress we have made in the diagnosis and treatment of cancer, realizing precision cancer therapy, reducing side effects, and enhancing efficacy remain daunting tasks. Fortunately, the emergence of therapeutic viruses and nanomaterials provides new possibilities for tackling these issues. Therapeutic viruses possess the ability to accurately locate and attack tumor cells, while nanomaterials serve as efficient drug carriers, delivering medication precisely to tumor tissues. The synergy of these two elements has led to a novel approach to cancer treatment-the combination of therapeutic viruses and nanomaterials. This advantageous combination has overcome the limitations associated with the side effects of oncolytic viruses and the insufficient tumoricidal capacity of nanomedicines, enabling the oncolytic viruses to more effectively breach the tumor's immune barrier. It focuses on the lesion site and even allows for real-time monitoring of the distribution of therapeutic viruses and drug release, achieving a synergistic effect. This article comprehensively explores the application of therapeutic viruses and nanomaterials in tumor treatment, dissecting their working mechanisms, and integrating the latest scientific advancements to predict future development trends. This approach, which combines viral therapy with the application of nanomaterials, represents an innovative and more effective treatment strategy, offering new perspectives in the field of tumor therapy.

Oncolytic virus-driven immune remodeling revealed in mouse medulloblastomas at single cell resolution

Oncolytic viruses, modified for tumor-restricted infection, are a promising cancer immunotherapeutic, yet much remains to be understood about factors driving their activity and outcome in the tumor microenvironment. Here, we report that oncolytic herpes simplex virus C134, previously found to exert T cell-dependent efficacy in mouse models of glioblastoma, exerts T cell-independent efficacy in mouse models of medulloblastoma, indicating this oncolytic virus uses different mechanisms in different tumors. We investigated C134's behavior in mouse medulloblastomas, using single cell RNA sequencing to map C134-induced gene expression changes across cell types, timepoints, and medulloblastoma subgroup models at whole-transcriptome resolution. Our work details substantial oncolytic virus-induced transcriptional remodeling of medulloblastoma-infiltrating immune cells, 10 subpopulations of monocytes and macrophages collectively demonstrating M1-like responses to C134, and suggests C134 be investigated as a potential new therapy for medulloblastoma.

Development and application of oncolytic viruses as the nemesis of tumor cells

Viruses and tumors are two pathologies that negatively impact human health, but what occurs when a virus encounters a tumor? A global consensus among cancer patients suggests that surgical resection, chemotherapy, radiotherapy, and other methods are the primary means to combat cancer. However, with the innovation and development of biomedical technology, tumor biotherapy (immunotherapy, molecular targeted therapy, gene therapy, oncolytic virus therapy, etc.) has emerged as an alternative treatment for malignant tumors. Oncolytic viruses possess numerous anti-tumor properties, such as directly lysing tumor cells, activating anti-tumor immune responses, and improving the tumor microenvironment. Compared to traditional immunotherapy, oncolytic virus therapy offers advantages including high killing efficiency, precise targeting, and minimal side effects. Although oncolytic virus (OV) therapy was introduced as a novel approach to tumor treatment in the 19th century, its efficacy was suboptimal, limiting its widespread application. However, since the U.S. Food and Drug Administration (FDA) approved the first OV therapy drug, T-VEC, in 2015, interest in OV has grown significantly. In recent years, oncolytic virus therapy has shown increasingly promising application prospects and has become a major research focus in the field of cancer treatment. This article reviews the development, classification, and research progress of oncolytic viruses, as well as their mechanisms of action, therapeutic methods, and routes of administration.

Gospel of malignant Glioma: Oncolytic virus therapy

Glioma accounts for nearly 80% of all intracranial malignant tumors. It is a major challenge to society as it is causes to impaired brain function in many patients. Currently, gliomas are mainly treated with surgery, postoperative radiotherapy, and chemotherapy. However, the curative effects of these treatments are not satisfactory. Oncolytic virus (OV) is a novel treatment which works by activating the immune functions and inducing apoptosis of tumor cells. The OV propagates indefinitely in the host cell, eventually leading to the death of host cell. Subsequently, a large number of antigens and signal molecules are released which exert antitumor immunity. Several preclinical and clinical studies have shown that G207, DNX2401, Zika and other viruses have important roles in malignant tumors. For example, these viruses can reduce the growth of tumor cells without causing severe complications. However, the known OVs have not been clearly classified. Herein, we divided OVs into neurotropic and non-neurophilic OVs based on whether the OVs are naturally neurotropic or not. The therapeutic effects of each group were compared. Finally, challenges encountered in the clinical application of OVs in the treatment of malignant gliomas were summarized.

Targeting High-Risk Neuroblastoma Patient-Derived Xenografts with Oncolytic Virotherapy

Cancer is the leading cause of death by disease in children, and over 15% of pediatric cancer-related mortalities are due to neuroblastoma. Current treatment options for neuroblastoma remain suboptimal as they often have significant toxicities, are associated with long-term side effects, and result in disease relapse in over half of children with high-risk disease. There is a dire need for new therapies, and oncolytic viruses may represent an effective solution. Oncolytic viruses attack tumor cells in two ways: direct infection of tumor cells leading to cytolysis, and production of a debris field that stimulates an anti-tumor immune response. Our group has previously shown that M002, an oncolytic herpes simplex virus (oHSV), genetically engineered to express murine interleukin-12 (mIL-12), was effective at targeting and killing long term passage tumor cell lines. In the current study, we investigated M002 in three neuroblastoma patient-derived xenografts (PDXs). PDXs better recapitulate the human condition, and these studies were designed to gather robust data for translation to a clinical trial. We found that all three PDXs expressed viral entry receptors, and that the virus actively replicated in the cells. M002 caused significant tumor cell death in 2D culture and 3D bioprinted tumor models. Finally, the PDXs displayed variable susceptibility to M002, with a more profound effect on high-risk neuroblastoma PDXs compared to low-risk PDX. These findings validate the importance of incorporating PDXs for preclinical testing of oncolytic viral therapeutics and showcase a novel technique, 3D bioprinting, to test therapies in PDXs. Collectively, our data indicate that oHSVs effectively target high-risk neuroblastoma, and support the advancement of this therapy to the clinical setting.

Eliciting an immune-mediated antitumor response through oncolytic herpes simplex virus-based shared antigen expression in tumors resistant to viroimmunotherapy

Background

Oncolytic virotherapy (OV) is an immunotherapy that incorporates viral cancer cell lysis with engagement of the recruited immune response against cancer cells. Pediatric solid tumors are challenging targets because they contain both an inert immune environment and a quiet antigenic landscape, making them more resistant to conventional OV approaches. Further complicating this, herpes simplex virus suppresses host gene expression during virotherapy infection.

Methods

We therefore developed a multimodal oncolytic herpes simplex virus (oHSV) that expresses ephrin A2 (EphA2), a shared tumor-associated antigen (TAA) expressed by many tumors to improve immune-mediated antitumor activity. We verified the virus genotypically and phenotypically and then tested it in an oHSV-resistant orthotopic model (including immunophenotypic analysis), in flank and in T cell-deficient mouse models. We then assessed the antigen-expressing virus in an unrelated peripheral tumor model that also expresses the shared tumor antigen and evaluated functional T-cell response from the treated mice.

Results

Virus-based EphA2 expression induces a robust acquired antitumor immune responses in both an oHSV-resistant murine brain and peripheral tumor model. Our new multimodal oncolytic virus (1) improves survival in viroimmunotherapy resistant tumors, (2) alters both the infiltrating and peripheral T-cell populations capable of suppressing tumor growth on rechallenge, and (3) produces EphA2-specific CD8 effector-like populations.

Conclusions

Our results suggest that this flexible viral-based platform enables immune recognition of the shared TAA and improves the immune-therapeutic response, thus making it well suited for low-mutational load tumors.

In Situ Cancer Vaccination and Immunovirotherapy Using Oncolytic HSV

Herpes simplex virus (HSV) can be genetically altered to acquire oncolytic properties so that oncolytic HSV (oHSV) preferentially replicates in and kills cancer cells, while sparing normal cells, and inducing anti-tumor immune responses. Over the last three decades, a better understanding of HSV genes and functions, and improved genetic-engineering techniques led to the development of oHSV as a novel immunovirotherapy. The concept of in situ cancer vaccination (ISCV) was first introduced when oHSV was found to induce a specific systemic anti-tumor immune response with an abscopal effect on non-injected tumors, in the process of directly killing tumor cells. Thus, the use of oHSV for tumor vaccination in situ is antigen-agnostic. The research and development of oHSVs have moved rapidly, with the field of oncolytic viruses invigorated by the FDA/EMA approval of oHSV talimogene laherparepvec in 2015 for the treatment of advanced melanoma. Immunovirotherapy can be enhanced by arming oHSV with immunomodulatory transgenes and/or using them in combination with other chemotherapeutic and immunotherapeutic agents. This review offers an overview of the development of oHSV as an agent for ISCV against solid tumors, describing the multitude of different oHSVs and their efficacy in immunocompetent mouse models and in clinical trials.

Positron emission tomography imaging with 89Zr-labeled anti-CD8 cys-diabody reveals CD8+ cell infiltration during oncolytic virus therapy in a glioma murine model

Determination of treatment response to immunotherapy in glioblastoma multiforme (GBM) is a process which can take months. Detection of CD8+ T cell recruitment to the tumor with a noninvasive imaging modality such as positron emission tomography (PET) may allow for tumor characterization and early evaluation of therapeutic response to immunotherapy. In this study, we utilized 89Zr-labeled anti-CD8 cys-diabody-PET to provide proof-of-concept to detect CD8+ T cell immune response to oncolytic herpes simplex virus (oHSV) M002 immunotherapy in a syngeneic GBM model. Immunocompetent mice (n = 16) were implanted intracranially with GSC005 GBM tumors, and treated with intratumoral injection of oHSV M002 or saline control. An additional non-tumor bearing cohort (n = 4) receiving oHSV M002 treatment was also evaluated. Mice were injected with 89Zr-labeled anti-CD8 cys-diabody seven days post oHSV administration and imaged with a preclinical PET scanner. Standardized uptake value (SUV) was quantified. Ex vivo tissue analyses included autoradiography and immunohistochemistry. PET imaging showed significantly higher SUV in tumors which had been treated with M002 compared to those without M002 treatment (p = 0.0207) and the non-tumor bearing M002 treated group (p = 0.0021). Accumulation in target areas, especially the spleen, was significantly reduced by blocking with the non-labeled diabody (p < 0.001). Radioactive probe accumulation in brains was consistent with CD8+ cell trafficking patterns after oHSV treatment. This PET imaging strategy could aid in distinguishing responders from non-responders during immunotherapy of GBM.

The Current State of Oncolytic Herpes Simplex Virus for Glioblastoma Treatment

Glioblastoma (GBM) is a lethal primary malignant brain tumor with no current effective treatments. The recent emergence of immuno-virotherapy and FDA approval of T-VEC have generated a great expectation towards oncolytic herpes simplex viruses (oHSVs) as a promising treatment option for GBM. Since the generation and testing of the first genetically engineered oHSV in glioma in the early 1990s, oHSV-based therapies have shown a long way of great progress in terms of anti-GBM efficacy and safety, both preclinically and clinically. Here, we revisit the literature to understand the recent advancement of oHSV in the treatment of GBM. In addition, we discuss current obstacles to oHSV-based therapies and possible strategies to overcome these pitfalls.

The Association of Human Herpesviruses with Malignant Brain Tumor Pathology and Therapy: Two Sides of a Coin

The role of certain viruses in malignant brain tumor development remains controversial. Experimental data demonstrate that human herpesviruses (HHVs), particularly cytomegalovirus (CMV), Epstein–Barr virus (EBV) and human herpes virus 6 (HHV-6), are implicated in brain tumor pathology, although their direct role has not yet been proven. CMV is present in most gliomas and medulloblastomas and is known to facilitate oncomodulation and/or immunomodulation, thus promoting cancer cell proliferation, invasion, apoptosis, angiogenesis, and immunosuppression. EBV and HHV-6 have also been detected in brain tumors and high-grade gliomas, showing high rates of expression and an inflammatory potential. On the other hand, due to the neurotropic nature of HHVs, novel studies have highlighted the engagement of such viruses in the development of new immunotherapeutic approaches in the context of oncolytic viral treatment and vaccine-based strategies against brain tumors. This review provides a comprehensive evaluation of recent scientific data concerning the emerging dual role of HHVs in malignant brain pathology, either as potential causative agents or as immunotherapeutic tools in the fight against these devastating diseases.

Clinically Explored Virus-Based Therapies for the Treatment of Recurrent High-Grade Glioma in Adults

As new treatment modalities are being explored in neuro-oncology, viruses are emerging as a promising class of therapeutics. Virotherapy consists of the introduction of either wild-type or engineered viruses to the site of disease, where they exert an antitumor effect. These viruses can either be non-lytic, in which case they are used to deliver gene therapy, or lytic, which induces tumor cell lysis and subsequent host immunologic response. Replication-competent viruses can then go on to further infect and lyse neighboring glioma cells. This treatment paradigm is being explored extensively in both preclinical and clinical studies for a variety of indications. Virus-based therapies are advantageous due to the natural susceptibility of glioma cells to viral infection, which improves therapeutic selectivity. Furthermore, lytic viruses expose glioma antigens to the host immune system and subsequently stimulate an immune response that specifically targets tumor cells. This review surveys the current landscape of oncolytic virotherapy clinical trials in high-grade glioma, summarizes preclinical experiences, identifies challenges associated with this modality across multiple trials, and highlights the potential to integrate this therapeutic strategy into promising combinatory approaches.

"Non-Essential" Proteins of HSV-1 with Essential Roles In Vivo: A Comprehensive Review

Viruses encode for structural proteins that participate in virion formation and include capsid and envelope proteins. In addition, viruses encode for an array of non-structural accessory proteins important for replication, spread, and immune evasion in the host and are often linked to virus pathogenesis. Most virus accessory proteins are non-essential for growth in cell culture because of the simplicity of the infection barriers or because they have roles only during a state of the infection that does not exist in cell cultures (i.e., tissue-specific functions), or finally because host factors in cell culture can complement their absence. For these reasons, the study of most nonessential viral factors is more complex and requires development of suitable cell culture systems and in vivo models. Approximately half of the proteins encoded by the herpes simplex virus 1 (HSV-1) genome have been classified as non-essential. These proteins have essential roles in vivo in counteracting antiviral responses, facilitating the spread of the virus from the sites of initial infection to the peripheral nervous system, where it establishes lifelong reservoirs, virus pathogenesis, and other regulatory roles during infection. Understanding the functions of the non-essential proteins of herpesviruses is important to understand mechanisms of viral pathogenesis but also to harness properties of these viruses for therapeutic purposes. Here, we have provided a comprehensive summary of the functions of HSV-1 non-essential proteins.

Oncolytic Virotherapy in Glioma Tumors

Glioma tumors are one of the most devastating cancer types. Glioblastoma is the most advanced stage with the worst prognosis. Current therapies are still unable to provide an effective cure. Recent advances in oncolytic immunotherapy have generated great expectations in the cancer therapy field. The use of oncolytic viruses (OVs) in cancer treatment is one such immune-related therapeutic alternative. OVs have a double oncolytic action by both directly destroying the cancer cells and stimulating a tumor specific immune response to return the ability of tumors to escape the control of the immune system. OVs are one promising alternative to conventional therapies in glioma tumor treatment. Several clinical trials have proven the feasibility of using some viruses to specifically infect tumors, eluding undesired toxic effects in the patient. Here, we revisited the literature to describe the main OVs proposed up to the present moment as therapeutic alternatives in order to destroy glioma cells in vitro and trigger tumor destruction in vivo. Oncolytic viruses were divided with respect to the genome in DNA and RNA viruses. Here, we highlight the results obtained in various clinical trials, which are exploring the use of these agents as an alternative where other approaches provide limited hope.

Tumor Control by Cytomegalovirus: A Door Open for Oncolytic Virotherapy?

Belonging to the herpesviridae family, human cytomegalovirus (HCMV) is a well-known ubiquitous pathogen that establishes a lifelong infection in humans. Recently, a beneficial tumor-cytoreductive role of CMV infection has been defined in human and animal models. Described as a potential anti-tumoral activity, HCMV modulates the tumor microenvironment mainly by inducing cell death through apoptosis and prompting a robust stimulatory effect on the immune cells infiltrating the tumor tissue. However, major current limitations embrace transient protective effect and a viral dissemination potential in immunosuppressed hosts. The latter could be counteracted through direct viral intratumoral delivery, use of non-human strains, or even defective CMV vectors to ascertain transformed cells-selective tropism. This potential oncolytic activity could be complemented by tackling further platforms, namely combination with immune checkpoint inhibitors or epigenetic therapy, as well as the use of second-generation chimeric oncovirus, for instance HCMV/HSV-1 oncolytic virus. Overall, preliminary data support the use of CMV in viral oncolytic therapy as a viable option, establishing thus a potential new modality, where further assessment through extensive basic research armed by molecular biotechnology is compulsory.

STING Restricts oHSV Replication and Spread in Resistant MPNSTs but Is Dispensable for Basal IFN-Stimulated Gene Upregulation

Malignant peripheral nerve sheath tumors (MPNSTs) are an aggressive soft-tissue sarcoma amenable only to surgical resection. Oncolytic herpes simplex viruses (oHSVs) are a promising experimental therapy. We previously showed that basal interferon (IFN) and nuclear factor κB (NFκB) signaling upregulate IFN-stimulated gene (ISG) expression and restrict efficient viral infection and cell-to-cell spread in ∼50% of tested MPNSTs. Stimulator of Interferon Genes (STING) integrates DNA sensor activity and mediates downstream IFN signaling in infected cells. We sought to identify STING’s role in oHSV resistance and contribution to basal ISG upregulation in MPNSTs. We show that the level of STING activity in human MPNST cell lines is predictive of oHSV sensitivity and that resistant cell lines have intact mechanisms for detection of cytosolic double-stranded DNA (dsDNA). Furthermore, we show that STING downregulation renders MPNSTs more permissive to oHSV infection and cell-to-cell spread. While next-generation viruses can exploit this loss of STING activity, first-generation viruses remain restricted. Finally, STING is not integral to the previously-observed basal ISG upregulation, indicating that other pathways contribute to basal IFN signaling in resistant MPNSTs. These data broaden our understanding of the intrinsic pathways in MPNSTs and their role in oHSV resistance and offer potential targets to potentiate oncolytic virus activity.

Immunotherapeutic Challenges for Pediatric Cancers

Solid tumors contain a mixture of malignant cells and non-malignant infiltrating cells that often create a chronic inflammatory and immunosuppressive microenvironment that restricts immunotherapeutic approaches. Although childhood and adult cancers share some similarities related to microenvironmental changes, pediatric cancers are unique, and adult cancer practices may not be wholly applicable to our pediatric patients. This review highlights the differences in tumorigenesis, viral infection, and immunologic response between children and adults that need to be considered when trying to apply experiences from experimental therapies in adult cancer patients to pediatric cancers.

Recent advances in oncolytic virus-based cancer therapy

Administration of oncolytic viruses (OVs) is an emerging anticancer strategy that exploits the lytic nature of viral replication to enhance the killing of malignant cells. OVs can be used as tools to directly induce cancer cell death and to trigger local and/or systemic immune responses to metastatic cancer in vivo. The effectiveness of OV therapy was initially highlighted by the clinical use of the genetically modified herpes virus, talimogene laherparepvec, for melanoma therapy. A number of OVs are now being evaluated as potential treatments for cancer in clinical trials. In spite of being engineered to specifically target tumor cells, the safety and off-target effects of OV therapy are a concern. The potential safety concerns of OVs are highlighted by current clinical trial criteria, which exclude individuals harbouring other viral infections and people who are immunocompromised. Despite the potential for adverse effects, clinical trials to date revealed relatively minimal adverse immune-related effects, such as fever. With advances in our understanding of virus replication cycles, several novel OVs have emerged. Reverse genetic systems have facilitated the insertion of anticancer genes into a range of OVs to further enhance their tumor-killing capacity. In this review, we highlight the recent advances in OV therapy for a range of human cancers in in vitro and in in vivo animal studies. We further discuss the future of OVs as a therapeutic strategy for a range of life-threatening cancers.

IL-6 and IL-8 secreted by tumour cells impair the function of NK cells via the STAT3 pathway in oesophageal squamous cell carcinoma

Background

Recurrence and metastasis are the leading causes of tumour-related death in patients with oesophageal squamous cell carcinoma (ESCC). Tumour-infiltrating natural killer cells (NK cells) display powerful cytotoxicity to tumour cells and play a pivotal role in tumour therapy. However, the phenotype and functional regulation of NK cells in oesophageal squamous cell carcinoma (ESCC) remains largely unknown.

Methods

Single cell suspensions from blood and tissue samples were isolated by physical dissociation and filtering through a 70 μm cell strainer. Flow cytometry was applied to profile the activity and function of NK cells, and an antibody chip experiment was used to identify and quantitate cytokine levels. We studied IL-6 and IL-8 function in primary oesophageal squamous carcinoma and NK cell co-cultures in vitro and by a xenograft tumour model in vivo. Western blotting was used to quantitate STAT3 (signal transducer and activator of transcription 3) and p-STAT3 levels. Finally, we performed an IHC array to analyse IL-6/IL-8 (interleukin 6/interleukin 8) expression in 103 pairs of tumours and matched adjacent tissues of patients with ESCC to elucidate the correlation between IL-6 or IL-8 and clinical characteristics.

Results

The percentages of NK cells in both peripheral blood and tumour tissues from patients with ESCC were significantly increased in comparison with those in the controls and correlated with the clinical characteristics. Furthermore, the decrease in activating receptors and increase in inhibitory receptors on the surface of tumour-infiltrating NK cells was confirmed by flow cytometry. The level of granzyme B, the effector molecule of tumour-infiltrating NK cells, was also decreased. Mechanistically, primary ESCC cells activated the STAT3 signalling pathway on NK cells through IL-6 and IL-8 secretion, leading to the downregulation of activating receptors (NKp30 and NKG2D) on the surface of NK cells. An ex vivo study showed that blockade of STAT3 attenuated the IL-6/IL-8-mediated impairment of NK cell function. Moreover, the expression of IL-6 or IL-8 in tumour tissues was validated by immunohistochemistry to be positively correlated with tumour progression and poor survival, respectively.

Conclusions

Tumour cell-secreted IL-6 and IL-8 impair the activity and function of NK cells via STAT3 signalling and contribute to oesophageal squamous cell carcinoma malignancy.

Electronic supplementary material

The online version of this article (10.1186/s13046-019-1310-0) contains supplementary material, which is available to authorized users.

Oncolytic herpes simplex virus immunotherapy for brain tumors: current pitfalls and emerging strategies to overcome therapeutic resistance

Malignant tumors of the central nervous system (CNS) continue to be a leading cause of cancer-related mortality in both children and adults. Traditional therapies for malignant brain tumors consist of surgical resection and adjuvant chemoradiation; such approaches are often associated with extreme morbidity. Accordingly, novel, targeted therapeutics for neoplasms of the CNS, such as immunotherapy with oncolytic engineered herpes simplex virus (HSV) therapy, are urgently warranted. Herein, we discuss treatment challenges related to HSV virotherapy delivery, entry, replication, and spread, and in so doing focus on host antiviral immune responses and the immune microenvironment. Strategies to overcome such challenges including viral re-engineering, modulation of the immunoregulatory microenvironment and combinatorial therapies with virotherapy, such as checkpoint inhibitors, radiation, and vaccination are also examined in detail.

Oncolytic herpes simplex virus therapy for malignant glioma: current approaches to successful clinical application

INTRODUCTION

With the approval of talimogene laherparepvec (T-VEC) for advanced malignant melanoma, virotherapy using oncolytic herpes simplex virus (oHSV) is now emerging as a viable therapeutic option for cancer patients, including malignant gliomas.

AREAS COVERED

This review summarizes the most recent literature to provide cutting-edge knowledge about preclinical and clinical development of oHSV therapy for malignant gliomas, presenting current approaches to overcome obstacles to successful clinical application of oHSV in neuro-oncology.

EXPERT OPINION

Current strategies to improve the efficacy of oHSV therapy include engineering new viruses, modulation of innate and adaptive immune responses, combination with other treatments, and developing new oHSV delivery. All of these could rapidly be translated into clinical investigations, following several clinical trials that are currently ongoing.

Combination Therapy Using Ruxolitinib and Oncolytic HSV Renders Resistant MPNSTs Susceptible to Virotherapy

Malignant peripheral nerve sheath tumors (MPNSTs) are aggressive soft-tissue sarcomas resistant to most cancer treatments. Surgical resection remains the primary treatment, but this is often incomplete, ultimately resulting in high mortality and morbidity rates. There has been a resurgence of interest in oncolytic virotherapy because of encouraging preclinical and clinical trial results. Oncolytic herpes simplex virus (oHSV) selectively replicates in cancer cells, lysing the cell and inducing antitumor immunity. We previously showed that basal interferon (IFN) signaling increases interferon-stimulated gene (ISG) expression, restricting viral replication in almost 50% of MPNSTs. The FDA-approved drug ruxolitinib (RUX) temporarily resets this constitutively active STAT signaling and renders the tumor cells susceptible to oHSV infection in cell culture. In the studies described here, we translated our in vitro results into a syngeneic MPNST tumor model. Consistent with our previous results, murine MPNSTs exhibit a similar IFN- and ISG-mediated oHSV-resistance mechanism, and virotherapy alone provides no antitumor benefit in vivo However, pretreatment of mice with ruxolitinib reduced ISG expression, making the tumors susceptible to oHSV infection. Ruxolitinib pretreatment improved viral replication and altered the oHSV-induced immune-mediated response. Our results showed that this combination therapy increased CD8⁺ T-cell activation in the tumor microenvironment and that this population was indispensable for the antitumor benefit that follows from the combination of RUX and oHSV. These data suggest that JAK inhibition prior to oncolytic virus treatment augments both oHSV replication and the immunotherapeutic efficacy of oncolytic herpes virotherapy.