Synergistic action of oncolytic herpes simplex virus and radiotherapy in pancreatic cancer cell lines

Advances in antitumour therapy with oncolytic herpes simplex virus combinations

Oncolytic Virus (OVs) is an emerging approach to tumour immunity that allows the use of natural or genetically modified viruses to specifically infect and lyse tumour cells without damaging normal cells. Oncolytic herpes simplex virus (oHSV) is one of the more widely researched and applied OVs in the field of oncology, which can directly kill tumour cells to promote anti-tumour immune responses. oHSV is one of the few viruses with good antiviral drugs, so oHSV is also more clinically safe. In recent years, in addition to monotherapy of oHSV in tumours, more and more studies have been devoted to exploring the anti-tumour effects of oHSV in combination with other therapeutic approaches. In this article we describe the progress of oHSV combination therapy against tumours in the nervous system, digestive system, reproductive system and other systems.

HSV: The scout and assault for digestive system tumors

More than 25% of all malignant tumors are digestive system tumors (DSTs), which mostly include esophageal cancer, gastric cancer, pancreatic cancer, liver cancer, gallbladder cancer and cholangiocarcinoma, and colorectal cancer. DSTs have emerged as one of the prominent reasons of morbidity and death in many nations and areas around the world, posing a serious threat to human life and health. General treatments such as radiotherapy, chemotherapy, and surgical resection can poorly cure the patients and have a bad prognosis. A type of immunotherapy known as oncolytic virus therapy, have recently shown extraordinary anti-tumor effectiveness. One of the viruses that has been the subject of the greatest research in this field, the herpes simplex virus (HSV), has shown excellent potential in DSTs. With a discussion of HSV-1 based on recent studies, we outline the therapeutic effects of HSV on a number of DSTs in this review. Additionally, the critical function of HSV in the detection of cancers is discussed, and some HSV future possibilities are shown.

Senecavirus A as an Oncolytic Virus: Prospects, Challenges and Development Directions

Oncolytic viruses have the capacity to selectively kill infected tumor cells and trigger protective immunity. As such, oncolytic virotherapy has become a promising immunotherapy strategy against cancer. A variety of viruses from different families have been proven to have oncolytic potential. Senecavirus A (SVA) was the first picornavirus to be tested in humans for its oncolytic potential and was shown to penetrate solid tumors through the vascular system. SVA displays several properties that make it a suitable model, such as its inability to integrate into human genome DNA and the absence of any viral-encoded oncogenes. In addition, genetic engineering of SVA based on the manipulation of infectious clones facilitates the development of recombinant viruses with improved therapeutic indexes to satisfy the criteria of safety and efficacy regulations. This review summarizes the current knowledge and strategies of genetic engineering for SVA, and addresses the current challenges and future directions of SVA as an oncolytic agent.

Oncolytic virus therapy in cancer: A current review

In view of the advancement in the understanding about the most diverse types of cancer and consequently a relentless search for a cure and increased survival rates of cancer patients, finding a therapy that is able to combat the mechanism of aggression of this disease is extremely important. Thus, oncolytic viruses (OVs) have demonstrated great benefits in the treatment of cancer because it mediates antitumor effects in several ways. Viruses can be used to infect cancer cells, especially over normal cells, to present tumor-associated antigens, to activate "danger signals" that generate a less immune-tolerant tumor microenvironment, and to serve transduction vehicles for expression of inflammatory and immunomodulatory cytokines. The success of therapies using OVs was initially demonstrated by the use of the genetically modified herpes virus, talimogene laherparepvec, for the treatment of melanoma. At this time, several OVs are being studied as a potential treatment for cancer in clinical trials. However, it is necessary to be aware of the safety and possible adverse effects of this therapy; after all, an effective treatment for cancer should promote regression, attack the tumor, and in the meantime induce minimal systemic repercussions. In this manuscript, we will present a current review of the mechanism of action of OVs, main clinical uses, updates, and future perspectives on this treatment.

Oncolytic viruses for triple negative breast cancer and beyond

Biological therapy is considered an alternative treatment capable of eliciting the same effects on tumors as surgery, radiotherapy, and chemotherapy. As a major player in biological therapy, oncolytic viruses (OVs) have attracted great attention and achieved good results. Specifically, the successful application of OVs in head and neck cancer, as well as melanoma, promoted its research in triple negative breast cancer (TNBC). TNBC is a high-risk molecular type of breast cancer, characterized by strong invasion, easy recurrence, and metastasis. Due to the absence of estrogen and progesterone receptors, as well as the absence of overexpression or gene amplification of human epidermal growth factor receptor 2 (HER2), endocrine therapy and anti HER-2 targeted therapy have proven ineffective. Although chemotherapy has shown substantial efficacy in some TNBC patients, the occurrence of drug resistance and poor prognosis have prompted the exploration of new and effective treatment methods. The emerging concept of OVs provides a new platform to treat TNBC. Indeed, several studies have confirmed the therapeutic effects of OVs in TNBC. Numerous studies have also investigated the efficacy of OVs in other malignances, including solid tumor clinical trials, thus further demonstrating the promising application of oncolytic virotherapy for TNBC. The primary focus of the current review is the examination of OV mechanisms underlying their antitumor properties, while also summarizing the ongoing progress in OV research regarding TNBC treatment, as well as the various combinatorial strategies comprising OVs and other therapies. We also briefly introduce specific relevant clinical trials and discuss some of the progress in the research of novel OVs for the treatment of other malignancies, thereby affirming the significant therapeutic potential of OVs for the treatment of TNBC, as well as other cancers.

The Oncolytic Virus in Cancer Diagnosis and Treatment

Cancer has always been an enormous threat to human health and survival. Surgery, radiotherapy, and chemotherapy could improve the survival of cancer patients, but most patients with advanced cancer usually have a poor survival or could not afford the high cost of chemotherapy. The emergence of oncolytic viruses provided a new strategy for us to alleviate or even cure malignant tumors. An oncolytic virus can be described as a genetically engineered or naturally existing virus that can selectively replicate in cancer cells and then kill them without damaging the healthy cells. There have been many kinds of oncolytic viruses, such as herpes simplex virus, adenovirus, and Coxsackievirus. Moreover, they have different clinical applications in cancer treatment. This review focused on the clinical application of oncolytic virus and predicted the prospect by analyzing the advantages and disadvantages of oncolytic virotherapy.

Oncolytic herpes simplex virus and immunotherapy

BACKGROUND

Oncolytic viruses have been proposed to be employed as a potential treatment of cancer. Well targeted, they will serve the purpose of cracking tumor cells without causing damage to normal cells. In this category of oncolytic viral drugs human pathogens herpes simplex virus (HSV) is especially suitable for the cause. Although most viral infection causes antiviral reaction in the host, HSV has multiple mechanisms to evade those responses. Powerful anti-tumor effect can thus be achieved via genetic manipulation of the HSV genes involved in this evading mechanism, namely deletions or mutations that adapt its function towards a tumor microenvironment. Currently, oncolytic HSV (oHSV) is widely use in clinical; moreover, there's hope that its curative effect will be further enhanced through the combination of oHSV with both traditional and emerging therapeutics.

RESULTS

In this review, we provide a summary of the HSV host antiviral response evasion mechanism, HSV expresses immune evasion genes such as ICP34.5, ICP0, Us3, which are involved in inducing and activating host responses, so that the virus can evade the immune system and establish effective long-term latent infection; we outlined details of the oHSV strains generated by removing genes critical to viral replication such as ICP34.5, ICP0, and inserting therapeutic genes such as LacZ, granulocyte macrophage colony-stimulating factor (GM-CSF); security and limitation of some oHSV such G207, 1716, OncoVEX, NV1020, HF10, G47 in clinical application; and the achievements of oHSV combined with immunotherapy and chemotherapy.

CONCLUSION

We reviewed the immunotherapy mechanism of the oHSV and provided a series of cases. We also pointed out that an in-depth study of the application of oHSV in cancer treatment will potentially benefits cancer patients more.

Oncolytic Virotherapy versus Cancer Stem Cells: A Review of Approaches and Mechanisms

A growing body of evidence suggests that a subset of cells within tumors are resistant to conventional treatment modalities and may be responsible for disease recurrence. These cells are called cancer stem cells (CSC), which share properties with normal stem cells including self-renewal, pluripotency, drug resistance, and the ability to maintain quiescence. While most conventional therapies can efficiently destroy rapidly dividing cancer cells comprising the bulk of a tumor, they often fail to kill the less abundant and quiescent CSCs. Furthermore, killing of only differentiated cells in the tumor may actually allow for enrichment of CSCs and thereby portend a bad prognosis. Therefore, targeting of CSCs is important to achieve long-term success in cancer therapy. Oncolytic viruses represent a completely different class of therapeutics that can kill cancer cells in a variety of ways, which differ from those of conventional therapies. Hence, CSCs that are inherently resistant to conventional therapies may be susceptible to oncolytic virus-mediated killing. Recent studies have shown that oncolytic viruses can efficiently kill CSCs in many types of cancer. Here, we discuss the mechanism through which CSCs can escape conventional therapies and how they may still be susceptible to different classes of oncolytic viruses. Furthermore, we provide a summary of recent studies that have tested oncolytic viruses on CSCs of different origins and discuss possible future directions for this fascinating subset of oncolytic virus research.

Effect of Repeat Dosing of Engineered Oncolytic Herpes Simplex Virus on Preclinical Models of Rhabdomyosarcoma

Rhabdomyosarcoma (RMS), a tumor of skeletal muscle origin, is the most common sarcoma of childhood. Despite multidrug chemotherapy regimens, surgical intervention, and radiation treatment, outcomes remain poor, especially in advanced disease, and novel therapies are needed for the treatment of these aggressive malignancies. Genetically engineered oncolytic viruses, such as herpes simplex virus-1 (HSV), are currently being explored as treatments for pediatric tumors. M002, an oncolytic HSV, has both copies of the γ₁34.5 gene deleted, enabling replication in tumor cells but thwarting infection of normal, postmitotic cells. We hypothesized that M002 would infect human RMS tumor cells and lead to decreased tumor cell survival in vitro and impede tumor growth in vivo. In the current study, we demonstrated that M002 could infect, replicate in, and decrease cell survival in both embryonal (ERMS) and alveolar rhabdomyosarcoma (ARMS) cells. Additionally, M002 reduced xenograft tumor growth and increased animal survival in both ARMS and ERMS. Most importantly, we showed for the first time that repeated dosing of oncolytic virus coupled with low-dose radiation provided improved tumor response in RMS. These findings provide support for the clinical investigation of oncolytic HSV in pediatric RMS.

Pancreatic cancer from bench to bedside: molecular pathways and treatment options

In the last forty years the pancreatic cancer treatment has made advances, however; still novel drugs are needed. It is known that the five year survival rate remains around 5%. The best treatment option still remains surgery, if patients are diagnosed early. In the last decade the biology of pancreatic cancer has been vastly explored and novel agents such as; tyrosine kinase agents, or vaccines have been added as a treatment perspective. The big challenge is now to translate this knowledge in better outcomes for patients. In this current review we will present information from pancreatic cancer diagnosis to molecular pathways and treatment options; current and future.

Viro-immune therapy: A new strategy for treatment of pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is an almost uniformly lethal disease with less than 5% survival at five years. This is largely due to metastatic disease, which is already present in the majority of patients when diagnosed. Even when the primary cancer can be removed by radical surgery, local recurrence occurs within one year in 50%-80% of cases. Therefore, it is imperative to develop new approaches for the treatment of advanced cancer and the prevention of recurrence after surgery. Tumour-targeted oncolytic viruses (TOVs) have become an attractive therapeutic agent as TOVs can kill cancer cells through multiple mechanisms of action, especially via virus-induced engagement of the immune response specifically against tumour cells. To attack tumour cells effectively, tumour-specific T cells need to overcome negative regulatory signals that suppress their activation or that induce tolerance programmes such as anergy or exhaustion in the tumour microenvironment. In this regard, the recent breakthrough in immunotherapy achieved with immune checkpoint blockade agents, such as anti-cytotoxic T-lymphocyte-associate protein 4, programmed death 1 (PD-1) or PD-L1 antibodies, has demonstrated the possibility of relieving immune suppression in PDAC. Therefore, the combination of oncolytic virotherapy and immune checkpoint blockade agents may synergistically function to enhance the antitumour response, lending the opportunity to be the future for treatment of pancreatic cancer.

Oncolytic virotherapy using herpes simplex virus: how far have we come?

Oncolytic virotherapy exploits the properties of human viruses to naturally cytolysis of cancer cells. The human pathogen herpes simplex virus (HSV) has proven particularly amenable for use in oncolytic virotherapy. The relative safety of HSV coupled with extensive knowledge on how HSV interacts with the host has provided a platform for manipulating HSV to enhance the targeting and killing of human cancer cells. This has culminated in the approval of talimogene laherparepvec for the treatment of melanoma. This review focuses on the development of HSV as an oncolytic virus and where the field is likely to head in the future.

Vaccinia virus, a promising new therapeutic agent for pancreatic cancer

The poor prognosis of pancreatic cancer patients signifies a need for radically new therapeutic strategies. Tumor-targeted oncolytic viruses have emerged as attractive therapeutic candidates for cancer treatment due to their inherent ability to specifically target and lyse tumor cells as well as induce antitumor effects by multiple action mechanisms. Vaccinia virus has several inherent features that make it particularly suitable for use as an oncolytic agent. In this review, we will discuss the potential of vaccinia virus in the management of pancreatic cancer in light of our increased understanding of cellular and immunological mechanisms involved in the disease process as well as our extending knowledge in the biology of vaccinia virus.

Oncolytic viral therapy for pancreatic cancer: current research and future directions

The development of targeted agents and chemotherapies for pancreatic cancer has only modestly affected clinical outcome and not changed 5-year survival. Fortunately the genetic and molecular mechanisms underlying pancreatic cancer are being rapidly uncovered and are providing opportunities for novel targeted therapies. Oncolytic viral therapy is one of the most promising targeted agents for pancreatic cancer. This review will look at the current state of the development of these self-replicating nanoparticles in the treatment of pancreatic cancer.

Oncolytic vaccinia virus in combination with radiation shows synergistic antitumor efficacy in pancreatic cancer

Combining oncolytic viruses with conventional therapy such as radiation is an innovative option for pancreatic cancer. We demonstrated that combination of GLV-1h151 and radiation yielded a synergistic cytotoxic effect, with the greatest effect achieved in the AsPC-1cell line. Combination treatment significantly increased apoptosis compared with either single treatment or the control group. In mice bearing human pancreatic tumor xenografts, combination treatment resulted in significantly enhanced inhibition of tumor growth. No evidence of toxicity was observed in mice. These results indicate that the combination of GLV-1h151 and radiation has great potential for translation into clinic practice.

Preclinical evaluation of engineered oncolytic herpes simplex virus for the treatment of neuroblastoma

Despite intensive research efforts and therapeutic advances over the last few decades, the pediatric neural crest tumor, neuroblastoma, continues to be responsible for over 15% of pediatric cancer deaths. Novel therapeutic options are needed for this tumor. Recently, investigators have shown that mice with syngeneic murine gliomas treated with an engineered, neuroattenuated oncolytic herpes simplex virus-1 (oHSV), M002, had a significant increase in survival. M002 has deletions in both copies of the γ₁34.5 gene, enabling replication in tumor cells but precluding infection of normal neural cells. We hypothesized that M002 would also be effective in the neural crest tumor, neuroblastoma. We showed that M002 infected, replicated, and decreased survival in neuroblastoma cell lines. In addition, we showed that in murine xenografts, treatment with M002 significantly decreased tumor growth, and that this effect was augmented with the addition of ionizing radiation. Importantly, survival could be increased by subsequent doses of radiation without re-dosing of the virus. Finally, these studies showed that the primary entry protein for oHSV, CD111 was expressed by numerous neuroblastoma cell lines and was also present in human neuroblastoma specimens. We concluded that M002 effectively targeted neuroblastoma and that this oHSV may have potential for use in children with unresponsive or relapsed neuroblastoma.

The diversity between pancreatic head and body/tail cancers: clinical parameters and in vitro models

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) can be divided into head, body and tail cancers according to the anatomy. Distinctions in tissue composition, vascularization and innervations have been clearly identified between the head and body/tail of the pancreas both in embryological development and in histopathology. To understand the postulated genotype difference, we present comprehensive information on two PDAC cell lines as typical representatives originating from pancreatic head and body/tail cancers, respectively.

DATA SOURCE

In the present review, we compare the difference between pancreatic head and body/tail cancers regarding clinical parameters and introducing an in vitro model.

RESULTS

Increasing evidence has shown that tumors at different locations (head vs body/tail) display different clinical presentation (e.g. incidence, symptom), treatment efficiency (e.g. surgery, chemotherapy) and thus patient prognosis. However, the genetic or molecular diversity (e.g. mutations, microRNA) between the two subtypes of PDAC has not been elucidated so far. They present different chemo- and/or radio-resistance, extracellular matrix adhesion and invasiveness, as well as genetic profiles.

CONCLUSION

Genetic and tumor biological diversity exists in PDAC according to the tumor localization.

The effects of radiation on antitumor efficacy of an oncolytic adenovirus vector in the Syrian hamster model

We report that radiation enhances the antitumor efficacy of the oncolytic adenovirus vector VRX-007 in Syrian hamster tumors. We used tumor-specific irradiation of subcutaneous tumors and compared treatment options of radiation alone or combined with VRX-007 and cyclophosphamide (CP). Radiation therapy further augmented the VRX-007-mediated inhibition of tumor growth, in both CP-treated and non-CP-treated hamsters, even though radiation did not lead to increased viral replication in tumors when compared to those treated with VRX-007 alone. Moreover, tumor growth inhibition was similar in tumors irradiated either one week before or after injection with VRX-007, which suggests that radiation exerts its antitumor effect independently from vector therapy. Thus, our results demonstrate that these two therapies do not have to be provided simultaneously to enhance their combined effectiveness against subcutaneous hamster tumors.

Advance in herpes simplex viruses for cancer therapy

Oncolytic virotherapy is an attractive approach that uses live viruses to selectively kill cancer cells. Oncolytic viruses can be genetically engineered to induce cell lyses through virus replication and cytotoxic protein expression. Herpes simplex virus (HSV) has become one of the most widely clinically used oncolytic agent. Various types of HSV have been studied in basic or clinical research. Combining oncolytic virotherapy with chemotherapy or radiotherapy generally produces synergic action with unclear molecular mechanisms. Arming HSV with therapeutic transgenes is a promising strategy and can be used to complement conventional therapies. As an efficient gene delivery system, HSV has been successfully used to deliver various immunomodulatory molecules. Arming HSV with therapeutic genes merits further investigation for potential clinical application.

Natural oncolytic activity of live-attenuated measles virus against human lung and colorectal adenocarcinomas

Lung and colorectal cancers are responsible for approximately 2 million deaths each year worldwide. Despite continual improvements, clinical management of these diseases remains challenging and development of novel therapies with increased efficacy is critical to address these major public health issues. Oncolytic viruses have shown promising results against cancers that are resistant to conventional anticancer therapies. Vaccine strains of measles virus (MV) exhibit such natural antitumor properties by preferentially targeting cancer cells. We tested the ability of live-attenuated Schwarz strain of MV to specifically infect tumor cells derived from human lung and colorectal adenocarcinomas and demonstrated that live-attenuated MV exhibits oncolytic properties against these two aggressive neoplasms. We also showed that Schwarz MV was able to prevent uncontrollable growth of large, established lung and colorectal adenocarcinoma xenografts in nude mice. Moreover, MV oncolysis is associated with in vivo activation of caspase-3 in colorectal cancer model, as shown by immunohistochemical staining. Our results provide new arguments for the use of MV as an antitumor therapy against aggressive human malignancies.

Viral therapy for pancreatic cancer: tackle the bad guys with poison

Pancreatic cancer is one of the most devastating diseases with very poor prognosis. Only a small proportion is curable by surgical resection, whilst standard chemotherapy for patients with advanced disease has only modest effect with substantial toxicity. Therefore, there is an urgent need for the development of novel therapeutic approaches to improve the patient outcome. Recently the viral therapy is emerging as a novel effective therapeutic approach for cancer with the potential to selectively treat both primary tumor and metastatic lesions. This review provides an overview of the current status of viral treatment for pancreatic cancer, both in the laboratories and in clinical settings.

In vivo evaluation of a cancer therapy strategy combining HSV1716-mediated oncolysis with gene transfer and targeted radiotherapy

Oncolytic herpes viruses show promise for cancer treatment. However, it is unlikely that they will fulfill their therapeutic potential when used as monotherapies. An alternative strategy is to use these viruses not only as oncolytic agents but also as a delivery mechanism of therapeutic transgenes to enhance tumor cell killing. The herpes simplex virus 1 deletion mutant HSV1716 is a conditionally replicating oncolytic virus that selectively replicates in and lyses dividing tumor cells. It has a proven safety profile in clinical trials and has demonstrated efficacy as a gene-delivery vehicle. To enhance its therapeutic potential, we have engineered HSV1716 to convey the noradrenaline transporter (NAT) gene (HSV1716/NAT), whose expression endows infected cells with the capacity to accumulate the noradrenaline analog metaiodobenzylguanidine (MIBG). Thus, the NAT gene-infected cells are susceptible to targeted radiotherapy using radiolabeled (131)I-MIBG, a strategy that has already shown promise for combined targeted radiotherapy-gene therapy in cancer cells after plasmid-mediated transfection.

METHODS

We used HSV1716/NAT as a dual cell lysis-gene delivery vehicle for targeting the NAT transgene to human tumor xenografts in vivo.

RESULTS

In tumor xenografts that did not express NAT, intratumoral or intravenous injection of HSV1716/NAT induced the capacity for active uptake of (131)I-MIBG. Administration of HSV1716/NAT and (131)I-MIBG resulted in decreased tumor growth and enhanced survival relative to injection of either agent alone. Efficacy was dependent on the scheduling of delivery of the 2 agents.

CONCLUSION

These findings support a role for combination radiotherapy-gene therapy for cancer using HSV1716 expressing the NAT transgene and targeted radionuclide therapy.

Impact of novel oncolytic virus HF10 on cellular components of the tumor microenviroment in patients with recurrent breast cancer

Oncolytic viruses are a promising method of cancer therapy, even for advanced malignancies. HF10, a spontaneously mutated herpes simplex type 1, is a potent oncolytic agent. The interaction of oncolytic herpes viruses with the tumor microenvironment has not been well characterized. We injected HF10 into tumors of patients with recurrent breast carcinoma, and sought to determine its effects on the tumor microenvironment. Six patients with recurrent breast cancer were recruited to the study. Tumors were divided into two groups: saline-injected (control) and HF10-injected (treatment). We investigated several parameters including neovascularization (CD31) and tumor lymphocyte infiltration (CD8, CD4), determined by immunohistochemistry, and apoptosis, determined by terminal deoxynucleotidyl transferase dUTP nick end labeling assay. Median apoptotic cell count was lower in the treatment group (P=0.016). Angiogenesis was significantly higher in treatment group (P=0.032). Count of CD8-positive lymphocytes infiltrating the tumors was higher in the treatment group (P=0.008). We were unable to determine CD4-positive lymphocyte infiltration. An effective oncolytic viral agent must replicate efficiently in tumor cells, leading to higher viral counts, in order to aid viral penetration. HF10 seems to meet this criterion; furthermore, it induces potent antitumor immunity. The increase in angiogenesis may be due to either viral replication or the inflammatory response.

Thunder and lightning: immunotherapy and oncolytic viruses collide

For the last several decades, the development of antitumor immune-based strategies and the engineering and testing of oncolytic viruses (OVs) has occurred largely in parallel tracks. Indeed, the immune system is often thought of as an impediment to successful oncolytic virus delivery and efficacy. More recently, however, both preclinical and clinical results have revealed potential synergy between these two promising therapeutic strategies. Here, we summarize some of the evidence that supports combining OVs with immuno-therapeutics and suggest new ways to mount a multipronged biological attack against cancers.

Engineered herpes simplex virus vectors for antitumor therapy and vaccine delivery

Genetically modified herpes simplex viruses (HSVs) have been exploited for both antitumor therapy and vaccine delivery. These mutant viruses retain their ability to replicate and lyse permissive cells, including many tumor types, and are referred to as oncolytic HSVs. In addition, deletion of nonessential genes permits the introduction of foreign genes to augment the antitumor effect by either immune stimulation, targeting for select tumors, or expression of tumor or vaccine antigens. This article reviews the development of oncolytic HSVs as an anticancer therapy, as well as the application of HSV-1 vectors for delivery of targeted antigens or as vaccine adjuvants. The impact of these novel vectors with respect to enhanced antitumor activity and development of antitumor vaccination strategies is discussed.