Comparison of safety, delivery, and efficacy of two oncolytic herpes viruses (G207 and NV1020) for peritoneal cancer

Chimeric Antigen Receptor-T Cell and Oncolytic Viral Therapies for Gastric Cancer and Peritoneal Carcinomatosis of Gastric Origin: Path to Improving Combination Strategies

Precision immune oncology capitalizes on identifying and targeting tumor-specific antigens to enhance anti-tumor immunity and improve the treatment outcomes of solid tumors. Gastric cancer (GC) is a molecularly heterogeneous disease where monoclonal antibodies against human epidermal growth factor receptor 2 (HER2), vascular endothelial growth factor (VEGF), and programmed cell death 1 (PD-1) combined with systemic chemotherapy have improved survival in patients with unresectable or metastatic GC. However, intratumoral molecular heterogeneity, variable molecular target expression, and loss of target expression have limited antibody use and the durability of response. Often immunogenically "cold" and diffusely spread throughout the peritoneum, GC peritoneal carcinomatosis (PC) is a particularly challenging, treatment-refractory entity for current systemic strategies. More adaptable immunotherapeutic approaches, such as oncolytic viruses (OVs) and chimeric antigen receptor (CAR) T cells, have emerged as promising GC and GCPC treatments that circumvent these challenges. In this study, we provide an up-to-date review of the pre-clinical and clinical efficacy of CAR T cell therapy for key primary antigen targets and provide a translational overview of the types, modifications, and mechanisms for OVs used against GC and GCPC. Finally, we present a novel, summary-based discussion on the potential synergistic interplay between OVs and CAR T cells to treat GCPC.

Regional Immunotherapy for Peritoneal Carcinomatosis in Gastroesophageal Cancer: Emerging Strategies to Re-Condition a Maladaptive Tumor Environment

Peritoneal carcinomatosis originating from gastric/gastroesophageal junction cancer (GC-PC) occurs in a defined subset of gastric cancer patients with unique clinical, pathologic, molecular and immunologic characteristics that create significant obstacles to effective treatment with modern therapy. Although systemic chemo- and immuno- therapy have yielded disappointing results in GC-PC, recent advances in the characterization of GC-PC and peritoneal immune biology present new opportunities for targeted therapeutics. In this review article, we discuss the distinct properties of GC-PC and the peritoneal immune environment as they pertain to current and investigative treatment strategies. We discuss pre-clinical studies and clinical trials relevant to the modulation of the peritoneal environment as a therapeutic intervention in GC-PC. Finally, we present a road map for future combinatorial strategies based on the conception of the peritoneal cavity as a bioreactor. Within this isolated compartment, prevailing immunosuppressive conditions can be altered through regional interventions toward an adaptive phenotype that would support the effectiveness of regionally delivered cellular therapy products. It is hoped that novel combination strategies would promote efficacy not only in the sequestered peritoneal environment, but also via migration into the circulation of tumor-reactive lymphocytes to produce durable systemic disease control, thereby improving oncologic outcome and quality of life in patients with GC-PC.

The Dilemma of HSV-1 Oncolytic Virus Delivery: The Method Choice and Hurdles

Oncolytic viruses (OVs) have emerged as effective gene therapy and immunotherapy drugs. As an important gene delivery platform, the integration of exogenous genes into OVs has become a novel path for the advancement of OV therapy, while the herpes simplex virus type 1 (HSV-1) is the most commonly used. However, the current mode of administration of HSV-1 oncolytic virus is mainly based on the tumor in situ injection, which limits the application of such OV drugs to a certain extent. Intravenous administration offers a solution to the systemic distribution of OV drugs but is ambiguous in terms of efficacy and safety. The main reason is the synergistic role of innate and adaptive immunity of the immune system in the response against the HSV-1 oncolytic virus, which is rapidly cleared by the body's immune system before it reaches the tumor, a process that is accompanied by side effects. This article reviews different administration methods of HSV-1 oncolytic virus in the process of tumor treatment, especially the research progress in intravenous administration. It also discusses immune constraints and solutions of intravenous administration with the intent to provide new insights into HSV-1 delivery for OV therapy.

Establishing a New Platform to Investigate the Efficacy of Oncolytic Virotherapy in a Human Ex Vivo Peritoneal Carcinomatosis Model

Oncolytic virotherapy constitutes a promising treatment option for many solid cancers, including peritoneal carcinomatosis (PC), which still represents a terminal stage of many types of tumors. To date, the in vitro efficacy of oncolytic viruses is mostly tested in 2D-cultured tumor cell lines due to the lack of realistic 3D in vitro tumor models. We have investigated the feasibility of virotherapy as a treatment option for PC in a human ex vivo peritoneum co-culture model. Human HT-29 cancer cells stably expressing marker genes GFP and firefly luciferase (GFP/luc) were cultured on human peritoneum and infected with two prototypic oncolytic viruses (GLV-0b347 and MeV-DsRed). Both viral constructs were able to infect HT-29 cells in patient-derived peritoneum with high tumor specificity. Over time, both GFP signal and luciferase activity decreased substantially, thereby indicating successful virus-induced oncolysis. Furthermore, immunohistochemistry stainings showed specific virotherapeutic infections of HT-29 cells and effective tumor cell lysis in infected co-cultures. Thus, the PC model established here provides a clinically relevant screening platform to evaluate the therapeutic efficacy of virotherapeutic compounds and also to investigate, in an autologous setting, the immunostimulatory potential of oncolytic viruses for PC in a unique human model system superior to standard 2D in vitro models.

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.

Herpes simplex virus 1 as an oncolytic viral therapy for refractory cancers

The need for efficacious and non-toxic cancer therapies is paramount. Oncolytic viruses (OVs) are showing great promise and are introducing new possibilities in cancer treatment with their ability to selectively infect tumor cells and trigger antitumor immune responses. Herpes Simplex Virus 1 (HSV-1) is a commonly selected OV candidate due to its large genome, relative safety profile, and ability to infect a variety of cell types. Talimogene laherparevec (T-VEC) is an HSV-1-derived OV variant and the first and only OV therapy currently approved for clinical use by the United States Food and Drug Administration (FDA). This review provides a concise description of HSV-1 as an OV candidate and the genomic organization of T-VEC. Furthermore, this review focuses on the advantages and limitations in the use of T-VEC compared to other HSV-1 OV variants currently in clinical trials. In addition, approaches for future directions of HSV-1 OVs as cancer therapy is discussed.

Oncolytic HSV: Underpinnings of Tumor Susceptibility

Oncolytic herpes simplex virus (oHSV) is a therapeutic modality that has seen substantial success for the treatment of cancer, though much remains to be improved. Commonly attenuated through the deletion or alteration of the γ₁34.5 neurovirulence gene, the basis for the success of oHSV relies in part on the malignant silencing of cellular pathways critical for limiting these viruses in healthy host tissue. However, only recently have the molecular mechanisms underlying the success of these treatments begun to emerge. Further clarification of these mechanisms can strengthen rational design approaches to develop the next generation of oHSV. Herein, we review our current understanding of the molecular basis for tumor susceptibility to γ₁34.5-attenuated oHSV, with particular focus on the malignant suppression of nucleic acid sensing, along with strategies meant to improve the clinical efficacy of these therapeutic viruses.

The Effect of Herpes Simplex Virus-Type-1 (HSV-1) Oncolytic Immunotherapy on the Tumor Microenvironment

The development of cancer causes disruption of anti-tumor immunity required for surveillance and elimination of tumor cells. Immunotherapeutic strategies aim for the restoration or establishment of these anti-tumor immune responses. Cancer immunotherapies include immune checkpoint inhibitors (ICIs), adoptive cellular therapy (ACT), cancer vaccines, and oncolytic virotherapy (OVT). The clinical success of some of these immunotherapeutic modalities, including herpes simplex virus type-1 derived OVT, resulted in Food and Drug Administration (FDA) approval for use in treatment of human cancers. However, a significant proportion of patients do not respond or benefit equally from these immunotherapies. The creation of an immunosuppressive tumor microenvironment (TME) represents an important barrier preventing success of many immunotherapeutic approaches. Mechanisms of immunosuppression in the TME are a major area of current research. In this review, we discuss how oncolytic HSV affects the tumor microenvironment to promote anti-tumor immune responses. Where possible we focus on oncolytic HSV strains for which clinical data is available, and discuss how these viruses alter the vasculature, extracellular matrix and immune responses in the tumor microenvironment.

HSV-1 Oncolytic Viruses from Bench to Bedside: An Overview of Current Clinical Trials

Herpes simplex virus 1 (HSV-1) provides a genetic chassis for several oncolytic viruses (OVs) currently in clinical trials. Oncolytic HSV1 (oHSV) have been engineered to reduce neurovirulence and enhance anti-tumor lytic activity and immunogenicity to make them attractive candidates in a range of oncology indications. Successful clinical data resulted in the FDA-approval of the oHSV talimogene laherparepvec (T-Vec) in 2015, and several other variants are currently undergoing clinical assessment and may expand the landscape of future oncologic therapy options. This review offers a detailed overview of the latest results from clinical trials as well as an outlook on newly developed HSV-1 oncolytic variants with improved tumor selectivity, replication, and immunostimulatory capacity and related clinical studies.

The Double-Edged Sword Role of Viruses in Gastric Cancer

Due to its high morbidity and mortality, gastric cancer is a topic of a great concern throughout the world. Major ways of treatment are gastrectomy and chemotherapy, unfortunately they are not always successful. In a search for more efficient therapy strategies, viruses and their potential seem to be an important issue. On one hand, several oncogenic viruses have been noticed in the case of gastric cancer, making the positive treatment even more advantageous, but on the other, viruses exist with a potential therapeutic role in this malignancy.

Efficacy of a Third-Generation Oncolytic Herpes Virus G47Δ in Advanced Stage Models of Human Gastric Cancer

Advanced gastric cancer, especially scirrhous gastric cancer with peritoneal dissemination, remains refractory to conventional therapies. G47Δ, a third-generation oncolytic herpes simplex virus type 1, is an attractive novel therapeutic agent for solid cancer. In this study, we investigated the therapeutic potential of G47Δ for human gastric cancer. In vitro, G47Δ showed good cytopathic effects and replication capabilities in nine human gastric cancer cell lines tested. In vivo, intratumoral inoculations with G47Δ (2 × 10⁵ or 1 × 10⁶ plaque-forming units [PFU]) significantly inhibited the growth of subcutaneous tumors (MKN45, MKN74, and 44As3). To evaluate the efficacy of G47Δ for advanced-stage models of gastric cancer, we generated an orthotopic tumor model and peritoneal dissemination models of human scirrhous gastric cancer (MKN45-luc and 44As3Luc), which have features mimicking intractable scirrhous cancer patients. G47Δ (1 × 10⁶ PFU) was constantly efficacious whether administered intratumorally or intraperitoneally in the clinically relevant models. Notably, G47Δ injected intraperitoneally readily distributed to, and selectively replicated in, disseminated tumors. Furthermore, flow cytometric analyses of tumor-infiltrating cells in subcutaneous tumors revealed that intratumoral G47Δ injections markedly decreased M2 macrophages while increasing M1 macrophages and natural killer (NK) cells. These findings indicate the usefulness of G47Δ for treating human gastric cancer, including scirrhous gastric cancer and the ones in advanced stages.

Synergistic combination of oncolytic virotherapy with CAR T-cell therapy

For patients with advanced hematological malignancies the therapeutic landscape has been transformed by the emergence of adoptive cell transfer utilizing autologous chimeric antigen receptor (CAR)-redirected T-cells. However, solid tumors have proved far more resistant to this approach. Here, we summarize the numerous challenges faced by CAR T-cells designed to target solid tumors, highlighting, in particular, issues related to impaired trafficking, expansion, and persistence. In parallel, we draw attention to exciting developments in the burgeoning field of oncolytic virotherapy and posit strategies for the synergistic combination of oncolytic viruses with CAR T-cells to improve outcomes for patients with advanced solid tumors.

Oncolytic virotherapy in upper gastrointestinal tract cancers

Upper gastrointestinal tract malignancies are among the most challenging cancers with regard to response to treatment and prognosis. Cancers of the esophagus, stomach, pancreas, liver, and biliary tree have dismal 5-year survival, and very modest improvements in this rate have been made in recent times. Oncolytic viruses are being developed to address these malignancies, with a focus on high safety profiles and low off-target toxicities. Each viral platform has evolved to enhance oncolytic potency and the clinical response to either single-agent viral therapy or combined viral treatment with radiotherapy and chemotherapy. A panel of genomic alterations, chimeric proteins, and pseudotyped capsids are the breakthroughs for vector success. This article revisits developments for each viral platform to each tumor type, in an attempt to achieve maximum tumor selectivity. From the bench to clinical trials, the scope of this review is to highlight the beginnings of translational oncolytic virotherapy research in upper gastrointestinal tract malignancies and provide a bioengineering perspective of the most promising platforms.

Application of interferon modulators to overcome partial resistance of human ovarian cancers to VSV-GP oncolytic viral therapy

Previously, we described an oncolytic vesicular stomatitis virus variant pseudotyped with the nonneurotropic glycoprotein of the lymphocytic choriomeningitis virus, VSV-GP, which was highly effective in glioblastoma. Here, we tested its potency for the treatment of ovarian cancer, a leading cause of death from gynecological malignancies. Effective oncolytic activity of VSV-GP could be demonstrated in ovarian cancer cell lines and xenografts in mice; however, remission was temporary in most mice. Analysis of the innate immune response revealed that ovarian cancer cell lines were able to respond to and produce type I interferon, inducing an antiviral state upon virus infection. This is in stark contrast to published data for other cancer cell lines, which were mostly found to be interferon incompetent. We showed that in vitro this antiviral state could be reverted by combining VSV-GP with the JAK1/2-inhibitor ruxolitinib. In addition, for the first time, we report the in vivo enhancement of oncolytic virus treatment by ruxolitinib, both in subcutaneous as well as in orthotopic xenograft mouse models, without causing significant additional toxicity. In conclusion, VSV-GP has the potential to be a potent and safe oncolytic virus to treat ovarian cancer, especially when combined with an inhibitor of the interferon response.

Treatment of human hepatocellular carcinoma by the oncolytic herpes simplex virus G47delta

Background

Oncolytic herpes simplex virus (HSV) can replicate in and kill cancer cells while sparing the adjacent normal tissue. Hepatocellular carcinoma (HCC) is amongst the most common and lethal cancers, especially in Third World countries. In this study, the cytotoxicity of a third-generation oncolytic HSV, G47Δ, was investigated in different human HCC cell lines and in an immortalized human hepatic cell line. Additionally, subcutaneous models of HCC were established to evaluate the in vivo anti-tumor efficacy of G47Δ.

Methods

The HepG2, HepB, SMMC-7721, BEL-7404, and BEL-7405 human HCC cell lines and the HL-7702 human hepatic immortalized cell lines were infected with G47Δ at different multiplicities of infection (MOIs). The viability of infected cells was determined, and the G47Δ replication was identified by X-gal staining for LacZ expression. Two subcutaneous (s.c.) HCC tumor models of HCC were also established in Balb/c nude mice, which were intratumorally(i.t.) treated with either G47Δ or mock virus. Tumor volume and mouse survival times were documented.

Results

More than 95% of the HepG2, Hep3B,and SMMC-7721 HCC cells were killed on by day 5 after infection with a MOI’s of 0.01. For the HL-7702 human hepatic immortalized cells, 100% of the cells were killed on by day 5 after infection with a MOI’s of 0.01. The BEL-7404 HCC cell line was less susceptible with about 70% cells were killed by day 5 after infection with a MOI’s of 0.01. Whereas the BEL-7405 HCC cells were the least susceptible, with only 30% of the cells were killed. Both the SMMC-7721 and BEL-7404 cells form aggressive sc tumor models. G47Δ replicates in the tumors, such that most of the tumors regressed after the G47Δ-treatment, and treated tumor-bearing mice survived much longer than the control animals.

Conclusions

G47Δ effectively kills human HCC cells and an immortalized hepatic cell line at low MOI. Intra-tumor injection of G47Δ can induce a therapeutic effect and prolong the survival of treated mice bearing SMMC-7721 and BEL-7404 subcutaneously (s.c.) tumors. Thus, G47Δ may be useful as a novel therapeutic agent for HCC.

Use of miRNA response sequences to block off-target replication and increase the safety of an unattenuated, glioblastoma-targeted oncolytic HSV

Glioblastoma multiforme (GBM) is an aggressive brain cancer for which there is no effective treatment. Oncolytic HSV vectors (oHSVs) are attenuated lytic viruses that have shown promise in the treatment of human GBM models in animals, but their efficacy in early phase patient trials has been limited. Instead of attenuating the virus with mutations in virulence genes, we engineered four copies of the recognition sequence for miR-124 into the 3'UTR of the essential ICP4 gene to protect healthy tissue against lytic virus replication; miR-124 is expressed in neurons but not in glioblastoma cells. Following intracranial inoculation into nude mice, the miR-124-sensitive vector failed to replicate or show overt signs of pathogenesis. To address the concern that this safety feature may reduce oncolytic activity, we inserted the miR-124 response elements into an unattenuated, human receptor (EGFR/EGFRvIII)-specific HSV vector. We found that miR-124 sensitivity did not cause a loss of treatment efficiency in an orthotopic model of primary human GBM in nude mice. These results demonstrate that engineered miR-124 responsiveness can eliminate off-target replication by unattenuated oHSV without compromising oncolytic activity, thereby providing increased safety.

Immunogenic HSV-mediated oncolysis shapes the antitumor immune response and contributes to therapeutic efficacy

Within the oncolytic virus field, the extent of virus replication that is essential for immune stimulation to control tumor growth remains unresolved. Using infected cell protein 0 (ICP0)-defective oncolytic Herpes simplex virus type 1 (HSV-1) and HSV-2 viruses (dICP0 and dNLS) that show differences in their in vitro replication and cytotoxicity, we investigated the inherent features of oncolytic HSV viruses that are required for potent antitumor activity. In vitro, the HSV-2 vectors showed rapid cytotoxicity despite lower viral burst sizes compared to HSV-1 vectors. In vivo, although both of the dICP0 vectors initially replicated to a similar level, HSV-1 dICP0 was rapidly cleared from the tumors. In spite of this rapid clearance, HSV-1 dICP0 treatment conferred significant survival benefit. HSV-1 dICP0-treated tumors showed significantly higher levels of danger-associated molecular patterns that correlated with higher numbers of antigen-presenting cells within the tumor and increased antigen-specific CD8+ T-cell levels in the peripheral blood. This study suggests that, at least in the context of oncolytic HSV, the initial stages of immunogenic virus replication leading to activation of antitumor immunity are more important than persistence of a replicating virus within the tumor. This knowledge provides important insight for the design of therapeutically successful oncolytic viruses.

A rationally designed A34R mutant oncolytic poxvirus: improved efficacy in peritoneal carcinomatosis

Oncolytic poxviruses have demonstrated initial promising results in patients with cancer in clinical trials, yet further improvements are needed. It has been shown that a single point mutation in the A34R gene resulted in the production of more total progeny virus and more extracellular enveloped virus (EEV), a form that can be immune-evasive and with enhanced spread. We have genetically engineered a new oncolytic poxvirus (designated vA34R) by incorporating this mutated A34R gene into a viral backbone (vvDD) which was designed for tumor-selective replication. This rationally designed virus can evade neutralization from antipoxvirus antibodies and is highly cytotoxic to cancer cells. It demonstrates improved spread and increased replication within the peritoneal cavity resulting in improved antitumor effects in a peritoneal carcinomatosis (PC) model of MC38 colon cancer. Impressively, after carrier cell-mediated delivery in the preimmunized host, vA34R displayed high replication in tumor nodules yet low accumulation in normal tissues thus enhancing the therapeutic index leading to 70% long-term cures. These results demonstrate that vA34R gains an enhanced therapeutic index for PC via immune evasion, increased spread, and production of more progeny virus. Thus, vA34R may be a potent oncolytic virus (OV) for patients with PC, even after prior exposure to vaccinia virus (VV).

Oncolytic viruses in the treatment of cancer: a review of current strategies

Oncolytic viruses are live, replication-competent viruses that replicate selectively in tumor cells leading to the destruction of the tumor cells. Tumor-selective replicating viruses offer appealing advantages over conventional cancer therapy and are promising a new approach for the treatment of human cancer. The development of virotherapeutics is based on several strategies. Virotherapy is not a new concept, but recent technical advances in the genetic modification of oncolytic viruses have improved their tumor specificity, leading to the development of new weapons for the war against cancer. Clinical trials with oncolytic viruses demonstrate the safety and feasibility of an effective virotherapeutic approach. Strategies to overcome potential obstacles and challenges to virotherapy are currently being explored. Systemic administrations of oncolytic viruses will successfully extend novel treatment against a range of tumors. Combination therapy has shown some encouraging antitumor responses by eliciting strong immunity against established cancer.

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.

Real-time fluorescence imaging of abdominal, pleural, and lymphatic metastases

Virally-directed fluorescence imaging has the potential to revolutionize intra-operative oncologic staging and tumor resection. Many viruses genetically engineered to specifically infect tumor cells as cancer therapy can be further modified to have a visible marker gene for cancer staging. In this chapter, we describe such a herpes simplex virus (HSV) modified to be detected by fluorescence. Other viruses so designed can be similarly used in cancer detection and staging. Replication-competent, tumor-specific HSV NV1066 expresses green fluorescent protein (GFP) in infected cancer cells. One single dose of NV1066 administered via intratumor, intracavitary, or systemic injection can spread within and across body cavities to target tumor cells while sparing normal tissue cells from infection. Tumors otherwise invisible by conventional laparoscopy appear green with the use of an endoscope equipped with a fluorescent filter. Furthermore, with GFP expression easily visualized by stereomicroscopy, microscopic, and pathologic analysis is significantly enhanced. This chapter addresses NV1066-directed visualization of peritoneal, pleural, and lymphatic metastases. This chapter also provides protocols for the production of tumor models in various body cavities in rodents.

Characterization of herpes simplex virus 1 strains as platforms for the development of oncolytic viruses against liver cancer

BACKGROUND

Diverse oncolytic viruses (OV) are being designed for the treatment of cancer. The characteristics of the parental virus strains may influence the properties of these agents.

AIMS

To characterize two herpes simplex virus 1 strains (HSV-1 17syn(+) and HFEM) as platforms for virotherapy against liver cancer.

METHODS

The luciferase reporter gene was introduced in the intergenic region 20 locus of both HSV-1 strains, giving rise to the Cgal-Luc and H6-Luc viruses. Their properties were studied in hepatocellular carcinoma (HCC) cells in vitro. Biodistribution was monitored by bioluminescence imaging (BLI) in athymic mice and immune-competent Balb/c mice. Immunogenicity was studied by MHC-tetramer staining, in vivo killing assays and determination of specific antibody production. Intratumoural transgene expression and oncolytic effect were studied in HuH-7 xenografts.

RESULTS

The H6-Luc virus displayed a syncytial phenotype and showed higher cytolytic effect on some HCC cells. Upon intravenous or intrahepatic injection in mice, both viruses showed a transient transduction of the liver with rapid relocalization of bioluminescence in adrenal glands, spinal cord, uterus and ovaries. No significant differences were observed in the immunogenicity of these viruses. Local intratumoural administration caused progressive increase in transgene expression during the first 5 days and persisted for at least 2 weeks. H6-Luc achieved faster amplification of transgene expression and stronger inhibition of tumour growth than Cgal-Luc, although toxicity of these non-attenuated viruses should be reduced to obtain a therapeutic effect.

CONCLUSIONS

The syncytial H6-Luc virus has a strong oncolytic potential on human HCC xenografts and could be the basis for potent OV.

Oncolytic herpes simplex virus 1 encoding 15-prostaglandin dehydrogenase mitigates immune suppression and reduces ectopic primary and metastatic breast cancer in mice

Oncolytic herpes simplex virus 1 (HSV-1) viruses armed with immunomodulatory transgenes have shown potential for enhanced antitumor therapy by overcoming tumor-based immune suppression and promoting antitumor effector cell development. Previously, we reported that the new oncolytic HSV-1 virus, OncSyn (OS), engineered to fuse tumor cells, prevented tumor growth and metastasis to distal organs in the 4T1/BALB/c immunocompetent breast cancer mouse model, suggesting the elicitation of antitumor immune responses (Israyelyan et al., Hum. Gen. Ther. 18:5, 2007, and Israyelyan et al., Virol. J. 5:68, 2008). The OSV virus was constructed by deleting the OS viral host shutoff gene (vhs; UL41) to further attenuate the virus and permit dendritic cell activation and antigen presentation. Subsequently, the OSVP virus was constructed by inserting into the OSV viral genome a murine 15-prostaglandin dehydrogenase (15-PGDH) expression cassette, designed to constitutively express 15-PGDH upon infection. 15-PGDH is a tumor suppressor protein and the primary enzyme responsible for the degradation of prostaglandin E2 (PGE2), which is known to promote tumor development. OSVP, OSV, and OS treatment of 4T1 tumors in BALB/c mice effectively reduced primary tumor growth and inhibited metastatic development of secondary tumors. OSVP was able to significantly inhibit the development and accumulation of 4T1 metastatic tumor cells in the lungs of treated mice. Ex vivo analysis of immune cells following treatment showed increased inflammatory cytokine production and the presence of mature dendritic cells for the OSVP, OSV, and OS viruses. A statistically significant decrease in splenic myeloid-derived suppressor cells (MDSC) was observed only for OSVP-treated mice. These results show that intratumoral oncolytic herpes is highly immunogenic and suggest that 15-PGDH expression by OSVP enhanced the antitumor immune response initiated by viral infection of primary tumor cells, leading to reduced development of pulmonary metastases. The availability of the OSVP genome as a bacterial artificial chromosome allows for the rapid insertion of additional immunomodulatory genes that could further assist in the induction of potent antitumor immune responses against primary and metastatic tumors.

Fluorescence-assisted cytological testing (FACT): Ex Vivo viral method for enhancing detection of rare cancer cells in body fluids

Cytological analysis of body fluids is currently used for detecting cancer. The objective of this study was to determine if the herpes virus carrying an enhanced green fluorescent protein (EGFP) could detect rare cancer cells in body fluids against millions of normal cells. Human cancer cells suspended with normal murine cells were infected with NV1066 at a multiplicity of infection (MOI) of 0.5 and 1.0 for 18 h. Fluorescent microscopy and flow cytometry were used for EGFP detection of cancer cells. EGFP-expressing cells were confirmed as cancer cells with specific markers by immunohistochemistry staining. Limits of detection of cancer cells in body fluid were measured by serial dilutions. Applicability of technique was confirmed with samples from patients with malignant pleural effusions. NV1066 expressed EGFP in 111 human cancer cell lines detected by fluorescent microscopy at an MOI of 0.5. NV1066 selectively infected cancer cells and spared normal cells as confirmed by immunohistochemistry. Sensitivity of detecting fluorescent green cells was 92% (confidence interval [CI] 83% to 97%) at a ratio of 1 cancer cell to 1 million normal cells. EGFP-positive cells were detected by fluorescent microscopy in patients' malignant pleural effusion samples. Our data show proof of the concept that NV1066-induced EGFP expression allows detection of a single cancer cell against a background of 1 million normal cells. This method was demonstrated to be a reliable screening tool for human cancer cells in a suspension of normal murine cells as well as clinical specimens of malignant pleural effusions.

Adaptive antiviral immunity is a determinant of the therapeutic success of oncolytic virotherapy

Oncolytic virotherapy, the selective killing of tumor cells by oncolytic viruses (OVs), has emerged as a promising avenue of anticancer research. We have previously shown that KM100, a Herpes simplex virus type-1 (HSV) deficient for infected cell protein 0 (ICP0), possesses substantial oncolytic properties in vitro and has antitumor efficacy in vivo, in part by inducing antitumor immunity. Here, we illustrate through T-cell immunodepletion studies in nontolerized tumor-associated antigen models of breast cancer that KM100 treatment promotes antiviral and antitumor CD8(+) cytotoxic T-cell responses necessary for complete tumor regression. In tolerized tumor-associated antigen models of breast cancer, antiviral CD8(+) cytotoxic T-cell responses against infected tumor cells correlated with the induction of significant tumoristasis in the absence of tumor-associated antigen-specific CD8(+) cytotoxic T-cells. To enhance oncolysis, we tested a more cytopathic ICP0-null HSV and a vesicular stomatitis virus M protein mutant and found that despite improved in vitro replication, oncolysis in vivo did not improve. These studies illustrate that the in vitro cytolytic properties of OVs are poor prognostic indicators of in vivo antitumor activity, and underscore the importance of adaptive antiviral CD8(+) cytotoxic T-cells in effective cancer virotherapy.

Regional liver therapy using oncolytic virus to target hepatic colorectal metastases

The mortality of colorectal carcinoma often results from the progression of metastatic disease, which is predominantly hepatic. Although recent advances in surgical, locoregional, and systemic therapies have yielded modest improvements in survival, treatment of these aggressive lesions is limited to palliation for the vast majority of patients. Oncolytic viral therapy represents a promising novel therapeutic modality that has achieved tumor regression in several preclinical and clinical models. Evidence further suggests that locoregional viral administration may improve viral efficacy while minimizing toxicity. This study will review the theories behind hepatic arterial infusion of oncolytic virus, as well as herpes viral design, preclinical data, and clinical progress in regional liver therapy using oncolytic virus to treat hepatic colorectal carcinoma metastases.

A third-generation herpesvirus is effective against gastroesophageal cancer

BACKGROUND

Gastroesophageal cancer remains a leading cause of cancer deaths and is uniformly fatal in patients presenting with metastases and recurrence. This study sets out to determine the effect of a third-generation, replication-competent, oncolytic herpes simplex type 1 virus containing transgenes encoding for a fusogenic membrane glycoprotein and Fcy::Fur, against gastroesophageal cancer.

METHODS

The cytotoxic effect of the virus was tested on human gastroesophageal cancer cell lines OCUM-2MD3, MKN-45, AGS, MKN-1, MKN-74, and BE-3 at sequential multiplicities of infection (MOI). Cytotoxicity was measured using a lactate dehydrogenase assay. Viral replication was tested by serially diluting supernatants from viral infections and titering on VERO cells via standard plaque assay. Correlations of cytotoxicity and viral replication were also investigated.

RESULTS

All cell lines were susceptible to viral infection and demonstrated a dose-dependent effect, with greater and faster cytotoxicity at higher MOIs. Viral replication was supported in the cell lines tested, with peak titers by d 5, some supporting as high as >40,000× amplification. Cell lines with longer doubling times (>30 h) also achieved higher viral titers at a MOI of 0.1. Cell lines with shorter doubling times achieved 50% cell kill in fewer days, with an average of 2.3 d for cell lines with doubling times under 30 h compared with 4.4 d for cell lines with doubling times over 30 h.

CONCLUSION

These results suggest that this third-generation oncolytic herpesvirus can effectively infect and lyse gastroesophageal cancer cells and may provide a novel therapy against gastroesophageal cancer.

Effects of herpes simplex virus amplicon transduction on murine dendritic cells

The herpes simplex virus (HSV)-based amplicon is a versatile vaccine platform that has been preclinically vetted as a gene-based immunotherapeutic for cancer, HIV, and neurodegenerative disorders. Although it is well known that injection of dendritic cells (DCs) transduced ex vivo with helper virus-free HSV amplicon vectors expressing disease-relevant antigens induces antigen-specific immune responses, the cellular receptor(s) by which the amplicon virion gains entry into DCs, as well as the effects that viral vector transduction impinges on the physiological status of these cells, is less understood. Herein, we examine the effects of amplicon transduction on mouse bone marrow-derived DCs. We demonstrate that HSV-1 cellular receptors HveC and HveA are expressed on the cell surface of murine DCs, and that HSV amplicons transduce DCs at high efficiency (>90%) with minimal effects on cell viability. Transduction of dendritic cells with amplicons induces a transient DC maturation phenotype as represented by self-limited upregulation of MHCII and CD11c markers. Mature DCs are less sensitive to HSV amplicon transduction than immature DCs regarding DC-related surface marker maintenance. From this and our previous work, we conclude that HSV amplicons transduce DCs efficiently, but impart differential and transient physiological effects on mature and immature DC pools, which will facilitate fine-tuning of this vaccination platform and further exploit its potential in immunotherapy.

Fluorescence-expressing viruses allow rapid identification and separation of rare tumor cells in spiked samples of human whole blood

BACKGROUND

Finding and isolating rare tumor cells in blood allows for diagnosis of disseminated cancer and for molecular profiling to direct the choice of biologic therapy. We explored whether the candidate gene therapy virus NV1066-designed to specifically infect cancer cells and express green fluorescence protein (GFP)-can be used for rapid infection, identification, and isolation of rare circulating tumor cells (CTC) in human whole blood.

METHODS

Mixtures of human cancer cell lines and human whole blood were exposed to NV1066 or heat-inactivated virus, incubated, and then examined for GFP expression by fluorescence microscopy and flow cytometry. Fluorescence-assisted cell sorting (FACS) was used to determine the efficiency of virally assisted tumor cell isolation. Sorted cells were subsequently stained for carcinoembryonic antigen (CEA) to determine if cells isolated in this way would maintain sufficient cellular integrity for molecular characterization.

RESULTS

In our study, there was 100% specificity for detection of cancer cells. Detection was consistent even at the highest dilution tested (10 cancer cells in 10 ml whole blood). The processing involved simple incubation without the technical demands of immunohistochemistry. FACS allowed for rapid isolation of GFP-expressing cells. Cells isolated by this method can subsequently undergo molecular characterization.

CONCLUSION

Oncolytic herpes simplex virus mediated green fluorescence in combination with FACS is a novel technique for the identification and isolation of cancer cells in an experimental model of blood-borne metastases. This procedure is a promising method for improving our diagnosis, staging, and molecular profiling of cancer.

Relationship between 31P metabolites and oncolytic viral therapy sensitivity in human colorectal cancer xenografts

Background

Studies using phosphorus magnetic resonance spectroscopy (MRS) have pointed to the significance of phospholipid metabolite alterations as biochemical markers for tumour progression or therapy response.

Methods

Spectroscopic imaging was performed in colorectal flank tumours in nude mice. In vivo tumour doubling times for each cell line were measured. In vivo sensitivity of each tumour line to treatment with G207 and NV1020 oncolytic viruses was assessed. Correlations between viral sensitivity and tumour doubling time and phosphorus MRS were estimated.

Results

For G207 virus, in vitro cytotoxicity tests showed cell viability at multiplicities of infection (ratio of viral particles per tumour cell) of 0·1 on day 6 as follows: C85, less than 1 per cent; HCT8, 1 per cent; LS174T, 9 per cent; HT29, 18 per cent; and C18, 92 per cent. Respective values for NV1020 were 1, 18, 4, 18 and 86 per cent. The phosphoethanolamine to phosphocholine ratio was significantly lower in virus-sensitive than -insensitive cells, and was dependent on tumour doubling time.

Conclusion

Alterations in membrane phospholipid metabolites that relate to proliferation of cancer cells affect the efficacy of oncolytic viral therapy. MRS proved a highly sensitive non-invasive tool for predicting the efficacy of viruses.

Gene therapy: the end of the rainbow?

The increased understanding of the molecular basis of oral cancer has led to expectations that correction of the genetic defects will lead to improved treatments. Nevertheless, the first clinical trials for gene therapy of oral cancer occurred 20 years ago, and routine treatment is still not available. The major difficulty is that genes are usually delivered by virus vectors whose effects are weak and temporary. Viruses that replicate would be better, and the field includes many approaches in that direction. If any of these are effective in patients, then gene therapy will become available in the next few years. Without significant advances, however, the treatment of oral cancer by gene therapy will remain as remote as the legendary pot of gold at the end of the rainbow.

Regional administration of oncolytic Echovirus 1 as a novel therapy for the peritoneal dissemination of gastric cancer

The dissemination of malignant gastric cells to the peritoneum occurs frequently, usually as an early event in disease, and results in poor patient prognosis. Surgery and chemotherapy offer limited therapeutic success. The low-pathogenic human enterovirus, Echovirus 1 (EV1), is an oncolytic virus that selectively targets and destroys malignant prostate and ovarian cancer xenografts in vivo. Lytic EV1 infection requires the cell surface expression of alpha(2)beta(1), an integrin involved in the dissemination of gastric cancer cells to the peritoneum. Herein, we evaluated the capacity of EV1 for anti-neoplastic cell action in gastric peritoneal carcinomatosis. Flow cytometric analysis demonstrated that alpha(2)beta(1) was abundantly surface expressed on a panel of gastric cancer cell lines, rendering the majority of lines highly susceptible to in vitro lytic EV1 infection and supportive of efficient viral progeny production. A bioluminescent MKN-45-Luc SCID mouse model of peritoneal dissemination was developed to allow real-time non-invasive monitoring of peritoneal tumor burden. Employing this mouse model, we demonstrated a therapeutic dose-response for escalating oncolytic EV1 doses. Taken together, these results emphasize the exciting potential for EV1 as a single or adjunct therapy for the control of the peritoneal dissemination of gastric cancer.

A herpes oncolytic virus can be delivered via the vasculature to produce biologic changes in human colorectal cancer

Genetically engineered herpes simplex viruses (HSVs) can selectively infect and replicate in cancer cells, and are candidates for use as oncolytic therapy. This long-term report of a phase I trial examines vascular administration of HSV as therapy for cancer. Twelve subjects with metastatic colorectal cancer within the liver failing first-line chemotherapy were treated in four cohorts with a single dose (3 x 10(6) to 1 x 10(8) particles) of NV1020, a multimutated, replication-competent HSV. After hepatic arterial administration, subjects were observed for 4 weeks before starting intra-arterial chemotherapy. All patients exhibited progression of disease before HSV injection. During observation, levels of the tumor marker carcinoembryonic antigen (CEA) decreased (median % drop = 24%; range 13-74%; P < 0.02). One of three individuals at the 10(8) level showed a 39% radiologic decrease in tumor size by cross-section and 75% by volume. HSV infection was documented from liver tumor biopsies. After beginning regional chemotherapy, all patients demonstrated a further decrease in CEA (median 96%; range 50-98%; P < 0.008) and a radiologic partial response. Median survival for this group was 25 months. During follow-up, no signs of virus reactivation were found. Multimutated HSV can be delivered safely into the human bloodstream to produce selective infection of tumor tissues and biologic effects.

Comparison of intravenous versus intraperitoneal administration of oncolytic herpes simplex virus 1 for peritoneal carcinomatosis in mice

hrR3 is an oncolytic herpes simplex virus 1 (HSV-1) mutant that replicates preferentially in tumors compared with normal tissues. Portal venous administration of hrR3 in mice bearing diffuse colorectal carcinoma liver metastases significantly reduces tumor burden and prolongs animal survival. In this study, we compared survival benefit and biodistribution of hrR3 following intravenous (i.v.) administration versus intraperitoneal (i.p.) administration in immunocompetent mice bearing colon carcinoma peritoneal metastases. Mice bearing peritoneal metastases received 1 x 10(8) plaque-forming units hrR3 or mock-infected media every other day for three doses and were randomized to have the viruses administered by either an i.p. or i.v. route. Biodistribution was assessed by PCR amplification of HSV-1-specific sequences from tumor and normal tissues including the small bowel, liver, spleen, kidney, lung, heart and brain. LD(50) for i.p. administration was compared with the LD(50) for i.v. administration. In subsequent experiments, animals were monitored for survival. The frequency of HSV-1 detection in peritoneal tumors was similar in mice randomized to either i.p. or i.v. administration. However, i.p. administration resulted in a more restricted systemic biodistribution, with a reduced frequency of virus detected in the kidney, lung and heart. The LD(50) associated with i.p. administration was higher than that with i.v. administration. Tumor burden was more effectively reduced with i.p. compared with i.v. administration. Median survival following i.p. administration was approximately twice that observed with i.v. administration. I.p. administration of an HSV-1 oncolytic mutant is associated with a more restricted biodistribution, less toxicity and greater efficacy against peritoneal metastases compared with i.v. administration.

Herpes simplex virus NV1020 as a novel and promising therapy for hepatic malignancy

BACKGROUND

Patients with hepatic malignancy have a dismal prognosis with standard therapies. NV1020 is an oncolytic herpes simplex virus that has potential to be a safe and effective therapeutic agent for this disease.

OBJECTIVE

We set out to discuss the development of NV1020 as an oncolytic agent and explore the potential role of this particular virus in the setting of human hepatic cancer.

METHODS

The scope of this review includes an overview of preclinical experience with NV1020, as well as an examination of current standard and developing therapies for liver cancer. The primary focus, however, is on the safety and potential clinical efficacy of NV1020 against hepatic malignancy.

RESULTS/CONCLUSION

We have found that NV1020 is a safe, novel therapeutic agent for treatment of refractory hepatic malignancy.

Efficacy and safety of the oncolytic herpes simplex virus rRp450 alone and combined with cyclophosphamide

Oncolytic herpes simplex virus (oHSV) mutants are under development as anticancer therapeutics. One such vector, rRp450, is ICP6-deleted and expresses a prodrug enzyme for cyclophosphamide (CPA) (rat CYP2B1). Little is known about rRp450's toxicity profile, especially in combination with CPA. We tested rRp450/CPA for antitumor efficacy in an aggressive human xenograft sarcoma model, measured virus production in primary cells, and tested rRp450/CPA for safety in immunocompetent mice. CPA enhanced the antitumor efficacy of rRp450. Relative to wild-type HSV-1, rRp450 replication was attenuated approximately 10,000-fold in human primary hepatocytes, differentiated primary foreskin keratinocytes, and primary Schwann cells. In vivo, intravenous and intracranial (IC) rRp450 injection at the strength of 10(8) plaque-forming units (pfu) alone or followed 24 hours later by intraperitoneal (IP) CPA was well tolerated and had no significant effect clinically on blood counts or chemistries. By contrast, intravenous KOS was found to be uniformly neurotoxic at 10(5) and fatal at 10(6) pfu, and IC virus was fatal in most mice at 10(4) pfu. Low levels of virus DNA were detected in some organs following intravenous and IC virus injection, but were not significantly altered by CPA. HSV replication was not detected in reactivation studies of isolated organs. Our findings suggest rRp450/CPA is safe and warrants further study as a potential combination in anticancer therapeutics.

Feasibility of herpes simplex virus type 1 mutants labeled with radionuclides for tumor treatment

For over one hundred years, viruses have been recognized as capable of killing tumor cells. At present, people are still researching and constructing more suitable oncolytic viruses for treating different malignant tumors. Although extensive studies have demonstrated that herpes simplex virus type 1 (HSV-1) is the most potential oncolytic virus, therapies based on herpes simplex virus type 1 vectors still arouse bio-safety and risk management issues. Researchers have therefore introduced the new idea of treating cancer with HSV-1 mutants labeled with radionuclides, combining radionuclide and oncolytic virus therapies. This overview briefly summarizes the status and mechanisms by which oncolytic viruses kill tumor cells, discusses the application of HSV-1 and HSV-1 derived vectors for tumor therapy, and demonstrates the feasibility and prospect of HSV-1 mutants labeled with radionuclides for treating tumors.

[Oncolytic virotherapy: new strategies in oncology]

The introduction of new therapeutical approaches to the medical practice has never been an easy task. On the one hand, modern therapies have to fulfil the strict requirements of the industry, on the other, patients and therapists have usually high expectations towards them. Thus, the public's initial euphoric emotions can quickly turn into pessimism following the experience of the first complications and difficulties of the new therapeutic method. Regarding oncolytic virotherapy, the emerging troubles and the lack of complete success upon the first clinical trials also led to the rejection of this promising new approach to the treatment of cancer. In the last few decades, however, due to the advances in molecular and cell biology, oncolytic virotherapy has been put in the lime-light again, and some of the newly developed virotherapeutic agents have been tested in various clinical trials all around the world. This review focuses on the current situation of the field and summarizes the available results.

Tumor genotype determines susceptibility to oncolytic herpes simplex virus mutants: strategies for clinical application

Oncolytic Herpes simplex virus -1 (HSV-1) mutants based on deletion of the γ134.5 gene are promising therapies for cancer. Δγ134.5 mutant replication and cytolysis is tumor cell type specific and severely attenuated in normal tissues. The basis for attenuation lies in the activation of the protein kinase R (PKR)-mediated host cellular defense pathway, which inhibits protein synthesis in infected cells. Tumor cells which overexpress MAPK kinase (MEK) activity support robust replication of Δγ134.5 mutants via MEK-mediated inhibition of PKR, resulting in tumor oncolysis. Systemic delivery of γ134.5 mutants may allow selective targeting and destruction of metastases from a broad range of solid human tumors that overexpress MEK. Barriers to systemic HSV-1 oncolytic therapy include innate immunity, adaptive immunity and hepatic adsorption. Immunomodulating agents may overcome innate immunity to HSV-1-based vectors. Preclinical data combined with the pervasiveness of HSV-1 despite widespread immunity suggest that preexisting immunity may not eliminate oncolytic efficacy. In the future, biopsy-determined tumor MEK status may select patients for Δγ134.5 oncolytic therapy.

Effective treatment of human breast tumor in a mouse xenograft model with herpes simplex virus type 1 specifying the NV1020 genomic deletion and the gBsyn3 syncytial mutation enabling high viral replication and spread in breast cancer cells

A new oncolytic and fusogenic herpes simplex virus type 1 (HSV-1) was constructed on the basis of the wildtype HSV-1(F) strain. To provide for safety and tumor selectivity, the virus carried a large deletion including one of the two alpha4, gamma(1)34.5, alpha0 genes and the latency-associated transcript region. The gamma(1)34.5 gene, a major neurovirulence factor, was replaced by a gene cassette constitutively expressing the red fluorescent protein gene. Homologous recombination was used to transfer the fusogenic gBsyn3 mutation to the viral genome to produce the OncSyn virus. OncSyn causes extensive virus-induced cell fusion (syncytia) and replicates to higher titers than the parental Onc and HSV-1(F) strains in breast cancer cells. Biochemical analysis revealed that the OncSyn virus retains a stable genome and expresses all major viral glycoproteins. A xenograft mouse model system using MDA-MB-435S-luc (MM4L) human breast cancer cells constitutively expressing the luciferase gene implanted within the interscapular region of animals was used to test the ability of the virus to inactivate breast tumor cells in vivo. Seventy-two mice bearing MM4L breast cancer xenografts were randomly divided into three groups and given two rounds of three consecutive intratumoral injections of OncSyn, inactivated OncSyn, or phosphate-buffered saline 3 days apart. A single round of virus injections resulted in a drastic reduction of tumor sizes (p <or= 0.0001) and diminution of chemiluminescence emitted by the cancer cells (p <or= 0.0002). This effect was enhanced by a second round of virus injections into the tumors 3 days after the first round (p <or= 0.0001). Systematic necropsy and pathological evaluation of the primary tumors revealed that the single round of injections resulted in extensive necrosis of tumor cells (p <or= 0.0001), which was enhanced by the second round of injections (p <or= 0.0002). Internal organs were not affected by virus inoculation. Mouse weights were not significantly impacted by any treatment during the course of the entire study (p = 0.46). These results show that the attenuated, fusogenic, and oncolytic HSV-1(F) virus strain OncSyn may effectively treat human breast tumors in vivo.

Efficacy of oncolytic herpesvirus NV1020 can be enhanced by combination with chemotherapeutics in colon carcinoma cells

NV1020, an oncolytic herpes simplex virus type 1, can destroy colon cancer cells by selectively replicating within these cells, while sparing normal cells. NV1020 is currently under investigation in a clinical phase I/II trial as an agent for the treatment of colon cancer liver metastases, in combination with conventional chemotherapeutic agents such as 5-fluorouracil (5-FU), SN38 (the active metabolite of irinotecan), and oxaliplatin. To study the synergy of NV1020 and chemotherapy, cytotoxicity and viral replication were evaluated in vitro by treating various human and murine colon carcinoma cell lines, using a colorimetric viability assay, a clonogenic assay, and a plaque-forming assay. In vivo experiments, using a subcutaneous syngeneic CT-26 tumor model in BALB/c mice, were performed to determine the efficacy of combination therapy. In vitro studies showed that the efficacy of NV1020 on human colon carcinoma cell lines HT-29, WiDr, and HCT-116 was additively or synergistically enhanced in combination with 5-FU, SN38, or oxaliplatin. The sequence of application was not important and effects were still apparent after a 21-day incubation period. Three intra-tumoral treatments with NV1020 (1 x 10(7) plaque-forming units), followed by three subcutaneous treatments with 5-FU (50 mg/kg), resulted in substantially higher inhibition of tumor growth and prolongation of survival compared with monotherapies (NV1020/5-FU vs. NV1020, p = 0.027). On WiDr cells, reduced replication of NV1020, in combination with 5-FU, indicated that additive and synergistic effects of combination therapy must be independent from viral replication. These results suggest that NV1020, in combination with chemotherapy, is a promising therapy for treating patients with metastatic colorectal cancer of the liver. We hypothesize that infection of cells with NV1020 sensitizes the infected cells for the cytotoxic effect of the chemotherapeutics.

Nectin-1 is a marker of thyroid cancer sensitivity to herpes oncolytic therapy

CONTEXT

The prognosis for patients diagnosed with anaplastic thyroid cancer is dismal, with a median survival time of only 6 months. Novel therapies are needed for these and other thyroid cancers that are refractory to conventional therapy.

OBJECTIVES

Our goals were to assess the ability of an attenuated, replication-competent, oncolytic herpes virus (NV1023) to enter and lyse human thyroid cancers and determine whether herpes simplex virus receptor expression is a determinant of NV1023 efficacy.

DESIGN

A panel of 12 human thyroid cancer cell lines including anaplastic, medullary, follicular, and papillary cancers were exposed to NV1023 and assessed for susceptibility to viral entry and oncolysis. The expression of herpes simplex virus glycoprotein D receptors nectin-1 and herpes virus entry mediator was assessed by quantitative fluorescence-activated cell sorter and correlated with NV1023 entry and oncolysis.

RESULTS

There was significant variation in the ability of NV1023 to enter thyroid cancer cells as measured by lacZ expression. Thyroid cancer nectin-1 expression correlated strongly with NV1023 entry. Nectin-1 transfections and antibody receptor blocking studies validated the importance of nectin-1 for NV1023 entry. Follicular cancers were least sensitive to NV1023 oncolysis. All anaplastic, medullary, and papillary cancers tested exhibited greater than 85% cytotoxicity 7 d after exposure to NV1023 at multiplicity of infection 1, although oncolysis was variable at multiplicity of infection 0.01. Significant correlations between nectin-1 expression and NV1023 oncolysis were identified using Pearson's coefficients.

CONCLUSIONS

NV1023 causes significant cytotoxicity of anaplastic, medullary, and papillary thyroid cancers. Nectin-1 is a novel marker of thyroid cancer sensitivity to herpes oncolytic therapy that might guide patient selection for therapy.

Oncolytic viruses in cancer therapy

Oncolytic virotherapy is a promising form of gene therapy for cancer, employing nature’s own agents to find and destroy malignant cells. The purpose of this review is to provide an introduction to this very topical field of research and to point out some of the current observations, insights and ideas circulating in the literature. We have strived to acknowledge as many different oncolytic viruses as possible to give a broader picture of targeting cancer using viruses. Some of the newest additions to the panel of oncolytic viruses include the avian adenovirus, foamy virus, myxoma virus, yaba-like disease virus, echovirus type 1, bovine herpesvirus 4, Saimiri virus, feline panleukopenia virus, Sendai virus and the non-human coronaviruses. Although promising, virotherapy still faces many obstacles that need to be addressed, including the emergence of virus-resistant tumor cells.

Viral gene therapy

Cancer is a multigenic disorder involving mutations of both tumor suppressor genes and oncogenes. A large body of preclinical data, however, has suggested that cancer growth can be arrested or reversed by treatment with gene transfer vectors that carry a single growth inhibitory or pro-apoptotic gene or a gene that can recruit immune responses against the tumor. Many of these gene transfer vectors are modified viruses. The ability for the delivery of therapeutic genes, made them desirable for engineering virus vector systems. The viral vectors recently in laboratory and clinical use are based on RNA and DNA viruses processing very different genomic structures and host ranges. Particular viruses have been selected as gene delivery vehicles because of their capacities to carry foreign genes and their ability to efficiently deliver these genes associated with efficient gene expression. These are the major reasons why viral vectors derived from retroviruses, adenovirus, adeno-associated virus, herpesvirus and poxvirus are employed in more than 70% of clinical gene therapy trials worldwide. Because these vector systems have unique advantages and limitations, each has applications for which it is best suited. Retroviral vectors can permanently integrate into the genome of the infected cell, but require mitotic cell division for transduction. Adenoviral vectors can efficiently deliver genes to a wide variety of dividing and nondividing cell types, but immune elimination of infected cells often limits gene expression in vivo. Herpes simplex virus can deliver large amounts of exogenous DNA; however, cytotoxicity and maintenance of transgene expression remain as obstacles. AAV also infects many non-dividing and dividing cell types, but has a limited DNA capacity. This review discusses current and emerging virusbased genetic engineering strategies for the delivery of therapeutic molecules or several approaches for cancer treatment.

ReVOLT: radiation-enhanced viral oncolytic therapy

Viral oncolytic therapy has been pursued with renewed interest as the molecular basis of carcinogenesis and viral replication has been elucidated. Genetically engineered, attenuated viruses have been rationally constructed to achieve a therapeutic index in tumor cells compared with surrounding normal tissue. Many of these attenuated mutant viruses have entered clinical trials. Here we review the preclinical literature demonstrating the interaction of oncolytic viruses with ionizing radiation and provides a basis for future clinical trials.

Gene therapy of liver cancer

The application of gene transfer technologies to the treatment of cancer has led to the development of new experimental approaches like gene directed enzyme/pro-drug therapy (GDEPT), inhibition of oncogenes and restoration of tumor-suppressor genes. In addition, gene therapy has a big impact on other fields like cancer immunotherapy, anti-angiogenic therapy and virotherapy. These strategies are being evaluated for the treatment of primary and metastatic liver cancer and some of them have reached clinical phases. We present a review on the basis and the actual status of gene therapy approaches applied to liver cancer.

Radiation therapy potentiates effective oncolytic viral therapy in the treatment of lung cancer

BACKGROUND

Replication-competent oncolytic herpes simplex viruses with deletion of the gamma(1)34.5 gene preferentially replicate in and kill malignant cells. The gamma(1)34.5 gene codes for ICP 34.5, a protein that enhances viral replication, and is homologous to growth arrest and DNA damage protein 34 (GADD34), a radiation-inducible DNA repair gene. We hypothesized that radiation therapy may potentiate efficacy of oncolytic viral therapy by upregulating GADD34 and promoting viral replication.

METHODS

The A549 and H1299 lung cancer cell lines were infected with NV1066, an oncolytic herpes simplex virus, at multiplicities of infection (number of viral particles per tumor cell) of 0.1 to 0.5 in vitro with radiation (2 to 10 Gy) or without radiation. Viral replication was determined by plaque assay, cell-to-cell spread was determined by flow cytometry, cell kill was determined by lactate dehydrogenase assay, and GADD34 induction was determined by real-time reverse transcription-polymerase chain reaction and Western blot method. Evidence of synergistic cytotoxicity dependence with GADD34 induction is further confirmed by small inhibitory RNA inhibition of GADD34 expression.

RESULTS

Using both the isobologram method and combination index method of Chou and Talalay, significant synergism was demonstrated between radiation therapy and NV1066 both in vitro and in vivo. As a result of such synergism, a dose reduction for each agent (2- to 6,000-fold) can be accomplished for a wide range of therapeutic effect levels without sacrificing tumor cell kill. This effect is correlated with increased GADD34 expression and inhibited by transfection of small inhibitory RNA directed against GADD34.

CONCLUSIONS

These data provide the cellular basis for the clinical investigation of combined use of radiation therapy with oncolytic herpes simplex virus therapy in the treatment of lung cancer to achieve synergistic efficacy while minimizing dosage and toxicity.

Gene therapy for cancer treatment: past, present and future

The broad field of gene therapy promises a number of innovative treatments that are likely to become important in preventing deaths from cancer. In this review, we discuss the history, highlights and future of three different gene therapy treatment approaches: immunotherapy, oncolytic virotherapy and gene transfer. Immunotherapy uses genetically modified cells and viral particles to stimulate the immune system to destroy cancer cells. Recent clinical trials of second and third generation vaccines have shown encouraging results with a wide range of cancers, including lung cancer, pancreatic cancer, prostate cancer and malignant melanoma. Oncolytic virotherapy, which uses viral particles that replicate within the cancer cell to cause cell death, is an emerging treatment modality that shows great promise, particularly with metastatic cancers. Initial phase I trials for several vectors have generated excitement over the potential power of this technique. Gene transfer is a new treatment modality that introduces new genes into a cancerous cell or the surrounding tissue to cause cell death or slow the growth of the cancer. This treatment technique is very flexible, and a wide range of genes and vectors are being used in clinical trials with successful outcomes. As these therapies mature, they may be used alone or in combination with current treatments to help make cancer a manageable disease.