The replication-competent oncolytic herpes simplex mutant virus NV1066 is effective in the treatment of esophageal cancer

A Structure-Activity Relationship Study of Bimodal BODIPY-Labeled PSMA-Targeting Bioconjugates

The aim of this study was to identify a high-affinity BODIPY peptidomimetic that targets the prostate-specific membrane antigen (PSMA) as a potential bimodal imaging probe for prostate cancer. For the structure-activity study, several BODIPY (difluoroboron dipyrromethene) derivatives with varying spacers between the BODIPY dye and the PSMA Glu-CO-Lys binding motif were prepared. Corresponding affinities were determined by competitive binding assays in PSMA-positive LNCaP cells. One compound was identified with comparable affinity (IC50 =21.5±0.1 nM) to Glu-CO-Lys-Ahx-HBED-CC (PSMA-11) (IC50 =18.4±0.2 nM). Radiolabeling was achieved by Lewis-acid-mediated 19 F/18 F exchange in moderate molar activities (∼0.7 MBq nmol-1 ) and high radiochemical purities (>99 %) with mean radiochemical yields of 20-30 %. Cell internalization of the 18 F-labeled high-affinity conjugate was demonstrated in LNCaP cells showing gradual increasing PSMA-mediated internalization over time. By fluorescence microscopy, localization of the high-affinity BODIPY-PSMA conjugate was found in the cell membrane at early time points and also in subcellular compartments at later time points. In summary, a high-affinity BODIPY-PSMA conjugate has been identified as a suitable candidate for the development of PSMA-specific dual-imaging agents.

Fighting Fire With Fire: Oncolytic Virotherapy for Thoracic Malignancies

Thoracic malignancies are associated with high mortality rates. Conventional therapy for many of the patients with thoracic malignancies is obviated by a high incidence of locoregional recurrence and distant metastasis. Fortunately, developments in immunotherapy provide effective strategies for both local and systemic treatments that have rapidly advanced during the last decade. One promising approach to cancer immunotherapy is to use oncolytic viruses, which have the advantages of relatively high tumor specificity, selective replication-mediated oncolysis, enhanced antigen presentation, and potential for delivery of immunogenic payloads such as cytokines, with subsequent elicitation of effective antitumor immunity. Several oncolytic viruses including adenovirus, coxsackievirus B3, herpes virus, measles virus, reovirus, and vaccinia virus have been developed and applied to thoracic cancers in preclinical murine studies and clinical trials. This review discusses the current state of oncolytic virotherapy in lung cancer, esophageal cancer, and metastatic malignant pleural effusions and considers its potential as an emergent therapeutic for these patients.

Intraarterial delivery of virotherapy for glioblastoma

Oncolytic viruses (OVs) have been used in the treatment of cancer, in a focused manner, since the 1990s. These OVs have become popular in the treatment of several cancers but are only now gaining interest in the treatment of glioblastoma (GBM) in recent clinical trials. In this review, the authors discuss the unique applications of intraarterial (IA) delivery of OVs, starting with concepts of OV, how they apply to IA delivery, and concluding with discussion of the current ongoing trials. Several OVs have been used in the treatment of GBM, including specifically several modified adenoviruses. IA delivery of OVs has been performed in the hepatic circulation and is now being studied in the cerebral circulation to help enhance delivery and specificity. There are some interesting synergies with immunotherapy and IA delivery of OVs. Some of the shortcomings are discussed, specifically the systemic response to OVs and feasibility of treatment. Future studies can be performed in the preclinical setting to identify the ideal candidates for translation into clinical trials, as well as the nuances of this novel delivery method.

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.

Targeting Nucleotide Biosynthesis: A Strategy for Improving the Oncolytic Potential of DNA Viruses

The rapid growth of tumors depends upon elevated levels of dNTPs, and while dNTP concentrations are tightly regulated in normal cells, this control is often lost in transformed cells. This feature of cancer cells has been used to advantage to develop oncolytic DNA viruses. DNA viruses employ many different mechanisms to increase dNTP levels in infected cells, because the low concentration of dNTPs found in non-cycling cells can inhibit virus replication. By disrupting the virus-encoded gene(s) that normally promote dNTP biosynthesis, one can assemble oncolytic versions of these agents that replicate selectively in cancer cells. This review covers the pathways involved in dNTP production, how they are dysregulated in cancer cells, and the various approaches that have been used to exploit this biology to improve the tumor specificity of oncolytic viruses. In particular, we compare and contrast the ways that the different types of oncolytic virus candidates can directly modulate these processes. We limit our review to the large DNA viruses that naturally encode homologs of the cellular enzymes that catalyze dNTP biogenesis. Lastly, we consider how this knowledge might guide future development of oncolytic viruses.

Current status and future perspectives of fluorescence-guided surgery for cancer

Curative cancer surgery is dependent on the removal of all primary tumor and metastatic cancer cells. Preoperative imaging, intraoperative inspection and palpation, as well as pathological margin confirmation aid the surgeon, but these methods are lacking in sensitivity and can be highly subjective. Techniques in fluorescence-guided surgery (FGS) are emerging that selectively illuminate cancer cells, enhancing the distinction between tumors and surrounding tissues with the potential for single-cell sensitivity. FGS enhances tumor detection, surgical navigation, margin confirmation, and in some cases can be combined with therapeutic techniques to eliminate microscopic disease. In this review, we describe the preclinical developments and currently-used techniques for FGS.

Ratiometric activatable cell-penetrating peptides label pancreatic cancer, enabling fluorescence-guided surgery, which reduces metastases and recurrence in orthotopic mouse models

BACKGROUND

The aim of this study was to evaluate the efficacy of using matrix metalloproteinase-2 (MMP-2) and matrix metalloproteinase-9 (MMP-9)-cleavable ratiometric activatable cell-penetrating peptides (RACPPs) conjugated to Cy5 and Cy7 fluorophores to accurately label pancreatic cancer for fluorescence-guided surgery (FGS) in an orthotopic mouse model.

METHODS

Orthotopic mouse models were established using MiaPaCa-2-GFP human pancreatic cancer cells. Two weeks after implantation, tumor-bearing mice were randomized to conventional white light reflectance (WLR) surgery or FGS. FGS was performed at far-red and infrared wavelengths with a customized fluorescence-dissecting microscope 2 h after injection of MMP-2 and MMP-9-cleavable RACPPs. Green fluorescence imaging of the GFP-labeled cancer cells was used to assess the effectiveness of surgical resection and monitor recurrence. At 8 weeks, mice were sacrificed to evaluate tumor burden and metastases.

RESULTS

Mice in the WLR group had larger primary tumors than mice in the FGS group at termination [1.72 g ± standard error (SE) 0.58 vs. 0.25 g ± SE 0.14; respectively, p = 0.026). Mean disease-free survival was significantly lengthened from 5.33 weeks in the WLR group to 7.38 weeks in the FGS group (p = 0.02). Recurrence rates were lower in the FGS group than in the WLR group (38 vs. 73 %; p = 0.049). This translated into lower local and distant recurrence rates for FGS compared to WLR (31 vs. 67 for local recurrence, respectively, and 25 vs. 60 % for distant recurrence, respectively). Metastatic tumor burden was significantly greater in the WLR group than in the FGS group (96.92 mm(2) ± SE 52.03 vs. 2.20 mm(2) ± SE 1.43; respectively, χ (2) = 5.455; p = 0.02).

CONCLUSIONS

RACPPs can accurately and effectively label pancreatic cancer for effective FGS, resulting in better postresection outcomes than for WLR surgery.

Fluorescence-guided surgery and fluorescence laparoscopy for gastrointestinal cancers in clinically-relevant mouse models

There are many challenges that face surgeons when attempting curative resection for gastrointestinal cancers. The ability to properly delineate tumor margins for complete resection is of utmost importance in achieving cure and giving the patient the best chance of prolonged survival. Targeted tumor imaging techniques have gained significant interest in recent years to enable better identification of tumor lesions to improve diagnosis and treatment of cancer from preoperative staging modalities to optimizing the surgeon's ability to visualize tumor margins at the initial operation. Using unique characteristics of the tumor to fluorescently label the tissue can delineate tumor margins from normal surrounding tissue, allowing improved precision of surgical resection. In this paper, different methods of fluorescently labeling native tumor are discussed as well as the development of fluorescence laparoscopy and the potential role for fluorescence-guided surgery in the treatment of gastrointestinal cancers.

Tumor-specific fluorescence antibody imaging enables accurate staging laparoscopy in an orthotopic model of pancreatic cancer

BACKGROUND/AIMS

Laparoscopy is important in staging pancreatic cancer, but false negatives remain problematic. Making tumors fluorescent has the potential to improve the accuracy of staging laparoscopy.

METHODOLOGY

Orthotopic and carcinomatosis models of pancreatic cancer were established with BxPC-3 human pancreatic cancer cells in nude mice. Alexa488-antiCEA conjugates were injected via tail vein 24 hours prior to laparoscopy. Mice were examined under bright field laparoscopic (BL) and fluorescence laparoscopic (FL) modes. Outcomes measured included time to identification of primary tumor for the orthotopic model and number of metastases identified within 2 minutes for the carcinomatosis model.

RESULTS

FL enabled more rapid and accurate identification and localization of primary tumors and metastases than BL. Using BL took statistically significantly longer time than FL (p<0.0001, fold change and 95% CI for BL vs. FL: 8.12 (4.54,14.52)). More metastatic lesions were detected and localized under FL compared to BL and with greater accuracy, with sensitivities of 96% vs. 40%, respectively, when compared to control. FL was sensitive enough to detect metastatic lesions <1mm.

CONCLUSIONS

The use of fluorescence laparoscopy with tumors labeled with fluorophore-conjugated anti-CEA antibody permits rapid detection and accurate localization of primary and metastatic pancreatic cancer in an orthotopic model. The results of the present report demonstrate the future clinical potential of fluorescence laparoscopy.

Combination of pet imaging with viral vectors for identification of cancer metastases

There are three main ways for dissemination of solid tumors: direct invasion, lymphatic spread and hematogenic spread. The presence of metastases is the most significant factor in predicting prognosis and therefore evidence of metastases will influence decision-making regarding treatment. Conventional imaging techniques are limited in the evaluation and localization of metastases due to their restricted ability to identify subcentimeter neoplastic disease. Hence, there is a need for an effective noninvasive modality that can accurately identify occult metastases in cancer patients. One such method is the combination of positron emission tomography (PET) with vectors designed for delivery of reporter genes into target cells. Vectors expressing the herpes simplex virus-1 thymidine kinase (HSV1-tk) reporter system have recently been shown to allow localization of micrometastases in animal models of cancer using non invasive imaging. Combination of HSV1-tk and PET imaging is based on the virtues of vectors which can carry and selectively express the HSV1-tk reporter gene in a variety of cancer cells but not in normal tissue. A radioactive tracer which is applied systemically is phosphorylated by the HSV1-tk enzyme, and as a consequence, the tracer accumulates in proportion to the level of HSV1-tk expression which can be imaged by PET. In this paper we review the recent developments in molecular imaging of micrometastases using replication-competent viral or nonviral vectors carrying the HSV1-tk gene using PET imaging. These diagnostic paradigms introduce an advantageous new concept in noninvasive molecular imaging with the potential benefits for improving patient care by providing guidance for therapy to patients with risk for metastases.

An LED light source and novel fluorophore combinations improve fluorescence laparoscopic detection of metastatic pancreatic cancer in orthotopic mouse models

BACKGROUND

The aim of this study was to improve fluorescence laparoscopy of pancreatic cancer in an orthotopic mouse model with the use of a light-emitting diode (LED) light source and optimal fluorophore combinations.

STUDY DESIGN

Human pancreatic cancer models were established with fluorescent FG-RFP, MiaPaca2-GFP, BxPC-3-RFP, and BxPC-3 cancer cells implanted in 6-week-old female athymic mice. Two weeks postimplantation, diagnostic laparoscopy was performed with a Stryker L9000 LED light source or a Stryker X8000 xenon light source 24 hours after tail-vein injection of CEA antibodies conjugated with Alexa 488 or Alexa 555. Cancer lesions were detected and localized under each light mode. Intravital images were also obtained with the OV-100 Olympus and Maestro CRI Small Animal Imaging Systems, serving as a positive control. Tumors were collected for histologic analysis.

RESULTS

Fluorescence laparoscopy with a 495-nm emission filter and an LED light source enabled real-time visualization of the fluorescence-labeled tumor deposits in the peritoneal cavity. The simultaneous use of different fluorophores (Alexa 488 and Alexa 555), conjugated to antibodies, brightened the fluorescence signal, enhancing detection of submillimeter lesions without compromising background illumination. Adjustments to the LED light source permitted simultaneous detection of tumor lesions of different fluorescent colors and surrounding structures with minimal autofluorescence.

CONCLUSIONS

Using an LED light source with adjustments to the red, blue, and green wavelengths, it is possible to simultaneously identify tumor metastases expressing fluorescent proteins of different wavelengths, which greatly enhanced the signal without compromising background illumination. Development of this fluorescence laparoscopy technology for clinical use can improve staging and resection of pancreatic cancer.

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.

Expression of RNA interference triggers from an oncolytic herpes simplex virus results in specific silencing in tumour cells in vitro and tumours in vivo

Background

Delivery of small interfering RNA (siRNA) to tumours remains a major obstacle for the development of RNA interference (RNAi)-based therapeutics. Following the promising pre-clinical and clinical results with the oncolytic herpes simplex virus (HSV) OncoVEX^GM-CSF, we aimed to express RNAi triggers from oncolytic HSV, which although has the potential to improve treatment by silencing tumour-related genes, was not considered possible due to the highly oncolytic properties of HSV.

Methods

To evaluate RNAi-mediated silencing from an oncolytic HSV backbone, we developed novel replicating HSV vectors expressing short-hairpin RNA (shRNA) or artificial microRNA (miRNA) against the reporter genes green fluorescent protein (eGFP) and β-galactosidase (lacZ). These vectors were tested in non-tumour cell lines in vitro and tumour cells that are moderately susceptible to HSV infection both in vitro and in mice xenografts in vivo. Silencing was assessed at the protein level by fluorescent microscopy, x-gal staining, enzyme activity assay, and western blotting.

Results

Our results demonstrate that it is possible to express shRNA and artificial miRNA from an oncolytic HSV backbone, which had not been previously investigated. Furthermore, oncolytic HSV-mediated delivery of RNAi triggers resulted in effective and specific silencing of targeted genes in tumour cells in vitro and tumours in vivo, with the viruses expressing artificial miRNA being comprehensibly more effective.

Conclusions

This preliminary data provide the first demonstration of oncolytic HSV-mediated expression of shRNA or artificial miRNA and silencing of targeted genes in tumour cells in vitro and in vivo. The vectors developed in this study are being adapted to silence tumour-related genes in an ongoing study that aims to improve the effectiveness of oncolytic HSV treatment in tumours that are moderately susceptible to HSV infection and thus, potentially improve response rates seen in human clinical trials.

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.

Imaging of lymph node micrometastases using an oncolytic herpes virus and [F]FEAU PET

Background

In patients with melanoma, knowledge of regional lymph node status provides important information on outlook. Since lymph node status can influence treatment, surgery for sentinel lymph node (SLN) biopsy became a standard staging procedure for these patients. Current imaging modalities have a limited sensitivity for detection of micrometastases in lymph nodes and, therefore, there is a need for a better technique that can accurately identify occult SLN metastases.

Methodology/Principal Findings

B16-F10 murine melanoma cells were infected with replication-competent herpes simplex virus (HSV) NV1023. The presence of tumor-targeting and reporter-expressing virus was assessed by [¹⁸F]-2′-fluoro-2′-deoxy-1-β-D-β-arabinofuranosyl-5-ethyluracil ([¹⁸F]FEAU) positron emission tomography (PET) and confirmed by histochemical assays. An animal foot pad model of melanoma lymph node metastasis was established. Mice received intratumoral injections of NV1023, and 48 hours later were imaged after i.v. injection of [¹⁸F]FEAU. NV1023 successfully infected and provided high levels of lacZ transgene expression in melanoma cells. Intratumoral injection of NV1023 resulted in viral trafficking to melanoma cells that had metastasized to popliteal and inguinal lymph nodes. Presence of virus-infected tumor cells was successfully imaged with [¹⁸F]FEAU-PET, that identified 8 out of 8 tumor-positive nodes. There was no overlap between radioactivity levels (lymph node to surrounding tissue ratio) of tumor-positive and tumor-negative lymph nodes.

Conclusion/Significance

A new approach for imaging SLN metastases using NV1023 and [¹⁸F]FEAU-PET was successful in a murine model. Similar studies could be translated to the clinic and improve the staging and management of patients with melanoma.

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.

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.

Myxoma virus is oncolytic for human pancreatic adenocarcinoma cells

BACKGROUND

Viral oncolytic therapy, which seeks to exploit the use of live viruses to treat cancer, has shown promise in the treatment of cancers resistant to conventional anticancer therapies. Among the most difficult to treat cancers is advanced pancreatic adenocarcinoma. Our study investigates the ability of a novel oncolytic agent, myxoma virus, to infect, productively replicate in, and kill human pancreatic cancer cells in vitro.

METHODS

The myxoma virus vMyxgfp was tested against a panel of human pancreatic adenocarcinoma cell lines. Infectivity, viral proliferation, and tumor cell kill were assessed.

RESULTS

Infection of tumor cells was assessed by expression of the marker gene enhanced green fluorescent protein (e-GFP). vMyxgfp had the ability to infect all pancreatic cancer cell lines tested. Killing of tumor cells varied among the 6 cell lines tested, ranging from >90% cell kill at 7 days for the most sensitive Panc-1 cells, to 39% in the most resistant cell line Capan-2. Sensitivity correlated to replication of virus, and was found to maximally exhibit a four-log increase in foci-forming units for the most sensitive Panc-1 cells within 72 h.

CONCLUSION

Our study demonstrates for the first time the ability of the myxoma virus to productively infect, replicate in, and lyse human pancreatic adenocarcinoma cells in vitro. These data encourage further investigation of this virus, which is pathogenic only in rabbits, for treatment of this nearly uniformly fatal cancer.

Nectin-1 Expression by Squamous Cell Carcinoma is a Predictor of Herpes Oncolytic Sensitivity

Oncolytic viruses based on herpes simplex virus type 1 (HSV-1) are able to infect and lyse a variety of malignant cell lines. However, there is variability in the degree of tumor susceptibility, and the cancer cell determinants of HSV sensitivity are poorly defined. Nectin-1 is a cell surface adhesion molecule that functions as a cellular receptor to HSV envelope glycoprotein D (gD). We assessed tumor nectin-1 expression as a predictor of oncolytic HSV sensitivity. A panel of human squamous carcinoma cell lines was evaluated for viral entry, replication, and cytotoxicity to an attenuated, replication-competent, oncolytic HSV (NV1023). Potential tumor determinants of HSV sensitivity were assessed, including nectin-1, herpes viral entry mediator, total gD receptor expression, S-phase fraction, and doubling time. Significant correlations between nectin-1 expression measured by quantitative fluorescence-activated cell sorting and viral sensitivity measures were identified using Pearson's coefficients. Cancer cell nectin-1 receptor blockade and nectin-1 transfection led to inhibition and enhancement of NV1023 viral entry, respectively. Cell lines with varying nectin-1 expression showed corresponding sensitivity to NV1023 therapy in vivo. Immunohistochemistry for nectin-1 was inversely related to E-cadherin staining, suggesting increased herpes sensitivity of E-cadherin-deficient tumors. These results suggest that nectin-1 may be used as a marker to predict the sensitivity of a tumor to herpes oncolytic therapy.

Intraoperative localization of lymph node metastases with a replication-competent herpes simplex virus

OBJECTIVES

Lymph node status is the most important prognostic factor determining recurrence and survival in patients with mesothelioma and other thoracic malignancies. Accurate localization of lymph node metastases is therefore necessary to improve selection of resectable and curable patients for surgical intervention. This study investigates the potential to identify lymph node metastases intraoperatively by using herpes-guided cancer cell-specific expression of green fluorescent protein.

METHODS

After infection with NV1066, a herpes simplex virus carrying green fluorescent protein transgene, human mesothelioma cancer cell lines were assessed for cancer cell-specific infection, green fluorescent protein expression, viral replication, and cytotoxicity. Murine models of lymphatic metastasis were established by means of surgical implantation of cancer cells into the preauricular (drainage to cervical lymph nodes) and pleural (mediastinal and retroperitoneal lymph nodes) spaces of athymic mice. Fluorescent thoracoscopy, laparoscopy, and stereomicroscopy were used to localize lymph node metastases that were confirmed by means of immunohistochemistry.

RESULTS

In vitro NV1066 infected, replicated (5- to 17,000-fold), and expressed green fluorescent protein in all cancer cells, even when infected at a low ratio of one viral plaque-forming unit per 100 tumor cells. In vivo NV1066 injected into primary tumors was able to locate and infect lymph node metastases producing green fluorescent protein that was visualized by means of fluorescent imaging. Histology confirmed lymphatic metastases, and immunohistochemistry confirmed viral presence in regions that expressed green fluorescent protein.

CONCLUSIONS

Herpes virus-guided cancer cell-specific production of green fluorescent protein can facilitate accurate localization of lymph node metastases. Fluorescent filters that detect green fluorescent protein can be incorporated into operative scopes to precisely localize and biopsy lymph node metastases.

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.

Minimally invasive localization of oncolytic herpes simplex viral therapy of metastatic pleural cancer

Herpes simplex virus-1 (HSV-1) oncolytic therapy and gene therapy are promising treatment modalities against cancer. NV1066, one such HSV-1 virus, carries a marker gene for enhanced green fluorescent protein (EGFP). The purpose of this study was to determine whether NV1066 is cytotoxic to lung cancer and whether EGFP is a detectable marker of viral infection in vitro and in vivo. We further investigated whether EGFP expression in infected cells can be used to localize the virus and to identify small metastatic tumor foci (<1 mm) in vivo by means of minimally invasive endoscopic systems equipped with fluorescent filters. In A549 human lung cancer cells, in vitro viral replication was determined by plaque assay, cell kill by LDH release assay, and EGFP expression by flow cytometry. In vivo, A549 cells were injected into the pleural cavity of athymic mice. Mice were treated with intrapleural injection of NV1066 or saline and examined for EGFP expression in tumor deposits using a stereomicroscope or a fluorescent thoracoscopic system. NV1066 replicated in, expressed EGFP in infected cells and killed tumor cells in vitro. In vivo, treatment with intrapleural NV1066 decreased pleural disease burden, as measured by chest wall nodule counts and organ weights. EGFP was easily visualized in tumor deposits, including microscopic foci, by fluorescent thoracoscopy. NV1066 has significant oncolytic activity against a human NSCLC cell line and is effective in limiting the progression of metastatic disease in an in vivo orthotopic model. By incorporating fluorescent filters into endoscopic systems, a minimally invasive means for diagnosing small metastatic pleural deposits and localization of viral therapy for thoracic malignancies may be developed using the EGFP marker gene inserted in oncolytic herpes simplex viruses.

Imaging and therapy of malignant pleural mesothelioma using replication-competent herpes simplex viruses

BACKGROUND

Malignant pleural mesothelioma (MPM) is an aggressive cancer that is refractory to current treatment modalities. Oncolytic herpes simplex viruses (HSV) used for gene therapy are genetically engineered, replication-competent viruses that selectively target tumor cells while sparing normal host tissue. The localized nature, the potential accessibility and the relative lack of distant metastasis make MPM a particularly suitable disease for oncolytic viral therapy.

METHODS

The infectivity, selective replication, vector spread and cytotoxic ability of three oncolytic HSV: G207, NV1020 and NV1066, were tested against eleven pathological types of MPM cell lines including those that are resistant to radiation therapy, gemcitabine or cisplatin. The therapeutic efficacy and the effect on survival of NV1066 were confirmed in a murine MPM model.

RESULTS

All three oncolytic HSV were highly effective against all the MPM cell lines tested. Even at very low concentrations of MOI 0.01 (MOI: multiplicity of viral infection, ratio of viral particles per cancer cell), HSV were highly effective against MPM cells that are resistant to radiation, gemcitabine and cisplatin. NV1066, an oncolytic HSV that expresses green fluorescent protein (GFP), was able to delineate the extent of the disease in a murine model of MPM due to selective infection and expression of GFP in tumor cells. Furthermore, NV1066 was able to reduce the tumor burden and prolong survival even when treatment was at an advanced stage of the disease.

CONCLUSION

These findings support the continued investigation of oncolytic HSV as potential therapy for patients with therapy-resistant MPM.

Real-time intraoperative detection of breast cancer axillary lymph node metastases using a green fluorescent protein-expressing herpes virus

OBJECTIVE

To investigate the use of a green fluorescent protein (GFP)-expressing oncolytic herpes virus to enable real-time intraoperative detection of breast cancer lymph node metastases.

SUMMARY BACKGROUND DATA

Axillary lymph node status is the most important factor determining treatment, recurrence, and overall survival for women with breast cancer. The current methods of determining nodal status, however, have limitations. NV1066 is a novel oncolytic herpes viral strain that specifically infects cancer cells and expresses GFP.

METHODS

Seven human breast cancer cell lines were infected in vitro with NV1066 and assessed for GFP expression, viral replication, and cytotoxicity. An in vivo model of breast cancer lymphatic metastasis was established in mice. Tumor-bearing mice were treated with NV1066 via injection into the primary tumor. Axillary lymph nodes were analyzed using an in vivo fluorescent imaging system. Histologic and molecular assessment of lymph nodes were performed using immunohistochemistry and reverse transcriptase PCR and operating characteristics were determined.

RESULTS

NV1066 infected, expressed GFP, replicated within, and killed all human breast cancer cell lines in vitro. Injection of NV1066 into primary breast tumors resulted in viral transit to axillary lymph nodes, infection of lymphatic metastases, and GFP expression that was visualized with in vivo fluorescent imaging. Histologic and molecular confirmation demonstrated favorable operating characteristics of this method (sensitivity 80%; specificity 96%).

CONCLUSIONS

We introduce a novel, sensitive, and specific method of lymphatic mapping that utilizes NV1066-guided cancer cell-specific viral production of GFP to enable real-time intraoperative detection of lymphatic metastases.

Triple combination of oncolytic herpes simplex virus-1 vectors armed with interleukin-12, interleukin-18, or soluble B7-1 results in enhanced antitumor efficacy

Conditionally replicating herpes simplex virus-1 (HSV-1) vectors are promising therapeutic agents for cancer. Insertion of therapeutic transgenes into the viral genome should confer desired anticancer functions in addition to oncolytic activities. Herein, using bacterial artificial chromosome and two recombinase-mediated recombinations, we simultaneously created four "armed" oncolytic HSV-1, designated vHsv-B7.1-Ig, vHsv-interleukin (IL)-12, vHsv-IL-18, and vHsv-null, which express murine soluble B7.1 (B7.1-Ig), murine IL-12, murine IL-18, and no transgene, respectively. These vHsv vectors possess deletions in the gamma34.5 genes and contain the green fluorescent protein gene as a histochemical marker and the immunostimulatory transgene inserted in the deleted ICP6 locus. The vHsv showed similar replicative capabilities in vitro. The in vivo efficacy was tested in A/J mice harboring s.c. tumors of syngeneic and poorly immunogenic Neuro2a neuroblastoma. The triple combination of vHsv-B7.1-Ig, vHsv-IL-12, and vHsv-IL-18 exhibited the highest efficacy among all single vHsv or combinations of two viruses. Combining 1 x 10(5) plaque-forming units each of the three armed viruses showed stronger antitumor activities than any single armed virus at 3 x 10(5) plaque-forming units in inoculated tumors as well as in noninoculated remote tumors. Studies using athymic mice indicated that this enhancement of antitumor efficacy was likely mediated by T-cell immune responses. The combined use of multiple oncolytic HSV-1 armed with different immunostimulatory genes may be a useful strategy for cancer therapy.

Real-time diagnostic imaging of tumors and metastases by use of a replication-competent herpes vector to facilitate minimally invasive oncological surgery

Current efforts on expanding minimally invasive techniques into the realm of oncological surgery are hindered by lack of accurate visualization of tumor margins and failure to detect micro metastases in real time. We used a systemic delivery of a herpes viral vector with cancer-selective infection and replication to precisely differentiate between normal and malignant tissue. NV1066 is a genetically modified, replication-competent herpes simplex virus carrying a transgene for enhanced green fluorescent protein (GFP). We tested the potential of NV1066 in delineating tumor tissue in vitro and in vivo in a wide range of cancers and whether NV1066-induced GFP expression can detect small foci of tumors and metastases in in vivo models using an operating endoscope with fluorescent filters. Our findings indicate that NV1066 can be used for real-time intraoperative imaging and enhanced detection of early cancers and metastases. We demonstrate that a single dose of NV1066, administered either locally (intratumoral or intracavitary) or systemically, will detect loco-regional and distant disease throughout the body. Such cancer selectivity is confirmed in 110 types of cancer cells from 16 different primary organs. Fluorescence-aided minimally invasive endoscopy revealed microscopic tumor deposits unrecognized by conventional laparoscopy/thoracoscopy. Furthermore, NV1066 ability to transit and infect tumor and metastases is proven in syngenic and transplanted tumors in different animal models, both immunocompetent and immunodeficient. Cancer-selective GFP expression is confirmed by histology, immunohistochemistry, and qRT-PCR. These studies form the basis for real-time, intraoperative diagnostic imaging of tumor and metastases by minimally invasive endoscopic technology.

Virally-directed fluorescent imaging (VFI) can facilitate endoscopic staging

BACKGROUND

Replication-competent, tumor specific herpes simplex virus NV1066 expresses green fluorescent protein (GFP) in infected cancer cells. We sought to determine the feasibility of GFP-guided imaging technology in the intraoperative detection of small tumor nodules.

METHODS

Human cancer cell lines were infected with NV1066 at multiplicities of infection of 0.01, 0.1 and 1. Cancer cell specific infectivity, vector spread and GFP signal intensity were measured by flow cytometry and time-lapse digital imaging (in vitro); and by use of a stereomicroscope and endoscope equipped with a fluorescent filter (in vivo).

RESULTS

NV1066 infected all cancer cell lines and expressed GFP at all MOIs. GFP signal was significantly higher than the autofluorescence of normal cells. One single dose of NV1066 spread within and across body cavities and selectively infected tumor nodules sparing normal tissue. Tumor nodules undetectable by conventional thoracoscopy and laparoscopy were identified by GFP fluorescence.

CONCLUSION

Virally-directed fluorescent imaging (VFI) is a real-time novel molecular imaging technology that has the potential to enhance the intraoperative detection of endoluminal or endocavitary tumor nodules.

Enhanced nectin-1 expression and herpes oncolytic sensitivity in highly migratory and invasive carcinoma

PURPOSE

Although a variety of malignant tumors are susceptible to therapy with oncolytic herpes simplex viruses, the determinants of tumor sensitivity to these viruses are poorly understood. Nectin-1 is a cell surface adhesion molecule that is a component of intercellular adherens junctions and also functions as a herpes viral receptor. Because highly invasive cells may have decreased intercellular adhesion, we sought to determine if such cells might also have altered availability of cell surface nectin-1 to act as a herpes receptor.

EXPERIMENTAL DESIGN AND RESULTS

A series of squamous cell carcinoma lines of increasing migratory and invasive potential, termed MG1-MG14, were selected by serial passages of murine SCC7 through Matrigel invasion chambers. Available cell surface nectin-1 was enhanced on the MG11 and MG14 cell lines in comparison to SCC7 as measured by cellular ELISA and immunofluorescence microscopy. A replication-competent, oncolytic herpes virus (NV1023) showed an increased ability to enter MG11 and MG14 cells as compared with SCC7 cells. Furthermore, MG11 and MG14 supported increased herpes viral replication and cytotoxicity over SCC7. For all three of the cell lines, viral entry assays revealed that the actively migrating cells were significantly more susceptible to herpes infection than the nonmigrating cells.

CONCLUSIONS

These results show that malignant cells with highly migratory and invasive properties may exhibit increased cell surface nectin-1 availability, which may serve as a herpes viral receptor to enhance the efficacy of herpes oncolytic therapy. This finding has implications regarding patient selection for future clinical trials using these promising therapeutic vectors.

Herpes simplex virus based gene therapy enhances the efficacy of mitomycin C for the treatment of human bladder transitional cell carcinoma

PURPOSE

Oncolytic replication competent herpes simplex virus type-1 (HSV) mutants have the ability to replicate in and kill malignant cells. We have previously reported the ability of replication competent HSV to control bladder cancer growth in an orthotopic murine model. We hypothesized that the combination of a chemotherapeutic agent used for intravesical treatment, namely mitomycin C (MMC) (Bristol-Myers Squibb Oncology, Princeton, New Jersey), and oncolytic HSV would exert a synergistic effect for the treatment of human transitional cell carcinoma.

MATERIALS AND METHODS

We used mutant HSV NV1066 (Medigene, San Diego, California), which is deleted for viral genes ICP0 and ICP4, and selectively infects cancer cells, to treat the transitional cell carcinoma lines KU19-19 and SKUB. Cell survival was determined by lactate dehydrogenase assay for each agent as well as for drug-viral combinations from days 1 to 5. The isobologram method and the combination index method of Chou-Talalay were used to assess the synergistic effect.

RESULTS

NV1066 enhanced MMC mediated cytotoxicity at all combinations tested for KU19-19 and SKUB. The combination of the 2 agents demonstrated a synergistic effect and allowed dose reduction by 12 and 10.4 times (NV1066), and by 3 and 156 times (MMC) for the treatment of KU19-19 and SKUB, respectively, while achieving an estimated 90% cell kill.

CONCLUSIONS

These data provide the cellular basis for the clinical investigation of combined MMC and oncolytic HSV therapy for the treatment of bladder cancer.

Oncolytic herpes simplex virus mutants are more efficacious than wild-type adenovirus Type 5 for the treatment of high-risk neuroblastomas in preclinical models

BACKGROUND

High-risk neuroblastoma (Nb) is incurable using current treatment regimens in the majority of patients. Oncolytic virotherapy is a novel approach being tested for several types of adult cancers.

OBJECTIVES

To compare the susceptibility of Nb tumor models to oncolytic adenovirus and HSV mutants and delineate the mechanisms of resistance or sensitivity.

METHODS

Human Nb cell lines were used to determine susceptibility to adenovirus type 5 wild-type and HSV1 mutant (NV1066) infection, adenovirus receptor expression, support of NV1066 replication, and induction of apoptosis. Human xenograft tumors in immunodeficient mice were evaluated for histological effects and tumor response to intratumoral injection of an oncolytic HSV mutant.

RESULTS

All eight Nb cell lines tested in culture were relatively resistant to infection with wild type and attenuated adenoviruses. Cells expressed the cocksackie-adenovirus attachment receptor (CAR) but had low or absent expression of the internalization receptors (alphavbeta3, alphavbeta5 integrins). In contrast, all cells were uniformly sensitive to infection with the attenuated HSV mutant, NV1066. Productive virus replication and induction of apoptosis were observed in HSV-infected cells. CHLA-20 and LAN-5 xenograft tumors injected with a single dose of NV1066 showed a significant antitumor response, and the animals had a prolonged survival post infection in comparison to the PBS-treated control group. HSV injected tumors showed extensive areas of necrosis and morphologic evidence of apoptosis.

CONCLUSIONS

Nb tumor models are resistant to adenovirus mediated oncolysis but highly sensitive to HSV mediated oncolysis. Further studies of HSV virotherapy as a novel treatment for Nb are warranted.