Impairments in Bowel Function, Social Function and Quality of Life After Cytoreductive Surgery and Hyperthermic Intraperitoneal Chemotherapy.

BACKGROUND: Cytoreductive surgery and hyperthermic intraperitoneal chemotherapy (CRS-HIPEC) can be associated with decreases in quality of life (QOL). Bowel-related QOL (BR-QOL) after CRS-HIPEC has not been previously studied. The objectives of the current study were to examine the effect of different types of bowel resection during CRS-HIPEC on overall QOL and BR-QOL. METHODS: A prospective cohort study was performed. QOL data were collected using the European Organisation for Research and Treatment of Cancer (EORTC) QLQ-C30 and CR-29 questionnaires at 3, 6, and 12 months after CRS-HIPEC. Patients were divided into groups that underwent no bowel resection, non-low anterior resection (LAR) bowel resection, LAR, and LAR with stoma. Primary outcomes were global QOL and BR-QOL. RESULTS: Overall, 158 patients were included in this study. Bowel resections were performed in 77% of patients, with 31% undergoing LAR. Global QOL was not significantly different between groups. LAR patients (with and without stoma) had significantly worse BR-QOL, embarrassment, and altered body image, with LAR + stoma patients having the largest impairments in these domains. Trends toward higher levels of impotence and anxiety were also seen in LAR patients. Although global QOL improved over time, impairments in BR-QOL and sexual and social function did not significantly improve over time. CONCLUSIONS: Although global QOL after CRS-HIPEC was not affected by the type of bowel resection, the use of LAR and ostomies was associated with clinically meaningful and persistent impairments in BR-QOL and related functional domains. Generic QOL questionnaires may not adequately capture these domains; however, targeted questionnaires in these patients may help improve QOL after CRS-HIPEC.

Management of complex polyps of the colon and rectum.

PUPRPOSE: Benign polyps that are technically challenging and unsafe to remove via polypectomy are known as complex polyps. Concerns regarding safety and completeness of resection dictate they undergo advanced endoscopic techniques, such as endoscopic mucosal resection or surgery. We provide a comprehensive overview of complex polyps and current treatment options. METHODS: A review of the English literature was conducted to identifyarticles describing the management of complex polyps of the colon and rectum. RESULTS: Endoscopic mucosal resection is the standard of care for the majority of complex polyps. Only polyps that fail endoscopic mucosal resection or are highly suspicious of invasive cancer but which cannot be removed endoscopically warrant surgery. CONCLUSION: Several factors influence the treatment of a complex polyp; therefore, there cannot be a "one-size-fitsall" approach. Treatment should be tailored to the lesion's characteristics, the risk of adverse events, and the resources available to the treating physician.

Impact of Major Complications on Patients' Quality of Life After Cytoreductive Surgery and Hyperthermic Intraperitoneal Chemotherapy.

INTRODUCTION: Cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC) is an effective treatment for selected patients with peritoneal surface malignancies (PSM). Although it can have significant morbidity, perioperative mortality is low. Little is known about whether major complications after CRS/HIPEC have a lasting impact on patients' quality of life (QOL). METHODS: We retrospectively reviewed data from a prospectively collected database on patients treated with CRS/HIPEC for PSM (2011-2014). Patients with CRS/HIPEC and 6-month QOL evaluation were included. Major perioperative complications (Clavien-Dindo grade 3/4) were the primary independent variable. QOL was evaluated using the validated EORTC QLQ-C30 score. The primary outcome was 6-month global health score. Secondary outcomes were individual functional and symptom domains. RESULTS: Forty-two patients were analyzed. Median age was 57.5; 64 % were female. Origin of PSM was appendix (55 %), colorectal (38 %), mesothelioma (5 %), and small bowel (2 %). Fourteen patients (33 %) had major (grade 3/4) complications. Median length of stay was 16 days; patients experiencing major complications had significantly increased length of stay (35.5 vs. 13 days, p < 0.01). Major complications included intra-abdominal abscess (9.5 %), bleeding (9.5 %), symptomatic pleural effusion (7.1 %), anastomotic leaks (7.1 %), and renal failure (2.4 %). The average global health score at 6 months was 68.1. The worst-rated symptom scores at 6 months were diarrhea (39.8) and fatigue (35.4). There were no significant differences in 6-month QOL scores between patients with and without major complications, globally or in specific domains. CONCLUSIONS: Although major complications are common after CRS/HIPEC, QOL at 6 months recovers and is similar to those without major complications.

First-in-man study of western reserve strain oncolytic vaccinia virus: safety, systemic spread, and antitumor activity.

Oncolytic viral therapy utilizes a tumor-selective replicating virus which preferentially infects and destroys cancer cells and triggers antitumor immunity. The Western Reserve strain of vaccinia virus (VV) is the most virulent strain of VV in animal models and has been engineered for tumor selectivity through two targeted gene deletions (vvDD). We performed the first-in-human phase 1, intratumoral dose escalation clinical trial of vvDD in 16 patients with advanced solid tumors. In addition to safety, we evaluated signs of vvDD replication and spread to distant tumors, pharmacokinetics and pharmacodynamics, clinical and immune responses to vvDD. Dose escalation proceeded without dose-limiting toxicities to a maximum feasible dose of 3 × 10(9) pfu. vvDD replication in tumors was reproducible. vvDD genomes and/or infectious particles were recovered from injected (n = 5 patients) and noninjected (n = 2 patients) tumors. At the two highest doses, vvDD genomes were detected acutely in blood in all patients while delayed re-emergence of vvDD genomes in blood was detected in two patients. Fifteen of 16 patients exhibited late symptoms, consistent with ongoing vvDD replication. In summary, intratumoral injection of the oncolytic vaccinia vvDD was well-tolerated in patients and resulted in selective infection of injected and noninjected tumors and antitumor activity.

Complement inhibition prevents oncolytic vaccinia virus neutralization in immune humans and cynomolgus macaques.

Oncolytic viruses (OVs) have shown promising clinical activity when administered by direct intratumoral injection. However, natural barriers in the blood, including antibodies and complement, are likely to limit the ability to repeatedly administer OVs by the intravenous route. We demonstrate here that for a prototype of the clinical vaccinia virus based product Pexa-Vec, the neutralizing activity of antibodies elicited by smallpox vaccination, as well as the anamnestic response in hyperimmune virus treated cancer patients, is strictly dependent on the activation of complement. In immunized rats, complement depletion stabilized vaccinia virus in the blood and led to improved delivery to tumors. Complement depletion also enhanced tumor infection when virus was directly injected into tumors in immunized animals. The feasibility and safety of using a complement inhibitor, CP40, in combination with vaccinia virus was tested in cynomolgus macaques. CP40 pretreatment elicited an average 10-fold increase in infectious titer in the blood early after the infusion and prolonged the time during which infectious virus was detectable in the blood of animals with preexisting immunity. Capitalizing on the complement dependence of antivaccinia antibody with adjunct complement inhibitors may increase the infectious dose of oncolytic vaccinia virus delivered to tumors in virus in immune hosts.

Peritoneal Carcinomatosis from Colon Cancer: A Systematic Review of the Data for Cytoreduction and Intraperitoneal Chemotherapy.

A systematic review of the literature on the management of peritoneal carcinomatosis (PC) from colon cancer with cytoreductive surgery (CRS) and intraperitoneal chemotherapy (IPC) was undertaken using OVID Medline. Forty-six relevant studies were reviewed. Mean weighted overall morbidity following CRS and IPC was 49% (range 22-76%) and mortality was 3.6% (range 0-19%). Median overall survival ranged from 15 to 63 months, and 5-year overall survival ranged from 7 to 100%. This represents an improvement over historical treatment with systemic chemotherapy alone, even in the era of modern chemotherapeutic agents. Quality of life following surgery is initially decreased but improves with time and approaches baseline. Available data appear to support the treatment of PC from colon cancer with CRS and IPC. There is a large amount of variability among studies and few high-quality studies exist. Further studies are needed to standardize techniques.

Tumor vascularization is critical for oncolytic vaccinia virus treatment of peritoneal carcinomatosis.

Peritoneal carcinomatosis (PC) represents a significant clinical challenge for which there are few treatment options. Oncolytic viruses are ideal candidates for PC treatment because of their high tumor specificity, excellent safety profile and suitability for peritoneal delivery. Here, we described the use of vvDD-SR-RFP, a recombinant vaccinia virus, in xenograft and syngeneic models of colorectal PC. Colorectal cancer cell lines were highly susceptible to vvDD-SR-RFP replication and cytotoxicity. Intraperitoneal delivery of vvDD-SR-RFP on Day 12 to mice with colorectal carcinomatosis significantly improved survival whereas survival was not improved following virus treatment on Day 8, when tumors were smaller. Immunohistochemistry revealed early tumors had a poorly distributed network of blood vessels and lower proliferation index compared to later tumors. Virus infection was also restricted to tumor rims following Day 8 treatment, whereas it was disseminated in tumors treated on Day 12. Additionally, direct infection of tumor endothelium was observed and virus infection correlated with a loss of endothelial staining and induction of cell death. Our results demonstrate that tumor vasculature has a critical role in virus delivery and tumor response. This will have significant implications in the clinical setting, both in understanding timing of therapies and in designing combination treatment strategies.

Oncolytic vaccinia virus as an adjuvant treatment to cytoreductive surgery for malignant peritoneal mesothelioma.

BACKGROUND: Malignant peritoneal mesothelioma (MPM) is an aggressive cancer with a dismal prognosis. Oncolytic viruses are a promising new therapy for cancer because of their ability to kill tumor cells with minimal toxicity to normal tissues. This experimental study aimed to examine the potential of modified vaccinia virus (VV) to treat MPM when administered alone or as an adjuvant treatment to surgery. METHODS: Two aggressive murine mesothelioma cell lines (AC29, AB12), were used. Cell viability and viral cytopathic effects were assessed using MTS and crystal violet assays. Immunocompetent mice were injected intraperitoneally with MPM cells and treated with intraperitoneal VV. Tumor-bearing mice also underwent cytoreductive surgery (CRS) followed by VV (or control) therapy. RESULTS: The cytotoxic effects of VV on MPM cell lines was significantly increased compared with the control non-cancer cell line. In both orthotopic models, VV induced tumor regression, prolonging median and long-term survival. VV treatment after incomplete CRS was not superior to VV alone; however, when mice with microscopic disease were treated with VV, further prolongation of median and long-term survivals was observed. CONCLUSIONS: VV selectively kills MPM cells in vitro and leads to improved survival and cures in immunocompetent murine models. Higher efficacy of the virus in the microscopic disease context suggests the use of the virus as an adjuvant treatment to complete surgical resection. These promising results justify further studies of VV in humans as a novel treatment for MPM.

Mucinous tumor of the appendix with limited peritoneal spread: is there a role for expectant observation?

BACKGROUND: Cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC) is now the standard management for mucinous tumors of appendiceal origin at many centers. We examined the role of expectant observation (EO) in patients who had undergone an initial resection at the time of referral to our center and who had limited residual disease. METHODS: We performed a retrospective review of patients referred to Mount Sinai/Princess Margaret Hospitals, Toronto, for consideration of surgical management of peritoneal malignancy between January 1998 and December 2009. One hundred and three patients with primary mucinous appendiceal malignancy were identified. EO, consisting of regularly scheduled imaging and clinical review, was selected for asymptomatic patients with low-grade tumor and no/limited disease on imaging. Overall survival (OS) and progression-free survival (PFS) were determined. RESULTS: Management consisted of supportive care in 7 patients, systemic chemotherapy in 7, referral for CRS with HIPEC in 8, CRS without HIPEC at our center in 51, and EO in 30. In the CRS group, 5-year OS was 74 % and PFS was 56 %; both OS and PFS were predicted by extent of residual disease after cytoreduction (p = 0.014 and p = 0.011, respectively). In the EO group, 5-year OS and PFS were 95 and 82 %, respectively. Two patients in the EO group subsequently underwent CRS for progression on imaging. CONCLUSIONS: In well-selected patients who have undergone initial resection for low-grade mucinous tumor of the appendix with limited peritoneal spread, a formal program of observation can result in excellent 5-year OS and PFS. Longer-term follow-up will help define the benefits and risks of this approach.

Oncolytic Vaccinia virus safely and effectively treats skin tumors in mouse models of xeroderma pigmentosum.

Xeroderma pigmentosum (XP) is an orphan autosomal recessive disorder of DNA repair. When exposed to genotoxic stress, XP patients have reduced capacity to remove bulky adducts by nucleotide excision repair and are thus greatly predisposed to cancer. Unfortunately, given the nature of their underlying genetic defect, tumor-bearing XP patients cannot be treated with conventional DNA damaging therapies. Engineered strains of the poxvirus Vaccinia have been shown to cure cancer in numerous preclinical models, and based on promising Phase I/II clinical trials have recently been approved for late phase evaluation in humans. As poxviruses are nongenotoxic, we investigated whether clinical-candidate strains of Vaccinia can safely and effectively treat cancers arising from XP. In vitro, Vaccinia virus was highly cytotoxic against tumor-derived cells from XP patients, on average 10- to 100-fold more so than on nontumor derived control cells from similar patients. In vivo, local or systemic administration of Vaccinia virus led to durable tumor resolution in both xenograft and genetic models of XP. Importantly, Vaccinia virus was well tolerated in the genetic models, which are each null for a critical component of the DNA repair process. Taken together, our data suggest that oncolytic Vaccinia virus may be a safe and effective therapy for cancers arising from XP, and raise the possibility of similar therapeutic potential against tumors that arise in patients with other DNA repair disorders.

Physicians' awareness of cytoreductive surgery and hyperthermic intraperitoneal chemotherapy for colorectal cancer carcinomatosis.

BACKGROUND: Recent trials have shown that cytoreductive surgery and heated intraperitoneal chemotherapy (S+HIPEC) for colorectal cancer carcinomatosis (CRC-C) leads to 5-year, disease-free survival rates of more than 30%. Since these data represent a substantial change in the management of CRC-C, the objectives of this study were to determine physicians' awareness of S+HIPEC for CRC-C and physician characteristics predictive of awareness of S+HIPEC for CRC-C. METHODS: This study was a mailed, cross-sectional survey of general surgeons and medical oncologists in Ontario. RESULTS: The response rate was 44.0% (214 of 487). Most respondents were men and younger than 50 years. There was an even split between those at academic and community hospitals. Overall, 46% of respondents were aware of S+HIPEC for CRC-C, and multivariate analysis showed that there were no physician characteristics predictive of awareness of S+HIPEC for CRC-C. CONCLUSION: Physician awareness of S+HIPEC for CRC-C is low. Therefore, strategies to improve patient and physician knowledge about S+HIPEC for CRC-C are important to ensure appropriate treatment for patients.

CONTEXTE: Des essais récents ont démontré que la chirurgie de réduction tumorale combinée à la chimiothérapie intrapéritonéale hyperthermique (S+HIPEC) contre la carcinomatose du cancer colorectal (C-CCR) produit des taux de survie sans maladie de 5 ans qui dépassent 30 %. Comme ces données représentent une modification importante de la prise en charge de la C-CCR, l'étude visait à déterminer si les médecins connaissent la technique S+HIPEC contre la C-CCR et les caractéristiques des médecins qui prédisent une connaissance de la technique S+HIPEC contre la C-CCR. MÉTHODES: L'étude consistait en un sondage transversal postal mené auprès de chirurgiens généraux et de médecins oncologues de l'Ontario. RÉSULTANTS: Le taux de réponse a atteint 44,0 % (214 sur 487). La plupart des répondants étaient des hommes de moins de 50 ans. La répartition entre les hôpitaux universitaires et les hôpitaux communautaires était égale. Dans l'ensemble, 46 % des répondants connaissaient la technique S+HIPEC contre la C-CCR et une analyse à variables multiples a montré qu'il n'y avait pas de caractéristiques des médecins qui pouvaient prédire la connaissance de la technique S+HIPEC contre la C-CCR. CONCLUSIONS: Les médecins connaissent peu la technique S+HIPEC contre la C-CCR. Des stratégies visant à améliorer la connaissance de la technique S+HIPEC contre la C-CCR chez les patients et les médecins sont importantes pour assurer le traitement approprié des patients.

Vaccinia virus and peptide-receptor radiotherapy synergize to improve treatment of peritoneal carcinomatosis.

Tumor-specific overexpression of receptors enables a variety of targeted cancer therapies, exemplified by peptide-receptor radiotherapy (PRRT) for somatostatin receptor (SSTR)-positive neuroendocrine tumors. While effective, PRRT is restricted to tumors with SSTR overexpression. To overcome this limitation, we propose using oncolytic vaccinia virus (vvDD)-mediated receptor gene transfer to permit molecular imaging and PRRT in tumors without endogenous SSTR overexpression, a strategy termed radiovirotherapy. We hypothesized that vvDD-SSTR combined with a radiolabeled somatostatin analog could be deployed as radiovirotherapy in a colorectal cancer peritoneal carcinomatosis model, producing tumor-specific radiopeptide accumulation. Following vvDD-SSTR and 177Lu-DOTATOC treatment, viral replication and cytotoxicity, as well as biodistribution, tumor uptake, and survival, were evaluated. Radiovirotherapy did not alter virus replication or biodistribution, but synergistically improved vvDD-SSTR-induced cell killing in a receptor-dependent manner and significantly increased the tumor-specific accumulation and tumor-to-blood ratio of 177Lu-DOTATOC, making tumors imageable by microSPECT/CT and causing no significant toxicity. 177Lu-DOTATOC significantly improved survival over virus alone when combined with vvDD-SSTR but not control virus. We have therefore demonstrated that vvDD-SSTR can convert receptor-negative tumors into receptor-positive tumors and facilitate molecular imaging and PRRT using radiolabeled somatostatin analogs. Radiovirotherapy represents a promising treatment strategy with potential applications in a wide range of cancers.

Cutting both ways: the innate immune response to oncolytic virotherapy.

Oncolytic viruses (OVs), above and beyond infecting and lysing malignant cells, interact with the immune system in complex ways that have important therapeutic significance. While investigation into these interactions is still in its early stages, important insights have been made over the past two decades that will help improve the clinical efficacy of OV-based management strategies in cancer care moving forward. The inherent immunosuppression that defines the tumor microenvironment can be modified by OV infection, and the subsequent recruitment and activation of innate immune cells, in particular, is central to this. Indeed, neutrophils, macrophages, natural killer cells, and dendritic cells, as well as other populations such as myeloid-derived suppressor cells, are key to the immune escape that allows tumors to survive, but their natural response to infection can be exploited by virotherapy. While stimulation of innate immune cells by OVs can initiate antitumor responses, related antiviral activity can limit virus spread and direct cytopathogenic effects. In this review, we highlight how each innate immune cell population influences this balance of antitumor and antiviral forces during virotherapy, some of the important molecular pathways that have been identified, and specific therapeutic targets that have emerged through this work. We discuss the importance of OV-based combination therapies in optimizing antiviral and antitumor innate immune responses stimulated by virotherapy toward tumor eradication, and how these processes vary depending on the tumor and OV in question. Rather than concentrating on a particular OV species in the review, we present the range of effects that have been documented across OV types to emphasize the context-specific nature of these interactions and how this is important in the design of future OV-based treatment approaches.

Antiangiogenic arming of an oncolytic vaccinia virus enhances antitumor efficacy in renal cell cancer models.

Oncolytic vaccinia viruses have shown compelling results in preclinical cancer models and promising preliminary safety and antitumor activity in early clinical trials. However, to facilitate systemic application it would be useful to improve tumor targeting and antitumor efficacy further. Here we report the generation of vvdd-VEGFR-1-Ig, a targeted and armed oncolytic vaccinia virus. Tumor targeting was achieved by deletion of genes for thymidine kinase and vaccinia virus growth factor, which are necessary for replication in normal but not in cancer cells. Given the high vascularization typical of kidney cancers, we armed the virus with the soluble vascular endothelial growth factor (VEGF) receptor 1 protein for an antiangiogenic effect. Systemic application of high doses of vvdd-VEGFR-1-Ig resulted in cytokine induction in an immunocompromised mouse model. Upon histopathological analysis, splenic extramedullary hematopoiesis was seen in all virus-injected mice and was more pronounced in the vvdd-VEGFR-1-Ig group. Analysis of the innate immune response after intravenous virus injection revealed high transient and dose-dependent cytokine elevations. When medium and low doses were used for intratumoral or intravenous injection, vvdd-VEGFR-1-Ig exhibited a stronger antitumor effect than the unarmed control. Furthermore, expression of VEGFR-1-Ig was confirmed, and a concurrent antiangiogenic effect was seen. In an immunocompetent model, systemic vvdd-VEGFR-1-Ig exhibited superior antitumor efficacy compared to the unarmed control virus. In conclusion, the targeted and armed vvdd-VEGFR-1-Ig has promising anticancer activity in renal cell cancer models. Extramedullary hematopoiesis may be a sensitive indicator of vaccinia virus effects in mice.

Intelligent design: combination therapy with oncolytic viruses.

Metastatic cancer remains an incurable disease in the majority of cases and thus novel treatment strategies such as oncolytic virotherapy are rapidly advancing toward clinical use. In order to be successful, it is likely that some type of combination therapy will be necessary to have a meaningful impact on this disease. Although it may be tempting to simply combine an oncolytic virus with the existing standard radiation or chemotherapeutics, the long-term goal of such treatments must be to have a rational, potentially synergistic combination strategy that can be safely and easily used in the clinical setting. The combination of oncolytic virotherapy with existing radiotherapy and chemotherapy modalities is reviewed along with novel biologic therapies including immunotherapies, in order to help investigators make intelligent decisions during the clinical development of these products.

Identification of genetically modified Maraba virus as an oncolytic rhabdovirus.

To expand our current array of safe and potent oncolytic viruses, we screened a variety of wild-type (WT) rhabdoviruses against a panel of tumor cell lines. Our screen identified a number of viruses with varying degrees of killing activity. Maraba virus was the most potent of these strains. We built a recombinant system for the Maraba virus platform, engineered a series of attenuating mutations to expand its therapeutic index, and tested their potency in vitro and in vivo. A double mutant (MG1) strain containing both G protein (Q242R) and M protein (L123W) mutations attenuated Maraba virus in normal diploid cell lines, yet appeared to be hypervirulent in cancer cells. This selective attenuation was mediated through interferon (IFN)-dependent and -independent mechanisms. Finally, the Maraba MG1 strain had a 100-fold greater maximum tolerable dose (MTD) than WT Maraba in vivo and resulted in durable cures when systemically administered in syngeneic and xenograft models. In summary, we report a potent new oncolytic rhabdovirus platform with unique tumor-selective attenuating mutations.

Synergistic interaction between oncolytic viruses augments tumor killing.

A major barrier to all oncolytic viruses (OVs) in clinical development is cellular innate immunity, which is variably active in a spectrum of human malignancies. To overcome the heterogeneity of tumor response, we combined complementary OVs that attack cancers in distinct ways to improve therapeutic outcome. Two genetically distinct viruses, vesicular stomatitis virus (VSV) and vaccinia virus (VV), were used to eliminate the risk of recombination. The combination was tested in a variety of tumor types in vitro, in immunodeficient and immunocompetent mouse tumor models, and ex vivo, in a panel of primary human cancer samples. We found that VV synergistically enhanced VSV antitumor activity, dependent in large part on the activity of the VV B18R gene product. A recombinant version of VSV expressing the fusion-associated small-transmembrane (p14FAST) protein also further enhanced the ability of VV to spread through an infected monolayer, resulting in a "ping pong" oncolytic effect wherein each virus enhanced the ability of the other to replicate and/or spread in tumor cells. Our strategy is the first example where OVs are rationally combined to utilize attributes of different OVs to overcome the heterogeneity of malignancies and demonstrates the feasibility of combining complementary OVs to improve therapeutic outcome.

Deletion of immunomodulatory genes as a novel approach to oncolytic vaccinia virus development.

Vaccinia virus (VV) has emerged as a promising platform for oncolytic virotherapy. Many clinical VV candidates, such as the double-deleted VV, vvDD, are engineered with deletions that enhance viral tumor selectivity based on cellular proliferation rates. An alternative approach is to exploit the dampened interferon-based innate immune responses of tumor cells by deleting one of the many VV immunomodulatory genes expressed to dismantle the antiviral response. We hypothesized that such a VV mutant would be attenuated in non-tumor cells but retain the ability to effectively propagate in and kill tumor cells, yielding a tumor-selective oncolytic VV with significant anti-tumor potency. In this study, we demonstrated that VVs with a deletion in one of several VV immunomodulatory genes (N1L, K1L, K3L, A46R, or A52R) have similar or improved in vitro replication, spread, and cytotoxicity in colon and ovarian cancer cells compared to vvDD. These deletion mutants are tumor selective, and the best performing candidates (ΔK1L, ΔA46R, and ΔA52R VV) are associated with significant improvement in survival, as well as immunomodulation, within the tumor environment. Overall, we show that exploiting the diminished antiviral responses in tumors serves as an effective strategy for generating tumor-selective and potent oncolytic VVs, with important implications in future oncolytic virus (OV) design.

Modeling oncolytic virus dynamics in the tumor microenvironment using zebrafish.

We have adapted a zebrafish (Danio rerio) tumor xenograft model for use in the study of oncolytic virotherapy. Following implantation of mammalian cancer cells into the perivitelline space of developing zebrafish embryos, both local and intravenous oncolytic virus treatments produce a tumor-specific infection with measurable antitumor effects. Tumor cells are injected at 48 h post fertilization, with oncolytic virus treatment then being administered 24 h later to allow for an initial period of tumor development and angiogenesis. Confocal fluorescent imaging is used to quantify dynamics within the tumor environment. The natural translucency of zebrafish at the embryo stage, coupled with the availability of strains with fluorescent immune and endothelial cell reporter lines, gives the model broad potential to allow for real time, in vivo investigation of important events within tumors throughout the course of virotherapy. Zebrafish xenografts offer a system with biologic fidelity to processes in human cancer development that influence oncolytic virus efficacy, and to our knowledge this is the first demonstration of the model's use in the context of virotherapy. Compared with other models, our protocol offers a powerful, inexpensive approach to evaluating novel oncolytic viruses and oncolytic virus-based combination therapies, with potential application to investigating the impacts of virotherapy on immune response, tumor vasculature, and metastatic disease.

Efficacy of systemically administered oncolytic vaccinia virotherapy for malignant gliomas is enhanced by combination therapy with rapamycin or cyclophosphamide.

PURPOSE: The oncolytic effects of a systemically delivered, replicating, double-deleted vaccinia virus has been previously shown for the treatment of many cancers, including colon, ovarian, and others. The purpose of this study was to investigate the oncolytic potential of double-deleted vaccinia virus alone or in combination with rapamycin or cyclophosphamide to treat malignant gliomas in vitro and in vivo. EXPERIMENTAL DESIGN: Rat (RG2, F98, C6) and human (A172, U87MG, U118) glioma cell lines were cultured in vitro and treated with live or UV-inactivated vaccinia virus. Viral gene [enhanced green fluorescent protein (EGFP)] expression by fluorescence-activated cell sorting, relative cell viability by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), and assays for cytopathic effects were examined. S.c. murine tumor xenografts (U87MG, U118, C6) and i.c. (RG2, F98) tumor models in immunocompetent rats were treated with systemic administration of EGFP-expressing vaccinia virus (vvDD-EGFP), alone or in combination with rapamycin or cyclophosphamide, or controls. Tumor size, viral biodistribution, and animal survival were assessed. Lastly, the oncolytic effects of vvDD-EGFP on human malignant glioma explants were evaluated. RESULTS: vvDD-EGFP was able to infect and kill glioma cells in vitro. A single systemic dose of vvDD-EGFP significantly inhibited the growth of xenografts in athymic mice. Systemic delivery of vvDD-EGFP alone was able to target solitary and multifocal i.c. tumors and prolong survival of immunocompetent rats, whereas combination therapy with rapamycin or cyclophosphamide enhanced viral replication and further prolonged survival. Finally, vvDD-EGFP was able to infect and kill ex vivo primary human malignant gliomas. CONCLUSIONS: These results suggest that vvDD-EGFP is a promising novel agent for human malignant glioma therapy, and in combination with immunosuppressive agents, may lead to prolonged survival from this disease.