Treatment of multi-focal colorectal carcinoma metastatic to the liver of immune-competent and syngeneic rats by hepatic artery infusion of oncolytic vesicular stomatitis virus

Viral Replicon Systems and Their Biosafety Aspects

Introduction

Viral RNA replicons are self-amplifying RNA molecules generated by deleting genetic information of one or multiple structural proteins of wild-type viruses. Remaining viral RNA is used as such (naked replicon) or packaged into a viral replicon particle (VRP), whereby missing genes or proteins are supplied via production cells. Since replicons mostly originate from pathogenic wild-type viruses, careful risk consideration is crucial.

Methods

A literature review was performed compiling information on potential biosafety risks of replicons originating from positive- and negative-sense single-stranded RNA viruses (except retroviruses).

Results

For naked replicons, risk considerations included genome integration, persistence in host cells, generation of virus-like vesicles, and off-target effects. For VRP, the main risk consideration was formation of primary replication competent virus (RCV) as a result of recombination or complementation. To limit the risks, mostly measures aiming at reducing the likelihood of RCV formation have been described. Also, modifying viral proteins in such a way that they do not exhibit hazardous characteristics in the unlikely event of RCV formation has been reported.

Discussion and Conclusion

Despite multiple approaches developed to reduce the likelihood of RCV formation, scientific uncertainty remains on the actual contribution of the measures and on limitations to test their effectiveness. In contrast, even though effectiveness of each individual measure is unclear, using multiple measures on different aspects of the system may create a solid barrier. Risk considerations identified in the current study can also be used to support risk group assignment of replicon constructs based on a purely synthetic design.

Evaluation of the blood supply and efficacy of transcatheter arterial chemoembolization for patients with liver metastasis using 18F-fluorodeoxyglucose positron emission tomography/computed tomography

Our study aims to evaluate the efficacy of transcatheter arterial chemoembolization in the treatment of patients with liver metastasis using integrated ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography. A total of 97 liver metastasis patients treated by transcatheter arterial chemoembolization were enrolled in this study. The ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography images of liver metastasis patients were collected before and after transcatheter arterial chemoembolization treatment. The efficacy of transcatheter arterial chemoembolization for the treatment of liver metastasis was evaluated according to the revised Response Evaluation Criteria in Solid Tumors guidelines. The receiver operating characteristic curve analysis was used to determine cut-off values of ¹⁸F-fluorodeoxyglucose positron emission tomography parameters (Tsuvmax, Tsuvmax/Lsuvmax, and Tsuvmax/Lsuvmean) for predicting the efficacy of transcatheter arterial chemoembolization. Progression-free survival and the incidence of postoperative complications were compared. Correlation of Tsuvmax, Tsuvmax/Lsuvmax, and Tsuvmax/Lsuvmean with blood supply and lipiodol deposition in the lesion was analyzed. Among three ¹⁸F-fluorodeoxyglucose positron emission tomography parameters, the receiver operating characteristic analysis showed that Tsuvmax/Lsuvmax with a cut-off value of 3.56 was the best predictor of transcatheter arterial chemoembolization efficacy. According to the cut-off value of Tsuvmax/Lsuvmax, liver metastasis patients were divided into the Tsuvmax/Lsuvmax ≤ 3.56 and Tsuvmax/Lsuvmax > 3.56 groups. Compared with the Tsuvmax/Lsuvmax > 3.56 group, the Tsuvmax/Lsuvmax ≤ 3.56 group showed a longer progression-free survival and a lower incidence of postoperative complications. The Tsuvmax, Tsuvmax/Lsuvmax, and Tsuvmax/Lsuvmean in the lesion with abundant blood supply were significantly lower than those in peripheral liver parenchyma, while the Tsuvmax, Tsuvmax/Lsuvmax, and Tsuvmax/Lsuvmean in the lesion with lack of blood supply were significantly higher than those in peripheral liver parenchyma. Spearman correlation analysis indicated that lipiodol deposition in the lesion was positively correlated with the Tsuvmax, Tsuvmax/Lsuvmax, and Tsuvmax/Lsuvmean. The Tsuvmax/Lsuvmax of ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography may be a good tool for predicting the blood supply and efficacy of transcatheter arterial chemoembolization for patients with liver metastasis.

p53 gene therapy-based transarterial chemoembolization for unresectable hepatocellular carcinoma: A prospective cohort study

BACKGROUND AND AIM

Transarterial chemoembolization (TACE) is used for treating unresectable hepatocellular carcinoma (HCC), but its efficacy still needs to be improved. Recombinant adenovirus p53 (rAd-p53) injection is a gene therapeutic agent that could improve the prognosis of HCC patients. This study aimed to evaluate the efficacy and safety of rAd-p53-based TACE for treating unresectable HCC.

METHODS

Prospective analysis of patients who received rAd-p53-based TACE or TACE alone in Chongqing Cancer Institute from January 1, 2011 to December 31, 2012. The primary endpoint is overall survival. The secondary endpoints were progression-free survival, response rate, and safety.

RESULTS

One hundred two patients were enrolled in this study. Forty-nine patients received the rAd-p53-based TACE, and 53 patients received TACE alone. The rAd-p53-based TACE treatment strategy improved the overall survival (hazard ratio: 0.58, 95% confidence interval: 0.35-0.96, P = 0.035), progression-free survival (hazard ratio: 0.60, 95% confidence interval: 0.37-0.97, P = 0.037), response rate (P = 0.047) compared with TACE monotherapy. The rAd-p53-based TACE treatment group caused more occurrences of fever than with TACE alone (P = 0.01). However, symptomatic treatment may solve this problem.

CONCLUSIONS

rAd-p53-based TACE treatment strategy is effective and safe for treating unresectable HCC. Large-scale randomized clinical trials are needed to verify these results.

Characteristics of oncolytic vesicular stomatitis virus displaying tumor-targeting ligands

We sought proof of principle that tumor-targeting ligands can be displayed on the surface of vesicular stomatitis virus (VSV) by engineering its glycoprotein. Here, we successfully rescued VSVs displaying tumor vasculature-targeting ligands. By using a rational approach, we investigated various feasible insertion sites on the G protein of VSV (VSV-G) for display of tumor vasculature-targeting ligands, cyclic RGD (cRGD) and echistatin. We found seven sites on VSV-G that tolerated insertion of the 9-residue cRGD peptide, two of which could tolerate insertion of the 49-amino acid echistatin domain. All of the ligand-displaying viruses replicated as well as the parental virus. In vitro studies demonstrated that the VSV-echistatin viruses specifically bound to targeted integrins. Since the low-density lipoprotein receptor (LDLR) was recently identified as a major receptor for VSV, we investigated the entry of ligand-displaying viruses after masking LDLR. The experiment showed that the modified viruses can enter the cell independently of LDLR, whereas entry of unmodified virus is significantly blocked by a specific monoclonal antibody against LDLR. Both parental and ligand-displaying viruses displayed equal oncolytic efficacies in a syngeneic mouse myeloma model. We further demonstrated that single-chain antibody fragments against tumor-specific antigens can be inserted at the N terminus of the G protein and that corresponding replication-competent VSVs can be rescued efficiently. Overall, we demonstrated that functional tumor-targeting ligands can be displayed on replication-competent VSVs without perturbing viral growth and oncolytic efficacy. This study provides a rational foundation for the future development of fully retargeted oncolytic VSVs.

Oncolytic vesicular stomatitis virus as a treatment for neuroendocrine tumors

BACKGROUND

Therapeutic goals for neuroendocrine tumors (NETs) not amenable to operative cure are limited to relieving symptoms and slowing progression. Many malignancies acquire defective antiviral responses as they undergo unregulated proliferation. Therefore, we explored the abilities of recombinant wild-type vesicular stomatitis virus and an attenuated matrix protein mutant (M51R-VSV) to exploit defective antiviral pathways in NETs.

METHODS

Viral infectivity and lethality were evaluated in a panel of human NET cell lines H727, UMC-11, and CNDT2.5. We evaluated β-interferon pathways in these cells to define the acquired defect. Murine xenografts were treated with a single intratumoral injection of M51R-VSV to study viral efficacy in vivo.

RESULTS

VSV infected >99% of cells within 24 hours and killed >95% within 72 hours. NET cells did not produce relevant amounts of β-interferon after infection, but exogenous β-interferon protected cells from oncolysis. Treatment with M51R-VSV resulted in suppressed tumor growth (mean value ± standard error of the mean) compared with mock-infected xenografts for H727 (87 ± 72% vs. 2,197 ± 335%; P < .001), UMC-11 (13 ± 59% vs. 1,471 ± 324%; P < .001), and CNDT2.5 (81 ± 121% vs. 1,576 ± 349%; P = .001).

CONCLUSION

VSV infects and kills human NETs by exploiting their inability to produce a type I antiviral response. Therefore, M51R-VSV is an excellent candidate for the treatment of advanced NETs.

Mouse models of colorectal cancer

Colorectal cancer is one of the most common malignancies in the world. Many mouse models have been developed to evaluate features of colorectal cancer in humans. These can be grouped into genetically-engineered, chemically-induced, and inoculated models. However, none recapitulates all of the characteristics of human colorectal cancer. It is critical to use a specific mouse model to address a particular research question. Here, we review commonly used mouse models for human colorectal cancer.

Neuroattenuation of vesicular stomatitis virus through picornaviral internal ribosome entry sites

Vesicular stomatitis virus (VSV) is potent and a highly promising agent for the treatment of cancer. However, translation of VSV oncolytic virotherapy into the clinic is being hindered by its inherent neurotoxicity. It has been demonstrated that selected picornaviral internal ribosome entry site (IRES) elements possess restricted activity in neuronal tissues. We therefore sought to determine whether the picornavirus IRES could be engineered into VSV to attenuate its neuropathogenicity. We have used IRES elements from human rhinovirus type 2 (HRV2) and foot-and-mouth disease virus (FMDV) to control the translation of the matrix gene (M), which plays a major role in VSV virulence. In vitro studies revealed slowed growth kinetics of IRES-controlled VSVs in most of the cell lines tested. However, in vivo studies explicitly demonstrated that IRES elements of HRV2 and FMDV severely attenuated the neurovirulence of VSV without perturbing its oncolytic potency.

Vesicular stomatitis virus as an oncolytic agent against pancreatic ductal adenocarcinoma

Vesicular stomatitis virus (VSV) is a promising oncolytic agent against a variety of cancers. However, it has never been tested in any pancreatic cancer model. Pancreatic ductal adenocarcinoma (PDA) is the most common and aggressive form of pancreatic cancer. In this study, the oncolytic potentials of several VSV variants were analyzed in a panel of 13 clinically relevant human PDA cell lines and compared to conditionally replicative adenoviruses (CRAds), Sendai virus and respiratory syncytial virus. VSV variants showed oncolytic abilities superior to those of other viruses, and some cell lines that exhibited resistance to other viruses were successfully killed by VSV. However, PDA cells were highly heterogeneous in their susceptibility to virus-induced oncolysis, and several cell lines were resistant to all tested viruses. Resistant cells showed low levels of very early VSV RNA synthesis, indicating possible defects at initial stages of infection. In addition, unlike permissive PDA cell lines, most of the resistant cell lines were able to both produce and respond to interferon, suggesting that intact type I interferon responses contributed to their resistance phenotype. Four cell lines that varied in their permissiveness to VSV-ΔM51 and CRAd dl1520 were tested in mice, and the in vivo results closely mimicked those in vitro. While our results demonstrate that VSV is a promising oncolytic agent against PDA, further studies are needed to better understand the molecular mechanisms of resistance of some PDAs to oncolytic virotherapy.

Oncolytic vesicular stomatitis virus administered by isolated limb perfusion suppresses osteosarcoma growth

A significant limitation to oncolytic virotherapy in vivo is the lack of a clinically relevant means of delivering the virus. We evaluated the oncolytic activity of vesicular stomatitis virus (VSV) in human osteosarcoma cells and explored isolated limb perfusion (ILP) as a novel oncolytic virus delivery system to extremity sarcoma in immune-competent rats. Human and rat osteosarcoma cells transduced with rVSV-lacZ uniformly expressed β-gal. VSV was fully capable of replicating its RNA genome in all osteosarcoma cell lines, and efficiently killed them in time- and dose-dependent manners, whereas normal bone marrow stromal cells were refractory to the virus. VSV delivered by ILP inhibited growth of osteosarcoma xenografts more potently than that injected intravenously and intratumorally in the hind limb of immune-competent rats. Histopathological sections of tumor lesions treated by ILP-delivered VSV showed positive for VSV-G protein. There were no VSV-G expressions in perfused leg muscle, nonperfused leg muscle, brain, lung, and liver in VSV-treated rats. Our findings show efficient VSV gene expression and replication in osteosarcoma cells, suggesting that osteosarcoma may be a promising target for oncolytic virotherapy with VSV. Furthermore, we firstly showed that ILP of VSV against extremity sarcoma caused antitumor activity.

Mechanisms underlying vesicular stomatitis virus-induced apoptosis of HepG2 cells in vitro

AIM: To investigate the apoptosis-inducing effect of a laboratory-attenuated vesicular stomatitis virus (VSV) strain on HepG2 cells and to explore the underlying mechanisms.

METHODS: After HepG2 cells were infected with VSV at a multiplicity of infection (MOI) of 1.0, cell viability was determined by MTT assay; morphological assessment of apoptosis was performed by acridine orange (AO)/ethidium bromide (EB) and Hoechst/PI staining; apoptotic cells were quantified by annexin V/PI double-staining and cell cycle analysis; mitochondrial membrane potential (ΔΨm) was measured by JC-1 staining; and activation of caspase proteolytic cascade was measured with caspase-9, caspase-8 and -3 colorimetric assay kits.

RESULTS: The attenuated VSV strain could markedly inhibit HepG2 cell proliferation in a time-dependent manner. After HepG2 cells were exposed to VSV at an MOI of 1.0 for 24 h, the percentages of early apoptotic cells (26.46% ± 6.01% vs 4.86% ± 2. 28%, t = -5.817, P < 0.01) and cells in sub-G1 phase (14.07% ± 3.83% vs 3.99% ± 1.36%, t = -4.293, P < 0.05) were increased compared with mock-infected cells. VSV infection significantly decreased mitochondria membrane potential (ΔΨm) (t = -4.586, P < 0.05) and increased the activity of caspase-9 and caspase-3 (both P < 0.05).

CONCLUSION: Human hepatoma cell line HepG2 is highly susceptible to infection with oncolytic VSV. VSV can inhibit the proliferation of HepG2 cell and promote apoptosis through the intrinsic mitochondria pathway. VSV-induced collapse of the mitochondrial trans-membrane potential could exert a feedback effect to elicit caspase-9, and then lead to the activation of the key downstream factor caspase-3.

Vesicular stomatitis virus-induced immune suppressor cells generate antagonism between intratumoral oncolytic virus and cyclophosphamide

Despite having potent oncolytic activity, in vitro, direct intratumoral injection of oncolytic vesicular stomatitis virus (VSV) into established AE17ova mesothelioma tumors in C57Bl/6 mice had no therapeutic effect. During studies to combine systemic cyclophosphamide (CPA) with VSV to suppress the innate immune reaction against VSV, we observed that CPA alone had highly significant antitumor effects in this model. However, against our expectations, the combination of CPA and VSV consistently reduced therapeutic efficacy compared to CPA alone, despite the fact that the combination increased intratumoral VSV titers. We show here that CPA-mediated therapy against AE17ova tumors was immune-mediated and dependent upon both CD4 T cells and natural killer (NK) cells. However, intratumoral VSV induced a transforming growth factor-β (TGF-β)-dependent suppressive activity, mediated by CD11b(+)GR-1(+) cells that significantly inhibited both antigen-specific T-cell activation, and CPA-activated, NK-dependent killing of AE17ova tumor cells. Overall, our results show that treatment with oncolytic viruses can induce a variety of immune-mediated consequences in vivo with both positive, or negative, effects on antitumor therapy. These underexplored immune consequences of treatment with oncolytic viruses may have significant, and possibly unexpected, impacts on how virotherapy interacts in combination with other agents which modulate antitumor immune effectors.

VSV oncolytic virotherapy in the B16 model depends upon intact MyD88 signaling

We show here, for the first time to our knowledge, that the antitumor therapy of oncolytic vesicular stomatitis virus (VSV) in the B16ova model depends upon signaling through myeloid differentiation primary response gene 88 (MyD88) in host cells. VSV-mediated therapy of B16ova tumors was abolished in MyD88(-/-) mice despite generation of antigen-specific T cell responses similar to those in immune-competent mice. Mice defective in only toll-like receptor 4 (TLR4), TLR7, or interleukin 1 (IL-1) signaling retained VSV-induced therapy, suggesting that multiple, redundant pathways of innate immune activation by the virus contribute to antitumor immune reactivity. Lack of MyD88 signaling was associated with decreased expression of proinflammatory cytokines and neutrophil infiltration in response to intratumoral virus, as well as decreased infiltration of draining lymph nodes (LN) with plasmacytoid dendritic cells (pDCs) (CD11b(-)GR1(+)B220(+)) and myeloid-derived suppressor cells (CD11b(+)GR1(+)F4/80(+)). MyD88 signaling in response to VSV was also closely associated with a type I interferon (IFN) response. This inhibited virus replication within the tumor but also protected the host from viral dissemination from the tumor. Therefore, the innate immune response to oncolytic viruses can be, simultaneously, protherapeutic, antioncolytic, and systemically protective. These paradoxically conflicting roles need to be carefully considered in future strategies designed to improve the efficacy of oncolytic virotherapy.

Vesicular stomatitis virus modified with single chain IL-23 exhibits oncolytic activity against tumor cells in vitro and in vivo

Viruses are potentially attractive agents for development as novel oncolytic agents. Reverse genetic approaches allow for the attenuation of candidate viruses and can enhance their ability to exploit inherent cellular and molecular properties of tumors, including deficiencies in interferon (IFN) signaling. Vesicular stomatitis virus (VSV) is a promising oncolytic agent for exactly these reasons. VSV infection of immunocompetent mice is usually rapidly cleared due to the virus' sensitivity to type I IFN responses. However, in tumors that are unable to activate the IFN response, VSV is able to replicate without inhibition, resulting in cell destruction. Unfortunately, when VSV is introduced into mice intranasally or systemically via therapeutic doses into tumor-bearing rodents, hosts may develop fatal encephalitis. We have previously found that a recombinant VSV expressing the pro-inflammatory cytokine interleukin-23 (IL-23) is significantly attenuated in the central nervous system (CNS). As a result of this, we hypothesized that attenuation in the CNS is partially a result of enhanced NO response as a result of IL-23 signaling. Infection of the CNS with this virus (designated VSV23) is characterized by decreased viral replication, morbidity, and mortality. We have now extended those studies which reveal that VSV23 maintains oncolytic capacity in vitro in multiple cell lines including NB41A3 neuroblastomas, L929 adipose-derived cells, immortalized BHK-21 cells, and the murine mammary derived JC cells. Additionally, in vivo VSV23 infection results in JC tumor destruction and induces enhanced memory responses against tumor cells.

Cytokine-modified VSV is attenuated for neural pathology, but is both highly immunogenic and oncolytic

Vesicular stomatitis virus (VSV), an enveloped, nonsegmented, negative-stranded RNA virus, is being tested by several laboratories as an antitumor agent. Unfortunately, viral infection of the central nervous system (CNS) has been observed by many groups following administration to tumor-bearing animals. In rodents, VSV encephalitis is characterized by weight-loss, paralysis, and high mortality. In order to provide protection from VSV infection of the CNS after therapeutic administration, we have attenuated VSV by the introduction of the gene encoding the proinflammatory cytokine interleukin (IL)-23, and designated the new virus VSV23. We hypothesize that while VSV23 is replicating within tumors, resulting in tumor destruction, the expression of IL-23 will enhance host antitumor and antiviral immune responses. In the event that the virus escapes from the tumor, the host's immune system will be activated and the virus will be rapidly cleared from healthy tissue. Experimental VSV23 infection of the CNS is characterized by decreased viral replication, morbidity, and mortality. VSV23 is capable of stimulating the enhanced production of nitric oxide in the CNS, which is critical for elimination of VSV from infected neurons. Intraperitoneal administration of VSV23 stimulates both nonspecific natural killer cell, virus-specific cytolytic T lymphocyte and memory virus-specific proliferative T cell responses against wild-type VSV in splenocytes. Furthermore, VSV23 is able to replicate in, and induce apoptosis of tumor cells in vitro. These data indicate that VSV23 is immunogenic, attenuated and suitable for testing as an efficacious and safe oncolytic agent.

Oncolytic efficacy of recombinant vesicular stomatitis virus and myxoma virus in experimental models of rhabdoid tumors

PURPOSE

Rhabdoid tumors are highly aggressive pediatric tumors that are usually refractory to available treatments. The purpose of this study was to evaluate the therapeutic potential of two oncolytic viruses, myxoma virus (MV) and an attenuated vesicular stomatitis virus (VSV(DeltaM51)), in experimental models of human rhabdoid tumor.

EXPERIMENTAL DESIGN

Four human rhabdoid tumor cell lines were cultured in vitro and treated with live or inactivated control virus. Cytopathic effect, viral gene expression, infectious viral titers, and cell viability were examined at various time points after infection. To study viral oncolysis in vivo, human rhabdoid tumor cells were implanted s.c. in the hind flank or intracranially in CD-1 nude mice and treated with intratumoral (i.t.) or i.v. injections of live or UV-inactivated virus. Viral distribution and effects on tumor size and survival were assessed.

RESULTS

All rhabdoid tumor cell lines tested in vitro were susceptible to productive lethal infections by MV and VSV(DeltaM51). I.t. injection of live MV or VSV(DeltaM51) dramatically reduced the size of s.c. rhabdoid tumor xenografts compared with control animals. I.v. administration of VSV(DeltaM51) or i.t. injection of MV prolonged the median survival of mice with brain xenografts compared with controls (VSV(DeltaM51): 25 days versus 21 days, log-rank test, P = 0.0036; MV: median survival not reached versus 21 days, log-rank test, P = 0.0007). Most of the MV-treated animals (4 of 6; 66.7%) were alive and apparently "cured" when the experiment was arbitrarily ended (>180 days).

CONCLUSIONS

These results suggest that VSV(DeltaM51) and MV could be novel effective therapies against human rhabdoid tumor.

Animal models for liver metastases of colorectal cancer: research review of preclinical studies in rodents

Liver metastases of colorectal carcinoma occur in about 50-60% of patients. To improve survival of these patients, there is an urgent need for new treatment strategies. For this purpose, the availability of a preclinical model to develop and test such treatments is mandatory. An ideal animal model for studying liver metastases of colorectal origin should mimic all aspects of the metastatic development in humans and be practical, predictable, and optimal in terms of ethical considerations. Thus far, no model has been developed which satisfies all these conditions. As a consequence, choosing an animal model for the study of liver metastases requires compromises and choices about the necessary characteristics that depend on the purpose of the intended experiments. This overview addresses the advantages and disadvantages of different animal models used for research on experimental liver metastases of colorectal origin. Based on data available in literature, we conclude that heterotopic injection of undifferentiated syngeneic tumor cells in immunocompetent rodents covers most of the desired characteristics. Both subcapsular as well as intraportal injection will yield suitable models and the eventual choice will depend on the aim of the study.

Therapeutic efficacy of replication-competent retrovirus vector-mediated suicide gene therapy in a multifocal colorectal cancer metastasis model

Replication-competent retrovirus (RCR) vectors are intrinsically incapable of infecting quiescent cells and have been shown to achieve highly efficient and tumor-restricted replicative spread and gene transfer in vivo after direct intratumoral injection in a variety of primary cancer models. However, i.v. delivery of RCR vectors expressing therapeutic genes has never previously been tested, particularly in an immunocompetent tumor model. Therefore, in the present study, we sought to test the therapeutic effect of an RCR vector (ACE-CD) carrying the yeast cytosine deaminase (CD) gene, which converts the nontoxic prodrug 5-fluorocytosine (5FC) into the chemotoxin 5-fluorouracil, after delivery by infusion into the locoregional circulation in a multifocal hepatic metastasis model of colon cancer. After confirmation of suicide gene cytotoxicity in vitro, multifocal hepatic tumors were established in syngeneic mice with murine CT26 colorectal cancer cells expressing firefly luciferase (CT26-Luc), and the ACE-CD vector was infused via intrasplenic injection into the portal circulation. Fourteen days after locoregional infusion, systemic administration of 5FC resulted in significant inhibition of bioluminescent signals in mice whose tumors had been infected with RCR but not in control mice. Notably, there was no detectable RCR vector spread to normal liver or bone marrow by quantitative PCR analysis. Our results thus show that locoregional delivery of a suicide gene by RCR vectors infused into the portal circulation results in progressive transduction of multiple tumor foci in the liver, without evidence of spread to adjacent normal parenchyma or extrahepatic tissues, and can achieve significant tumor growth inhibition.

Effects of intravenously administered recombinant vesicular stomatitis virus (VSV(deltaM51)) on multifocal and invasive gliomas

BACKGROUND

An ideal virus for the treatment of cancer should have effective delivery into multiple sites within the tumor, evade immune responses, produce rapid viral replication, spread within the tumor, and infect multiple tumors. Vesicular stomatitis virus (VSV) has been shown to be an effective oncolytic virus in a variety of tumor models, and mutations in the matrix (M) protein enhance VSV's effectiveness in animal models.

METHODS

We evaluated the susceptibility of 14 glioma cell lines to infection and killing by mutant strain VSV(deltaM51), which contains a single-amino acid deletion in the M protein. We also examined the activity and safety of this strain against the U87 and U118 experimental models of human malignant glioma in nude mice and analyzed the distribution of the virus in the brains of U87 tumor-bearing mice using fluorescence labeling. Finally, we examined the effect of VSV(deltaM51) on 15 primary human gliomas cultured from surgical specimens. All statistical tests were two-sided.

RESULTS

All 14 glioma cell lines were susceptible to VSV(deltaM51) infection and killing. Intratumoral administration of VSV(deltaM51) produced marked regression of malignant gliomas in nude mice. When administered systemically, live VSV(deltaM51) virus, as compared with dead virus, statistically significantly prolonged survival of mice with unilateral U87 tumors (median survival: 113 versus 46 days, P = .0001) and bilateral U87 tumors (median survival: 73 versus 46 days, P = .0025). VSV(deltaM51) infected multifocal gliomas, invasive glioma cells that migrated beyond the main glioma, and all 15 primary human gliomas. There was no evidence of toxicity.

CONCLUSIONS

Systemically delivered VSV(deltaM51) was an effective and safe oncolytic agent against laboratory models of multifocal and invasive malignant gliomas, the most challenging clinical manifestations of this disease.

International Society for Cell and Gene Therapy of Cancer: 2005 meeting in Shenzhen, China

The 2005 International Society for Cell and Gene Therapy of Cancer (ISCGT) Congress was held in Shenzhen, China (www.iscgtchina2005.com) from December 9th-11th 2005. Here, we describe a representation of the most seminal presentations providing an overview of the progress in the field of cancer gene therapy including the successful introduction of the first approved gene therapy drug.

Establishment of a syngeneic model of hepatic colorectal oligometastases

BACKGROUND

Regional and systemic therapies aimed at improving the outcome for patients with colorectal hepatic metastases have met with modest yet tangible success. Currently, liver resection remains the only curative treatment, but only a minority of patients are candidates for surgery. Animal models are an ideal way to study new treatments for patients with metastatic colorectal cancer. We propose a syngeneic animal model of hepatic colorectal metastases that simulates oligometastases, which is a clinical state considered amenable to regional therapeutic strategies.

MATERIALS AND METHODS

BDIX (BD-9) rats underwent intrasplenic injection of DHD/K12/TRb (Prob/K12) cells to create hepatic metastases via the portal system. After injection of 5 x 10(6) cells, rats underwent laparotomy to determine metastatic burden. Histological analysis confirmed the presence of metastases from resected tumors.

RESULTS

Fifty-three animals were prospectively treated and observed for the development of oligometastases defined as between 1 and 10 hepatic lesions. Thirty-six (68%) of the animals developed detectable metastases while 32 (60%) developed oligometastases (average = 4.40 +/- 2.67). Four animals had overwhelming metastatic liver and peritoneal disease. All animals underwent peritoneal examination and thoracotomy to ensure localized disease. Histological analysis of five hepatectomy specimens confirmed the presence of metastatic cancer. Animals with oligometastases were healthy as evidenced by normal feeding and grooming behavior.

CONCLUSIONS

An animal model of oligometastatic colorectal cancer to the liver can reproducibly mimic the stage IV state in humans conducive to regional therapy and can be used reliably to test novel treatments and mechanisms of metastatic colorectal cancer.

Gene therapy strategies for hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most frequent cancers worldwide. Effective therapy to this cancer is currently lacking, creating an urgent need for new therapeutic strategies for HCC. Gene therapy approach that relies on the transduction of cells with genetic materials, such as apoptotic genes, suicide genes, genes coding for antiangiogenic factors or immunomodulatory molecules, small interfering RNA (siRNA), or oncolytic viral vectors, may provide a promising strategy. The aforementioned strategies have been largely evaluated in the animal models with HCC or liver metastasis. Due to the diversity of vectors and therapeutic genes, being used alone or in combination, gene therapy approach may generate great beneficial effects to control the growth of tumors within the liver.