Gene therapy progress and prospects cancer: oncolytic viruses

Gene Therapy for Regenerative Medicine

The development of biological methods over the past decade has stimulated great interest in the possibility to regenerate human tissues. Advances in stem cell research, gene therapy, and tissue engineering have accelerated the technology in tissue and organ regeneration. However, despite significant progress in this area, there are still several technical issues that must be addressed, especially in the clinical use of gene therapy. The aims of gene therapy include utilising cells to produce a suitable protein, silencing over-producing proteins, and genetically modifying and repairing cell functions that may affect disease conditions. While most current gene therapy clinical trials are based on cell- and viral-mediated approaches, non-viral gene transfection agents are emerging as potentially safe and effective in the treatment of a wide variety of genetic and acquired diseases. Gene therapy based on viral vectors may induce pathogenicity and immunogenicity. Therefore, significant efforts are being invested in non-viral vectors to enhance their efficiency to a level comparable to the viral vector. Non-viral technologies consist of plasmid-based expression systems containing a gene encoding, a therapeutic protein, and synthetic gene delivery systems. One possible approach to enhance non-viral vector ability or to be an alternative to viral vectors would be to use tissue engineering technology for regenerative medicine therapy. This review provides a critical view of gene therapy with a major focus on the development of regenerative medicine technologies to control the in vivo location and function of administered genes.

Therapeutic Applications for Oncolytic Self-Replicating RNA Viruses

Self-replicating RNA viruses have become attractive delivery vehicles for therapeutic applications. They are easy to handle, can be rapidly produced in large quantities, and can be delivered as recombinant viral particles, naked or nanoparticle-encapsulated RNA, or plasmid DNA-based vectors. The self-replication of RNA in infected host cells provides the means for generating much higher transgene expression levels and the possibility to apply substantially reduced amounts of RNA to achieve similar expression levels or immune responses compared to conventional synthetic mRNA. Alphaviruses and flaviviruses, possessing a single-stranded RNA genome of positive polarity, as well as measles viruses and rhabdoviruses with a negative-stranded RNA genome, have frequently been utilized for therapeutic applications. Both naturally and engineered oncolytic self-replicating RNA viruses providing specific replication in tumor cells have been evaluated for cancer therapy. Therapeutic efficacy has been demonstrated in animal models. Furthermore, the safe application of oncolytic viruses has been confirmed in clinical trials. Multiple myeloma patients treated with an oncolytic measles virus (MV-NIS) resulted in increased T-cell responses against the measles virus and several tumor-associated antigen responses and complete remission in one patient. Furthermore, MV-CEA administration to patients with ovarian cancer resulted in a stable disease and more than doubled the median overall survival.

Nanomedicine for Glioblastoma: Progress and Future Prospects

Glioblastoma is the most aggressive form of brain tumor, accounting for the highest mortality and morbidity rates. Current treatment for patients with glioblastoma includes maximal safe tumor resection followed by radiation therapy with concomitant temozolomide (TMZ) chemotherapy. The addition of TMZ to the conformal radiation therapy has improved the median survival time only from 12 months to 16 months in patients with glioblastoma. Despite these aggressive treatment strategies, patients' prognosis remains poor. This therapeutic failure is primarily attributed to the blood-brain barrier (BBB) that restricts the transport of TMZ from reaching the tumor site. In recent years, nanomedicine has gained considerable attention among researchers and shown promising developments in clinical applications, including the diagnosis, prognosis, and treatment of glioblastoma tumors. This review sheds light on the morphological and physiological complexity of the BBB. It also explains the development of nanomedicine strategies to enhance the permeability of drug molecules across the BBB.

Advances in DNA- and RNA-Based Oncolytic Viral Therapeutics and Immunotherapies

The role of viruses has been studied extensively for use as curative cancer therapies. However, the natural immunogenicity of viruses and their interaction with the host’s immune system needs to be examined to determine the full effectiveness of the viral treatment. The prevalence of cancer is increasing globally, and treatments are needed to support the increasing body of patient care. Oncolytic viral therapies used existing pathogenic viruses, which are genetically modified to not cause disease in humans when administered using a vaccine viral vector. Immunotherapies are another avenue of recent interest that has gained much traction. This review will discuss oncolytic viral approaches using three DNA-based viruses, including herpes simplex virus (HSV), vaccinia virus, and adenovirus; as well as four RNA-based viruses, including reovirus, Newcastle disease virus (NDV), poliovirus, and measles virus (MV). It also examines the novel field of cancer-based immunotherapies.

Construction and Characterization of a Novel Recombinant Attenuated and Replication-Deficient Candidate Human Adenovirus Type 3 Vaccine: "Adenovirus Vaccine Within an Adenovirus Vector"

Human adenoviruses (HAdVs) are highly contagious and result in large number of acute respiratory disease (ARD) cases with severe morbidity and mortality. Human adenovirus type 3 (HAdV-3) is the most common type that causes ARD outbreaks in Asia, Europe, and the Americas. However, there is currently no vaccine approved for its general use. The hexon protein contains the main neutralizing epitopes, provoking strong and lasting immunogenicity. In this study, a novel recombinant and attenuated adenovirus vaccine candidate against HAdV-3 was constructed based on a commercially-available replication-defective HAdV-5 gene therapy and vaccine vector. The entire HAdV-3 hexon gene was integrated into the E1 region of the vector by homologous recombination using a bacterial system. The resultant recombinants expressing the HAdV-3 hexon protein were rescued in AD293 cells, identified and characterized by RT-PCR, Western blots, indirect immunofluorescence, and electron microscopy. This potential vaccine candidate had a similar replicative efficacy as the wild-type HAdV-3 strain. However, and importantly, the vaccine strain had been rendered replication-defective and was incapable of replication in A549 cells after more than twenty-generation passages in AD293 cells. This represents a significant safety feature. The mice immunized both intranasally and intramuscularly by this vaccine candidate raised significant neutralizing antibodies against HAdV-3. Therefore, this recombinant, attenuated, and safe adenovirus vaccine is a promising HAdV-3 vaccine candidate. The strategy of using a clinically approved and replication-defective HAdV-5 vector provides a novel approach to develop universal adenovirus vaccine candidates against all the other types of adenoviruses causing ARDs and perhaps other adenovirus-associated diseases.

A bibliometric review of oncolytic virus research as a novel approach for cancer therapy

Background

In recent years, oncolytic viruses (OVs) have drawn attention as a novel therapy to various types of cancers, both in clinical and preclinical cancer studies all around the world. Consequently, researchers have been actively working on enhancing cancer therapy since the early twentieth century. This study presents a systematic review of the literature on OVs, discusses underlying research clusters and, presents future directions of OVs research.

Methods

A total of 1626 published articles related to OVs as cancer therapy were obtained from the Web of Science (WoS) database published between January 2000 and March 2020. Various aspects of OVs research, including the countries/territories, institutions, journals, authors, citations, research areas, and content analysis to find trending and emerging topics, were analysed using the bibliometrix package in the R-software.

Results

In terms of the number of publications, the USA based researchers were the most productive (n = 611) followed by Chinese (n = 197), and Canadian (n = 153) researchers. The Molecular Therapy journal ranked first both in terms of the number of publications (n = 133) and local citations (n = 1384). The most prominent institution was Mayo Clinic from the USA (n = 117) followed by the University of Ottawa from Canada (n = 72), and the University of Helsinki from Finland (n = 63). The most impactful author was Bell J.C with the highest number of articles (n = 67) and total local citations (n = 885). The most impactful article was published in the Cell journal. In addition, the latest OVs research mainly builds on four research clusters.

Conclusion

The domain of OVs research has increased at a rapid rate from 2000 to 2020. Based on the synthesis of reviewed studies, adenovirus, herpes simplex virus, reovirus, and Newcastle disease virus have shown potent anti-cancer activity. Developed countries such as the USA, Canada, the UK, and Finland were the most productive, hence, contributed most to this field. Further collaboration will help improve the clinical research translation of this therapy and bring benefits to cancer patients worldwide.

Canine Parvovirus and Its Non-Structural Gene 1 as Oncolytic Agents: Mechanism of Action and Induction of Anti-Tumor Immune Response

The exploration into the strategies for the prevention and treatment of cancer is far from complete. Apart from humans, cancer has gained considerable importance in animals because of increased awareness towards animal health and welfare. Current cancer treatment regimens are less specific towards tumor cells and end up harming normal healthy cells. Thus, a highly specific therapeutic strategy with minimal side effects is the need of the hour. Oncolytic viral gene therapy is one such specific approach to target cancer cells without affecting the normal cells of the body. Canine parvovirus (CPV) is an oncolytic virus that specifically targets and kills cancer cells by causing DNA damage, caspase activation, and mitochondrial damage. Non-structural gene 1 (NS1) of CPV, involved in viral DNA replication is a key mediator of cytotoxicity of CPV and can selectively cause tumor cell lysis. In this review, we discuss the oncolytic properties of Canine Parvovirus (CPV or CPV2), the structure of the NS1 protein, the mechanism of oncolytic action as well as role in inducing an antitumor immune response in different tumor models.

Combination Therapy of Novel Oncolytic Adenovirus with Anti-PD1 Resulted in Enhanced Anti-Cancer Effect in Syngeneic Immunocompetent Melanoma Mouse Model

Malignant melanoma, an aggressive form of skin cancer, has a low five-year survival rate in patients with advanced disease. Immunotherapy represents a promising approach to improve survival rates among patients at advanced stage. Herein, the aim of the study was to design and produce, by using engineering tools, a novel oncolytic adenovirus AdV-D24- inducible co-stimulator ligand (ICOSL)-CD40L expressing potent co-stimulatory molecules enhancing clinical efficacy through the modulation of anti-cancer immune responses. Firstly, we demonstrated the vector's identity and genetic stability by restriction enzyme assay and sequencing, then, by performing in vitro and in vivo pre-clinical studies we explored the anti-cancer efficacy of the virus alone or in combination with anti PD-1 inhibitor in human melanoma cell lines, i.e., MUG Mel-1 and MUG Mel-2, and in immunocompetent C57BL/6 melanoma B16V mouse model. We showed that both monotherapy and combination approaches exhibit enhanced anti-cancer ability and immunogenic cell death in in vitro settings. Furthermore, AdV-D24-ICOSL-CD40L combined with anti PD-1 revealed a fall in tumor volume and 100% survival in in vivo context, thus suggesting enhanced efficacy and survival via complementary anti-cancer properties of those agents in melanoma therapy. Collectively, the novel oncolytic vector AdV-D24-ICOSL-CD40L alone or in combination with anticancer drugs, such as check point inhibitors, may open novel therapeutic perspectives for the treatment of melanoma.

Self-assembled Viral Nanoparticles as Targeted Anticancer Vehicles

Viral nanoparticles (VNPs) comprise a variety of mammalian viruses, plant viruses, and bacteriophages, that have been adopted as building blocks and supra-molecular templates in nanotechnology. VNPs demonstrate the dynamic, monodisperse, polyvalent, and symmetrical architectures which represent examples of such biological templates. These programmable scaffolds have been exploited for genetic and chemical manipulation for displaying of targeted moieties together with encapsulation of various payloads for diagnosis or therapeutic intervention. The drug delivery system based on VNPs offer diverse advantages over synthetic nanoparticles, including biocompatibility, biodegradability, water solubility, and high uptake capability. Here we summarize the recent progress of VNPs especially as targeted anticancer vehicles from the encapsulation and surface modification mechanisms, involved viruses and VNPs, to their application potentials.

Development of a New Hyaluronic Acid Based Redox-Responsive Nanohydrogel for the Encapsulation of Oncolytic Viruses for Cancer Immunotherapy

Oncolytic viruses (OVs) are emerging as promising and potential anti-cancer therapeutic agents, not only able to kill cancer cells directly by selective intracellular viral replication, but also to promote an immune response against tumor. Unfortunately, the bioavailability under systemic administration of OVs is limited because of undesired inactivation caused by host immune system and neutralizing antibodies in the bloodstream. To address this issue, a novel hyaluronic acid based redox responsive nanohydrogel was developed in this study as delivery system for OVs, with the aim to protect the OVs following systemic administration. The nanohydrogel was formulated by water in oil (W/O) nanoemulsion method and cross-linked by disulfide bonds derived from the thiol groups of synthesized thiolated hyaluronic acid. One DNA OV Ad[I/PPT-E1A] and one RNA OV Rigvir^® ECHO-7 were encapsulated into the developed nanohydrogel, respectively, in view of their potential of immunovirotherapy to treat cancers. The nanohydrogels showed particle size of approximately 300–400 nm and negative zeta potential of around −13 mV by dynamic light scattering (DLS). A uniform spherical shape of the nanohydrogel was observed under the scanning electron microscope (SEM) and transmission electron microscope (TEM), especially, the successfully loading of OV into nanohydrogel was revealed by TEM. The crosslinking between the hyaluronic acid chains was confirmed by the appearance of new peak assigned to disulfide bond in Raman spectrum. Furthermore, the redox responsive ability of the nanohydrogel was determined by incubating the nanohydrogel into phosphate buffered saline (PBS) pH 7.4 with 10 μM or 10 mM glutathione at 37 °C which stimulate the normal physiological environment (extracellular) or reductive environment (intracellular or tumoral). The relative turbidity of the sample was real time monitored by DLS which indicated that the nanohydrogel could rapidly degrade within 10 h in the reductive environment due to the cleavage of disulfide bonds, while maintaining the stability in the normal physiological environment after 5 days. Additionally, in vitro cytotoxicity assays demonstrated a good oncolytic activity of OVs-loaded nanohydrogel against the specific cancer cell lines. Overall, the results indicated that the developed nanohydrogel is a delivery system appropriate for viral drugs, due to its hydrophilic and porous nature, and also thanks to its capacity to maintain the stability and activity of encapsulated viruses. Thus, nanohydrogel can be considered as a promising candidate carrier for systemic administration of oncolytic immunovirotherapy.

Basic stochastic model for tumor virotherapy

The complexity of oncolytic virotherapy arises from many factors. In this study, we incorporate environmental noise and stochastic effects to our basic deterministic model and propose a stochastic model for viral therapy in terms of Ito stochastic differential equations. We conduct a detailed analysis of the model using boundary methods. We find two combined parameters, one describes possibilities of eradicating tumors and one is an increasing function of the viral burst size, which serve as thresholds to classify asymptotical dynamics of the model solution paths. We show there are three ergodic invariant probability measures which correspond to equilibrium states of the deterministic model, and extra possibility to eradicate tumor due to strong variance of tumor growth rate and medium viral burst size. Numerical analysis demonstrates several typical solution paths with biological explanations. In addition, we provide some medical interpretations and implications.

Virus specific tolerance enhanced efficacy of cancer immuno-virotherapy

BACKGROUND

Activation of the immune system to fight cancer is a major goal in immunology and oncology. Although cancer treatment using oncolytic viruses shows promising results, virus mediated oncolysis induces a weak anti-tumor immune response. Upon application of viruses, immune responses against the virus play a significant role in limiting tumor virotherapy. Although suppression of host immunity increases the efficacy of virotherapy against the tumor, but inhibits anti-tumor immune responses. Induction of viral specific tolerance before viral replication may cause the virus to efficiently replicate in tumor cells without affecting the immune responses against tumor antigens. Investigation of the combined strategy of virotherapy and immunotherapy using irradiated tumor cells along with IL-2 and interferon-alpha in virus specific tolerant mice was the goal of this study.

MATERIALS AND METHODS

For tolerance induction, the newborn mice were injected with vesicular stomatitis virus (VSV) subcutaneously. After injection of TC-1 tumor cells to adult tolerant mice and formation of a tumor, irradiated TC-1 cells along with IL-2 and Interferon-alpha expression plasmid were injected twice in mice and followed by virotherapy. Size of tumors and CTL activity against the virus and tumor cells were measured.

RESULT

The results showed increased efficacy of virotherapy in combination with immune-stimulators and tumor cells injection in tolerant mice compared to normal mice.

CONCLUSION

Specific tolerance against the oncolytic virus enhances the efficacy of virotherapy both in monotherapy and in combination with immunotherapy.

Use of stem cells as carriers of oncolytic viruses for cancer treatment

Therapeutic application of stem cells and oncolytic viruses in cancer treatment has rapidly increased in the last decade. Oncolytic viruses are considered as a new class of anticancer agents because of their ability to selectively infect and destroy cancer cells. Furthermore, regarding the specific migratory capacity of stem cells, they can be used as carriers or vectors targeting metastatic cancer. Promising results have been reported regarding the use of stem cells and oncolytic viruses as a therapeutic approach for the treatment of metastatic cancer. The present review aimed to determine the approaches involved in the use of the tumor-homing capacity of stem cells for cancer treatment.

Viral vector: potential therapeutic for glioblastoma multiforme

Glioblastoma multiforme is a highly malignant primary brain tumour found in adults and is highlighted as the most devastating among all the other grades of glioma. Well-established standard treatment methods, such as chemotherapy, radiation and surgery, have resulted in modest improvement in the survival of patients. Hence, the arduous search for novel treatments backed by advancements in molecular biology still persists. Glioblastoma has many distinctive characteristics, which makes it a potential candidate for gene therapy. Gene therapy involves the delivery of genetic material of therapeutic use into tumour cells, which produces a specific antitumour response. Moreover, viruses stimulate a vigorous cytotoxic effect, they are easily modifiable and the inherent property of horizontal transfer of genetic material makes them valuable tools for genetic engineering. In this review, we have enlisted the various viral vectors employed in gene therapy for glioblastoma.

Investigating Ions at Amphiphilic Monolayers with X-ray Fluorescence

Amphiphilic monolayers formed at the soft air/liquid interface are easy-to-handle and versatile model systems for material and life sciences. Helmuth Möhwald was one of the pioneers in this field. Over the last few decades, total-reflection X-ray fluorescence (TRXF) has become an important analytical tool for the investigation of monolayer interactions with ions. Here, the theoretical background of TRXF is described, and practical aspects are discussed. The experimentally determined fluorescence intensity from the adsorbed ions can be interpreted quantitatively either by a calibration procedure utilizing monolayers with known charge density or by calibration with respect to the bare aqueous surface. Both calibration approaches yield quantitatively consistent results within <10% accuracy. Some examples demonstrating the power of TRXF for the study of ion adsorption to charged and noncharged monolayers as well as for the characterization of the physicochemical properties of novel cationic lipids used for improved gene delivery are given.

Matrix Mediated Viral Gene Delivery: A Review

Polymeric matrices inherently protect viral vectors from pre-existing immune conditions, limit dissemination to off-target sites, and can sustain vector release. Advancing methodologies in development of particulate based vehicles have led to improved encapsulation of viral vectors. Polymeric delivery systems have contributed to increasing cellular transduction, responsive release mechanisms, cellular infiltration, and cellular signaling. Synthetic polymers are easily customizable, and are capable of balancing matrix retention with cellular infiltration. Natural polymers contain inherent biorecognizable motifs adding therapeutic efficacy to the incorporated viral vector. Recombinant polymers use highly conserved motifs to carefully engineer matrices, allowing for precise design including elements of vector retention and responsive release mechanisms. Composite polymer systems provide opportunities to create matrices with unique properties. Carefully designed matrices can control spatiotemporal release patterns that synergize with approaches in regenerative medicine and antitumor therapies.

Dual-vector prodrug activator gene therapy using retroviral replicating vectors

Retroviral replicating vectors (RRVs) have been shown to achieve efficient tumor transduction and enhanced therapeutic benefits in a variety of cancer models. In the present study, we evaluated a possible combinatorial effect of prodrug activator genes delivered by two different RRVs derived from amphotropic murine leukemia virus (AMLV) and gibbon ape leukemia virus (GALV) on human hepatocellular carcinoma Hep3B cells. Both RRVs showed efficient replicative spread in culture and can overcame superinfection resistance each other. Notably, the replication and spread of each RRV in culture remained unaffected by pretransduction with the counterpart RRV. We further transduced cells with RRVs which individually possessed the prodrug activator genes yeast cytosine deaminase (CD) and herpes simplex virus thymidine kinase (TK) alone or in combination, and evaluated the cytotoxic effects of RRV-mediated gene therapy with CD and TK in the presence of the respective prodrugs, 5-fluorocytosine and ganciclovir. All combinations of the two prodrug activator genes produced synergistic cytocidal effects, but the combined effects of the different genes were significantly greater than those of the same genes when delivered by two different vectors. The present findings indicate the potential utility of dual-vector gene therapy using two different RRVs carrying different prodrug activator genes.

Efficient tumor transduction and antitumor efficacy in experimental human osteosarcoma using retroviral replicating vectors

Retroviral replicating vectors (RRVs) have achieved efficient tumor transduction and enhanced therapeutic benefit in a wide variety of cancer models. Here, we evaluated two different RRVs derived from amphotropic murine leukemia virus (AMLV) and gibbon ape leukemia virus (GALV), which utilize different cellular receptors (PiT-2 and PiT-1, respectively) for viral entry, in human osteosarcoma cells. Quantitative RT-PCR showed that low levels of expression of both receptors were observed in normal and non-malignant cells. However, high PiT-2 (for AMLV) and low PiT-1 (for GALV) expression was observed in most osteosarcoma cell lines. Accordingly, AMLV expressing the green fluorescent protein gene infected and replicated more efficiently than GALV in most osteosarcoma cell lines. Furthermore, RRVs expressing the cytosine deaminase prodrug activator gene showed differential cytotoxicity that correlated with the results of viral spread. AMLV-RRV-mediated prodrug activator gene therapy achieved significant inhibition of subcutaneous MG-63 tumor growth over GALV in nude mice. These data indicate that AMLV vectors predominate over GALV in human osteosarcoma cells. Moreover, our findings support the potential utility of the two RRVs in personalized cancer virotherapy on the basis of receptor expression.

Viral Vectors in Gene Therapy

Applications of viral vectors have found an encouraging new beginning in gene therapy in recent years. Significant improvements in vector engineering, delivery, and safety have placed viral vector-based therapy at the forefront of modern medicine. Viral vectors have been employed for the treatment of various diseases such as metabolic, cardiovascular, muscular, hematologic, ophthalmologic, and infectious diseases and different types of cancer. Recent development in the area of immunotherapy has provided both preventive and therapeutic approaches. Furthermore, gene silencing generating a reversible effect has become an interesting alternative, and is well-suited for delivery by viral vectors. A number of preclinical studies have demonstrated therapeutic and prophylactic efficacy in animal models and furthermore in clinical trials. Several viral vector-based drugs have also been globally approved.

Lysine-based amino-functionalized lipids for gene transfection: the protonation state in monolayers at the air-liquid interface

Cationic lipids are considered as non-viral carriers for genetic material used in gene therapy. They have no carcinogenic potential and cause low immune response compared to existing viral systems. The protonation degree of these cationic lipids is a crucial parameter for the binding behavior of polynucleotides (e.g., DNA). Newly synthesized peptide-mimic lysine-based amino-functionalized lipids have been investigated in 2D models as monolayers at the air-liquid interface. Standard surface pressure - area isotherms have been measured to prove the layer stability. Total reflection X-ray fluorescence (TRXF) has been used as a surface sensitive analytical method to estimate the amount of counterions at the head groups. Using a standard sample as a reference, the protonation degree of these cationic lipids can be quantified on buffers with different pH values. It is found that the protonation degree depends linearly on the packing density of the lipid monolayer.

New frontiers in oncolytic viruses: optimizing and selecting for virus strains with improved efficacy

Oncolytic viruses have demonstrated selective replication and killing of tumor cells. Different types of oncolytic viruses – adenoviruses, alphaviruses, herpes simplex viruses, Newcastle disease viruses, rhabdoviruses, Coxsackie viruses, and vaccinia viruses – have been applied as either naturally occurring or engineered vectors. Numerous studies in animal-tumor models have demonstrated substantial tumor regression and prolonged survival rates. Moreover, clinical trials have confirmed good safety profiles and therapeutic efficacy for oncolytic viruses. Most encouragingly, the first cancer gene-therapy drug – Gendicine, based on oncolytic adenovirus type 5 – was approved in China. Likewise, a second-generation oncolytic herpes simplex virus-based drug for the treatment of melanoma has been registered in the US and Europe as talimogene laherparepvec.

Advances in the mechanisms of action of cancer-targeting oncolytic viruses

Cancer virotherapy mediated by oncolytic viruses (OV), has emerged as a novel and effective strategy in cancer therapeutics. Preclinical models have demonstrated anticancer activity against numerous types of cancer. Currently, a number of recombinant viruses are in late phase clinical trials, many of which have demonstrated promising results regarding the safety and reliability of the treatments, particularly when combined with standard antineoplastic therapies. In addition to molecular-targeted therapeutics, genetic engineering of the viruses allows functional complementation to chemotherapy or radiotherapy agents. Co-administration of chemotherapy or radiotherapy is imperative for an effective treatment regime. Additionally, these approaches may be used in combination with current treatments to assist in cancer management. The near future may reveal whether this renewed interest in oncological virotherapy will result in meaningful therapeutic effects in patients. The aim of the present review was to highlight how the knowledge of oncolytic viral specificity and cytotoxicity has advanced in recent years, with a view to discuss OV in clinical application and the future directions of this field.

Canine Parvovirus ns1 gene and Chicken Anemia vp3 gene induce partial oncolysis of Canine Transmissible Venereal Tumor

The oncolytic effect of Canine Parvovirus ns1 gene and Chicken Anemia vp3 gene in naturally occurring cases of Canine Transmissible Venereal Tumor (CTVT) is being reported. Dogs suffering from CTVT (N = 18) were systematically randomized into three groups viz. A, B, and C (n = 6). Animals of the groups A, B, and C received 100 µg of the ns1 gene, vp3 gene, and ns1  +  vp3 gene combination, respectively, for three weeks intratumorally at weekly intervals; results were normalized against base values before commencement of therapy and after complete remission that were taken as negative and positive controls, respectively. Initiation of oncolytic gene therapy arrested the further progression of the tumor but most of the animals in the study underwent incomplete remission, indicating incomplete activity of ns1 and vp3 genes. The oncolytic effect of the treatments was in the order ns1 > vp3 > ns1 + vp3. Oncolysis was accompanied by decreased mitotic index and AgNOR count, and increased TUNEL positive cells and CD4⁺ lymphocyte counts. Our findings show that Canine Parvovirus ns1 may eventually find an important role as an oncolytic agent.

Monitoring the Efficacy of Oncolytic Viruses via Gene Expression

With the recent success of oncolytic viruses in clinical trials, efforts toward improved monitoring of the viruses and their mechanism have intensified. Four main gene expression strategies have been employed to date including: analyzing overall gene expression in tumor cells, looking at gene expression of a few specific genes in the tumor cells, focusing on gene expression of specific transgenes introduced into the virus, and following gene expression of certain viral genes. Each strategy presents certain advantages and disadvantages over the others. Various methods to organize the dysregulated genes into clusters have provided a window into the mechanism of action for these viruses. Methodologically, the combined approach of looking at both overall gene expression, the tumor cells and gene expression of viral genes, enables researchers to assess correlation between the introduction of the virus and the changes in the tumor. This would seem to be the most productive approach for future studies, providing much information on mechanism and timing.

Latest trends in cancer therapy applying viral vectors

Gene therapy based on viral vectors has demonstrated steady progress recently, not only in the area of cancers. A multitude of viral vectors has been engineered for both preventive and therapeutic applications. Two main approaches comprise of viral vector-based delivery of toxic or anticancer genes or immunization with anticancer antigens. Tumor growth inhibition and tumor regression have been observed, providing improved survival rates in animal tumor models. Furthermore, vaccine-based cancer immunotherapy has demonstrated both tumor regression and protection against challenges with lethal doses of tumor cells. Several clinical trials with viral vectors have also been conducted. Additionally, viral vector-based cancer drugs have been approved. This review gives an overview of different viral vector systems and their applications in cancer gene therapy.

Hitting the nail on the head: combining oncolytic adenovirus-mediated virotherapy and immunomodulation for the treatment of glioma

Glioblastoma is a highly aggressive malignant brain tumor with a poor prognosis and the median survival 14.6 months. Immunomodulatory proteins and oncolytic viruses represent two treatment approaches that have recently been developed for patients with glioblastoma that could extend patient survival and result in better treatment outcomes for patients with this disease. Together, these approaches could potentially augment the treatment efficacy and strength of these anti-tumor therapies. In addition to oncolytic activities, this combinatory approach introduces immunomodulation locally only where cancerous cells are present. This thereby results in the change of the tumor microenvironment from immune-suppressive to immune-vulnerable via activation of cytotoxic T cells or through the removal of glioma cells immune-suppressive capability. This review discusses the strengths and weaknesses of adenoviral oncolytic therapy, and highlights the genetic modifications that result in more effective and targeted viral agents. Additionally, the mechanism of action of immune-activating agents is described and the results of previous clinical trials utilizing these treatments in other solid tumors are reviewed. The feasibility, synergy, and limitations for treatments that combine these two approaches are outlined and areas for which more work is needed are considered.

Polymeric Nanoparticle-Mediated Gene Delivery for Lung Cancer Treatment

In recent years, researchers have focused on targeted gene therapy for lung cancer, using nanoparticle carriers to overcome the limitations of conventional treatment methods. The main goal of targeted gene therapy is to develop more efficient therapeutic strategies by improving the bioavailability, stability, and target specificity of gene therapeutics and to reduce off-target effects. Polymer-based nanoparticles, an alternative to lipid and inorganic nanoparticles, efficiently carry nucleic acid therapeutics and are stable in vivo. Receptor-targeted delivery is a promising approach that can limit non-specific gene delivery and can be achieved by modifying the polymer nanoparticle surface with specific receptor ligands or antibodies. This review highlights the recent developments in gene delivery using synthetic and natural polymer-based nucleic acid carriers for lung cancer treatment. Various nanoparticle systems based on polymers and polymer combinations are discussed. Further, examples of targeting ligands or moieties used in targeted, polymer-based gene delivery to lung cancer are reviewed.

Tanapoxvirus lacking a neuregulin-like gene regresses human melanoma tumors in nude mice

Neuregulin (NRG), an epidermal growth factor is known to promote the growth of various cell types, including human melanoma cells through ErbB family of tyrosine kinases receptors. Tanapoxvirus (TPV)-encoded protein TPV-15L, a functional mimic of NRG, also acts through ErbB receptors. Here, we show that the TPV-15L protein promotes melanoma proliferation. TPV recombinant generated by deleting the 15L gene (TPVΔ15L) showed replication ability similar to that of wild-type TPV (wtTPV) in owl monkey kidney cells, human lung fibroblast (WI-38) cells, and human melanoma (SK-MEL-3) cells. However, a TPV recombinant with both 15L and the thymidine kinase (TK) gene 66R ablated (TPVΔ15LΔ66R) replicated less efficiently compared to TPVΔ15L and the parental virus. TPVΔ15L exhibited more robust tumor regression in the melanoma-bearing nude mice compared to other TPV recombinants. Our results indicate that deletion of TPV-15L gene product which facilitates the growth of human melanoma cells can be an effective strategy to enhance the oncolytic potential of TPV for the treatment of melanoma.

Gene Therapy: A Paradigm Shift in Dentistry

Gene therapy holds a promising future for bridging the gap between the disciplines of medicine and clinical dentistry. The dynamic treatment approaches of gene therapy have been advancing by leaps and bounds. They are transforming the conventional approaches into more precise and preventive ones that may limit the need of using drugs and surgery. The oral cavity is one of the most accessible areas for the clinical applications of gene therapy for various oral tissues. The idea of genetic engineering has become more exciting due to its advantages over other treatment modalities. For instance, the body is neither subjected to an invasive surgery nor deep wounds, nor is it susceptible to systemic effects of drugs. The aim of this article is to review the gene therapy applications in the field of dentistry. In addition, therapeutic benefits in terms of treatment of diseases, minimal invasion and maximum outcomes have been discussed.

Etoposide enhances antitumor efficacy of MDR1-driven oncolytic adenovirus through autoupregulation of the MDR1 promoter activity

Conditionally replicating adenoviruses (CRAds), or oncolytic adenoviruses, such as E1B55K-deleted adenovirus, are attractive anticancer agents. However, the therapeutic efficacy of E1B55K-deleted adenovirus for refractory solid tumors has been limited. Environmental stress conditions may induce nuclear accumulation of YB-1, which occurs in multidrug-resistant and adenovirus-infected cancer cells. Overexpression and nuclear localization of YB-1 are associated with poor prognosis and tumor recurrence in various cancers. Nuclear YB-1 transactivates the multidrug resistance 1 (MDR1) genes through the Y-box. Here, we developed a novel E1B55K-deleted adenovirus driven by the MDR1 promoter, designed Ad5GS3. We tested the feasibility of using YB-1 to transcriptionally regulate Ad5GS3 replication in cancer cells and thereby to enhance antitumor efficacy. We evaluated synergistic antitumor effects of oncolytic virotherapy in combination with chemotherapy. Our results show that adenovirus E1A induced E2F-1 activity to augment YB-1 expression, which shut down host protein synthesis in cancer cells during adenovirus replication. In cancer cells infected with Ad5WS1, an E1B55K-deleted adenovirus driven by the E1 promoter, E1A enhanced YB-1 expression, and then further phosphorylated Akt, which, in turn, triggered nuclear translocation of YB-1. Ad5GS3 in combination with chemotherapeutic agents facilitated nuclear localization of YB-1 and, in turn, upregulated the MDR1 promoter activity and enhanced Ad5GS3 replication in cancer cells. Thus, E1A, YB-1, and the MDR1 promoter form a positive feedback loop to promote Ad5GS3 replication in cancer cells, and this regulation can be further augmented when chemotherapeutic agents are added. In the in vivo study, Ad5GS3 in combination with etoposide synergistically suppressed tumor growth and prolonged survival in NOD/SCID mice bearing human lung tumor xenografts. More importantly, Ad5GS3 exerted potent oncolytic activity against clinical advanced lung adenocarcinoma, which was associated with elevated levels of nuclear YB-1 and cytoplasmic MDR1 expression in the advanced tumors. Therefore, Ad5GS3 may have therapeutic potential for cancer treatment, especially in combination with chemotherapy. Because YB-1 is expressed in a broad spectrum of cancers, this oncolytic adenovirus may be broadly applicable.

Going viral: a review of replication-selective oncolytic adenoviruses

Oncolytic viruses have had a tumultuous course, from the initial anecdotal reports of patients having antineoplastic effects after natural viral infections a century ago to the development of current cutting-edge therapies in clinical trials. Adenoviruses have long been the workhorse of virotherapy, and we review both the scientific and the not-so-scientific forces that have shaped the development of these therapeutics from wild-type viral pathogens, turning an old foe into a new friend. After a brief review of the mechanics of viral replication and how it has been modified to engineer tumor selectivity, we give particular attention to ONYX-015, the forerunner of virotherapy with extensive clinical testing that pioneered the field. The findings from those as well as other oncolytic trials have shaped how we now view these viruses, which our immune system has evolved to vigorously attack, as promising immunotherapy agents.

Polyethyleneimine-modified calcium carbonate nanoparticles for p53 gene delivery

In this study, calcium carbonate (CaCO3) nanoparticles with spherical structure were regulated by arginine and successfully synthesized via a facile co-precipitation method. The average particle size of as-prepared CaCO3 was about 900 nm. The properties of nanostructured CaCO3 particles were characterized by scanning electron microscope, Fourier transform infrared spectroscopy, X-ray diffraction and size distribution. After modified with polyethyleneimine (PEI), the ability of PEI-CaCO3 nanoparticles to carry GFP-marked p53 gene (pEGFP-C1-p53) into cancer cells to express P53 protein were studied. Meanwhile, the cytotoxicity, transfection efficiency, cells growth inhibition and the ability to induce apoptosis by expressed P53 protein were conducted to evaluate the performances of PEI-CaCO3 nanoparticles. The results show that prepared PEI-CaCO3 nanoparticles had good biocompatibility and low cytotoxicity in a certain concentration range. PEI-CaCO3 effectively transfected pEGFP-C1 gene into epithelial-like cancer cells. And with the expression of GFP-P53 fusion protein, pEGFP-C1-p53-gene-loaded PEI-CaCO3 particles significantly reduced the proliferation of cancer cells. These findings indicate that our PEI-modified CaCO3 nanoparticles are potential to be successfully used as carriers for gene therapy.

Therapy of prostate cancer using a novel cancer terminator virus and a small molecule BH-3 mimetic

Despite recent advances, treatment options for advanced prostate cancer (CaP) remain limited. We are pioneering approaches to treat advanced CaP that employ conditionally replication-competent oncolytic adenoviruses that simultaneously produce a systemically active cancer-specific therapeutic cytokine, mda-7/IL-24, Cancer Terminator Viruses (CTV). A truncated version of the CCN1/CYR61 gene promoter, tCCN1-Prom, was more active than progression elevated gene-3 promoter (PEG-Prom) in regulating transformation-selective transgene expression in CaP and oncogene-transformed rat embryo cells. Accordingly, we developed a new CTV, Ad.tCCN1-CTV-m7, which displayed dose-dependent killing of CaP without harming normal prostate epithelial cells in vitro with significant anti-cancer activity in vivo in both nude mouse CaP xenograft and transgenic Hi-Myc mice (using ultrasound-targeted microbubble (MB)-destruction, UTMD, with decorated MBs). Resistance to mda-7/IL-24-induced cell deathcorrelated with overexpression of Bcl-2 family proteins. Inhibiting Mcl-1 using an enhanced BH3 mimetic, BI-97D6, sensitized CaP cell lines to mda-7/IL-24-induced apoptosis. Combining BI-97D6 with Ads expressing mda-7/IL-24promoted ER stress, decreased anti-apoptotic Mcl-1 expression and enhanced mda-7/IL-24expression through mRNA stabilization selectively in CaP cells. In Hi-myc mice, the combination induced enhanced apoptosis and tumor growth suppression. These studies highlight therapeutic efficacy of combining a BH3 mimetic with a novel CTV, supporting potential clinical applications for treating advanced CaP.

Experimental Adaptation of Rotaviruses to Tumor Cell Lines

A number of viruses show a naturally extended tropism for tumor cells whereas other viruses have been genetically modified or adapted to infect tumor cells. Oncolytic viruses have become a promising tool for treating some cancers by inducing cell lysis or immune response to tumor cells. In the present work, rotavirus strains TRF-41 (G5) (porcine), RRV (G3) (simian), UK (G6-P5) (bovine), Ym (G11-P9) (porcine), ECwt (murine), Wa (G1-P8), Wi61 (G9) and M69 (G8) (human), and five wild-type human rotavirus isolates were passaged multiple times in different human tumor cell lines and then combined in five different ways before additional multiple passages in tumor cell lines. Cell death caused by the tumor cell-adapted isolates was characterized using Hoechst, propidium iodide, 7-AAD, Annexin V, TUNEL, and anti-poly-(ADP ribose) polymerase (PARP) and -phospho-histone H2A.X antibodies. Multiple passages of the combined rotaviruses in tumor cell lines led to a successful infection of these cells, suggesting a gain-of-function by the acquisition of greater infectious capacity as compared with that of the parental rotaviruses. The electropherotype profiles suggest that unique tumor cell-adapted isolates were derived from reassortment of parental rotaviruses. Infection produced by such rotavirus isolates induced chromatin modifications compatible with apoptotic cell death.

Oncolytic viruses for therapy of malignant glioma

Effective treatment of malignant brain tumors is still an open problem. Location of tumor in vital areas of the brain significantly limits capasities of surgical treatment. The presence of tumor stem cells resistant to radiation and anticancer drugs in brain tumor complicates use of chemoradiotherapy and causes a high rate of disease recurrence. A technological improvement in bioselection and production of recombinant resulted in creation of viruses with potent oncolytic properties against glial tumors. Recent studies, including clinical trials, showed, that majority of oncolytic viruses are safe. Despite the impressive results of the viral therapy in some patients, the treatment of other patients is not effective; therefore, further improvement of the methods of oncolytic virotherapy is necessary. High genetic heterogeneity of glial tumor cells even within a single tumor determines differences in individual sensitivity of tumor cells to oncolytic viruses. This review analyses the most successful oncolytic virus strains, including those which had reached clinical trials, and discusses the prospects for new approaches to virotherapy of gliomas.

Characterization of an Oncolytic Adenovirus Vector Constructed to Target the cMet Receptor

The cMet receptor is a homodimer with tyrosine kinase activity. Upon stimulation with its ligand, hepatocyte growth factor (HGF), the receptor mediates wide physiologic actions. The HGF-cMet signaling pathway is dysregulated in many cancers, which makes cMet an important target for novel therapeutic interventions. Oncolytic adenoviruses (Ads) have been used for the past three decades as a promising therapeutic approach for a wide array of neoplastic diseases. To date, achieving cancer-specific replication of oncolytic Ads has been accomplished by either viral genome deletions or by incorporating tumor selective promoters. To achieve novel specificity of oncolytic Ad infection of cancer cells that overexpress cMet, we inserted the HGF NK2 sequence, corresponding to a competitive antagonist of HGF binding to the cMet receptor, into the Ad serotype 5 (Ad5) fiber gene. The resulting vector, Ad5-pIX-RFP-FF/NK2, was rescued, amplified in HEK293 cells, and characterized. Binding specificity and viral infectivity were tested in various cancer cell lines that express varying levels of cMet and hCAR (the Ad5 receptor). We found that Ad5-pIX-RFP-FF/NK2 demonstrated binding specificity to the cMet receptor. In addition, there was enhanced viral infectivity and virus replication compared with a non-targeted Ad vector. Although NK2 weakly induces cMet receptor activation, our results showed no receptor phosphorylation in the context of an oncolytic Ad virus. In summary, these results suggest that an oncolytic Ad retargeted to the cMet receptor is a promising vector for developing a novel cancer therapeutic agent.

Metabolic alteration--Overcoming therapy resistance in gastric cancer via PGK-1 inhibition in a combined therapy with standard chemotherapeutics

BACKGROUND AND OBJECTIVES

It can be assumed that PGK1 is involved in metastatic spread of gastric carcinomas. Furthermore PGK1 has a proven influence on the characteristics of tumor stem cells. The presence of malignant stem cells, regarding treatment resistance and recurrence, is of considerable importance. We hypothesized that inhibition of PGK1 makes these cells more sensitive to chemotherapeutic agents and therefore mediates an overcome of the existing therapy resistance.

METHODS

All investigations were performed with human gastric adenocarcinoma cell lines. Small hairpin RNA knockdown of PGK1 via adenovirus-shPGK1 was used for PGK1-inhibition. Chemotherapeutic agents were 5-FU and mitomycin. FACS, qRT-PCR, and xCELLigence were performed.

RESULTS

Using the medium-sole-control indicating the highest cell viability and Triton indicating the lowest, mitomycin and 5-FU alone showed a significant decrease in cell viability. The treatment with AdvshPGK1 alone already showed a better decrease. The simultaneous application of chemotherapeutics and adenovirus showed the strongest effect and is comparable to the effect of Triton.

CONCLUSIONS

We showed a significant decrease in cell viability after the simultaneous application of chemotherapeutics and adenovirus. These results suggest that PGK1-inhibition is able to increase the vulnerability of gastric cancer cells and tumor stem cells to overcome the chemotherapeutic therapy resistance.

The antitumor effects of oncolytic adenovirus H101 against lung cancer

Lung cancer is the leading cause of cancer mortality in both men and women, with dismal survival rates due to late-stage diagnoses and a lack of efficacious therapies. The new treatment options with completely novel mechanism of therapeutic activity are needed for lung cancer to improve patient outcome. The present study was aimed at testing the efficacy of recombinant adenovirus H101 as an oncolytic agent for killing human lung cancer cell lines in vitro and in vivo. We assessed the coxsackievirus adenovirus receptor (CAR) expression on human lung cancer cell lines by RT-PCR and immunocytochemistry staining. Viral infectivity and viral replication in lung cancer cells was assayed by flow cytometry and real-time fluorescent quantitative PCR. After H101 treatment, cytotoxic effect, cell cycle progression and apoptosis were further examined by lactate dehydrogenase release assay and flow cytometry in vitro, respectively. In vivo, antitumor effects of H101 were assessed on SCID Beige mice xenografted with human lung cancer cells. Receptor characterization confirmed that human lung cancer cell lines expressed CAR receptor for adenovirus type 5. Lung cancer cells were sensitive to infection by the H101 virus. H101 infection and replication resulted in very potent cytotoxicity, G2/M phase arrest and cell lysis. In vivo, we also showed that H101 significantly inhibited tumor growth following intratumoral injection, with virus replication, cell degeneration and necrosis in the tumor tissue. These results have important implications for the treatment of human lung cancer.

Indole-3-carbinol (I3C) increases apoptosis, represses growth of cancer cells, and enhances adenovirus-mediated oncolysis

Epidemiological studies suggest that high intake of cruciferous vegetables is associated with a lower risk of cancer. Experiments have shown that indole-3-carbinol (I3C), a naturally occurring compound derived from cruciferous vegetables, exhibits potent anticarcinogenic properties in a wide range of cancers. In this study, we showed that higher doses of I3C (≥400 μM) induced apoptotic cancer cell death and lower doses of I3C (≤200 μM) repressed cancer cell growth concurrently with suppressed expression of cyclin E and its partner CDK2. Notably, we found that pretreatment with low doses of I3C enhanced Ad-mediated oncolysis and cytotoxicity of human carcinoma cells by synergistic upregulation of apoptosis. Thus, the vegetable compound I3C as a dietary supplement may benefit cancer prevention and improve Ad oncolytic therapies.

The evolution of adenoviral vectors through genetic and chemical surface modifications

A long time has passed since the first clinical trial with adenoviral (Ad) vectors. Despite being very promising, Ad vectors soon revealed their limitations in human clinical trials. The pre-existing immunity, the marked liver tropism and the high toxicity of first generation Ad (FG-Ad) vectors have been the main challenges for the development of new approaches. Significant effort toward the development of genetically and chemically modified adenoviral vectors has enabled researchers to create more sophisticated vectors for gene therapy, with an improved safety profile and a higher transduction ability of different tissues. In this review, we will describe the latest findings in the high-speed, evolving field of genetic and chemical modifications of adenoviral vectors, a field in which different disciplines, such as biomaterial research, virology and immunology, co-operate synergistically to create better gene therapy tools for modern challenges.

A novel oncolytic viral therapy and imaging technique for gastric cancer using a genetically engineered vaccinia virus carrying the human sodium iodide symporter

Background

Gastric cancers have poor overall survival despite recent advancements in early detection methods, endoscopic resection techniques, and chemotherapy treatments. Vaccinia viral therapy has had promising therapeutic potential for various cancers and has a great safety profile. We investigated the therapeutic efficacy of a novel genetically-engineered vaccinia virus carrying the human sodium iodide symporter (hNIS) gene, GLV-1 h153, on gastric cancers and its potential utility for imaging with ^99mTc pertechnetate scintigraphy and ¹²⁴I positron emission tomography (PET).

Methods

GLV-1 h153 was tested against five human gastric cancer cell lines using cytotoxicity and standard viral plaque assays. In vivo, subcutaneous flank tumors were generated in nude mice with human gastric cancer cells, MKN-74. Tumors were subsequently injected with either GLV-1 h153 or PBS and followed for tumor growth. ^99mTc pertechnetate scintigraphy and ¹²⁴I microPET imaging were performed.

Results

GFP expression, a surrogate for viral infectivity, confirmed viral infection by 24 hours. At a multiplicity of infection (MOI) of 1, GLV-1 h153 achieved > 90% cytotoxicity in MNK-74, OCUM-2MD3, and AGS over 9 days, and >70% cytotoxicity in MNK- 45 and TMK-1. In vivo, GLV-1 h153 was effective in treating xenografts (p < 0.001) after 2 weeks of treatment. GLV-1 h153-infected tumors were readily imaged by ^99mTc pertechnetate scintigraphy and ¹²⁴I microPET imaging 2 days after treatment.

Conclusions

GLV-1 h153 is an effective oncolytic virus expressing the hNIS protein that can efficiently regress gastric tumors and allow deep-tissue imaging. These data encourages its continued investigation in clinical settings.

Adenovirus-Based Vectors for the Development of Prophylactic and Therapeutic Vaccines

Emerging and reemerging infectious diseases as well as cancer pose great global health impacts on the society. Vaccines have emerged as effective treatments to prevent or reduce the burdens of already developed diseases. This is achieved by means of activating various components of the immune system to generate systemic inflammatory reactions targeting infectious agents or diseased cells for control/elimination. DNA virus-based genetic vaccines gained significant attention in the past decades owing to the development of DNA manipulation technologies, which allowed engineering of recombinant viral vectors encoding sequences for foreign antigens or their immunogenic epitopes as well as various immunomodulatory molecules. Despite tremendous progress in the past 50 years, many hurdles still remain for achieving the full clinical potential of viral-vectored vaccines. This chapter will present the evolution of vaccines from “live” or “attenuated” first-generation agents to recombinant DNA and viral-vectored vaccines. Particular emphasis will be given to human adenovirus (Ad) for the development of prophylactic and therapeutic vaccines. Ad biological properties related to vaccine development will be highlighted along with their advantages and potential hurdles to be overcome. In particular, we will discuss (1) genetic modifications in the Ad capsid protein to reduce the intrinsic viral immunogenicity, (2) antigen capsid incorporation for effective presentation of foreign antigens to the immune system, (3) modification of the hexon and fiber capsid proteins for Ad liver de-targeting and selective retargeting to cancer cells, (4) Ad-based vaccines carrying “arming” transgenes with immunostimulatory functions as immune adjuvants, and (5) oncolytic Ad vectors as a new therapeutic approach against cancer. Finally, the combination of adenoviral vectors with other non-adenoviral vector systems, the prime/boost strategy of immunization, clinical trials involving Ad-based vaccines, and the perspectives for the field development will be discussed.

A novel armed oncolytic measles vaccine virus for the treatment of cholangiocarcinoma

Cholangiocarcinoma (CC) is curable only in early stages by complete surgical resection. Thus, in advanced disease stages in which a complete removal of the tumor mass is no longer possible and palliative chemotherapy achieves only modest success, therapeutics employing new methods of action are desperately needed. Oncolytic viruses employed in clinical studies have been shown to spread preferentially in cancer cells. Beyond that, virotherapeutic cell killing can be enhanced by virus-based expression of suicide genes. We engineered a measles vaccine virus (MeV) vector expressing super cytosine deaminase (SCD), a fusion protein of yeast cytosine deaminase and uracil phosphoribosyltransferase, which converts the prodrug 5-fluorocytosine (5-FC) to 5-fluorouracil (5-FU) and subsequently to 5-fluorouridine-monophosphate. This novel vector was evaluated using three different human-derived CC cell lines. In vitro, all CC cell lines were found to be permissive to MeV infection. Partial blocking of MeV-mediated oncolysis could be overcome by employment of the SCD transgene together with administration of 5-FC. In vivo, intratumoral application of SCD-armed MeV together with a systemic 5-FC treatment showed a significant reduction in tumor size in a TFK-1 xenograft mouse model when compared with virus-only treatment. In a second animal experiment employing a HuCCT1 xenograft tumor model, an enhanced SCD-armed MeV vector, in which the SCD transgene was expressed from a different genomic position, led not only to reduced tumor volumes, but also to a significant survival benefit. On the basis of these encouraging preclinical data on employment of SCD-armed MeV for the virotherapeutic treatment of chemotherapy-resistant CC, a clinical virotherapy trial is set up currently.

Increased Resistance of Breast, Prostate, and Embryonic Carcinoma Cells against Herpes Simplex Virus in Three-Dimensional Cultures

In previous studies we found that uveal melanoma cells grown in extracellular matrix (ECM)-containing three-dimensional (3D) cultures have increased resistance against herpes simplex virus type 1 (HSV-1)-mediated destruction relative to cells cultured without ECM. Using additional tumor cell types including MB-231 human breast cancer cells, PC-3 human prostate cancer cells, and P19 mouse embryonal carcinoma cells, we show here that tumor cell lines other than melanoma are also more resistant to HSV-1-mediated destruction in 3D cultures than cells grown in 2D. We also demonstrate here that one mechanism responsible for the increased resistance of tumor cells to HSV-1 infection in 3D cultures is an ECM-mediated inhibition of virus replication following virus entry into cells. These findings confirm and extend previous observations related to the role of the ECM in tumor resistance against HSV-1 and may lead to improved strategies of oncolytic virotherapy.

Virosome presents multimodel cancer therapy without viral replication

A virosome is an artificial envelope that includes viral surface proteins and lacks the ability to produce progeny virus. Virosomes are able to introduce an encapsulated macromolecule into the cytoplasm of cells using their viral envelope fusion ability. Moreover, virus-derived factors have an adjuvant effect for immune stimulation. Therefore, many virosomes have been utilized as drug delivery vectors and adjuvants for cancer therapy. This paper introduces the application of virosomes for cancer treatment. In Particular, we focus on virosomes derived from the influenza and Sendai viruses which have been widely used for cancer therapy. Influenza virosomes have been mainly applied as drug delivery vectors and adjuvants. By contrast, the Sendai virosomes have been mainly applied as anticancer immune activators and apoptosis inducers.

Highly efficient tumor transduction and antitumor efficacy in experimental human malignant mesothelioma using replicating gibbon ape leukemia virus

Retroviral replicating vectors (RRVs) have been shown to achieve efficient tumor transduction and enhanced therapeutic benefit in a wide variety of cancer models. Here we evaluated two different RRVs derived from amphotropic murine leukemia virus (AMLV) and gibbon ape leukemia virus (GALV), in human malignant mesothelioma cells. In vitro, both RRVs expressing the green fluorescent protein gene efficiently replicated in most mesothelioma cell lines tested, but not in normal mesothelial cells. Notably, in ACC-MESO-1 mesothelioma cells that were not permissive for AMLV-RRV, the GALV-RRV could spread efficiently in culture and in mice with subcutaneous xenografts by in vivo fluorescence imaging. Next, GALV-RRV expressing the cytosine deaminase prodrug activator gene showed efficient killing of ACC-MESO-1 cells in a prodrug 5-fluorocytosine dose-dependent manner, compared with AMLV-RRV. GALV-RRV-mediated prodrug activator gene therapy achieved significant inhibition of subcutaneous ACC-MESO-1 tumor growth in nude mice. Quantitative reverse transcription PCR demonstrated that ACC-MESO-1 cells express higher PiT-1 (GALV receptor) and lower PiT-2 (AMLV receptor) compared with normal mesothelial cells and other mesothelioma cells, presumably accounting for the distinctive finding that GALV-RRV replicates much more robustly than AMLV-RRV in these cells. These data indicate the potential utility of GALV-RRV-mediated prodrug activator gene therapy in the treatment of mesothelioma.