Liver cancer protease activity profiles support therapeutic options with matrix metalloproteinase-activatable oncolytic measles virus

Viral vectored vaccines: design, development, preventive and therapeutic applications in human diseases

Human diseases, particularly infectious diseases and cancers, pose unprecedented challenges to public health security and the global economy. The development and distribution of novel prophylactic and therapeutic vaccines are the prioritized countermeasures of human disease. Among all vaccine platforms, viral vector vaccines offer distinguished advantages and represent prominent choices for pathogens that have hampered control efforts based on conventional vaccine approaches. Currently, viral vector vaccines remain one of the best strategies for induction of robust humoral and cellular immunity against human diseases. Numerous viruses of different families and origins, including vesicular stomatitis virus, rabies virus, parainfluenza virus, measles virus, Newcastle disease virus, influenza virus, adenovirus and poxvirus, are deemed to be prominent viral vectors that differ in structural characteristics, design strategy, antigen presentation capability, immunogenicity and protective efficacy. This review summarized the overall profile of the design strategies, progress in advance and steps taken to address barriers to the deployment of these viral vector vaccines, simultaneously highlighting their potential for mucosal delivery, therapeutic application in cancer as well as other key aspects concerning the rational application of these viral vector vaccines. Appropriate and accurate technological advances in viral vector vaccines would consolidate their position as a leading approach to accelerate breakthroughs in novel vaccines and facilitate a rapid response to public health emergencies.

Repurposing live attenuated trivalent MMR vaccine as cost-effective cancer immunotherapy

It has long been known that oncolytic viruses wield their therapeutic capability by priming an inflammatory state within the tumor and activating the tumor immune microenvironment, resulting in a multifaceted antitumor immune response. Vaccine-derived viruses, such as measles and mumps, have demonstrated promising potential for treating human cancer in animal models and clinical trials. However, the extensive cost of manufacturing current oncolytic viral products makes them far out of reach for most patients. Here by analyzing the impact of intratumoral (IT) administrations of the trivalent live attenuated measles, mumps, and rubella viruses (MMR) vaccine, we unveil the cellular and molecular basis of MMR-induced anti-cancer activity. Strikingly, we found that IT delivery of low doses of MMR correlates with tumor control and improved survival in murine hepatocellular cancer and colorectal cancer models via increased tumor infiltration of CD8+ granzyme B+ T-cells and decreased macrophages. Moreover, our data indicate that MMR activates key cellular effectors of the host's innate and adaptive antitumor immunity, culminating in an immunologically coordinated cancer cell death. These findings warrant further work on the potential for MMR to be repurposed as safe and cost-effective cancer immunotherapy to impact cancer patients globally.

Transcriptome Analysis of Human Glioblastoma Cells Susceptible to Infection with the Leningrad-16 Vaccine Strain of Measles Virus

Glioblastoma multiforme (GBM) accounts for almost half of all primary malignant brain tumors in adults and has a poor prognosis. Here we demonstrated the oncolytic potential of the L-16 vaccine strain of measles virus (MV) against primary human GBM cells and characterized the genetic patterns that determine the sensitivity of primary human GBM cells to oncolytic therapy. MV replicated in all GBM cells, and seven out of eight cell lines underwent complete or partial oncolysis. RNA-Seq analysis identified about 1200 differentially expressed genes (FDR < 0.05) with at least two-fold expression level change between MV-infected and uninfected cells. Among them, the most significant upregulation was observed for interferon response, apoptosis and cytokine signaling. One out of eight GBM cell lines was defective in type I interferon production and, thus, in the post-interferon response, other cells lacked expression of different cellular defense factors. Thus, none of the cell lines displayed induction of the total gene set necessary for effective inhibition of MV replication. In the resistant cells, we detected aberrant expression of metalloproteinase genes, particularly MMP3. Thus, such genes could be considered intriguing candidates for further study of factors responsible for cell sensitivity and resistance to L-16 MV infection.

Measles Virus as an Oncolytic Immunotherapy

Measles virus (MeV) preferentially replicates in malignant cells, leading to tumor lysis and priming of antitumor immunity. Live attenuated MeV vaccine strains are therefore under investigation as cancer therapeutics. The versatile MeV reverse genetics systems allows for engineering of advanced targeted, armed, and shielded oncolytic viral vectors. Therapeutic efficacy can further be enhanced by combination treatments. An emerging focus in this regard is combination immunotherapy, especially with immune checkpoint blockade. Despite challenges arising from antiviral immunity, availability of preclinical models, and GMP production, early clinical trials have demonstrated safety of oncolytic MeV and yielded promising efficacy data. Future clinical trials with engineered viruses, rational combination regimens, and comprehensive translational research programs will realize the potential of oncolytic immunotherapy.

Engineering and combining oncolytic measles virus for cancer therapy

Cancer immunotherapy using tumor-selective, oncolytic viruses is an emerging therapeutic option for solid and hematologic malignancies. A considerable variety of viruses ranging from small picornaviruses to large poxviruses are currently being investigated as potential candidates. In the early days of virotherapy, non-engineered wild-type or vaccine-strain viruses were employed. However, these viruses often did not fully satisfy the major criteria of safety and efficacy. Since the advent of reverse genetics systems for manipulating various classes of viruses, the field has shifted to developing genetically engineered viruses with an improved therapeutic index. In this review, we will summarize the concepts and strategies of multi-level genetic engineering of oncolytic measles virus, a prime candidate for cancer immunovirotherapy. Furthermore, we will provide a brief overview of measles virus-based multimodal combination therapies for improved tumor control and clinical efficacy.

Measles virus in cancer therapy

Over the last years, the development of viruses to treat cancer patients has re-gained considerable attention. A genetically modified herpesvirus, Talimogene laherparepvec, has already been authorized for the treatment of melanoma patients. Also recombinant measles virus (MeV) is developed as an oncolytic virus. Because of its high genetic flexibility, a number of different MeV strains have been the basis for the generation of targeted, armed, or shielded viruses that are highly specific for a given tumor target, more effective, or protected against serum neutralization. Such MeV have been extensively tested in vitro and in vivo, whereby remarkable oncolytic potency is accompanied by safety also in non-human primates. Therefore, MeV has been introduced into 19 different clinical trials and has reached phase II against two different tumor entities, multiple myeloma and ovarian carcinoma. Remarkably, one patient with advanced stage myeloma experienced long-term remission after treatment, visualizing the potency of this approach.

Development of Entry-Targeted Oncolytic Measles Viruses

This chapter describes the development of recombinant oncolytic measles viruses (MeV) that selectively enter and destroy tumor cells. The envelope of MeV is a favorable targeting substrate because receptor attachment and membrane fusion functions are separated on two proteins: the hemagglutinin (H) that binds receptors, and the fusion (F) protein that fuses the viral envelope with the cell membrane. The cell entry process, which depends on receptor recognition and occurs at the plasma membrane at neutral pH, results in the delivery of encapsidated genomes to the cytoplasm, where they replicate. Towards improving cancer specificity of oncolytic MeV, two types of cell entry targeting have been achieved. First, entry has been redirected through cancer-specific cell surface proteins. This was done by displaying specificity domains on H while also ablating binding to its natural receptors. Second, activation of the F protein was made dependent on secreted cancer proteases, while also interfering with F cleavage/activation by a ubiquitous intracellular protease. This chapter describes how entry-targeted MeV are produced: In short, gene cassettes with modified H or F coding regions are generated, and then introduced into the viral genome available on plasmid DNA. Such full-length genome plasmids are transfected in cell lines expressing, stably or transiently, the three viral proteins necessary for genome replication. Infectious centers form among these "rescue" cells, which allow isolation of clonal recombinant viruses. These are amplified, characterized in vitro, and then evaluated for their oncolytic activity in appropriate preclinical animal models.

High-Affinity DARPin Allows Targeting of MeV to Glioblastoma Multiforme in Combination with Protease Targeting without Loss of Potency

Measles virus (MeV) is naturally cytolytic by extensive cell-to-cell fusion. Vaccine-derived MeV is toxic for cancer cells and is clinically tested as oncolytic virus. To combine the potential of MeV with enhanced safety, different targeting strategies have been described. We generated a receptor-targeted MeV by using receptor-blind viral attachment protein genetically fused to designed ankyrin repeat protein (DARPin) binding domains specific for the epidermal growth factor receptor (EGFR). To reduce on-target toxicity for EGFR⁺ healthy cells, we used an engineered viral fusion protein activatable by tumor-associated matrix metalloproteases (MMPs) for additional protease targeting. The dual-targeted virus replicated exclusively on EGFR⁺/MMP⁺ tumor cells but was safe on healthy EGFR⁺ target cells, primary human keratinocytes. Nevertheless, glioblastoma and other tumor cells were efficiently killed by all targeted viruses, although replication and oncolysis were slower for protease-targeted MeV. In vivo, efficacy of EGFR-targeted MeV was virtually unimpaired, whereas also dual-targeted MeV showed significant intra-tumoral spread and efficacy and could be armed with a prodrug convertase. The use of DARPin-domains resulted in potent EGFR-targeted MeV and for the first time effective dual retargeting of an oncolytic virus, further enhancing tumor selectivity. Together with powerful cell-toxic genes, the application as highly tumor-specific platform is promising.

Clinical Trials with Oncolytic Measles Virus: Current Status and Future Prospects

Attenuated Edmonston lineage measles virus (MV-Edm) vaccine strains can preferentially infect and lyse a wide variety of cancer cells. Oncolytic MV-Edm derivatives are genetically engineered to express the human carcinoembryonic antigen (MV-CEA virus) or the human sodium iodide symporter (MV-NIS virus) and are currently being tested in clinical trials against ovarian cancer, glioblastoma multiforme, multiple myeloma, mesothelioma, head and neck cancer, breast cancer and malignant peripheral nerve sheath tumors. This review describes the basic and preclinical data that facilitated the clinical translation of MV-Edm strains, and summarizes the clinical results of this oncolytic platform to date. Furthermore, we discuss the latest clinically relevant MV-Edm vector developments and creative strategies for future translational steps.

Physical, chemical, and synthetic virology: Reprogramming viruses as controllable nanodevices

The fields of physical, chemical, and synthetic virology work in partnership to reprogram viruses as controllable nanodevices. Physical virology provides the fundamental biophysical understanding of how virus capsids assemble, disassemble, display metastability, and assume various configurations. Chemical virology considers the virus capsid as a chemically addressable structure, providing chemical pathways to modify the capsid exterior, interior, and subunit interfaces. Synthetic virology takes an engineering approach, modifying the virus capsid through rational, combinatorial, and bioinformatics-driven design strategies. Advances in these three subfields of virology aim to develop virus-based materials and tools that can be applied to solve critical problems in biomedicine and biotechnology, including applications in gene therapy and drug delivery, diagnostics, and immunotherapy. Examples discussed include mammalian viruses, such as adeno-associated virus (AAV), plant viruses, such as cowpea mosaic virus (CPMV), and bacterial viruses, such as Qβ bacteriophage. Importantly, research efforts in physical, chemical, and synthetic virology have further unraveled the design principles foundational to the form and function of viruses. This article is categorized under: Diagnostic Tools > Diagnostic Nanodevices Biology-Inspired Nanomaterials > Protein and Virus-Based Structures.

Aeration and Shear Stress Are Critical Process Parameters for the Production of Oncolytic Measles Virus

Oncolytic Measles virus is a promising candidate for cancer treatment, but clinical studies have shown that extremely high doses (up to 1011 TCID50 per dose) are required to effect a cure. Very high titers of the virus must therefore be achieved during production to ensure an adequate supply. We have previously shown that Measles virus can be produced in Vero cells growing on a Cytodex 1 microcarrier in serum-containing medium using a stirred-tank reactor (STR). However, process optimization and further process transfer or scale up requires the identification of critical process parameters, particularly because the use of STRs increases the risk of cell damage and lower product yields due to shear stress. Using a small-scale STR (0.5 L working volume) we found that Measles virus titers are sensitive to agitator-dependent shear, with shear stress ≥0.25 N m-2 reducing the titer by more than four orders of magnitude. This effect was observed in both serum-containing and serum-free medium. At this scale, virus of titers up to 1010 TCID50 mL-1 could be achieved with an average shear stress of 0.1 N m-2. We also found that the aeration method affected the virus titer. Aeration was necessary to ensure a sufficient oxygen supply to the Vero cells, and CO2 was also needed to regulate the pH of the sodium bicarbonate buffer system. Continuous gassing with air and CO2 reduced the virus titer by four orders of magnitude compared to head-space aeration. The manufacture of oncolytic Measles virus in a STR can therefore be defined as a shear-sensitive process, but high titers can nevertheless be achieved by keeping shear stress levels below 0.25 N m-2 and by avoiding extensive gassing of the medium.

Virotherapy Research in Germany: From Engineering to Translation

Virotherapy is a unique modality for the treatment of cancer with oncolytic viruses (OVs) that selectively infect and lyse tumor cells, spread within tumors, and activate anti-tumor immunity. Various viruses are being developed as OVs preclinically and clinically, several of them engineered to encode therapeutic proteins for tumor-targeted gene therapy. Scientists and clinicians in German academia have made significant contributions to OV research and development, which are highlighted in this review paper. Innovative strategies for "shielding," entry or postentry targeting, and "arming" of OVs have been established, focusing on adenovirus, measles virus, parvovirus, and vaccinia virus platforms. Thereby, new-generation virotherapeutics have been derived. Moreover, immunotherapeutic properties of OVs and combination therapies with pharmacotherapy, radiotherapy, and especially immunotherapy have been investigated and optimized. German investigators are increasingly assessing their OV innovations in investigator-initiated and sponsored clinical trials. As a prototype, parvovirus has been tested as an OV from preclinical proof-of-concept up to first-in-human clinical studies. The approval of the first OV in the Western world, T-VEC (Imlygic), has further spurred the involvement of investigators in Germany in international multicenter studies. With the encouraging developments in funding, commercialization, and regulatory procedures, more German engineering will be translated into OV clinical trials in the near future.

Immunomodulation in hepatocellular cancer

Hepatocellular carcinoma (HCC) is the fastest growing malignancy in the United States in relation to mortality. HCC relies on a complex immunosuppressive network to modify the host immune system and evade destruction. Intrinsic to the liver's function and anatomy, native hepatic and immune cells produce many inhibitory cytokines that promote tolerogenicity and limit immune response. Since the introduction of sorafenib in 2008, no treatment has been able to demonstrate improved survival in patients with advanced HCC post disease progression treated with sorafenib. More recent studies have shown that sorafenib has an immunomodulatory function in addition to inhibition of multiple tyrosine kinases. Clinical trials have aimed to further enhance this immunomodulatory function with other treatments, most promisingly immune checkpoint inhibitors. Additionally, ongoing studies are using combinatorial approaches with immunomodulatory treatment and liver directed therapies such as transarterial chemoembolization (TACE), radiofrequency ablation (RFA), microwave ablation (MWA), and cryoablation. This article will review recent data describing the immunosuppressive network in HCC, recent results of immunotherapies, and combinatorial approaches to treat advanced HCC.

Potential and clinical translation of oncolytic measles viruses

INTRODUCTION

Oncolytic viruses represent a novel treatment modality that is unencumbered by the standard resistance mechanisms limiting the therapeutic efficacy of conventional antineoplastic agents. Attenuated engineered measles virus strains derived from the Edmonston vaccine lineage have undergone extensive preclinical evaluation with significant antitumor activity observed in a broad range of preclinical tumoral models. These have laid the foundation for several clinical trials in both solid and hematologic malignancies, which have demonstrated safety, biologic activity and the ability to elicit antitumor immune responses. Areas covered: This review examines the published preclinical data which supported the clinical translation of this therapeutic platform, reviews the available clinical trial data and expands on ongoing phase II testing. It also looks at approaches to optimize clinical applicability and offers future perspectives. Expert opinion: Reverse genetic engineering has allowed the generation of oncolytic MV strains retargeted to increase viral tumor specificity, or armed with therapeutic and immunomodulatory genes in order to enhance anti-tumor efficacy. Continuous efforts focusing on exploring methods to overcome resistance pathways and determining optimal combinatorial strategies will facilitate further development of this encouraging antitumor strategy.

Measles to the Rescue: A Review of Oncolytic Measles Virus

Oncolytic virotherapeutic agents are likely to become serious contenders in cancer treatment. The vaccine strain of measles virus is an agent with an impressive range of oncolytic activity in pre-clinical trials with increasing evidence of safety and efficacy in early clinical trials. This paramyxovirus vaccine has a proven safety record and is amenable to careful genetic modification in the laboratory. Overexpression of the measles virus (MV) receptor CD46 in many tumour cells may direct the virus to preferentially enter transformed cells and there is increasing awareness of the importance of nectin-4 and signaling lymphocytic activation molecule (SLAM) in oncolysis. Successful attempts to retarget MV by inserting genes for tumour-specific ligands to antigens such as carcinoembryonic antigen (CEA), CD20, CD38, and by engineering the virus to express synthetic microRNA targeting sequences, and "blinding" the virus to the natural viral receptors are exciting measures to increase viral specificity and enhance the oncolytic effect. Sodium iodine symporter (NIS) can also be expressed by MV, which enables in vivo tracking of MV infection. Radiovirotherapy using MV-NIS, chemo-virotherapy to convert prodrugs to their toxic metabolites, and immune-virotherapy including incorporating antibodies against immune checkpoint inhibitors can also increase the oncolytic potential. Anti-viral host immune responses are a recognized barrier to the success of MV, and approaches such as transporting MV to the tumour sites by carrier cells, are showing promise. MV Clinical trials are producing encouraging preliminary results in ovarian cancer, myeloma and cutaneous non-Hodgkin lymphoma, and the outcome of currently open trials in glioblastoma multiforme, mesothelioma and squamous cell carcinoma are eagerly anticipated.

Proteases in cancer drug delivery

Whereas protease inhibitors have been developed successfully against hypertension and viral infections, they have failed thus far as cancer drugs. With advances in cancer profiling we now better understand that the tumor "degradome" (i.e. the repertoire of proteases and their natural inhibitors and interaction partners) forms a complex network in which specific nodes determine the global outcome of manipulation of the protease web. However, knowing which proteases are active in the tumor micro-environment, we may tackle cancers with the use of Protease-Activated Prodrugs (PAPs). Here we exemplify this concept for metallo-, cysteine and serine proteases. PAPs not only exist as small molecular adducts, containing a cleavable substrate sequence and a latent prodrug, they are presently also manufactured as various types of nanoparticles. Although the emphasis of this review is on PAPs for treatment, it is clear that protease activatable probes and nanoparticles are also powerful tools for imaging purposes, including tumor diagnosis and staging, as well as visualization of tumor imaging during microsurgical resections.

Protein engineering: a new frontier for biological therapeutics

Protein engineering holds the potential to transform the metabolic drug landscape through the development of smart, stimulusresponsive drug systems. Protein therapeutics are a rapidly expanding segment of Food and Drug Administration approved drugs that will improve clinical outcomes over the long run. Engineering of protein therapeutics is still in its infancy, but recent general advances in protein engineering capabilities are being leveraged to yield improved control over both pharmacokinetics and pharmacodynamics. Stimulus- responsive protein therapeutics are drugs which have been designed to be metabolized under targeted conditions. Protein engineering is being utilized to develop tailored smart therapeutics with biochemical logic. This review focuses on applications of targeted drug neutralization, stimulus-responsive engineered protein prodrugs, and emerging multicomponent smart drug systems (e.g., antibody-drug conjugates, responsive engineered zymogens, prospective biochemical logic smart drug systems, drug buffers, and network medicine applications).

Oncolysis by paramyxoviruses: multiple mechanisms contribute to therapeutic efficiency

Oncolytic paramyxoviruses include some strains of Measles, Mumps, Newcastle disease, and Sendai viruses. All these viruses are well equipped for promoting highly specific and efficient malignant cell death, which can be direct and/or immuno-mediated. A number of proteins that serve as natural receptors for oncolytic paramyxoviruses are frequently overexpressed in malignant cells. Therefore, the preferential interaction of paramyxoviruses with malignant cells rather than with normal cells is promoted. Due to specific genetic defects of cancer cells in the interferon (IFN) and apoptotic pathways, viral replication has the potential to be promoted specifically in tumors. Viral mediation of syncytium formation (a polykaryonic structure) promotes intratumoral paramyxo-virus replication and spreading, without exposure to host neutralizing antibodies. So, two related processes: efficient intratumoral infection spread as well as the consequent mass malignant cell death, both are enhanced. In general, the paramyxoviruses elicit strong anticancer innate and adaptive immune responses by triggering multiple danger signals. The paramyxoviruses are powerful inducers of IFN and other immuno-stimulating cytokines. These viruses efficiently promote anticancer activity of natural killer cells, dendritic cells, and cytotoxic T lymphocytes. Moreover, a neuraminidase (sialidase), a component of the viral envelope of Newcastle Disease, Mumps, and Sendai viruses, can cleave sialic acids on the surface of malignant cells thereby unmasking cancer antigens and exposing them to the immune system. These multiple mechanisms contribute to therapeutic efficacy of oncolytic paramyxovi-ruses and are responsible for encouraging results in preclinical and clinical studies.

Improved in vitro human tumor models for cancer gene therapy

Developing effective anticancer treatments is a particular challenge, as agents must contend with not only the target cellular biology, but also with the complex tumor microenvironment. Here we discuss various in vitro strategies that have sought to address this issue, with a particular focus on new methodologies that utilize clinical samples in basic research and their application in gene therapy and virotherapy.

Pseudogene CYP4Z2P 3'UTR promotes angiogenesis in breast cancer

Pseudogenes have long been marked as "false" genes, which are similar with real genes but have no apparent function. The 3'UTR is well-known to regulate gene expression post-transcriptionally. Our recent evidence, however, indicates novel functional roles of pseudogene CYP4Z2P 3'UTR (Z2P-UTR). We found that ectopic expression of Z2P-UTR in breast cancer cells significantly increased the expression of VEGF-A without affecting cell proliferation in vitro. Meanwhile, conditioned medium (CM) from Z2P-UTR overexpression cells enhanced proliferation, migration and tube formation of HUVEC, and promoted angiogenesis in ex vivo models. Also, CM increased the expression of VEGFR2 in HUVEC. Our data suggest that Z2P-UTR can promote breast cancer angiogenesis partly via paracrine pathway of VEGF-A/VEGFR2.

MicroRNA-mediated multi-tissue detargeting of oncolytic measles virus

Precise oncotropism is required for successful systemic administration of next-generation oncolytic measles viruses (MVs). We have previously established a system for efficient post-entry targeting by insertion of synthetic microRNA target sites (miRTS) into the MV genome, thereby repressing replication in the presence of cognate microRNAs. Thus, differential expression of microRNAs, as frequently observed in normal compared with malignant tissues, can be exploited to increase vector specificity and safety. Here we report the combination of miRTS for different microRNAs in a single vector to detarget pivotal organs at risk during systemic administration (liver, brain, gastrointestinal tract). Accordingly, miRTS for miR-122, miR-7 and miR-148a that are enriched in these tissues were inserted to create multi-tissue-detargeted MV (MV-EGFP(mtd)). Replication of MV-EGFP(mtd) is repressed in cell lines as well as in non-transformed primary human hepatocytes and liver slices expressing cognate microRNAs. Oncolytic potency of MV-EGFP(mtd) is retained in a model of pancreatic cancer in vitro and in vivo. This work is a proof-of-concept that favorable expression profiles of multiple microRNAs can be exploited concomitantly to reshape the tropism of MV without compromising oncolytic efficacy. This strategy can be adapted to different vectors and cancer entities for safe and efficient high-dose systemic administration in clinical trials.

Oncolytic activity of avian influenza virus in human pancreatic ductal adenocarcinoma cell lines

Pancreatic ductal adenocarcinoma (PDA) is the most lethal form of human cancer, with dismal survival rates due to late-stage diagnoses and a lack of efficacious therapies. Building on the observation that avian influenza A viruses (IAVs) have a tropism for the pancreas in vivo, the present study was aimed at testing the efficacy of IAVs as oncolytic agents for killing human PDA cell lines. Receptor characterization confirmed that human PDA cell lines express the alpha-2,3- and the alpha-2,6-linked glycan receptor for avian and human IAVs, respectively. PDA cell lines were sensitive to infection by human and avian IAV isolates, which is consistent with this finding. Growth kinetic experiments showed preferential virus replication in PDA cells over that in a nontransformed pancreatic ductal cell line. Finally, at early time points posttreatment, infection with IAVs caused higher levels of apoptosis in PDA cells than gemcitabine and cisplatin, which are the cornerstone of current therapies for PDA. In the BxPC-3 PDA cell line, apoptosis resulted from the engagement of the intrinsic mitochondrial pathway. Importantly, IAVs did not induce apoptosis in nontransformed pancreatic ductal HPDE6 cells. Using a model based on the growth of a PDA cell line as a xenograft in SCID mice, we also show that a slightly pathogenic avian IAV significantly inhibited tumor growth following intratumoral injection. Taken together, these results are the first to suggest that IAVs may hold promise as future agents of oncolytic virotherapy against pancreatic ductal adenocarcinomas.

IMPORTANCE

Despite intensive studies aimed at designing new therapeutic approaches, PDA still retains the most dismal prognosis among human cancers. In the present study, we provide the first evidence indicating that avian IAVs of low pathogenicity display a tropism for human PDA cells, resulting in viral RNA replication and a potent induction of apoptosis in vitro and antitumor effects in vivo. These results suggest that slightly pathogenic IAVs may prove to be effective for oncolytic virotherapy of PDA and provide grounds for further studies to develop specific and targeted viruses, with the aim of testing their efficacy in clinical contexts.

Viral oncolysis - can insights from measles be transferred to canine distemper virus?

Neoplastic diseases represent one of the most common causes of death among humans and animals. Currently available and applied therapeutic options often remain insufficient and unsatisfactory, therefore new and innovative strategies and approaches are highly needed. Periodically, oncolytic viruses have been in the center of interest since the first anecdotal description of their potential usefulness as an anti-tumor treatment concept. Though first reports referred to an incidental measles virus infection causing tumor regression in a patient suffering from lymphoma several decades ago, no final treatment concept has been developed since then. However, numerous viruses, such as herpes-, adeno- and paramyxoviruses, have been investigated, characterized, and modified with the aim to generate a new anti-cancer treatment option. Among the different viruses, measles virus still represents a highly interesting candidate for such an approach. Numerous different tumors of humans including malignant lymphoma, lung and colorectal adenocarcinoma, mesothelioma, and ovarian cancer, have been studied in vitro and in vivo as potential targets. Moreover, several concepts using different virus preparations are now in clinical trials in humans and may proceed to a new treatment option. Surprisingly, only few studies have investigated viral oncolysis in veterinary medicine. The close relationship between measles virus (MV) and canine distemper virus (CDV), both are morbilliviruses, and the fact that numerous tumors in dogs exhibit similarities to their human counterpart, indicates that both the virus and species dog represent a highly interesting translational model for future research in viral oncolysis. Several recent studies support such an assumption. It is therefore the aim of the present communication to outline the mechanisms of morbillivirus-mediated oncolysis and to stimulate further research in this potentially expanding field of viral oncolysis in a highly suitable translational animal model for the benefit of humans and dogs.

53BP1 is a novel regulator of angiogenesis in breast cancer

In our previous study, we found that 53BP1 was a tumor suppressor and was associated with prognosis in breast cancer. However, little is known about its role in angiogenesis. In the present study, we aimed to reveal the role of 53BP1 in angiogenesis of breast cancer. With RNA interference and ectopic expression strategies to elucidate the detailed function of 53BP1 in angiogenesis, we observed that ectopic expression of 53BP1 inhibited cellular angiogenesis and 53BP1 RNA interference led to an increase in angiogenesis both in vitro and in vivo. In clinical breast cancer samples, 53BP1 was inversely correlated with CD31, MMP-2 and MMP-9 by immunohistochemistry analysis. Furthermore, we showed that the Akt pathway was involved in the antiangiogenesis function of 53BP1. Overall, our findings demonstrate that 53BP1 plays a vital role in inhibiting angiogenesis. These findings suggest that 53BP1 might provide a viable target therapy for breast cancer.

DARPin-targeting of measles virus: unique bispecificity, effective oncolysis, and enhanced safety

Oncolytic virotherapy is an emerging treatment modality that uses replication-competent viruses to destroy cancers. Many naturally occurring viruses have a preferential, although nonexclusive, tropism for tumors and tumor cells. In addition, specific targeting of cancer cells can be achieved at the virus entry level. We optimized retargeting of cell entry by elongating the measles virus attachment protein with designed ankyrin repeat proteins (DARPins), while simultaneously ablating entry through the natural receptors. DARPin-targeted viruses were strongly attenuated in off-target tissue, thereby enhancing safety, but completely eliminated tumor xenografts. Taking advantage of the unique properties of DARPins of being fused without generating folding problems, we generated a virus simultaneous targeting two different tumor markers. The bispecific virus retained the original oncolytic efficacy, while providing proof of concept for a strategy to counteract issues of resistance development. Thus, DARPin-targeting opens new prospects for the development of personalized, targeted therapeutics.

Oncolytic measles virus strains as novel anticancer agents

INTRODUCTION

Replication-competent oncolytic measles virus (MV) strains preferentially infect and destroy a wide variety of cancer tissues. Clinical translation of engineered attenuated MV vaccine derivatives is demonstrating the therapeutic potential and negligible pathogenicity of these strains in humans.

AREAS COVERED

The present review summarizes the mechanisms of MV tumor selectivity and cytopathic activity as well as the current data on the oncolytic efficacy and preclinical testing of MV strains. Investigational strategies to reprogram MV selectivity, escape antiviral immunity and modulate the immune system to enhance viral delivery and tumor oncolysis are also discussed.

EXPERT OPINION

Clinical viral kinetic data derived from noninvasive monitoring of reporter transgene expression will guide future protocols to enhance oncolytic MV efficacy. Anti-measles immunity is a major challenge of measles-based therapeutics and various strategies are being investigated to modulate immunity. These include the combination of MV therapy with immunosuppressive drugs, such as cyclophosphamide, the use of cell carriers and the introduction of immunomodulatory transgenes and wild-type virulence genes. Available MV retargeting technologies can address safety considerations that may arise as more potent oncolytic MV vectors are being developed.

Testin is a tumor suppressor and prognostic marker in breast cancer

The testin (TES) gene was previously identified in the fragile chromosomal region FRA7G at 7q31.2. In the present study, we aimed to investigate the candidate tumor suppressor function of TES and explore its correlations to clinicopathologic features and prognosis in breast cancer. In clinical samples, we showed that the expression of TES decreased gradually from normal through ductal hyperplasia without atypia, atypical ductal hyperplasia, and ductal carcinoma in situ, to invasive ductal carcinoma. To explore the possible tumor suppressing function of TES, the expression of TES in breast cancer cells was manipulated by ectopic expression or by RNAi. We revealed that ectopic TES expression significantly inhibited cell proliferation, invasive ability, and angiogenesis, whereas knockdown of TES by RNAi enhanced cell proliferation, invasive ability, and angiogenesis. In an animal model, TES markedly inhibited breast cancer cell xenograft formation in athymic nude mice and reduced breast cancer cell metastasis to lung. Moreover, we revealed that TES inhibited the invasion and angiogenesis of breast cancer partially through miR-29b-mediated MMP-2 inhibition. Using the tissue microarray of breast cancer from Yale University, we found that lower TES expression was an independent prognostic factor for shorter overall survival and disease-free survival with univariate and multivariate analyses. Taken together, these data suggest that TES, as a valuable marker of breast cancer prognosis, plays an important role in the development and progression of breast cancer. TES may be an effective novel target in breast cancer prevention and treatment.

Targeted lentiviral vectors pseudotyped with the Tupaia paramyxovirus glycoproteins

Lentiviral vectors are vectors of choice for many gene therapy applications. Recently, efficient targeting of lentiviral vectors pseudotyped with the Measles virus (MV) glycoproteins has been reported. However, MV antibodies in patients might limit the clinical use of these vectors. We demonstrate here that lentiviral vectors can also be pseudotyped with the glycoproteins of Tupaia paramyxovirus (TPMV), the hemagglutinin (H) and fusion (F) protein. As this animal paramyxovirus has no known close relatives in humans, we do not expect TPMV antibodies in patients. Because TPMV normally does not infect human cells, 'detargeting' from natural receptors is unnecessary. Similar to the MV system, TPMV glycoproteins can mediate targeted cell entry by displaying different single-chain antibodies (scAb) directed against surface molecules on target cells on the viral hemagglutinin. We generated a panel of H and F proteins with truncated cytoplasmic tails and determined the variants that efficiently pseudotyped lentiviral vectors. The B-cell marker CD20 was used as a model antigen, and CD20-targeted TPMV vectors selectively transduced CD20-positive cells, including quiescent primary human B-cells. Lentiviral vectors pseudotyped with targeted TPMV envelope proteins might be a valuable vector choice when systemic application of targeted lentiviral vectors in humans is required.

MicroRNA-29b suppresses tumor angiogenesis, invasion, and metastasis by regulating matrix metalloproteinase 2 expression

Hepatocellular carcinoma (HCC) is a highly vascularized tumor with frequent intrahepatic metastasis. Active angiogenesis and metastasis are responsible for rapid recurrence and poor survival of HCC. We previously found that microRNA-29b (miR-29b) down-regulation was significantly associated with poor recurrence-free survival of HCC patients. Therefore, the role of miR-29b in tumor angiogenesis, invasion, and metastasis was further investigated in this study using in vitro capillary tube formation and transwell assays, in vivo subcutaneous and orthotopic xenograft mouse models, and Matrigel plug assay, and human HCC samples. Both gain- and loss-of-function studies showed that miR-29b dramatically suppressed the ability of HCC cells to promote capillary tube formation of endothelial cells and to invade extracellular matrix gel in vitro. Using mouse models, we revealed that tumors derived from miR-29b-expressed HCC cells displayed significant reduction in microvessel density and in intrahepatic metastatic capacity compared with those from the control group. Subsequent investigations revealed that matrix metalloproteinase-2 (MMP-2) was a direct target of miR-29b. The blocking of MMP-2 by neutralizing antibody or RNA interference phenocopied the antiangiogenesis and antiinvasion effects of miR-29b, whereas introduction of MMP-2 antagonized the function of miR-29b. We further disclosed that miR-29b exerted its antiangiogenesis function, at least partly, by suppressing MMP-2 expression in tumor cells and, in turn, impairing vascular endothelial growth factor receptor 2-signaling in endothelial cells. Consistently, in human HCC tissues and mouse xenograft tumors miR-29b level was inversely correlated with MMP-2 expression, as well as tumor angiogenesis, venous invasion, and metastasis.

CONCLUSION

miR-29b deregulation contributes to angiogenesis, invasion, and metastasis of HCC. Restoration of miR-29b represents a promising new strategy in anti-HCC therapy.

Recent advances in oncolytic virus design

The cytolytic properties of viruses can be used to treat cancer. Replication of certain viruses is favoured in cancer cells, whereas others can be modified to obtain tumour specificity. This approach has evolved to become a new discipline called virotherapy. In addition, these replication-competent (oncolytic) viruses can be adapted as vectors for cancer gene therapy. The "armed" viruses show a double mechanism of action: direct destruction of cancer cells as a consequence of the lytic viral cycle, in combination with the effect of the therapeutic gene incorporated in the viral genome. Current trends in the field include strategies to increase the oncolytic potency of existing viruses; the evaluation of new candidates; the search for synergistic effects between different viruses and conventional therapies; and a rational approach to take advantage of the interplay between the viruses and the host immune system. This review summarises the most relevant achievements in recent years.