A phase I study of a tropism-modified conditionally replicative adenovirus for recurrent malignant gynecologic diseases

Cancer therapy with the viral and bacterial pathogens: The past enemies can be considered the present allies

Cancer continues to be one of the leading causes of mortality worldwide despite significant advancements in cancer treatment. Many difficulties have arisen as a result of the detrimental consequences of chemotherapy and radiotherapy as a common cancer therapy, such as drug inability to penetrate deep tumor tissue, and also the drug resistance in tumor cells continues to be a major concern. These obstacles have increased the need for the development of new techniques that are more selective and effective against cancer cells. Bacterial-based therapies and the use of oncolytic viruses can suppress cancer in comparison to other cancer medications. The tumor microenvironment is susceptible to bacterial accumulation and proliferation, which can trigger immune responses against the tumor. Oncolytic viruses (OVs) have also gained considerable attention in recent years because of their potential capability to selectively target and induce apoptosis in cancer cells. This review aims to provide a comprehensive summary of the latest literature on the role of bacteria and viruses in cancer treatment, discusses the limitations and challenges, outlines various strategies, summarizes recent preclinical and clinical trials, and emphasizes the importance of optimizing current strategies for better clinical outcomes.

Anticancer Activity of Measles-Mumps-Rubella MMR Vaccine Viruses against Glioblastoma

BACKGROUND

Oncolytic viruses (OVs) have been utilized since 1990s for targeted cancer treatment. Our study examined the Measles-Mumps-Rubella (MMR) vaccine's cancer-killing potency against Glioblastoma (GBM), a therapy-resistant, aggressive cancer type.

METHODOLOGY

We used GBM cell lines, primary GBM cells, and normal mice microglial cells, to assess the MMR vaccine's efficacy through cell viability, cell cycle analysis, intracellular viral load via RT-PCR, and Transmission Electron Microscopy (TEM).

RESULTS

After 72 h of MMR treatment, GBM cell lines and primary GBM cells exhibited significant viability reduction compared to untreated cells. Conversely, normal microglial cells showed only minor changes in viability and morphology. Intracellular viral load tests indicated GBM cells' increased sensitivity to MMR viruses compared to normal cells. The cell cycle study also revealed measles and mumps viruses' crucial role in cytopathic effects, with the rubella virus causing cell cycle arrest.

CONCLUSION

Herein the reported results demonstrate the anti-cancer activity of the MMR vaccine against GBM cells. Accordingly, the MMR vaccine warrants further study as a potential new tool for GBM therapy and relapse prevention. Therapeutic potential of the MMR vaccine has been found to be promising in earlier studies as well.

Developing Oncolytic Viruses for the Treatment of Cervical Cancer

Cervical cancer represents one of the most important malignancies among women worldwide. Current therapeutic approaches for cervical cancer are reported not only to be inadequate for metastatic cervical cancer, but are also considered as cytotoxic for several patients leading to serious side effects, which can have negative implications on the quality of life of women. Therefore, there is an urgent need for the development of innovative and effective treatment options. Oncolytic viruses can eventually become effective biological agents, since they preferentially infect and kill cancer cells, while leaving the normal tissue unaffected. Moreover, they are also able to leverage the host immune system response to limit tumor growth. This review aims to systematically describe and discuss the different types of oncolytic viruses generated for targeting cervical cancer cells, as well as the outcome of the combination of virotherapy with conventional therapies. Although many preclinical studies have evaluated the therapeutic efficacy of oncolytic viruses in cervical cancer, the number of clinical trials so far is limited, while their oncolytic properties are currently being tested in clinical trials for the treatment of other malignancies.

Development and application of oncolytic viruses as the nemesis of tumor cells

Viruses and tumors are two pathologies that negatively impact human health, but what occurs when a virus encounters a tumor? A global consensus among cancer patients suggests that surgical resection, chemotherapy, radiotherapy, and other methods are the primary means to combat cancer. However, with the innovation and development of biomedical technology, tumor biotherapy (immunotherapy, molecular targeted therapy, gene therapy, oncolytic virus therapy, etc.) has emerged as an alternative treatment for malignant tumors. Oncolytic viruses possess numerous anti-tumor properties, such as directly lysing tumor cells, activating anti-tumor immune responses, and improving the tumor microenvironment. Compared to traditional immunotherapy, oncolytic virus therapy offers advantages including high killing efficiency, precise targeting, and minimal side effects. Although oncolytic virus (OV) therapy was introduced as a novel approach to tumor treatment in the 19th century, its efficacy was suboptimal, limiting its widespread application. However, since the U.S. Food and Drug Administration (FDA) approved the first OV therapy drug, T-VEC, in 2015, interest in OV has grown significantly. In recent years, oncolytic virus therapy has shown increasingly promising application prospects and has become a major research focus in the field of cancer treatment. This article reviews the development, classification, and research progress of oncolytic viruses, as well as their mechanisms of action, therapeutic methods, and routes of administration.

The Challenges and Prospects of p53-Based Therapies in Ovarian Cancer

It has been well established that mutations in the tumor suppressor gene, p53, occur readily in a vast majority of cancer tumors, including ovarian cancer. Typically diagnosed in stages three or four, ovarian cancer is the fifth leading cause of death in women, despite accounting for only 2.5% of all female malignancies. The overall 5-year survival rate for ovarian cancer is around 47%; however, this drops to an abysmal 29% for the most common type of ovarian cancer, high-grade serous ovarian carcinoma (HGSOC). HGSOC has upwards of 96% of cases expressing mutations in p53. Therefore, wild-type (WT) p53 and p53-based therapies have been explored as treatment options via a plethora of drug delivery vehicles including nanoparticles, viruses, polymers, and liposomes. However, previous p53 therapeutics have faced many challenges, which have resulted in their limited translational success to date. This review highlights a selection of these historical p53-targeted therapeutics for ovarian cancer, why they failed, and what the future could hold for a new generation of this class of therapies.

Oncolytic Viruses and Cancer Immunotherapy

PURPOSE OF REVIEW

Oncolytic viruses (OVs) exert their antitumor effect through selective killing of cancer cells and induction of host anti-tumor immunity. This review aims to summarize the recent and current trials with OVs for the treatment of lung cancer.

RECENT FINDINGS

Several OVs have been developed for the treatment of lung cancer including adenovirus, coxsackievirus B3, reovirus, and vaccinia virus and trials have demonstrated a safe toxicity profile. Early-phase trials in lung cancer with OVs have reported antiviral immune responses and evidence of clinical benefit. However, clinical efficacy of OVs in lung cancer either as monotherapy or in combination with chemotherapy has not been confirmed in larger phase II or III trials. Development of OVs in lung cancer has been limited by difficulty in administering OVs in the tumor directly as well as achieving adequate viral load at all tumor sites with systemically administered OVs. Developing novel combinations with OVs, especially checkpoint inhibitors and other immunotherapeutics, may be a strategy to address the limited success seen thus far. Integrating appropriate biomarker studies and meaningful endpoints in future clinical trials will be imperative. Using novel viral delivery systems in addition to increasing tumor specificity through improved genetic modifications in the OVs are other strategies to improve efficacy.

Cutting-Edge Developments in Oncology Research

The field of oncology research has made many successful advances, and new discoveries have started making headlines. As an example, the identification of immune checkpoint inhibition mechanisms in carcinogenic cells led to the development of immunoassays, which have helped many cancer convalescents recover. This article covers the most advanced cutting-edge areas of cancer research: exosomes, microbiomes, immunotherapy, nanocarriers, and organoids. Research on exosomes advances cancer detection and treatment modalities, as well as further understanding of mechanisms that regulate carcinogen cell division, proliferation, invasion, and metastasis. Microbiome consents the researchers to understand the disease cancer. Immunotherapy is the third method in the treatment of cancer. Organoid biology will be further expanded with the aim of translating research into customized therapeutic therapies. Nanocarriers enable cancer specific drug delivery by inherent unreceptive targeting phenomena and implemented active targeting strategies. These areas of research may also bring about the advent of the latest cancer treatments in the future. Malignant infections are one of the leading grounds for demise in the society. Patients are treated with surgery, radiation, and chemotherapy. In chemotherapy, the malignant cells are destroyed and the tumor burden is reduced. However, in most cases, resistance to chemotherapy develops. Therefore, there is a constant need for new additional treatment modalities and chemotherapeutic complex rules. Due to the rapid development in cancer research, I can only mention a few goals and treatment options that I have chosen; However, this review specializes in new and admirable significant strategies and compounds.

Therapeutic Efficacy of Oncolytic Viruses in Fighting Cancer: Recent Advances and Perspective

Immunotherapy is at the cutting edge of modern cancer treatment. Innovative medicines have been developed with varying degrees of success that target all aspects of tumor biology: tumors, niches, and the immune system. Oncolytic viruses (OVs) are a novel and potentially immunotherapeutic approach for cancer treatment. OVs reproduce exclusively in cancer cells, causing the tumor mass to lyse. OVs can also activate the immune system in addition to their primary activity. Tumors create an immunosuppressive environment by suppressing the immune system’s ability to respond to tumor cells. By injecting OVs into the tumor, the immune system is stimulated, allowing it to generate a robust and long-lasting response against the tumor. The essential biological properties of oncolytic viruses, as well as the underlying mechanisms that enable their usage as prospective anticancer medicines, are outlined in this review. We also discuss the increased efficacy of virotherapy when combined with other cancer medications.

Oncolytic virus therapy in cancer: A current review

In view of the advancement in the understanding about the most diverse types of cancer and consequently a relentless search for a cure and increased survival rates of cancer patients, finding a therapy that is able to combat the mechanism of aggression of this disease is extremely important. Thus, oncolytic viruses (OVs) have demonstrated great benefits in the treatment of cancer because it mediates antitumor effects in several ways. Viruses can be used to infect cancer cells, especially over normal cells, to present tumor-associated antigens, to activate "danger signals" that generate a less immune-tolerant tumor microenvironment, and to serve transduction vehicles for expression of inflammatory and immunomodulatory cytokines. The success of therapies using OVs was initially demonstrated by the use of the genetically modified herpes virus, talimogene laherparepvec, for the treatment of melanoma. At this time, several OVs are being studied as a potential treatment for cancer in clinical trials. However, it is necessary to be aware of the safety and possible adverse effects of this therapy; after all, an effective treatment for cancer should promote regression, attack the tumor, and in the meantime induce minimal systemic repercussions. In this manuscript, we will present a current review of the mechanism of action of OVs, main clinical uses, updates, and future perspectives on this treatment.

Integrating Cancer Vaccines in the Standard-of-Care of Ovarian Cancer: Translating Preclinical Models to Human

Simple Summary

The overall survival of ovarian cancer (OC) remains poor for most patients. Despite incorporation of novel therapeutic agents such as bevacizumab and PARP inhibitors to OC standard-of-care, efficacy is only observed in a subset of patients. Cancer vaccination has demonstrated effectiveness in OC patients and could be considered for potential incorporation into OC standard-of-care. This review provides an overview of the different types of cancer vaccination strategies and discusses the use of murine OC tumor models to evaluate combinatorial regimens comprising cancer vaccines and OC standard-of-care.

Abstract

As the majority of ovarian cancer (OC) patients are diagnosed with metastatic disease, less than 40% will survive past 5 years after diagnosis. OC is characterized by a succession of remissions and recurrences. The most promising time point for immunotherapeutic interventions in OC is following debulking surgery. Accumulating evidence shows that T cells are important in OC; thus, cancer vaccines capable of eliciting antitumor T cells will be effective in OC treatment. In this review, we discuss different cancer vaccines and propose strategies for their incorporation into the OC standard-of-care regimens. Using the murine ID8 ovarian tumor model, we provide evidence that a cancer vaccine can be effectively combined with OC standard-of-care to achieve greater overall efficacy. We demonstrate several important similarities between the ID8 model and OC patients, in terms of response to immunotherapies, and the ID8 model can be an important tool for evaluating combinatorial regimens and clinical trial designs in OC. Other emerging models, including patient-derived xenograft and genetically engineered mouse models, are continuing to improve and can be useful for evaluating cancer vaccination therapies in the near future. Here, we provide a comprehensive review of the completed and current clinical trials evaluating cancer vaccines in OC.

Is more better? An analysis of toxicity and response outcomes from dose-finding clinical trials in cancer

BACKGROUND

The overwhelming majority of dose-escalation clinical trials use methods that seek a maximum tolerable dose, including rule-based methods like the 3+3, and model-based methods like CRM and EWOC. These methods assume that the incidences of efficacy and toxicity always increase as dose is increased. This assumption is widely accepted with cytotoxic therapies. In recent decades, however, the search for novel cancer treatments has broadened, increasingly focusing on inhibitors and antibodies. The rationale that higher doses are always associated with superior efficacy is less clear for these types of therapies.

METHODS

We extracted dose-level efficacy and toxicity outcomes from 115 manuscripts reporting dose-finding clinical trials in cancer between 2008 and 2014. We analysed the outcomes from each manuscript using flexible non-linear regression models to investigate the evidence supporting the monotonic efficacy and toxicity assumptions.

RESULTS

We found that the monotonic toxicity assumption was well-supported across most treatment classes and disease areas. In contrast, we found very little evidence supporting the monotonic efficacy assumption.

CONCLUSIONS

Our conclusion is that dose-escalation trials routinely use methods whose assumptions are violated by the outcomes observed. As a consequence, dose-finding trials risk recommending unjustifiably high doses that may be harmful to patients. We recommend that trialists consider experimental designs that allow toxicity and efficacy outcomes to jointly determine the doses given to patients and recommended for further study.

Genetic and Chemical Capsid Modifications of Adenovirus Vectors to Modulate Vector-Host Interactions

Adenovirus-based vectors are playing an important role as efficacious genetic vaccines to fight the current COVID-19 pandemic. Furthermore, they have an enormous potential as oncolytic vectors for virotherapy and as vectors for classic gene therapy. However, numerous vector-host interactions on a cellular and noncellular level, including specific components of the immune system, must be modulated in order to generate safe and efficacious vectors for virotherapy or classic gene therapy. Importantly, the current widespread use of Ad vectors as vaccines against COVID-19 will induce antivector immunity in many humans. This requires the development of strategies and techniques to enable Ad-based vectors to evade pre-existing immunity. In this review article, we discuss the current status of genetic and chemical capsid modifications as means to modulate the vector-host interactions of Ad-based vectors.

Teratogenic Toxicity Evaluation of Bladder Cancer-Specific Oncolytic Adenovirus on Mice

BACKGROUND

In our previous studies, we had demonstrated the efficiency and specificity of constructed bladder tissue-specific adenovirus Ad-PSCAE-UPII-E1A-AR (APU-EIA-AR) on bladder cancer. The virus biodistribution and body toxicity in nude mice have also been investigated. However, the safety of the bladder cancer-specific oncolytic adenovirus on fetal mice and F1 mice should be under intense investigation.

OBJECTIVE

In order to evaluate the teratogenic toxicity of bladder cancer-specific oncolytic adenovirus APU-EIA-AR on mice, in this study, we investigated the fetal mice weight, fetal body length and tail length, fetal skeleton development, as well as the F1 mice weight, growth curve, and major organ pathology. These teratogenic toxicity data of bladder tissue-specific adenovirus Ad-PSCAE- UPII-E1A-AR (AD) would provide safe information prior to embarking on clinical trials.

METHODS

On the sixth day of being fertilized, the pregnant mice began to be intramuscularly administrated with AD (1×10⁷VP, 1×10⁸VP, 1×10⁹VP) every other day for ten days. The pregnant mice were then divided into two groups. One group was euthanized on the seventeenth day; the fetal mice were taken out, and the bone structure of the infants was observed. The other group was observed until natural childbirth. The Filial Generation (F1) is fed for 30 days; the variations in the growth progress and development were assessed. The mice were then euthanized; The tissues from major organs were harvested and observed under the microscope.

RESULTS

In the process of teratogenic toxicity test, the Placenta weight, fetal mice weight, body length, and a tail length of mice fetal in adenovirus treated group did not reveal any alteration. Meanwhile, comparing with the PBS group, there is no obvious change in the skeleton of fetal mice treated with adenovirus. During the development process of F1 mice treated with adenovirus, the changes in mice weight show statistical significance. However, in the progress of the growth curve, this difference is not very obvious. Furthermore, the pathological section showed no obvious alteration in major organs.

CONCLUSION

Our study demonstrated that bladder cancer-specific adenovirus Ad-PSCAE-UPII- E1A-AR appears safe in pregnant mice without any discernable effects on fetal mice and F1 development. Hence, it is relatively safe for tumor gene therapy.

Oncolytic Virotherapy in Solid Tumors: The Challenges and Achievements

Oncolytic virotherapy (OVT) is a promising approach in cancer immunotherapy. Oncolytic viruses (OVs) could be applied in cancer immunotherapy without in-depth knowledge of tumor antigens. The capability of genetic modification makes OVs exciting therapeutic tools with a high potential for manipulation. Improving efficacy, employing immunostimulatory elements, changing the immunosuppressive tumor microenvironment (TME) to inflammatory TME, optimizing their delivery system, and increasing the safety are the main areas of OVs manipulations. Recently, the reciprocal interaction of OVs and TME has become a hot topic for investigators to enhance the efficacy of OVT with less off-target adverse events. Current investigations suggest that the main application of OVT is to provoke the antitumor immune response in the TME, which synergize the effects of other immunotherapies such as immune-checkpoint blockers and adoptive cell therapy. In this review, we focused on the effects of OVs on the TME and antitumor immune responses. Furthermore, OVT challenges, including its moderate efficiency, safety concerns, and delivery strategies, along with recent achievements to overcome challenges, are thoroughly discussed.

Delta-24-RGD, an Oncolytic Adenovirus, Increases Survival and Promotes Proinflammatory Immune Landscape Remodeling in Models of AT/RT and CNS-PNET

PURPOSE

Atypical teratoid/rhabdoid tumors (AT/RT) and central nervous system primitive neuroectodermal tumors (CNS-PNET) are pediatric brain tumors with poor survival and life-long negative side effects. Here, the aim was to characterize the efficacy and safety of the oncolytic adenovirus, Delta-24-RGD, which selectively replicates in and kills tumor cells.

EXPERIMENTAL DESIGN

Delta-24-RGD determinants for infection and replication were evaluated in patient expression datasets. Viral replication and cytotoxicity were assessed in vitro in a battery of CNS-PNET and AT/RT cell lines. In vivo, efficacy was determined in different orthotopic mouse models, including early and established tumor models, a disseminated AT/RT lesion model, and immunocompetent humanized mouse models (hCD34⁺-NSG-SGM3).

RESULTS

Delta-24-RGD infected and replicated efficiently in all the cell lines tested. In addition, the virus induced dose-dependent cytotoxicity [IC₅₀ value below 1 plaque-forming unit (PFU)/cell] and the release of immunogenic markers. In vivo, a single intratumoral Delta-24-RGD injection (10⁷ or 10⁸ PFU) significantly increased survival and led to long-term survival in AT/RT and PNET models. Delta-24-RGD hindered the dissemination of AT/RTs and increased survival, leading to 70% of long-term survivors. Of relevance, viral administration to established tumor masses (30 days after engraftment) showed therapeutic benefit. In humanized immunocompetent models, Delta-24-RGD significantly extended the survival of mice bearing AT/RTs or PNETs (ranging from 11 to 27 days) and did not display any toxicity associated with inflammation. Immunophenotyping of Delta-24-RGD-treated tumors revealed increased CD8⁺ T-cell infiltration.

CONCLUSIONS

Delta-24-RGD is a feasible therapeutic option for AT/RTs and CNS-PNETs. This work constitutes the basis for potential translation to the clinical setting.

Considerations for setting occupational exposure limits for novel pharmaceutical modalities

In order to develop new and effective medicines, pharmaceutical companies must be modality agnostic. As science reveals an enhanced understanding of biological processes, new therapeutic modalities are becoming important in developing breakthrough therapies to treat both rare and common diseases. As these new modalities progress, concern and uncertainty arise regarding their safe handling by the researchers developing them, employees manufacturing them and nurses administering them. This manuscript reviews the available literature for emerging modalities (including oligonucleotides, monoclonal antibodies, fusion proteins and bispecific antibodies, antibody-drug conjugates, peptides, vaccines, genetically modified organisms, and several others) and provides considerations for occupational health and safety-oriented hazard identification and risk assessments to enable timely, consistent and well-informed hazard identification, hazard communication and risk-management decisions. This manuscript also points out instances where historical exposure control banding systems may not be applicable (e.g. oncolytic viruses, biologics) and where other occupational exposure limit systems are more applicable (e.g. Biosafety Levels, Biologic Control Categories).

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Review of toxicology and pharmacology information for novel therapeutic modalities.

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Identification of occupational hazards associated with novel therapeutic modalities.

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Occupational hazards and exposure risks differ across pharmaceutical modalities.

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Occupational exposure control banding systems are not one size fits all.

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Banding system variations offer benefits while enabling proper exposure controls.

Clinical Application of Oncolytic Viruses: A Systematic Review

Leveraging the immune system to thwart cancer is not a novel strategy and has been explored via cancer vaccines and use of immunomodulators like interferons. However, it was not until the introduction of immune checkpoint inhibitors that we realized the true potential of immunotherapy in combating cancer. Oncolytic viruses are one such immunotherapeutic tool that is currently being explored in cancer therapeutics. We present the most comprehensive systematic review of all oncolytic viruses in Phase 1, 2, and 3 clinical trials published to date. We performed a systematic review of all published clinical trials indexed in PubMed that utilized oncolytic viruses. Trials were reviewed for type of oncolytic virus used, method of administration, study design, disease type, primary outcome, and relevant adverse effects. A total of 120 trials were found; 86 trials were available for our review. Included were 60 phase I trials, five phase I/II combination trials, 19 phase II trials, and two phase III clinical trials. Oncolytic viruses are feverously being evaluated in oncology with over 30 different types of oncolytic viruses being explored either as a single agent or in combination with other antitumor agents. To date, only one oncolytic virus therapy has received an FDA approval but advances in bioengineering techniques and our understanding of immunomodulation to heighten oncolytic virus replication and improve tumor kill raises optimism for its future drug development.

Understanding and addressing barriers to successful adenovirus-based virotherapy for ovarian cancer

Ovarian cancer is the leading cause of death among women with gynecological cancer, with an overall 5-year survival rate below 50% due to a lack of specific symptoms, late stage at time of diagnosis and a high rate of recurrence after standard therapy. A better understanding of heterogeneity, genetic mutations, biological behavior and immunosuppression in the tumor microenvironment have allowed the development of more effective therapies based on anti-angiogenic treatments, PARP and immune checkpoint inhibitors, adoptive cell therapies and oncolytic vectors. Oncolytic adenoviruses are commonly used platforms in cancer gene therapy that selectively replicate in tumor cells and at the same time are able to stimulate the immune system. In addition, they can be genetically modified to enhance their potency and overcome physical and immunological barriers. In this review we highlight the challenges of adenovirus-based oncolytic therapies targeting ovarian cancer and outline recent advances to improve their potential in combination with immunotherapies.

Determinants of the efficacy of viro-immunotherapy: A review

Oncolytic virus immunotherapy is rapidly gaining interest in the field of immunotherapy against cancer. The minimal toxicity upon treatment and the dual activity of direct oncolysis and immune activation make therapy with oncolytic viruses (OVs) an interesting treatment modality. The safety and efficacy of several OVs have been assessed in clinical trials and, so far, the Food and Drug Administration (FDA) has approved one OV. Unfortunately, most treatments with OVs have shown suboptimal responses in clinical trials, while they appeared more promising in preclinical studies, with tumours reducing after immune cell influx. In several clinical trials with OVs, parameters such as virus replication, virus-specific antibodies, systemic immune responses, immune cell influx into tumours and tumour-specific antibodies have been studied as predictors or correlates of therapy efficacy. In this review, these studies are summarized to improve our understanding of the determinants of the efficacy of OV therapies in humans and to provide insights for future developments in the viro-immunotherapy treatment field.

Tumor Targeting by αvβ3-Integrin-Specific Lipid Nanoparticles Occurs via Phagocyte Hitchhiking

Although the first nanomedicine was clinically approved more than two decades ago, nanoparticles' (NP) in vivo behavior is complex and the immune system's role in their application remains elusive. At present, only passive-targeting nanoformulations have been clinically approved, while more complicated active-targeting strategies typically fail to advance from the early clinical phase stage. This absence of clinical translation is, among others, due to the very limited understanding for in vivo targeting mechanisms. Dynamic in vivo phenomena such as NPs' real-time targeting kinetics and phagocytes' contribution to active NP targeting remain largely unexplored. To better understand in vivo targeting, monitoring NP accumulation and distribution at complementary levels of spatial and temporal resolution is imperative. Here, we integrate in vivo positron emission tomography/computed tomography imaging with intravital microscopy and flow cytometric analyses to study α_vβ₃-integrin-targeted cyclic arginine-glycine-aspartate decorated liposomes and oil-in-water nanoemulsions in tumor mouse models. We observed that ligand-mediated accumulation in cancerous lesions is multifaceted and identified "NP hitchhiking" with phagocytes to contribute considerably to this intricate process. We anticipate that this understanding can facilitate rational improvement of nanomedicine applications and that immune cell-NP interactions can be harnessed to develop clinically viable nanomedicine-based immunotherapies.

Oncolytic viruses: what to expect from their use in cancer treatment

Oncolytic viruses are biologic agents able to selectively infect and destroy cancer cells while sparing the normal ones. Furthermore, they also stimulate the host immune system to combat the tumor growth and to promote tumor removal. This review thoroughly describes different types of viruses developed for targeting specific cancers, as well as the strategies to improve the efficacy and safety of oncolytic virotherapy. It also explores how their potential as anticancer agents may be enhanced through combination with other traditional therapies, such as chemotherapy or more recent approaches, such as checkpoint inhibitors. There are many oncolytic viruses currently being tested in clinical trials for the treatment of various types of cancer, suggesting that this approach could become the near future of the oncology field.

Delivery and Biosafety of Oncolytic Virotherapy

In recent years, oncolytic virotherapy has emerged as a promising anticancer therapy. Oncolytic viruses destroy cancer cells, without damaging normal tissues, through virus self-replication and antitumor immunity responses, showing great potential for cancer treatment. However, the clinical guidelines for administering oncolytic virotherapy remain unclear. Delivery routes for oncolytic virotherapy to patients vary in existing studies, depending on the tumor sites and the objective of studies. Moreover, the biosafety of oncolytic virotherapy, including mainly uncontrolled adverse events and long-term complications, remains a serious concern that needs to be accurately measured. This review provides a comprehensive and detailed overview of the delivery and biosafety of oncolytic virotherapy.

Defining a murine ovarian cancer model for the evaluation of conditionally-replicative adenovirus (CRAd) virotherapy agents

BACKGROUND

Virotherapy represents a promising approach for ovarian cancer. In this regard, conditionally replicative adenovirus (CRAd) has been translated to the context of human clinical trials. Advanced design of CRAds has sought to exploit their capacity to induce anti-tumor immunization by configuring immunoregulatory molecule within the CRAd genome. Unfortunately, employed murine xenograft models do not allow full analysis of the immunologic activity linked to CRAd replication.

RESULTS

We developed CRAds based on the Ad5/3-Delta24 design encoding cytokines. Whereas the encoded cytokines did not impact adversely CRAd-induced oncolysis in vitro, no gain in anti-tumor activity was noted in immune-incompetent murine models with human ovarian cancer xenografts. On this basis, we explored the potential utility of the murine syngeneic immunocompetent ID8 ovarian cancer model. Of note, the ID8 murine ovarian cancer cell lines exhibited CRAd-mediated cytolysis. The use of this model now enables the rational design of oncolytic agents to achieve anti-tumor immunotherapy.

CONCLUSIONS

Limits of widely employed murine xenograft models of ovarian cancer limit their utility for design and study of armed CRAd virotherapy agents. The ID8 model exhibited CRAd-induced oncolysis. This feature predicate its potential utility for the study of CRAd-based virotherapy agents.

A Phase 1 Trial of Oncolytic Adenovirus ICOVIR-5 Administered Intravenously to Cutaneous and Uveal Melanoma Patients

Oncolytic viruses represent a unique type of agents that combine self-amplification, lytic, and immunostimulatory properties against tumors. A local and locoregional clinical benefit has been demonstrated upon intratumoral injections of an oncolytic herpes virus in melanoma patients, leading to its approval in the United States and Europe for patients without visceral disease (up to stage IVM1a). However, in order to debulk and change the local immunosuppressive environment of tumors that cannot be injected directly, oncolyitc viruses need to be administered systemically. Among different viruses, adenovirus has been extensively used in clinical trials but with few evidences of activity upon systemic administration. Preclinical efficacy of a single intravenous administration of our oncolytic adenovirus ICOVIR5, an adenovirus type 5 responsive to the retinoblastoma pathway commonly deregulated in tumors, led us to use this virus in a dose-escalation phase 1 trial in metastatic melanoma patients. The results in 12 patients treated with a single infusion of a dose up to 1 × 10¹³ viral particles show that ICOVIR5 can reach melanoma metastases upon a single intravenous administration but fails to induce tumor regressions. These results support the systemic administration of armed oncolytic viruses to treat disseminated cancer.

The role of JNK phosphorylation as a molecular target to enhance adenovirus replication, oncolysis and cancer therapeutic efficacy

Oncolytic adenoviruses (Ads) are cancer selective tumoricidal agents; however their mechanism of Ad-mediated cancer cell lysis, or oncolysis, remains undefined. This report focuses upon the autophagy mediator c-JUN n-terminal kinase (JNK) and its effects upon Ad oncolysis and replication. Previously, E1b-deleted Ads have been used to treat several hundred cancer patients with limited clinical efficacy. We hypothesize that by studying the potential interactions between E1b and JNK, mechanisms to improve oncolytic Ad design and cancer therapeutic efficacy may be elucidated. To test this hypothesis, E1b was selectively deleted from the Ad genome. These studies indicated that Ads encoding E1b induced JNK phosphorylation predominately occurred via E1b-19K. The expression of another crucial Ad gene E1a was then overexpressed by the CMV promoter via the replication competent Ad vector Adhz69; these data indicated that E1A also induced JNK phosphorylation. To assess the effects of host cell JNK expression upon Ad oncolysis and replication, siRNA targeting JNK1 and JNK2 (JNK1/2) were utilized. The oncolysis and replication of the E1b-19K wild-type Ads Ad5 and Adhz63 were significantly attenuated following JNK1/2 siRNA transfection. However the oncolytic effects and replication of the E1b-19K deleted Ad Adhz60 were not altered by JNK1/2 siRNA transfection, further implicating the crucial role of E1b-19K for Ad oncolysis and replication via JNK phosphorylation. This study has demonstrated for the first time that JNK is an intriguing molecular marker associated with enhanced Ad virotherapy efficacy, influencing future Ad vector design.

Recent Progress in Gene Therapy for Ovarian Cancer

Ovarian cancer is the most lethal gynecological malignancy in developed countries. This is due to the lack of specific symptoms that hinder early diagnosis and to the high relapse rate after treatment with radical surgery and chemotherapy. Hence, novel therapeutic modalities to improve clinical outcomes in ovarian malignancy are needed. Progress in gene therapy has allowed the development of several strategies against ovarian cancer. Most are focused on the design of improved vectors to enhance gene delivery on the one hand, and, on the other hand, on the development of new therapeutic tools based on the restoration or destruction of a deregulated gene, the use of suicide genes, genetic immunopotentiation, the inhibition of tumour angiogenesis, the alteration of pharmacological resistance, and oncolytic virotherapy. In the present manuscript, we review the recent advances made in gene therapy for ovarian cancer, highlighting the latest clinical trials experience, the current challenges and future perspectives.

Oncolytic virus immunotherapies in ovarian cancer: moving beyond adenoviruses

Ovarian cancer is the 5th most common cancer in UK women with a high relapse rate. The overall survival for ovarian cancer has remained low for decades prompting a real need for new therapies. Recurrent ovarian cancer remains confined in the peritoneal cavity in >80% of the patients, providing an opportunity for locoregional administration of novel therapeutics, including gene and viral therapy approaches. Immunotherapy is an expanding field, and includes oncolytic viruses as well as monoclonal antibodies, immune checkpoint inhibitors, and therapeutic vaccines. Oncolytic viruses cause direct cancer cell cytolysis and immunogenic cell death and subsequent release of tumor antigens that will prime for a potent tumor-specific immunity. This effect may be further enhanced when the viruses are engineered to express, or coadministered with, immunostimulatory molecules. Currently, the most commonly used and well-characterized vectors utilized for virotherapy purposes are adenoviruses. They have been shown to work synergistically with traditional chemotherapy and radiotherapy and have met with success in clinical trials. However, pre-existing immunity and poor in vivo models limit our ability to fully investigate the potential of oncolytic adenovirus as effective immunotherapies which in turn fosters the need to develop alternative viral vectors. In this review we cover recent advances in adenovirus-based oncolytic therapies targeting ovarian cancer and recent advances in mapping immune responses to oncolytic virus therapies in ovarian cancer.

Combing oncolytic adenovirus expressing Beclin-1 with chemotherapy agent doxorubicin synergistically enhances cytotoxicity in human CML cells in vitro

Cancer virotherapy provides a new strategy to treat cancer that can directly kill cancer cells by oncolysis. Insertion of therapeutic genes into the genome of a modified adenovirus, thereby creating a so-called gene-virotherapy that shares the advantages of gene therapy and virotherapy. In this study we investigated whether a strategy that combines the oncolytic effects of an adenoviral vector with the simultaneous expression of the autophagy gene Beclin-1 offered a therapeutic advantage for chronic myeloid leukemia (CML) cells with resistance to chemotherapy and evaluated the synergistic effects of SG511-BECN and doxorubicin (Dox) in human CML cells in vitro. Oncolytic virus SG511-BECN was constructed through introducing the Beclin-1 gene into the oncolytic adenoviral backbone. SG511-BECN displayed significantly improved antileukemia activity on multidrug-resistant CML cell line K562/A02, which was mediated via induction of autophagic cell death. Furthermore, Dox could synergize with SG511-BECN to kill the CML cells by improving the infectious efficiency of the oncolytic adenovirus without causing significant damage to normal human mononuclear cells. The results demonstrate that targeting the autophagic cell death pathway and combination of a chemotherapy agent with oncolytic adenovirus may be a novel strategy for the treatment of leukemia with chemotherapy resistance.

The E1B19K-deleted oncolytic adenovirus mutant AdΔ19K sensitizes pancreatic cancer cells to drug-induced DNA-damage by down-regulating Claspin and Mre11

Adenovirus-mediated sensitization of cancer cells to cytotoxic drugs depends on simultaneous interactions of early viral genes with cell death and survival pathways. It is unclear what cellular factors mediate these interactions in the presence of DNA-damaging drugs. We found that adenovirus prevents Chk1-mediated checkpoint activation through inactivation of Mre11 and downregulation of the pChk1 adaptor-protein, Claspin, in cells with high levels of DNA-damage induced by the cytotoxic drugs gemcitabine and irinotecan. The mechanisms for Claspin downregulation involve decreased transcription and increased degradation, further attenuating pChk1-mediated signalling. Live cell imaging demonstrated that low doses of gemcitabine caused multiple mitotic aberrations including multipolar spindles, micro- and multi-nucleation and cytokinesis failure. A mutant virus with the anti-apoptotic E1B19K-gene deleted (AdΔ19K) further enhanced cell killing, Claspin downregulation, and potentiated drug-induced DNA damage and mitotic aberrations. Decreased Claspin expression and inactivation of Mre11 contributed to the enhanced cell killing in combination with DNA-damaging drugs. These results reveal novel mechanisms that are utilised by adenovirus to ensure completion of its life cycle in the presence of cellular DNA damage. Taken together, our findings reveal novel cellular targets that may be exploited when developing improved anti-cancer therapeutics.

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.

Oncolytic Adenovirus-Loaded Menstrual Blood Stem Cells Overcome the Blockade of Viral Activity Exerted by Ovarian Cancer Ascites

Patients with ovarian cancer present peritoneal ascites at recurrence as a marker of disseminated disease and dismal prognosis. Oncolytic immunotherapy is an emerging approach for the treatment of disseminated cancer. In the present work, we constructed a novel oncolytic adenovirus, AR2011, to target malignant ovarian tumors. AR2011 exhibited a clear lytic effect in vitro in human ovarian cancer cell lines and malignant cells obtained from ascitic fluids (AFs) of patients with ovarian cancer. AR2011 activity was neutralized by antibodies present in 31 samples of patient-derived AFs. However, this blockade was overridden by preloading menstrual blood stem cells (MenSCs) with AR2011 (MenSC-AR), since AFs exerted no in vitro inhibitory effect on viral lytic activity under these conditions. Moreover, soluble factors present in AFs act as MenSC chemoattractants. MenSC-AR treatment of nude mice carrying established peritoneal carcinomatosis following administration of human ovarian cancer cells was able to inhibit tumor growth at levels similar to those observed with AR2011 alone. This study demonstrates that MenSCs can be used to override the blockade that AFs exert on viral oncolytic effects.

A Comparative Study of Replication-Incompetent and -Competent Adenoviral Therapy-Mediated Immune Response in a Murine Glioma Model

Oncolytic virotherapy is a treatment approach with increasing clinical relevance, as indicated by the marked survival benefit seen in animal models and its current exploration in human patients with cancer. The use of an adenovirus vector for this therapeutic modality is common, has significant clinical benefit in animals, and its efficacy has recently been linked to an anti-tumor immune response that occurs following tumor antigen presentation. Here, we analyzed the adaptive immune system's response following viral infection by comparing replication-incompetent and replication-competent adenoviral vectors. Our findings suggest that cell death caused by replication-competent adenoviral vectors is required to induce a significant anti-tumor immune response and survival benefits in immunocompetent mice bearing intracranial glioma. We observed significant changes in the repertoire of immune cells in the brain and draining lymph nodes and significant recruitment of CD103+ dendritic cells (DCs) in response to oncolytic adenoviral therapy, suggesting the active role of the immune system in anti-tumor response. Our data suggest that the response to oncolytic virotherapy is accompanied by local and systemic immune responses and should be taken in consideration in the future design of the clinical studies evaluating oncolytic virotherapy in patients with glioblastoma multiforme (GBM).

Oncolytic adenoviruses as a therapeutic approach for osteosarcoma: A new hope

Osteosarcoma is the most common bone cancer among those with non-hematological origin and affects mainly pediatric patients. In the last 50 years, refinements in surgical procedures, as well as the introduction of aggressive neoadjuvant and adjuvant chemotherapeutic cocktails, have increased to nearly 70% the survival rate of these patients. Despite the initial therapeutic progress the fight against osteosarcoma has not substantially improved during the last three decades, and almost 30% of the patients do not respond or recur after the standard treatment. For this group there is an urgent need to implement new therapeutic approaches. Oncolytic adenoviruses are conditionally replicative viruses engineered to selectively replicate in and kill tumor cells, while remaining quiescent in healthy cells. In the last years there have been multiple preclinical and clinical studies using these viruses as therapeutic agents in the treatment of a broad range of cancers, including osteosarcoma. In this review, we summarize some of the most relevant published literature about the use of oncolytic adenoviruses to treat human osteosarcoma tumors in subcutaneous, orthotopic and metastatic mouse models. In conclusion, up to date the preclinical studies with oncolytic adenoviruses have demonstrated that are safe and efficacious against local and metastatic osteosarcoma. Knowledge arising from phase I/II clinical trials with oncolytic adenoviruses in other tumors have shown the potential of viruses to awake the patient´s own immune system generating a response against the tumor. Generating osteosarcoma immune-competent adenoviruses friendly models will allow to better understand this potential. Future clinical trials with oncolytic adenoviruses for osteosarcoma tumors are warranted.

IL-12 Expressing oncolytic herpes simplex virus promotes anti-tumor activity and immunologic control of metastatic ovarian cancer in mice

Background

Despite advances in surgical aggressiveness and conventional chemotherapy, ovarian cancer remains the most lethal cause of gynecologic cancer mortality; consequently there is a need for new therapeutic agents and innovative treatment paradigms for the treatment of ovarian cancer. Several studies have demonstrated that ovarian cancer is an immunogenic disease and immunotherapy represents a promising and novel approach that has not been completely evaluated in ovarian cancer. Our objective was to evaluate the anti-tumor activity of an oncolytic herpes simplex virus “armed” with murine interleukin-12 and its ability to elicit tumor-specific immune responses. We evaluated the ability of interleukin−12-expressing and control oncolytic herpes simplex virus to kill murine and human ovarian cancer cell lines in vitro. We also administered interleukin−12-expressing oncolytic herpes simplex virus to the peritoneal cavity of mice that had developed spontaneous, metastatic ovarian cancer and determined overall survival and tumor burden at 95 days. We used flow cytometry to quantify the tumor antigen-specific CD8⁺ T cell response in the omentum and peritoneal cavity.

Results

All ovarian cancer cell lines demonstrated susceptibility to oncolytic herpes simplex virus in vitro. Compared to controls, mice treated with interleukin−12-expressing oncolytic herpes simplex virus demonstrated a more robust tumor antigen-specific CD8⁺ T-cell immune response in the omentum (471.6 cells vs 33.1 cells; p = 0.02) and peritoneal cavity (962.3 cells vs 179.5 cells; p = 0.05). Compared to controls, mice treated with interleukin−12-expressing oncolytic herpes simplex virus were more likely to control ovarian cancer metastases (81.2 % vs 18.2 %; p = 0.008) and had a significantly longer overall survival (p = 0.02). Finally, five of 6 mice treated with interleukin−12-expressing oHSV had no evidence of metastatic tumor when euthanized at 6 months, compared to two of 4 mice treated with sterile phosphate buffer solution.

Conclusion

Our pilot study demonstrates that an interleukin−12-expressing oncolytic herpes simplex virus effectively kills both murine and human ovarian cancer cell lines and promotes tumor antigen-specific CD8⁺ T-cell responses in the peritoneal cavity and omentum, leading to reduced peritoneal metastasis and improved survival in a mouse model.

Combinatorial strategies based on CRAd-IL24 and CRAd-ING4 virotherapy with anti-angiogenesis treatment for ovarian cancer

Background

A major hurdle incurrent to the human clinical application of conditionally replicative adenovirus (CRAd)-based virotherapy agents is their limited therapeutic efficacy. In this study we evaluated whether arming our previously reported Ad5/3Δ24 CRAd vector containing a 24-base pair deletion in the E1A conserved region 2, which allows selective replication within Rb-p16-deficient tumor cells, to express therapeutic genes could improve oncolytic virus potency in ovarian cancer cells. We choose to assess the therapeutic benefits achieved by virus-mediated expression of interleukin 24 (IL-24), a cytokine-like protein of the IL-10 family, and the inhibitor of growth 4 (ING4) tumor suppressor protein.

Results

The generated CRAd-IL24 and CRAd-ING4 vectors were tested in ovarian cancer cell lines in vitro to compare their replication, yield, and cytotoxic effects with control CRAd Ad5/3∆24 lacking the therapeutic gene. These studies showed that CRAd-IL24 infection resulted in significantly increased yield of infectious particles, which translated to a marked enhancement of virus-induced cytotoxic effects as compared to CRAd-ING4 and non-armed CRAd. Testing CRAd-IL24 and CRAd-ING4 vectors combined together did not revealed synergistic effects exceeding oncolytic potency of single CRAD-IL24 vector. Both CRAds were also tested along with anti-VEGF monoclonal antibody Avastin and showed no significant augmentation of viral cytolysis by anti-angiogenesis treatment in vitro.

Conclusions

Our studies validated that arming with these key immunomodulatory genes was not deleterious to virus-mediated oncolysis. These findings thus, warrant further preclinical studies of CRAd-IL24 tumoricidal efficacy in murine ovarian cancer models to establish its potential utility for the virotherapy of primary and advanced neoplastic diseases.

Oncolytic viruses: From bench to bedside with a focus on safety

Oncolytic viruses are a relatively new class of anti-cancer immunotherapy agents. Several viruses have undergone evaluation in clinical trials in the last decades, and the first agent is about to be approved to be used as a novel cancer therapy modality. In the current review, an overview is presented on recent (pre)clinical developments in the field of oncolytic viruses that have previously been or currently are being evaluated in clinical trials. Special attention is given to possible safety issues like toxicity, environmental shedding, mutation and reversion to wildtype virus.

Leveraging immunotherapy for the treatment of gynecologic cancers in the era of precision medicine

During the past decade significant progress in the understanding of stimulatory and inhibitory signaling pathways in immune cells has reinvigorated the field of immuno-oncology. In this review we outline the current immunotherapy based approaches for the treatment of gynecological cancers, and focus on the emerging clinical data on immune checkpoint inhibitors, adoptive cell therapies, and vaccines. It is anticipated that in the coming years biomarker-guided clinical trials, will provide for a better understanding of the mechanisms of response and resistance to immunotherapy, and guide combination treatment strategies that will extend the benefit from immunotherapy to patients with gynecologic cancers.

Oncolytic adenoviruses targeted to Human Papilloma Virus-positive head and neck squamous cell carcinomas

OBJECTIVES

In recent years, the incidence of Human Papilloma Virus (HPV)-positive head and neck squamous cell carcinomas (HNSCC) has markedly increased. Our aim was to design a novel therapeutic agent through the use of conditionally replicative adenoviruses (CRAds) that are targeted to the HPV E6 and E7 oncoproteins.

METHODS

Each adenovirus included small deletion(s) in the E1a region of the genome (Δ24 or CB016) intended to allow for selective replication in HPV-positive cells. In vitro assays were performed to analyze the transduction efficiency of the vectors and the cell viability following viral infection. Then, the UPCI SCC090 cell line (HPV-positive) was used to establish subcutaneous tumors in the flanks of nude mice. The tumors were then treated with either one dose of the virus or four doses (injected every fourth day).

RESULTS

The transduction analysis with luciferase-expressing viruses demonstrated that the 5/3 fiber modification maximized virus infectivity. In vitro, both viruses (5/3Δ24 and 5/3CB016) demonstrated profound oncolytic effects. The 5/3CB016 virus was more selective for HPV-positive HNSCC cells, whereas the 5/3Δ24 virus killed HNSCC cells regardless of HPV status. In vivo, single injections of both viruses demonstrated anti-tumor effects for only a few days following viral inoculation. However, after four viral injections, there was statistically significant reductions in tumor growth when compared to the control group (p<0.05).

CONCLUSION

CRAds targeted to HPV-positive HNSCCs demonstrated excellent in vitro and in vivo therapeutic effects, and they have the potential to be clinically translated as a novel treatment modality for this emerging disease.

Targeted Adenoviral Vector Demonstrates Enhanced Efficacy for In Vivo Gene Therapy of Uterine Leiomyoma

BACKGROUND

Gene therapy is a potentially effective non-surgical approach for the treatment of uterine leiomyoma. We demonstrated that targeted adenovirus vector, Ad-SSTR-RGD-TK/GCV, was highly effective in selectively inducing apoptosis and inhibiting proliferation of human leiomyoma cells in vitro while sparing normal myometrial cells.

STUDY DESIGN

An in-vivo study, to compare efficacy and safety of modified adenovirus vector Ad-SSTR-RGD-TK/GCV versus untargeted vector for treatment of leiomyoma.

MATERIALS AND METHODS

Female nude mice were implanted with rat leiomyoma cells subcutaneously. Then mice were randomized into three groups. Group 1 received Ad-LacZ (marker gene), Group 2 received untargeted Ad-TK, and Group 3 received the targeted Ad-SSTR-RGD-TK. Tumors were measured weekly for 4 weeks. Then mice were sacrificed and tissue samples were collected. Evaluation of markers of apoptosis, proliferation, extracellular matrix, and angiogenesis was performed using Western Blot & Immunohistochemistry. Statistical analysis was done using ANOVA. Dissemination of adenovirus was assessed by PCR.

RESULTS

In comparison with the untargeted vector, the targeted adenoviral vector significantly shrank leiomyoma size (P < 0.05), reduced expression of proliferation marker (PCNA) (P < 0.05), induced expression of apoptotic protein, c-PARP-1, (P < 0.05) and inhibited expression of extracellular matrix-related genes (TGF beta 3) and angiogenesis-related genes (VEGF & IGF-1) (P < 0.01). There were no detectable adenovirus in tested tissues other than leiomyoma lesions with both targeted and untargeted adenovirus.

CONCLUSION

Targeted adenovirus, effectively reduces tumor size in leiomyoma without dissemination to other organs. Further evaluation of this localized targeted strategy for gene therapy is needed in appropriate preclinical humanoid animal models in preparation for a future pilot human trial.

A Multi Targeting Conditionally Replicating Adenovirus Displays Enhanced Oncolysis while Maintaining Expression of Immunotherapeutic Agents

Studies have demonstrated that oncolytic adenoviruses based on a 24 base pair deletion in the viral E1A gene (D24) may be promising therapeutics for treating a number of cancer types. In order to increase the therapeutic potential of these oncolytic viruses, a novel conditionally replicating adenovirus targeting multiple receptors upregulated on tumors was generated by incorporating an Ad5/3 fiber with a carboxyl terminus RGD ligand. The virus displayed full cytopathic effect in all tumor lines assayed at low titers with improved cytotoxicity over Ad5-RGD D24, Ad5/3 D24 and an HSV oncolytic virus. The virus was then engineered to deliver immunotherapeutic agents such as GM-CSF while maintaining enhanced heterogenic oncolysis.

Assessment of current virotherapeutic application schemes: "hit hard and early" versus "killing softly"?

Over the past two decades, a considerable amount of oncolytic vector families has entered numerous clinical trials. However, to this date, the field has not yet been able to come to a common understanding regarding the best possible ways to administer oncolytic viruses to cancer patients. This is mainly due to the fact that so far clinical trials being designed for head-to-head comparisons (such as using two different virotherapeutics originating from two distinct virus families being applied via identical routes in the same types of cancer) are still missing. Hence, there is no consent (i) on the best route of virotherapeutics administration (e.g., systemic versus intratumoral), (ii) on the virus dosages to be applied, (iii) on dosing intervals, and (iv) on the numbers of repetitive courses of virus administration. As the detailed comparison of clinical virotherapy trial regimens is time-consuming and complex, we here present an overview of current state-of-the-art virotherapeutic application schemes. Notably, our comprehensive assessment culminates in raising two rough classifications of virotherapeutic strategies, i.e., "hit hard and early" versus "killing softly". In order to find out which one of these two gross alternatives might be most successful for each and every tumor entity, we here suggest the implementation of phase 1/2 studies, which primarily aim at a repetitive sampling and analysis of tumor samples in cancer patients treated with oncolytic viruses reading out (i) virus-specific, (ii) tumor-specific as well as (iii) immunotherapeutic parameters. On this basis, a rational design of significantly improved virotherapeutic application schemes should be possible in the future.

Advanced targeted therapies in cancer: Drug nanocarriers, the future of chemotherapy

Cancer is the second worldwide cause of death, exceeded only by cardiovascular diseases. It is characterized by uncontrolled cell proliferation and an absence of cell death that, except for hematological cancers, generates an abnormal cell mass or tumor. This primary tumor grows thanks to new vascularization and, in time, acquires metastatic potential and spreads to other body sites, which causes metastasis and finally death. Cancer is caused by damage or mutations in the genetic material of the cells due to environmental or inherited factors. While surgery and radiotherapy are the primary treatment used for local and non-metastatic cancers, anti-cancer drugs (chemotherapy, hormone and biological therapies) are the choice currently used in metastatic cancers. Chemotherapy is based on the inhibition of the division of rapidly growing cells, which is a characteristic of the cancerous cells, but unfortunately, it also affects normal cells with fast proliferation rates, such as the hair follicles, bone marrow and gastrointestinal tract cells, generating the characteristic side effects of chemotherapy. The indiscriminate destruction of normal cells, the toxicity of conventional chemotherapeutic drugs, as well as the development of multidrug resistance, support the need to find new effective targeted treatments based on the changes in the molecular biology of the tumor cells. These novel targeted therapies, of increasing interest as evidenced by FDA-approved targeted cancer drugs in recent years, block biologic transduction pathways and/or specific cancer proteins to induce the death of cancer cells by means of apoptosis and stimulation of the immune system, or specifically deliver chemotherapeutic agents to cancer cells, minimizing the undesirable side effects. Although targeted therapies can be achieved directly by altering specific cell signaling by means of monoclonal antibodies or small molecules inhibitors, this review focuses on indirect targeted approaches that mainly deliver chemotherapeutic agents to molecular targets overexpressed on the surface of tumor cells. In particular, we offer a detailed description of different cytotoxic drug carriers, such as liposomes, carbon nanotubes, dendrimers, polymeric micelles, polymeric conjugates and polymeric nanoparticles, in passive and active targeted cancer therapy, by enhancing the permeability and retention or by the functionalization of the surface of the carriers, respectively, emphasizing those that have received FDA approval or are part of the most important clinical studies up to date. These drug carriers not only transport the chemotherapeutic agents to tumors, avoiding normal tissues and reducing toxicity in the rest of the body, but also protect cytotoxic drugs from degradation, increase the half-life, payload and solubility of cytotoxic agents and reduce renal clearance. Despite the many advantages of all the anticancer drug carriers analyzed, only a few of them have reached the FDA approval, in particular, two polymer-protein conjugates, five liposomal formulations and one polymeric nanoparticle are available in the market, in contrast to the sixteen FDA approval of monoclonal antibodies. However, there are numerous clinical trials in progress of polymer-protein and polymer-drug conjugates, liposomal formulations, including immunoliposomes, polymeric micelles and polymeric nanoparticles. Regarding carbon nanotubes or dendrimers, there are no FDA approvals or clinical trials in process up to date due to their unresolved toxicity. Moreover, we analyze in detail the more promising and advanced preclinical studies of the particular case of polymeric nanoparticles as carriers of different cytotoxic agents to active and passive tumor targeting published in the last 5 years, since they have a huge potential in cancer therapy, being one of the most widely studied nano-platforms in this field in the last years. The interest that these formulations have recently achieved is stressed by the fact that 90% of the papers based on cancer therapeutics with polymeric nanoparticles have been published in the last 6 years (PubMed search).

Paclitaxel resistance increases oncolytic adenovirus efficacy via upregulated CAR expression and dysfunctional cell cycle control

Resistance to paclitaxel chemotherapy frequently develops in ovarian cancer. Oncolytic adenoviruses are a novel therapy for human malignancies that are being evaluated in early phase trials. However, there are no reliable predictive biomarkers for oncolytic adenovirus activity in ovarian cancer. We investigated the link between paclitaxel resistance and oncolytic adenovirus activity using established ovarian cancer cell line models, xenografts with de novo paclitaxel resistance and tumour samples from two separate trials. The activity of multiple Ad5 vectors, including dl922-947 (E1A CR2-deleted), dl1520 (E1B-55K deleted) and Ad5 WT, was significantly increased in paclitaxel resistant ovarian cancer in vitro and in vivo. This was associated with greater infectivity resulting from increased expression of the primary receptor for Ad5, CAR (coxsackie adenovirus receptor). This, in turn, resulted from increased CAR transcription secondary to histone modification in resistant cells. There was increased CAR expression in intraperitoneal tumours with de novo paclitaxel resistance and in tumours from patients with clinical resistance to paclitaxel. Increased CAR expression did not cause paclitaxel resistance, but did increase inflammatory cytokine expression. Finally, we identified dysregulated cell cycle control as a second mechanism of increased adenovirus efficacy in paclitaxel-resistant ovarian cancer. Ad11 and Ad35, both group B adenoviruses that utilise non-CAR receptors to infect cells, are also significantly more effective in paclitaxel-resistant ovarian cell models. Inhibition of CDK4/6 using PD-0332991 was able both to reverse paclitaxel resistance and reduce adenovirus efficacy. Thus, paclitaxel resistance increases oncolytic adenovirus efficacy via at least two separate mechanisms - if validated further, this information could have future clinical utility to aid patient selection for clinical trials.

The oncolytic adenovirus Δ24-RGD in combination with cisplatin exerts a potent anti-osteosarcoma activity

Osteosarcoma is the most common malignant bone tumor in children and adolescents. The presence of metastases and the lack of response to conventional treatment are the major adverse prognostic factors. Therefore, there is an urgent need for new treatment strategies that overcome both of these problems. Our purpose was to elucidate whether the use of the oncolytic adenovirus Δ24-RGD alone or in combination with standard chemotherapy would be effective, in vitro and in vivo, against osteosarcoma. Our results showed that Δ24-RGD exerted a potent antitumor effect against osteosarcoma cell lines that was increased by the addition of cisplatin. Δ24-RGD osteosarcoma treatment resulted in autophagy in vitro that was further enhanced when combined with cisplatin. Of importance, administration of Δ24-RGD and/or cisplatin, in novel orthotopic and two lung metastatic models in vivo resulted in a significant reduction of tumor burden meanwhile maintaining a safe toxicity profile. Together, our data underscore the potential of Δ24-RGD to become a realistic therapeutic option for primary and metastatic pediatric osteosarcoma. Moreover, this study warrants a future clinical trial to evaluate the safety and efficacy of Δ24-RGD for this devastating disease.

ORCA-010, a novel potency-enhanced oncolytic adenovirus, exerts strong antitumor activity in preclinical models

Improving the antitumor potency of current oncolytic adenoviruses represents one of the major challenges in development of these viruses for clinical use. We have generated an oncolytic adenovirus carrying the safety-enhancing E1AΔ24 deletion, the potency-enhancing T1 mutation, and the infectivity-enhancing fiber RGD modification. The results of in vitro cytotoxicity assays on 15 human cancer cell lines derived from different tumor types demonstrated that ORCA-010 is more potent than Ad5-Δ24RGD or ONYX-015. As ORCA-010 will initially be developed for the treatment of prostate cancer, selectivity experiments were performed using primary human prostate cells. ORCA-010 killed cancer cells more effectively than these primary human cells. In both primary prostate fibroblasts and epithelial cells, ORCA-010 was as safe as Ad5-Δ24RGD. Evaluation of ORCA-010 in in vivo xenograft tumor models in nude mice showed that ORCA-010 significantly inhibited growth of prostate, lung, and ovarian tumors and conferred prolonged survival of tumor-bearing animals. Furthermore, we observed a substantial increase in infectious viral particles in tumors injected with ORCA-010. The number of infectious viral particles increased after treatment and infectious particles remained present up to at least 4 weeks posttreatment. Intratumoral virus replication was associated with substantial necrosis and fibrosis. In conclusion, ORCA-010 is more potent than earlier generation oncolytic adenoviruses, without demonstrating increased toxicity. ORCA-010 exerted strong in vivo antitumor activity and is therefore a suitable candidate for clinical evaluation.

The in vivo therapeutic efficacy of the oncolytic adenovirus Delta24-RGD is mediated by tumor-specific immunity

The oncolytic adenovirus Delta24-RGD represents a new promising therapeutic agent for patients with a malignant glioma and is currently under investigation in clinical phase I/II trials. Earlier preclinical studies showed that Delta24-RGD is able to effectively lyse tumor cells, yielding promising results in various immune-deficient glioma models. However, the role of the immune response in oncolytic adenovirus therapy for glioma has never been explored. To this end, we assessed Delta24-RGD treatment in an immune-competent orthotopic mouse model for glioma and evaluated immune responses against tumor and virus. Delta24-RGD treatment led to long-term survival in 50% of mice and this effect was completely lost upon administration of the immunosuppressive agent dexamethasone. Delta24-RGD enhanced intra-tumoral infiltration of F4/80+ macrophages, CD4+ and CD8+ T-cells, and increased the local production of pro-inflammatory cytokines and chemokines. In treated mice, T cell responses were directed to the virus as well as to the tumor cells, which was reflected in the presence of protective immunological memory in mice that underwent tumor rechallenge. Together, these data provide evidence that the immune system plays a vital role in the therapeutic efficacy of oncolytic adenovirus therapy of glioma, and may provide angles to future improvements on Delta24-RGD therapy.

Potent antitumor activity of oncolytic adenovirus expressing Beclin-1 via induction of autophagic cell death in leukemia

An attractive strategy among adenovirus-based oncolytic systems is to design adenoviral vectors to express pro-apoptotic genes, in which this gene-virotherapy approach significantly enhances tumor cell death by activating apoptotic pathways. However, the existence of cancer cells with apoptotic defects is one of the major obstacles in gene-virotherapy. Here, we investigated whether a strategy that combines the oncolytic effects of an adenoviral vector with simultaneous expression of Beclin-1, an autophagy gene, offers a therapeutic advantage for leukemia. A Beclin-1 cDNA was cloned in an oncolytic adenovirus with chimeric Ad5/11 fiber (SG511-BECN). SG511-BECN treatment induced significant autophagic cell death, and resulted in enhanced cell killing in a variety of leukemic cell lines and primary leukemic blasts. SG511-BECN effects were seen in chronic myeloid leukemia and acute myeloid leukemia with resistance to imatinib or chemotherapy, but exhibited much less cytotoxicity on normal cells. The SG511-BECN-induced autophagic cell death could be partially reversed by RNA interference knockdown of UVRAG, ATG5, and ATG7. We also showed that SG511-BECN strongly inhibited the growth of leukemic progenitors in vitro. In murine leukemia models, SG511-BECN prolonged the survival and decreased the xenograft tumor size by inducing autophagic cell death. Our results suggest that infection of leukemia cells with an oncolytic adenovirus overexpressing Beclin-1 can induce significant autophagic cell death and provide a new strategy for the elimination of leukemic cells via a unique mechanism of action distinct from apoptosis.