Systemic delivery of oncolytic viruses: hopes and hurdles

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.

A review exploring the fusion of oncolytic viruses and cancer immunotherapy: An innovative strategy in the realm of cancer treatment

Oncolytic viruses (OVs) are increasingly recognized as potent tools in cancer therapy, effectively targeting and eradicating oncogenic conditions while sparing healthy cells. They enhance antitumor immunity by triggering various immune responses throughout the cancer cycle. Genetically engineered OVs swiftly destroy cancerous tissues and activate the immune system by releasing soluble antigens like danger signals and interferons. Their ability to stimulate both innate and adaptive immunity makes them particularly attractive in cancer immunotherapy. Recent advancements involve combining OVs with other immune therapies, yielding promising results. Transgenic OVs, designed to enhance immunostimulation and specifically target cancer cells, further improve immune responses. This review highlights the intrinsic mechanisms of OVs and underscores their synergistic potential with other immunotherapies. It also proposes strategies for optimizing armed OVs to bolster immunity against tumors.

The therapeutic impact of programmed death - 1 in the treatment of colorectal cancer

Colorectal cancer (CRC) is the most common type of newly diagnosed cancer. Metastatic spread and multifactorial chemoresistance have limited the benefits of current therapies. Hence, it is imperative to identify new therapeutic agents to increase treatment efficacy. One of CRC's most promising immunotherapeutic targets is programmed death-1 (PD-1), a cell surface receptor that regulates immune responses. In this paper, we provide an overview of the therapeutic impact of PD-1 in the treatment of CRC. Cancer cells can exploit the PD-1 pathway by upregulating its programmed death-ligand 1 (PD-L1) ligand to evade immune surveillance. The binding of PD-L1 to PD-1 inhibits T cell function, leading to tumor immune escape. PD-1 inhibitors, such as pembrolizumab and nivolumab, block the PD-1/PD-L1 interaction. Clinical trials evaluating PD-1 inhibitors in advanced CRC have shown promising results. In patients with microsatellite instability-high (MSI-H) or mismatch repair-deficient (dMMR) tumors characterized by high mutation rates and increased immunogenicity, PD-1 blockade has demonstrated remarkable efficacy. As a result, pembrolizumab and nivolumab have received accelerated approval by regulatory authorities for the treatment of MSI-H/dMMR metastatic CRC. Additionally, combination approaches, such as combining PD-1 inhibitors with other immunotherapies or targeted agents, are being explored. Despite the success of PD-1 inhibitors in CRC, challenges still exist. Immune-related adverse events can occur and require close monitoring. In conclusion, PD-1 inhibitors have demonstrated significant therapeutic impact, particularly in patients with MSI-H/dMMR tumors.

Nanotechnology and bioengineering approaches to improve the potency of mesenchymal stem cell as an off-the-shelf versatile tumor delivery vehicle

Targeting actionable mutations in oncogene-driven cancers and the evolution of immuno-oncology are the two prominent revolutions that have influenced cancer treatment paradigms and caused the emergence of precision oncology. However, intertumoral and intratumoral heterogeneity are the main challenges in both fields of precision cancer treatment. In other words, finding a universal marker or pathway in patients suffering from a particular type of cancer is challenging. Therefore, targeting a single hallmark or pathway with a single targeted therapeutic will not be efficient for fighting against tumor heterogeneity. Mesenchymal stem cells (MSCs) possess favorable characteristics for cellular therapy, including their hypoimmune nature, inherent tumor-tropism property, straightforward isolation, and multilineage differentiation potential. MSCs can be loaded with various chemotherapeutics and oncolytic viruses. The combination of these intrinsic features with the possibility of genetic manipulation makes them a versatile tumor delivery vehicle that can be used for in vivo selective tumor delivery of various chemotherapeutic and biological therapeutics. MSCs can be used as biofactory for the local production of chemical or biological anticancer agents at the tumor site. MSC-mediated immunotherapy could facilitate the sustained release of immunotherapeutic agents specifically at the tumor site, and allow for the achievement of therapeutic concentrations without the need for repetitive systemic administration of high therapeutic doses. Despite the enthusiasm evoked by preclinical studies that used MSC in various cancer therapy approaches, the translation of MSCs into clinical applications has faced serious challenges. This manuscript, with a critical viewpoint, reviewed the preclinical and clinical studies that have evaluated MSCs as a selective tumor delivery tool in various cancer therapy approaches, including gene therapy, immunotherapy, and chemotherapy. Then, the novel nanotechnology and bioengineering approaches that can improve the potency of MSC for tumor targeting and overcoming challenges related to their low localization at the tumor sites are discussed.

Intracellular delivery of oncolytic viruses with engineered Salmonella causes viral replication and cell death

As therapies, oncolytic viruses regress tumors and have the potential to induce antitumor immune responses that clear hard-to-treat and late-stage cancers. Despite this promise, clearance from the blood prevents treatment of internal solid tumors. To address this issue, we developed virus-delivering Salmonella (VDS) to carry oncolytic viruses into cancer cells. The VDS strain contains the PsseJ-lysE delivery circuit and has deletions in four homologous recombination genes (ΔrecB, ΔsbcB, ΔsbcCD, and ΔrecF) to preserve essential hairpins in the viral genome required for replication and infectivity. VDS delivered the genome for minute virus of mice (MVMp) to multiple cancers, including breast, pancreatic, and osteosarcoma. Viral delivery produced functional viral particles that are cytotoxic and infective to neighboring cells. The release of mature virions initiated new rounds of infection and amplified the infection. Using Salmonella for delivery will circumvent the limitations of oncolytic viruses and will provide a new therapy for many cancers.

Nanoparticle-Mediated Synergistic Chemoimmunotherapy for Cancer Treatment

Until now, there has been a lack of effective strategies for cancer treatment. Immunotherapy has high potential in treating several cancers but its efficacy is limited as a monotherapy. Chemoimmunotherapy (CIT) holds promise to be widely used in cancer treatment. Therefore, identifying their involvement and potential synergy in CIT approaches is decisive. Nano-based drug delivery systems (NDDSs) are ideal delivery systems because they can simultaneously target immune cells and cancer cells, promoting drug accumulation, and reducing the toxicity of the drug. In this review, we first introduce five current immunotherapies, including immune checkpoint blocking (ICB), adoptive cell transfer therapy (ACT), cancer vaccines, oncolytic virus therapy (OVT) and cytokine therapy. Subsequently, the immunomodulatory effects of chemotherapy by inducing immunogenic cell death (ICD), promoting tumor killer cell infiltration, down-regulating immunosuppressive cells, and inhibiting immune checkpoints have been described. Finally, the NDDSs-mediated collaborative drug delivery systems have been introduced in detail, and the development of NDDSs-mediated CIT nanoparticles has been prospected.

Tumor-targeted delivery of copper-manganese biomineralized oncolytic adenovirus for colorectal cancer immunotherapy

Oncolytic viral therapy (OVT) is a novel anti-tumor immunotherapy approach, specifically replicating within tumor cells. Currently, oncolytic viruses are mainly administered by intratumoral injection. However, achieving good results for distant metastatic tumors is challenging. In this study, a multifunctional oncolytic adenovirus, OA@CuMnCs, was developed using bimetallic ions copper and manganese. These metal cations form a biomineralized coating on the virus's surface, reducing immune clearance. It is known that viruses upregulate the expression of PD-L1. Copper ions in OA@CuMnCs can decrease the PD-L1 expression of tumor cells, thereby promoting immune cell-related factor release. This process involves antigen presentation and the combination of immature dendritic cells, transforming them into mature dendritic cells. It changes "cold" tumors into "hot" tumors, further inducing immunogenic cell death. While oncolytic virus replication requires oxygen, manganese ions in OA@CuMnCs can react with endogenous hydrogen peroxide. This reaction produces oxygen, enhancing the virus's replication ability and the tumor lysis effect. Thus, this multifunctionally coated OA@CuMnCs demonstrates potent amplification in immunotherapy efficacy, and shows great potential for further clinical OVT. STATEMENT OF SIGNIFICANCE: Oncolytic virus therapy (OVs) is a new anti-tumor immunotherapy method that can specifically replicate in tumor cells. Although the oncolytic virus can achieve a therapeutic effect on some non-metastatic tumors through direct intratumoral injection, there are still three major defects in the treatment of metastatic tumors: immune response, hypoxia effect, and administration route. Various studies have shown that the immune response in vivo can be overcome by modifying or wrapping the surface protein of the oncolytic virus. In this paper, a multifunctional coating of copper and manganese was prepared by combining the advantages of copper and manganese ions. The coating has a simple preparation method and mild conditions, and can effectively enhance tumor immunotherapy.

Transient inhibition of neutrophil functions enhances the antitumor effect of intravenously delivered oncolytic vaccinia virus

Oncolytic viruses (OVs) possess the unique ability to selectively replicate within tumor cells, leading to their destruction, while also reversing the immunosuppression within the tumor microenvironment and triggering an antitumor immune response. As a result, OVs have emerged as one of the most promising approaches in cancer therapy. However, the effective delivery of intravenously administered OVs faces significant challenges imposed by various immune cells within the peripheral blood, hindering their access to tumor sites. Notably, neutrophils, the predominant white blood cell population comprising approximately 50%-70% of circulating white cells in humans, show phagocytic properties. Our investigation revealed that the majority of oncolytic vaccinia viruses (VV) are engulfed and degraded by neutrophils in the bloodstream. The depletion of neutrophils using the anti-LY6G Ab (1-A8) resulted in an increased accumulation of circulating oncolytic VV in the peripheral blood and enhanced deposition at the tumor site, consequently amplifying the antitumor effect. Neutrophils heavily rely on PI3K signaling to sustain their phagocytic process. Additionally, our study determined that the inhibition of the PI3Kinase delta isoform by idelalisib (CAL-101) suppressed the uptake of oncolytic VV by neutrophils. This inhibition led to a greater presence of oncolytic VV in both the peripheral blood and at the tumor site, resulting in improved efficacy against the tumor. In conclusion, our study showed that inhibiting neutrophil functions can significantly enhance the antitumor efficacy of intravenous oncolytic VV.

Molecular insights and promise of oncolytic virus based immunotherapy

Discovering a therapeutic that can counteract the aggressiveness of this disease's mechanism is crucial for improving survival rates for cancer patients and for better understanding the most different types of cancer. In recent years, using these viruses as an anticancer therapy has been thought to be successful. They mostly work by directly destroying cancer cells, activating the immune system to fight cancer, and expressing exogenous effector genes. For the treatment of tumors, oncolytic viruses (OVs), which can be modified to reproduce only in tumor tissues and lyse them while preserving the healthy non-neoplastic host cells and reinstating antitumor immunity which present a novel immunotherapeutic strategy. OVs can exist naturally or be created in a lab by altering existing viruses. These changes heralded the beginning of a new era of less harmful virus-based cancer therapy. We discuss three different types of oncolytic viruses that have already received regulatory approval to treat cancer as well as clinical research using oncolytic adenoviruses. The primary therapeutic applications, mechanism of action of oncolytic virus updates, future views of this therapy will be covered in this chapter.

New hopes for the breast cancer treatment: perspectives on the oncolytic virus therapy

Oncolytic virus (OV) therapy has emerged as a promising frontier in cancer treatment, especially for solid tumours. While immunotherapies like immune checkpoint inhibitors and CAR-T cells have demonstrated impressive results, their limitations in inducing complete tumour regression have spurred researchers to explore new approaches targeting tumours resistant to current immunotherapies. OVs, both natural and genetically engineered, selectively replicate within cancer cells, inducing their lysis while sparing normal tissues. Recent advancements in clinical research and genetic engineering have enabled the development of targeted viruses that modify the tumour microenvironment, triggering anti-tumour immune responses and exhibiting synergistic effects with other cancer therapies. Several OVs have been studied for breast cancer treatment, including adenovirus, protoparvovirus, vaccinia virus, reovirus, and herpes simplex virus type I (HSV-1). These viruses have been modified or engineered to enhance their tumour-selective replication, reduce toxicity, and improve oncolytic properties.Newer generations of OVs, such as Oncoviron and Delta-24-RGD adenovirus, exhibit heightened replication selectivity and enhanced anticancer effects, particularly in breast cancer models. Clinical trials have explored the efficacy and safety of various OVs in treating different cancers, including melanoma, nasopharyngeal carcinoma, head and neck cancer, and gynecologic malignancies. Notably, Talimogene laherparepvec (T-VEC) and Oncorine have. been approved for advanced melanoma and nasopharyngeal carcinoma, respectively. However, adverse effects have been reported in some cases, including flu-like symptoms and rare instances of severe complications such as fistula formation. Although no OV has been approved specifically for breast cancer treatment, ongoing preclinical clinical trials focus on four groups of viruses. While mild adverse effects like low-grade fever and nausea have been observed, the effectiveness of OV monotherapy in breast cancer remains insufficient. Combination strategies integrating OVs with chemotherapy, radiotherapy, or immunotherapy, show promise in improving therapeutic outcomes. Oncolytic virus therapy holds substantial potential in breast cancer treatment, demonstrating safety in trials. Multi-approach strategies combining OVs with conventional therapies exhibit more promising therapeutic effects than monotherapy, signalling a hopeful future for OV-based breast cancer treatments.

Recent progress in combination therapy of oncolytic vaccinia virus

In recent years, oncolytic viruses have emerged as promising agents for treating various cancers. An oncolytic virus is a non-pathogenic virus that, due to genetic manipulation, tends to replicate in and cause lysis of cancerous cells while leaving healthy cells unaffected. Among these viruses, vaccinia virus is an attractive platform for use as an oncolytic platform due to its 190 Kb genome with a high capacity for encoding therapeutic payloads. Combining oncolytic VV therapy with other conventional cancer treatments has been shown to be synergistic and more effective than monotherapies. Additionally, OVV can be used as a vector to deliver therapeutic payloads, alone or in combination with other treatments, to increase overall efficacy. Here, we present a comprehensive analysis of preclinical and clinical studies that have evaluated the efficacy of oncolytic vaccinia viruses in cancer immunotherapy. We discuss the outcomes of these studies, including tumor regression rates, overall survival benefits, and long-term responses. Moreover, we provide insights into the challenges and limitations associated with oncolytic vaccinia virus- based therapies, including immune evasion mechanisms, potential toxicities, and the development of resistance.

Enhancement of Therapeutic Potential of Oncolytic Virus with Homologous Tumor Cell Membranes for Pancreatic Cancer

Pancreatic cancer is a leading cause of cancer-related deaths worldwide. Conventional therapies often provide limited success, necessitating the need for novel therapeutic strategies. Oncolytic viruses (OVs) are a class of viruses that specifically target and kill cancer cells while leaving normal cells unharmed. These viruses have shown promise in the treatment of various cancers, including pancreatic cancer. However, their use in clinical settings has been limited by several factors. Their inability to efficiently infect and kill tumor cells. To overcome this limitation, a cell membrane-coated oncolytic virus was developed. However, the necessity of homologous and nonhomologous tumor cell membranes for their function has not yet been proven. This novel virus displayed increased infectivity and killing activity against tumor cells compared to nonhomologous tumor cell membranes and noncoated viruses. We believe that the homologous tumor cell membranes-coated OVs can enhance the therapeutic potential for pancreatic cancer therapy.

Arming oncolytic viruses with bispecific T cell engagers: The evolution and current status

Oncolytic viruses (OVs) are emerging as therapeutically relevant anticancer agents as contemporary immunotherapy gains traction. Furthermore, OVs are an ideal platform for genetic modification to express therapeutic transgenes. Bispecific T cell engagers (BiTEs) can redirect T cells to tumor cells, resulting in targeted cytotoxicity. BiTEs have demonstrated success in hematological cancers but are rarely used in solid tumors. The drawbacks of BiTEs, including inadequate delivery and on-target-off-tumor activity have limited their efficacy. Combining OVs with BiTEs is a prospective area to investigate. This combined strategy can benefit from the best qualities of both therapies while overcoming the limitations.

Oncolytic Virotherapy: A New Paradigm in Cancer Immunotherapy

Oncolytic viruses (OVs) are emerging as potential treatment options for cancer. Natural and genetically engineered viruses exhibit various antitumor mechanisms. OVs act by direct cytolysis, the potentiation of the immune system through antigen release, and the activation of inflammatory responses or indirectly by interference with different types of elements in the tumor microenvironment, modification of energy metabolism in tumor cells, and antiangiogenic action. The action of OVs is pleiotropic, and they show varied interactions with the host and tumor cells. An important impediment in oncolytic virotherapy is the journey of the virus into the tumor cells and the possibility of its binding to different biological and nonbiological vectors. OVs have been demonstrated to eliminate cancer cells that are resistant to standard treatments in many clinical trials for various cancers (melanoma, lung, and hepatic); however, there are several elements of resistance to the action of viruses per se. Therefore, it is necessary to evaluate the combination of OVs with other standard treatment modalities, such as chemotherapy, immunotherapy, targeted therapies, and cellular therapies, to increase the response rate. This review provides a comprehensive update on OVs, their use in oncolytic virotherapy, and the future prospects of this therapy alongside the standard therapies currently used in cancer treatment.

Oncolytic virotherapy in cancer treatment: challenges and optimization prospects

Oncolytic viruses (OVs) are emerging cancer therapeutics that offer a multifaceted therapeutic platform for the benefits of replicating and lysing tumor cells, being engineered to express transgenes, modulating the tumor microenvironment (TME), and having a tolerable safety profile that does not overlap with other cancer therapeutics. The mechanism of OVs combined with other antitumor agents is based on immune-mediated attack resistance and might benefit patients who fail to achieve durable responses after immune checkpoint inhibitor (ICI) treatment. In this Review, we summarize data on the OV mechanism and limitations of monotherapy, which are currently in the process of combination partner development, especially with ICIs. We discuss some of the hurdles that have limited the preclinical and clinical development of OVs. We also describe the available data and provide guidance for optimizing OVs in clinical practice, as well as a summary of approved and promising novel OVs with clinical indications.

Alliance between titans: combination strategies of CAR-T cell therapy and oncolytic virus for the treatment of hematological malignancies

There have been several clinical studies using chimeric antigen receptor (CAR)-T cell therapy for different hematological malignancies. It has transformed the therapy landscape for hematologic malignancies dramatically. Nonetheless, in acute myeloid leukemia (AML) and T cell malignancies, it still has a dismal prognosis. Even in the most promising locations, recurrence with CAR-T treatment remains a big concern. Oncolytic viruses (OVs) can directly lyse tumor cells or cause immune responses, and they can be manipulated to create therapeutic proteins, increasing anticancer efficacy. Oncolytic viruses have been proven in a rising number of studies to be beneficial in hematological malignancies. There are limitations that cannot be avoided by using either treatment alone, and the combination of CAR-T cell therapy and oncolytic virus therapy may complement the disadvantages of individual application, enhance the advantages of their respective treatment methods and improve the treatment effect. The alternatives for combining two therapies in hematological malignancies are discussed in this article.

Efficacy of Systemically Administered Retargeted Oncolytic Herpes Simplex Viruses-Clearance and Biodistribution in Naïve and HSV-Preimmune Mice

We investigated the anticancer efficacy, blood clearance, and tissue biodistribution of systemically administered retargeted oncolytic herpes simplex viruses (ReHVs) in HSV-naïve and HSV-preimmunized (HSV-IMM) mice. Efficacy was tested against lung tumors formed upon intravenous administration of cancer cells, a model of metastatic disease, and against subcutaneous distant tumors. In naïve mice, HER2- and hPSMA-retargeted viruses, both armed with mIL-12, were highly effective, even when administered to mice with well-developed tumors. Efficacy was higher for combination regimens with immune checkpoint inhibitors. A significant amount of infectious virus persisted in the blood for at least 1 h. Viral genomes, or fragments thereof, persisted in the blood and tissues for days. Remarkably, the only sites of viral replication were the lungs of tumor-positive mice and the subcutaneous tumors. No replication was detected in other tissues, strengthening the evidence of the high cancer specificity of ReHVs, a property that renders ReHVs suitable for systemic administration. In HSV-IMM mice, ReHVs administered at late times failed to exert anticancer efficacy, and the circulating virus was rapidly inactivated. Serum stability and in vivo whole blood stability assays highlighted neutralizing antibodies as the main factor in virus inactivation. Efforts to deplete mice of the neutralizing antibodies are ongoing.

Virus-Protein Corona Replacement Strategy to Improve the Antitumor Efficacy of Intravenously Injected Oncolytic Adenovirus

Intravenous administration of oncolytic adenoviruses (OVs) is a hopeful tumor therapeutic modality. However, the sharp clearance of OVs by the immune system dampens its effectiveness. Many studies have attempted to extend the circulation of intravenously administered OVs, almost all by preventing OVs from binding to neutralizing antibodies and complements in the blood, but the results have not been satisfactory. In contrast to previous conclusions, we found that the key to improving the circulation of OVs is to prevent the formation of the virus-protein corona rather than simply preventing the binding of neutralizing antibodies or complements to OVs. After identifying the key protein components of the virus-protein corona, we proposed a virus-protein corona replacement strategy, where an artificial virus-protein corona was formed on OVs to completely prevent the interaction of OVs with key virus-protein corona components in the plasma. It was found that this strategy dramatically prolonged the circulation time of OVs by over 30 fold and increased the distribution of OVs in tumors by over 10-fold, resulting in superior antitumor efficacy in primary and metastatic tumor models. Our finding provides a perspective on intravenous delivery of OVs, shifting the focus of future studies from preventing OV binding with neutralization antibodies and complements to preventing OVs from interacting with key virus-protein corona components in the plasma.

Oncolytic Virus Engineering and Utilizations: Cancer Immunotherapy Perspective

Oncolytic viruses have positively impacted cancer immunotherapy over the past 20 years. Both natural and genetically modified viruses have shown promising results in treating various cancers. Various regulatory authorities worldwide have approved four commercial oncolytic viruses, and more are being developed to overcome this limitation and obtain better anti-tumor responses in clinical trials at various stages. Faster advancements in translating research into the commercialization of cancer immunotherapy and a comprehensive understanding of the modification strategies will widen the current knowledge of future technologies related to the development of oncolytic viruses. In this review, we discuss the strategies of virus engineering and the progress of clinical trials to achieve virotherapeutics.

Human Monocytes Are Suitable Carriers for the Delivery of Oncolytic Herpes Simplex Virus Type 1 In Vitro and in a Chicken Embryo Chorioallantoic Membrane Model of Cancer

Oncolytic viruses (OVs) are promising therapeutics for tumors with a poor prognosis. An OV based on herpes simplex virus type 1 (oHSV-1), talimogene laherparepvec (T-VEC), has been recently approved by the Food and Drug Administration (FDA) and by the European Medicines Agency (EMA) for the treatment of unresectable melanoma. T-VEC, like most OVs, is administered via intratumoral injection, underlining the unresolved problem of the systemic delivery of the oncolytic agent for the treatment of metastases and deep-seated tumors. To address this drawback, cells with a tropism for tumors can be loaded ex vivo with OVs and used as carriers for systemic oncolytic virotherapy. Here, we evaluated human monocytes as carrier cells for a prototype oHSV-1 with a similar genetic backbone as T-VEC. Many tumors specifically recruit monocytes from the bloodstream, and autologous monocytes can be obtained from peripheral blood. We demonstrate here that oHSV-1-loaded primary human monocytes migrated in vitro towards epithelial cancer cells of different origin. Moreover, human monocytic leukemia cells selectively delivered oHSV-1 to human head-and-neck xenograft tumors grown on the chorioallantoic membrane (CAM) of fertilized chicken eggs after intravascular injection. Thus, our work shows that monocytes are promising carriers for the delivery of oHSV-1s in vivo, deserving further investigation in animal models.

The progress of microenvironment-targeted therapies in brain metastases

The incidence of brain metastases (BrM) has become a growing concern recently. It is a common and often fatal manifestation in the brain during the end-stage of many extracranial primary tumors. Increasing BrM diagnoses can be attributed to improvements in primary tumor treatments, which have extended patients’ lifetime, and allowed for earlier and more efficient detection of brain lesions. Currently, therapies for BrM encompass systemic chemotherapy, targeted therapy, and immunotherapy. Systemic chemotherapy regimens are controversial due to their associated side effects and limited efficacy. Targeted and immunotherapies have garnered significant attention in the medical field: they target specific molecular sites and modulate specific cellular components. However, multiple difficulties such as drug resistance and low permeability of the blood-brain barrier (BBB) remain significant challenges. Thus, there is an urgent need for novel therapies. Brain microenvironments consist of cellular components including immune cells, neurons, endothelial cells as well as molecular components like metal ions, nutrient molecules. Recent research indicates that malignant tumor cells can manipulate the brain microenvironment to change the anti-tumoral to a pro-tumoral microenvironment, both before, during, and after BrM. This review compares the characteristics of the brain microenvironment in BrM with those in other sites or primary tumors. Furthermore, it evaluates the preclinical and clinical studies of microenvironment-targeted therapies for BrM. These therapies, due to their diversity, are expected to overcome drug resistance or low permeability of the BBB with low side effects and high specificity. This will ultimately lead to improved outcomes for patients with secondary brain tumors.

esRAGE-expressing oHSV enhances anti-tumor efficacy by inhibition of endothelial cell activation

High-mobility group box 1 (HMGB1) is a damage-associated molecular pattern (DAMP) molecule that plays an important role in inflammation and tumorigenesis. Receptor for advanced glycation end products (RAGE) is one of the major receptors to which extracellular HMGB1 binds to mediate its activity. RAGE is highly expressed on the endothelial cells (ECs) and regulates endothelial permeability during inflammation. Here, we introduced the endogenous secretory form of RAGE (esRAGE) as a decoy receptor for RAGE ligands into an oncolytic herpes simplex virus 1 (oHSV) (OVesRAGE), which, upon release, can function to block RAGE signaling. OVesRAGE significantly decreased phosphorylation of MEK1/2 and Erk and increased cleaved PARP in glioblastoma (GBM) cells in vitro and in vivo. oHSV-infected GBM cells co-cultured with ECs were used to test OVesRAGE effect on EC activation, vessel leakiness, virus replication, and tumor cell killing. OVesRAGE could effectively secrete esRAGE and rescue virus-induced EC migration and activation. Reduced EC activation facilitated virus replication in tumor cells when co-cultured with ECs. Finally, OVesRAGE significantly enhanced therapeutic efficacy in GBM-bearing mice. Collectively, our data demonstrate that HMGB1-RAGE signaling could be a promising target and that its inhibition is a feasible approach to improve the efficacy of oHSV therapy.

Brain metastasis in breast cancer: focus on genes and signaling pathways involved, blood-brain barrier and treatment strategies

Breast cancer (BC) is one of the most prevalent types of cancer in women. Despite advancement in early detection and efficient treatment, recurrence and metastasis continue to pose a significant risk to the life of BC patients. Brain metastasis (BM) reported in 17-20 percent of BC patients is considered as a major cause of mortality and morbidity in these patients. BM includes various steps from primary breast tumor to secondary tumor formation. Various steps involved are primary tumor formation, angiogenesis, invasion, extravasation, and brain colonization. Genes involved in different pathways have been reported to be associated with BC cells metastasizing to the brain. ADAM8 gene, EN1 transcription factor, WNT, and VEGF signaling pathway have been associated with primary breast tumor; MMP1, COX2, XCR4, PI3k/Akt, ERK and MAPK pathways in angiogenesis; Noth, CD44, Zo-1, CEMIP, S0X2 and OLIG2 are involved in invasion, extravasation and colonization, respectively. In addition, the blood-brain barrier is also a key factor in BM. Dysregulation of cell junctions, tumor microenvironment and loss of function of microglia leads to BBB disruption ultimately resulting in BM. Various therapeutic strategies are currently used to control the BM in BC. Oncolytic virus therapy, immune checkpoint inhibitors, mTOR-PI3k inhibitors and immunotherapy have been developed to target various genes involved in BM in BC. In addition, RNA interference (RNAi) and CRISPR/Cas9 are novel interventions in the field of BCBM where research to validate these and clinical trials are being carried out. Gaining a better knowledge of metastasis biology is critical for establishing better treatment methods and attaining long-term therapeutic efficacies against BC. The current review has been compiled with an aim to evaluate the role of various genes and signaling pathways involved in multiple steps of BM in BC. The therapeutic strategies being used currently and the novel ones being explored to control BM in BC have also been discussed at length.

Mesenchymal stem cell-released oncolytic virus: an innovative strategy for cancer treatment

Oncolytic viruses (OVs) infect, multiply, and finally remove tumor cells selectively, causing no damage to normal cells in the process. Because of their specific features, such as, the ability to induce immunogenic cell death and to contain curative transgenes in their genomes, OVs have attracted attention as candidates to be utilized in cooperation with immunotherapies for cancer treatment. This treatment takes advantage of most tumor cells' inherent tendency to be infected by certain OVs and both innate and adaptive immune responses are elicited by OV infection and oncolysis. OVs can also modulate tumor microenvironment and boost anti-tumor immune responses. Mesenchymal stem cells (MSC) are gathering interest as promising anti-cancer treatments with the ability to address a wide range of cancers. MSCs exhibit tumor-trophic migration characteristics, allowing them to be used as delivery vehicles for successful, targeted treatment of isolated tumors and metastatic malignancies. Preclinical and clinical research were reviewed in this study to discuss using MSC-released OVs as a novel method for the treatment of cancer. Video Abstract.

The Dilemma of HSV-1 Oncolytic Virus Delivery: The Method Choice and Hurdles

Oncolytic viruses (OVs) have emerged as effective gene therapy and immunotherapy drugs. As an important gene delivery platform, the integration of exogenous genes into OVs has become a novel path for the advancement of OV therapy, while the herpes simplex virus type 1 (HSV-1) is the most commonly used. However, the current mode of administration of HSV-1 oncolytic virus is mainly based on the tumor in situ injection, which limits the application of such OV drugs to a certain extent. Intravenous administration offers a solution to the systemic distribution of OV drugs but is ambiguous in terms of efficacy and safety. The main reason is the synergistic role of innate and adaptive immunity of the immune system in the response against the HSV-1 oncolytic virus, which is rapidly cleared by the body's immune system before it reaches the tumor, a process that is accompanied by side effects. This article reviews different administration methods of HSV-1 oncolytic virus in the process of tumor treatment, especially the research progress in intravenous administration. It also discusses immune constraints and solutions of intravenous administration with the intent to provide new insights into HSV-1 delivery for OV therapy.

The application of tumor cell-derived vesicles in oncology therapy

Tumor cell-derived vesicles are released by tumor cells, have a phospholipid bilayer, and are widely distributed in various biological fluids. In recent years, it has been found that tumor cell-derived vesicles contain proteins, metabolites and nucleic acids and can be delivered to recipient cells to perform their physiological functions, such as mediating specific intercellular communication, activating or inhibiting signaling pathways, participating in regulating the modulation of tumor microenvironment and influencing tumor development, which can be used for early detection and diagnosis of cancer. In addition, tumor cell-derived vesicles exhibit multiple properties in tumor therapeutic applications and may serve as a new class of delivery systems. In this review, we elaborate on the application of tumor cell-derived vesicles in oncology therapy.

Extracellular Vesicles and Viruses: Two Intertwined Entities

Viruses share many attributes in common with extracellular vesicles (EVs). The cellular machinery that is used for EV production, packaging of substrates and secretion is also commonly manipulated by viruses for replication, assembly and egress. Viruses can increase EV production or manipulate EVs to spread their own genetic material or proteins, while EVs can play a key role in regulating viral infections by transporting immunomodulatory molecules and viral antigens to initiate antiviral immune responses. Ultimately, the interactions between EVs and viruses are highly interconnected, which has led to interesting discoveries in their associated roles in the progression of different diseases, as well as the new promise of combinational therapeutics. In this review, we summarize the relationships between viruses and EVs and discuss major developments from the past five years in the engineering of virus-EV therapies.

Nonclinical pharmacokinetics and biodistribution of VSV-GP using methods to decouple input drug disposition and viral replication

Viral replication places oncolytic viruses (OVs) in a unique niche in the field of drug pharmacokinetics (PK) as their self-amplification obscures exposure-response relationships. Moreover, standard bioanalytical techniques are unable to distinguish the input from replicated drug products. Here, we combine two novel approaches to characterize PK and biodistribution (BD) after systemic administration of vesicular stomatitis virus pseudotyped with lymphocytic choriomeningitis virus glycoprotein (VSV-GP) in healthy mice. First: to decouple input drug PK/BD versus replication PK/BD, we developed and fully characterized a replication-incompetent tool virus that retained all other critical attributes of the drug. We used this approach to quantify replication in blood and tissues and to determine its impact on PK and BD. Second: to discriminate the genomic and antigenomic viral RNA strands contributing to replication dynamics in tissues, we developed an in situ hybridization method using strand-specific probes and assessed their spatiotemporal distribution in tissues. This latter approach demonstrated that distribution, transcription, and replication localized to tissue-resident macrophages, indicating their role in PK and BD. Ultimately, our study results in a refined PK/BD profile for a replicating OV, new proposed PK parameters, and deeper understanding of OV PK/BD using unique approaches that could be applied to other replicating vectors.

Systemic cellular viroimmunotherapy for canine high-grade gliomas

BACKGROUND

Oncolytic viruses constitute a growing field of interest, both in human and veterinary oncology, given that they are particularly helpful for treating non-surgical tumors and disseminated cancer, such as high-grade gliomas. Companion dogs present malignant gliomas with biological, genetic, phenotypic, immunological, and clinical similarities to human gliomas. These features favor comparative approaches, leading to the treatment of canine oncological patients to achieve translational applications to the human clinic. The systemic administration of oncolytic viruses presents a challenge due to their limitations in effectively targeting tumors and metastases. Therefore, the aim of this study is to evaluate the safety and antitumor activity of a virotherapy used in spontaneous canine tumors.

METHODS

Ten dogs with high-grade rostrotentorial gliomas underwent weekly systemic endovenous cellular virotherapy with dCelyvir (canine mesenchymal stem cells infected with the canine oncolytic adenovirus ICOCAV17) for 8 weeks. Efficacy was determined in seven dogs according to the Response Assessment in Veterinary Neuro-Oncology criteria considering clinical status and MRI measurements. Medical history, physical and neurological examinations, and vaccination status were evaluated prior to and during follow-up. Safety was evaluated by physical examinations and hematological and biochemical changes in peripheral blood. Immune populations were analyzed by flow cytometry in peripheral blood and by gene expression and immunohistochemistry in the tumor microenvironment.

RESULTS

The treatment was well tolerated and major adverse effects were not observed. Two dogs had partial responses (76% and 86% reduction in tumor size), and 3/7 showed stable disease. ICOCAV17 was detected in peripheral blood in nine dogs, and a correlation between the ICOCAV17 particles and anti-canine adenovirus (CAV) antibodies was observed. ICOCAV17 was detected in 3/9 tumor tissues after necropsies. Regarding tumor-infiltrating lymphocytes, the dogs with disease stabilization and partial response tended to have reduced memory B-cell infiltration and increased monocyte/macrophage lineage cells.

CONCLUSIONS

These findings indicate that dCelyvir is safe and presents efficacy in canine rostrotentorial high-grade gliomas. These data are relevant to the ongoing phase Ib regulated human clinical trial that is administering this virotherapy to children, adolescents, and young adults with diffuse pontine glioma. Celyvir should be further explored as a treatment in veterinary and human neuro-oncology.

Modifying oncolytic virotherapy to overcome the barrier of the hypoxic tumor microenvironment. Where do we stand?

Viruses are completely dependent on host cell machinery for their reproduction. As a result, factors that influence the state of cells, such as signaling pathways and gene expression, could determine the outcome of viral pathogenicity. One of the important factors influencing cells or the outcome of viral infection is the level of oxygen. Recently, oncolytic virotherapy has attracted attention as a promising approach to improving cancer treatment. However, it was shown that tumor cells are mostly less oxygenated compared with their normal counterparts, which might affect the outcome of oncolytic virotherapy. Therefore, knowing how oncolytic viruses could cope with stressful environments, particularly hypoxic environments, might be essential for improving oncolytic virotherapy.

Cytotoxic effect of cloned EGFP gene on NCI-H727 cell line via genetically engineered gene transfer system

Introduction and Aim: Cancers are a complex group of genetic illnesses that develop through multistep, mutagenic processes which can invade or spread throughout the body. Recent advances in cancer treatment involve oncolytic viruses to infect and destroy cancer cells. The Newcastle disease virus (NDV), an oncolytic virus has shown to have anti-cancer effects either directly by lysing cancer cells or indirectly by activating the immune system. The green fluorescent protein (GFP) has been widely used in studying the anti-tumor activity of oncolytic viruses. This study aimed to study the anticancer effect of a recombinant rNDV-GFP clone on NCI-H727 lung carcinoma cell line in vitro.   Materials and Methods: The GFP gene was inserted to a NDV strain to create a recombinant NDV (rNDV- GFP) using reverse genetics technology. The MTT assay was used in evaluating the oncolytic effect of rNDV- GFP on the lung carcinoma NCI-H727 cells. Light and fluorescent microscopy was used to study the cytopathic effects of rNDV-GFP.   Results: MTT assay showed that rNDV-GPF inhibited the NCI-H727 tumor cell death in a time-dependent manner. A significant inhibitory effect (78.3%) for rNDV-GPF on cancer cells was observed at 96h in comparison to rNDV (22.7%) and the cytotoxicity rate was directly proportional to the MOI used. Microscopic studies showed rNDV-GPF to induce cytopathic effect post 24 h of infection.   Conclusion: The GFP-expressing recombinant NDV strains exhibited encouraging results in terms of tumor growth inhibition. Our research set the groundwork for employing recombinant NDV as an anticancer viral vector.  

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.

Virus-inspired strategies for cancer therapy

The intentional use of viruses for cancer therapy dates back over a century. As viruses are inherently immunogenic and naturally optimized delivery vehicles, repurposing viruses for drug delivery, tumor antigen presentation, or selective replication in cancer cells represents a simple and elegant approach to cancer treatment. While early virotherapy was fraught with harsh side effects and low response rates, virus-based therapies have recently seen a resurgence due to newfound abilities to engineer and tune oncolytic viruses, virus-like particles, and virus-mimicking nanoparticles for improved safety and efficacy. However, despite their great potential, very few virus-based therapies have made it through clinical trials. In this review, we present an overview of virus-inspired approaches for cancer therapy, discuss engineering strategies to enhance their mechanisms of action, and highlight their application for overcoming the challenges of traditional cancer therapies.

Development of Adenovirus Containing Liposomes Produced by Extrusion vs. Homogenization: A Comparison for Scale-Up Purposes

Adenovirus (Ad) is a widely studied viral vector for cancer therapy as it can be engineered to cause selective lysis of cancer cells. However, Ad delivery is limited in treating cancers that do not have coxsackievirus and adenovirus receptors (CAR). To overcome this challenge, Ad-encapsulated liposomes were developed that enhance the delivery of Ads and increase therapeutic efficacy. Cationic empty liposomes were manufactured first, to which an anionic Ad were added, which resulted in encapsulated Ad liposomes through charge interaction. Optimization of the liposome formula was carried out with series of formulation variables experiments using an extrusion process, which is ideal for laboratory-scale small batches. Later, the optimized formulation was manufactured with a homogenization technique-A high shear rotor-stator blending, that is ideal for large-scale manufacturing and is in compliance with Good Manufacturing Practices (GMP). Comparative in vitro transduction, physicochemical characterization, long-term storage stability at different temperature conditions, and in vivo animal studies were performed. Ad encapsulated liposomes transduced CAR deficient cells 100-fold more efficiently than the unencapsulated Ad (p ≤ 0.0001) in vitro, and 4-fold higher in tumors injected in nude mice in vivo. Both extrusion and homogenization performed similarly-with equivalent in vitro and in vivo transduction efficiencies, physicochemical characterization, and long-term storage stability. Thus, two Ad encapsulated liposomes preparation methods used herein, i.e., extrusion vs. homogenization were equivalent in terms of enhanced Ad performance and long-term storage stability; this will, hopefully, facilitate translation to the clinic.

DNA Origami Disguises Herpes Simplex Virus 1 Particles and Controls Their Virulence

DNA nanostructures are well-established vectors for packaging diversified payloads for targeted cellular delivery. Here, DNA origami rectangular sheets were combined with Herpes Simplex Virus 1 (HSV1) capsids to demonstrate surface coverage of the particle via electrostatic interactions. The optimized origami:HSV1 molar ratios led to characteristic packaging geometries ranging from dispersed "HSV1 pockets" to agglomerated "HSV1 sleeves". "Pockets" were disguised from cells in HeLa and B16F10 cells and were 44.2% less infective than naked HSV1 particles. However, the pockets were 117% more infective than naked HSV1 particles when the origami sheets were coated with folic acid. We observed infectivity from naked origami, but they are 99.1% less infective with respect to HSV1 and 99.6% less infective with respect to the pocket complexes. This work suggests that DNA origami can selectively modulate virus infectivity.

Immunovirotherapy: The role of antibody based therapeutics combination with oncolytic viruses

Despite the fact that the new drugs and targeted therapies have been approved for cancer therapy during the past 30 years, the majority of cancer types are still remain challenging to be treated. Due to the tumor heterogeneity, immune system evasion and the complex interaction between the tumor microenvironment and immune cells, the great majority of malignancies need multimodal therapy. Unfortunately, tumors frequently develop treatment resistance, so it is important to have a variety of therapeutic choices available for the treatment of neoplastic diseases. Immunotherapy has lately shown clinical responses in malignancies with unfavorable outcomes. Oncolytic virus (OV) immunotherapy is a cancer treatment strategy that employs naturally occurring or genetically-modified viruses that multiply preferentially within cancer cells. OVs have the ability to not only induce oncolysis but also activate cells of the immune system, which in turn activates innate and adaptive anticancer responses. Despite the fact that OVs were translated into clinical trials, with T-VECs receiving FDA approval for melanoma, their use in fighting cancer faced some challenges, including off-target side effects, immune system clearance, non-specific uptake, and intratumoral spread of OVs in solid tumors. Although various strategies have been used to overcome the challenges, these strategies have not provided promising outcomes in monotherapy with OVs. In this situation, it is increasingly common to use rational combinations of immunotherapies to improve patient benefit. With the development of other aspects of cancer immunotherapy strategies, combinational therapy has been proposed to improve the anti-tumor activities of OVs. In this regard, OVs were combined with other biotherapeutic platforms, including various forms of antibodies, nanobodies, chimeric antigen receptor (CAR) T cells, and dendritic cells, to reduce the side effects of OVs and enhance their efficacy. This article reviews the promising outcomes of OVs in cancer therapy, the challenges OVs face and solutions, and their combination with other biotherapeutic agents.

Challenges and progress toward tumor-targeted therapy by systemic delivery of polymer-complexed oncolytic adenoviruses

Oncolytic adenovirus (oAd) elicits antitumor activity by preferential viral replication in cancer cells. However, poor systemic administrability or suboptimal intratumoral retainment of the virus remains a major challenge toward maximizing the antitumor activity of oAd in a clinical environment. To surmount these issues, a variety of non-immunogenic polymers has been used to modify the surface of oAds chemically or physically. Complexation of oAd with polymers can effectively evade the host immune response and reduces nonspecific liver sequestration. The tumor-specific delivery of these complexes can be further improved upon by inclusion of tumor-targeting moieties on the surface. Therefore, modification of the Ad surface using polymers is viewed as a potential strategy to enhance the delivery of Ad via systemic administration. This review aims to provide a comprehensive overview of polymer-complexed Ads, their progress, and future challenges in cancer treatment.

Strategies for Advanced Oncolytic Virotherapy: Current Technology Innovations and Clinical Approaches

Oncolytic virotherapy is a type of nanomedicine with a dual antitumor mechanism. Viruses are engineered to selectively infect and lyse cancer cells directly, leading to the release of soluble antigens which induce systemic antitumor immunity. Representative drug Talimogene laherparepvec has showed promising therapeutic effects in advanced melanoma, especially when combined with immune checkpoint inhibitors with moderate adverse effects. Diverse viruses like herpes simplex virus, adenovirus, vaccina virus, and so on could be engineered as vectors to express different transgenic payloads, vastly expanding the therapeutic potential of oncolytic virotherapy. A number of related clinical trials are under way which are mainly focusing on solid tumors. Studies about further optimizing the genome of oncolytic viruses or improving the delivering system are in the hotspot, indicating the future development of oncolytic virotherapy in the clinic. This review introduces the latest progress in clinical trials and pre-clinical studies as well as technology innovations directed at oncolytic viruses. The challenges and perspectives of oncolytic virotherapy towards clinical application are also discussed.

Immunology Meets Bioengineering: Improving the Effectiveness of Glioblastoma Immunotherapy

Glioblastoma (GBM) therapy has seen little change over the past two decades. Surgical excision followed by radiation and chemotherapy is the current gold standard treatment. Immunotherapy techniques have recently transformed many cancer treatments, and GBM is now at the forefront of immunotherapy research. GBM immunotherapy prospects are reviewed here, with an emphasis on immune checkpoint inhibitors and oncolytic viruses. Various forms of nanomaterials to enhance immunotherapy effectiveness are also discussed. For GBM treatment and immunotherapy, we outline the specific properties of nanomaterials. In addition, we provide a short overview of several 3D (bio)printing techniques and their applications in stimulating the GBM microenvironment. Lastly, the susceptibility of GBM cancer cells to the various immunotherapy methods will be addressed.

Oncolytic Viruses: Immunotherapy Drugs for Gastrointestinal Malignant Tumors

Oncolytic virus therapy has advanced rapidly in recent years. Natural or transgenic viruses can target tumor cells and inhibit tumor growth and metastasis in various ways without interfering with normal cell and tissue function. Oncolytic viruses have a high level of specificity and are relatively safe. Malignant tumors in the digestive system continue to have a high incidence and mortality rate. Although existing treatment methods have achieved some curative effects, they still require further improvement due to side effects and a lack of specificity. Many studies have shown that oncolytic viruses can kill various tumor cells, including malignant tumors in the digestive system. This review discusses how oncolytic virus therapy improves malignant tumors in the digestive system from the point-of-view of basic and clinical studies. Also, the oncolytic virus anti-tumor mechanisms underpinning the therapeutic potential of oncolytic viruses are expounded. In all, we argue that oncolytic viruses might eventually provide therapeutic solutions to malignant tumors in the digestive system.

Clinical activity of single-dose systemic oncolytic VSV virotherapy in patients with relapsed refractory T-cell lymphoma

Clinical success with intravenous (IV) oncolytic virotherapy (OV) has to-date been anecdotal. We conducted a phase 1 clinical trial of systemic OV and investigated the mechanisms of action in responding patients. A single IV dose of vesicular stomatitis virus (VSV) interferon-β (IFN-β) with sodium iodide symporter (NIS) was administered to patients with relapsed/refractory hematologic malignancies to determine safety and efficacy across 4 dose levels (DLs). Correlative studies were undertaken to evaluate viremia, virus shedding, virus replication, and immune responses. Fifteen patients received VSV-IFNβ-NIS. Three patients were treated at DL1 through DL3 (0.05, 0.17, and 0.5 × 1011 TCID50), and 6 were treated at DL4 (1.7 × 1011 TCID50) with no dose-limiting toxicities. Three of 7 patients with T-cell lymphoma (TCL) had responses: a 3-month partial response (PR) at DL2, a 6-month PR, and a complete response (CR) ongoing at 20 months at DL4. Viremia peaked at the end of infusion, g was detected. Plasma IFN-β, a biomarker of VSV-IFNβ-NIS replication, peaked between 4 hours and 48 hours after infusion. The patient with CR had robust viral replication with increased plasma cell-free DNA, high peak IFN-β of 18 213 pg/mL, a strong anti-VSV neutralizing antibody response, and increased numbers of tumor reactive T-cells. VSV-IFNβ-NIS as a single agent was effective in patients with TCL, resulting in durable disease remissions in heavily pretreated patients. Correlative analyses suggest that responses may be due to a combination of direct oncolytic tumor destruction and immune-mediated tumor control. This trial is registered at www.clinicaltrials.gov as #NCT03017820.

Oncolytic virus delivery modulated immune responses toward cancer therapy: Challenges and perspectives

Oncolytic viruses (OVs) harness the hallmarks of tumor cells and cancer-related immune responses for the lysis of malignant cells, modulation of the tumor microenvironment, and exertion of vaccine-like activities. However, efficient clinical exploitation of these potent therapeutic modules requires their systematic administration, especially against metastatic and solid tumors. Therefore, developing methods for shielding a virus from the neutralizing environment of the bloodstream while departing toward tumor sites is a must. This paper reports the latest advancements in the employment of chemical and biological compounds aimed at safe and efficient delivery of OVs to target tissues or tumor deposits within the host.

Microparticles: biogenesis, characteristics and intervention therapy for cancers in preclinical and clinical research

Extracellular vesicles (EVs), spherical biological vesicles, mainly contain nucleic acids, proteins, lipids and metabolites for biological information transfer between cells. Microparticles (MPs), a subtype of EVs, directly emerge from plasma membranes, and have gained interest in recent years. Specific cell stimulation conditions, such as ultraviolet and X-rays irradiation, can induce the release of MPs, which are endowed with unique antitumor functionalities, either for therapeutic vaccines or as direct antitumor agents. Moreover, the size of MPs (100–1000 nm) and their spherical structures surrounded by a lipid bilayer membrane allow MPs to function as delivery vectors for bioactive antitumor compounds, with favorable phamacokinetic behavior, immunostimulatory activity and biological function, without inherent carrier-specific toxic side effects. In this review, the mechanisms underlying MP biogenesis, factors that influence MP production, properties of MP membranes, size, composition and isolation methods of MPs are discussed. Additionally, the applications and mechanisms of action of MPs, as well as the main hurdles for their applications in cancer management, are introduced.

Nanobugs as Drugs: Bacterial Derived Nanomagnets Enhance Tumor Targeting and Oncolytic Activity of HSV-1 Virus

The survival strategies of infectious organisms have inspired many therapeutics over the years. Indeed the advent of oncolytic viruses (OVs) exploits the uncontrolled replication of cancer cells for production of their progeny resulting in a cancer-targeting treatment that leaves healthy cells unharmed. Their success against inaccessible tumors however, is highly variable due to inadequate tumor targeting following systemic administration. Coassembling herpes simplex virus (HSV1716) with biocompatible magnetic nanoparticles derived from magnetotactic bacteria enables tumor targeting from circulation with magnetic guidance, protects the virus against neutralizing antibodies and thereby enhances viral replication within tumors. This approach additionally enhances the intratumoral recruitment of activated immune cells, promotes antitumor immunity and immune cell death, thereby inducing tumor shrinkage and increasing survival in a syngeneic mouse model of breast cancer by 50%. Exploiting the properties of such a nanocarrier, rather than tropism of the virus, for active tumor targeting offers an exciting, novel approach for enhancing the bioavailability and treatment efficacy of tumor immunotherapies for disseminated neoplasms.

Transplantation of autologous bone marrow pre-loaded ex vivo with oncolytic myxoma virus is efficacious against drug-resistant Vk*MYC mouse myeloma

Multiple myeloma (MM) is a hematological malignancy of plasma cells that remains incurable despite significant progress with myeloablative regimens and autologous stem cell transplantation for eligible patients and, more recently with T cell redirected immunotherapy. Recently, we reported that ex vivo virotherapy with oncolytic myxoma virus (MYXV) improved MM-free survival in an autologous-transplant Balb/c mouse model. Here, we tested the Vk*MYC transplantable C57BL/6 mouse MM model that more closely recapitulates human disease. In vitro, the murine bortezomib-resistant Vk12598 cell line is fully susceptible to MYXV infection. In vivo results demonstrate: (i) autologous bone marrow (BM) leukocytes armed ex vivo with MYXV exhibit moderate therapeutic effects against MM cells pre-seeded into recipient mice; (ii) Cyclophosphamide in combination with BM/MYXV delays the onset of myeloma in mice seeded with Vk12598 cells; (iii) BM/MYXV synergizes with the Smac-mimetics LCL161 and with immune checkpoint inhibitor α-PD-1 to control the progression of established MM in vivo, resulting in significant improvement of survival rates and decreased of tumor burden; (iv) Survivor mice from (ii) and (iii), when re-challenged with fresh Vk12598 cells, developed acquired anti-MM immunity. These results highlight the utility of autologous BM grafts armed ex vivo with oncolytic MYXV alone or in combination with chemotherapy/immunotherapy to treat drug-resistant MM in vivo.

The Landscape of Nanovectors for Modulation in Cancer Immunotherapy

Immunotherapy represents a promising strategy for the treatment of cancer, which functions via the reprogramming and activation of antitumor immunity. However, adverse events resulting from immunotherapy that are related to the low specificity of tumor cell-targeting represent a limitation of immunotherapy's efficacy. The potential of nanotechnologies is represented by the possibilities of immunotherapeutical agents being carried by nanoparticles with various material types, shapes, sizes, coated ligands, associated loading methods, hydrophilicities, elasticities, and biocompatibilities. In this review, the principal types of nanovectors (nanopharmaceutics and bioinspired nanoparticles) are summarized along with the shortcomings in nanoparticle delivery and the main factors that modulate efficacy (the EPR effect, protein coronas, and microbiota). The mechanisms by which nanovectors can target cancer cells, the tumor immune microenvironment (TIME), and the peripheral immune system are also presented. A possible mathematical model for the cellular communication mechanisms related to exosomes as nanocarriers is proposed.

Giving Oncolytic Viruses a Free Ride: Carrier Cells for Oncolytic Virotherapy

Oncolytic viruses (OVs) are an emerging class of therapeutics which combine multiple mechanisms of action, including direct cancer cell-killing, immunotherapy and gene therapy. A growing number of clinical trials have indicated that OVs have an excellent safety profile and provide some degree of efficacy, but to date only a single OV drug, HSV-1 talimogene laherparepvec (T-Vec), has achieved marketing approval in the US and Europe. An important issue to consider in order to accelerate the clinical advancement of OV agents is the development of an effective delivery system. Currently, the most commonly employed OV delivery route is intratumoral; however, to target metastatic diseases and tumors that cannot be directly accessed, it is of great interest to develop effective approaches for the systemic delivery of OVs, such as the use of carrier cells. In general, the ideal carrier cell should have a tropism towards the tumor microenvironment (TME), and it must be susceptible to OV infection but remain viable long enough to allow migration and finally release of the OV within the tumor bed. Mesenchymal stem cells (MSCs) have been heavily investigated as carrier cells due to their inherent tumor tropism, in spite of some disadvantages in biodistribution. This review focuses on the other promising candidate carrier cells under development and discusses their interaction with specific OVs and future research lines.