Oncolytic Viral Therapy and the Immune System: A Double-Edged Sword Against Cancer

Advancing glioblastoma therapy: Learning from the past and innovations for the future

Marred by a median survival of only around 12-15 months coupled with poor prognosis and effective therapeutic deprived drug armory, treatment/management of glioblastoma has proved to be a daunting task. Surgical resection, flanked by radiotherapy and chemotherapy with temozolomide, stands as the standard of care; however, this trimodal therapy often manifests limited efficacy due to the heterogeneous and highly infiltrative nature of GBM cells. In addition, the existence of the blood-brain barrier, tumor microenvironment, and the immunosuppressive nature of GBM, along with the encountered resistance of GBM cells towards conventional therapy, also hinders the therapeutic applications of chemotherapeutics in GBM. This review presents key insights into the molecular pathology of GBM, including genetic mutations, signaling pathways, and tumor microenvironment characteristics. Recent innovations such as immunotherapy, oncolytic viral therapies, vaccines, nanotechnology, electric field, and cancer neuroscience, as well as their clinical progress, have been covered. In addition, this compilation also encompasses a discussion on the role of personalized medicine in tailoring treatments based on individual tumor profiles, an approach that is gradually shifting the paradigm in GBM management. Endowed with the learnings imbibed from past failures coupled with the zeal to embrace novel/multidisciplinary approaches, researchers appear to be on the right track to pinpoint more effective and durable solutions in the context of GBM treatment.

Neoantigen-based immunotherapy: advancing precision medicine in cancer and glioblastoma treatment through discovery and innovation

Neoantigen-based immunotherapy has emerged as a transformative approach in cancer treatment, offering precision medicine strategies that target tumor-specific antigens derived from genetic, transcriptomic, and proteomic alterations unique to cancer cells. These neoantigens serve as highly specific targets for personalized therapies, promising more effective and tailored treatments. The aim of this article is to explore the advances in neoantigen-based therapies, highlighting successful treatments such as vaccines, tumor-infiltrating lymphocyte (TIL) therapy, T-cell receptor-engineered T cells therapy (TCR-T), and chimeric antigen receptor T cells therapy (CAR-T), particularly in cancer types like glioblastoma (GBM). Advances in technologies such as next-generation sequencing, RNA-based platforms, and CRISPR gene editing have accelerated the identification and validation of neoantigens, moving them closer to clinical application. Despite promising results, challenges such as tumor heterogeneity, immune evasion, and resistance mechanisms persist. The integration of AI-driven tools and multi-omic data has refined neoantigen discovery, while combination therapies are being developed to address issues like immune suppression and scalability. Additionally, the article discusses the ongoing development of personalized immunotherapies targeting tumor mutations, emphasizing the need for continued collaboration between computational and experimental approaches. Ultimately, the integration of cutting-edge technologies in neoantigen research holds the potential to revolutionize cancer care, offering hope for more effective and targeted treatments.

Expression of SIRPα-Fc by oncolytic virus enhances antitumor efficacy through tumor microenvironment reprogramming

Oncolytic viruses (OVs) selectively replicate within tumors, directly killing cancer cells and promoting a systemic immune response by releasing tumor antigens. These features make OVs a promising approach in tumor immunotherapy, offering targeted treatment with fewer side effects. Despite these advantages, OVs are primarily administered via intratumoral injection, limiting their effectiveness for advanced, systemic cancers. Among OVs, oncolytic adenoviruses (oAdVs) are the most widely studied due to their well-understood gene regulation, safety, and stability. In this study, a modified oAdV vector, pDC316-oAd-SA, was engineered to express the SIRPα-mIgG1Fc gene, designed to remodel tumor-associated macrophages (TAMs) and enhance anti-tumor immunity. This vector, along with a control virus (Ad-ON), was evaluated both in vitro and in vivo. The modified oAd-SA significantly improved macrophage phagocytosis and showed superior tumor regression in murine models. Additionally, while both oAdVs increased T cell infiltration in the tumor microenvironment, oAd-SA specifically enhanced T cell immune function. The study also revealed that oAdVs modulate TAMs differently across tumor types, with oAd-SA therapy particularly increasing TAM phagocytosis and promoting an anti-tumor response.

Advances in preclinical and clinical studies of oncolytic virus combination therapy

Oncolytic viruses represent a distinct class of viruses that selectively infect and destroy tumor cells while sparing normal cells. Despite their potential, oncolytic viruses encounter several challenges as standalone therapies. Consequently, the combination of oncolytic viruses with other therapeutic modalities has emerged as a prominent research focus. This paper summarizes the tumor-killing mechanisms of oncolytic viruses, explores their integration with radiotherapy, chemotherapy, immune checkpoint inhibitors, CAR-T, and CAR-NK therapies, and provides an overview of related clinical trials. By synthesizing these advancements, this study seeks to offer valuable insights for the clinical translation of oncolytic virus combination therapies.

Neoadjuvant immunotherapy and oncolytic virotherapy in HPV positive and HPV negative skin cancer: A comprehensive review

Skin cancer is the most common new cancer among Caucasians. This cancer has different types, of which non-melanoma skin cancer is the most common type. Various factors affect this disease, one of which is viral infections, including HPV. This virus plays an important role in skin cancer, especially cSCCs. There are various options for the treatment of skin cancer, and today special attention has been paid to treatments based on therapeutic goals, immunotherapy and combination therapy. In this study, we have investigated treatments based on immunotherapy and virotherapy and the effect of HPV virus on the effectiveness of these treatments in skin cancer. Treatments based on virotherapy are performed for a long time in combination with other common treatments such as radiotherapy and chemotherapy in order to have a greater effect and lower its side effects, which include: shortness of breath, tachycardia, lowering blood pressure in the patient. Also, the most important axis of immunotherapy is to focus on PD1-PDL1, despite abundant evidence on the importance of immunotherapy, many studies investigate the use of immunotherapy inhibitors in the adjuvant and neoadjuvant setting in various cancers. Also, previous findings show conflicting evidence of the effect of HPV status on the response to immunotherapy.

SMAC-armed oncolytic virotherapy enhances the anticancer activity of PD1 blockade by modulating PANoptosis

BACKGROUND

Oncolytic viruses (OVs) are increasingly recognized as promising tools for cancer therapy, as they selectively infect and destroy tumor cells while leaving healthy cells unharmed. Despite considerable progress, the limited therapeutic efficacy of OV-based virotherapy continues to be a significant challenge in cancer treatment.

METHODS

The SMAC/DIABLO gene was inserted into the genome of vesicular stomatitis virus (VSV) to generate VSV-S. Head and neck squamous cell carcinoma (HNSCC) cell lines and orthotopic mouse models were employed for research. Morphological changes were observed using both light microscopy and transmission electron microscopy. Molecular alterations were analyzed through Western blotting and ELISA kits. The tumor secretome was characterized using a combination of biotinylation and LC-MS analysis. Immune cell changes were evaluated by flow cytometry and immunohistochemistry.

RESULTS

Compared to its parental virus, VSV-S not only increases apoptosis by overexpressing SMAC during VSV infection but also triggers elevated levels of PANoptosis (pyroptosis, apoptosis, and necroptosis) in HNSCC cells via activation of caspase-1/gasdermin D (GSDMD) signaling. As a result, VSV-S-induced PANoptosis promotes CD8+ T cell tumor infiltration and enhances their cytotoxic capacity, eventually potentiating T cell-mediated antitumor immunity. Moreover, VSV-S reduces PDL1 levels in HNSCC cells and, in combination with PD1 blockade, produces a more potent antitumor effect than either therapy alone.

CONCLUSIONS

Our findings demonstrate that the combination of VSV-S and PD1 blockade offers a synergistic therapeutic strategy for HNSCC, supporting the advancement of VSV-based virotherapy as a promising strategy to improve outcomes for HNSCC patients.

CAR-T cell therapy: developments, challenges and expanded applications from cancer to autoimmunity

Chimeric Antigen Receptor (CAR)-T cell therapy has rapidly emerged as a groundbreaking approach in cancer treatment, particularly for hematologic malignancies. However, the application of CAR-T cell therapy in solid tumors remains challenging. This review summarized the development of CAR-T technologies, emphasized the challenges and solutions in CAR-T cell therapy for solid tumors. Also, key innovations were discussed including specialized CAR-T, combination therapies and the novel use of CAR-Treg, CAR-NK and CAR-M cells. Besides, CAR-based cell therapy have extended its reach beyond oncology to autoimmune disorders. We reviewed preclinical experiments and clinical trials involving CAR-T, Car-Treg and CAAR-T cell therapies in various autoimmune diseases. By highlighting these cutting-edge developments, this review underscores the transformative potential of CAR technologies in clinical practice.

Emerging combined CAR-NK cell therapies in cancer treatment: Finding a dancing partner

In recent decades, immunotherapy with chimeric antigen receptors (CARs) has revolutionized cancer treatment and given hope where other cancer therapies have failed. CAR-natural killer (NK) cells are NK cells that have been engineered ex vivo with a CAR on the cell membrane with high specificity for specific target antigens of tumor cells. The impressive results of several studies suggest that CAR-NK cell therapy has significant potential and successful performance in cancer treatment. Despite its effectiveness, CAR-NK cell therapy can have significant challenges when it comes to treating cancer. These challenges include tumor heterogeneity, antigen escape, an immunosuppressive tumor microenvironment, limited tissue migration from blood, exhaustion of CAR-NK cells, and inhibition by immunosuppressive checkpoint molecule signaling, etc. In CAR-T cell therapy, the use of combined approaches has shown encouraging outcomes for tumor regression and improved cancer treatment compared to single therapies. Therefore, to overcome these significant challenges in CAR-NK cells, innovative combination therapies of CAR-NK cells with other conventional therapies (e.g., chemotherapy and radiotherapy) or other immunotherapies are needed to counteract the above challenges and thereby increase the activity of CAR-NK cells. This review comprehensively discusses various cancer-treatment approaches in combination with CAR-NK cell therapy in the hope of providing valuable insights that may improve cancer treatment in the near future.

The Potential of Oncolytic Virotherapy in the Treatment of Head and Neck Cancer: A Comprehensive Review

Head and neck cancer (HNC) represents a challenging oncological entity with significant morbidity and mortality rates. Despite advances in conventional therapies, including surgery, chemotherapy, and radiation therapy, the overall survival rates for advanced HNC remain suboptimal. In recent years, the emerging field of oncolytic virotherapy has gained attention as a promising therapeutic approach for various malignancies, including HNC. This review provides a comprehensive overview of the current understanding of oncolytic viruses (Ovs) in the context of HNC treatment, including their mechanisms of action, preclinical and clinical studies, challenges, and future directions. Future oncolytic virotherapy focuses on improving delivery and specificity through nanoparticle carriers and genetic modifications to enhance tumor targeting and immune response. Combining different OVs and integrating them with immunotherapies, such as checkpoint inhibitors, could overcome tumor resistance and improve outcomes. Personalized approaches and rigorous clinical trials are key to ensuring the safety and effectiveness of virotherapy in treating HNC.

An in silico approach uncovering the competency of oncolytic human adenovirus 52 for targeted breast cancer virotherapy

Breast cancer remains a major health threat throughout the world specifically in women above 30 years of age however, it is rarely known to affect men as well. It is characterized by the abnormal division of cells in the breast tissue resulting in the development of breast malignancies. Various risk factors contributing to breast cancer include age, family history, genetic mutations (chiefly in BRCA1 and BRCA2 genes) along with hormonal imbalances (oestrogen, progesterone, HER2). Early detection which can be obtained through frequent rounds of self-examination, mammographic scanning, and clinical assessment plays a crucial role in the prevention of the disease. In addition, appropriate diagnosis assists in better therapeutic responses. This study highlights the considerable health risks associated with the conventional treatment procedures which arise and increased demand of advanced, secure, and risk-free treatment alternatives. Oncolytic viruses are potentially apparent for the aim of improving cancer therapeutics with reduced side effects. These viruses act as the fundamental therapeutic agent themselves that selectively target and kill malignant cells without harm to healthy tissues. The key objective of the research is to provide evidence that Human Adenovirus 52 is a potent oncolytic virus and to highlight its capacity to target and eliminate cancer cells with precision while causing the least amount of harm to healthy tissues. Validating the in-silico method entails evaluating the precision and dependability of the computational modelling by contrasting the in-silico predictions with the findings from the experiments rank as the secondary objective. The workflow of this research utilized in-silico computational drug designing approaches including retrieval of tertiary structures of both the target Breast Cancer Type 1 Susceptibility Protein (BRCA1) and the viral Human Adenovirus 52 protein, their validation generating Ramachandran Plots determining favoured amino acid residue angles and prediction of their active residues. Furthermore, the study focused on the molecular dynamics docking of proteins, interpretation of molecular interactions between the docked complex, as well as the assessment of the molecular dynamic simulations (MD) in addition to their MMGBSA binding energy calculations. A successful docking between BRCA1 and Adenovirus protein provided a significant score of 329.2 +/- 24.3, furthermore, MD simulations showed a high RMSD peak at 2.8 Å, RMSF were maximum at 3.5 Å with highest protein-protein interaction, the radius of gyration was stable throughout the simulation representing elastic stability along with a high energy interaction value of - 7882 kCal/mol. Moreover, the MMGBSA calculation results showed a notable release of binding free energy of - 68.96 kCal/mol demonstrating effective bond formation between the docked complex. These findings propose the effectiveness of Human Adenovirus 52 to treat cancer. The selected oncolytic Human Adenovirus 52 is a potential candidate for the target specific treatment of breast cancer through virotherapy. This computer-aided drug discovery presents significant potential in targeting cancer cells and would assist in the development of potent drug reagents for the cancer therapy.

Advances of immune-checkpoint inhibition of CTLA-4 in pancreatic cancer

Targeting checkpoints for immune cell activation has been acknowledged known as one of the most effective way to activate anti-tumor immune responses. Among them, drugs targeting cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) are approved for clinical treatment though several more are in advanced stages of development, which demonstrated durable response rates and manageable safety profile. However, its therapy efficacy is unsatisfactory in pancreatic cancer (PC), which can be limited by the overall condition of patients, the pathological type of PC, the expression level of tumor related genes, etc. To improve clinical efficiency, various researches have been conducted, and the efficacy of combination therapy showed significantly improvement compared to monotherapy. This review analyzed current strategies based on anti-CTLA-4 combination immunotherapy, providing totally new idea for future research.

Progression of oncolytic virus in liver cancer treatment

The liver plays a crucrial role in detoxification, metabolism, and nutrient storage. Because liver cancer ranks among the top three leading causes of death globally, there is an urgent need for developing treatment strategies for liver cancer. Although traditional approaches such as radiation, chemotherapy, surgical removal, and transplantation are widely practiced, the number of patients with liver cancer continues to increase rapidly each year. Some novel therapeutics for liver cancer have been studied for many years. In the past decade, oncolytic therapy has emerged, in which viruses selectively infect and destroy cancer cells while sparing normal cells. However, oncolytic virotherapy for liver cancer remains relatively obscure due to the aggressive nature of the disease and the limited effectiveness of treatment. To keep pace with the latest developments in oncolytic tumor therapy for liver cancer, this review summarizes basic science studies and clinical trials conducted within 5 years, focusing on the efficacy and safety profiles of the five most commonly used oncolytic viruses: herpes simplex virus, adenovirus, influenza virus, vaccinia virus, and coxsackievirus.

Optimizing Pancreatic Cancer Therapy: The Promise of Immune Stimulatory Oncolytic Viruses

Pancreatic cancer presents formidable challenges due to rapid progression and resistance to conventional treatments. Oncolytic viruses (OVs) selectively infect cancer cells and cause cancer cells to lyse, releasing molecules that can be identified by the host's immune system. Moreover, OV can carry immune-stimulatory payloads such as interleukin-12, which when delivered locally can enhance immune system-mediated tumor killing. OVs are very well tolerated by cancer patients due to their ability to selectively target tumors without affecting surrounding normal tissues. OVs have recently been combined with other therapies, including chemotherapy and immunotherapy, to improve clinical outcomes. Several OVs including adenovirus, herpes simplex viruses (HSVs), vaccinia virus, parvovirus, reovirus, and measles virus have been evaluated in preclinical and clinical settings for the treatment of pancreatic cancer. We evaluated the safety and tolerability of a replication-competent oncolytic adenoviral vector carrying two suicide genes (thymidine kinase, TK; and cytosine deaminase, CD) and human interleukin-12 (hIL12) in metastatic pancreatic cancer patients in a phase 1 trial. This vector was found to be safe and well-tolerated at the highest doses tested without causing any significant adverse events (SAEs). Moreover, long-term follow-up studies indicated an increase in the overall survival (OS) in subjects receiving the highest dose of the OV. Our encouraging long-term survival data provide hope for patients with advanced pancreatic cancer, a disease that has not seen a meaningful increase in OS in the last five decades. In this review article, we highlight several preclinical and clinical studies and discuss future directions for optimizing OV therapy in pancreatic cancer. We envision OV-based gene therapy to be a game changer in the near future with the advent of newer generation OVs that have higher specificity and selectivity combined with personalized treatment plans developed under AI guidance.

Where Are We Now with Oncolytic Viruses in Melanoma and Nonmelanoma Skin Malignancies?

Skin cancer prognosis has greatly improved recently due to the introduction of immune checkpoint inhibitors (ICIs). However, many patients with advanced skin cancer still experience immunotherapy resistance and disease progression during ICI treatment, thus calling for novel therapeutics which address this treatment gap. Talimogene laherparepvec (T-VEC) has gained popularity in recent years as a viable treatment option for patients with skin cancer. In preclinical studies, T-VEC demonstrated both a direct anti-tumor effect in injected lesions as well as a systemic immune-mediated effect in non-injected lesions, which could pose additional benefits when combined with ICI therapy. Following promising results from the OPTiM trial, the Food and Drug Administration (FDA) approved the usage of T-VEC as a single agent in advanced melanoma. However, the MASTERKEY-265 trial demonstrated that adding T-VEC to pembrolizumab did not offer additional clinical benefit in patients with melanoma. Nevertheless, the promising efficacy of T-VEC and its approval by the FDA helped oncolytic viruses (OVs) gain wide attention in cancer therapy, and extensive research has been undertaken to evaluate the usage of OVs in other tumors such as sarcomas and breast cancers. Here, we provide a review of clinical results from 2022 to 2024 that investigate the efficacy and safety of OVs as a monotherapy or in combination with other therapies in skin malignancies. Furthermore, we delineate the current limitations in OV utilization and outline future directions to enhance clinical outcomes for patients with skin malignancies receiving OV-based therapies.

The Immune System-A Double-Edged Sword for Adenovirus-Based Therapies

Pathogenic adenovirus (Ad) infections are widespread but typically mild and transient, except in the immunocompromised. As vectors for gene therapy, vaccine, and oncology applications, Ad-based platforms offer advantages, including ease of genetic manipulation, scale of production, and well-established safety profiles, making them attractive tools for therapeutic development. However, the immune system often poses a significant challenge that must be overcome for adenovirus-based therapies to be truly efficacious. Both pre-existing anti-Ad immunity in the population as well as the rapid development of an immune response against engineered adenoviral vectors can have detrimental effects on the downstream impact of an adenovirus-based therapeutic. This review focuses on the different challenges posed, including pre-existing natural immunity and anti-vector immunity induced by a therapeutic, in the context of innate and adaptive immune responses. We summarise different approaches developed with the aim of tackling these problems, as well as their outcomes and potential future applications.

The role of immune cells in resistance to oncolytic viral therapy

Resistance to treatment poses a major challenge for cancer therapy, and oncoviral treatment encounters the issue of viral resistance as well. In this investigation, we introduce deterministic differential equation models to explore the effect of resistance on oncolytic viral therapy. Specifically, we classify tumor cells into resistant, sensitive, or infected with respect to oncolytic viruses for our analysis. Immune cells can eliminate both tumor cells and viruses. Our research shows that the introduction of immune cells into the tumor-virus interaction prevents all tumor cells from becoming resistant in the absence of conversion from resistance to sensitivity, given that the proliferation rate of immune cells exceeds their death rate. The inclusion of immune cells leads to an additional virus-free equilibrium when the immune cell recruitment rate is sufficiently high. The total tumor burden at this virus-free equilibrium is smaller than that at the virus-free and immune-free equilibrium. Therefore, immune cells are capable of reducing the tumor load under the condition of sufficient immune strength. Numerical investigations reveal that the virus transmission rate and parameters related to the immune response significantly impact treatment outcomes. However, monotherapy alone is insufficient for eradicating tumor cells, necessitating the implementation of additional therapies. Further numerical simulation shows that combination therapy with chimeric antigen receptor (CAR T-cell) therapy can enhance the success of treatment.

Combination therapy with oncolytic virus and T cells or mRNA vaccine amplifies antitumor effects

Antitumor therapies based on adoptively transferred T cells or oncolytic viruses have made significant progress in recent years, but the limited efficiency of their infiltration into solid tumors makes it difficult to achieve desired antitumor effects when used alone. In this study, an oncolytic virus (rVSV-LCMVG) that is not prone to induce virus-neutralizing antibodies was designed and combined with adoptively transferred T cells. By transforming the immunosuppressive tumor microenvironment into an immunosensitive one, in B16 tumor-bearing mice, combination therapy showed superior antitumor effects than monotherapy. This occurred whether the OV was administered intratumorally or intravenously. Combination therapy significantly increased cytokine and chemokine levels within tumors and recruited CD8+ T cells to the TME to trigger antitumor immune responses. Pretreatment with adoptively transferred T cells and subsequent oncolytic virotherapy sensitizes refractory tumors by boosting T-cell recruitment, down-regulating the expression of PD-1, and restoring effector T-cell function. To offer a combination therapy with greater translational value, mRNA vaccines were introduced to induce tumor-specific T cells instead of adoptively transferred T cells. The combination of OVs and mRNA vaccine also displays a significant reduction in tumor burden and prolonged survival. This study proposed a rational combination therapy of OVs with adoptive T-cell transfer or mRNA vaccines encoding tumor-associated antigens, in terms of synergistic efficacy and mechanism.

Oncolytic viral therapy for gliomas: Advances in the mechanisms and approaches to delivery

Glioma is a diverse category of tumors originating from glial cells encompasses various subtypes, based on the specific type of glial cells involved. The most aggressive is glioblastoma multiforme (GBM), which stands as the predominant primary malignant tumor within the central nervous system in adults. Despite the application of treatment strategy, the median survival rate for GBM patients still hovers around 15 months. Oncolytic viruses (OVs) are artificially engineered viruses designed to selectively target and induce apoptosis in cancer cells. While clinical trials have demonstrated encouraging results with intratumoral OV injections for some cancers, applying this approach to GBM presents unique challenges. Here we elaborate on current trends in oncolytic viral therapy and their delivery methods. We delve into the various methods of delivering OVs for therapy, exploring their respective advantages and disadvantages and discussing how selecting the optimal delivery method can enhance the efficacy of this innovative treatment approach.

Viruses in glioblastoma: an update on evidence and clinical trials

BACKGROUND

Glioblastoma (GB) is a lethal and aggressive brain tumour. While molecular characteristics of GB is studied extensively, the aetiology of GB remains uncertain. The interest in exploring viruses as a potential contributor to the development of GB stems from the notion that viruses are known to play a key role in pathogenesis of other human cancers such as cervical cancer. Nevertheless, the role of viruses in GB remains controversial.

METHODS

This review delves into the current body of knowledge surrounding the presence of viruses in GB as well as provide updates on clinical trials examining the potential inclusion of antiviral therapies as part of the standard of care protocol.

CONCLUSIONS

The review summarises current evidences and important gaps in our knowledge related to the presence of viruses in GB.

Mesenchymal-Stem-Cell-Based Therapy against Gliomas

Glioblastoma is the most aggressive, malignant, and lethal brain tumor of the central nervous system. Its poor prognosis lies in its inefficient response to currently available treatments that consist of surgical resection, radiotherapy, and chemotherapy. Recently, the use of mesenchymal stem cells (MSCs) as a possible kind of cell therapy against glioblastoma is gaining great interest due to their immunomodulatory properties, tumor tropism, and differentiation into other cell types. However, MSCs seem to present both antitumor and pro-tumor properties depending on the tissue from which they come. In this work, the possibility of using MSCs to deliver therapeutic genes, oncolytic viruses, and miRNA is presented, as well as strategies that can improve their therapeutic efficacy against glioblastoma, such as CAR-T cells, nanoparticles, and exosomes.

The NDV-MLS as an Immunotherapeutic Strategy for Breast Cancer: Proof of Concept in Female Companion Dogs with Spontaneous Mammary Cancer

The absence of tumor-infiltrating lymphocytes negatively impacts the response to chemotherapy and prognosis in all subtypes of breast cancer. Therapies that stimulate a proinflammatory environment may help improve the response to standard treatments and also to immunotherapies such as checkpoint inhibitors. Newcastle disease virus (NDV) shows oncolytic activity, as well as immune modulating potential, in the treatment of breast cancer in vitro and in vivo; however, its potential to enhance tumor-infiltrating immune cells in breast cancer has yet to be evaluated. Since spontaneous canine mammary tumors represent a translational model of human breast cancer, we conducted this proof-of-concept study, which could provide a rationale for further investigating NDV-MLS as immunotherapy for mammary cancer. Six female companion dogs with spontaneous mammary cancer received a single intravenous and intratumoral injection of oncolytic NDV-MLS. Immune cell infiltrates were evaluated by histology and immunohistochemistry in the stromal, intratumoral, and peritumoral compartments on day 6 after viral administration. Increasing numbers of immune cells were documented post-viral treatment, mainly in the peritumoral compartment, where plasma cells and CD3+ and CD3-/CD79- lymphocytes predominated. Viral administration was well tolerated, with no significant adverse events. These findings support additional research on the use of NDV-MLS immunotherapy for mammary cancer.

Optimal strategies of oncolytic virus-bortezomib therapy via the apoptotic, necroptotic, and oncolysis signaling network

Bortezomib and oncolytic virotherapy are two emerging targeted cancer therapies. Bortezomib, a proteasome inhibitor, disrupts protein degradation in cells, leading to the accumulation of unfolded proteins that induce apoptosis. On the other hand, virotherapy uses genetically modified oncolytic viruses (OVs) to infect cancer cells, trigger cell lysis, and activate anti-tumor response. Despite progress in cancer treatment, identifying administration protocols for therapeutic agents remains a significant concern, aiming to strike a balance between efficacy, minimizing toxicity, and administrative costs. In this work, optimal control theory was employed to design a cost-effective and efficient co-administration protocols for bortezomib and OVs that could significantly diminish the population of cancer cells via the cell death program with the NF$ \kappa $B-BAX-RIP1 signaling network. Both linear and quadratic control strategies were explored to obtain practical treatment approaches by adapting necroptosis protocols to efficient cell death programs. Our findings demonstrated that a combination therapy commencing with the administration of OVs followed by bortezomib infusions yields an effective tumor-killing outcome. These results could provide valuable guidance for the development of clinical administration protocols in cancer treatment.

Synergistic Viro-chemoimmunotherapy in Breast Cancer Enabled by Bioengineered Immunostimulatory Exosomes and Dual-Targeted Coxsackievirus B3

Breast cancer's immunosuppressive environment hinders effective immunotherapy, but oncolytic viruses hold promise for addressing this challenge by targeting tumor cells and altering the microenvironment. Yet, neutralizing antibodies and immune clearance impede their clinical utility. This study explored microRNA-modified coxsackievirus B3 (miR-CVB3), an innovative oncolytic virus, and its potential in breast cancer treatment. It investigated miR-CVB3's impact on immune-related proteins and utilized exosomes as both protective shields and delivery carriers. Results demonstrated miR-CVB3's capacity to reshape immune-related protein profiles toward a more immunostimulatory state and enhance exosome-mediated immune cell activation. Notably, cancer cell-released exosomes encapsulating miR-CVB3 (ExomiR-CVB3) maintained its antitumor cytotoxicity and bolstered its immunostimulatory effects. Moreover, ExomiR-CVB3 shielded miR-CVB3 from neutralizing antibodies and rapid immune clearance when it was systemically administered. Building on these findings, ExomiR-CVB3 was engineered with the AS1411 aptamer and doxorubicin (ExomiR-CVB3/DoxApt), enhancing therapeutic efficacy. This notable approach, combining genomic modification, aptamer surface decoration, and doxorubicin addition, demonstrated safe delivery of CVB3 to cancer cells. Comprehensive in vitro and in vivo analyses revealed selective breast cancer cell targeting, cell death induction, and significant immune cell infiltration within the tumor microenvironment while sparing healthy organs. In summary, this study highlights ExomiR-CVB3/DoxApt as a pioneering breast cancer treatment strategy adaptable for diverse cancer types, offering a potent and versatile approach to reshaping cancer immunotherapy.

HIV-Encoded Gene Therapy as Anti-cancer Therapeutics: A Narrative Review

Recently, there has been interest in using viruses as cancer treatments. Oncolytic virology was founded by scientists who noticed that viruses might preferentially lyse cancer cells over healthy ones. Oncolytic virotherapy has similar obstacles as other treatment approaches, gaining entry into the specific tumour cell, encountering antiviral immune responses, off-target infection and many other unfavourable circumstances in the tumour microenvironment, and a lack of unique therapeutic and predictive biomarkers. However, oncolytic viruses have emerged as the main players in the biological treatment for cancer with the use of vectors such as human adenoviruses in oncolytic virotherapy. Recent large-scale research has shown that other viruses, such as the measles virus and the herpes simplex virus (HSV), may potentially be viable options for cancer treatment. The FDA has cleared T-VEC, an HSV-based oncolytic virus, for use in biological cancer treatment after its successful completion of human clinical trials. Furthermore, the measles virus vaccine strain has shown remarkable outcomes in pre-clinical and clinical testing. The use of such modified viruses in biological cancer treatment holds promise for groundbreaking discoveries in the field of cancer research because of their therapeutic effectiveness, fewer side effects, and safety. Several other newer approaches have been used in recent years. HIV-encoded proteins are also hypothesized to promote mitochondrial homeostasis causing bystander-induced apoptosis. We provide an overview of the most recent developments in the clinical use of oncolytic virus-based biological cancer treatment in this study. This evaluation also assesses the advantages and disadvantages of the viral candidates and provides insight into their potential in the future.

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.

Targeting Innate Immunity in Glioma Therapy

Currently, there is a lack of effective therapies for the majority of glioblastomas (GBMs), the most common and malignant primary brain tumor. While immunotherapies have shown promise in treating various types of cancers, they have had limited success in improving the overall survival of GBM patients. Therefore, advancing GBM treatment requires a deeper understanding of the molecular and cellular mechanisms that cause resistance to immunotherapy. Further insights into the innate immune response are crucial for developing more potent treatments for brain tumors. Our review provides a brief overview of innate immunity. In addition, we provide a discussion of current therapies aimed at boosting the innate immunity in gliomas. These approaches encompass strategies to activate Toll-like receptors, induce stress responses, enhance the innate immune response, leverage interferon type-I therapy, therapeutic antibodies, immune checkpoint antibodies, natural killer (NK) cells, and oncolytic virotherapy, and manipulate the microbiome. Both preclinical and clinical studies indicate that a better understanding of the mechanisms governing the innate immune response in GBM could enhance immunotherapy and reinforce the effects of chemotherapy and radiotherapy. Consequently, a more comprehensive understanding of the innate immune response against cancer should lead to better prognoses and increased overall survival for GBM patients.

Oncolytic vaccinia virus and cancer immunotherapy

Oncolytic virotherapy (OVT) is a promising form of cancer treatment that uses genetically engineered viruses to replicate within cancer cells and trigger anti-tumor immune response. In addition to killing cancer cells, oncolytic viruses can also remodel the tumor microenvironment and stimulate a long-term anti-tumor immune response. Despite achieving positive results in cellular and organismal studies, there are currently only a few approved oncolytic viruses for clinical use. Vaccinia virus (VACV) has emerged as a potential candidate due to its ability to infect a wide range of cancer cells. This review discusses the mechanisms, benefits, and clinical trials of oncolytic VACVs. The safety and efficacy of different viral backbones are explored, as well as the effects of oncolytic VACVs on the tumor microenvironment. The potential combination of oncolytic VACVs with immunotherapy or traditional therapies is also highlighted. The review concludes by addressing prospects and challenges in the field of oncolytic VACVs, with the aim of promoting further research and application in cancer therapy.

Breaking Barriers: A Future Perspective on Glioblastoma Therapy with mRNA-Based Immunotherapies and Oncolytic Viruses

The use of mRNA-based immunotherapies that leverage the genomes of oncolytic viruses holds significant promise in addressing glioblastoma (GBM), an exceptionally aggressive neurological tumor. We explore the significance of mRNA-based platforms in the area of immunotherapy, introducing an innovative approach to mitigate the risks associated with the use of live viruses in cancer treatment. The ability to customize oncolytic virus genome sequences enables researchers to precisely target specific cancer cells, either through viral genome segments containing structural proteins or through a combination of regions with oncolytic potential. This strategy may enhance treatment effectiveness while minimizing unintended impacts on non-cancerous cells. A notable case highlighted here pertains to advanced findings regarding the application of the Zika virus (ZIKV) in GBM treatment. ZIKV, a member of the family Flaviviridae, shows oncolytic properties against GBM, opening novel therapeutic avenues. We explore intensive investigations of glioblastoma stem cells, recognized as key drivers in GBM initiation, progression, and resistance to therapy. However, a comprehensive elucidation of ZIKV's underlying mechanisms is imperative to pave the way for ZIKV-based clinical trials targeting GBM patients. This investigation into harnessing the potential of oncolytic-virus genomes for mRNA-based immunotherapies underscores its noteworthy implications, potentially paving the way for a paradigm shift in cancer treatment strategies.

Recent advances of engineered oncolytic viruses-based combination therapy for liver cancer

Liver cancer is a major malignant tumor, which seriously threatens human health and increases the economic burden on patients. At present, gene therapy has been comprehensively studied as an excellent therapeutic measure in liver cancer treatment. Oncolytic virus (OV) is a kind of virus that can specifically infect and kill tumor cells. After being modified by genetic engineering, the specificity of OV infection to tumor cells is increased, and its influence on normal cells is reduced. To date, OV has shown its effectiveness and safety in experimental and clinical studies on a variety of tumors. Thus, this review primarily introduces the current status of different genetically engineered OVs used in gene therapy for liver cancer, focuses on the application of OVs and different target genes for current liver cancer therapy, and identifies the problems encountered in OVs-based combination therapy and the corresponding solutions, which will provide new insights into the treatment of liver cancer.

Glioma stem cells remodel immunotolerant microenvironment in GBM and are associated with therapeutic advancements

Glioma is the most common primary tumor of the central nervous system (CNS). Glioblastoma (GBM) is incurable with current treatment strategies. Additionally, the treatment of recurrent GBM (rGBM) is often referred to as terminal treatment, necessitating hospice-level care and management. The presence of the blood-brain barrier (BBB) gives GBM a more challenging or "cold" tumor microenvironment (TME) than that of other cancers and gloma stem cells (GSCs) play an important role in the TME remodeling, occurrence, development and recurrence of giloma. In this review, our primary focus will be on discussing the following topics: niche-associated GSCs and macrophages, new theories regarding GSC and TME involving pyroptosis and ferroptosis in GBM, metabolic adaptations of GSCs, the influence of the cold environment in GBM on immunotherapy, potential strategies to transform the cold GBM TME into a hot one, and the advancement of GBM immunotherapy and GBM models.

Stem Cells and Tumor-Killing Virus to Target Brain Tumor: In Pursuit to Bring a Potential Delivery Vehicle for the Central Nervous System Tumors

To target brain cancer, various therapeutic options are present to fight against cancer cells. But the existing therapies are not showing a proper curation of cancer patients. Henceforth, activating the immune cells and targeting oncogenes/proteins might be an emerging therapeutic approach to target and destroy malignant brain tumor. Stem cells (SCs) are considered potential immunomodulators that trigger the highly suppressed immune system in the tumor microenvironment. Also, engineered SCs can repress the aberrantly expressed oncoproteins that cause tumor cell proliferation and growth. SCs have an excellent migration capability to reach the infected site and support the regeneration of damaged blood vessels and tissues. Likewise, oncolytic virotherapy (OVT) is a promising novel therapeutic molecule in which genetically modified viruses can selectively replicate and destroy cancer cells without harming healthy cells. Same as SCs, oncolytic viruses (OVs) tend to stimulate the host's innate and adaptive immune response to battle against the advanced brain tumor. In clinical studies, various OVs have shown good immunogenic responses with a high safety profile and tolerability against cancer patients with reduced morbidity and mortality rate. SCs act as an attractive cargo for OVs which helps to influence the tumor site and destroy the tumor volume. SCs protect the OVs from systemic degradation and promote therapeutic efficacy against cancer cells. SCs carried OVs might be a potential therapeutic way to bring an effective treatment option for brain tumors.

Vector-Mediated Cancer Gene Therapy Reduces Toxicity and Inhibition of Lung Carcinoma Growth in Nude Mice

Replication-competent oncolytic adenovirus (TOA2) gene therapy is a recently introduced anti-tumor treatment regimen with superior results. The biodistribution studies of virus vector-based medicine seem more cautious and have been given much attention recently in terms of its quality and safety in preclinical trials. The current study determined the biodistribution and safety of a replication-competent adenovirus in different organs to predict its toxicity threshold. The present study has used TOA2, while biodistribution analysis was performed in human lung carcinoma A549-induced tumor-bearing nude mice model. Intratumoral injection was applied onto tumor-bearing mice with the adenovirus (3×1010 VP per mouse). Mice were sacrificed at the end of the experiment and the organs were dissected. Biodistribution analysis was done with complete hexon gene detection in each organ using quantitative real-time polymerase chain reaction (qRT-PCR). The biodistribution and concentration profiles showed that the TOA2 is well distributed in the entire tumor tissue. After dose 3 at day 11, the concentration of the virus has increased in the tumor tissue from 2240.54 (± 01.69) copies/100 ng genome to 13,120.28 (± 88.21) copies/100 ng genome on the 18th day, which eventually approached 336.45 (± 23.41) copies/100ng genome on the day 36. On the contrary, the concentration of the same decreased in the order of the liver, kidney, spleen, lung, and heart over time but no distributional traces in gonads. But the concentration found decreased dramatically in blood and other organs, while at the end of the experiment no detectable distribution was seen besides tumor tissue. The study confirms that adenovirus-based tumor therapy using conditionally replicating competent oncolytic TOA2 exhibited great efficiency with no toxicity at all.

Novel Therapies in Glioblastoma Treatment: Review of Glioblastoma; Current Treatment Options; and Novel Oncolytic Viral Therapies

One of the most prevalent primary malignant brain tumors is glioblastoma (GB). About 6 incidents per 100,000 people are reported annually. Most frequently, these tumors are linked to a poor prognosis and poor quality of life. There has been little advancement in the treatment of GB. In recent years, some innovative medicines have been tested for the treatment of newly diagnosed cases of GB and recurrent cases of GB. Surgery, radiotherapy, and alkylating chemotherapy are all common treatments for GB. A few of the potential alternatives include immunotherapy, tumor-treating fields (TTFs), and medications that target specific cellular receptors. To provide new multimodal therapies that focus on the molecular pathways implicated in tumor initiation and progression in GB, novel medications, delivery technologies, and immunotherapy approaches are being researched. Of these, oncolytic viruses (OVs) are among the most recent. Coupling OVs with certain modern treatment approaches may have significant benefits for GB patients. Here, we discuss several OVs and how they work in conjunction with other therapies, as well as virotherapy for GB. The study was based on the PRISMA guidelines. Systematic retrieval of information was performed on PubMed. A total of 307 articles were found in a search on oncolytic viral therapies for glioblastoma. Out of these 83 articles were meta-analyses, randomized controlled trials, reviews, and systematic reviews. A total of 42 articles were from the years 2018 to 2023. Appropriate studies were isolated, and important information from each of them was understood and entered into a database from which the information was used in this article. One of the most prevalent malignant brain tumors is still GB. Significant promise and opportunity exist for oncolytic viruses in the treatment of GB and in boosting immune response. Making the most of OVs in the treatment of GB requires careful consideration and evaluation of a number of its application factors.

Replication-incompetent influenza A viruses armed with IFN-γ effectively mediate immune modulation and tumor destruction in mice harboring lung cancer

Low pathogenic influenza A viruses (IAVs) have shown promising oncolytic potential in lung cancer-bearing mice. However, as replication-competent pathogens, they may cause side effects in immunocompromised cancer patients. To circumvent this problem, we genetically engineered nonreplicating IAVs lacking the hemagglutinin (HA) gene (ΔHA IAVs), but reconstituted the viral envelope with recombinant HA proteins to allow a single infection cycle. To optimize the therapeutic potential and improve immunomodulatory properties, these replication-incompetent IAVs were complemented with a murine interferon-gamma (mIFN-γ) gene. After intratracheal administration to transgenic mice that develop non-small cell lung cancer (NSCLC), the ΔHA IAVs induced potent tumor destruction. However, ΔHA IAVs armed with mIFN-γ exhibited an even stronger and more sustained effect, achieving 85% tumor reduction at day 12 postinfection. In addition, ΔHA-mIFN-γ viruses were proven to be efficient in recruiting and activating natural killer cells and macrophages from the periphery and in inducing cytotoxic T lymphocytes. Most important, both viruses, and particularly IFN-γ-encoding viruses, activated tumor-associated alveolar macrophages toward a proinflammatory M1-like phenotype. Therefore, replication-incompetent ΔHA-mIFN-γ-IAVs are safe and efficient oncolytic viruses that additionally exhibit immune cell activating properties and thus represent a promising innovative therapeutic option in the fight against NSCLC.

Progress in the application of hydrogels in immunotherapy of gastrointestinal tumors

Gastrointestinal tumors are the most common cancers with the highest morbidity and mortality worldwide. Surgery accompanied by chemotherapy, radiotherapy and targeted therapy remains the first option for gastrointestinal tumors. However, poor specificity for tumor cells of these postoperative treatments often leads to severe side effects and poor prognosis. Tumor immunotherapy, including checkpoint blockade and tumor vaccines, has developed rapidly in recent years, showing good curative effects and minimal side effects in the treatment of gastrointestinal tumors. National Comprehensive Cancer Network guidelines recommend tumor immunotherapy as part of the treatment of gastrointestinal tumors. However, the heterogeneity of tumor cells, complicacy of the tumor microenvironment and poor tumor immunogenicity hamper the effectiveness of tumor immunotherapy. Hydrogels, defined as three-dimensional, hydrophilic, and water-insoluble polymeric networks, could significantly improve the overall response rate of immunotherapy due to their superior drug loading efficacy, controlled release and drug codelivery ability. In this article, we briefly describe the research progress made in recent years on hydrogel delivery systems in immunotherapy for gastrointestinal tumors and discuss the potential future application prospects and challenges to provide a reference for the clinical application of hydrogels in tumor immunotherapy.

Pevonedistat, a first-in-class NEDD8-activating enzyme inhibitor, sensitizes cancer cells to VSVΔ51 oncolytic virotherapy

The clinical efficacy of VSVΔ51 oncolytic virotherapy has been limited by tumor resistance to viral infection, so strategies to transiently repress antiviral defenses are warranted. Pevonedistat is a first-in-class NEDD8-activating enzyme (NAE) inhibitor currently being tested in clinical trials for its antitumor potential. In this study, we demonstrate that pevonedistat sensitizes human and murine cancer cells to increase oncolytic VSVΔ51 infection, increase tumor cell death, and improve therapeutic outcomes in resistant syngeneic murine cancer models. Increased VSVΔ51 infectivity was also observed in clinical human tumor samples. We further identify the mechanism of this effect to operate via blockade of the type 1 interferon (IFN-1) response through neddylation-dependent interferon-stimulated growth factor 3 (ISGF3) repression and neddylation-independent inhibition of NF-κB nuclear translocation. Together, our results identify a role for neddylation in regulating the innate immune response and demonstrate that pevonedistat can improve the therapeutic outcomes of strategies using oncolytic virotherapy.

Hypoxia effects on oncolytic virotherapy in Cancer: Friend or Foe?

Researchers have tried to find novel strategies for cancer treatment in the past decades. Among the utilized methods, administering oncolytic viruses (OVs) alone or combined with other anticancer therapeutic approaches has had promising outcomes, especially in solid tumors. Infecting the tumor cells by these viruses can lead to direct lysis or induction of immune responses. However, the immunosuppressive tumor microenvironment (TME) is considered a significant challenge for oncolytic virotherapy in treating cancer. Based on OV type, hypoxic conditions in the TME can accelerate or repress virus replication. Therefore, genetic manipulation of OVs or other molecular modifications to reduce hypoxia can induce antitumor responses. Moreover, using OVs with tumor lysis capability in the hypoxic TME may be an attractive strategy to overcome the limitations of the therapy. This review summarizes the latest information available in the field of cancer virotherapy and discusses the dual effect of hypoxia on different types of OVs to optimize available related therapeutic methods.

Assessment of Clinical Response to V937 Oncolytic Virus After Intravenous or Intratumoral Administration Using Physiologically-Based Modeling

Oncolytic viruses (OVs) represent a potential therapeutic strategy in cancer treatment. However, there is currently a lack of comprehensive quantitative models characterizing clinical OV kinetics and distribution to the tumor. In this work, we present a mechanistic modeling framework for V937 OV, after intratumoral (i.t.) or intravascular (i.v.) administration in patients with cancer. A minimal physiologically-based pharmacokinetic model was built to characterize biodistribution of OVs in humans. Viral dynamics was incorporated at the i.t. cellular level and linked to tumor response, enabling the characterization of a direct OV killing triggered by the death of infected tumor cells and an indirect killing induced by the immune response. The model provided an adequate description of changes in V937 mRNA levels and tumor size obtained from phase I/II clinical trials after V937 administration. The model showed prominent role of viral clearance from systemic circulation and infectivity in addition to known tumor aggressiveness on clinical response. After i.v. administration, i.t. exposure of V937 was predicted to be several orders of magnitude lower compared with i.t. administration. These differences could be overcome if there is high virus infectivity and/or replication. Unfortunately, the latter process could not be identified at the current clinical setting. This work provides insights on selecting optimal OV considering replication rate and infectivity.

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-Driven Biotherapies from Bench to Bedside

With advances in cancer biology and an ever-deepening understanding of molecular virology, oncolytic virus (OV)-driven therapies have developed rapidly and become a promising alternative to traditional cancer therapies. In recent years, satisfactory results for oncolytic virus therapy (OVT) are achieved at both the cellular and organismal levels, and efforts are being increasingly directed toward clinical trials. Unfortunately, OVT remains ineffective in these trials, especially when performed using only a single OV reagent. In contrast, integrated approaches, such as using immunotherapy, chemotherapy, or radiotherapy, alongside OVT have demonstrated considerable efficacy. The challenges of OVT in clinical efficacy include the restricted scope of intratumoral injections and poor targeting of intravenous administration. Further optimization of OVT delivery is needed before OVs become a viable therapy for tumor treatment. In this review, the development process and antitumor mechanisms of OVs are introduced. The advances in OVT delivery routes to provide perspectives and directions for the improvement of OVT delivery are highlighted. This review also discusses the advantages and limitations of OVT monotherapy and combination therapy through the lens of recent clinical trials and aims to chart a course toward safer and more effective OVT strategies.

Current Status and Challenges of Oncolytic Virotherapy for the Treatment of Glioblastoma

Despite decades of research and numerous clinical trials, the prognosis of patients diagnosed with glioblastoma (GBM) remains dire with median observed survival at 8 months. There is a critical need for novel treatments for GBM, which is the most common malignant primary brain tumor. Major advances in cancer therapeutics such as immune checkpoint inhibitors and chimeric antigen receptor (CAR) T-cell therapy have not yet led to improved outcomes for GBM. Conventional therapy of surgery followed by chemoradiation with or without tumor treating fields remains the standard of care. One of the many approaches to GBM therapy currently being explored is viral therapies. These typically work by selectively lysing target neoplastic cells, called oncolysis, or by the targeted delivery of a therapeutic transgene via a viral vector. In this review, we discuss the underlying mechanisms of action and describe both recent and current human clinical trials using these viruses with an emphasis on promising viral therapeutics that may ultimately break the field's current stagnant paradigm.

Advancing therapeutic strategies for Epstein-Barr virus-associated malignancies through lytic reactivation

Epstein-Barr virus (EBV) is a widespread human herpes virus associated with lymphomas and epithelial cell cancers. It establishes two separate infection phases, latent and lytic, in the host. Upon infection of a new host cell, the virus activates several pathways, to induce the expression of lytic EBV antigens and the production of infectious virus particles. Although the carcinogenic role of latent EBV infection has been established, recent research suggests that lytic reactivation also plays a significant role in carcinogenesis. In this review, we summarize the mechanism of EBV reactivation and recent findings about the role of viral lytic antigens in tumor formation. In addition, we discuss the treatment of EBV-associated tumors with lytic activators and the targets that may be therapeutically effective in the future.

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.

Advances in Intralesional Therapy for Locoregionally Advanced and Metastatic Melanoma: Five Years of Progress

Locoregionally advanced and metastatic melanoma are complex diagnoses with a variety of available treatment options. Intralesional therapy for melanoma has been under investigation for decades; however, it has advanced precipitously in recent years. In 2015, the Food and Drug Administration (FDA) approved talimogene laherparepvec (T-VEC), the only FDA-approved intralesional therapy for advanced melanoma. There has been significant progress since that time with other oncolytic viruses, toll-like receptor agonists, cytokines, xanthene dyes, and immune checkpoint inhibitors all under investigation as intralesional agents. Further to this, there has been exploration of numerous combinations of intralesional therapies and systemic therapies as various lines of therapy. Several of these combinations have been abandoned due to their lack of efficacy or safety concerns. This manuscript presents the various types of intralesional therapies that have reached phase 2 or later clinical trials in the past 5 years, including their mechanism of action, therapeutic combinations under investigation, and published results. The intention is to provide an overview of the progress that has been made, discuss ongoing trials worth following, and share our opinions on opportunities for further advancement.

Recent Developments in Glioblastoma Therapy: Oncolytic Viruses and Emerging Future Strategies

Glioblastoma is the most aggressive form of malignant brain tumor. Standard treatment protocols and traditional immunotherapy are poorly effective as they do not significantly increase the long-term survival of glioblastoma patients. Oncolytic viruses (OVs) may be an effective alternative approach. Combining OVs with some modern treatment options may also provide significant benefits for glioblastoma patients. Here we review virotherapy for glioblastomas and describe several OVs and their combination with other therapies. The personalized use of OVs and their combination with other treatment options would become a significant area of research aiming to develop the most effective treatment regimens for glioblastomas.

Immune response elicited in the tumor microenvironment upon rMV-SLAMblind cancer virotherapy

Oncolytic virotherapy is a promising therapy for cancer. We previously established a recombinant measles virus (rMV-SLAMblind) that targets NECTIN4-expressing cancer cells and demonstrated its antitumor effects using a xenograft model in an immunodeficient mouse. In the current study, to investigate the immune response after rMV-SLAMblind therapy, we developed an immunocompetent cancer mouse model by introducing the NECTIN4 gene into mouse cancer cell lines. NECTIN4-expressing mouse cancer cells were successfully killed by rMV-SLAMblind in vitro. After transplantation of the NECTIN4-expressing tumor cells, rMV-SLAMblind significantly suppressed tumor growth in immunocompetent mice. Thus, this immunocompetent mouse cancer model could be a powerful tool in which to study the effect of rMV-SLAMblind therapy on the immune response. Using this model we found that rMV-SLAMblind elicited significant activation of natural killer cells, type 1 helper T cells and the tumor-specific CD8⁺ T-cell response in the tumor microenvironment. Immune cell depletion study revealed that CD8⁺ cells particularly played significant roles in the therapeutic efficacy of rMV-SLAMblind. Thus, rMV-SLAMblind exerts a therapeutic effect, not only directly by tumor cell killing, but also indirectly by efficient induction of antitumor immunity.

Magnetofection of miR-21 promoted by electromagnetic field and iron oxide nanoparticles via the p38 MAPK pathway contributes to osteogenesis and angiogenesis for intervertebral fusion

BACKGROUND

Magnetofection-mediated gene delivery shows great therapeutic potential through the regulation of the direction and degree of differentiation. Lumbar degenerative disc disease (DDD) is a serious global orthopaedic problem. However, even though intervertebral fusion is the gold standard for the treatment of DDD, its therapeutic effect is unsatisfactory. Here, we described a novel magnetofection system for delivering therapeutic miRNAs to promote osteogenesis and angiogenesis in patients with lumbar DDD.

RESULTS

Co-stimulation with electromagnetic field (EMF) and iron oxide nanoparticles (IONPs) enhanced magnetofection efficiency significantly. Moreover, in vitro, magnetofection of miR-21 into bone marrow mesenchymal stem cells (BMSCs) and human umbilical endothelial cells (HUVECs) influenced their cellular behaviour and promoted osteogenesis and angiogenesis. Then, gene-edited seed cells were planted onto polycaprolactone (PCL) and hydroxyapatite (HA) scaffolds (PCL/HA scaffolds) and evolved into the ideal tissue-engineered bone to promote intervertebral fusion. Finally, our results showed that EMF and polyethyleneimine (PEI)@IONPs were enhancing transfection efficiency by activating the p38 MAPK pathway.

CONCLUSION

Our findings illustrate that a magnetofection system for delivering miR-21 into BMSCs and HUVECs promoted osteogenesis and angiogenesis in vitro and in vivo and that magnetofection transfection efficiency improved significantly under the co-stimulation of EMF and IONPs. Moreover, it relied on the activation of p38 MAPK pathway. This magnetofection system could be a promising therapeutic approach for various orthopaedic diseases.

Prediction and validation of murine MHC class I epitopes of the recombinant virus VSV-GP

Oncolytic viruses are currently tested as a novel platform for cancer therapy. These viruses preferentially replicate in and kill malignant cells. Due to their microbial origin, treatment with oncolytic viruses naturally results in anti-viral responses and general immune activation. Consequently, the oncolytic virus treatment also induces anti-viral T cells. Since these can constitute the dominant activated T cell pool, monitoring of the anti-viral T cell response may aid in better understanding of the immune responses post oncolytic virotherapy. This study aimed to identify the anti-viral T cells raised by VSV-GP virotherapy in C57BL/6J mice, one of the most widely used models for preclinical studies. VSV-GP is a novel oncolytic agent that recently entered a clinical phase I study. To identify the VSV-GP epitopes to which mouse anti-viral T cells react, we used a multilevel adapted bioinformatics viral epitope prediction approach based on the tools netMHCpan, MHCflurry and netMHCstabPan, which are commonly used in neoepitope identification. Predicted viral epitopes were ranked based on consensus binding strength categories, predicted stability, and dissimilarity to the mouse proteome. The top ranked epitopes were selected and included in the peptide candidate matrix in order to use a matrix deconvolution approach. Using ELISpot, we showed which viral epitopes presented on C57BL/6J mouse MHC-I alleles H2-Db and H2-Kb trigger IFN-γ secretion due to T cell activation. Furthermore, we validated these findings using an intracellular cytokine staining. Collectively, identification of the VSV-GP T cell epitopes enables monitoring of the full range of anti-viral T cell responses upon VSV-GP virotherapy in future studies with preclinical mouse models to more comprehensively delineate anti-viral from anti-tumor T cell responses. These findings also support the development of novel VSV-GP variants expressing immunomodulatory transgenes and can improve the assessment of anti-viral immunity in preclinical models.

Evaluation of Human Mesenchymal Stromal Cells as Carriers for the Delivery of Oncolytic HAdV-5 to Head and Neck Squamous Cell Carcinomas

Human multipotent mesenchymal stromal cells (hMSCs) are of significant therapeutic interest due to their ability to deliver oncolytic adenoviruses to tumors. This approach is also investigated for targeting head and neck squamous cell carcinomas (HNSCCs). HAdV-5-HexPos3, a recently reported capsid-modified vector based on human adenovirus type 5 (HAdV-5), showed strongly improved infection of both hMSCs and the HNSCC cell line UM-SCC-11B. Given that, we generated life cycle-unmodified and -modified replication-competent HAdV-5-HexPos3 vector variants and analyzed their replication within bone marrow- and adipose tissue-derived hMSCs. Efficient replication was detected for both life cycle-unmodified and -modified vectors. Moreover, we analyzed the migration of vector-carrying hMSCs toward different HNSCCs. Although migration of hMSCs to HNSCC cell lines was confirmed in vitro, no homing of hMSCs to HNSCC xenografts was observed in vivo in mice and in ovo in a chorioallantoic membrane model. Taken together, our data suggest that HAdV-5-HexPos3 is a potent candidate for hMSC-based oncolytic therapy of HNSCCs. However, it also emphasizes the importance of generating optimized in vivo models for the evaluation of hMSC as carrier cells.

Dendritic cells and natural killer cells: The road to a successful oncolytic virotherapy

Every type of cancer tissue is theoretically more vulnerable to viral infection. This natural proclivity has been harnessed as a new anti-cancer therapy by employing oncolytic viruses (OVs) to selectively infect and destroy cancer cells while providing little or no harm with no toxicity to the host. Whereas the primary oncolytic capabilities of OVs initially sparked the greatest concern, the predominant focus of research is on the association between OVs and the host immune system. Numerous OVs are potent causal agents of class I MHC pathway-related chemicals, enabling early tumor/viral immune recognition and cytokine-mediated response. The modified OVs have been studied for their ability to bind to dendritic cells (DCs) by expressing growth factors, chemokines, cytokines, and defensins inside the viral genome. OVs, like reovirus, can directly infect DCs, causing them to release chemokines and cytokines that attract and excite natural killer (NK) cells. In addition, OVs can directly alter cancer cells' sensitivity to NK by altering the expression levels of NK cell activators and inhibitors on cancerous cells. Therefore, NK cells and DCs in modulating the therapeutic response should be considered when developing and improving future OV-based therapeutics, whether modified to express transgenes or used in combination with other drugs/immunotherapies. Concerning the close relationship between NK cells and DCs in the potential of OVs to kill tumor cells, we explore how DCs and NK cells in tumor microenvironment affect oncolytic virotherapy and summarize additional information about the interaction mentioned above in detail in this work.