Cancer remains the leading cause of death in domestic dogs. Conventional therapeutic approaches, including surgery, chemotherapy, and radiotherapy, frequently fail to achieve sustained remission or stabilization. Oncolytic virotherapy, a rapidly advancing therapeutic modality in human oncology, is emerging as a novel strategy in veterinary medicine. This systematic review summarizes current knowledge on the application of oncolytic viruses (OVs) in canine cancer treatment, focusing on their mechanisms of action, safety profiles, and clinical efficacy. We evaluate diverse OV platforms, including myxoma virus, reovirus, vesicular stomatitis virus, canine adenoviruses, vaccinia virus, Sendai virus, and Newcastle disease virus, across preclinical and clinical studies in dogs with various malignancies. While several OVs have demonstrated favorable tolerability and modest antitumor activity, key challenges such as pre-existing immunity, optimization of dosing regimens, and rational combination strategies remain to be addressed. This review emphasizes the translational significance of canine studies for both veterinary and human oncology, underscoring the critical need for rigorously designed clinical trials to refine virotherapy protocols and expand therapeutic options for canine cancer patients.

Oncolytic virotherapy offers a promising avenue for solid tumor treatment, yet single-agent approaches are frequently limited by insufficient tumor lysis and inadequate immune activation. Here we report that combined therapy with two recombinant variants of the oncolytic vaccinia virus, armed with either herpes simplex virus thymidine kinase (VV-HSVtk) or the interleukin 15 receptor subunit alpha (VV-mIL15Rα), leads to enhanced cytotoxicity and immune stimulation in a murine mammary adenocarcinoma model (4T1). In vitro, VV-HSVtk exhibited dose-dependent cytotoxicity markedly potentiated by ganciclovir (GCV) through HSVtk-mediated phosphorylation into a cytotoxic nucleoside analog, and co-culture of VV-infected tumor cells with donor-derived NK cells further increased oncolytic efficiency. In vivo, combined treatment with VV-HSVtk, VV-mIL15Rα, and GCV resulted in significant tumor regression and extended survival relative to monotherapy controls in 4T1 syngeneic mice. Histological examination revealed increased lymphocytic infiltration at tumor sites and absence of hepatic or splenic toxicity. Together, these data indicate that integrating direct viral cytotoxicity, HSVtk/GCV-mediated suicide gene therapy, and IL-15-pathway-targeted immunomodulation within an oncolytic vaccinia platform can improve antitumor efficacy in a stringent breast cancer model.

Background/Objectives: Glioblastoma remains the most lethal primary brain tumor in adults, and progress in oncolytic virotherapy is limited by the lack of immunocompetent models permissive to human-tropic viruses. Methods: Here, murine CT-2A and GL261 glioma and B16 melanoma cell lines were engineered to express human Coxsackievirus and Adenovirus Receptor (CXADR) fused to tagBFP, generating "humanized" tumors that preserve parental growth characteristics while acquiring high susceptibility to group B Coxsackieviruses (CVBs) and adenovirus serotype 5. Results: CXADR expression in CT-2A, GL261, and B16 cells markedly enhanced binding, internalization, and replication of CVBs in vitro, with the strongest effect observed for LEV14 (attenuated CVB5), which reached up to 105-fold higher viral titers in humanized cells compared with parental cells. Unchanged sensitivity to vesicular stomatitis virus indicated receptor-specific effects. Humanized CT-2A-CXADR-BFP and GL261-CXADR-BFP cells initiated aggressive subcutaneous and intracranial tumors in syngeneic C57BL/6 mice without signs of immune rejection, and histology and MRI confirmed invasive high-grade glioma phenotypes. In intracranial CT-2A-CXADR-BFP tumors, repeated intratumoral LEV14 administration induced extensive tumor necrosis and prolonged survival despite the rapid development of neutralizing antibodies. Systemic intravenous LEV14 dosing produced strong oncolytic activity against subcutaneous CT-2A-CXADR-BFP tumors, as demonstrated by pronounced tumor growth inhibition, long-lasting regression in a subset of animals with gliomas, and improved overall survival. Conclusions: Collectively, these data establish CXADR-humanized models as versatile, immunocompetent platforms for evaluation of CXADR-dependent oncolytic enteroviruses.

Poliovirus represents an oncolytic agent for human glioblastoma—one of the most aggressive types of cancer. Since interference of viruses with metabolic and redox pathways is often linked to their pathogenesis, drugs targeting metabolic enzymes are regarded as potential enhancers of oncolysis. Our goal was to reveal an imprint of poliovirus on the metabolism of glioblastoma cell lines and to assess the dependence of the virus on these pathways. Using GC-MS, HPLC, and Seahorse techniques, we show that poliovirus interferes with amino acid, purine and polyamine metabolism, mitochondrial respiration, and glycolysis. However, many of these changes are cell line- and culture medium-dependent. 2-Deoxyglucose, the pharmacologic inhibitor of glycolysis, was shown to enhance the cytopathic effect of poliovirus, pointing to its possible repurposing as an enhancer of oncolysis. Inhibitors of polyamine biosynthesis, pyruvate import into mitochondria, and fatty acid oxidation exhibited antiviral activity, albeit in a cell-dependent manner. We also demonstrate that poliovirus does not interfere with the production of superoxide anions or with levels of H2O2, showing an absence of oxidative stress during infection. Finally, we showed that a high rate of poliovirus replication is associated with fragmentation of the mitochondrial network, pointing to the significance of these organelles for the virus.

Non-pathogenic natural and recombinant strains of human Enteroviruses are the subject of ongoing study with some strains having been approved for use as anticancer agents. The efficacy of oncolytic virotherapy depends upon identifying the receptor utilized by a specific strain for cell entry, and the presence of this receptor on the surface of cancer cells. Accordingly, a rapid and straightforward approach to determining the enteroviral receptors is necessary for developing an effective patient-specific, virus-based cancer therapy. To this end, we created a panel of seven lines with double knockouts on the background of the HEK293T cell line, which lacks the IFNAR1 gene. In these lines, the main viral receptor genes, including PVR, CXADR, CD55, ITGA2, SCARB2, ICAM1, and FCGRT, were knocked out using the CRISPR/Cas9 system. The panel of lines was validated on twelve different Enteroviruses types, providing a basis for studying the molecular mechanisms of enterovirus entry into cells, and for developing new therapeutic strains.

Sestrins, evolutionarily conserved stress-responsive proteins, are increasingly recognized for their potential role in lifespan regulation. This study aimed to elucidate the influence of the sesn-1 gene on lifespan modulation during caloric deprivation (CD) in the model organism C. elegans. Our findings reveal that sesn-1 mediates lifespan extension under CD, primarily through the repression of mTORC1 kinase and activation of autophagy. Moreover, we identified an essential role for sesn-1 in enhancing stress resilience in nematodes, particularly in the context of nutrient sensing. Further investigations demonstrated sesn-1's interaction with the GATOR2 protein complex, its role in maintaining muscle integrity and a potential synergy between sesn-1 and the FOXO pathway. Overall, our research underscores the profound implications of Sestrins in aging and stress resistance, shedding light on possible therapeutic avenues for prevention and treatment of age-associated disorders.

Treatment of malignant diseases using oncolytic viruses (OVs) is currently considered a promising therapeutic approach. Initial encouraging results fueled a large number of clinical trials, showcasing favorable safety profiles of OVs—but therapeutic outcomes remain far from perfect. The efficacy of systemically administered OVs is limited due to rapid immune clearance and suboptimal biodistribution, while locally administered OVs encounter an additional barrier of poor bioavailability. Cell-based carriers that can shield viral particles and provide tumor-targeted OV delivery, represent one of the potential ways to address these challenges. The feasibility of this approach was demonstrated using a broad range of cell types, including mesenchymal stem cells (MSCs), neural stem cells (NSCs), different subsets of immune cells, and cancer cell lines. The resulting spectrum of carriers can be viewed as a multifaceted tool, taking into account the specific properties, advantages, and limitations of each cell carrier type discussed in this review. Careful consideration of these features will provide the basis for successful development of cell-based OV delivery platforms.

Immunotherapy with oncolytic viruses (OVs) becomes a full-fledged neoadjuvant therapy method in the paradigm of evidence-based medicine for the growing number of cancers. The use of OVs for immunologically "cold" tumors causing minimal immune response and having the clearly immunosuppressive tumor microenvironment is especially relevant. Recombinant OVs carrying the sequences of proteins activating the immune system can be used to stimulate antitumor response. The study aimed to assess oncoselectivity and antitumor activity of the recombinant OV designed based on the LIVP vaccinia virus strain showing expression of human and murine interpheron alpha sequences (hIFN alpha and mIFN alpha, respectively). The in vitro experiments showed that the recombinant OVs designed showed oncoselectivity in relation to tumor cell lines of appropriate species. The ability to effectively infect human adenocarcinoma and glioblastoma cell lines was reported for LIVP-hIFN alpha. LIVP-mIFN alpha showed selectivity in relation to glioma Gl261 and melanoma B16 in vitro. The in vivo experiment involving the C57Bl/6 mice with subcutaneous melanoma & Vcy;16 showed the ability of the intravenously administered LIVP-mIFN alpha to reduce the size of the subcutaneous tumor allograft and increase tumor infiltration with the CD8+ and NK cells. The recombinant virus designed can be a potential platform for the development of oncolytic virotherapy of human melanoma and glioblastoma.

Enteroviruses, with their diverse clinical manifestations ranging from mild or asymptomatic infections to severe diseases such as poliomyelitis and viral myocarditis, present a public health threat. However, they can also be used as oncolytic agents. This review shows the intricate relationship between enteroviruses and host cell factors. Enteroviruses utilize specific receptors and coreceptors for cell entry that are critical for infection and subsequent viral replication. These receptors, many of which are glycoproteins, facilitate virus binding, capsid destabilization, and internalization into cells, and their expression defines virus tropism towards various types of cells. Since enteroviruses can exploit different receptors, they have high oncolytic potential for personalized cancer therapy, as exemplified by the antitumor activity of certain enterovirus strains including the bioselected non-pathogenic Echovirus type 7/Rigvir, approved for melanoma treatment. Dissecting the roles of individual receptors in the entry of enteroviruses can provide valuable insights into their potential in cancer therapy. This review discusses the application of gene-targeting techniques such as CRISPR/Cas9 technology to investigate the impact of the loss of a particular receptor on the attachment of the virus and its subsequent internalization. It also summarizes the data on their expression in various types of cancer. By understanding how enteroviruses interact with specific cellular receptors, researchers can develop more effective regimens of treatment, offering hope for more targeted and efficient therapeutic strategies.

Cancer cell aggressiveness, marked by actin cytoskeleton reconfiguration critical for metastasis, may result from an imbalanced ratio favoring γ-actin. Dysfunctional p53 emerges as a key regulator of invasiveness and migration in various cancer cells, both in vitro and in vivo. P53 inactivation (via mutants R175H, R248W, R273H, or TP53 repression) significantly enhanced the migration, invasion, and proliferation of human lung adenocarcinoma A549 cells in vitro and in vivo, facilitating intrapulmonary xenograft metastasis in athymic mice. Conversely, wild-type TP53 (TP53 WT) overexpression in p53-deficient non-small- cell lung cancer (NSCLC) H1299 cells substantially reduced proliferation and migration in vitro, effectively curbing orthotopic tumorigenicity and impeding in vivo metastasis. These alterations in cell motility were closely associated with actin cytoskeleton restructuring, favoring γ-actin, and coincided with ERK1/2-mediated signaling activation, unveiling an innovative regulatory mechanism in malignancy progression. Cancer cell aggressiveness, driven by actin cytoskeleton reorganization and a shift towards γ-actin predominance, may be regulated by p53 dysfunction, thereby providing novel insight into tumor progression mechanisms.

Supplementary Figures 1-2 from Repression of Sestrin Family Genes Contributes to Oncogenic Ras-Induced Reactive Oxygen Species Up-regulation and Genetic Instability

We developed recombinant variants of oncolytic vaccinia virus LIVP strain expressing interleukin-15 (IL-15) or its receptor subunit alpha (IL-15Rα) to stimulate IL-15-dependent immune cells. We evaluated their oncolytic activity either alone or in combination with each other in vitro and in vivo using the murine CT26 colon carcinoma and 4T1 breast carcinoma models. We demonstrated that the admixture of these recombinant variants could promote the generation of the IL-15/IL-15Rα complex. In vitro studies indicated that 4T1 breast cancer cells were more susceptible to the developed recombinant viruses. In vivo studies showed significant survival benefits and tumor regression in 4T1 breast cancer syngeneic mice that received a combination of LIVP-IL15-RFP with LIVP-IL15Ra-RFP. Histological analysis showed recruited lymphocytes at the tumor region, while no harmful effects to the liver or spleen of the animals were detected. Evaluating tumor-infiltrated lymphocytes represented profound activation of cytotoxic T cells and macrophages in mice receiving combination therapy. Thus, our experiments showed superior oncolytic effectiveness of simultaneous injection of LIVP-IL15-RFP and LIVP-IL15Ra-RFP in breast cancer-bearing mice. The combined therapy by these recombinant variants represents a potent and versatile approach for developing new immunotherapies for breast cancer.

Cancer virotherapy is an alternative therapeutic approach based on the viruses that selectively infect and kill tumor cells. Vaccinia virus (VV) is a member of the Poxviridae , a family of enveloped viruses with a large linear double-stranded DNA genome. The proven safety of the VV strains as well as considerable transgene capacity of the viral genome, make VV an excellent platform for creating recombinant oncolytic viruses for cancer therapy. Furthermore, various genetic modifications can increase tumor selectivity and therapeutic efficacy of VV by arming it with the immune-modulatory genes or proapoptotic molecules, boosting the host immune system, and increasing cross-priming recognition of the tumor cells by T-cells or NK cells. In this review, we summarized the data on bioengineering approaches to develop recombinant VV strains for enhanced cancer immunotherapy.

Sredi onkoliticheskih virusov odnim iz naibolee izuchennyh yavlyaetsya virus ospovakciny (VV), shtamma modificirovannogo vysokoattenuirovannogo virusa Ankara (MVA), pokazavshego mnogoobeshchayushchie rezul'taty v doklinicheskih i klinicheskih ispytaniyah. SHtamm Lister VV iz Moskovskogo Instituta virusnyh preparatov (LIVP) issledovan v men'shej stepeni, chem MVA i imeet otlichnyj ot MVA tropizm. Cel'yu raboty bylo sravnit' onkoliticheskuyu effektivnost' shtammov LIVP i MVA v otnoshenii solidnyh opuholej. Dlya povysheniya selektivnosti LIVP i MVA k opuholevym kletkam nami byli polucheny rekombinantnye varianty s inaktivaciej gena timidinkinazy (TK), MVA-RFP i LIVP-RFP, ekspressiruyushchie krasnyj fluorescentnyj belok. Kinetiku replikacii i onkoliticheskuyu aktivnost' poluchennyh rekombinantnyh shtammov ocenivali in vitro i in vivo na liniyah opuholevyh kletok i allotransplantatah myshinyh singennyh modelej metastaticheskoj adenokarcinomy molochnoj zhelezy myshi 4T1, adenokarcinomy tolstoj kishki CT26 i melanomy B16. Kak MVA-RFP, tak i LIVP-RFP pokazali vysokuyu effektivnost' replikacii v opuholevyh kletkah i vyrazhennuyu onkoliticheskuyu aktivnost' v otnoshenii allotransplantatov melanomy V16 i adenokarcinomy molochnoj zhelezy 4T1. V otnoshenii 4T1, yavlyayushchejsya model'yu trojnogo negativnogo raka molochnoj zhelezy cheloveka, LIVP-RFP po sravneniyu s MVA-RFP pokazal bolee chem na 50% povyshennuyu citotoksichnost' v testah in vitro, a takzhe dostovernoe zamedlenie progressirovaniya allotransplantatov 4T1 i povyshenie vyzhivaemosti zhivotnyh v eksperimentah in vivo. Primenenie shtamma LIVP v kachestve platformy pri razrabotke rekombinantnyh onkoliticheskih virusov dlya terapii raka molochnoj zhelezy mozhet byt' bolee perspektivnym, chem primenenie shtamma MVA.

Oncolytic viral therapy is a promising novel approach to cancer treatment. Oncolytic viruses cause tumor regression through direct cytolysis on the one hand and recruiting and activating immune cells on the other. In this study, to enhance the antitumor efficacy of the thymidine kinase-deficient vaccinia virus (VV, Lister strain), recombinant variants encoding bacterial flagellin (subunit B) of Vibrio vulnificus (LIVP-FlaB-RFP), firefly luciferase (LIVP-Fluc-RFP) or red fluorescent protein (LIVP-RFP) were developed. The LIVP-FLuc-RFP strain demonstrated exceptional onco-specificity in tumor-bearing mice, detected by the in vivo imaging system (IVIS). The antitumor efficacy of these variants was explored in syngeneic murine tumor models (B16 melanoma, CT26 colon cancer and 4T1 breast cancer). After intravenous treatment with LIVP-FlaB-RFP or LIVP-RFP, all mice tumor models exhibited tumor regression, with a prolonged survival rate in comparison with the control mice. However, superior oncolytic activity was observed in the B16 melanoma models treated with LIVP-FlaB-RFP. Tumor-infiltrated lymphocytes and the cytokine analysis of the serum and tumor samples from the melanoma-xenografted mice treated with these virus variants demonstrated activation of the host's immune response. Thus, the expression of bacterial flagellin by VV can enhance its oncolytic efficacy against immunosuppressive solid tumors.

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.

Among oncolytic viruses, modified vaccinia virus Ankara (MVA), a highly attenuated vaccinia virus (VV) is a well-studied variant with promising results in preclinical and clinical trials. The Lister VV strain from the Moscow Institute of Viral Preparations (LIVP) has been studied to a lesser extent than MVA and has a different oncolytic property from MVA. The aim of this work was to compare the oncolytic efficacy of LIVP and MVA strains against solid tumors. We developed recombinant variants LIVP-RFP and MVA-RFP; to enhance onco-selectivity thymidine kinase (TK) gene was inactivated by insertion of red fluorescent protein (RFP) gene to the TK locus. The replication kinetics and oncolytic activity of the obtained recombinant strains were evaluated in vitro and in vivo on tumor cell lines and mouse syngeneic tumor models of metastatic mouse 4T1 mammary adenocarcinoma, CT26 colon adenocarcinoma, and B16 melanoma. Both MVA-RFP and LIVP-RFP showed high replication efficiency in tumor cells and pronounced oncolytic activity against B16 melanoma and 4T1 breast adenocarcinoma allografts. In relation to 4T1, which is a model of triple negative human breast cancer, LIVP-RFP showed more than 50% increased cytotoxicity in in vitro tests compared to MVA-RFP, as well as a significant slowdown in the progression of 4T1 allografts and an increase in animal survival in experiments in vivo. Thus, the LIVP strain may be more promising than MVA as a platform for the development of recombinant oncolytic viruses for the breast cancer treatment.

Diffuse gliomas are incurable, prevalent, and aggressive central nervous system tumors. Therefore, the development of selective oncolytic viral strains for malignant neoplasms is highly relevant. This study aimed to create an oncolytic virus based on a vaccine strain of poliovirus type 3 with natural antitumor activity. To achieve this goal, we replaced the internal ribosome entry site (IRES) of poliovirus with the corresponding fragment of human rhinovirus 30. The resulting recombinant oncolytic strain RVP3 retained the serotype of poliovirus type 3, as confirmed by virus neutralization micro-test with specific antiserum. In addition, the oncolytic efficacy of RVP3 was assessed in vitro on a broad panel of cell cultures. According to the results, RVP3 has changed its tropism, losing the ability to replicate in conditionally normal cell lines of embryonic astrocytes and embryonic fibroblasts while retaining the ability to replicate in tumor cells.

Glioblastoma multiforme (GBM) is one of the most common types of brain tumor. Despite intensive research, patients with GBM have a poor prognosis due to a very high rate of relapse and significant side effects of the treatment, with a median survival of 14.6 months. Oncolytic viruses are considered a promising strategy to eliminate GBM and other types of cancer, and several viruses have already been introduced into clinical practice. However, identification of the factors that underly the sensitivity of tumor species to oncolytic viruses or that modulate their clinical efficacy remains an important target. Here, we show that Coxsackievirus B5 (CVB5) demonstrates high oncolytic potential towards GBM primary cell species and cell lines. Moreover, 2-deoxyglucose (2DG), an inhibitor of glycolysis, potentiates the cytopathic effects of CVB5 in most of the cancer cell lines tested. The cells in which the inhibition of glycolysis enhanced oncolysis are characterized by high mitochondrial respiratory activity and glycolytic capacity, as determined by Seahorse analysis. Thus, 2-deoxyglucose and other analogs should be considered as adjuvants for oncolytic therapy of glioblastoma multiforme.

Cancer cell lines responded differentially to type I interferon treatment in models of oncolytic therapy using vesicular stomatitis virus (VSV). Two opposite cases were considered in this study, glioblastoma DBTRG-05MG and osteosarcoma HOS cell lines exhibiting resistance and sensitivity to VSV after the treatment, respectively. Type I interferon responses were compared for these cell lines by integrative analysis of the transcriptome, proteome, and RNA editome to identify molecular factors determining differential effects observed. Adenosine-to-inosine RNA editing was equally induced in both cell lines. However, transcriptome analysis showed that the number of differentially expressed genes was much higher in DBTRG-05MG with a specific enrichment in inflammatory proteins. Further, it was found that two genes, EGFR and HER2, were overexpressed in HOS cells compared with DBTRG-05MG, supporting recent reports that EGF receptor signaling attenuates interferon responses via HER2 co-receptor activity. Accordingly, combined treatment of cells with EGF receptor inhibitors such as gefitinib and type I interferon increases the resistance of sensitive cell lines to VSV. Moreover, sensitive cell lines had increased levels of HER2 protein compared with non-sensitive DBTRG-05MG. Presumably, the level of this protein expression in tumor cells might be a predictive biomarker of their resistance to oncolytic viral therapy.