Current landscape and perspective of oncolytic viruses and their combination therapies

Oncolytic virotherapy has become an important strategy in cancer immunotherapy. Oncolytic virus (OV) can reshape the tumor microenvironment (TME) through its replication-mediated oncolysis and transgene-produced anticancer effect, inducing an antitumor immune response and creating favorable conditions for the combination of other therapeutic measures. Extensive preclinical and clinical data have suggested that OV-based combination therapy has definite efficacy and promising prospects. Recently, several clinical trials of oncolytic virotherapy combined with immunotherapy have made breakthroughs. This review comprehensively elaborates the OV types and their targeting mechanisms, the selection of anticancer genes armed in OVs, and the therapeutic modes of action and strategies of OVs to provide a theoretical basis for the better design and construction of OVs and the optimization of OV-based therapeutic strategies.     

Therapeutic potency of oncolytic virotherapy in breast cancer targeting,current status and perspective

Breast cancer is the most common cause of cancer death in women and presents a serious therapeutic challenge worldwide. Traditional treatments are less successful at targeting cancer tumors, leading to recurrent treatment-resistant secondary malignancies. Oncolytic virotherapy (OV) is a novel anticancer strategy with therapeutic implications at targeting cancer cells by using mechanisms that differ from conventional therapies. Administration of OVs either alone or in combination with standard therapies provide new insights regarding the effectiveness and improvement of treatment responses for breast cancer patients. This review summarizes cellular, animal and clinical studies investigating therapeutic potency of oncolytic virotherapy in breast cancer treatment for a better understanding and hence a better management of this disease.     

Lung cancer and oncolytic virotherapy——enemy's enemy

Lung cancer is one of the malignant tumors that seriously threaten human health worldwide, while the covid-19 virus has become people's nightmare after the coronavirus pandemic. There are too many similarities between cancer cells and viruses, one of the most significant is that both of them are our enemies. The strategy to take the advantage of the virus to beat cancer cells is called Oncolytic virotherapy. When immunotherapy represented by immune checkpoint inhibitors has made remarkable breakthroughs in the clinical practice of lung cancer, the induction of antitumor immunity from immune cells gradually becomes a rapidly developing and promising strategy of cancer therapy. Oncolytic virotherapy is based on the same mechanisms that selectively kill tumor cells and induce systemic anti-tumor immunity, but still has a long way to go before it becomes a standard treatment for lung cancer. This article provides a comprehensive review of the latest progress in oncolytic virotherapy for lung cancer, including the specific mechanism of oncolytic virus therapy and the main types of oncolytic viruses, and the combination of oncolytic virotherapy and existing standard treatments. It aims to provide new insights and ideas on oncolytic virotherapy for lung cancer.     

Synergistic breast cancer suppression efficacy of doxorubicin by combination with glycyrrhetinic acid as an angiogenesis inhibitor

BackgroundTherapeutic regimens of breast cancer treatment are increasingly inclined to adopt combination strategy based on the broad spectrum antitumor effect of doxorubicin (Dox). Currently, combination therapy comprises of conventional anti-cancer drugs and angiogenesis inhibitors have been corroborated as an effective approach in cancer treatment.PurposeWe explored the ability of a natural anti-angiogenic compound glycyrrhetinic acid (GA), derived from an edible-medicinal herb licorice, to enhance the breast cancer suppression effect of Dox.Study designThe drug ratio of GA and Dox with synergistic anticancer effect against MCF-7 cells was optimized by combination index (CI) value in vitro, followed by evaluation of the improved anticancer effects and reduced side-effects of this combination in vitro and in vivo.MethodsCell viability was measured by MTT assay. Analyses of mitochondrial membrane potential and cell apoptosis on MCF-7 cells were performed by JC-1 dye and Annexin V-FITC/PI assays. The cellular accumulation of Dox when combined with GA was evaluated. Levels of apoptosis-related proteins in MCF-7 cells were measured by Western blot analysis. Synergistic anti-angiogenic effects on HUVECs were evaluated. A breast cancer mouse model was established to investigate the anti-tumor effects in vivo.ResultsBased on the optimization by CI value, Dox and GA at 1:20 molar ratio was chosen as the optimal combination drug ratio that exhibited synergistic effect against MCF-7 breast cancer cells. In addition, the combination of GA and Dox exhibited significantly enhanced cytotoxicity, apoptosis, and loss of mitochondrial membrane potential via the upregulation of a mitochondrial-dependent apoptosis pathway against MCF-7 cells. Interestingly, the addition of GA increased the intracellular accumulation of Dox in MCF-7 cells. Moreover, VEGF-induced HUVECs proliferation, migration, and tube formation were strongly inhibited by Dox when used with GA via the significant down-regulation of VEGFR2-mediated pathway, indicating that the combination of Dox and GA could exhibit ideal synergistic anti-angiogenesis effect. Expectedly, the enhanced anti-tumor efficacy of Dox and reduced Dox-induced cardiotoxicity when used in combination with GA were evident in a mouse breast tumor model.ConclusionsThese findings support that the combination of Dox with GA is a novel and promising therapeutic strategy for the treatment of breast cancer.     

The two-faces of NK cells in oncolytic virotherapy

Oncolytic viruses (OVs) are immunotherapeutics capable of directly killing cancer cells and with potent immunostimulatory properties. OVs exert their antitumor effect, at least partially, by activating the antitumor immune response, of which NK cells are an important component. However, if on the one hand increasing evidence revealed that NK cells are important mediators of oncolytic virotherapy, on the other hand, NK cells have evolved to fight viral infections, and therefore they can have a detrimental effect for the efficacy of OVs. In this review, we will discuss the dichotomy between the antitumor and antiviral functions of NK cells related to oncolytic virotherapy. We will also review NK cell-based and OV-based therapies, engineered OVs aimed at enhancing immune stimulation, and combination therapies involving OVs and NK cells currently used in cancer immunotherapy.     

The role of cancer metabolism in defining the success of oncolytic viro-immunotherapy

Oncolytic viruses infect, replicate in, and kill cancer cells selectively without harming normal cells. The rapidly expanding clinical development of oncolytic virotherapy is an exciting interdisciplinary field that provides insights into virology, oncology, and immunotherapy. Recent years have seen greater focus on rational design of cancer-selective viruses together with strategies to exploit their immunostimulatory capabilities, ultimately to develop powerful oncolytic cancer vaccines. However, despite great interest in the field, many important experiments are still conducted under optimum conditions in vitro, with many nutrients present in excess and with cellular stress kept to a minimum. Whilst this provides a convenient platform for cell culture, it bears little relation to the typical conditions found within a tumour in vivo, where cells are often subject to a range of metabolic and environmental stresses. Viral infection and cancer will both lead to production of metabolites that are also not present in media in vitro. Understanding how oncolytic viruses interact with cells exposed to more representative metabolic conditions in vitro represents an under-explored area of study that could provide valuable insight into the intelligent design of superior oncolytic viruses and help bridge the gap between bench and bedside. This review summarises the major metabolic pathways altered in cancer cells, during viral infection and highlights possible targets for future studies.     

Oncolytic virotherapy for pancreatic ductal adenocarcinoma: A glimmer of hope after years of disappointment?

Pancreatic ductal adenocarcinoma (PDAC) is one of the most aggressive and highly lethal malignancies. Existing therapeutic interventions have so far been unsuccessful in improving prognosis, and survival remains very poor. Oncolytic virotherapy represents a promising, yet not fully explored, alternative strategy for the treatment of PDAC. Oncolytic viruses (OVs) infect, replicate within and lyse tumor cells specifically and stimulate antitumor immune responses. Multiple challenges have hampered the efficacy of oncolytic virotherapy for PDAC, the most significant being the desmoplastic and immunosuppressive pancreatic tumor microenvironment (TME). The TME limits the access of therapeutic drugs and the infiltration of effector T cells and natural killer (NK) cells into the tumor mass. Additionally, cancer cells promote the secretion of immunosuppressive factors and develop mechanisms to evade the host immune system. Because of their oncolytic and immune-stimulating properties, OVs are the ideal candidates for counteracting the pancreatic immunosuppressive TME and for designing combination therapies that can be clinically exploited in clinical trials that seek to improve the prognosis of PDAC.     

Different anticancer effects of Saxifragifolin A on estrogen receptor-positive and estrogen receptor-negative breast cancer cells

BackgroundBreast cancer is the leading cause of cancer-related death among women worldwide. For treating breast cancer, numerous natural products have been considered as chemotherapeutic drugs.Hypothesis/purposeThe present study aims to investigate the apoptotic effect of Saxifragifolin A (Saxi A) isolated from Androsace umbellata in two different human breast cancer cells which are ER-positive MCF-7 cells and ER-negative MDA-MB-231 cells, and examine the molecular basis for its anticancer actions.Study designThe inhibitory effects of Saxi A on cell survival were examined in MCF-7 cells and MDA-MB-231 cells in vitro.MethodsMTT assays, Annexin V/PI staining analysis, ROS production assay, Hoechst33342 staining and Western blot analysis were performed.ResultsOur results showed that MDA-MB-231 cells were more sensitive to Saxi A-induced apoptosis than MCF-7 cells. Saxi A induced apoptosis in MDA-MB-231 cells through ROS-mediated and caspase-dependent pathways, whereas treatment with Saxi A induced apoptosis in MCF-7 cells in a caspase-independent manner. In spite of Saxi A-induced activation of MAPKs in both breast cancer cell lines, only p38 MAPK and JNK mediated Saxi A-induced apoptosis. In addition, cell survival of shERα-transfected MCF-7 cells was decreased, while MDA-MB-231 cells that overexpress ERα remained viable.ConclusionSaxi A inhibits cell survival in MCF-7 cells and MDA-MB-231 cells through different regulatory pathway, and ERα status appears to be important for regulating Saxi A-induced apoptosis in breast cancer cells. Thus, Saxi A may have a potential therapeutic use for treating breast cancer.     

MeV-Stealth: A CD46-specific oncolytic measles virus resistant to neutralization by measles-immune human serum

The frequent overexpression of CD46 in malignant tumors has provided a basis to use vaccine-lineage measles virus (MeV) as an oncolytic virotherapy platform. However, widespread measles seropositivity limits the systemic deployment of oncolytic MeV for the treatment of metastatic neoplasia. Here, we report the development of MeV-Stealth, a modified vaccine MeV strain that exhibits oncolytic properties and escapes antimeasles antibodies in vivo. We engineered this virus using homologous envelope glycoproteins from the closely-related but serologically non-cross reactive canine distemper virus (CDV). By fusing a high-affinity CD46 specific single-chain antibody fragment (scFv) to the CDV-Hemagglutinin (H), ablating its tropism for human nectin-4 and modifying the CDV-Fusion (F) signal peptide we achieved efficient retargeting to CD46. A receptor binding affinity of ~20 nM was required to trigger CD46-dependent intercellular fusion at levels comparable to the original MeV H/F complex and to achieve similar antitumor efficacy in myeloma and ovarian tumor-bearing mice models. In mice passively immunized with measles-immune serum, treatment of ovarian tumors with MeV-Stealth significantly increased overall survival compared with treatment with vaccine-lineage MeV. Our results show that MeV-Stealth effectively targets and lyses CD46-expressing cancer cells in mouse models of ovarian cancer and myeloma, and evades inhibition by human measles-immune serum. MeV-Stealth could therefore represent a strong alternative to current oncolytic MeV strains for treatment of measles-immune cancer patients.     

Blood Outgrowth Endothelial Cells as a Cellular Carrier for Oncolytic Vesicular Stomatitis Virus Expressing Interferon-β in Preclinical Models of Non-Small Cell Lung Cancer

Oncolytic viruses have demonstrated efficacy in numerous tumor models including non-small cell lung cancer (NSCLC). One limitation of viral therapy for metastatic lung cancer is that systemic administration can be hindered by complement and antiviral immunity. Thus, we investigated whether ex vivo-infected blood outgrowth endothelial cells (BOECs) could be used to deliver VSV-IFNβ in preclinical models of NSCLC. BOECs were obtained from human donors or C57/Bl6 mice. VSV was engineered to produce GFP or IFNβ. Human and murine BOECs could be infected by VSV-GFP and VSV-IFNβ. Infected BOECs resulted in killing of NSCLC cells in vitro and shielded VSV-IFNβ from antibody neutralization. Mouse BOECs localized to lungs of mice bearing syngeneic LM2 lung tumors, and infected murine BOECs reduced tumor burden in this model. In an immune-deficient A549 xenograft model, mice treated with VSV-IFNβ-infected human BOECs exhibited superior antitumor activity and survival of mice (n = 10, P < .05 compared to VSV-IFNβ alone). We conclude that BOECs can be used as a carrier for delivery of oncolytic VSV-IFNβ. This may be an effective strategy for clinical translation of oncolytic virotherapy for patients with metastatic NSCLC.     

Attenuated measles vaccine strain have potent oncolytic activity against Iraqi patient derived breast cancer cell line

BackgroundOne of the world's leading causes of death among females is breast cancer. Oncolytic viruses are promising anticancer therapy that can overcome resistance to current conventional therapies. Measles virus replicates in and destroys malignant cells without affecting healthy cells. The study aimed to evaluate the lives attenuated Measles virus vaccine against Iraqi patient derived breast cancer cells that have functional BRCA1/BRCA2 genes and compare its activity against international breast cancer MCF-7 and CAL-51 cell lines.MethodsThe virus was propagated in VERO-hSLAM slam cells. The MTT cytotoxicity assay used to test the virus's ability to kill three human breast cell lines (AMJ13), (MCF-7), and (CAL-51). The cytopathic effect of the measles virus was determined using an H&E stain. Immunocytochemistry assay using specific anti H protein monoclonal antibody for measles virus in the virally infected cells. Finally, apoptosis induction in the infected cells tested using double staining of acridine orange/propidium iodide.ResultsThe result shown that breast cancer cells are effectively infected and destroyed by live attenuated measles virus vaccine, and it caused a significant cytopathic effect in the infected cell lines after 48–72 h of infection with remarkable effect on AMJ13 cells (IC50 was 3.527 for AMJ13, when it was 5.079 and 9.171 for MCF-7 and CAL-51 respectively). Measles virus treatment induces apoptosis significantly in breast cancer cell lines compared with control cells.ConclusionMeV vaccine is useful and safe as anticancer therapy with a notable impact on the local Iraqi breast cancer AMJ13 cells.     

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

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

STAT1 Interaction with E3-14.7K in Monocytes Affects the Efficacy of Oncolytic Adenovirus

Oncolytic viruses based on adenovirus type 5 (Ad5) have been developed as a new class of therapeutic agents for cancers that are resistant to conventional therapies. Clinical experience shows that these agents are safe, but virotherapy alone has not achieved long-term cure in cancer patients. The vast majority of oncolytic adenoviruses used in clinical trials to date have deletion of the E3B genes. It has been demonstrated that the antitumor potency of the E3B-deleted mutant (dl309) is inferior to adenovirus with E3B genes intact. Tumors treated with dl309 show markedly greater macrophage infiltration than E3B-intact adenovirus. However, the functional mechanisms for this were not previously known. Here, we demonstrate that deletion of E3B genes increases production of chemokines by monocytes after adenovirus infection and increases monocyte migration. The E3B 14,700-Da protein (E3B-14.7K) inhibits STAT1 function by preventing its phosphorylation and nuclear translocation. The STAT1 inhibitor, fludarabine, rescues the effect of E3B-14.7K deletion by downregulating target chemokine expression in human and murine monocytes and results in an enhanced antitumor efficacy with dl309 in vivo. These findings have important implications for clinical use of E3B-deleted oncolytic adenovirus and other E3B-deleted adenovirus vector-based therapy.     

Induction of strong antitumor immunity by an HSV-2-based oncolytic virus in a murine mammary tumor model

Oncolytic viruses have shown considerable promise for the treatment of solid tumors. In previous studies, we demonstrated that a novel oncolytic virus (FusOn‐H2), constructed by replacing the serine/threonine protein kinase (PK) domain of the ICP10 gene of type 2 herpes simplex virus (HSV‐2) with the gene encoding the green fluorescent protein, can selectively replicate in and thus lyse tumor cells. 4T1 tumor cells are weakly immunogenic and the mammary tumors derived from them aggressively metastasize to different parts of body, thus providing an attractive model for evaluating anticancer agents. We thus tested the antitumor effect of FusOn‐H2 in this tumor model, in comparisons with several other oncolytic HSVs derived from HSV‐1, including a nonfusogenic HSV‐1 (Baco‐1) and a doubly fusogenic virus (Synco‐2D). Our results show that FusOn‐H2 and Synco‐2D have greater oncolytic activity in vitro than Baco‐1. Moreover, FusOn‐H2 induced strong T cell responses against primary and metastatic mammary tumors in vivo, and splenocytes adoptively transferred from FusOn‐H2‐treated mice effectively prevented metastasis in naïve mice bearing implanted mammary tumors. We conclude that the HSV‐2‐based FusOn‐H2 oncolytic virus may be an effective agent for the treatment of both primary and metastatic breast cancer. Copyright © 2007 John Wiley & Sons, Ltd.     

Advance in herpes simplex viruses for cancer therapy

Oncolytic virotherapy is an attractive approach that uses live viruses to selectively kill cancer cells. Oncolytic viruses can be genetically engineered to induce cell lyses through virus replication and cytotoxic protein expression. Herpes simplex virus (HSV) has become one of the most widely clinically used oncolytic agent. Various types of HSV have been studied in basic or clinical research. Combining oncolytic virotherapy with chemotherapy or radiotherapy generally produces synergic action with unclear molecular mechanisms. Arming HSV with therapeutic transgenes is a promising strategy and can be used to complement conventional therapies. As an efficient gene delivery system, HSV has been successfully used to deliver various immunomodulatory molecules. Arming HSV with therapeutic genes merits further investigation for potential clinical application.     

Vesicular stomatitis virus sensitizes immunologically cold tumors to checkpoint blockade by inducing pyroptosis

BackgroundTraditionally, vesicular stomatitis virus (VSV) and other oncolytic viruses (OVs) are thought to kill tumors by inducing apoptosis. However, cell apoptosis leads to immune quiescence, which is incompatible with the ability of OVs to activate the antitumor immune microenvironment. Thus, studying OVs-mediated oncolytic mechanisms is of great importance for the clinical application of OVs.MethodsWe examined the pyroptosis in tumor cells and tissues by morphological observation, Lactate Dehydrogenase (LDH) assay, frozen section observation, and western-blotting techniques. The critical role of GSDME in VSV-induced pyroptosis was confirmed by CRISPR/Cas9 technique. VSV virotherapy-recruited cytotoxic lymphocytes in the tumors were examined by flow cytometry assay. VSV-activated antitumor immunity was further enhanced by the co-administration with anti-PD-1 antibody.ResultsHere, we observed that VSV was able to trigger tumor pyroptosis through Gasdermin E (GSDME) in tumor cells, human tumor samples, and tumor-bearing mouse models. Importantly, the effectiveness of VSV-based virotherapy is highly dependent on GSDME, as depletion of GSDME not only reverses VSV-induced tumor-suppressive effects but also diminishes the ability of VSV to activate antitumor immunity. Notably, VSV treatment makes immunologically ‘cold’ tumors more sensitive to checkpoint blockade.ConclusionsOncolytic VSV induces tumor cell pyroptosis by activating GSDME. GSDME is critical in recruiting cytotoxic T lymphocytes in the context of VSV therapy, which can switch immunologically ‘cold’ tumors into ‘hot’ and enhance immune checkpoint therapy efficacy.     

Oncolytic Vesicular Stomatitis Virus in an Immunocompetent Model of MUC1-Positive or MUC1-Null Pancreatic Ductal Adenocarcinoma

Vesicular stomatitis virus (VSV) is a promising oncolytic agent against various malignancies. Here, for the first time, we tested VSV in vitro and in vivo in a clinically relevant, immunocompetent mouse model of pancreatic ductal adenocarcinoma (PDA). Our system allows the study of virotherapy against PDA in the context of overexpression (80% of PDA patients) or no expression of human mucin 1 (MUC1), a major marker for poor prognosis in patients. In vitro, we tested three VSV recombinants, wild-type VSV, VSV-green fluorescent protein (VSV-GFP), and a safe oncolytic VSV-ΔM51-GFP, against five mouse PDA cell lines that either expressed human MUC1 or were MUC1 null. All viruses demonstrated significant oncolytic abilities independent of MUC1 expression, although VSV-ΔM51-GFP was somewhat less effective in two PDA cell lines. In vivo administration of VSV-ΔM51-GFP resulted in significant reduction of tumor growth for tested mouse PDA xenografts (+MUC1 or MUC1 null), and antitumor efficacy was further improved when the virus was combined with the chemotherapeutic drug gemcitabine. The antitumor effect was transient in all tested groups. The developed system can be used to study therapies involving various oncolytic viruses and chemotherapeutics, with the goal of inducing tumor-specific immunity while preventing premature virus clearance.     

溶瘤单纯疱疹病毒治疗技术及其进展

溶瘤病毒治疗是当前肿瘤治疗技术的研究热点,溶瘤单纯疱疹病毒是目前研究最多的,也是抗肿瘤作用最好的溶瘤病毒之一,本文就主要介绍溶瘤单纯疱疹病毒的优势、遗传操作、发展策略、研究进展及靶向性策略等。     

Identification of a Novel Calotropis procera Protein That Can Suppress Tumor Growth in Breast Cancer through the Suppression of NF-κB Pathway

Breast cancer is the most common cancer among women. To date, improvements in hormonal and cytotoxic therapies have not yet led to a sustained remission or cure. In the present study, we investigated the in vitro and in vivo antitumor activities of a novel Calotropis procera protein (CP-P) isolated from root bark. CP-P protein inhibited the proliferation and induced apoptosis of breast cancer cells through the suppression of nuclear factor kappaB (NF-kB) activation. CP-P, when administered individually or in combination with cyclophosphamide (CYC, 0.2 mg/kg) to rats with 7, 12-dimethyl benz(a)anthracene (DMBA)-induced breast cancer decreased tumor volume significantly without affecting the body weight. To elucidate the anticancer mechanism of CP-P, antioxidant activities such as superoxide dismutase (SOD), catalase (CAT), glutathione-s-transferase (GST) and non-enzymatic antioxidant - reduced glutathione (GSH), vitamin E and C generation in the breast were analyzed by various assays. SOD, CAT, GST, GSH, vitamin E and C levels were high in combination-treated groups (CP-P+CYC) versus the CYC alone-treated groups. Also, the combination was more effective in down-regulating the expression of NF-kB-regulated gene products (cyclin D1 and Bcl-2) in breast tumor tissues. Our findings indicate that CP-P possesses significant antitumor activity comparable to a commonly used anticancer drug, cyclophosphamide, and may form the basis of a novel therapy for breast cancer.     

溶瘤病毒的免疫学机制及临床研究进展

溶瘤病毒（oncolytic virus,OVs）历经百年发展,应用于当前最具潜力的肿瘤免疫疗法。它主要是天然的或基因修饰的DNA病毒和RNA病毒。近年来随着基因工程技术的飞跃发展,经基因改造的溶瘤病毒在肿瘤治疗领域取得很大进展,很多不同类型的病毒（包括单纯疱疹病毒、腺病毒、痘病毒、麻疹病毒和呼肠孤病毒等）正处于临床前研究、临床试验阶段或已批准上市,显示了良好的安全性和临床疗效。普遍认为溶瘤病毒靶向杀伤肿瘤细胞是通过选择性在肿瘤细胞内自我复制,最终裂解肿瘤细胞,同时可激发机体的免疫应答反应,进而增强抗肿瘤免疫效果,靶向杀伤肿瘤细胞而对正常细胞无明显影响。运用基因重组技术将溶瘤病毒与免疫检查点相结合以及肿瘤免疫联合疗法的兴起和不断进步,使溶瘤病毒的应用更加广泛,但仍存在病毒靶向性、安全性、给药途径等瓶颈问题。本文综述了溶瘤病毒的发展史、病毒分类、不同类型溶瘤病毒产品的临床研究进展、溶瘤病毒靶向杀伤肿瘤的免疫学机制及未来发展面临的挑战与展望等。