Oncolytic virotherapy: the questions and the promise

Cancer immunotherapy and its facilitation by nanomedicine

Cancer immunotherapy has sparked a wave of cancer research, driven by recent successful proof-of-concept clinical trials. However, barriers are emerging during its rapid development, including broad adverse effects, a lack of reliable biomarkers, tumor relapses, and drug resistance. Integration of nanomedicine may ameliorate current cancer immunotherapy. Ultra-large surface-to-volume ratio, extremely small size, and easy modification surface of nanoparticles enable them to selectively detect cells and kill cancer cells in vivo. Exciting synergistic applications of the two approaches have emerged in treating various cancers at the intersection of cancer immunotherapy and cancer nanomedicine, indicating the potential that the combination of these two therapeutic modalities can lead to new paradigms in the treatment of cancer. This review discusses the status of current immunotherapy and explores the possible opportunities that the nanomedicine platform can make cancer immunotherapy more powerful and precise by synergizing the two approaches.

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.

A promising future in cancer immunotherapy: Oncolytic viruses

Alongside the conventional methods, attention has been drawn to the use of immunotherapy-based methods for cancer treatment. Immunotherapy has developed as a therapeutic option that can be more specific with better outcomes in tumor treatment. It can boost or regulate the immune system behind the targeted virotherapy. Virotherapy is a kind of oncolytic immunotherapy that investigated broadly in cancer treatment in recent decades, due to its several advantages. According to recent advance in the field of understanding cancer cell biology and its occurrence, as well as increasing the knowledge about conditionally replicating oncolytic viruses and their destructive function in the tumor cells, nowadays, it is possible to apply this strategy in the treatment of malignancies. Relying on achievements in clinical trials of oncolytic viruses, we can certainly expect that this therapeutic perception can play a more central role in cancer treatment. In cancer treatment, combination therapy using oncolytic viruses alongside standard cancer treatment methods and other immunotherapy-based treatments can expect more promising results in the future.

The chicken chorioallantoic membrane model for isolation of CRISPR/cas9-based HSV-1 mutant expressing tumor suppressor p53

Oncolytic viruses (OVs) have emerged as a novel cancer treatment modality, which selectively target and kill cancer cells while sparing normal ones. Among them, engineered Herpes simplex virus type 1 (HSV-1) has been proposed as a potential treatment for cancer and was moved to phase III clinical trials. Previous studies showed that design of OV therapy combined with p53 gene therapy increases the anti-cancer activities of OVs. Here, the UL39 gene of the ICP34.5 deleted HSV-1 was manipulated with the insertion of the EGFP-p53 expression cassette utilizing CRISPR/ Cas9 editing approach to enhance oncoselectivity and oncotoxicity capabilities. The ΔUL39/Δγ34.5/HSV1-p53 mutant was isolated using the chorioallantoic membrane (CAM) of fertilized chicken eggs as a complementing membrane to support the growth of the viruses with gene deficiencies. Comparing phenotypic features of ΔUL39/Δγ34.5/HSV1-p53-infected cells with the parent Δγ34.5/HSV-1 in vitro revealed that HSV-1-P53 had cytolytic ability in various cell lines from different origin with different p53 expression rates. Altogether, data presented here illustrate the feasibility of exploiting CAM model as a promising strategy for isolating recombinant viruses such as CRISPR/Cas9 mediated HSV-1-P53 mutant with less virus replication in cell lines due to increased cell mortality induced by exogenous p53.

Instigation of the epoch of nanovaccines in cancer immunotherapy

Cancer is an unprecedented proliferation of cells leading to abnormalities in differentiation and maturation. Treatment of primary and metastatic cancer is challenging. In addition to surgery, chemotherapy and radiation therapies have been conventionally used; however, they suffer from severe toxicity and non-specificity. Immunotherapy, the science of programming the body's own defense system against cancer has gained tremendous attention in the last few decades. However, partial immunogenic stimulation, premature degradation and inability to activate dendritic and helper T cells has resulted in limited clinical success. The era of nanomedicine has brought about several breakthroughs in various pharmaceutical and biomedical fields. Hereby, we review and discuss the interplay of tumor microenvironment (TME) and the immunological cascade and how they can be employed to develop nanoparticle-based cancer vaccines and immunotherapies. Nanoparticles composed of lipids, polymers and inorganic materials contain useful properties suitable for vaccine development. Proteinaceous vaccines derived from mammalian viruses, bacteriophages and plant viruses also have unique advantages due to their immunomodulation capabilities. This review accounts for all such considerations. Additionally, we explore how attributes of nanotechnology can be utilized to develop successful nanomedicine-based vaccines for cancer therapy. This article is categorized under: Nanotechnology Approaches to Biology > Nanoscale Systems in Biology Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease.

Exploring the Interactions of Oncolytic Viral Therapy and Immunotherapy of Anti-CTLA-4 for Malignant Melanoma Mice Model

Oncolytic ability to direct target and lyse tumor cells makes oncolytic virus therapy (OVT) a promising approach to treating cancer. Despite its therapeutic potential to stimulate anti-tumor immune responses, it also has immunosuppressive effects. The efficacy of OVTs as monotherapies can be enhanced by appropriate adjuvant therapy such as anti-CTLA-4. In this paper, we propose a mathematical model to explore the interactions of combined therapy of oncolytic viruses and a checkpoint inhibitor, anti-CTLA-4. The model incorporates both the susceptible and infected tumor populations, natural killer cell population, virus population, tumor-specific immune populations, virus-specific immune populations, tumor suppressive cytokine IFN-g, and the effect of immune checkpoint inhibitor CTLA-4. In particular, we distinguish the tumor-specific immune abilities of CD8⁺ T, NK cells, and CD4⁺ T cells and describe the destructive ability of cytokine on tumor cells as well as the inhibitory capacity of CTLA-4 on various components. Our model is validated through the experimental results. We also investigate various dosing strategies to improve treatment outcomes. Our study reveals that tumor killing rate by cytokines, cytokine decay rate, and tumor growth rate play important roles on both the OVT monotherapy and the combination therapy. Moreover, parameters related to CD8⁺ T cell killing have a large impact on treatment outcomes with OVT alone, whereas parameters associated with IFN-g strongly influence treatment responses for the combined therapy. We also found that virus killing by NK cells may halt the desired spread of OVs and enhance the probability of tumor escape during the treatment. Our study reveals that it is the activation of host anti-tumor immune system responses rather than its direct destruction of the tumor cells plays a major biological function of the combined therapy.

Dynamic analysis of an age structure model for oncolytic virus therapy

Cancer is recognized as one of the serious diseases threatening human health. Oncolytic therapy is a safe and effective new cancer treatment method. Considering the limited ability of uninfected tumor cells to infect and the age of infected tumor cells have a significant effect on oncolytic therapy, an age-structured model of oncolytic therapy involving Holling-Ⅱ functional response is proposed to investigate the theoretical significance of oncolytic therapy. First, the existence and uniqueness of the solution is obtained. Furthermore, the stability of the system is confirmed. Then, the local stability and global stability of infection-free homeostasis are studied. The uniform persistence and local stability of the infected state are studied. The global stability of the infected state is proved by constructing the Lyapunov function. Finally, the theoretical results are verified by numerical simulation. The results show that when the tumor cells are at the appropriate age, injection of the right amount of oncolytic virus can achieve the purpose of tumor treatment.

Genetic and Immune Changes Associated with Disease Progression under the Pressure of Oncolytic Therapy in A Neuroblastoma Outlier Patient

Little is known about the effect of oncolytic adenovirotherapy on pediatric tumors. Here we present the clinical case of a refractory neuroblastoma that responded positively to Celyvir (ICOVIR-5 oncolytic adenovirus delivered by autologous mesenchymal stem cells) for several months. We analyzed samples during tumor evolution in order to identify molecular and mutational features that could explain the interactions between treatment and tumor and how the balance between both of them evolved. We identified a higher adaptive immune infiltration during stabilized disease compared to progression, and also a higher mutational rate and T-cell receptor (TCR) diversity during disease progression. Our results indicate an initial active role of the immune system controlling tumor growth during Celyvir therapy. The tumor eventually escaped from the control exerted by virotherapy through acquisition of resistance by the tumor microenvironment that exhausted the initial T cell response.

Mathematical Analysis of a Mathematical Model of Chemovirotherapy: Effect of Drug Infusion Method

A mathematical model for the treatment of cancer using chemovirotherapy is developed with the aim of determining the efficacy of three drug infusion methods: constant, single bolus, and periodic treatments. The model is in the form of ODEs and is further extended into DDEs to account for delays as a result of the infection of tumor cells by the virus and chemotherapeutic drug responses. Analysis of the model is carried out for each of the three drug infusion methods. Analytic solutions are determined where possible and stability analysis of both steady state solutions for the ODEs and DDEs is presented. The results indicate that constant and periodic drug infusion methods are more efficient compared to a single bolus injection. Numerical simulations show that with a large virus burst size, irrespective of the drug infusion method, chemovirotherapy is highly effective compared to either treatments. The simulations further show that both delays increase the period within which a tumor can be cleared from body tissue.

Antitumor effect of oncolytic virus and paclitaxel encapsulated in extracellular vesicles for lung cancer treatment

Standard of care for cancer is commonly a combination of surgery with radiotherapy or chemoradiotherapy. However, in some advanced cancer patients this approach might still remaininefficient and may cause many side effects, including severe complications and even death. Oncolytic viruses exhibit different anti-cancer mechanisms compared with conventional therapies, allowing the possibility for improved effect in cancer therapy. Chemotherapeutics combined with oncolytic viruses exhibit stronger cytotoxic responses and oncolysis. Here, we have investigated the systemic delivery of the oncolytic adenovirus and paclitaxel encapsulated in extracellular vesicles (EV) formulation that, in vitro, significantly increased the transduction ratio and the infectious titer when compared with the virus and paclitaxel alone. We demonstrated that the obtained EV formulation reduced the in vivo tumor growth in animal xenograft model of human lung cancer. Indeed, we found that combined treatment of oncolytic adenovirus and paclitaxel encapsulated in EV has enhanced anticancer effects both in vitro and in vivo in lung cancer models. Transcriptomic comparison carried out on the explanted xenografts from the different treatment groups revealed that only 5.3% of the differentially expressed genes were overlapping indicating that a de novo genetic program is triggered by the presence of the encapsulated paclitaxel: this novel genetic program might be responsible of the observed enhanced antitumor effect. Our work provides a promising approach combining anticancer drugs and viral therapies by intravenous EV delivery as a strategy for the lung cancer treatment.

Oncolytic viral therapy for pancreatic cancer

Outcomes of pancreatic adenocarcinoma (PDA) remain dismal despite extensive clinical investigation. Combination chemotherapy provides modest improvements in survival above best supportive care, and immunotherapy has thus far not proven effective. Nevertheless, growing insight into antitumor immunity and the tumor microenvironment has inspired the discovery of novel agents targeting PDA. Oncolytic viruses represent an emerging class of immunotherapeutic agents that have undergone extensive preclinical investigation and warrant further investigation in well-designed clinical trials.

ΔPK oncolytic activity includes modulation of the tumour cell milieu

Oncolytic virotherapy is a unique cancer therapeutic that encompasses tumour cell lysis through both virus replication and programmed cell death (PCD) pathways. Nonetheless, clinical efficacy is relatively modest, likely related to the immunosuppressive tumour milieu. Our studies use the herpes simplex virus type 2 (HSV-2)-based oncolytic virus ΔPK that has documented anti-tumour activity associated with virus replication, PCD and cancer stem cell lysis. They are designed to examine whether ΔPK-mediated oncolysis includes the ability to reverse the immunosuppressive tumour microenvironment by altering the balance of cytokines directly secreted by the melanoma cells and to define its mechanism. Here, we show that melanoma cells secreted the immunosuppressive cytokine IL-10, and that secretion was inhibited by ΔPK through virus replication and c-Jun N-terminal kinase/c-Jun activation. ΔPK-induced IL-10 inhibition upregulated surface expression of MHC class I chain-related protein A, the ligand for the activating NKG2D receptor expressed on NK- and cytotoxic T-cells. Concomitantly, ΔPK also upregulated the secretion of inflammatory cytokines TNF-α, granulocyte macrophage colony-stimulating factor and IL-1β through autophagy-mediated activation of Toll-like receptor 2 pathways and pyroptosis, and it inhibited the expression of the negative immune checkpoint regulator cytotoxic T-lymphocyte antigen 4. Pharmacologic inhibition of these processes significantly reduces the oncolytic activity of ΔPK.