Cytokines in oncolytic virotherapy

A viral attack on brain tumors: the potential of oncolytic virus therapy

Managing malignant brain tumors remains a significant therapeutic hurdle that necessitates further research to comprehend their treatment potential fully. Oncolytic viruses (OVs) offer many opportunities for predicting and combating tumors through several mechanisms, with both preclinical and clinical studies demonstrating potential. OV therapy has emerged as a potent and effective method with a dual mechanism. Developing innovative and effective strategies for virus transduction, coupled with immune checkpoint inhibitors or chemotherapy drugs, strengthens this new technique. Furthermore, the discovery and creation of new OVs that can seamlessly integrate gene therapy strategies, such as cytotoxic, anti-angiogenic, and immunostimulatory, are promising advancements. This review presents an overview of the latest advancements in OVs transduction for brain cancer, focusing on the safety and effectiveness of G207, G47Δ, M032, rQNestin34.5v.2, C134, DNX-2401, Ad-TD-nsIL12, NSC-CRAd-S-p7, TG6002, and PVSRIPO. These are evaluated in both preclinical and clinical models of various brain tumors.

Tutorial: design, production and testing of oncolytic viruses for cancer immunotherapy

Oncolytic viruses (OVs) represent a novel class of cancer immunotherapy agents that preferentially infect and kill cancer cells and promote protective antitumor immunity. Furthermore, OVs can be used in combination with established or upcoming immunotherapeutic agents, especially immune checkpoint inhibitors, to efficiently target a wide range of malignancies. The development of OV-based therapy involves three major steps before clinical evaluation: design, production and preclinical testing. OVs can be designed as natural or engineered strains and subsequently selected for their ability to kill a broad spectrum of cancer cells rather than normal, healthy cells. OV selection is further influenced by multiple factors, such as the availability of a specific viral platform, cancer cell permissivity, the need for genetic engineering to render the virus non-pathogenic and/or more effective and logistical considerations around the use of OVs within the laboratory or clinical setting. Selected OVs are then produced and tested for their anticancer potential by using syngeneic, xenograft or humanized preclinical models wherein immunocompromised and immunocompetent setups are used to elucidate their direct oncolytic ability as well as indirect immunotherapeutic potential in vivo. Finally, OVs demonstrating the desired anticancer potential progress toward translation in patients with cancer. This tutorial provides guidelines for the design, production and preclinical testing of OVs, emphasizing considerations specific to OV technology that determine their clinical utility as cancer immunotherapy agents.

Octyl itaconate enhances VSVΔ51 oncolytic virotherapy by multitarget inhibition of antiviral and inflammatory pathways

The presence of heterogeneity in responses to oncolytic virotherapy poses a barrier to clinical effectiveness, as resistance to this treatment can occur through the inhibition of viral spread within the tumor, potentially leading to treatment failures. Here we show that 4-octyl itaconate (4-OI), a chemical derivative of the Krebs cycle-derived metabolite itaconate, enhances oncolytic virotherapy with VSVΔ51 in various models including human and murine resistant cancer cell lines, three-dimensional (3D) patient-derived colon tumoroids and organotypic brain tumor slices. Furthermore, 4-OI in combination with VSVΔ51 improves therapeutic outcomes in a resistant murine colon tumor model. Mechanistically, we find that 4-OI suppresses antiviral immunity in cancer cells through the modification of cysteine residues in MAVS and IKKβ independently of the NRF2/KEAP1 axis. We propose that the combination of a metabolite-derived drug with an oncolytic virus agent can greatly improve anticancer therapeutic outcomes by direct interference with the type I IFN and NF-κB-mediated antiviral responses.

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.

Molecular Circuits of Immune Sensing and Response to Oncolytic Virotherapy

Oncolytic virotherapy is a promising immunotherapy approach for cancer treatment that utilizes viruses to preferentially infect and eliminate cancer cells while stimulating the immune response. In this review, we synthesize the current literature on the molecular circuits of immune sensing and response to oncolytic virotherapy, focusing on viral DNA or RNA sensing by infected cells, cytokine and danger-associated-signal sensing by neighboring cells, and the subsequent downstream activation of immune pathways. These sequential sense-and-response mechanisms involve the triggering of molecular sensors by viruses or infected cells to activate transcription factors and related genes for a breadth of immune responses. We describe how the molecular signals induced in the tumor upon virotherapy can trigger diverse immune signaling pathways, activating both antigen-presenting-cell-based innate and T cell-based adaptive immune responses. Insights into these complex mechanisms provide valuable knowledge for enhancing oncolytic virotherapy strategies.

Personalizing Oncolytic Immunovirotherapy Approaches

Development of successful cancer therapeutics requires exploration of the differences in genetics, metabolism, and interactions with the immune system among malignant and normal cells. The clinical observation of spontaneous tumor regression following natural infection with microorganism has created the premise of their use as cancer therapeutics. Oncolytic viruses (OVs) originate from viruses with attenuated virulence in humans, well-characterized vaccine strains of known human pathogens, or engineered replication-deficient viral vectors. Their selectivity is based on receptor expression level and post entry restriction factors that favor replication in the tumor, while keeping the normal cells unharmed. Clinical trials have demonstrated a wide range of patient responses to virotherapy, with subgroups of patients significantly benefiting from OV administration. Tumor-specific gene signatures, including antiviral interferon-stimulated gene (ISG) expression profile, have demonstrated a strong correlation with tumor permissiveness to infection. Furthermore, the combination of OVs with immunotherapeutics, including anticancer vaccines and immune checkpoint inhibitors [ICIs, such as anti-PD-1/PD-L1 or anti-CTLA-4 and chimeric antigen receptor (CAR)-T or CAR-NK cells], could synergistically improve the therapeutic outcome. Creating response prediction algorithms represents an important step for the transition to individualized immunovirotherapy approaches in the clinic. Integrative predictors could include tumor mutational burden (TMB), inflammatory gene signature, phenotype of tumor-infiltrating lymphocytes, tumor microenvironment (TME), and immune checkpoint receptor expression on both immune and target cells. Additionally, the gut microbiota has recently been recognized as a systemic immunomodulatory factor and could further be used in the optimization of individualized immunovirotherapy algorithms.

Improving the therapeutic efficacy of oncolytic viruses for cancer: targeting macrophages

Oncolytic viruses (OVs) for cancer treatment are in a rapid stage of development, and the direct tumor lysis and activation of a comprehensive host immune response are irreplaceable advantages of cancer immunotherapy. However, excessive antiviral immune responses also restrict the spread of OVs in vivo and the infection of tumor cells. Macrophages are functionally diverse innate immune cells that phagocytose tumor cells and present antigens to activate the immune response, while also limiting the delivery of OVs to tumors. Studies have shown that the functional propensity of macrophages between OVs and tumor cells affects the overall therapeutic effect of oncolytic virotherapy. How to effectively avoid the restrictive effect of macrophages on OVs and reshape the function of tumor-associated macrophages in oncolytic virotherapy is an important challenge we are now facing. Here, we review and summarize the complex dual role of macrophages in oncolytic virotherapy, highlighting how the functional characteristics of macrophage plasticity can be utilized to cooperate with OVs to enhance anti-tumor effects, as well as highlighting the importance of designing and optimizing delivery modalities for OVs in the future.

Viral Vectors Expressing Interleukin 2 for Cancer Immunotherapy

Interleukin 2 (IL-2) plays a crucial role in T cell growth and survival, enhancing the cytotoxic activity of natural killer and cytotoxic T cells and thus functioning as a versatile master proinflammatory anticancer cytokine. The FDA has approved IL-2 cytokine therapy for the treatment of metastatic melanoma and metastatic renal cell carcinoma. However, IL-2 therapy has significant constraints, including a short serum half-life, low tumor accumulation, and life-threatening toxicities associated with high doses. Oncolytic viruses (OVs) offer a promising option for cancer immunotherapy, selectively targeting and destroying cancer cells while sparing healthy cells. Numerous studies have demonstrated the successful delivery of IL-2 to the tumor microenvironment without compromising safety using OVs such as vaccinia, Sendai, parvo, Newcastle disease, tanapox, and adenoviruses. Additionally, by engineering OVs to coexpress IL-2 with other anticancer transgenes, the immune properties of IL-2 can be further enhanced. Preclinical and clinical studies have shown promising antitumor effects of IL-2-expressing viral vectors, either alone or in combination with other anticancer therapies. This review summarizes the therapeutic potential of IL-2-expressing viral vectors and their antitumor mechanisms of action.

Oncolytic Virus Engineering and Utilizations: Cancer Immunotherapy Perspective

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

The Clinical Advances of Oncolytic Viruses in Cancer Immunotherapy

A promising future for oncology treatment has been brought about by the emergence of a novel approach utilizing oncolytic viruses in cancer immunotherapy. Oncolytic viruses are viruses that have been exploited genetically to assault malignant cells and activate a robust immune response. Several techniques have been developed to endow viruses with an oncolytic activity through genetic engineering. For instance, redirection capsid modification, stimulation of anti-neoplastic immune response, and genetically arming viruses with cytokines such as IL-12. Oncolytic viral clinical outcomes are sought after, particularly in more advanced cancers. The effectiveness and safety profile of the oncolytic virus in clinical studies with or without the combination of standard treatment (chemotherapy, radiotherapy, or primary excision) has been assessed using response evaluation criteria in solid tumors (RECIST). This review will comprehensively outline the most recent clinical applications and provide the results from various phases of clinical trials in a variety of cancers in the latest published literature.

Oncolytic BHV-1 Is Sufficient to Induce Immunogenic Cell Death and Synergizes with Low-Dose Chemotherapy to Dampen Immunosuppressive T Regulatory Cells

Immunogenic cell death (ICD) can switch immunologically "cold" tumors "hot", making them sensitive to immune checkpoint inhibitor (ICI) therapy. Many therapeutic platforms combine multiple modalities such as oncolytic viruses (OVs) and low-dose chemotherapy to induce ICD and improve prognostic outcomes. We previously detailed many unique properties of oncolytic bovine herpesvirus type 1 (oBHV) that suggest widespread clinical utility. Here, we show for the first time, the ability of oBHV monotherapy to induce bona fide ICD and tumor-specific activation of circulating CD8⁺ T cells in a syngeneic murine model of melanoma. The addition of low-dose mitomycin C (MMC) was necessary to fully synergize with ICI through early recruitment of CD8⁺ T cells and reduced infiltration of highly suppressive PD-1⁺ Tregs. Cytokine and gene expression analyses within treated tumors suggest that the addition of MMC to oBHV therapy shifts the immune response from predominantly anti-viral, as evidenced by a high level of interferon-stimulated genes, to one that stimulates myeloid cells, antigen presentation and adaptive processes. Collectively, these data provide mechanistic insights into how oBHV-mediated therapy modalities overcome immune suppressive tumor microenvironments to enable the efficacy of ICI therapy.

The emerging field of oncolytic virus-based cancer immunotherapy

Oncolytic viruses (OVs) provide novel and promising therapeutic options for patients with cancers resistant to traditional therapies. Natural or genetically modified OVs are multifaceted tumor killers. They directly lyse tumor cells while sparing normal cells, and indirectly potentiate antitumor immunity by releasing antigens and activating inflammatory responses in the tumor microenvironment. However, some limitations, such as limited penetration of OVs into tumors, short persistence, and the host antiviral immune response, are impeding the broad translation of oncolytic virotherapy into the clinic. If these challenges can be overcome, combination therapies, such as OVs plus immune checkpoint blockade (ICB), chimeric antigen receptor (CAR) T cells, or CAR natural killer (NK) cells, may provide powerful therapeutic platforms in the clinic.

CXCL10 Chemokine: A Critical Player in RNA and DNA Viral Infections

Chemokines constitute a group of small, secreted proteins that regulate leukocyte migration and contribute to their activation. Chemokines are crucial inflammatory mediators that play a key role in managing viral infections, during which the profile of chemokine expression helps shape the immune response and regulate viral clearance, improving clinical outcome. In particular, the chemokine ligand CXCL10 and its receptor CXCR3 were explored in a plethora of RNA and DNA viral infections. In this review, we highlight the expression profile and role of the CXCL10/CXCR3 axis in the host defense against a variety of RNA and DNA viral infections. We also discuss the interactions among viruses and host cells that trigger CXCL10 expression, as well as the signaling cascades induced in CXCR3 positive cells.

Current landscape and perspective of oncolytic viruses and their combination therapies

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Oncolytic virotherapy has become an important branch of cancer immunotherapy in clinical practice.

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Multiple viruses can be engineered to be OVs and armed with anticancer genes to enhance their efficacy.

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OVs can reshape TME and produce synergistic anticancer efficacy when combined with other therapies.

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Safety and effectiveness are the main direction of future research and development of OVs.

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.

Advances and Hurdles in CAR T Cell Immune Therapy for Solid Tumors

Simple Summary

Chimeric antigen receptor (CAR) T cells are genetically engineered T cells that recognize markers present on tumor cells and drive the degradation of the tumor itself. CAR T immunotherapy has obtained remarkable success in targeting a number of blood malignancies; however, its outcome is typically modest when applied to solid tumors, because of specific structural, biological, and metabolic aspects of the solid tumor environment. This article offers an overview of the interactions between CAR T cells and the solid tumor microenvironment, highlighting the main strategies that have been attempted to overcome CAR T suppression, both in preclinical models and in clinical trials.

Abstract

Chimeric antigen receptor (CAR) T cells in solid tumors have so far yielded limited results, in terms of therapeutic effects, as compared to the dramatic results observed for hematological malignancies. Many factors involve both the tumor cells and the microenvironment. The lack of specific target antigens and severe, potentially fatal, toxicities caused by on-target off-tumor toxicities constitute major hurdles. Furthermore, the tumor microenvironment is usually characterized by chronic inflammation, the presence of immunosuppressive molecules, and immune cells that can reduce CAR T cell efficacy and facilitate antigen escape. Nonetheless, solid tumors are under investigation as possible targets despite their complexity, which represents a significant challenge. In preclinical mouse models, CAR T cells are able to efficiently recognize and kill several tumor xenografts. Overall, in the next few years, there will be intensive research into optimizing novel cell therapies to improve their effector functions and keep untoward effects in check. In this review, we provide an update on the state-of-the-art CAR T cell therapies in solid tumors, focusing on the preclinical studies and preliminary clinical findings aimed at developing optimal strategies to reduce toxicity and improve efficacy.

Design Strategies and Precautions for Using Vaccinia Virus in Tumor Virotherapy

Oncolytic virotherapy has emerged as a novel form of cancer immunotherapy. Oncolytic viruses (OVs) can directly infect and lyse the tumor cells, and modulate the beneficial immune microenvironment. Vaccinia virus (VACV) is a promising oncolytic vector because of its high safety, easy gene editing, and tumor intrinsic selectivity. To further improve the safety, tumor-targeting ability, and OV-induced cancer-specific immune activation, various approaches have been used to modify OVs. The recombinant oncolytic VACVs with deleting viral virulence factors and/or arming various therapeutic genes have displayed better therapeutic effects in multiple tumor models. Moreover, the combination of OVs with other cancer immunotherapeutic approaches, such as immune checkpoint inhibitors and CAR-T cells, has the potential to improve the outcome in cancer patients. This will open up new possibilities for the application of OVs in cancer treatment, especially for personalized cancer therapies.

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

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

Hydrogel-based co-delivery of CIK cells and oncolytic adenovirus armed with IL12 and IL15 for cancer immunotherapy

Intratumoral injection of various effector cells combined with oncolytic adenovirus expressing antitumor cytokines exert an effective antitumor immune effect by oncolysis and altering the tumor microenvironment. However, this combination therapy had certain limitations. When used in high concentrations, effector cells and oncolytic viruses can spread rapidly to surrounding non-target tissues. And because both therapies used in combination are immunogenic and exhibit shorter biological activity, multiple injections were required to attain an adequate therapeutic index. To overcome these drawbacks, we encapsulated gelatin-based hydrogel capable of co-deliver oncolytic adenovirus armed with IL12 and IL15 (CRAd-IL12-IL15) and CIK cells for enhancing and prolonging the antitumor effects of both therapies after a single intratumoral injection. The injectable and biodegradable hydrogel reduced the dispersion of high-dose oncolytic adenovirus and CIK cells from the injection site to the liver and other non-target tissues. In this study, a novel oncolytic adenoviral vector CRAd-IL12-IL15 was constructed to verify the cytokine expression and oncolytic ability, which can upregulate the expression levels of Bcl-2, Cish and Gzmb in tumor cells. The CRAd-IL12-IL15 + CIKs/gelatin treatment maintained sustained release of CRAd-IL12-IL15 and active CIK cells over a longer period of time, attenuating the antiviral immune response against adenovirus. In conclusion, the results suggested that hydrogel-mediated co-delivery of CRAd-IL12-IL15 and CIK cells might be a an approach to overcome limitations. Both treatments could be effectively retained in tumor tissue and sustained to induce potent anti-tumor immune responses with a single administration.

Comprehensive characterization of tumor immune landscape following oncolytic virotherapy by single-cell RNA sequencing

An important mechanism of oncolytic virotherapy in ameliorating cancer immunotherapy is by inducing significant changes in the immune landscape in the tumor microenvironment (TME). Despite this notion and the potential therapeutic implications, a comprehensive analysis of the immune changes in carcinomas induced by virotherapy has not yet been elucidated. We conducted single-cell RNA sequencing analysis on carcinomas treated with an HSV-2-based oncolytic virus to characterize the immunogenic changes in the TME. We specifically analyzed and compared the immune cell composition between viral treated and untreated tumors. We also applied CellChat to analyze the complex interactions among the infiltrated immune cells. Our data revealed significant infiltration of B cells in addition to other important immune cells, including CD4+, CD8+, and NK cells following virotherapy. Further analysis identified distinct subset compositions of the infiltrated immune cells and their activation status upon virotherapy. The intensive interactions among the infiltrated immune cells as revealed by CellChat analysis may further shape the immune landscape in favor of generating antitumor immunity. Our findings will facilitate the design of new strategies in incorporating immunotherapy into virotherapy for clinical translation. Moreover, the significant infiltration of B cells makes it suitable for combining virotherapy with immune checkpoint inhibitors.

Triple-serotype chimeric oncolytic adenovirus exerts multiple synergistic mechanisms against solid tumors

Background

Oncolytic virotherapy has become an important branch of cancer immunotherapy. This study investigated the efficacy of an oncolytic adenovirus (OAV), OncoViron, with synergistic mechanisms in the treatment of multiple solid tumors.

Methods

An OAV, OncoViron, was constructed and investigated by cytological experiments and implanted tumor models of multiple solid tumor cell lines to certify its anticancer efficacy, the synergistic effects of viral oncolysis and transgene anticancer activity of OncoViron, as well as oncolytic virotherapy combined with immunotherapy, were also verified.

Results

The selective replication of OncoViron mediated high expression of anticancer factors, specifically targeted a variety of solid tumors and significantly inhibited cancer cell proliferation. On a variety of implanted solid tumor models in immunodeficient mice, immunocompetent mice, and humanized mice, OncoViron showed great anticancer effects on its own and in combination with programmed death 1 (PD-1) antibody and chimeric antigen receptor (CAR) T cells. Pathological examination, single-cell sequencing, and spatial transcriptome analysis of animal implanted tumor specimens confirmed that OncoViron significantly altered the gene expression profile of infected cancer cells, not only recruiting a large number of lymphocytes, natural killer cells, and mononuclear macrophages into tumor microenvironment (TME) and activated immune cells, especially T cells but also inducing M1 polarization of macrophages and promoting the release of more immune cytokines, thereby remodeling the TME for coordinating PD-1 antibody or CAR T therapy.

Conclusions

The chimeric OncoViron is a novel broad-spectrum anticancer product with multiple mechanisms of synergistic and potentiated immunotherapy, creating a good opportunity for combined immunotherapy against solid tumors.

TNF blockade enhances the efficacy of myxoma virus-based oncolytic virotherapy

BACKGROUND

Oncolytic virotherapy (OV) represents a method to treat a variety of solid tumors by inducing antitumor immune responses. While this therapy has been extremely efficacious in preclinical models, translating these successes into human patients has proven challenging. One of the major reasons for these failures is the existence of immune-regulatory mechanisms, which dampen the efficacy of virally induced antitumor immunity. Unfortunately, the full extent of these immune-regulatory pathways remains unclear.

METHODS

To address this issue, we generated a doubly recombinant, oncolytic myxoma virus which expresses both a soluble fragment of programmed cell death protein 1 (PD1) and an interleukin 12 (IL-12) fusion protein (vPD1/IL-12 (virus-expressing PD1 and IL-12)). We then tested the molecular impact and therapeutic efficacy of this construct in multiple models of disseminated disease to identify novel pathways, which are associated with poor therapeutic outcomes.

RESULTS

Our results demonstrate that vPD1/IL-12 causes robust inflammation during therapy including inducing high levels of tumor necrosis factor (TNF). Surprisingly, although expression of TNF has generally been assumed to be beneficial to OV, the presence of this TNF appears to inhibit therapeutic efficacy by reducing intratumoral T-cell viability. Likely because of this, disruption of the TNF pathway, either through genetic knockout or antibody-based blockade, significantly enhances the overall outcomes of vPD1/IL-12-based therapy that allows for the generation of complete cures in normally non-responsive models.

CONCLUSIONS

These data suggest that some aspects of OV-induced inflammation might represent a double-edged sword during therapy and that specific blockade of TNF might enhance the efficacy of these treatments.

Engineering strategies to enhance oncolytic viruses in cancer immunotherapy

Oncolytic viruses (OVs) are emerging as potentially useful platforms in treatment methods for patients with tumors. They preferentially target and kill tumor cells, leaving healthy cells unharmed. In addition to direct oncolysis, the essential and attractive aspect of oncolytic virotherapy is based on the intrinsic induction of both innate and adaptive immune responses. To further augment this efficacious response, OVs have been genetically engineered to express immune regulators that enhance or restore antitumor immunity. Recently, combinations of OVs with other immunotherapies, such as immune checkpoint inhibitors (ICIs), chimeric antigen receptors (CARs), antigen-specific T-cell receptors (TCRs) and autologous tumor-infiltrating lymphocytes (TILs), have led to promising progress in cancer treatment. This review summarizes the intrinsic mechanisms of OVs, describes the optimization strategies for using armed OVs to enhance the effects of antitumor immunity and highlights rational combinations of OVs with other immunotherapies in recent preclinical and clinical studies.

Development of Delivery Systems for Local Administration of Cytokines/Cytokine Gene-Directed Therapeutics: Modern Oncologic Implications

PURPOSE OF REVIEW

In this review, we discuss modern cytokine delivery systems in oncologic care, focusing on modalities being developed in the clinical trials or currently in use. These include pegylation, immune-cytokine drug conjugates, cytokine-expressing plasmid nanoparticles, nonviral cytokine nanoparticles, viral systems, and AcTakines.

RECENT FINDINGS

Cytokine therapy has the potential to contribute to cancer treatment options by modulating the immune system towards an improved antitumor response and has shown promise both independently and in combination with other immunotherapy agents. Despite promising preliminary studies, systemic toxicities and challenges with administration have limited the impact of unmodified cytokine therapy. In the last decade, novel delivery systems have been developed to address these challenges and facilitate cytokine-based oncologic treatments. Novel delivery systems provide potential solutions to decrease dose-limiting side effects, facilitate administration, and increase the therapeutic activity of cytokine treatments in oncology care. The expanding clinical and translational research in these systems provides an opportunity to augment the armamentarium of immune oncology and may represent the next frontier of cytokine-based immuno-oncology.

NK Cell Effector Functions and Bystander Tumor Cell Killing in Immunovirotherapy

Oncolytic virotherapy is a compelling strategy to combine cancer gene therapy with immunotherapy. Lytic virus replication in malignant cells not only enables localized transgene expression based on engineered vectors but also triggers immunogenic tumor cell death and elicits inflammation in the tumor microenvironment. Modified oncolytic viruses encoding immunomodulators have been developed to enhance antitumor immune effects and therapeutic efficacy. As one example, bispecific molecules that engage immune cells to exert antitumor cytotoxicity can be encoded within the viral vector. This chapter describes an in vitro coculture experiment to study functionality and antitumor efficacy of engineered measles vaccine strain virus encoding natural killer cell engagers. In a flow cytometry-based analysis, target cell death of noninfected bystander cancer cells and effector functions of primary human natural killer cells are investigated. This methodology can facilitate assessment of advanced oncolytic viral vectors for cancer immunotherapy.

Oncolytic Viruses: Newest Frontier for Cancer Immunotherapy

Cancer remains a leading cause of death worldwide. Despite many signs of progress, currently available cancer treatments often do not provide desired outcomes for too many cancers. Therefore, newer and more effective therapeutic approaches are needed. Oncolytic viruses (OVs) have emerged as a novel cancer treatment modality, which selectively targets and kills cancer cells while sparing normal ones. In the past several decades, many different OV candidates have been developed and tested in both laboratory settings as well as in cancer patient clinical trials. Many approaches have been taken to overcome the limitations of OVs, including engineering OVs to selectively activate anti-tumor immune responses. However, newer approaches like the combination of OVs with current immunotherapies to convert "immune-cold" tumors to "immune-hot" will almost certainly improve the potency of OVs. Here, we discuss strategies that are explored to further improve oncolytic virotherapy.

Trial watch: intratumoral immunotherapy

While chemotherapy and radiotherapy remain the first-line approaches for the management of most unresectable tumors, immunotherapy has emerged in the past two decades as a game-changing treatment, notably with the clinical success of immune checkpoint inhibitors. Immunotherapies aim at (re)activating anticancer immune responses which occur in two main steps: (1) the activation and expansion of tumor-specific T cells following cross-presentation of tumor antigens by specialized myeloid cells (priming phase); and (2) the immunological clearance of malignant cells by these antitumor T lymphocytes (effector phase). Therapeutic vaccines, adjuvants, monoclonal antibodies, cytokines, immunogenic cell death-inducing agents including oncolytic viruses, anthracycline-based chemotherapy and radiotherapy, as well as adoptive cell transfer, all act at different levels of this cascade to (re)instate cancer immunosurveillance. Intratumoral delivery of these immunotherapeutics is being tested in clinical trials to promote superior antitumor immune activity in the context of limited systemic toxicity.

Clinical Application of Cytokines in Cancer Immunotherapy

Cytokines are key components of the immune system and play pivotal roles in anticancer immune response. Cytokines as either therapeutic agents or targets hold clinical promise for cancer precise treatment. Here, we provide an overview of the various roles of cytokines in the cancer immunity cycle, with a particular focus on the clinical researches of cytokine-based drugs in cancer therapy. We review 27 cytokines in 2630 cancer clinical trials registered with ClinicalTrials.gov that had completed recruitment up to January 2021 while summarizing important cases for each cytokine. We also discuss recent progress in methods for improving the delivery efficiency, stability, biocompatibility, and availability of cytokines in therapeutic applications.

Oncolytic viruses encoding bispecific T cell engagers: a blueprint for emerging immunovirotherapies

Bispecific T cell engagers (BiTEs) are an innovative class of immunotherapeutics that redirect T cells to tumor surface antigens. While efficacious against certain hematological malignancies, limited bioavailability and severe toxicities have so far hampered broader clinical application, especially against solid tumors. Another emerging cancer immunotherapy are oncolytic viruses (OVs) which selectively infect and replicate in malignant cells, thereby mediating tumor vaccination effects. These oncotropic viruses can serve as vectors for tumor-targeted immunomodulation and synergize with other immunotherapies. In this article, we discuss the use of OVs to overcome challenges in BiTE therapy. We review the current state of the field, covering published preclinical studies as well as ongoing clinical investigations. We systematically introduce OV-BiTE vector design and characteristics as well as evidence for immune-stimulating and anti-tumor effects. Moreover, we address additional combination regimens, including CAR T cells and immune checkpoint inhibitors, and further strategies to modulate the tumor microenvironment using OV-BiTEs. The inherent complexity of these novel therapeutics highlights the importance of translational research including correlative studies in early-phase clinical trials. More broadly, OV-BiTEs can serve as a blueprint for diverse OV-based cancer immunotherapies.

Redirecting the Immune Microenvironment in Acute Myeloid Leukemia

Simple Summary

Despite remarkable progress in the outcome of childhood acute myeloid leukemia (AML), risk of relapse and refractory diseases remains high. Treatment of the chemo-refractory disease is restricted by dose-limiting therapy-related toxicities which necessitate alternative tolerable efficient therapeutic modalities. By disrupting its immune environment, leukemic blasts are known to gain the ability to evade immune surveillance and promote disease progression; therefore, many efforts have been made to redirect the immune system against malignant blasts. Deeper knowledge about immunologic alterations has paved the way to the discovery and development of novel targeted therapeutic concepts, which specifically override the immune evasion mechanisms to eradicate leukemic blasts. Herein, we review innovative immunotherapeutic strategies and their mechanisms of action in pediatric AML.

Abstract

Acute myeloid leukemia is a life-threatening malignant disorder arising in a complex and dysregulated microenvironment that, in part, promotes the leukemogenesis. Treatment of relapsed and refractory AML, despite the current overall success rates in management of pediatric AML, remains a challenge with limited options considering the heavy but unsuccessful pretreatments in these patients. For relapsed/refractory (R/R) patients, hematopoietic stem cell transplantation (HSCT) following ablative chemotherapy presents the only opportunity to cure AML. Even though in some cases immune-mediated graft-versus-leukemia (GvL) effect has been proven to efficiently eradicate leukemic blasts, the immune- and chemotherapy-related toxicities and adverse effects considerably restrict the feasibility and therapeutic power. Thus, immunotherapy presents a potent tool against acute leukemia but needs to be engineered to function more specifically and with decreased toxicity. To identify innovative immunotherapeutic approaches, sound knowledge concerning immune-evasive strategies of AML blasts and the clinical impact of an immune-privileged microenvironment is indispensable. Based on our knowledge to date, several promising immunotherapies are under clinical evaluation and further innovative approaches are on their way. In this review, we first focus on immunological dysregulations contributing to leukemogenesis and progression in AML. Second, we highlight the most promising therapeutic targets for redirecting the leukemic immunosuppressive microenvironment into a highly immunogenic environment again capable of anti-leukemic immune surveillance.