Oncolytic Herpes Simplex Virus Type 1 Induces Immunogenic Cell Death Resulting in Maturation of BDCA-1+ Myeloid Dendritic Cells

Shifting cold to hot tumors by nanoparticle-loaded drugs and products

Cold tumors lack antitumor immunity and are resistant to therapy, representing a major challenge in cancer medicine. Because of the immunosuppressive spirit of the tumor microenvironment (TME), this form of tumor has a low response to immunotherapy, radiotherapy, and also chemotherapy. Cold tumors have low infiltration of immune cells and a high expression of co-inhibitory molecules, such as immune checkpoints and immunosuppressive molecules. Therefore, targeting TME and remodeling immunity in cold tumors can improve the chance of tumor repression after therapy. However, tumor stroma prevents the infiltration of inflammatory cells and hinders the penetration of diverse molecules and drugs. Nanoparticles are an intriguing tool for the delivery of immune modulatory agents and shifting cold to hot tumors. In this review article, we discuss the mechanisms underlying the ability of nanoparticles loaded with different drugs and products to modulate TME and enhance immune cell infiltration. We also focus on newest progresses in the design and development of nanoparticle-based strategies for changing cold to hot tumors. These include the use of nanoparticles for targeted delivery of immunomodulatory agents, such as cytokines, small molecules, and checkpoint inhibitors, and for co-delivery of chemotherapy drugs and immunomodulatory agents. Furthermore, we discuss the potential of nanoparticles for enhancing the efficacy of cancer vaccines and cell therapy for overcoming resistance to treatment.

Immunogenic cell death-based oncolytic virus therapy: A sharp sword of tumor immunotherapy

Tumor immunotherapy, especially immune checkpoint inhibitors (ICIs), has been applied in clinical practice, but low response to immune therapies remains a thorny issue. Oncolytic viruses (OVs) are considered promising for cancer treatment because they can selectively target and destroy tumor cells followed by spreading to nearby tumor tissues for a new round of infection. Immunogenic cell death (ICD), which is the major mechanism of OVs' anticancer effects, is induced by endoplasmic reticulum stress and reactive oxygen species overload after virus infection. Subsequent release of specific damage-associated molecular patterns (DAMPs) from different types of tumor cells can transform the tumor microenvironment from "cold" to "hot". In this paper, we broadly define ICD as those types of cell death that is immunogenic, and describe their signaling pathways respectively. Focusing on ICD, we also elucidate the advantages and disadvantages of recent combination therapies and their future prospects.

Advances in research on immunocyte iron metabolism, ferroptosis, and their regulatory roles in autoimmune and autoinflammatory diseases

Autoimmune diseases commonly affect various systems, but their etiology and pathogenesis remain unclear. Currently, increasing research has highlighted the role of ferroptosis in immune regulation, with immune cells being a crucial component of the body's immune system. This review provides an overview and discusses the relationship between ferroptosis, programmed cell death in immune cells, and autoimmune diseases. Additionally, it summarizes the role of various key targets of ferroptosis, such as GPX4 and TFR, in immune cell immune responses. Furthermore, the release of multiple molecules, including damage-associated molecular patterns (DAMPs), following cell death by ferroptosis, is examined, as these molecules further influence the differentiation and function of immune cells, thereby affecting the occurrence and progression of autoimmune diseases. Moreover, immune cells secrete immune factors or their metabolites, which also impact the occurrence of ferroptosis in target organs and tissues involved in autoimmune diseases. Iron chelators, chloroquine and its derivatives, antioxidants, chloroquine derivatives, and calreticulin have been demonstrated to be effective in animal studies for certain autoimmune diseases, exerting anti-inflammatory and immunomodulatory effects. Finally, a brief summary and future perspectives on the research of autoimmune diseases are provided, aiming to guide disease treatment strategies.

Comparison of the oncolytic activity of a replication-competent and a replication-deficient herpes simplex virus 1

In 2015, the oncolytic herpes simplex virus 1 (HSV-1) T-VEC (talimogene laherparepvec) was approved for intratumoral injection in non-resectable malignant melanoma. To determine whether viral replication is required for oncolytic activity, we compared replication-deficient HSV-1 d106S with replication-competent T-VEC. High infectious doses of HSV-1 d106S killed melanoma (n = 10), head-and-neck squamous cell carcinoma (n = 11), and chondrosarcoma cell lines (n = 2) significantly faster than T-VEC as measured by MTT metabolic activity, while low doses of T-VEC were more effective over time. HSV-1 d106S and, to a lesser extent T-VEC, triggered caspase-dependent early apoptosis as shown by pan-caspase inhibition and specific induction of caspases 3/7, 8, and 9. HSV-1 d106S induced a higher ratio of apoptosis-inducing infected cell protein (ICP) 0 to apoptosis-blocking ICP6 than T-VEC. T-VEC was oncolytic for an extended period of time as viral replication continued, which could be partially blocked by the antiviral drug aciclovir. High doses of T-VEC, but not HSV-1 d106S, increased interferon-β mRNA as part of the intrinsic immune response. When markers of immunogenic cell death were assessed, ATP was released more efficiently in the context of T-VEC than HSV-1 d106S infection, whereas HMGB1 was induced comparatively well. Overall, the early oncolytic effect on three different tumour entities was stronger with the non-replicative strain, while the replication-competent virus elicited a stronger innate immune response and more pronounced immunogenic cell death.

Nanocarrier-Mediated Immunogenic Cell Death for Melanoma Treatment

Melanoma, a highly aggressive skin tumor, exhibits notable features including heterogeneity, a high mutational load, and innate immune escape. Despite advancements in melanoma treatment, current immunotherapies fail to fully exploit the immune system's maximum potential. Activating immunogenic cell death (ICD) holds promise in enhancing tumor cell immunogenicity, stimulating immune amplification response, improving drug sensitivity, and eliminating tumors. Nanotechnology-enabled ICD has emerged as a compelling therapeutic strategy for augmenting cancer immunotherapy. Nanoparticles possess versatile attributes, such as prolonged blood circulation, stability, and tumor-targeting capabilities, rendering them ideal for drug delivery. In this review, we elucidate the mechanisms underlying ICD induction and associated therapeutic strategies. Additionally, we provide a concise overview of the immune stress response associated with ICD and explore the potential synergistic benefits of combining ICD induction methods with the utilization of nanocarriers.

Gold standard assessment of immunogenic cell death induced by photodynamic therapy: From in vitro to tumor mouse models and anti-cancer vaccination strategies

The discovery of the concept of immunogenic cell death (ICD) is a cornerstone in the development of novel anti-cancer immunotherapeutic approaches. Induction of the ICD pathway by specific anti-cancer therapeutic regimens can eliminate cancer cells by directly killing them during therapy and by activation of strong and specific anti-cancer immunity, leading to a long-lasting immunological memory that prevents cancer recurrence. ICD encompasses different forms of regulated cell death and can be triggered by many anti-cancer treatment modalities, including photodynamic therapy (PDT). PDT is a multistep procedure involving the accumulation of a light-sensitive dye known as a photosensitizer (PS) in tumor cells, followed by its activation by irradiation with a light of an appropriate wavelength. In the presence of molecular oxygen, the irradiated PS leads to the generation of cytotoxic reactive oxygen species, which can lead to ICD induction in the cancer cells. Here, we first describe in vitro methods to help optimize the PDT procedure for a specific PS. We also provide a collection of protocols and techniques for assessing ICD in vitro, including analysis of the emission of damage associated molecular patterns (DAMPs), efferocytosis, and the maturation and activation state of antigen presenting cells. Next, we describe in detail protocols for diverse tumor mouse models for assessing and characterizing ICD in vivo, such as murine tumor vaccination models. Finally, as an immunotherapeutic vaccine, we suggest using either PDT-induced dead cancer cells, preferably undergoing ICD, or dendritic cells loaded with lysates of PDT-induced cancer cells in a syngeneic orthotopic glioma model. Overall, this methodological article provides a quantitative, comprehensive set of validated tools that can be successfully used, with some adaptations, to identify, optimize and validate novel PSs in vitro and in vivo for the efficient induction of ICD during photodynamic treatment.

NET-targeted therapy: effects, limitations, and potential strategies to enhance treatment efficacy

Neutrophil extracellular traps (NETs) are complex structures released by activated neutrophils during inflammatory responses. Due to their unique potential for causing tissue damage and modulating immune responses, there is increasing interest in studying these structures as potential targets for the treatment of infectious diseases, autoimmune diseases, and cancer. However, therapeutic targeting of NETs might trigger deleterious effects that may limit treatment efficacy. NET disruption may increase the microbial load in infection; in autoimmunity, NET targeting might impair peripheral tolerance, but it might reduce adaptive immune responses in cancer. In this review, we explore the therapeutic and deleterious effects of NET-targeted therapy while shedding light on novel strategies to overcome treatment-related limitations and enhance treatment efficacy.

Enhancing Immunogenicity in Metastatic Melanoma: Adjuvant Therapies to Promote the Anti-Tumor Immune Response

Advanced melanoma is an aggressive form of skin cancer characterized by low survival rates. Less than 50% of advanced melanoma patients respond to current therapies, and of those patients that do respond, many present with tumor recurrence due to resistance. The immunosuppressive tumor-immune microenvironment (TIME) remains a major obstacle in melanoma therapy. Adjuvant treatment modalities that enhance anti-tumor immune cell function are associated with improved patient response. One potential mechanism to stimulate the anti-tumor immune response is by inducing immunogenic cell death (ICD) in tumors. ICD leads to the release of damage-associated molecular patterns within the TIME, subsequently promoting antigen presentation and anti-tumor immunity. This review summarizes relevant concepts and mechanisms underlying ICD and introduces the potential of non-ablative low-intensity focused ultrasound (LOFU) as an immune-priming therapy that can be combined with ICD-inducing focal ablative therapies to promote an anti-melanoma immune response.

Oncolytic virotherapies for pediatric tumors

INTRODUCTION

Many pediatric patients with malignant tumors continue to suffer poor outcomes. The current standard of care includes maximum safe surgical resection followed by chemotherapy and radiation which may be associated with considerable long-term morbidity. The emergence of oncolytic virotherapy (OVT) may provide an alternative or adjuvant treatment for pediatric oncology patients.

AREAS COVERED

We reviewed seven virus types that have been investigated in past or ongoing pediatric tumor clinical trials: adenovirus (AdV-tk, Celyvir, DNX-2401, VCN-01, Ad-TD-nsIL-12), herpes simplex virus (G207, HSV-1716), vaccinia (JX-594), reovirus (pelareorep), poliovirus (PVSRIPO), measles virus (MV-NIS), and Senecavirus A (SVV-001). For each virus, we discuss the mechanism of tumor-specific replication and cytotoxicity as well as key findings of preclinical and clinical studies.

EXPERT OPINION

Substantial progress has been made in the past 10 years regarding the clinical use of OVT. From our review, OVT has favorable safety profiles compared to chemotherapy and radiation treatment. However, the antitumor effects of OVT remain variable depending on tumor type and viral agent used. Although the widespread adoption of OVT faces many challenges, we are optimistic that OVT will play an important role alongside standard chemotherapy and radiotherapy for the treatment of malignant pediatric solid tumors in the future.

Novel technologies for applying immune checkpoint blockers

Cancer cells develop several ways to subdue the immune system among others via upregulation of inhibitory immune checkpoint (ICP) proteins. These ICPs paralyze immune effector cells and thereby enable unfettered tumor growth. Monoclonal antibodies (mAbs) that block ICPs can prevent immune exhaustion. Due to their outstanding effects, mAbs revolutionized the field of cancer immunotherapy. However, current ICP therapy regimens suffer from issues related to systemic administration of mAbs, including the onset of immune related adverse events, poor pharmacokinetics, limited tumor accessibility and immunogenicity. These drawbacks and new insights on spatiality prompted the exploration of novel administration routes for mAbs for instance peritumoral delivery. Moreover, novel ICP drug classes that are adept to novel delivery technologies were developed to circumvent the drawbacks of mAbs. We therefore review the state-of-the-art and novel delivery strategies of ICP drugs.

Oncolytic viruses-modulated immunogenic cell death, apoptosis and autophagy linking to virotherapy and cancer immune response

Recent reports have revealed that oncolytic viruses (OVs) play a significant role in cancer therapy. The infection of OVs such as oncolytic vaccinia virus (OVV), vesicular stomatitis virus (VSV), parvovirus, mammalian reovirus (MRV), human adenovirus, Newcastle disease virus (NDV), herpes simplex virus (HSV), avian reovirus (ARV), Orf virus (ORFV), inactivated Sendai virus (ISV), enterovirus, and coxsackievirus offer unique opportunities in immunotherapy through diverse and dynamic pathways. This mini-review focuses on the mechanisms of OVs-mediated virotherapy and their effects on immunogenic cell death (ICD), apoptosis, autophagy and regulation of the immune system.

Immunogenic cell death: The cornerstone of oncolytic viro-immunotherapy

According to the World Health Organization, cancer is one of the leading global health concerns, causing nearly 10 million deaths in 2020. While classical chemotherapeutics produce strong cytotoxicity on cancer cells, they carry limitations of drug resistance and off-target effects and sometimes fail to elicit adequate antitumor protection against tumor relapse. Additionally, most cancer cells have developed various ways to escape immune surveillance. Nevertheless, novel anticancer strategies such as oncolytic viro-immunotherapy can trigger immunogenic cell death (ICD), which can quickly grasp the attention of the host defense machinery, resulting in an ensuing antitumor immune response. Specifically, oncolytic viruses (OVs) can infect and destroy targeted cancer cells and stimulate the immune system by exposing pathogen-associated molecular patterns (PAMPs) and damage-associated molecular patterns (DAMPs) to promote inflammatory reactions, and concomitantly prime and induce antitumor immunity by the release of neoantigens from the damaged cancer cells. Thus, OVs can serve as a novel system to sensitize tumor cells for promising immunotherapies. This review discusses the concept of ICD in cancer, centralizing ICD-associated danger signals and their consequence in antitumor responses and ICD induced by OVs. We also shed light on the potential strategies to enhance the immunogenicity of OVs, including the use of genetically modified OVs and their combination with ICD-enhancing agents, which are helpful as forthcoming anticancer regimens.

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

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