Expanding cross-presenting dendritic cells enhances oncolytic virotherapy and is critical for long-term anti-tumor immunity

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.

Biomimetic piezoelectric nanomaterial-modified oral microrobots for targeted catalytic and immunotherapy of colorectal cancer

Lactic acid (LA) accumulation in the tumor microenvironment poses notable challenges to effective tumor immunotherapy. Here, an intelligent tumor treatment microrobot based on the unique physiological structure and metabolic characteristics of Veillonella atypica (VA) is proposed by loading Staphylococcus aureus cell membrane-coating BaTiO3 nanocubes (SAM@BTO) on the surface of VA cells (VA-SAM@BTO) via click chemical reaction. Following oral administration, VA-SAM@BTO accurately targeted orthotopic colorectal cancer through inflammatory targeting of SAM and hypoxic targeting of VA. Under in vitro ultrasonic stimulation, BTO catalyzed two reduction reactions (O2 → •O2- and CO2 → CO) and three oxidation reactions (H2O → •OH, GSH → GSSG, and LA → PA) simultaneously, effectively inducing immunogenic death of tumor cells. BTO catalyzed the oxidative coupling of VA cells metabolized LA, effectively disrupting the immunosuppressive microenvironment, improving dendritic cell maturation and macrophage M1 polarization, and increasing effector T cell proportions while decreasing regulatory T cell numbers, which facilitates synergetic catalysis and immunotherapy.

Self-adjuvanting polymeric nanovaccines enhance IFN production and cytotoxic T cell response

Vaccines represent one of the most powerful and cost-effective innovations for controlling a wide range of infectious diseases caused by various viruses and bacteria. Unlike mRNA and DNA-based vaccines, subunit vaccines carry no risk of insertional mutagenesis and can be lyophilized for convenient transportation and long-term storage. However, existing adjuvants are often associated with toxic effect and reactogenicity, necessitating expanding the repertoire of adjuvants with better biocompatibility, for instance, designing self-adjuvating polymeric carriers. We herein report a novel subunit vaccine delivery platform constructed via in situ free radical polymerization of C7A (2-(Hexamethyleneimino) ethyl methacrylate) and acrylamide around the surface of individual protein antigens. Using ovalbumin (OVA) as a model antigen, we observed substantial increases in both diameter (∼70 nm) and surface potential (-1.18 mV) following encapsulation, referred to as n(OVA)C7A. C7A's ultra pH sensitivity with a transition pH around 6.9 allows for rapid protonation in acidic environments. This property facilitates crucial processes such as endosomal escape and major histocompatibility complex (MHC)-I-mediated antigen presentation, culminating in the substantial CD8+ T cell activation. Additionally, compared to OVA nanocapsules without the C7A components and native OVA without modifications, we observed heightened B cell activation within the germinal center, along with remarkable increases in serum antibody and cytokine production. It's important to note that mounting evidence suggests that adjuvant effects, particularly its targeted stimulation of type I interferons (IFNs), can contribute to advantageous adaptive immune responses. Beyond its exceptional potency, the nanovaccine also demonstrated robust formation of immune memory and exhibited a favorable biosafety profile. These findings collectively underscore the promising potential of our nanovaccine in the realm of immunotherapy and vaccine development.

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.

Engineering Microorganisms for Cancer Immunotherapy

Cancer immunotherapy presents a promising approach to fight against cancer by utilizing the immune system. Recently, engineered microorganisms have emerged as a potential strategy in cancer immunotherapy. These microorganisms, including bacteria and viruses, can be designed and modified using synthetic biology and genetic engineering techniques to target cancer cells and modulate the immune system. This review delves into various microorganism-based therapies for cancer immunotherapy, encompassing strategies for enhancing efficacy while ensuring safety and ethical considerations. The development of these therapies holds immense potential in offering innovative personalized treatments for cancer.

Dendritic cell-targeted therapy expands CD8 T cell responses to bona-fide neoantigens in lung tumors

Cross-presentation by type 1 DCs (cDC1) is critical to induce and sustain antitumoral CD8 T cell responses to model antigens, in various tumor settings. However, the impact of cross-presenting cDC1 and the potential of DC-based therapies in tumors carrying varied levels of bona-fide neoantigens (neoAgs) remain unclear. Here we develop a hypermutated model of non-small cell lung cancer in female mice, encoding genuine MHC-I neoepitopes to study neoAgs-specific CD8 T cell responses in spontaneous settings and upon Flt3L + αCD40 (DC-therapy). We find that cDC1 are required to generate broad CD8 responses against a range of diverse neoAgs. DC-therapy promotes immunogenicity of weaker neoAgs and strongly inhibits the growth of high tumor-mutational burden (TMB) tumors. In contrast, low TMB tumors respond poorly to DC-therapy, generating mild CD8 T cell responses that are not sufficient to block progression. scRNA transcriptional analysis, immune profiling and functional assays unveil the changes induced by DC-therapy in lung tissues, which comprise accumulation of cDC1 with increased immunostimulatory properties and less exhausted effector CD8 T cells. We conclude that boosting cDC1 activity is critical to broaden the diversity of anti-tumoral CD8 T cell responses and to leverage neoAgs content for therapeutic advantage.

Integrating innate and adaptive immunity in oncolytic virus therapy

Oncolytic viruses (OVs), viruses engineered to lyse tumor cells, work hand in hand with the immune response. While for decades the field isolated lytic capability and viral spread to increase response to virotherapy, there is now a wealth of research that demonstrates the importance of immunity in the OV mechanism of action. In this review, we will cover how OVs interact with the innate immune system to fully activate the adaptive immune system and yield exceptional tumor clearances as well as look forward at combination therapies which can improve clinical responses.

Antigen cross-presentation by dendritic cells: A critical axis in cancer immunotherapy

Dendritic cells (DCs) are professional antigen-presenting cells that play a key role in shaping adaptive immunity. DCs have a unique ability to sample their environment, capture and process exogenous antigens into peptides that are then loaded onto major histocompatibility complex class I molecules for presentation to CD8+ T cells. This process, called cross-presentation, is essential for initiating and regulating CD8+ T cell responses against tumors and intracellular pathogens. In this review, we will discuss the role of DCs in cancer immunity, the molecular mechanisms underlying antigen cross-presentation by DCs, the immunosuppressive factors that limit the efficiency of this process in cancer, and approaches to overcome DC dysfunction and therapeutically promote antitumoral immunity.

Cytotoxicity as a form of immunogenic cell death leading to efficient tumor antigen cross-priming

Antigen cross-priming of CD8+ T cells is a critical process necessary for the effective expansion and activation of CD8+ T cells endowed with the ability to recognize and destroy tumor cells. The cross-presentation of tumor antigens to cross-prime CD8+ T cells is mainly mediated, if not only, by a subset of professional antigen-presenting cells termed type-1 conventional dendritic cells (cDC1). The demise of malignant cells can be immunogenic if it occurs in the context of premortem stress. These ways of dying are termed immunogenic cell death (ICD) and are associated with biochemical features favoring cDC1 for the efficient cross-priming of tumor antigens. Immunosurveillance and the success of immunotherapies heavily rely on the ability of cytotoxic immune cells, primarily CD8+ T cells and NK cells, to detect and eliminate tumor cells through mechanisms collectively known as cytotoxicity. Recent studies have revealed the significance of NK- and CTL-mediated cytotoxicity as a prominent form of immunogenic cell death, resulting in mechanisms that promote and sustain antigen-specific immune responses. This review focuses on the mechanisms underlying the cross-presentation of antigens released during tumor cell killing by cytotoxic immune cells, with an emphasis on the role of cDC1 cells. Indeed, cDC1s are instrumental in the effectiveness of most immunotherapies, underscoring the significance of tumor antigen cross-priming in contexts of immunogenic cell death. The notion of the potent immunogenicity of cell death resulting from NK or cytotoxic T lymphocyte (CTL)-mediated cytotoxicity has far-reaching implications for cancer immunotherapy.

The potential of mRNA vaccines in cancer nanomedicine and immunotherapy

Owing to their outstanding performance against COVID-19, mRNA vaccines have brought great hope for combating various incurable diseases, including cancer. Differences in the encoded proteins result in different molecular and cellular mechanisms of mRNA vaccines. With the rapid development of nanotechnology and molecular medicine, personalized antigen-encoding mRNA vaccines that enhance antigen presentation can trigger effective immune responses and prevent off-target toxicities. Herein, we review new insights into the influence of encoded antigens, cytokines, and other functional proteins on the mechanisms of mRNA vaccines. We also highlight the importance of delivery systems and chemical modifications for mRNA translation efficiency, stability, and targeting, and we discuss the potential problems and application prospects of mRNA vaccines as versatile tools for combating cancer.

Tumor vaccines: Toward multidimensional anti-tumor therapies

For decades, immunotherapies have offered hope for patients with advanced cancer. However, they show distinct benefits and limited clinical effects. Tumor vaccines have the potential to prime tumor-antigen-specific T cells and induce broad subsets of immune responses, ultimately eradicating tumor cells. Here, we classify tumor vaccines by their anti-tumor mechanisms, which include boosting the immune system, overcoming tumor immunosuppression, and modulating tumor angiogenesis. We focus on multidimensional tumor vaccine strategies using combinations of two or three of the above mechanisms, as these are superior to single-dimensional treatments. This review offers a perspective on tumor vaccine strategies and the future role of vaccine therapies in cancer treatment.

Biomimetic Nanophotosensitizer Amplifies Immunogenic Pyroptosis and Triggers Synergistic Cancer Therapy

Immunotherapy is considered to be an effective treatment for cancer and has drawn extensive interest. Nevertheless, the insufficient antigenicity and immunosuppressive tumor microenvironment often cause unsatisfactory therapeutic efficacy. Herein, a photo-activated reactive oxygen species (ROS) amplifying system (defined as "M-Cu-T") is developed to induce antitumor immune response by triggering a tumor-specific immunogenic pyroptosis. In M-Cu-T, M1 macrophage membrane-based vesicles are used for drug loading and tumor targeting, photosensitizers (meso-tetra(4-aminophenyl) porphyrin, TAPP) are used as a pyroptosis inducer, copper ions (Cu2+ ) can enhance ROS-induced pyroptosis by consuming antioxidant systems in cells. As expected, the prepared M-Cu-T targets enrichment into tumor cells and cascades the generation of ROS, which further induces pyroptosis through caspase 3-mediated gasdermin E (GSDME) cleavage under laser activation. The pyroptotic cancer cells accompanying secrete related pattern molecules, induce immunogenic cell death, and activate antitumor immunity for immunotherapy. An effective tumor ablation is observed in LLC and CT26 cancer mouse models. This study provides inspiration for boosting the immunogenicity and achieving satisfactory therapeutic effects in cancer therapy.

Engineering Non-Human RNA Viruses for Cancer Therapy

Alongside the development and progress in cancer immunotherapy, research in oncolytic viruses (OVs) continues advancing novel treatment strategies to the clinic. With almost 50 clinical trials carried out over the last decade, the opportunities for intervention using OVs are expanding beyond the old-fashioned concept of "lytic killers", with promising breakthrough therapeutic strategies focused on leveraging the immunostimulatory potential of different viral platforms. This review presents an overview of non-human-adapted RNA viruses engineered for cancer therapy. Moreover, we describe the diverse strategies employed to manipulate the genomes of these viruses to optimize their therapeutic capabilities. By focusing on different aspects of this particular group of viruses, we describe the insights into the promising advancements in the field of virotherapy and its potential to revolutionize cancer treatment.

Potential targeting of the tumor microenvironment to improve cancer virotherapy

In 2015, oncolytic virotherapy was approved for clinical use, and in 2017, recombinant adeno-associated virus (AAV) delivery was also approved. However, systemic administration remains challenging due to the limited number of viruses that successfully reach the target site. Although the US Food and Drug Administration (FDA) permits the use of higher doses of AAV to achieve greater rates of transduction, most AAV still accumulates in the liver, potentially leading to toxicity there and elsewhere. Targeting the tumor microenvironment is a promising strategy for cancer treatment due to the critical role of the tumor microenvironment in controlling tumor progression and influencing the response to therapies. Newly discovered evidence indicates that administration routes focusing on the tumor microenvironment can promote delivery specificity and transduction efficacy within the tumor. Here, we review approaches that involve modifying viral surface features, modulating the immune system, and targeting the physicochemical characteristics in tumor microenvironment to regulate therapeutic delivery. Targeting tumor acidosis presents advantages that can be leveraged to enhance virotherapy outcomes and to develop new therapeutic approaches that can be integrated with standard treatments.

Transcriptional regulation of dendritic cell development and function

Dendritic cells (DCs) are sentinel immune cells that form a critical bridge linking the innate and adaptive immune systems. Extensive research addressing the cellular origin and heterogeneity of the DC network has revealed the essential role played by the spatiotemporal activity of key transcription factors. In response to environmental signals DC mature but it is only following the sensing of environmental signals that DC can induce an antigen specific T cell response. Thus, whilst the coordinate action of transcription factors governs DC differentiation, sensing of environmental signals by DC is instrumental in shaping their functional properties. In this review, we provide an overview that focuses on recent advances in understanding the transcriptional networks that regulate the development of the reported DC subsets, shedding light on the function of different DC subsets. Specifically, we discuss the emerging knowledge on the heterogeneity of cDC2s, the ontogeny of pDCs, and the newly described DC subset, DC3. Additionally, we examine critical transcription factors such as IRF8, PU.1, and E2-2 and their regulatory mechanisms and downstream targets. We highlight the complex interplay between these transcription factors, which shape the DC transcriptome and influence their function in response to environmental stimuli. The information presented in this review provides essential insights into the regulation of DC development and function, which might have implications for developing novel therapeutic strategies for immune-related diseases.

Pattern recognition receptor agonists in pathogen vaccines mediate antitumor T-cell cross-priming

BACKGROUND

Cancer immunotherapies are generally effective in patients whose tumors contain a priori primed T-cells reactive to tumor antigens (TA). One approach to prime TA-reactive T-cells is to administer immunostimulatory molecules, cells, or pathogens directly to the tumor site, that is, in situ vaccination (ISV). We recently described an ISV using Flt3L to expand and recruit dendritic cells (DC), radiotherapy to load DC with TA, and pattern recognition receptor agonists (PRRa) to activate TA-loaded DC. While ISV trials using synthetic PRRa have yielded systemic tumor regressions, the optimal method to activate DCs is unknown.

METHODS

To discover optimal DC activators and increase access to clinical grade reagents, we assessed whether viral or bacterial components found in common pathogen vaccines are an effective source of natural PRRa (naPRRa). Using deep profiling (155-metric) of naPRRa immunomodulatory effects and gene editing of specific PRR, we defined specific signatures and molecular mechanisms by which naPRRa potentiate T-cell priming.

RESULTS

We observed that vaccine naPRRa can be even more potent in activating Flt3L-expanded murine and human DCs than synthetic PRRa, promoting cross-priming of TA-reactive T-cells. We developed a mechanistically diverse naPRRa combination (BCG, PedvaxHIB, Rabies) and noted more potent T-cell cross-priming than with any single naPRRa. The naPRRa triplet-as part of Flt3L-primed ISV-induced greater intratumoral CD8 T-cell infiltration, T-cells reactive to a newly defined tumorous neoantigen, durable tumor regressions.

CONCLUSIONS

This work provides rationale for the translation of pathogen vaccines as FDA-approved clinical-grade DC activators which could be exploited as immune-stimulants for early phase trials.

Immune responses elicited by ssRNA(-) oncolytic viruses in the host and in the tumor microenvironment

Oncolytic viruses (OVs) are at the forefront of biologicals for cancer treatment. They represent a diverse landscape of naturally occurring viral strains and genetically modified viruses that, either as single agents or as part of combination therapies, are being evaluated in preclinical and clinical settings. As the field gains momentum, the research on OVs has been shifting efforts to expand our understanding of the complex interplay between the virus, the tumor and the immune system, with the aim of rationally designing more efficient therapeutic interventions. Nowadays, the potential of an OV platform is no longer defined exclusively by the targeted replication and cancer cell killing capacities of the virus, but by its contribution as an immunostimulator, triggering the transformation of the immunosuppressive tumor microenvironment (TME) into a place where innate and adaptive immunity players can efficiently engage and lead the development of tumor-specific long-term memory responses. Here we review the immune mechanisms and host responses induced by ssRNA(-) (negative-sense single-stranded RNA) viruses as OV platforms. We focus on two ssRNA(-) OV candidates: Newcastle disease virus (NDV), an avian paramyxovirus with one of the longest histories of utilization as an OV, and influenza A (IAV) virus, a well-characterized human pathogen with extraordinary immunostimulatory capacities that is steadily advancing as an OV candidate through the development of recombinant IAV attenuated platforms.

Immune Checkpoint Inhibitor-Based Combination Therapy for Colorectal Cancer: An Overview

Colorectal cancer (CRC) is one of the most common diseases in the world. Tumor immunotherapy is an innovative cancer treatment that acts by activating the human body's autoimmune system. Immune checkpoint block has been shown to be effective in DNA deficient mismatch repair/microsatellite instability-high CRC. However, the therapeutic effect for proficient mismatch repair/microsatellite stability patients still requires further study and optimization. At present, the main CRC strategy is to combine other therapeutic methods, such as chemotherapy, targeted therapy, and radiotherapy. Here, we review the current status and the latest progress of immune checkpoint inhibitors in the treatment of CRC. At the same time, we consider therapeutic opportunities for transforming cold to hot, as well as perspectives on possible future therapies, which may be in great demand for drug-resistant patients.