Targeted delivery of TLR3 agonist to tumor cells with single chain antibody fragment-conjugated nanoparticles induces type I-interferon response and apoptosis

Toll-like receptor 3: a double-edged sword

The discovery of Toll-like receptors (TLRs) and their role in dendritic cells earned the Nobel Prize for 2011 because TLRs profoundly enhanced our understanding of the immune system. Specifically, TLR3 is located within the endosomal compartments of dendritic cells and plays a crucial role in the immune response by acting as a pattern recognition receptor that detects both exogenous (viral) and endogenous (mammalian) double-stranded RNA. However, TLR3 activation is a double-edged sword in various immune-mediated diseases. On one hand, it can enhance anti-viral defenses and promote pathogen clearance, contributing to host protection. On the other hand, excessive or dysregulated TLR3 signaling can lead to chronic inflammation and tissue damage, exacerbating conditions such as autoimmune diseases, chronic viral infections, and cancer. In cancer, TLR3 expression has been linked to both favorable and poor prognoses, though the underlying mechanisms remain unclear. Recent clinical and preclinical advances have explored the use of TLR3 agonists in cancer immunotherapy, attempting to capitalize on their potential to enhance anti-tumor responses. The dual role of TLR3 highlights its complexity as a therapeutic target, necessitating careful modulation to maximize its protective effects while minimizing potential pathological consequences. In this review, we explore the intricate roles of TLR3 in immune responses across different disease contexts, including cancer, infections, autoimmune disorders, and allergies, highlighting both its protective and detrimental effects in these disorders, as well as progress in developing TLR3 agonists as part of the immunotherapy landscape.

Multi-targeted immunotherapeutics to treat B cell malignancies

The concept of multi-targeted immunotherapeutic systems has propelled the field of cancer immunotherapy into an exciting new era. Multi-effector molecules can be designed to engage with, and alter, the patient's immune system in a plethora of ways. The outcomes can vary from effector cell recruitment and activation upon recognition of a cancer cell, to a multipronged immune checkpoint blockade strategy disallowing evasion of the cancer cells by immune cells, or to direct cancer cell death upon engaging multiple cell surface receptors simultaneously. Here, we review the field of multi-specific immunotherapeutics implemented to treat B cell malignancies. The mechanistically diverse strategies are outlined and discussed; common B cell receptor antigen targeting strategies are outlined and summarized; and the challenges of the field are presented along with optimistic insights for the future.

Early activation of Toll-like receptor-3 reduces the pathological progression of Alzheimer's disease in APP/PS1 mouse

BACKGROUND

Toll-like receptor 3 (TLR3) plays an important role in the immune/inflammatory response in the nervous system and is a main pathological feature of Alzheimer's disease (AD). This study investigates the role of early activation of TLR3 in the pathophysiological process of AD.

METHODS

In the experiment, the agonist of TLR3, Poly(I:C), was intraperitoneally injected into the APP/PS1 mouse model of AD and wild-type control mice starting from the age of 4 to 9 months. At the age of 14 months, behavioral tests were conducted. Western blot and immunohistochemistry staining were used to evaluate the level of amyloid β-protein (Aβ), the activation of inflammatory cells, and neuron loss. In addition, the levels of inflammatory cytokines were measured using a quantitative polymerase chain reaction.

RESULTS

The results demonstrated that the early activation of TLR3 attenuated neuronal loss and neurobehavioral dysfunction. Moreover, the early activation of TLR3 reduced Aβ deposition, inhibited the activation of microglia and astrocytes, and decreased the transcription of pro-inflammatory factors in the hippocampus.

CONCLUSIONS

The results indicated that the activation of TLR3 by Poly (I:C) in the early stage of development of AD in a mouse model attenuated neuron loss and improved neurobehavioral functions. The underlying mechanisms could be attributed to its role in Aβ clearance, the inhibition of glial cells, and the regulation of neuroinflammation in the hippocampus.

Antibody conjugates for targeted delivery of Toll-like receptor 9 agonist to the tumor tissue

Imiquimod, a Toll-like receptor 7 (TLR7) agonist is routinely used for topical administration in basal cell carcinoma and stage zero melanoma. Similarly, the TLR agonist Bacillus Calmette-Guérin is used for the local treatment of bladder cancer and clinical trials showed treatment efficacy of intratumoral injections with TLR9 agonists. However, when administered systemically, endosomal TLR agonists cause adverse responses due to broad immune activation. Hence, strategies for targeted delivery of TLR agonists to the tumor tissue are needed to enable the widespread use of endosomal TLR agonists in the context of tumor immunotherapy. One strategy for targeted delivery of TLR agonist is their conjugation to tumor antigen-specific therapeutic antibodies. Such antibody-TLR agonist conjugates act synergistically by inducing local TLR-mediated innate immune activation which complements the anti-tumor immune mechanisms induced by the therapeutic antibody. In this study, we explored different conjugation strategies for TLR9 agonists to immunoglobulin G (IgG). We evaluated biochemical conjugation of immunostimulatory CpG oligodesoxyribonucleotides (ODN) to the HER2-specific therapeutic antibody Trastuzumab with different cross-linkers comparing stochastic with site-specific conjugation. The physiochemical make-up and biological activities of the generated Trastuzumab-ODN conjugates were characterized in vitro and demonstrated that site-specific conjugation of CpG ODN is crucial for maintaining the antigen-binding capabilities of Trastuzumab. Furthermore, site-specific conjugate was effective in promoting anti-tumor immune responses in vivo in a pseudo-metastasis mouse model with engineered human HER2-transgenic tumor cells. In this in vivo model, co-delivery of Trastuzumab and CpG ODN in form of site-specific conjugates was superior to co-injection of unconjugated Trastuzumab, CpG ODN or stochastic conjugate in promoting T cell activation and expansion. Thereby, this study highlights that site-specific conjugation of CpG ODN to therapeutic antibodies targeting tumor markers is a feasible and more reliable approach for generation of conjugates which retain and combine the functional properties of the adjuvant and the antibody.

Factors Affecting the Cancer Immunotherapeutic Efficacy of T Cell Bispecific Antibodies and Strategies for Improvement

T-cell bispecific antibodies (T-BsAbs) are a new class of cancer immunotherapy drugs that can simultaneously bind to tumor-associated antigens on target cells and to the CD3 subunit of the T-cell receptor (TCR) on T cells. In the last decade, numerous T-BsAbs have been developed for the treatment of both hematological malignancies and solid tumors. Among them, blinatumomab has been successfully used to treat CD19 positive malignancies and has been approved by the FDA as standard care for acute lymphoblastic leukemia (ALL). However, in many clinical scenarios, the efficacy of T-BsAbs remains unsatisfactory. To further improve T-BsAb therapy, it will be crucial to better understand the factors affecting treatment efficacy and the nature of the T-BsAb-induced immune response. Herein, we first review the studies on the potential mechanisms by which T-BsAbs activate T-cells and how they elicit efficient target killing despite suboptimal costimulatory support. We focus on analyzing reports from clinical trials and preclinical studies, and summarize the factors that have been identified to impact the efficacy of T-BsAbs. Lastly, we review current and propose new approaches to improve the clinical efficacy of T-BsAbs.

Toll-like receptor (TLR) agonists as a driving force behind next-generation vaccine adjuvants and cancer therapeutics

Until recently, the development of new human adjuvants was held back by a poor understanding of their mechanisms of action. The field was revolutionized by the discovery of the toll-like receptors (TLRs), innate immune receptors that directly or indirectly are responsible for detecting pathogen-associated molecular patterns (PAMPs) and respond to them by activating innate and adaptive immune pathways. Hundreds of ligands targeting various TLRs have since been identified and characterized as vaccine adjuvants. This work has important implications not only for the development of vaccines against infectious diseases but also for immuno-therapies against cancer, allergy, Alzheimer's disease, drug addiction and other diseases. Each TLR has its own specific tissue localization and downstream gene signalling pathways, providing researchers the opportunity to precisely tailor adjuvants with specific immune effects. TLR agonists can be combined with other TLR or alternative adjuvants to create combination adjuvants with synergistic or modulatory effects. This review provides an introduction to the various classes of TLR adjuvants and their respective signalling pathways. It provides an overview of recent advancements in the TLR field in the past 2-3 years and discusses criteria for selecting specific TLR adjuvants based on considerations, such as disease mechanisms and correlates of protection, TLR immune biasing capabilities, route of administration, antigen compatibility, new vaccine technology platforms, and age- and species-specific effects.

Recent advances in cancer immunotherapy: Modulation of tumor microenvironment by Toll-like receptor ligands

Immunotherapy is considered a promising approach for cancer treatment. An important strategy for cancer immunotherapy is the use of cancer vaccines, which have been widely used for cancer treatment. Despite the great potential of cancer vaccines for cancer treatment, their therapeutic effects in clinical settings have been limited. The main reason behind the lack of significant therapeutic outcomes for cancer vaccines is believed to be the immunosuppressive tumor microenvironment (TME). The TME counteracts the therapeutic effects of immunotherapy and provides a favorable environment for tumor growth and progression. Therefore, overcoming the immunosuppressive TME can potentially augment the therapeutic effects of cancer immunotherapy in general and therapeutic cancer vaccines in particular. Among the strategies developed for overcoming immunosuppression in TME, the use of toll-like receptor (TLR) agonists has been suggested as a promising approach to reverse immunosuppression. In this paper, we will review the application of the four most widely studied TLR agonists including agonists of TLR3, 4, 7, and 9 in cancer immunotherapy.

Antibody-Incorporated Nanomedicines for Cancer Therapy

Antibody-based cancer therapy, one of the most significant therapeutic strategies, has achieved considerable success and progress over the past decades. Nevertheless, obstacles including limited tumor penetration, short circulation half-lives, undesired immunogenicity, and off-target side effects remain to be overcome for the antibody-based cancer treatment. Owing to the rapid development of nanotechnology, antibody-containing nanomedicines that have been extensively explored to overcome these obstacles have already demonstrated enhanced anticancer efficacy and clinical translation potential. This review intends to offer an overview of the advancements of antibody-incorporated nanoparticulate systems in cancer treatment, together with the nontrivial challenges faced by these next-generation nanomedicines. Diverse strategies of antibody immobilization, formats of antibodies, types of cancer-associated antigens, and anticancer mechanisms of antibody-containing nanomedicines are provided and discussed in this review, with an emphasis on the latest applications. The current limitations and future research directions on antibody-containing nanomedicines are also discussed from different perspectives to provide new insights into the construction of anticancer nanomedicines.

Targeted Transposition of Minicircle DNA Using Single-Chain Antibody Conjugated Cyclodextrin-Modified Poly (Propylene Imine) Nanocarriers

Among non-viral vectors, cationic polymers, such as poly(propylene imine) (PPI), play a prominent role in nucleic acid delivery. However, limitations of polycationic polymer-based DNA delivery systems are (i) insufficient target specificity, (ii) unsatisfactory transgene expression, and (iii) undesired transfer of therapeutic DNA into non-target cells. We developed single-chain antibody fragment (scFv)-directed hybrid polyplexes for targeted gene therapy of prostate stem cell antigen (PSCA)-positive tumors. Besides mono-biotinylated PSCA-specific single-chain antibodies (scFv(AM1-P-BAP)) conjugated to neutravidin, the hybrid polyplexes comprise β-cyclodextrin-modified PPI as well as biotin/maltose-modified PPI as carriers for minicircle DNAs encoding for Sleeping Beauty transposase and a transposon encoding the gene of interest. The PSCA-specific hybrid polyplexes efficiently delivered a GFP gene in PSCA-positive tumor cells, whereas control hybrid polyplexes showed low gene transfer efficiency. In an experimental gene therapy approach, targeted transposition of a codon-optimized p53 into p53-deficient HCT116^p53-/-/PSCA cells demonstrated decreased clonogenic survival when compared to mock controls. Noteworthily, p53 transposition in PTEN-deficient H4^PSCA glioma cells caused nearly complete loss of clonogenic survival. These results demonstrate the feasibility of combining tumor-targeting hybrid polyplexes and Sleeping Beauty gene transposition, which, due to the modular design, can be extended to other target genes and tumor entities.

Human Oral Epithelial Cells Suppress T Cell Function via Prostaglandin E2 Secretion

The oral mucosa is constantly exposed to a plethora of stimuli including food antigens, commensal microbiota and pathogens, requiring distinct immune responses. We previously reported that human oral epithelial cells (OECs) suppress immune responses to bacteria, using H413 and TR146 OEC lines and primary OECs in co-culture with dendritic cells (DCs) and T cells (OEC-conditioned cells). OECs reduced DCs expression of CD80/CD86 and IL-12/TNFα release and impaired T cell activation. Here, we further evaluated the immunosuppression by these OECs and investigated the underlying mechanisms. OEC-conditioned DCs did not induce CD4 T cell polarization towards Treg, judging by the absence of FoxP3 expression. OECs also repressed T-bet/IFNγ expression in CD4 and CD8 T cells activated by DCs or anti-CD3/CD28 antibodies. This inhibition depended on OEC:T cell ratio and IFNγ repression occurred at the transcriptional level. Time-lapse experiments showed that OECs inhibited early steps of T cell activation, consistent with OECs inability to suppress T cells stimulated with PMA/ionomycin. Blocking CD40/CD40L, CD58/CD2 and PD-L1/PD-1 interactions with specific antibodies did not disrupt T cell suppression by OECs. However, preventing prostaglandin E2 (PGE2) synthesis or blocking PGE2 binding to the cognate EP2/EP4 receptors, restored IFNγ and TNFα production in OEC-conditioned T cells. Finally, treating OECs with poly(I:C), which simulates viral infections, limited T cell suppression. Overall, these results point to an inherent ability of OECs to suppress immune responses, which can nonetheless be eluded when OECs are under direct assault.

Fast and long-lasting immune response to S-trimer COVID-19 vaccine adjuvanted by PIKA

In the face of the emerging variants of SARS-CoV-2, there is an urgent need to develop a vaccine that can induce fast, effective, long-lasting and broad protective immunity against SARS-CoV-2. Here, we developed a trimeric SARS-CoV-2 S protein vaccine candidate adjuvanted by PIKA, which can induce robust cellular and humoral immune responses. The results showed a high level of neutralizing antibodies induced by the vaccine was maintained for at least 400 days. In the study of non-human primates, PIKA adjuvanted S-trimer induced high SARS-CoV-2 neutralization titers and protected from virus replication in the lung following SARS-CoV-2 challenge. In addition, the long-term neutralizing antibody response induced by S-trimer vaccine adjuvanted by PIKA could neutralize multiple SARS-CoV-2 variants and there is no obvious different among the SARS- CoV-2 variants of interest or concern, including B.1.351, B.1.1.7, P.1, B.1.617.1 and B.1.617.2 variants. These data support the utility of S-trimer protein adjuvanted by PIKA as a potential vaccine candidate against SARS-CoV-2 infection.

Nanoparticle-Based Therapies for Turning Cold Tumors Hot: How to Treat an Immunosuppressive Tumor Microenvironment

Nanotechnologies are rapidly increasing their role in immuno-oncology in line with the need for novel therapeutic strategies to treat patients unresponsive to chemotherapies and immunotherapies. The tumor immune microenvironment (TIME) has emerged as critical for tumor classification and patient stratification to design better treatments. Notably, the tumor infiltration of effector T cells plays a crucial role in antitumor responses and has been identified as the primary parameter to define hot, immunosuppressed, excluded, and cold tumors. Organic and inorganic nanoparticles (NPs) have been applied as carriers of new targeted therapies to turn cold or altered (i.e., immunosuppressed or excluded) tumors into more therapeutically responsive hot tumors. This mini-review discusses the significant advances in NP-based approaches to turn immunologically cold tumors into hot ones.

PLGA-particle vaccine carrying TLR3/RIG-I ligand Riboxxim synergizes with immune checkpoint blockade for effective anti-cancer immunotherapy

With emerging supremacy, cancer immunotherapy has evolved as a promising therapeutic modality compared to conventional antitumor therapies. Cancer immunotherapy composed of biodegradable poly(lactic-co-glycolic acid) (PLGA) particles containing antigens and toll-like receptor ligands induces vigorous antitumor immune responses in vivo. Here, we demonstrate the supreme adjuvant effect of the recently developed and pharmaceutically defined double-stranded (ds)RNA adjuvant Riboxxim especially when incorporated into PLGA particles. Encapsulation of Riboxxim together with antigens potently activates murine and human dendritic cells, and elevated tumor-specific CD8+ T cell responses are superior to those obtained using classical dsRNA analogues. This PLGA particle vaccine affords primary tumor growth retardation, prevention of metastases, and prolonged survival in preclinical tumor models. Its advantageous therapeutic potency was further enhanced by immune checkpoint blockade that resulted in reinvigoration of cytotoxic T lymphocyte responses and tumor ablation. Thus, combining immune checkpoint blockade with immunotherapy based on Riboxxim-bearing PLGA particles strongly increases its efficacy.

Targeted RNAi of BIRC5/Survivin Using Antibody-Conjugated Poly(Propylene Imine)-Based Polyplexes Inhibits Growth of PSCA-Positive Tumors

Delivery of siRNAs for the treatment of tumors critically depends on the development of efficient nucleic acid carrier systems. The complexation of dendritic polymers (dendrimers) results in nanoparticles, called dendriplexes, that protect siRNA from degradation and mediate non-specific cellular uptake of siRNA. However, large siRNA doses are required for in vivo use due to accumulation of the nanoparticles in sinks such as the lung, liver, and spleen. This suggests the exploration of targeted nanoparticles for enhancing tumor cell specificity and achieving higher siRNA levels in tumors. In this work, we report on the targeted delivery of a therapeutic siRNA specific for BIRC5/Survivin in vitro and in vivo to tumor cells expressing the surface marker prostate stem cell antigen (PSCA). For this, polyplexes consisting of single-chain antibody fragments specific for PSCA conjugated to siRNA/maltose-modified poly(propylene imine) dendriplexes were used. These polyplexes were endocytosed by PSCA-positive 293T^PSCA/ffLuc and PC3^PSCA cells and caused knockdown of reporter gene firefly luciferase and Survivin expression, respectively. In a therapeutic study in PC3^PSCA xenograft-bearing mice, significant anti-tumor effects were observed upon systemic administration of the targeted polyplexes. This indicates superior anti-tumor efficacy when employing targeted delivery of Survivin-specific siRNA, based on the additive effects of siRNA-mediated Survivin knockdown in combination with scFv-mediated PSCA inhibition.

In Situ Vaccination as a Strategy to Modulate the Immune Microenvironment of Hepatocellular Carcinoma

Hepatocellular Carcinoma (HCC) is a highly prevalent malignancy that develops in patients with chronic liver diseases and dysregulated systemic and hepatic immunity. The tumor microenvironment (TME) contains tumor-associated macrophages (TAM), cancer-associated fibroblasts (CAF), regulatory T cells (Treg) and myeloid-derived suppressor cells (MDSC) and is central to mediating immune evasion and resistance to therapy. The interplay between these cells types often leads to insufficient antigen presentation, preventing effective anti-tumor immune responses. In situ vaccines harness the tumor as the source of antigens and implement sequential immunomodulation to generate systemic and lasting antitumor immunity. Thus, in situ vaccines hold the promise to induce a switch from an immunosuppressive environment where HCC cells evade antigen presentation and suppress T cell responses towards an immunostimulatory environment enriched for activated cytotoxic cells. Pivotal steps of in situ vaccination include the induction of immunogenic cell death of tumor cells, a recruitment of antigen-presenting cells with a focus on dendritic cells, their loading and maturation and a subsequent cross-priming of CD8+ T cells to ensure cytotoxic activity against tumor cells. Several in situ vaccine approaches have been suggested, with vaccine regimens including oncolytic viruses, Flt3L, GM-CSF and TLR agonists. Moreover, combinations with checkpoint inhibitors have been suggested in HCC and other tumor entities. This review will give an overview of various in situ vaccine strategies for HCC, highlighting the potentials and pitfalls of in situ vaccines to treat liver cancer.

Tumor-Targeted Nanomedicine for Immunotherapy

Therapeutic manipulation of the immune system against cancer has revolutionized the treatment of several advanced-stage tumors. While many have benefited from these treatments, the proportion of patients responding to immunotherapies is still low. Nanomedicines have promise to revolutionize tumor treatments through spatiotemporal control of drug activity. Such control of drug function could allow enhanced therapeutic actions of immunotherapies and reduced side effects. However, only a handful of formulations have been able to reach human clinical studies so far, and even fewer systems are being used in the clinic. Among translatable formulations, self-assembled nanomedicines have shown unique and versatile features for dealing with the heterogeneity and malignancy of tumors in the clinic. Such nanomedicines can be designed to promote antitumor immune responses through a series of immunopotentiating functions after being directly injected into tumors, or achieving selective tumor accumulation upon intravenous administration. Thus, tumor-targeted nanomedicines can enhance antitumor immunity by several mechanisms, such as inducing immunogenic damage to cancer cells, altering the tumor immune microenvironment by delivering immunomodulators, or eliminating or reprogramming immunosuppressive cells, enhancing the exposure of tumor-associated antigens to antigen presenting cells, stimulating innate immunity mechanisms, and facilitating the infiltration of antitumor immune cells and their interaction with cancer cells. Moreover, nanomedicines can be engineered to sense intratumoral stimuli for activating specific immune responses or installed with ligands for increasing drug levels in tumors, granting subcellular delivery, and triggering immune signals and proliferation of immune cells. Thus, the ability of nanomedicines to exert immunomodulatory functions selectively in tumor and tumor-associated tissues, such as draining lymph nodes, increases the efficiency of the treatments, while avoiding systemic immunosuppressive toxicities and the exacerbation of adverse immune responses. Moreover, the compartmentalized structure of self-assembled nanomedicines offers the possibility to coload a variety of drugs for controlled pharmacokinetics, enhanced tumor delivery, and synergistic therapeutic output. Also, by integrating imaging functionalities into nanomedicines, it is possible to develop theranostic platforms reporting the immune settings of tumors as well as the effects of nanomedicines on the tumor immune microenvironment. Herein, we critically reviewed significant strategies for developing nanomedicines capable of potentiating antitumor immune responses by surmounting biological barriers and modulating antitumor immune signals. Moreover, the potential of these nanomedicines for developing innovative anticancer treatments by targeting particular cells is discussed. Finally, we present our perspectives on the awaiting challenges and future directions of nanomedicines in the age of immunotherapy.

Toll-Like Receptor 3 in Solid Cancer and Therapy Resistance

Simple Summary

Toll-like receptor 3 (TLR3) is a member of the TLR family, which has been extensively studied for the antiviral function and, therefore, its role in the innate and adaptive immune responses. It is highly expressed in the endosomes of antigen-presenting immune cells and epithelial cells. Several studies have demonstrated TLR3 expression in multiple neoplasia types including breast, prostate, and ovarian cancer. In this perspective, we focus on the mechanisms through which TLR3 can either lead to tumor regression or promote carcinogenesis as well as on the potential of TLR-based therapies in resistant cancer.

Abstract

Toll-like receptor 3 (TLR3) is a member of the TLR family, which has been extensively studied for its antiviral function. It is highly expressed in the endosomes of antigen-presenting immune cells and epithelial cells. TLR3 binds specifically double-strand RNAs (dsRNAs), leading to the activation of mainly two downstream pathways: the phosphorylation of IRF3, with subsequent production of type I interferon, and the activation of NF-κB, which drives the production of inflammatory cytokines and chemokines. Several studies have demonstrated TLR3 expression in multiple neoplasia types including breast, prostate, and lung cancer. Most studies were focused on the beneficial role of TLR3 activation in tumor cells, which leads to the production of cytotoxic cytokines and interferons and promotes caspase-dependent apoptosis. Indeed, ligands of this receptor were proposed for the treatment of cancer, also in combination with conventional chemotherapy. In contrast to these findings, recent evidence showed a link between TLR3 and tumor progression, metastasis, and therapy resistance. In the present review, we summarize the current knowledge of the mechanisms through which TLR3 can either lead to tumor regression or promote carcinogenesis as well as the potential of TLR-based therapies in resistant cancer.

Nanomedicine-based drug delivery towards tumor biological and immunological microenvironment

The complex tumor microenvironment is a most important factor in cancer development. The biological microenvironment is composed of a variety of barriers including the extracellular matrix and associated cells such as endothelia cells, pericytes, and cancer-associated fibroblasts. Different strategies can be utilized to enhance nanoparticle-based drug delivery and distribution into tumor tissues addressing the extracellular matrix or cellular components. In addition to the biological microenvironment, the immunological conditions around the tumor tissue can be very complicated and cancer cells have various ways of evading immune surveillance. Nanoparticle drug delivery systems can enhance cancer immunotherapy by tuning the immunological response and memory of various immune cells such as T cells, B cells, macrophages, and dendritic cells. In this review, the main components in the tumor biological and immunological environment are discussed. The focus is on recent advances in nanoparticle-based drug delivery systems towards targets within the tumor microenvironment to improve cancer chemotherapy and immunotherapy.

Myeloid Differentiation Primary Response 88-Cyclin D1 Signaling in Breast Cancer Cells Regulates Toll-Like Receptor 3-Mediated Cell Proliferation

Toll-like receptor 3 (TLR3)-mediated apoptotic changes in cancer cells are well-documented, and hence, several synthetic ligands of TLR3 are being used for adjuvant therapy, but there are reports showing a contradictory effect of TLR3 signaling, which include our previous report that had shown cell proliferation following surface localization of TLR 3. However, the underlying mechanism of cell surface localization of TLR3 and subsequent cell proliferation lacks clarity. This study addresses the TLR3 ligand-mediated signaling cascade that regulates a proliferative effect in breast cancer cells (MDA-MB-231 and T47D) challenged with TLR3 ligand in the presence of myeloid differentiation primary response 88 (MyD88) inhibitor. Evidences were obtained using immunoblotting, coimmunoprecipitation, confocal microscopy, immunocytochemistry, ELISA, and flow cytometry. Results had revealed that TLR3 ligand treatment significantly enhanced breast cancer cell proliferation marked by an upregulated expression of cyclinD1, but the same was suppressed by the addition of MyD88 inhibitor. Also, expression of interleukin 1 receptor-associated kinase 1 (IRAK1)-TNF receptor-associated factor 6 (TRAF6)-transforming growth factor beta-activated kinase 1 (TAK1) was altered in the given TLR3-signaling pathway. Inhibition of MyD88 disrupted the downstream adaptor complex and mediated signaling through the TLR3-MyD88-NF-κB (p65)-IL-6-cyclin D1 pathway. TLR3-mediated alternative signaling of the TLR3-MyD88-IRAK1-TRAF6-TAK1-TAB1-NF-κB axis leads to upregulation of IL6 and cyclin D1. This response is hypothesized to be via the MyD88 gateway that culminates in the proliferation of breast cancer cells. Overall, this study provides first comprehensive evidence on the involvement of canonical signaling of TLR3 using MyD88-cyclin D1-mediated breast cancer cell proliferation. The findings elucidated herein will provide valuable insights into understanding the TLR3-mediated adjuvant therapy in cancer.

Chemical Strategies to Boost Cancer Vaccines

Personalized cancer vaccines (PCVs) are reinvigorating vaccine strategies in cancer immunotherapy. In contrast to adoptive T-cell therapy and checkpoint blockade, the PCV strategy modulates the innate and adaptive immune systems with broader activation to redeploy antitumor immunity with individualized tumor-specific antigens (neoantigens). Following a sequential scheme of tumor biopsy, mutation analysis, and epitope prediction, the administration of neoantigens with synthetic long peptide (SLP) or mRNA formulations dramatically improves the population and activity of antigen-specific CD4+ and CD8+ T cells. Despite the promising prospect of PCVs, there is still great potential for optimizing prevaccination procedures and vaccine potency. In particular, the arduous development of tumor-associated antigen (TAA)-based vaccines provides valuable experience and rational principles for augmenting vaccine potency which is expected to advance PCV through the design of adjuvants, delivery systems, and immunosuppressive tumor microenvironment (TME) reversion since current personalized vaccination simply admixes antigens with adjuvants. Considering the broader application of TAA-based vaccine design, these two strategies complement each other and can lead to both personalized and universal therapeutic methods. Chemical strategies provide vast opportunities for (1) exploring novel adjuvants, including synthetic molecules and materials with optimizable activity, (2) constructing efficient and precise delivery systems to avoid systemic diffusion, improve biosafety, target secondary lymphoid organs, and enhance antigen presentation, and (3) combining bioengineering methods to innovate improvements in conventional vaccination, "smartly" re-educate the TME, and modulate antitumor immunity. As chemical strategies have proven versatility, reliability, and universality in the design of T cell- and B cell-based antitumor vaccines, the union of such numerous chemical methods in vaccine construction is expected to provide new vigor and vitality in cancer treatment.

Arginine-Based Poly(I:C)-Loaded Nanocomplexes for the Polarization of Macrophages Toward M1-Antitumoral Effectors

Background: Tumor-associated macrophages (TAMs), with M2-like immunosuppressive profiles, are key players in the development and dissemination of tumors. Hence, the induction of M1 pro-inflammatory and anti-tumoral states is critical to fight against cancer cells. The activation of the endosomal toll-like receptor 3 by its agonist poly(I:C) has shown to efficiently drive this polarization process. Unfortunately, poly(I:C) presents significant systemic toxicity, and its clinical use is restricted to a local administration. Therefore, the objective of this work has been to facilitate the delivery of poly(I:C) to macrophages through the use of nanotechnology, that will ultimately drive their phenotype toward pro-inflammatory states.

Methods: Poly(I:C) was complexed to arginine-rich polypeptides, and then further enveloped with an anionic polymeric layer either by film hydration or incubation. Physicochemical characterization of the nanocomplexes was conducted by dynamic light scattering and transmission electron microscopy, and poly(I:C) association efficiency by gel electrophoresis. Primary human-derived macrophages were used as relevant in vitro cell model. Alamar Blue assay, ELISA, PCR and flow cytometry were used to determine macrophage viability, polarization, chemokine secretion and uptake of nanocomplexes. The cytotoxic activity of pre-treated macrophages against PANC-1 cancer cells was assessed by flow cytometry.

Results: The final poly(I:C) nanocomplexes presented sizes lower than 200 nm, with surface charges ranging from +40 to −20 mV, depending on the envelopment. They all presented high poly(I:C) loading values, from 12 to 50%, and great stability in cell culture media. In vitro, poly(I:C) nanocomplexes were highly taken up by macrophages, in comparison to the free molecule. Macrophage treatment with these nanocomplexes did not reduce their viability and efficiently stimulated the secretion of the T-cell recruiter chemokines CXCL10 and CCL5, of great importance for an effective anti-tumor immune response. Finally, poly(I:C) nanocomplexes significantly increased the ability of treated macrophages to directly kill cancer cells.

Conclusion: Overall, these enveloped poly(I:C) nanocomplexes might represent a therapeutic option to fight cancer through the induction of cytotoxic M1-polarized macrophages.

RIPK1-mediated immunogenic cell death promotes anti-tumour immunity against soft-tissue sarcoma

Drugs that mobilise the immune system against cancer are dramatically improving care for many people. Dying cancer cells play an active role in inducing anti-tumour immunity but not every form of death can elicit an immune response. Moreover, resistance to apoptosis is a major problem in cancer treatment and disease control. While the term "immunogenic cell death" is not fully defined, activation of receptor-interacting serine/threonine-protein kinase 1 (RIPK1) can induce a type of death that mobilises the immune system against cancer. However, no clinical treatment protocols have yet been established that would harness the immunogenic potential of RIPK1. Here, we report the first pre-clinical application of an in vivo treatment protocol for soft-tissue sarcoma that directly engages RIPK1-mediated immunogenic cell death. We find that RIPK1-mediated cell death significantly improves local disease control, increases activation of CD8+ T cells as well as NK cells, and enhances the survival benefit of immune checkpoint blockade. Our findings warrant a clinical trial to assess the survival benefit of RIPK1-induced cell death in patients with advanced disease at limb extremities.

Trial watch: TLR3 agonists in cancer therapy

Toll-like receptor 3 (TLR3) is a pattern recognition receptor that senses exogenous (viral) as well as endogenous (mammalian) double-stranded RNA in endosomes. On activation, TLR3 initiates a signal transduction pathway that culminates with the secretion of pro-inflammatory cytokines including type I interferon (IFN). The latter is essential not only for innate immune responses to infection but also for the initiation of antigen-specific immunity against viruses and malignant cells. These aspects of TLR3 biology have supported the development of various agonists for use as stand-alone agents or combined with other therapeutic modalities in cancer patients. Here, we review recent preclinical and clinical advances in the development of TLR3 agonists for oncological disorders.

Abbreviations

cDC, conventional dendritic cell; CMT, cytokine modulating treatment; CRC, colorectal carcinoma; CTL, cytotoxic T lymphocyte; DC, dendritic cell; dsRNA, double-stranded RNA; FLT3LG, fms-related receptor tyrosine kinase 3 ligand; HNSCC, head and neck squamous cell carcinoma; IFN, interferon; IL, interleukin; ISV, in situ vaccine; MUC1, mucin 1, cell surface associated; PD-1, programmed cell death 1; PD-L1, programmed death-ligand 1; polyA:U, polyadenylic:polyuridylic acid; polyI:C, polyriboinosinic:polyribocytidylic acid; TLR, Toll-like receptor.

A Novel Model of Cancer Drug Resistance: Oncosomal Release of Cytotoxic and Antibody-Based Drugs

Extracellular vesicles (EVs), such as exosomes or oncosomes, often carry oncogenic molecules derived from tumor cells. In addition, accumulating evidence indicates that tumor cells can eject anti-cancer drugs such as chemotherapeutics and targeted drugs within EVs, a novel mechanism of drug resistance. The EV-releasing drug resistance phenotype is often coupled with cellular dedifferentiation and transformation in cells undergoing epithelial-mesenchymal transition (EMT), and the adoption of a cancer stem cell phenotype. The release of EVs is also involved in immunosuppression. Herein, we address different aspects by which EVs modulate the tumor microenvironment to become resistant to anticancer and antibody-based drugs, as well as the concept of the resistance-associated secretory phenotype (RASP).