Acidic pH-responsive polymer nanoparticles as a TLR7/8 agonist delivery platform for cancer immunotherapy

Percutaneous Intratumoral Immunoadjuvant Gel Increases the Abscopal Effect of Cryoablation for Checkpoint Inhibitor Resistant Cancer

Percutaneous cryoablation is a common clinical therapy for metastatic and primary cancer. There are rare clinical reports of cryoablation inducing regression of distant metastases, known as the "abscopal" effect. Intratumoral immunoadjuvants may be able to augment the abscopal rate of cryoablation, but existing intratumoral therapies suffer from the need for frequent injections and inability to confirm target delivery, leading to poor clinical trial outcomes. To address these shortcomings, an injectable thermoresponsive gel-based controlled release formulation is developed for the FDA-approved Toll-like-receptor 7 (TLR7) agonist imiquimod ("Imigel") that forms a tumor-resident depot upon injection and contains a contrast agent for visualization under computed tomography (CT). The poly-lactic-co-glycolic acid-polyethylene glycol-poly-lactic-co-glycolic acid (PLGA-PEG-PLGA)-based amphiphilic copolymer gel's underlying micellar nature enables high drug concentration and a logarithmic release profile that is additive with the neo-antigen release from cryoablation, requiring only a single injection. Rheological testing demonstrated the thermoresponsive increase in viscosity at body temperature and radio-opacity via microCT. Its ability to significantly augment the abscopal rate of cryoablation is demonstrated in otherwise immunotherapy resistant metastatic tumors in two aggressive colorectal and breast cancer dual tumor models with an all or nothing response, responders generally demonstrating complete regression of bilateral tumors in 90-day survival studies.

Toll-Like Receptors 7/8: A Paradigm for the Manipulation of Immunologic Reactions for Immunotherapy

The innate immune system recognizes conserved features of viral and microbial pathogens through pattern recognition receptors (PRRs). Toll-like receptors (TLRs) are one type of PRR used by the innate immune system to mediate the secretion of proinflammatory cytokines and promote innate and adaptive immune responses. TLR family members TLR7 and TLR8 (referred to as TLR7/8 from herein) are endosomal transmembrane receptors that recognize purine-rich single-stranded RNA (ssRNA) and bacterial DNA, eliciting an immunologic reaction to pathogens. TLR7/8 were discovered to mediate the secretion of proinflammatory cytokines by activating immune cells. In addition, accumulating evidence has indicated that TLR7/8 may be closely related to numerous immune-mediated disorders, specifically several types of cancer, autoimmune disease, and viral disease. TLR7/8 agonists and antagonists, which are used as drugs or adjuvants, have been identified in preclinical studies and clinical trials as promising immune stimulators for the immunotherapy of these immune-mediated disorders. These results provided reasoning to further explore immunotherapy for the treatment of immune-mediated disorders. Nevertheless, numerous needs remain unmet, and the therapeutic effects of TLR7/8 agonists and antagonists are poor and exert strong immune-related toxicities. The present review aimed to provide an overview of the TLR family members, particularly TLR7/8, and address the underlying molecular mechanisms and clinical implications of TLR7/8 in immune-mediated disorders. The aim of the work is to discuss the underlying molecular mechanisms and clinical implications of TLR7/8 in immune-mediated disorders.

Cationic lipid potentiated the adjuvanticity of polysaccharide derivative-modified liposome vaccines

Antigen carriers that can selectively deliver antigens to antigen presenting cells and which can simultaneously activate these cells (adjuvant property) are necessary for efficient cancer immunotherapy or vaccination. Delivery of a model antigen into dendritic cell cytosol has been achieved by pH-responsive polymer-modified liposomes via destabilization of endosomal membranes responding to acidic pH, which impelled antigen-specific cellular immunity. Furthermore, β-glucan-based pH-responsive polysaccharides have shown not only cytosolic antigen delivery performance but also adjuvant property, which further heightened cellular immune responses. Because pH-responsive polysaccharides have anionic carboxy groups, cationic lipid was introduced to liposomes in this study to improve the modification efficiency of pH-responsive polysaccharides and to improve their adjuvanticity and immunity-inducing functions. Introduction of cationic lipids increased the amounts of polysaccharide derivatives on the liposome and increased the cellular association of the liposomes to dendritic cells. Liposomes containing β-glucan-based pH-responsive polysaccharides and cationic lipids increased cytokine production from dendritic cells much more than other polysaccharide derivatives did. Furthermore, through improvement of intra-tumoral immunosuppression and induction of antigen-specific cellular immunity, administering these liposomes impelled tumor suppression even with a small antigen dose. These results suggest that introducing cationic lipids and using pH-responsive polysaccharides having intrinsically adjuvant function are effective for producing liposomal nanovaccines showing strong immunity-inducing function.

Advancements in pH-responsive nanocarriers: enhancing drug delivery for tumor therapy

INTRODUCTION

Tumors pose a significant global economic and health burden, with conventional cancer treatments lacking tumor specificity, leading to limited efficiency and undesirable side effects. Targeted tumor therapy is imminent. Tumor cells produce lactate and hydrogen ions (H+) by Warburg effect, forming an acidic tumor microenvironment (TME), which can be employed to design targeted tumor therapy. Recently, progress in nanotechnology has led to the development of pH-responsive nanocarriers, which have gathered significant attention. Under acidic tumor conditions, they exhibit targeted accumulation within tumor sites and controlled release profiles of therapeutic reagents, enabling precise tumor therapy.

AREAS COVERED

This review comprehensively summarize the principles underlying pH-responsive features, discussing various types of pH-responsive nanocarriers, their advantages, and limitations. Innovative therapeutic drugs are also examined, followed by an exploration of recent advancements in applying various pH-responsive nanocarriers as delivery systems for enhanced tumor therapy.

EXPERT OPINIONS

pH-responsive nanocarriers have garnered significant attention for their capability to achieve targeted accumulation of therapeutic agents at tumor sites and controlled drug delivery profiles, ultimately increasing the efficiency of tumor eradication. It is anticipated that the employment of pH-responsive nanocarriers will elevate the effectiveness and safety of tumor therapy, contributing to improved overall outcomes.

The Latest Approach of Immunotherapy with Endosomal TLR Agonists Improving NK Cell Function: An Overview

Toll-like receptors (TLRs) are the most well-defined pattern recognition receptors (PRR) of several cell types recognizing pathogens and triggering innate immunity. TLRs are also expressed on tumor cells and tumor microenvironment (TME) cells, including natural killer (NK) cells. Cell surface TLRs primarily recognize extracellular ligands from bacteria and fungi, while endosomal TLRs recognize microbial DNA or RNA. TLR engagement activates intracellular pathways leading to the activation of transcription factors regulating gene expression of several inflammatory molecules. Endosomal TLR agonists may be considered as new immunotherapeutic adjuvants for dendritic cell (DC) vaccines able to improve anti-tumor immunity and cancer patient outcomes. The literature suggests that endosomal TLR agonists modify TME on murine models and human cancer (clinical trials), providing evidence that locally infused endosomal TLR agonists may delay tumor growth and induce tumor regression. Recently, our group demonstrated that CD56^bright NK cell subset is selectively responsive to TLR8 engagement. Thus, TLR8 agonists (loaded or not to nanoparticles or other carriers) can be considered a novel strategy able to promote anti-tumor immunity. TLR8 agonists can be used to activate and expand in vitro circulating or intra-tumoral NK cells to be adoptively transferred into patients.

Combination of STING and TLR 7/8 Agonists as Vaccine Adjuvants for Cancer Immunotherapy

Immunostimulatory adjuvants that potently activate antigen-presenting cells and (in turn) prime cytotoxic T cells are a key component of anticancer vaccines. In this study, we investigated a multi-adjuvant approach combining a TLR 7/8 agonist (522) and a STING agonist (DMXAA) to promote enhanced antigen cross-presentation, stimulate specific antitumor T-cell responses, and provide improved anticancer efficacy. In vitro experiments using bone marrow-derived dendritic cells (BMDCs) confirmed enhanced activation with the 522-DMXAA combination based on both co-stimulatory molecule expression and pro-inflammatory cytokine secretion. The immunization of mice with vaccines comprising both 522 and DMXAA resulted in greater antitumor efficacy in B16F10 melanoma and MB49 bladder tumor models relative to mono-agonist vaccines. Flow cytometry-based analysis of immune cells from immunized mice revealed the significant activation of antigen-presenting cells, increased numbers of activated and Ag-specific CD8+ T cells in the spleen and lymph nodes, modest NK cell activation, and an overall reduction in CD206⁺ macrophages. These results were supported by an increase in the levels of IFN-γ and a reduction in IL-10 levels in the sera. Taken together, these findings demonstrate the potential of the TLR7/8 and STING agonist combination as vaccine adjuvants to activate both innate and adaptive immune responses.

Toll-like receptor-targeted anti-tumor therapies: Advances and challenges

Toll-like receptors (TLRs) are pattern recognition receptors, originally discovered to stimulate innate immune reactions against microbial infection. TLRs also play essential roles in bridging the innate and adaptive immune system, playing multiple roles in inflammation, autoimmune diseases, and cancer. Thanks to the immune stimulatory potential of TLRs, TLR-targeted strategies in cancer treatment have proved to be able to regulate the tumor microenvironment towards tumoricidal phenotypes. Quantities of pre-clinical studies and clinical trials using TLR-targeted strategies in treating cancer have been initiated, with some drugs already becoming part of standard care. Here we review the structure, ligand, signaling pathways, and expression of TLRs; we then provide an overview of the pre-clinical studies and an updated clinical trial watch targeting each TLR in cancer treatment; and finally, we discuss the challenges and prospects of TLR-targeted therapy.

Nanoparticle Enhancement of Natural Killer (NK) Cell-Based Immunotherapy

Simple Summary

Natural killer cells are a part of the native immune response to cancer. NK cell-based immunotherapies are an emerging strategy to kill tumor cells. This paper reviews the role of NK cells, their mechanism of action for killing tumor cells, and the receptors which could serve as potential targets for signaling. In this review, the role of nanoparticles in NK cell activation and increased cytotoxicity of NK cells against cancer are highlighted.

Abstract

Natural killer (NK) cells are one of the first lines of defense against infections and malignancies. NK cell-based immunotherapies are emerging as an alternative to T cell-based immunotherapies. Preclinical and clinical studies of NK cell-based immunotherapies have given promising results in the past few decades for hematologic malignancies. Despite these achievements, NK cell-based immunotherapies have limitations, such as limited performance/low therapeutic efficiency in solid tumors, the short lifespan of NK cells, limited specificity of adoptive transfer and genetic modification, NK cell rejection by the patient’s immune system, insignificant infiltration of NK cells into the tumor microenvironment (TME), and the expensive nature of the treatment. Nanotechnology could potentially assist with the activation, proliferation, near-real time imaging, and enhancement of NK cell cytotoxic activity by guiding their function, analyzing their performance in near-real time, and improving immunotherapeutic efficiency. This paper reviews the role of NK cells, their mechanism of action in killing tumor cells, and the receptors which could serve as potential targets for signaling. Specifically, we have reviewed five different areas of nanotechnology that could enhance immunotherapy efficiency: nanoparticle-assisted immunomodulation to enhance NK cell activity, nanoparticles enhancing homing of NK cells, nanoparticle delivery of RNAi to enhance NK cell activity, genetic modulation of NK cells based on nanoparticles, and nanoparticle activation of NKG2D, which is the master regulator of all NK cell responses.

Poly lactic-co-glycolic acid-based nanoparticles as delivery systems for enhanced cancer immunotherapy

Cancer has emerged as one of the most severe diseases in modern times, various therapies have advanced remarkably in recent decades. Unlike the direct therapeutic targeting tumor cells, immunotherapy is a promising strategy that stimulate the immune system. In cancer immunotherapy, polymeric-based nanoparticles can serve as deliver systems for antigens and immunostimulatory molecules, and they have attracted increasing attention and revolutionized cancer therapy. Poly (lactic-co-glycolic acid) (PLGA) is the most frequently used clinically approved biodegradable polymer and has a broad scope of modification of its inherent properties. Recent advances in PLGA based drug delivery systems in cancer immunotherapy have been described in this mini review, with special emphasis on cancer vaccines and tumor microenvironment modulation.

The Role of Toll-like Receptor Agonists and Their Nanomedicines for Tumor Immunotherapy

Toll-like receptors (TLRs) are a class of pattern recognition receptors that play a critical role in innate and adaptive immunity. Toll-like receptor agonists (TLRa) as vaccine adjuvant candidates have become one of the recent research hotspots in the cancer immunomodulatory field. Nevertheless, numerous current systemic deliveries of TLRa are inappropriate for clinical adoption due to their low efficiency and systemic adverse reactions. TLRa-loaded nanoparticles are capable of ameliorating the risk of immune-related toxicity and of strengthening tumor suppression and eradication. Herein, we first briefly depict the patterns of TLRa, followed by the mechanism of agonists at those targets. Second, we summarize the emerging applications of TLRa-loaded nanomedicines as state-of-the-art strategies to advance cancer immunotherapy. Additionally, we outline perspectives related to the development of nanomedicine-based TLRa combined with other therapeutic modalities for malignancies immunotherapy.

Drug delivery for metabolism targeted cancer immunotherapy

Drug delivery vehicles have made a great impact on cancer immunotherapies in clinics and pre-clinical research. Notably, the science of delivery of cancer vaccines and immunotherapeutics, modulating immune cell functions has inspired development of several successful companies and clinical products. Interestingly, these drug delivery modalities not only modulate the function of immune cells (often quantified at the mRNA and protein levels), but also modulate the metabolism of these cells. Specifically, cancer immunotherapy often leads to activation of different immune cells such as dendritic cells, macrophages and T cells, which is driven by energy metabolism of these cells. Recently, there has been a great excitement about interventions that can directly modulate the energy metabolism of these immune cells and thus affect their function and in turn lead to a robust cancer immune response. Here we review few strategies that have been tested in clinic and pre-clinical research for generating effective metabolism-associated cancer therapies and immunotherapies.

pH-Responsive Polymer Nanomaterials for Tumor Therapy

The complexity of the tumor microenvironment presents significant challenges to cancer therapy, while providing opportunities for targeted drug delivery. Using characteristic signals of the tumor microenvironment, various stimuli-responsive drug delivery systems can be constructed for targeted drug delivery to tumor sites. Among these, the pH is frequently utilized, owing to the pH of the tumor microenvironment being lower than that of blood and healthy tissues. pH-responsive polymer carriers can improve the efficiency of drug delivery in vivo, allow targeted drug delivery, and reduce adverse drug reactions, enabling multifunctional and personalized treatment. pH-responsive polymers have gained increasing interest due to their advantageous properties and potential for applicability in tumor therapy. In this review, recent advances in, and common applications of, pH-responsive polymer nanomaterials for drug delivery in cancer therapy are summarized, with a focus on the different types of pH-responsive polymers. Moreover, the challenges and future applications in this field are prospected.

Stimuli-Responsive Nanoparticles for Controlled Drug Delivery in Synergistic Cancer Immunotherapy

Cancer immunotherapy has achieved promising clinical progress over the recent years for its potential to treat metastatic tumors and inhibit their recurrences effectively. However, low patient response rates and dose-limiting toxicity remain as major dilemmas for immunotherapy. Stimuli-responsive nanoparticles (srNPs) combined with immunotherapy offer the possibility to amplify anti-tumor immune responses, where the weak acidity, high concentration of glutathione, overexpressions of enzymes, and reactive oxygen species, and external stimuli in tumors act as triggers for controlled drug release. This review highlights the design of srNPs based on tumor microenvironment and/or external stimuli to combine with different anti-tumor drugs, especially the immunoregulatory agents, which eventually realize synergistic immunotherapy of malignant primary or metastatic tumors and acquire a long-term immune memory to prevent tumor recurrence. The authors hope that this review can provide theoretical guidance for the construction and clinical transformation of smart srNPs for controlled drug delivery in synergistic cancer immunotherapy.

Targeting innate immune system by nanoparticles for cancer immunotherapy

Various cancer therapies have advanced remarkably over the past decade. Unlike the direct therapeutic targeting of tumor cells, cancer immunotherapy is a new strategy that boosts the host's immune system...

A bioinspired stimuli-responsive amino acid-based antibacterial drug delivery system in cancer therapy

Design of tyrosine based stimuli responsive antibacterial drug delivery system with potential application in cancer therapy.

Stimuli-Responsive Polymeric Nanomaterials for the Delivery of Immunotherapy Moieties: Antigens, Adjuvants and Agonists

Immunotherapy has been investigated for decades, and it has provided promising results in preclinical studies. The most important issue that hinders researchers from advancing to clinical studies is the delivery system for immunotherapy agents, such as antigens, adjuvants and agonists, and the activation of these agents at the tumour site. Polymers are among the most versatile materials for a variety of treatments and diagnostics, and some polymers are reactive to either endogenous or exogenous stimuli. Utilizing this advantage, researchers have been developing novel and effective polymeric nanomaterials that can deliver immunotherapeutic moieties. In this review, we summarized recent works on stimuli-responsive polymeric nanomaterials that deliver antigens, adjuvants and agonists to tumours for immunotherapy purposes.

Emerging strategies in developing multifunctional nanomaterials for cancer nanotheranostics

Cancer involves a collection of diseases with a common trait - dysregulation in cell proliferation. At present, traditional therapeutic strategies against cancer have limitations in tackling various tumors in clinical settings. These include chemotherapeutic resistance and the inability to overcome intrinsic physiological barriers to drug delivery. Nanomaterials have presented promising strategies for tumor treatment in recent years. Nanotheranostics combine therapeutic and bioimaging functionalities at the single nanoparticle level and have experienced tremendous growth over the past few years. This review highlights recent developments of advanced nanomaterials and nanotheranostics in three main directions: stimulus-responsive nanomaterials, nanocarriers targeting the tumor microenvironment, and emerging nanomaterials that integrate with phototherapies and immunotherapies. We also discuss the cytotoxicity and outlook of next-generation nanomaterials towards clinical implementation.

Engineering Therapeutic Strategies in Cancer Immunotherapy via Exogenous Delivery of Toll-like Receptor Agonists

As a currently spotlighted method for cancer treatment, cancer immunotherapy has made a lot of progress in recent years. Among tremendous cancer immunotherapy boosters available nowadays, Toll-like receptor (TLR) agonists were specifically selected, because of their effective activation of innate and adaptive immune cells, such as dendritic cells (DCs), T cells, and macrophages. TLR agonists can activate signaling pathways of DCs to express CD80 and CD86 molecules, and secrete various cytokines and chemokines. The maturation of DCs stimulates naïve T cells to differentiate into functional cells, and induces B cell activation. Although TLR agonists have anti-tumor ability by activating the immune system of the host, their drawbacks, which include poor efficiency and remarkably short retention time in the body, must be overcome. In this review, we classify and summarize the recently reported delivery strategies using (1) exogenous TLR agonists to maintain the biological and physiological signaling activities of cargo agonists, (2) usage of multiple TLR agonists for synergistic immune responses, and (3) co-delivery using the combination with other immunomodulators or stimulants. In contrast to naked TLR agonists, these exogenous TLR delivery strategies successfully facilitated immune responses and subsequently mediated anti-tumor efficacy.

Combined photothermal-immunotherapy via poly-tannic acid coated PLGA nanoparticles for cancer treatment

Photothermal therapy (PTT) is able to ablate tumors via hyperthermia, while immunotherapy could prevent tumor recurrence and metastasis by activating the host immune responses. Therefore, the combination of PTT and immunotherapy offers great advantages for the treatment of cancer. To achieve this goal, poly tannic acid (pTA) coated PLGA nanoparticles (PLGA-pTA NPs) were synthesized for combined photothermal-immunotherapy. pTA was a coordination complex formed by TA and Fe3+ and it could be easily coated on PLGA NPs within seconds with a coating rate of 5.89%. As a photothermal agent, PLGA-pTA revealed high photothermal conversion efficiency and excellent photo-stability upon 808 nm laser irradiation. It also exhibited strong photothermal cytotoxicity against 4T1 cells. Moreover, PLGA-pTA based PTT could effectively trigger DC maturation since it could induce the release of DAMPs. The result of animal experiments showed that PLGA-pTA plus laser irradiation raised the tumor temperature up to ca. 60 °C and effectively suppressed the growth of primary tumors. What's more, the progression of distant tumors as well as lung metastasis was also significantly inhibited due to the activation of anti-tumor responses by PLGA-pTA mediated PTT. When further combined with anti-PD-L1 antibody (a-PD-L1), the tumor growth and metastasis were almost completely inhibited. Our study provided a versatile platform to achieve combined photothermal-immunotherapy with enhanced therapeutic efficacy.

Employing Drug Delivery Strategies to Overcome Challenges Using TLR7/8 Agonists for Cancer Immunotherapy

Toll-like receptors (TLRs) are a potential target for cancer immunotherapy due to their role in the activation of the innate immune system. More specifically, TLR7 and TLR8, two structurally similar pattern recognition receptors that trigger interferon and cytokine responses, have proven to be therapeutically relevant targets for cancer in numerous preclinical and clinical studies. When triggered by an agonist, such as imiquimod or resiquimod, the TLR7/8 activation pathway induces cellular and humoral immune responses that can kill cancer cells with high specificity. Unfortunately, TLR7/8 agonists also present a number of issues that must be overcome prior to broad clinical implementation, such as poor drug solubility and systemic toxic effects. To overcome the key limitations of TLR7/8 agonists as a cancer therapy, biomaterial-based drug delivery systems have been developed. These delivery devices are highly diverse in their design and include systems that can be directly administered to the tumor, passively accumulated in relevant cancerous and lymph tissues, triggered by environmental stimuli, or actively targeted to specific physiological areas and cellular populations. In addition to improved delivery systems, recent studies have also demonstrated the potential benefits of TLR7/8 agonist co-delivery with other types of therapies, particularly checkpoint inhibitors, cancer vaccines, and chemotherapeutics, which can yield impressive anti-cancer effects. In this review, we discuss recent advances in the development of TLR7/8 agonist delivery systems and provide perspective on promising future directions.

Encapsulation of Andrographolide in poly(lactide-co-glycolide) Nanoparticles: Formulation Optimization and in vitro Efficacy Studies

Andrographolide is a potential chemopreventive and chemotherapeutic agent that suffers from poor aqueous solubility. Encapsulation in poly(lactide-co-glycolide) (PLGA) nanoparticles can overcome solubility issues and enable sustained release of the drug, resulting in improved therapeutic efficacy. In this study, andrographolide was encapsulated in PLGA nanoparticles via emulsion solvent evaporation technique. Effect of various formulation parameters including polymer composition, polymer molecular weight, polymer to drug ratio, surfactant concentration and the organic solvent used on nanoparticle properties were investigated. A selected formulation was used to determine the effect of encapsulation in nanoparticles on andrographolide's in vitro anticancer efficacy. Nanoparticles formulated using a polymer with 85:15 lactide to glycolide ratio and ethyl acetate as the organic solvent were found to be optimal based on average hydrodynamic particle size (135 ± 4 nm) and drug loading (2.6 ± 0.6%w/w). This formulation demonstrated sustained release of andrographolide over 48 h and demonstrated significantly greater in vitro anticancer efficacy compared to free drug in a metastatic breast cancer cell line. These results suggest that additional, more in-depth efficacy studies are warranted for the nanoparticle formulation of andrographolide.

Novel TLR 7/8 agonists for improving NK cell mediated antibody-dependent cellular cytotoxicity (ADCC)

There is a significant interest in designing therapeutic agents that can enhance ADCC and thereby improve clinical responses with approved antibodies. We recently reported the combination of an imidazoquinoline-based TLR7/8 agonist (522) with a monoclonal antibody improved ADCC in vitro and in vivo. In the present study, we tested several new small molecule TLR7/8 agonists that induce significantly higher cytokines compared to both the FDA-approved TLR7 agonist, imiquimod, and 522. We evaluated these agonists in combination with monoclonal antibody therapy, with the main goal of enhancing ADCC. Our studies show these TLR7/8 agonists induce robust pro-inflammatory cytokine secretion and activate NK cells. Specifically, we found the agonists 574 and 558 significantly enhanced NK cell-mediated ADCC in vitro as well as enhanced the anti-cancer efficacy of monoclonal antibodies in two different in vivo mouse models. Additionally, we found the agonists were able to stimulate CD8 T cells, likely indicative of an early adaptive immune response.

Activatable polymer nanoagonist for second near-infrared photothermal immunotherapy of cancer

Nanomedicine in combination with immunotherapy offers opportunities to treat cancer in a safe and effective manner; however, remote control of immune response with spatiotemporal precision remains challenging. We herein report a photothermally activatable polymeric pro-nanoagonist (APNA) that is specifically regulated by deep-tissue-penetrating second near-infrared (NIR-II) light for combinational photothermal immunotherapy. APNA is constructed from covalent conjugation of an immunostimulant onto a NIR-II semiconducting transducer through a labile thermo-responsive linker. Upon NIR-II photoirradiation, APNA mediates photothermal effect, which not only triggers tumor ablation and immunogenic cell death but also initiates the cleavage of thermolabile linker to liberate caged agonist for in-situ immune activation in deep solid tumor (8 mm). Such controlled immune regulation potentiates systemic antitumor immunity, leading to promoted cytotoxic T lymphocytes and helper T cell infiltration in distal tumor, lung and liver to inhibit cancer metastasis. Thereby, the present work illustrates a generic strategy to prepare pro-immunostimulants for spatiotemporal regulation of cancer nano-immunotherapy.

Precise control of immune response remains challenging for cancer immunotherapy. Here, the authors report on photothermally activatable semiconducting polymeric pro-agonist in response to second near-infrared window light for regulated photothermal immunotherapy.

Synergistic Combination Chemotherapy of Lung Cancer: Cisplatin and Doxorubicin Conjugated Prodrug Loaded, Glutathione and pH Sensitive Nanocarriers

Purpose

Prodrug technology-based combination drug therapy has been exploited as a promising treatment strategy to achieve synergistic lung cancer therapy, reduce drug dose, and decrease side effects. In the present study, we synthesized a pH and glutathione (GSH) sensitive prodrug, cisplatin (CIS) and doxorubicin (DOX) conjugates (CIS-DOXp). CIS-DOXp was loaded by nanocarriers and delivered into the tumor site.

Methods

pH and GSH sensitive CIS-DOX prodrug (CIS-DOXp) was synthesized by conjugating GSH responsive CIS prodrug with pH sensitive DOX prodrug. CIS-DOXp-loaded nanocarriers (CIS-DOXp NC) were prepared using emulsification and solvent evaporation method. The morphology, particle size, polydispersity index (PDI) and zeta potential of nanocarriers were measured. In vitro cytotoxicity of nanocarriers and the corresponding free drugs was examined using the MTT assay. In vivo anti-tumor efficiency and biodistribution behaviors were evaluated on lung cancer mice models.

Results

The size, PDI, zeta potential, CIS loading efficiency, and DOX loading efficiency of CIS-DOXp NC were 128.6 ± 3.2 nm, 0.196 ± 0.021, 15.7 ± 1.7 mV, 92.1 ± 2.1%, and 90.4 ± 1.8%, respectively. The best cell killing ability (the lowest combination index of 0.57) was found at the combination ratio of 1:3 (CIS:DOX, w/w) in the drugs co-loaded formulations, indicating the strongest synergism effect. CIS-DOXp NC showed the best tumor inhibition efficiency (79.9%) in mice with negligible body weight lost.

Conclusion

CIS-DOXp NC could be applied as a promising system for the synergistic chemotherapy of lung 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.

The chemical biology of IL-12 production via the non-canonical NFkB pathway

Interleukin-12 (IL-12) has emerged as an attractive cytokine for cancer therapy because it has direct anti-cancer effects and additionally plays a critical role in enhancing checkpoint inhibitors. Given these multiple modes of actions, identifying means to pharmacologically induce IL-12 production in the tumor microenvironment has become important. In this review, we highlight therapeutics that promote IL-12 induction in tumor-associated myeloid cells through the non-canonical NFkB pathway. We discuss existing clinical trials and briefly examine the additional pathway targets that warrant further exploration for drug discovery.

pH-Responsive Nanoparticles for Cancer Immunotherapy: A Brief Review

Immunotherapy has recently become a promising strategy for the treatment of a wide range of cancers. However, the broad implementation of cancer immunotherapy suffers from inadequate efficacy and toxic side effects. Integrating pH-responsive nanoparticles into immunotherapy is a powerful approach to tackle these challenges because they are able to target the tumor tissues and organelles of antigen-presenting cells (APCs) which have a characteristic acidic microenvironment. The spatiotemporal control of immunotherapeutic drugs using pH-responsive nanoparticles endows cancer immunotherapy with enhanced antitumor immunity and reduced off-tumor immunity. In this review, we first discuss the cancer-immunity circle and how nanoparticles can modulate the key steps in this circle. Then, we highlight the recent advances in cancer immunotherapy with pH-responsive nanoparticles and discuss the perspective for this emerging area.

Advanced biomaterials for cancer immunotherapy

Immunotherapy, as a powerful strategy for cancer treatment, has achieved tremendous efficacy in clinical trials. Despite these advancements, there is much to do in terms of enhancing therapeutic benefits and decreasing the side effects of cancer immunotherapy. Advanced nanobiomaterials, including liposomes, polymers, and silica, play a vital role in the codelivery of drugs and immunomodulators. These nanobiomaterial-based delivery systems could effectively promote antitumor immune responses and simultaneously reduce toxic adverse effects. Furthermore, nanobiomaterials may also combine with each other or with traditional drugs via different mechanisms, thus giving rise to more accurate and efficient tumor treatment. Here, an overview of the latest advancement in these nanobiomaterials used for cancer immunotherapy is given, describing outstanding systems, including lipid-based nanoparticles, polymer-based scaffolds or micelles, inorganic nanosystems, and others.

Synthetic MUC1 breast cancer vaccine containing a Toll-like receptor 7 agonist exerts antitumor effects

Adjuvant immunotherapy has recently emerged as a potential treatment strategy for breast cancer. The tumor-associated protein mucin 1 (MUC1) has received increasing attention due to its high expression in numerous types of common tumors, in which MUC1 acts as a cancer antigen. However, the simple mixed composition of an adjuvant and a peptide is not a sufficient rationale for a MUC1 peptide-based vaccine. The present study developed a novel Toll-like receptor 7 (TLR7) agonist-conjugated MUC1 peptide vaccine (T7-MUC1), which elicited an effective immune response and a robust antitumor effect in a mouse breast cancer model. In vitro, T7-MUC1 significantly increased the release of cytokines in mouse bone marrow dendritic cells and spleen lymphocytes, and induced the dendritic cell-cytokine-induced killer response against tumor cells with high MUC1 expression. In vivo, it was observed that the 4T1 tumor weights in mice immunized with the T7-MUC1 conjugate were reduced by ≥70% compared with those in the control group. Furthermore, the therapeutic responses in vivo were attributed to the increase in specific humoral and cellular immunity, including high antibody titers, antibody-dependent cell-mediated cytotoxicity and cytotoxic T-lymphocyte activity. The percentages of CD3⁺/CD8⁺ T-cells were significantly higher in the T7-MUC1 treatment group compared with those in the control group. Therefore, the results of the present study suggested that the T7-MUC1 vaccine inhibited tumor growth in mice and thus may have potential as a therapeutic candidate in clinical trials for breast cancer immunotherapy.

Lymph node-targeted immune-activation mediated by imiquimod-loaded mesoporous polydopamine based-nanocarriers

Toll-like receptor (TLR) agonists are the potent stimulants of innate immune system and hold promises as an adjuvant for anticancer immunotherapy. Unfortunately, most of them are limited by a prompt dissemination, and thus caused "wasted inflammation". Hence, how to restrict their action radius into lymphoid tissues is of great relevance to enhance their efficacy and concomitantly alleviates the side effects. Here, imiquimod (R837), a TLR 7 agonist, was loaded into mesoporous polydopamine (MPDA) nanocarriers with high efficiency. Moreover, its surface was modified by polyvinyl pyrrolidone (PVP) to enhance their lymphatic drainage ability. These nano-adjuvants have obvious advantages in promoting dendritic cell (DC) maturation in comparison to free R837. Moreover, their transportation and retention ability in proximal lymph nodes (LNs) were also confirmed, by which lymphatic drug exposure can be maximized to a great extent. Consequently, effective DC activation and CD8⁺ T cell responses were observed as expected by R837 released in draining LNs. This effect was further enhanced by the presence of endogenous tumor antigens from apoptosis debris induced by MPDA-based photothermal effect, and thus led to the growth inhibition of subcutaneous B16 melanomas. The results demonstrated the great potency against melanoma of the designed PVP-MPDA@R837 nano-adjuvants by combining photothermal conversion property of MPDA with lymphatic-focused immune-activation.

Immunostimulatory TLR7 agonist-nanoparticles together with checkpoint blockade for effective cancer immunotherapy

Mono- or dual-checkpoint inhibitors for immunotherapy have changed the paradigm of cancer care; however, only a minority of patients responds to such treatment. Combining small molecule immuno-stimulators can improve treatment efficacy, but they are restricted by poor pharmacokinetics. In this study, TLR7 agonists conjugated onto silica nanoparticles showed extended drug localization after intratumoral injection. The nanoparticle-based TLR7 agonist increased immune stimulation by activating the TLR7 signaling pathway. When treating CT26 colon cancer, nanoparticle conjugated TLR7 agonists increased T cell infiltration into the tumors by > 4× and upregulated expression of the interferon γ gene compared to its unconjugated counterpart by ~2×. Toxicity assays established that the conjugated TLR7 agonist is a safe agent at the effective dose. When combined with checkpoint inhibitors that target programmed cell death protein 1 (PD-1) and cytotoxic T-lymphocyte-associated protein 4 (CTLA-4), a 10-100× increase in immune cell migration was observed; furthermore, 100 mm3 tumors were treated and a 60% remission rate was observed including remission at contralateral non-injected tumors. The data show that nanoparticle based TLR7 agonists are safe and can potentiate the effectiveness of checkpoint inhibitors in immunotherapy resistant tumor models and promote a long-term specific memory immune function.

TLR7/8 Agonist-Loaded Nanoparticles Augment NK Cell-Mediated Antibody-Based Cancer Immunotherapy

Activated natural killer (NK) cells can kill malignant tumor cells via granule exocytosis and secretion of IFN-γ, a key regulator of the TH1 response. Thus, mobilization of NK cells can augment cancer immunotherapy, particularly when mediated through antibody-dependent cellular cytotoxicity (ADCC). Stimulation of toll-like receptor (TLR)7/8 activity in dendritic cells promotes pro-inflammatory cytokine secretion and costimulatory molecule upregulation, both of which can potentiate NK cell activation. However, currently available TLR7/8 agonists exhibit unfavorable pharmacokinetics, limiting their in vivo efficacy. To enable efficient delivery to antigen-presenting cells, we encapsulated a novel imidazoquinoline-based TLR7/8 agonist in pH-responsive polymeric NPs. Enhanced costimulatory molecule expression on dendritic cells and a stronger pro-inflammatory cytokine response were observed with a NP-encapsulated agonist, compared to that with the soluble form. Treatment with NP-encapsulated agonists resulted in stronger in vivo cytotoxicity and prolonged activation of NK cells compared to that with a soluble agonist. In addition, TLR7/8 agonist-loaded NPs potentiated stronger NK cell degranulation, which resulted in enhanced in vitro and in vivo ADCC mediated by the epidermal growth factor receptor-targeting antibody cetuximab. TLR7/8 agonist-loaded NP treatment significantly enhanced the antitumor efficacy of cetuximab and an anti-HER2/neu antibody in mouse tumor models. Collectively, our data show that a pH-responsive NP-encapsulating TLR7/8 agonist could be used as a potent immunostimulatory adjuvant for antibody-based cancer immunotherapy by promoting NK cell activation.

Harnessing the immune system to fight cancer with Toll-like receptor and RIG-I-like receptor agonists

Cancer immunotherapy has come of age with the advent of immune checkpoint inhibitors. In this article we review how agonists for receptors of the innate immune system, the Toll-like receptors and the RIG-I-like receptors, impact anticancer immune responses. Treatment with these agonists enhances the activity of anticancer effector cells, such as cytotoxic T cells and NK cells, and at the same time blocks the activity of immunosuppressive cell types such as regulatory T cells and myeloid-derived suppressor cells. These compounds also impact the recruitment of immune cells to the tumor. The phenomena of pattern-recognition receptor tolerance and reprogramming and their implications for immunotherapy are discussed. Finally, novel delivery systems that target the immune-stimulating drugs to the tumor or the tumor-draining lymph nodes to enhance their efficacy and safety are presented.

Site-specific MOF-based immunotherapeutic nanoplatforms via synergistic tumor cells-targeted treatment and dendritic cells-targeted immunomodulation

An efficient antitumor immune response relies on multiple cells-based process including tumor cells-targeted immunogenicity increment, dendritic cells (DCs)-targeted vaccine delivery and T cells-mediated tumor elimination. Only limited immune efficacy could be achieved by strengthening the function of single type of cells. Therefore, building an effective immunotherapeutic nanoplatform by simultaneously modulating the functions of multiple cells involved in immune process is urgently demanded. However, it is challenging to modulate multiple cells since the on-demand delivery of diverse agents to different cells is restricted by inherent different target sites. Herein, as a proof of concept, dual tailor-made metal organic framework (MOF) nanoparticles based on zeolitic imidazolate framework-8 (ZIF-8) are designed to comprehensively enhance the immunotherapy via the spatiotemporal cooperation of various therapeutic agents including photothermal agent IR820, adjuvant imiquimod (R837) and immunomodulator 1-methyl-d-tryptophan (1 MT). On one hand, IR820@ZIF-8 is modified with hyaluronic acid for realizing tumor-targeted photothermal therapy, accompanied with the release of tumor antigens. On the other hand, (R837+1 MT)@ZIF-8 is modified with mannan for achieving DCs-targeted immune amplification. The synergistic tumor cells-targeted treatment and DCs-targeted immunomodulation can efficiently overcome two major obstacles in immunotherapy: inadequate activation of immune response and immune evasion, offering powerful platform against invasive malignancy and rechallenged tumors.

Nanomedicine in osteosarcoma therapy: Micelleplexes for delivery of nucleic acids and drugs toward osteosarcoma-targeted therapies

Osteosarcoma(OS) represents the main cancer affecting bone tissue, and one of the most frequent in children. In this review we discuss the major pathological hallmarks of this pathology, its current therapeutics, new active biomolecules, as well as the nanotechnology outbreak applied to the development of innovative strategies for selective OS targeting. Small RNA molecules play a role as key-regulator molecules capable of orchestrate different responses in what concerns cancer initiation, proliferation, migration and invasiveness. Frequently associated with lung metastasis, new strategies are urgent to upgrade the therapeutic outcomes and the life-expectancy prospects. Hence, the prominent rise of micelleplexes as multifaceted and efficient structures for nucleic acid delivery and selective drug targeting is revisited here with special emphasis on ligand-mediated active targeting. Future landmarks toward the development of novel nanostrategies for both OS diagnosis and OS therapy improvements are also discussed.

Ratiometric co-delivery of doxorubicin and docetaxel by covalently conjugating with mPEG-poly(β-malic acid) for enhanced synergistic breast tumor therapy

Ratiometric codelivery of doxorubicin and docetaxel through an engineered nanoconjugate based on mPEG-PMLA facilitates the accumulation of drugs at the tumor site and enhances synergistic antitumor response.

Hybrid nanovaccine for the co-delivery of the mRNA antigen and adjuvant

For efficient cancer vaccines, the antitumor function largely relies on cytotoxic T cells, whose activation can be effectively induced via antigen-encoding mRNA, making mRNA-based cancer vaccines an attractive approach for personalized cancer therapy. While the liposome-based delivery system enables the systemic delivery and transfection of mRNA, incorporating an adjuvant that is non-lipid like remains challenging, although the co-delivery of mRNA (antigen) and effective adjuvant is key to the activation of the cytotoxic T cells. This is because the presence of an adjuvant is important for dendritic cell maturation-another necessity for cytotoxic T cell activation. In the present work, we designed a poly (lactic-co-glycolic acid) (PLGA)-core/lipid-shell hybrid nanoparticle carrier for the co-delivery of mRNA and gardiquimod (adjuvant that cannot be incorporated into the lipid shell). We demonstrated in the present work that the co-delivery of mRNA and gardiquimod led to the effective antigen expression and DC maturation in vitro. The intravenous administration of the hybrid nanovaccine resulted in the enrichment of mRNA expression in the spleen and a strong immune response in vivo. The simultaneous delivery of the antigen and adjuvant both spatially and temporally via the core/shell nanoparticle carrier is found to be beneficial for tumor growth inhibition.

Nanotechnology platforms for cancer immunotherapy

Various cancer therapies have advanced remarkably over the past decade. Unlike the direct therapeutic targeting of tumor cells, cancer immunotherapy is a new strategy that boosts the host's immune system to detect specific cancer cells for efficient elimination. Nanoparticles incorporating immunomodulatory agents can activate immune cells and modulate the tumor microenvironment to enhance antitumor immunity. Such nanoparticle-based cancer immunotherapies have received considerable attention and have been extensively studied in recent years. This review thus focuses on nanoparticle-based platforms (especially naturally derived nanoparticles and synthetic nanoparticles) utilized in recent advances; summarizes delivery systems that incorporate various immune-modulating agents, including peptides and nucleic acids, immune checkpoint inhibitors, and other small immunostimulating agents; and introduces combinational cancer immunotherapy with nanoparticles, especially nanoparticle-based photo-immunotherapy and nanoparticle-based chemo-immunotherapy. Undoubtedly, the recent studies introduced in this review prove that nanoparticle-incorporated cancer immunotherapy is a highly promising treatment modality for patients with cancer. Nonetheless further research is needed to solve safety concerns and improve efficacy of nanoplatform-based cancer immunotherapy for future clinical application. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease.

Advances of functional nanomaterials for cancer immunotherapeutic applications

Immunotherapy has made great progress by modulating the body's own immune system to fight against cancer cells. However, the low response rates of related drugs limit the development of immunotherapy strategies. Fortunately, the advantages of nanotechnology can just make up for this shortcoming. Nanocarriers of diverse systems are utilized to co-deliver antigens and adjuvants, combined with drugs for immunomodulatory, such as chemotherapy, radiotherapy, and photodynamic. Here we review recent studies on immunotherapy with biomimetic, organic, and inorganic nanomaterials. They are going to potentially overcome the drawbacks in cancer immunotherapy with delivering immunomodulatory drugs, delivering cancer vaccine, and monitoring the immune systems. This article is characterized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease.

Nucleic acids presenting polymer nanomaterials as vaccine adjuvants

Most vaccines developed today include only the antigens that best stimulate the immune system rather than the entire virus or microbe, which makes vaccine production and use safer and easier, though they lack potency to induce acceptable immunity and long-term protection. The incorporation of additional immune stimulating components, named adjuvants, is required to generate a strong protective immune response. Nucleic acids (DNA and RNA) and their synthetic analogs are promising candidates as vaccine adjuvants activating Toll-like receptors (TLRs). Additionally, in the last few years several nanocarriers have emerged as platforms for targeted co-delivery of antigens and adjuvants. In this review, we focus on the recent developments in polymer nanomaterials presenting nucleic acids as vaccine adjuvants. We aim to compare the effectiveness of the various classes of polymers in immune modulating materials (nanoparticles, dendrimers, single-chain particles, nanogels, polymersomes and DNA-based architectures). In particular, we address the critical role of parameters such as size, shape, complexation and release of TLR ligands, cellular uptake, stability, toxicity and potential importance of spatial control in ligand presentation.