Polymeric nanoparticles promote macrophage reversal from M2 to M1 phenotypes in the tumor microenvironment

At the bench: Engineering the next generation of cancer vaccines

Cancer vaccines hold promise as an immunotherapeutic modality based on their potential to generate tumor antigen-specific T cell responses and long-lived antitumor responses capable of combating metastatic disease and recurrence. However, cancer vaccines have historically failed to deliver significant therapeutic benefit in the clinic, which we maintain is due in part to drug delivery challenges that have limited vaccine immunogenicity and efficacy. In this review, we examine some of the known and putative failure mechanisms of common first-generation clinical cancer vaccines, and describe how the rational design of materials engineered for vaccine delivery and immunomodulation can address these shortcomings. First, we outline vaccine design principles for augmenting cellular immunity to tumor antigens and describe how well-engineered materials can improve vaccine efficacy, highlighting recent innovations in vaccine delivery technology that are primed for integration into neoantigen vaccine development pipelines. We also discuss the importance of sequencing, timing, and kinetics in mounting effective immune responses to cancer vaccines, and highlight examples of materials that potentiate antitumor immunity through spatiotemporal control of immunomodulation. Furthermore, we describe several engineering strategies for improving outcomes of in situ cancer vaccines, which leverage local, intratumoral delivery to stimulate systemic immunity. Finally, we highlight recent innovations leveraging nanotechnology for increasing the immunogenicity of the tumor microenvironment (TME), which is critical to enhancing tumor infiltration and function of T cells elicited in response to cancer vaccines. These immunoengineering strategies and tools complement ongoing advances in cancer vaccines as they reemerge as an important component of the immunotherapeutic armamentarium.

Mesoporous Silica as a Versatile Platform for Cancer Immunotherapy

Immunotherapy has been recognized for decades as a promising therapeutic method for cancer treatment. To enhance host immune responses against cancer, antigen-presenting cells (APCs; e.g., dendritic cells) or T cells are educated using immunomodulatory agents including tumor-associated antigens and adjuvants, and manipulated to induce a cascading adaptive immune response targeting tumor cells. Mesoporous silica materials are promising candidates to improve cancer immunotherapy based on their attractive properties that include high porosity, high biocompatibility, facile surface modification, and self-adjuvanticity. Here, the recent progress on mesoporous-silica-based immunotherapies based on two material forms is summarized: 1) mesoporous silica nanoparticles (MSNs), which can be internalized into APCs, and 2) micrometer-sized mesoporous silica rods (MSRs) that can form a 3D space to recruit APCs. Subcutaneously injected MSN-based cancer vaccines can be taken up by peripheral APCs or by APCs in lymphoid organs to educate the immune system against cancer cells. MSR cancer vaccines can recruit immune cells into the MSR scaffold to induce cancer-specific immunity. Both vaccine systems successfully stimulate the adaptive immune response to eradicate cancer in vivo. Thus, mesoporous silica has potential value as a material platform for the treatment of cancer or infectious diseases.

In Situ Manipulation of Dendritic Cells by an Autophagy-Regulative Nanoactivator Enables Effective Cancer Immunotherapy

Cellular immunotherapeutics aim to employ immune cells as anticancer agents. Ex vivo engineering of dendritic cells (DCs), the initial role of an immune response, benefits tumor elimination by boosting specific antitumor responses. However, directly activating DCs in vivo is less efficient and therefore quite challenging. Here, we designed a nanoactivator that manufactures DCs through autophagy upregulating in vivo directly, which lead to a high-efficiency antigen presention of DCs and antigen-specific T cells generation. The nanoactivator significantly enhances tumor antigen cross-presentation and subsequent T cell priming. Consequently, in vivo experiments show that the nanoactivators successfully reduce tumor growth and prolong murine survival. Taken together, these results indicate in situ DCs manipulation by autophagy induction is a promising strategy for antigen presentation enhancement and tumor elimination.

Two-Way Cruise Nanosatellite Promotes Metastasis Inhibition by Immunochemotherapy

Currently, immunochemotherapy based on tumor-associated macrophages (TAMs) is mainly used for elimination of M2 macrophages. However, these methods cannot make full use of the positive immune-modulatory effects of macrophages. This study explores a two-way cruise strategy for combining immunotherapy based on TAM phenotype reversal with classical chemotherapy, the nanosatellites (DOX@HFn-PGZL@Res) are proposed to accurately deliver the chemotherapeutic agents and immune activators to their respective target cells. When the delivery system is recruited to tumor microenvironment, the nanosatellites are separated into DOX@HFn and Res@GZL nanoparticles, which can enter cancer cells and M2-TAMs, respectively. The data show that DOX@HFn-PGZL@Res successfully re-educate M2 to M1 macrophages, resulting in an activated immune response and inhibition of tumor invasion and metastasis. In general, this work describes a two-way homing nanoplatform for the integration of immunotherapy and chemotherapy, which provides a new idea for the "attack-defense" integrated treatment of tumor.

Targeted delivery of ibrutinib to tumor-associated macrophages by sialic acid-stearic acid conjugate modified nanocomplexes for cancer immunotherapy

Ibrutinib (IBR), an irreversible Bruton's tyrosine kinase (BTK) inhibitor, is expected to be a potent therapeutic modality, given that BTK is overexpressed in tumor-associated macrophages (TAMs) and participates in promoting tumor progression, angiogenesis, and immunosuppression. However, rapid clearance in vivo and low tumor accumulation have rendered effective uptake of IBR by TAMs challenge. Herein, we designed and synthesized a sialic acid (SA)-stearic acid conjugate modified on the surface of nanocomplexes to encapsulate IBR (SA/IBR/EPG) for targeted immunotherapy. Amphiphilic egg phosphatidylglycerol (EPG) structure and strong IBR-EPG interactions render these nanocomplexes high IBR loading capacity, prolonged blood circulation, and optimal particle sizes (∼30 nm), which can effectively deliver IBR to the tumor, followed by subsequent internalization of IBR by TAMs through SA-mediated active targeting. In vitro and in vivo tests showed that the prepared SA/IBR/EPG nanocomplexes could preferentially accumulate in TAMs and exert potent antitumor activity. Immunofluorescence staining analysis further confirmed that SA/IBR/EPG remarkably inhibited angiogenesis and tumorigenic cytokines released by TAM and eventually suppressed tumor progression, without eliciting any unwanted effect. Thus, SA-decorated IBR nanocomplexes present a promising strategy for cancer immunotherapy. STATEMENT OF SIGNIFICANCE: Ibrutinib (IBR), an irreversible Bruton's tyrosine kinase (BTK) inhibitor, is expected to be a potent therapeutic modality, given that BTK is overexpressed in tumor-associated macrophages (TAMs) and participates in promoting tumor progression, angiogenesis, and immunosuppression. However, rapid clearance in vivo and low tumor accumulation have rendered effective uptake of IBR by TAMs challenge. Herein, we designed and synthesized a sialic acid (SA)-stearic acid conjugate modified on the surface of nanocomplexes to encapsulate IBR (SA/IBR/EPG) for targeted delivery of IBR to TAMs. The developed SA/IBR/EPG nanocomplexes exhibited high efficiency in targeting TAMs and inhibiting BTK activation, consequently inhibiting Th2 tumorigenic cytokine release, reducing angiogenesis, and suppressing tumor growth. These results implied that the SA/IBR/EPG nanocomplex could be a promising strategy for TAM-targeting immunotherapy with minimal systemic side effects.

Modulation of macrophage phenotype via phagocytosis of drug-loaded microparticles

Monocyte-derived macrophages play a critical role in directing wound pathology following injury. Depending on their phenotype, macrophages also promote tissue regeneration. However, the therapeutic administration of macrophages with a controlled phenotype is challenging because macrophages are highly plastic and quickly revert to a detrimental, inflammatory phenotype in response to the environment of a damaged tissue. To address this issue, we developed a novel strategy to modulate macrophage phenotype intracellularly through phagocytosis of drug-loaded microparticles. Poly(lactic-co-glycolic acid) microparticles loaded with the anti-inflammatory drug dexamethasone (Dex) were phagocytosed by monocytes and stored intracellularly for at least 5 days. After differentiation into macrophages, cell phenotype was characterized over time with high-throughput gene expression analysis via NanoString. We found that the microparticles modulated macrophage phenotype for up to 7 days after microparticle uptake, with decreases in inflammation-related genes at early timepoints and upregulation of homing- and phagocytosis-related genes at multiple timepoints in a manner similar to cells treated with continuous free Dex. These data suggest that intracellularly loading macrophages with Dex microparticles via phagocytosis could be a unique methodology to selectively modulate macrophage phenotype over time. This strategy would allow therapeutic administration of macrophages for the treatment of a number of inflammatory disease and disorders. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 107A: 1213-1224, 2019.

Nanomaterial-Based Modulation of Tumor Microenvironments for Enhancing Chemo/Immunotherapy

The tumor microenvironment (TME) has drawn considerable research attention as an alternative target for nanomedicine-based cancer therapy. Various nanomaterials that carry active substances have been designed to alter the features or composition of the TME and thereby improve the delivery and efficacy of anticancer chemotherapeutics. These alterations include disruption of the extracellular matrix and tumor vascular systems to promote perfusion or modulate hypoxia. Nanomaterials have also been used to modulate the immunological microenvironment of tumors. In this context, nanomaterials have been shown to alter populations of cancer-associated fibroblasts, tumor-associated macrophages, regulatory T cells, and myeloid-derived suppressor cells. Despite considerable progress, nanomaterial-based TME modulation must overcome several limitations before this strategy can be translated to clinical trials, including issues related to limited tumor tissue penetration, tumor heterogeneity, and immune toxicity. In this review, we summarize recent progress and challenges of nanomaterials used to modulate the TME to enhance the efficacy of anticancer chemotherapy and immunotherapy.

Simultaneous T Cell Activation and Macrophage Polarization to Promote Potent Tumor Suppression by Iron Oxide-Embedded Large-Pore Mesoporous Organosilica Core-Shell Nanospheres

Nanomaterial-based immunotherapy stimulating T cell activation or tumor-associated macrophage (TAM) conversion holds great promise for promoting tumor suppression. Herein, a novel nanoplatform, iron oxide-embedded large-pore mesoporous organosilica nanospheres (IO-LPMONs), is prepared for the first time to simultaneously activate cytotoxic T cells and polarize macrophages for potent tumor immunotherapy. The IO-LPMONs have large mesopores (6.3 nm) and inorganic-organic hybrid shells, which contribute to a high payload (500 µg mg^-1 ) of the antigen ovalbumin (OVA). The IO-LPMONs effectively deliver OVA to dendritic cells (DCs) and activate DCs. Subsequently, high activation of both CD4⁺ and CD8⁺ effector antigen-specific T cells is achieved for powerful antitumor effects. Moreover, the IO-LPMONs also act as an immune modulator to polarize TAMs from an immunosuppressive M2 to a tumor-killing M1 phenotype, which induces efficient apoptosis of tumor cells. The combined T cell activation and macrophage polarization strategy based on the IO-LPMONs elicits remarkable combined antitumor effects in vivo, showing great promise for tumor treatment.

Impact of Locally Administered Carboxydextran-Coated Super-Paramagnetic Iron Nanoparticles on Cellular Immune Function

Interstitially administered iron oxide particles are currently used for interoperative localization of sentinel lymph nodes (LNs) in cancer staging. Several studies have described concerns regarding the cellular accumulation of iron oxide nanoparticles relating them to phenotype and function deregulation of macrophages, impairing their ability to mount an appropriate immune response once an insult is present. This study aims to address what phenotypic and functional changes occur during lymphatic transit and accumulation of these particles. Data show that 60 nm carboxydextran-coated iron nanoparticles use a noncellular mechanism to reach the draining LNs and that their accumulation in macrophages induces transient phenotypic and functional changes. Nevertheless, macrophages recover their baseline levels of response within 7 days, and are still able to mount an appropriate response to bacterially induced inflammation.

Tailoring Nanomaterials for Targeting Tumor-Associated Macrophages

Advances in the field of nanotechnology together with an increase understanding of tumor immunology have paved the way for the development of more personalized cancer immuno-nanomedicines. Nanovehicles, due to their specific physicochemical properties, are emerging as key translational moieties in tackling tumor-promoting, M2-like tumor-associated macrophages (TAMs). Cancer immuno-nanomedicines target TAMs primarily by blocking M2-like TAM survival or affecting their signaling cascades, restricting macrophage recruitment to tumors and re-educating tumor-promoting M2-like TAMs to the tumoricidal, M1-like phenotype. Here, the TAM effector mechanisms and strategies for targeting TAMs are summarized, followed by a focus on the mechanistic considerations in the development of novel immuno-nanomedicines. Furthermore, imaging TAMs with nanoparticles so as to forecast a patient's clinical outcome, describing treatment options, and observing therapy responses is also discussed. At present, strategies that target TAMs are being investigated not only at the basic research level but also in early clinical trials. The significance of TAM-targeting biomaterials is highlighted, with the goal of facilitating future clinical translation.

Synergetic Functional Nanocomposites Enhance Immunotherapy in Solid Tumors by Remodeling the Immunoenvironment

Checkpoint blockade immunotherapy has demonstrated significant clinical success in various malignant tumors. However, the therapeutic response is limited due to the immunosuppressive tumor microenvironment (ITM). In this study, a functional nanomaterial, layered double hydroxides (LDHs), carrying specific functional miR155 is developed to modulate ITM by synergistically repolarizing tumor associated macrophages (TAMs) to M1 subtype. LDH nanoparticles loaded with miR155 (LDH@155) exhibit superior ability in cellular uptake by murine macrophages, miR escape into the cytoplasm and TAMs specific delivery when introtumoral administration. Meanwhile, upon exposure to LDH@155, TAMs are significantly skewed to M1 subtype, which markedly inhibits myeloid-derived suppressor cells (MDSCs) formation and stimulates T-lymphocytes to secrete more interferon-γ (IFN-γ) cytokines in vitro. Introtumoral administration of LDH@155 reduces the percentage of TAMs and MDSCs in the tumor and elevates CD4+ and CD8+ T cell infiltration and activation, which can promote therapeutic efficiency of α-PD-1 antibody immunotherapy. Furthermore, it is found that LDH@155 significantly decreases the expression level of phosphorylated STAT3 and ERK1/2 and activates NF-κB expression in TAMs, indicating that the STAT3, ERK1/2, and NF-κB signaling pathways may involve in LDH@155-induced macrophage polarization. Overall, the results suggest that LDH@155 nanoparticles may, in the future, function as a promising agent for cancer combinational immunotherapy.

Emerging Nano-/Microapproaches for Cancer Immunotherapy

Cancer immunotherapy has achieved remarkable clinical efficacy through recent advances such as chimeric antigen receptor-T cell (CAR-T) therapy, immune checkpoint blockade (ICB) therapy, and neoantigen vaccines. However, application of immunotherapy in a clinical setting has been limited by low durable response rates and immune-related adverse events. The rapid development of nano-/microtechnologies in the past decade provides potential strategies to improve cancer immunotherapy. Advances of nano-/microparticles such as virus-like size, high surface to volume ratio, and modifiable surfaces for precise targeting of specific cell types can be exploited in the design of cancer vaccines and delivery of immunomodulators. Here, the emerging nano-/microapproaches in the field of cancer vaccines, immune checkpoint blockade, and adoptive or indirect immunotherapies are summarized. How nano-/microparticles improve the efficacy of these therapies, relevant immunological mechanisms, and how nano-/microparticle methods are able to accelerate the clinical translation of cancer immunotherapy are explored.

Intratumoral fate of functional nanoparticles in response to microenvironment factor: Implications on cancer diagnosis and therapy

The extraordinary growth and progression of tumor require enormous nutrient and energy. Unregulated behaviors of cancer cell progressing and persistently change of tumor microenvironment (TME) which acts as the soil for cancer growth and metastasis are the ubiquitous features. The tumor microenvironment exhibits some unique features which differ with the normal tissues. While the nanoparticles get through the blood vessel leakage, they encounter immediately and interact directly with these microenvironment factors. These factors may inhibit the diffusion of nanoparticles from penetrating through the tumor, or induce the dissociation of nanoparticles. Different nanoparticles encountered with different intratumoral microenvironment factors end up in different way. Therefore, in this review, we first briefly introduced the formations, distributions, features of some intratumoral microenvironment, and their effects on the tumor progression. They include extracellular matrix (ECM), matrix metalloproteinases (MMPs), acidic/hypoxia environment, redox environment, and tumor associated macrophages (TAMs). We then exemplified how these factors interact with nanoparticles and emphasized the potentials and challenges of nanoparticle-based strategies facing in enhancing intratumoral penetration and tumor microenvironment remodeling. We hope to give a simple understanding of the interaction between these microenvironment factors and the nanoparticles, thus, favors the designing and constructing of more ideal functional nanoparticles.

Directing toll-like receptor signaling in macrophages to enhance tumor immunotherapy

A key challenge facing immunotherapy is poor infiltration of T cells into tumors, along with suppression of cells reaching these sites. However, macrophages make up a majority of immune cell infiltrates into tumors, creating natural targets for immunotherapies able to direct macrophages away from tumor-supportive functions and toward anti-tumor phenotypes. Recent studies demonstrate that toll-like receptors (TLRs) - pathways that quickly trigger early immune responses - play an important role in polarizing macrophages. Here, we present emerging ways in which TLR signaling is being manipulated in macrophages to create new opportunities for cancer immunotherapy. In particular, we discuss approaches to deliver TLR agonists, to leverage biomaterials in these therapies, and to couple TLR-based approaches with other frontline treatments as combination cancer therapies.

Challenges and potential of PD-1/PD-L1 checkpoint blockade immunotherapy for glioblastoma

PD-1/PD-L1 checkpoint blockades have achieved significant progress in several kinds of tumours. Pembrolizumab, which targets PD-1, has been approved as a first-line treatment for advanced non-small cell lung cancer (NSCLC) patients with positive PD-L1 expression. However, PD-1/PD-L1 checkpoint blockades have not achieved breakthroughs in treating glioblastoma because glioblastoma has a low immunogenic response and an immunosuppressive microenvironment caused by the precise crosstalk between cytokines and immune cells. A phase III clinical trial, Checkmate 143, reported that nivolumab, which targets PD-1, did not demonstrate survival benefits compared with bavacizumab in recurrent glioblastoma patients. Thus, the combination of a PD-1/PD-L1 checkpoint blockade with RT, TMZ, antibodies targeting other inhibitory or stimulatory molecules, targeted therapy, and vaccines may be an appealing solution aimed at achieving optimal clinical benefit. There are many ongoing clinical trials exploring the efficacy of various approaches based on PD-1/PD-L1 checkpoint blockades in primary or recurrent glioblastoma patients. Many challenges need to be overcome, including the identification of discrepancies between different genomic subtypes in their response to PD-1/PD-L1 checkpoint blockades, the selection of PD-1/PD-L1 checkpoint blockades for primary versus recurrent glioblastoma, and the identification of the optimal combination and sequence of combination therapy. In this review, we describe the immunosuppressive molecular characteristics of the tumour microenvironment (TME), candidate biomarkers of PD-1/PD-L1 checkpoint blockades, ongoing clinical trials and challenges of PD-1/PD-L1 checkpoint blockades in glioblastoma.

In vitro inhibition of tumor growth by low-dose iron oxide nanoparticles activating macrophages

Macrophages as immunocyte are attracting more and more attention in cancer therapy. Our previous study observed that dimercaptosuccinic acid (DMSA)-coated Fe3O4 magnetic nanoparticles triggered comprehensive immune responses of mouse macrophages (RAW264.7 cells) and induced production of many kinds of cytokines. This study investigated the effects of Fe3O4 magnetic nanoparticles on RAW264.7 cells proliferation, migration, and inhibition of tumor growth in vitro. Fe3O4 magnetic nanoparticles had an average size of about 11 nm with good dispersibility and uniformity. Fe3O4 magnetic nanoparticles internalized efficiently into RAW264.7 cells. Through Cell Counting Kit-8 (CCK-8) detection, the proliferation of RAW264.7 cells significantly increased by the low-dose Fe3O4 magnetic nanoparticles (50 µg/mL) treatment. The results of wound-healing and Transwell assays both displayed a significant promotion of the RAW264.7 cells migratory capability compared with control group ( P<0.01). It is interesting to find that a large number of proliferated RAW264.7 cells were activated to surround quickly and attack mouse liver cancer cell (Hepa1-6) cells by Fe3O4 magnetic nanoparticles. The growth of Hepa1-6 cells was effectively inhibited according to microscope imaging and flow cytometry analysis. The inhibition may be cooperative effects of RAW264.7 cells proliferation, migration, and immune activation. The results suggest potential clinical value of low-dose iron oxide nanomaterials in cancer therapy.

Progress in Tumor-Associated Macrophages: From Bench to Bedside

Tumor-associated macrophages (TAMs) are of great interest in cancer immunology as they play an important role in the tumor microenvironment as cancer stromal cells recruited from circulating monocytes. TAMs are closely associated with tumor progression, including initiation, trophic growth, metabolism, angiogenesis, and metastasis; moreover, in clinical practice, their quantity can be related to poor prognosis. Fundamental and translational studies imply that TAMs are one of the most promising targets in tumor therapy. Herein, the biological origination and classification of TAMs, which correspond to their functions and differentiations, are reviewed in detail. In addition, recent basic research and clinical preprocess of TAMs in tumor immunotherapy are also discussed. Finally, the advances in the use of nanotechnology and TAMs for tumor therapy are discussed. This review focuses on the background and status of basic research and clinical significance of TAMs, points out the potential of TAMs in tumor immunological therapy, and clarifies the possibility of translation TAM-targeting therapies in medicine.

Recent Advances in Polymeric Nanomedicines for Cancer Immunotherapy

Immunotherapy has emerged as a promising approach to treat cancer, since it facilitates eradication of cancer by enhancing innate and/or adaptive immunity without using cytotoxic drugs. Of the immunotherapeutic approaches, significant clinical potentials are shown in cancer vaccination, immune checkpoint therapy, and adoptive cell transfer. Nevertheless, conventional immunotherapies often involve immune-related adverse effects, such as liver dysfunction, hypophysitis, type I diabetes, and neuropathy. In an attempt to address these issues, polymeric nanomedicines are extensively investigated in recent years. In this review, recent advances in polymeric nanomedicines for cancer immunotherapy are highlighted and thoroughly discussed in terms of 1) antigen presentation, 2) activation of antigen-presenting cells and T cells, and 3) promotion of effector cells. Also, the future perspectives to develop ideal nanomedicines for cancer immunotherapy are provided.

Computational Modeling of the Crosstalk Between Macrophage Polarization and Tumor Cell Plasticity in the Tumor Microenvironment

Tumor microenvironments contain multiple cell types interacting among one another via different signaling pathways. Furthermore, both cancer cells and different immune cells can display phenotypic plasticity in response to these communicating signals, thereby leading to complex spatiotemporal patterns that can impact therapeutic response. Here, we investigate the crosstalk between cancer cells and macrophages in a tumor microenvironment through in silico (computational) co-culture models. In particular, we investigate how macrophages of different polarization (M₁ vs. M₂) can interact with epithelial-mesenchymal plasticity of cancer cells, and conversely, how cancer cells exhibiting different phenotypes (epithelial vs. mesenchymal) can influence the polarization of macrophages. Based on interactions documented in the literature, an interaction network of cancer cells and macrophages is constructed. The steady states of the network are then analyzed. Various interactions were removed or added into the constructed-network to test the functions of those interactions. Also, parameters in the mathematical models were varied to explore their effects on the steady states of the network. In general, the interactions between cancer cells and macrophages can give rise to multiple stable steady-states for a given set of parameters and each steady state is stable against perturbations. Importantly, we show that the system can often reach one type of stable steady states where cancer cells go extinct. Our results may help inform efficient therapeutic strategies.

Recent advances in nanomaterial-based synergistic combination cancer immunotherapy

This review aims to summarize various synergistic combination cancer immunotherapy strategies based on nanomaterials.

Engineering Nanoparticles for Targeted Remodeling of the Tumor Microenvironment to Improve Cancer Immunotherapy

Owing to the fast-paced growth and cross-infiltration of oncology, immunology and molecular biology, tumor immunotherapy technology represented by immune checkpoint blockade and chimeric antigen receptor (CAR) T cell therapy has lately made remarkable advancements. In comparison with traditional chemotherapy, immunotherapy has the potential to elicit a stronger sustained antitumor immune response in those patients who have advanced malignant malignancies. In spite of the advancements made, a significant number of clinical research works have validated that an extensive proportion of cancer patients still manifest insensitivity to immunotherapy, primarily because of the immunomodulatory interactions between tumor cells and the immunosuppressive tumor microenvironment (TME), together mediating the immune tolerance of tumors and accordingly impacting the positive response to immunotherapy. The intricate immunosuppressive networks formed by stromal cells, inflammatory cells, vasculature, extracellular matrix (ECM), and their secreted cytokines in the TME, play a pivotal role in tumor immune escape. Specific blocking of inhibition pathways in the TME is expected to effectively prevent immune escape and tolerance of tumor cells in addition to their metastasis, accordingly improving the antitumor immune response at various phases of tumor growth. Emerging nanoscale targeted drug carriers truly suit this specific requirement due to their specificity, biocompatibility, and convenience of production. This review emphasizes recent attempts to remodel the tumor immune microenvironment using novel nanoparticles, which include specifically eliminating immunosuppressive cells, reprogramming immune regulatory cells, promoting inflammatory cytokines and blocking immune checkpoints. Targeted remodeling of the immunosuppressive TME using well-designed and fabricated nanoparticles provides a promising strategy for improving the effectiveness of current immunotherapy and is greatly significant.

Molecular Repolarisation of Tumour-Associated Macrophages

The tumour microenvironment (TME) is composed of extracellular matrix and non-mutated cells supporting tumour growth and development. Tumour-associated macrophages (TAMs) are among the most abundant immune cells in the TME and are responsible for the onset of a smouldering inflammation. TAMs play a pivotal role in oncogenic processes as tumour proliferation, angiogenesis and metastasis, and they provide a barrier against the cytotoxic effector function of T lymphocytes and natural killer (NK) cells. However, TAMs are highly plastic cells that can adopt either pro- or anti-inflammatory roles in response to environmental cues. Consequently, TAMs represent an attractive target to recalibrate immune responses in the TME. Initial TAM-targeted strategies, such as macrophage depletion or disruption of TAM recruitment, have shown beneficial effects in preclinical models and clinical trials. Alternatively, reprogramming TAMs towards a proinflammatory and tumouricidal phenotype has become an attractive strategy in immunotherapy. This work summarises the molecular wheelwork of macrophage biology and presents an overview of molecular strategies to repolarise TAMs in immunotherapy.

Polymeric micro- and nanoparticles for immune modulation

New advances in biomaterial-based approaches to modulate the immune system are being applied to treat cancer, infectious diseases, and autoimmunity. Particulate systems are especially well-suited to deliver immunomodulatory factors to immune cells since their small size allows them to engage cell surface receptors or deliver cargo intracellularly after internalization. Biodegradable polymeric particles are a particularly versatile platform for the delivery of signals to the immune system because they can be easily surface-modified to target specific receptors and engineered to release encapsulated cargo in a precise, sustained manner. Micro- and nanoscale systems have been used to deliver a variety of therapeutic agents including monoclonal antibodies, peptides, and small molecule drugs that function to activate the immune system against cancer or infectious disease, or suppress the immune system to combat autoimmune diseases and transplant rejection. This review provides an overview of recent advances in the development of polymeric micro- and nanoparticulate systems for the presentation and delivery of immunomodulatory agents targeted to a variety of immune cell types including APCs, T cells, B cells, and NK cells.

Inhaled nanomaterials and the respiratory microbiome: clinical, immunological and toxicological perspectives

Our development and usage of engineered nanomaterials has grown exponentially despite concerns about their unfavourable cardiorespiratory consequence, one that parallels ambient ultrafine particle exposure from vehicle emissions. Most research in the field has so far focused on airway inflammation in response to nanoparticle inhalation, however, little is known about nanoparticle-microbiome interaction in the human airway and the environment. Emerging evidence illustrates that the airway, even in its healthy state, is not sterile. The resident human airway microbiome is further altered in chronic inflammatory respiratory disease however little is known about the impact of nanoparticle inhalation on this airway microbiome. The composition of the airway microbiome, which is involved in the development and progression of respiratory disease is dynamic, adding further complexity to understanding microbiota-host interaction in the lung, particularly in the context of nanoparticle exposure. This article reviews the size-dependent properties of nanomaterials, their body deposition after inhalation and factors that influence their fate. We evaluate what is currently known about nanoparticle-microbiome interactions in the human airway and summarise the known clinical, immunological and toxicological consequences of this relationship. While associations between inhaled ambient ultrafine particles and host immune-inflammatory response are known, the airway and environmental microbiomes likely act as intermediaries and facilitate individual susceptibility to inhaled nanoparticles and toxicants. Characterising the precise interaction between the environment and airway microbiomes, inhaled nanoparticles and the host immune system is therefore critical and will provide insight into mechanisms promoting nanoparticle induced airway damage.

Carbon-Based Nanomaterials for Cancer Therapy via Targeting Tumor Microenvironment

Cancer remains one of the major health problems all over the world and conventional therapeutic approaches have failed to attain an effective cure. Tumor microenvironments (TME) present a unique challenge in tumor therapy due to their complex structures and multiple components, which also serve as the soil for tumor growth, development, invasion, and migration. The complex TME includes immune cells, fibrous collagen structures, and tortuous blood vessels, in which conventional therapeutic approaches are rendered useless. State-of-the-art nanotechnologies have potential to cope with the threats of malignant tumors. With unique physiochemical properties, carbon nanomaterials (CNMs), including graphene, fullerenes, carbon nanotubes, and carbon quantum dots, offer opportunities to resolve the hurdles, by targeting not only cancer cells but also the TME. This review summarizes the progress about CNM-based cancer therapy strategies, which mainly focuses on both the treatment for cancer cells and TME-targeted modulation. In the last, the challenges for TME-based therapy via CNMs are discussed, which will be important in guiding current basic research to clinical translation in the future.

Biomaterial-assisted targeted modulation of immune cells in cancer treatment

The past decade has witnessed the accelerating development of immunotherapies for cancer treatment. Immune checkpoint blockade therapies and chimeric antigen receptor (CAR)-T cell therapies have demonstrated clinical efficacy against a variety of cancers. However, issues including life-threatening off-target side effects, long processing times, limited patient responses and high cost still limit the clinical utility of cancer immunotherapies. Biomaterial carriers of these therapies, though, enable one to troubleshoot the delivery issues, amplify immunomodulatory effects, integrate the synergistic effect of different molecules and, more importantly, home and manipulate immune cells in vivo. In this Review, we will analyse thus-far developed immunomaterials for targeted modulation of dendritic cells, T cells, tumour-associated macrophages, myeloid-derived suppressor cells, B cells and natural killer cells, and summarize the promises and challenges of cell-targeted immunomodulation for cancer treatment.

Nanomaterials for modulating innate immune cells in cancer immunotherapy

Cancer immunotherapy has been intensively investigated in both preclinical and clinical studies. Whereas chemotherapies use cytotoxic drugs to kill tumor cells, cancer immunotherapy is based on the ability of the immune system to fight cancer. Tumors are intimately associated with the immune system: they can suppress the immune response and/or control immune cells to support tumor growth. Immunotherapy has yielded promising results in clinical practice, but some patients show limited responses. This may reflect the complexities of the relationship between a tumor and the immune system. In an effort to improve the current immunotherapies, researchers have exploited nanomaterials in creating new strategies to cure tumors via modulation of the immune system in tumor tissues. Although extensive studies have examined the use of immune checkpoint-based immunotherapy, rather less work has focused on manipulating the innate immune cells. This review examines the recent approaches and challenges in the use of nanomaterials to modulate innate immune cells.

A multi-functional macrophage and tumor targeting gene delivery system for the regulation of macrophage polarity and reversal of cancer immunoresistance

To achieve effective tumor eradication using anti-tumor immunotherapies, a fusion peptide functionalized gene delivery system for macrophage and tumor targeting delivery of the plasmid DNA encoding the IL-12 gene (pDNA IL-12) was prepared for macrophage re-polarization as well as reversal of cancer immunosuppression. A fusion peptide containing the tuftsin sequence that can interact with Fc receptors and neuropilin-1, and hyaluronic acid (HA) that can interact with CD44 were introduced into the delivery system by self-assembly to form peptide/hyaluronic acid/protamine/CaCO3/DNA nanoparticles (PHNP) with both macrophage targeting and tumor targeting capabilities. PHNP provides an efficient immunoregulation on J774A.1 cells to shift the anti-inflammatory M2 phenotype to the anti-tumor M1 phenotype with enhanced secretion of pro-inflammatory cytokines and increased expression of M1 markers. Owing to the improved delivery efficiency caused by the fusion peptide and HA, the transfection mediated by multi-functional PHNP can up-regulate IL-12 as well as down-regulate IL-10 and IL-4 more effectively as compared with the nanoparticles without HA and/or peptide decoration. More importantly, the gene delivery system can also deliver pDNA IL-12 to targeted cancerous HeLa cells to realize the secretion of IL-12. PHNP not only enables tumorous cells to produce pDNA IL-12, but also down-regulates CD47 and up-regulate CD80 and HLA-1 in the malignant cells, indicating that the gene delivery system can effectively reverse tumor induced immunosuppression.

Chemopreventive Effects of Phytochemicals and Medicines on M1/M2 Polarized Macrophage Role in Inflammation-Related Diseases

Macrophages can polarize into two different states (M1 and M2), which play contrasting roles during pathogenesis or tissue damage. M1 polarized macrophages produce pro-inflammatory cytokines and mediators resulting in inflammation, while M2 macrophages have an anti-inflammatory effect. Secretion of appropriate cytokines and chemokines from macrophages can lead to the modification of the microenvironment for bridging innate and adaptive immune responses. Increasing evidence suggests that polarized macrophages are pivotal for disease progression, and the regulation of macrophage polarization may provide a new approach in therapeutic treatment of inflammation-related diseases, including cancer, obesity and metabolic diseases, fibrosis in organs, brain damage and neuron injuries, and colorectal disease. Polarized macrophages affect the microenvironment by secreting cytokines and chemokines while cytokines or mediators that are produced by resident cells or tissues may also influence macrophages behavior. The interplay of macrophages and other cells can affect disease progression, and therefore, understanding the activation of macrophages and the interaction between polarized macrophages and disease progression is imperative prior to taking therapeutic or preventive actions. Manipulation of macrophages can be an entry point for disease improvement, but the mechanism and potential must be understood. In this review, some advanced studies regarding the role of macrophages in different diseases, potential mechanisms involved, and intervention of drugs or phytochemicals, which are effective on macrophage polarization, will be discussed.

Repolarization of Tumor-Associated Macrophages in a Genetically Engineered Nonsmall Cell Lung Cancer Model by Intraperitoneal Administration of Hyaluronic Acid-Based Nanoparticles Encapsulating MicroRNA-125b

Tumor-associated macrophages (TAMs) acquire a pro-tumor (M2) phenotype, which promotes tumor growth, angiogenesis, and metastasis. Certain microRNAs (miRs), such as miR-125b, can reprogram TAMs into an antitumor/pro-inflammatory (M1) phenotype. Using CD44 targeting hyaluronic acid-poly(ethylenimine) (HA-PEI)-based nanoparticles encapsulating miR-125b, we have herein shown macrophage-specific delivery and transfection upon intraperitoneal (i.p.) administration. We have exploited the inherent ability of peritoneal macrophages to migrate toward the inflammation/injury and demonstrated that following intraperitoneal administration of HA-PEI nanoparticles, there is an accumulation of HA-PEI nanoparticles in the macrophage-ablated lung tissues of both naïve and KRAS/p53 double mutant genetically engineered (KP-GEM) nonsmall cell lung cancer (NSCLC) mouse model. Additionally, upon transfection with miR-125b, we observed a >6-fold increase in the M1 to M2 macrophage ratio and 300-fold increase in the iNOS (M1 marker)/Arg-1 (M2 marker) ratio in TAMs as compared to the untreated control group. The results of these studies show that i.p. administered macrophage-specific HA-PEI nanoparticles can successfully transfect TAMs in lung tissues of both naïve mice and a KP-GEM NSCLC mouse model. Successful TAM repolarization toward the M1 phenotype has significant implication in anticancer immunotherapy.

Immune Microenvironment in Glioblastoma Subtypes

Glioblastomas (GBMs) are the most common and aggressive primary brain tumors. Due to their malignant growth and invasion into the brain parenchyma coupled with resistance to therapy, GBMs are among the deadliest of all cancers. GBMs are highly heterogeneous at both the molecular and histological levels. Hallmark histological structures include pseudopalisading necrosis and microvascular proliferation. In addition to high levels of intratumoral heterogeneity, GBMs also exhibit high levels of inter-tumoral heterogeneity. The major non-neoplastic cell population in the GBM microenvironment includes cells of the innate immune system called tumor-associated macrophages (TAMs). Correlative data from the literature suggest that molecularly distinct GBM subtypes exhibit differences in their microenvironment. Data from mouse models of GBM suggest that genetic driver mutations can create unique microenvironments. Here, we review the origin, features, and functions of TAMs in distinct GBM subtypes. We also discuss their interactions with other immune cell constituents and discuss prospects of therapeutically targeting TAMs to increase the efficacy of T-cell functions.

Titanium dioxide nanoparticle stimulating pro-inflammatory responses in vitro and in vivo for inhibited cancer metastasis

AIMS

The interaction of engineered nanoparticles (NPs) with the immune system and the possibility of inflammation induction are of particularly interest. Titanium dioxide nanoparticles (TiO₂ NPs) are one of the most popular manufactured nanomaterials. In this study, we focused on the immune-modulatory effect of commercial P-25 TiO₂ NPs in vivo and in vitro and their crucial role in cancer metastasis.

MAIN METHODS

The female C57BL/6 mice were injected into abdominal cavity with PBS or P-25 TiO₂ to investigate the immune-modulatory function of P-25. And breast cancer cells were intravenously (i.v.) injected into mouse to establish the liver and lung cancer metastasis model. Peritoneal macrophage was used to investigate the macrophage polarization in vitro.

KEY FINDINGS

Results showed us that peritoneal macrophage exposed to P-25 TiO₂ NPs displayed activated M1 macrophage response, as evidenced by the increased mRNA expression of interleukin-1β (IL1β), IL6, TNFα, CCR7 and inducible nitric oxide synthase (iNOS). After exposure of TiO₂ NPs in vivo for 21 days, the body weights of mice decreased significantly, which were accompanied by an infiltration of immune cells in liver and spleen in 20 mg/kg BW treated group. Importantly, the production of pro-inflammatory cytokines in liver, spleen and the serum were amplified, which indicated the tissue and systemic inflammation induced by TiO₂ NPs. In addition, the activation of immune response induced by P-25 TiO₂ NPs was correlated with their ability to inhibit cancer metastasis.

SIGNIFICANCE

Our results delineated the stimulating pro-inflammatory response induced by P-25 TiO₂ NPs and their outcome in vivo for cancer metastasis.

The roles of macrophages and microglia in multiple sclerosis and experimental autoimmune encephalomyelitis

Multiple sclerosis (MS) is an autoimmune and neurodegenerative disorder characterized by chronic inflammation, demyelination, as well as axonal and neuronal loss in the central nervous system (CNS). Macrophages and microglia are important components of the innate immune system. They participate in the primary response to microorganisms and play a role in inflammatory responses, homeostasis, and tissue regeneration. In the initial phase of MS and experimental autoimmune encephalomyelitis (EAE), an animal model of MS, macrophages from peripheral tissues infiltrate into the CNS and, together with residential microglia, contribute to the pathogenesis of MS. In the early stages, microglia and macrophages are expressed as the M1 phenotype, which can release proinflammatory cytokines, leading to tissue damage in the CNS. However, in the later stage, the M2 phenotype, which is the phenotype that is associated with resolving inflammation and tissue repair, becomes predominant in the CNS. Therefore, it is hypothesized that the M1/M2 phenotype balance plays an important role in disease progression and that the transition from the proinflammatory M1 phenotype to the regulatory or anti-inflammatory M2 phenotype can lead to restoration of homeostasis and improved functional outcomes. This review of recent literature focuses on the discussion of the M1/M2 phenotypes of microglia and macrophages as well as their relevance in the pathophysiology and treatment of MS and EAE. Furthermore, the possibility of directing the polarization of microglia and macrophages toward the M2 phenotype as a therapeutic and preventative strategy for MS is discussed.

Immunoengineering with biomaterials for enhanced cancer immunotherapy

Cancer immunotherapy has recently shown dramatic clinical success inducing durable response in patients of a wide variety of malignancies. Further improvement of the clinical outcome with immune related cancer treatment requests more exquisite manipulation of a patient's immune system with increased immunity against diseases while mitigating the toxicities. To meet this challenge, biomaterials applied to immunoengineering are being developed to achieve tissue- and/or cell-specific immunomodulation and thus could potentially enhance both the efficacy and safety of current cancer immunotherapies. Here, we review the recent advancement in the field of immunoengineering using biomaterials and their applications in promoting different modalities of cancer immunotherapies, with focus on cell-, antibody-, immunomodulator-, and gene-based immune related treatments and their combinations with conventional therapies. Challenges and opportunities are discussed in applying biomaterials engineering strategies in the development of future cancer immunotherapies. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease Therapeutic Approaches and Drug Discovery > Emerging Technologies Implantable Materials and Surgical Technologies > Nanomaterials and Implants.

Reconfigurable Peptide Nanotherapeutics at Tumor Microenvironmental pH

Peptide nanomaterials have recently attracted considerable interest in the biomedical field. However, their poor bioavailability and less powerful therapeutic efficacy hamper their further applications. Herein, we discovered reconfigurable and activated nanotherapeutics in the tumor microenvironment. Two peptides, that is, a pH-responsive peptide HLAH and a matrix metalloprotease-2 (MMP2)-sensitive peptide with a poly(ethylene glycol) (PEG) terminal were conjugated onto the hydrophobic poly(β-thioester)s backbones to gain the copolymer P-S-H. The therapeutic activity of the HLAH peptide could be activated in tumors owing to its reconfiguration under microenvironmental pH. The resultant copolymers self-assembled into nanoparticles under physiological condition, with HLAH in cores protected by PEG shells. The moderate size (∼100 nm) and negative potential enabled the stable circulation of P-S-H in the bloodstream. Once arrived at the tumor site, the P-S-H nanoparticles were stimulated by overexpressed MMP2 and acidic pH, and subsequently the shedding of the PEG shell and protonation of the HLAH peptide induced the reassembly of nanoparticles, resulting in the formation of nanoparticles with activated cytotoxic peptides on the surface. In vivo experiments demonstrated that the reorganized nanoassembly contained three merits: (1) effective accumulation in the tumor site, (2) enhanced antitumor capacity, and (3) no obvious toxic effect at the treatment dose. This on-site reorganization strategy provides an avenue for developing high-performance peptide nanomaterials in cancer treatment.

Tumor-associated macrophages, potential targets for cancer treatment

The fact that various immune cells, including macrophages, can be found in tumor tissues has long been known. With the introduction of concept that macrophages differentiate into a classically or alternatively activated phenotype, the role of tumor-associated macrophages (TAMs) is now beginning to be elucidated. TAMs act as "protumoral macrophages", contributing to disease progression. As the relationship between TAMs and malignant tumors becomes clearer, TAMs are beginning to be seen as potential therapeutic targets in these cases. In this review, we will discuss how TAMs can be used as therapeutic targets of cancer in clinics.

Tailoring Biomaterials for Cancer Immunotherapy: Emerging Trends and Future Outlook

Cancer immunotherapy, as a paradigm shift in cancer treatment, has recently received tremendous attention. The active cancer vaccination, immune checkpoint blockage (ICB) and chimeric antigen receptor (CAR) for T-cell-based adoptive cell transfer are among these developments that have achieved a significant increase in patient survival in clinical trials. Despite these advancements, emerging research at the interdisciplinary interface of cancer biology, immunology, bioengineering, and materials science is important to further enhance the therapeutic benefits and reduce side effects. Here, an overview of the latest studies on engineering biomaterials for the enhancement of anticancer immunity is given, including the perspectives of delivery of immunomodulatory therapeutics, engineering immune cells, and constructing immune-modulating scaffolds. The opportunities and challenges in this field are also discussed.

Nanoparticles for modulating tumor microenvironment to improve drug delivery and tumor therapy

Tumor microenvironment (TME) plays a critical role in tumorigenesis, tumor invasion and metastasis. TME is composed of stroma, endothelial cells, pericytes, fibroblasts, smooth muscle cells, and immune cells, which is characterized by hypoxia, acidosis, and high interstitial fluid pressure. Due to the important role of TME, we firstly reviewed the composition of TME and discussed the impact of TME on tumor progression, drug and nanoparticle delivery. Next, we reviewed current strategies developed to modulate TME, including modulating tumor vasculature permeability, tumor associated macrophage phenotypes, tumor associated fibroblasts, tumor stroma components, tumor hypoxia, and multiple interventions simultaneously. Also, potential problems and future directions of TME modulation strategy have been discussed.

Tumor-associated macrophages: from basic research to clinical application

The fact that various immune cells, including macrophages, can be found in tumor tissues has long been known. With the introduction of concept that macrophages differentiate into a classically or alternatively activated phenotype, the role of tumor-associated macrophages (TAMs) is now beginning to be elucidated. TAMs act as “protumoral macrophages,” contributing to disease progression. TAMs can promote initiation and metastasis of tumor cells, inhibit antitumor immune responses mediated by T cells, and stimulate tumor angiogenesis and subsequently tumor progression. As the relationship between TAMs and malignant tumors becomes clearer, TAMs are beginning to be seen as potential biomarkers for diagnosis and prognosis of cancers, as well as therapeutic targets in these cases. In this review, we will discuss the origin, polarization, and role of TAMs in human malignant tumors, as well as how TAMs can be used as diagnostic and prognostic biomarkers and therapeutic targets of cancer in clinics.

Killing colon cancer cells through PCD pathways by a novel hyaluronic acid-modified shell-core nanoparticle loaded with RIP3 in combination with chloroquine

Due to extensive apoptosis defects and multidrug resistance, there is great interest regarding non-apoptotic programmed cell death (PCD) pathways, such as lysosomal-mediated programmed cell death (LM-PCD), necroptosis and autophagy. Because there is an intricate effector network among these PCD pathways, it is expected that they may act synergistically in cancer therapy. In this study, chloroquine (CQ) was found to significantly upregulate receptor-interacting protein kinase 3 (RIP3) expression, and RIP3 were involved in CQ-related autophagy. Overexpressed-eGFP-RIP3 co-localized with the selective autophagy receptor p62. mRIP3 overexpression in combination with CQ markedly increased the inhibition rate relative to that observed in the CQ-treatment group. Several experiments, including Hoechst staining, transmission electron microscopy (TEM) observation, the high-mobility group box 1 (HMGB1) release assay, Annexin V/PI staining and immunoblotting of proteins included in PCD pathways, verified that mRIP3 overexpression in combination with CQ induced lysosomal membrane permeabilization (LMP) and necroptosis of cancer cells, leading to cancer cell death. For tumor-targeted delivery, hyaluronic acid (HA)-modified, lipid-coated PLGA nanoparticles loaded with mRIP3-pDNA were prepared and characterized using a particle sizer, differential scanning calorimetry (DSC) and TEM. The nanoparticles exhibited ideal biocompatibility and good tumor-targeting efficiency, and the tumor inhibition rate of HA-Lip-PEI-mRIP3-PLGA-NPs + CQ was 80.2% in the CT26 mouse model. In this study, we attempted to treat tumors by inducing several alternative PCD pathways to shed light on the combination therapy of alternative PCD inducers.