Terminating the renewal of tumor-associated macrophages: A sialic acid-based targeted delivery strategy for cancer immunotherapy

The selection of animal models influences the assessment of anti-tumor efficacy: promising sialic acid-conjugate modified liposomes demonstrate remarkable therapeutic effects in diverse mouse strains

Mice as a crucial tool for preclinical assessment of antineoplastic agents. The impact of physiological differences among mouse strains on the in vivo efficacy of antitumor drugs, however, has been significantly overlooked. Mononuclear phagocyte system (MPS) is the major player in clearance in vivo, and differences in MPS among different strains may potentially impact the effectiveness of antitumor preparations. Therefore, in this study, we employed conventional liposomes (CL-EPI) and SA-ODA modified liposomes (SAL-EPI) as model preparations to investigate the comprehensive tumor therapeutic effects of CL-EPI and SAL-EPI in KM, BALB/c, and C57BL/6 tumor-bearing mice. The results demonstrated significant variability in the efficacy of CL-EPI for tumor treatment across different mouse strains. Therefore, we should pay attention to the selection of animal models in the study of antitumor agents. SAL-EPI effectively targeted tumor sites by binding to Siglec-1 on the surface of peripheral blood monocytes (PBMs), and achieved good therapeutic effect in different mouse strains with little difference in treatment. The SA modified preparation is therefore expected to achieve a favorable therapeutic effect in tumor patients with different immune states through PBMs delivery (Siglec-1 was expressed in both mice and humans), thereby possessing clinical translational value and promising development prospects.

The investigation on sialic acid-modified pectin nanoparticles loaded with oxymatrine for orally targeting and inhibiting the of ulcerative colitis

The aim of the study was to develop an oral targeting drug delivery system (OTDDS) of oxymatrine (OMT) to effectively treat ulcerative colitis (UC). The OTDDS of OMT (OMT/SA-NPs) was constructed with OMT, pectin, Ca2+, chitosan (CS) and sialic acid (SA). The obtained particles were characterized in terms of particle size, zeta potential, morphology, drug loading, encapsulation efficiency, drug release and stability. The average size of OMT/SA-NPs was 255.0 nm with a zeta potential of -12.4 mV. The loading content and encapsulation efficiency of OMT/SA-NPs were 14.65% and 84.83%, respectively. The particle size of OMT/SA-NPs changed slightly in the gastrointestinal tract. The nanoparticles can delivery most of the drug to the colon region. In vitro cell experiments showed that the SA-NPs had excellent biocompatibility and anti-inflammation, and the uptake of SA-NPs by RAW 264.7 cells was time and concentration-dependent. The conjugated SA can help the internalization of NPs into target cells. In vivo experiments showed that OMT/SA-NPs had a superior anti-inflammation effect and the effect of reducing UC, which was attributed to the delivery most of OMT to the colonic lumen, the specific targeting and retention in colitis site and the combined anti-inflammation of OMT and NPs.

A landscape of recent advances in lipid nanoparticles and their translational potential for the treatment of solid tumors

Lipid nanoparticles (LNPs) are biocompatible drug delivery systems that have found numerous applications in medicine. Their versatile nature enables the encapsulation and targeting of various types of medically relevant molecular cargo, including oligonucleotides, proteins, and small molecules for the treatment of diseases, such as cancer. Cancers that form solid tumors are particularly relevant for LNP-based therapeutics due to the enhanced permeation and retention effect that allows nanoparticles to accumulate within the tumor tissue. Additionally, LNPs can be formulated for both locoregional and systemic delivery depending on the tumor type and stage. To date, LNPs have been used extensively in the clinic to reduce systemic toxicity and improve outcomes in cancer patients by encapsulating chemotherapeutic drugs. Next-generation lipid nanoparticles are currently being developed to expand their use in gene therapy and immunotherapy, as well as to enable the co-encapsulation of multiple drugs in a single system. Other developments include the design of targeted LNPs to specific cells and tissues, and triggerable release systems to control cargo delivery at the tumor site. This review paper highlights recent developments in LNP drug delivery formulations and focuses on the treatment of solid tumors, while also discussing some of their current translational limitations and potential opportunities in the field.

Sialic acid-decorated liposomes enhance the anti-cancer efficacy of docetaxel in tumor-associated macrophages

Tumor-associated macrophages (TAMs) in the tumor microenvironment potentially enhance tumor growth and invasion through various mechanisms and are thus an essential factor in tumor immunity. The highly expressed siglec-1 receptors on the surfaces of TAMs are potential targets for cancer drug delivery systems. Sialic acid (SA) is a specific ligand for siglec-1. In this study, the sialic acid-polyethylene glycol conjugate (DSPE-PEG2000-SA) was synthesized to modify the surface of liposomes and target TAMs by interacting with the siglec-1 receptor. Three docetaxel (DTX)-loaded liposomes, conventional (DTX-CL), DSPE-PEG2000-coated (DTX-PL), and DSPE-PEG2000-SA-coated (DTX-SAPL) liposomes, were prepared, with a particle size of <100 nm, uniform polydispersity index (PDI) values, negative zeta potential, and % encapsulation efficiency (EE) exceeding 95 %. Liposomes showed high stability after 3 months of storage at 4 °C without significant changes in particle size, PDI, zeta potential, or % EE. DTX was released from liposomes according to the Weibull model, and DTX-SAPL exhibited more rapid drug release than other liposomes. In vitro studies demonstrated that DTX-SAPL liposome exhibited a higher uptake and cytotoxicity on RAW 264.7 cells (TAM model) and lower toxicity on NIH3T3 cells (normal cell model) than other formulations. The high cell uptake ability was demonstrated by the role of the SA-SA receptor. Biodistribution studies indicated a high tumor accumulation of surface-modified liposomal formulations, particularly SA-modified liposomes, showing high signal accumulation at the tumor periphery, where TAMs were highly concentrated. Ex vivo imaging showed a significantly higher accumulation of SA-modified liposomes in the tumor, kidney, and heart than conventional liposomes. In the anti-cancer efficacy study, DTX-SAPL liposomes showed effective inhibition of tumor growth and relatively low systemic toxicity, as evidenced by the tumor volume, tumor weight, body weight values, and histopathological analysis. Therefore, DSPE-PEG2000-SA-coated liposomes could be promising carriers for DTX delivery targeting TAMs in cancer therapy.

Sialylation: An alternative to designing long-acting and targeted drug delivery system

Long-acting and specific targeting are two important properties of excellent drug delivery systems. Currently, the long-acting strategies based on polyethylene glycol (PEG) are controversial, and PEGylation is incapable of simultaneously possessing targeting ability. Thus, it is crucial to identify and develop approaches to produce long-acting and targeted drug delivery systems. Sialic acid (SA) is an endogenous, negatively charged, nine-carbon monosaccharide. SA not only mediates immune escape in the body but also binds to numerous disease related targets. This suggests a potential strategy, namely "sialylation," for preparing long-acting and targeted drug delivery systems. This review focuses on the application status of SA-based long-acting and targeted agents as a reference for subsequent research.

Tumor-associated macrophages in nanomaterial-based anti-tumor therapy: as target spots or delivery platforms

Targeting tumor-associated macrophages (TAMs) has emerged as a promising approach in cancer therapy. This article provides a comprehensive review of recent advancements in the field of nanomedicines targeting TAMs. According to the crucial role of TAMs in tumor progression, strategies to inhibit macrophage recruitment, suppress TAM survival, and transform TAM phenotypes are discussed as potential therapeutic avenues. To enhance the targeting capacity of nanomedicines, various approaches such as the use of ligands, immunoglobulins, and short peptides are explored. The utilization of live programmed macrophages, macrophage cell membrane-coated nanoparticles and macrophage-derived extracellular vesicles as drug delivery platforms is also highlighted, offering improved biocompatibility and prolonged circulation time. However, challenges remain in achieving precise targeting and controlled drug release. The heterogeneity of TAMs and the variability of surface markers pose hurdles in achieving specific recognition. Furthermore, the safety and clinical applicability of these nanomedicines requires further investigation. In conclusion, nanomedicines targeting TAMs hold great promise in cancer therapy, offering enhanced specificity and reduced side effects. Addressing the existing limitations and expanding our understanding of TAM biology will pave the way for the successful translation of these nano-therapies into clinical practice.

Targeting of TAMs with freeze-dried monosialotetrahexosylganglioside and sialic acid-octadecylamine co-modified liposomes remodels the tumor microenvironment and enhances anti-tumor activity

Although anti-tumor strategies targeting tumor-associated immune cells were being rapidly developed, the preparations were usually limited in targeting efficiency. To overcome this barrier, this study reported a novel sialic acid-octadecylamine (SA-ODA) and monosialotetrahexosylganglioside (GM1) co-modified epirubicin liposomes (5-5-SAGL-EPI), which improved tumor-targeting ability through the active targeting of tumor-associated macrophages (TAMs) by SA-ODA and the long circulation of GM1. Thus, we evaluated 5-5-SAGL-EPI in vitro and in vivo. Analysis of cellular uptake by RAW264.7 cells using flow cytometry and confocal microscopy showed a higher rate of cellular uptake for 5-5-SAGL-EPI than for the common liposomes (CL-EPI). In pharmacokinetic studies using Wistar rats, compared to CL-EPI, 5-5-SAGL-EPI showed a higher circulation time in vivo. Tissue distribution studies in Kunming mice bearing S180 tumors revealed increased distribution of 5-5-SAGL-EPI in tumor tissues compared with liposomes modified with single ligands (SA-ODA [5-SAL-EPI] or GM1 [5-GL-EPI]). In vivo anti-tumor experiments using the S180 tumor-bearing mice revealed a high tumor inhibition rate and low toxicity for 5-5-SAGL-EPI. Moreover, freeze-dried 5-5-SAGL-EPI had good storage stability, and the anti-tumor effect was comparable to that before freeze-drying. Overall, 5-5-SAGL-EPI exhibited excellent anti-tumor effects before and after lyophilization.

A potential platform of combining sialic acid derivative-modified paclitaxel cationic liposomes with antibody-drug conjugates inspires robust tumor-specific immunological memory in solid tumors

The recent approvals for antibody-drug conjugates (ADCs) in multiple malignancies in the past few years have fueled the ongoing development of this class of drug. However, the limitation of ADCs is selectivity toward cancer cells especially overexpressing the antigen of interest. To broaden the anti-cancer spectrum of ADCs, combinatorial strategies of ADCs with chemotherapy have become a central focus of the current preclinical and clinical research. Here, we used the microtubule stabilizer paclitaxel and enfortumab vedotin-ejfv (EV), an ADC carrying the microtubule inhibitor payload monomethyl auristatin E (MMAE), for co-administration under the consideration of their mechanism of action associated with microtubules. We designed a sialic acid-cholesterol (SA-CH) conjugate-modified cationic liposome platform loaded with PTX (PTX-SAL) for efficiently targeting tumor-associated immune cells. Compared with monotherapy, PTX-SAL-mediated combination therapy with ADCs significantly inhibited S180 tumor growth in mice, with complete tumor regression occurring. The formation of a durable tumor-specific immunological memory response in mice that experienced complete tumor regression was assessed by secondary tumor cell rechallenge, and the production of memory T cells in the spleen was detected as related to the increased CD4⁺T memory cells and the enhanced serum IFN-γ. All our preliminary results throw light on the tremendous application potential for the application of this combination therapy regimen capable of mounting a durable immune response and stimulating a robust T cell-mediated tumor-specific immunological memory.

Liposomal Doxorubicin: the Sphingomyelin/Cholesterol System Significantly Enhances the Antitumor Efficacy of Doxorubicin

Doxorubicin (DOX) has a cytotoxic effect on many tumor cells; however, its clinical application is limited owing to its strong side effects. Although Doxil® reduces the cardiotoxicity of free DOX, it has also introduced a new dose-limiting toxicity. In a previous study, a sialic acid-cholesterol conjugate (SA-CH) was synthesized and modified onto the surface of DOX-loaded liposomes to target tumor-associated macrophages (TAMs), further improving the efficacy of DOX-loaded liposomes over that of Doxil®. Meanwhile, the good retention characteristics and promising antitumor ability of sphingomyelin/cholesterol (SM/CH) system for water-soluble drugs have attracted wide attention. Therefore, we aimed to use SA-CH as the target and hydrogenated soybean phosphatidylcholine (HSPC) or egg sphingomyelin (ESM) as the membrane material to develop a more stable DOX-loaded liposome with stronger antitumor activity. The liposomes were evaluated for particle size, polydispersity index, zeta potential, entrapment efficiency, in vitro release, long-term storage, cytotoxicity, cellular uptake, pharmacokinetics, tumor targetability, and in vivo antitumor activity. In the liposomes prepared using HSPC/CH, sialic acid (SA) modification considerably increased the accumulation of DOX-loaded liposomes in the tumor, thus exerting a better antitumor effect. However, SA modification in DOX-ESL (SA-CH-modified DOX-loaded liposomes prepared by ESM/CH) destroyed the strong retention effect of the ESM/CH system on DOX, resulting in a reduced antitumor effect. Notably, DOX-ECL (DOX-loaded liposome prepared by ESM/CH) had the optimal storage stability, lowest toxicity, and optimal antitumor effect due to better drug retention properties. Thus, the ESM/CH liposome of DOX is a potential drug delivery system. Sketch of the effect of two DOX-loaded liposomes with hydrogenated soybean phospholipid (HSPC) and egg sphingomyelin (ESM) as lipid membrane material and surface-modified SA derivative on tumor growth inhibition.

Sialic acid-mediated photochemotherapy enhances infiltration of CD8+ T cells from tumor-draining lymph nodes into tumors of immunosenescent mice

Immunoscenescence plays a key role in the initiation and development of tumors. Furthermore, immunoscenescence also impacts drug delivery and cancer therapeutic efficacy. To reduce the impact of immunosenescence on anti-tumor therapy, this experimental plan aimed to use neutrophils with tumor tropism properties to deliver sialic acid (SA)-modified liposomes into the tumor, kill tumor cells via SA-mediated photochemotherapy, enhance infiltration of neutrophils into the tumor, induce immunogenic death of tumor cells with chemotherapy, enhance infiltration of CD8⁺ T cells into the tumor-draining lymph nodes and tumors of immunosenescent mice, and achieve SA-mediated photochemotherapy. We found that CD8⁺ T cell and neutrophil levels in 16-month-old mice were significantly lower than those in 2- and 8-month-old mice; 16-month-old mice exhibited immunosenescence. The anti-tumor efficacy of SA-mediated non-photochemotherapy declined in 16-month-old mice, and tumors recurred after scabbing. SA-mediated photochemotherapy enhanced tumor infiltration by CD8⁺ T cells and neutrophils, induced crusting and regression of tumors in 8-month-old mice, inhibited metastasis and recurrence of tumors and eliminated the immunosenescence-induced decline in antitumor therapeutic efficacy in 16-month-old mice via the light-heat-chemical-immunity conversion.

An Application of Tumor-Associated Macrophages as Immunotherapy Targets: Sialic Acid-Modified EPI-Loaded Liposomes Inhibit Breast Cancer Metastasis

Breast cancer metastasis is an important cause of death in patients with breast cancer and is closely related to circulating tumor cells (CTCs) and the metastatic microenvironment. As the most infiltrating immune cells in the tumor microenvironment (TME), tumor-associated macrophages (TAMs), which highly express sialic acid (SA) receptor (Siglec-1), are closely linked to tumor progression and metastasis. Furthermore, the surface of CTCs also highly expressed receptor (Selectin) for SA. A targeting ligand (SA-CH), composed of SA and cholesterol, was synthesized and modified on the surface of epirubicin (EPI)-loaded liposomes (EPI-SL) as an effective targeting delivery system. Liposomes were evaluated for characteristics, stability, in vitro release, cytotoxicity, cellular uptake, pharmacokinetics, tumor targeting, and pharmacodynamics. In vivo and in vitro experiments showed that EPI-SL enhanced EPI uptake by TAMs. In addition, cellular experiments showed that EPI-SL could also enhance the uptake of EPI by 4T1 cells, resulting in cytotoxicity second only to that of EPI solution. Pharmacodynamic experiments have shown that EPI-SL has optimal tumor inhibition with minimal toxicity, which can be ascribed to the fact that EPI-SL can deliver drugs to tumor based on TAMs and regulate TME through the depletion of TAMs. Our study demonstrated the significant potential of SA-modified liposomes in antitumor metastasis. Schematic diagram of the role of SA-CH modified EPI-loaded liposomes in the model of breast cancer metastasis.

Antitumor Immunotherapy of Sialic Acid and/or GM1 Modified Coenzyme Q10 Submicron Emulsion

Immunotherapy is a novel therapeutic approach for controlling and killing tumor cells by stimulating or reconstituting the immune system, among which T cells serve as immune targets. Herein, we used coenzyme Q10 (CoQ10), which has both immune activation and avoids adverse reactions, as a model drug and developed four CoQ10 submicron emulsions modified with sialic acid (SA) and/or monosialotetrahexosyl ganglioside (GM1). On the one hand, SA interacts with L-selectins on the surface of T cells after entering the circulatory system, leading to activation of T cells and enhancement of antitumor immune responses. On the other hand, owing to its immune camouflage, GM1 can prolong the circulation time of the preparation in the body, thereby increasing the accumulation of the drug at the tumor site. In vitro and in vivo experiments showed that SA-modified preparations exhibited stronger immune activation and inhibition of tumor proliferation. Pharmacokinetic experiments showed that GM1-modified preparations have longer circulation times in vivo. However, SA and GM1 co-modification did not produce a synergistic effect on the preparation. In conclusion, the SA-modified CoQ10 submicron emulsion (Q10-SE) showed optimal antitumor efficacy when administered at a medium dose (6 mg CoQ10 kg^-1). In this study, the submicron emulsion model was used as a carrier, and the tumor-bearing mice were used as animal models. In addition, CoQ10 submicron emulsion was modified with SA-CH with active targeting function and/or GM1 with long-circulation function to explore the antitumor effects of different doses of CoQ10 submicron emulsion, and to screen the best tumor immunotherapy formulations of CoQ10.

Neutrophils as emerging immunotherapeutic targets: Indirect treatment of tumors by regulating the tumor immune environment based on a sialic acid derivative-modified nanocomplex platform

Tumor cells are dependent on their microenvironment; thus, targeting the non-cancerous components surrounding the tumor may be beneficial. Neutrophils are important inflammatory cells in the tumor microenvironment that significantly affect tumor cell proliferation, metastasis, and immune regulation. Targeted regulation of tumor-associated neutrophil-related pathways is expected to become a new therapeutic approach. Colchicine compounds are powerful anti-inflammatory drugs that strongly inhibit the chemotaxis of neutrophils to the inflammatory site. We attempted to achieve anticancer effects by utilizing its ability to inhibit neutrophil recruitment rather than killing tumor cells. As such drugs are likely to cause non-specific damages due to the lack of selectivity, we synthesized and used sialic acid and cholesterol derivatives (SA-CH) for surface modification of the newly synthesized low-toxic colchicine derivative (BCS) nanocomposite to improve neutrophil targeting. In vivo and in vitro experiments have shown that SA-CH-modified BCS preparations are effectively absorbed by neutrophils, inhibit cell migration, reduce infiltration of tumor-associated neutrophils, enhance T lymphocyte function, and exhibit good anti-S180 early tumor effect. In addition, in a triple-negative breast cancer model, the agent could strongly inhibit tumor metastasis to the lungs.

Anticancer nanomedicines harnessing tumor microenvironmental components

INTRODUCTION

Small-molecular drugs are extensively used in cancer therapy, while they have issues of nonspecific distribution and consequent side effects. Nanomedicines that incorporate chemotherapeutic drugs have been developed to enhance the therapeutic efficacy of these drugs and reduce their side effects. One of the promising strategies is to prepare nanomedicines by harnessing the unique tumor microenvironment (TME).

AREAS COVERED

The TME contains numerous cell types that specifically express specific antibodies on the surface including tumor vascular endothelial cells, tumor-associated adipocytes, tumor-associated fibroblasts, tumor-associated immune cells and cancer stem cells. The physicochemical environment is characterized with a low pH, hypoxia, and a high redox potential resulting from tumor-specific metabolism. The intelligent nanomedicines can be categorized into two groups: the first group which is rapidly responsive to extracellular chemical/biological factors in the TME and the second one which actively and/or specifically targets cellular components in the TME.

EXPERT OPINION

In this paper, we review recent progress of nanomedicines by harnessing the TME and illustrate the principles and advantages of different strategies for designing nanomedicines, which are of great significance for exploring novel nanomedicines or translating current nanomedicines into clinical practice. We will discuss the challenges and prospects of preparing nanomedicines to utilize or alter the TME for achieving effective, safe anticancer treatment.

Serum Linkage-Specific Sialylation Changes Are Potential Biomarkers for Monitoring and Predicting the Recurrence of Papillary Thyroid Cancer Following Thyroidectomy

BACKGROUND

Although papillary thyroid cancer (PTC) could remain indolent, the recurrence rates after thyroidectomy are approximately 20%. There are currently no accurate serum biomarkers that can monitor and predict recurrence of PTC after thyroidectomy. This study aimed to explore novel serum biomarkers that are relevant to the monitoring and prediction of recurrence in PTC using N-glycomics.

METHODS

A high-throughput quantitative strategy based on matrix-assisted laser desorption/ionization time-of-flight mass spectrometry was used to obtain serum protein N-glycomes of well-differentiated PTC, postoperative surveillance (PS), postoperative recurrence (PR), and matched healthy controls (HC) including linkage-specific sialylation information.

RESULTS

Serum N-glycan traits were found to differ among PTC, PS, PR, and HC. The differentially expressed N-glycan traits consisting of sixteen directly detected glycan traits and seven derived glycan traits indicated the response to surgical resection therapy and the potential for monitoring the PTC. Two glycan traits representing the levels of linkage-specific sialylation (H4N3F1L1 and H4N6F1E1) which were down-regulated in PS and up-regulated in PR showed high potential as biomarkers for predicting the recurrence after thyroidectomy.

CONCLUSIONS

To the best of our knowledge, this study provides comprehensive evaluations of the serum N-glycomic changes in patients with PS or PR for the first time. Several candidate serum N-glycan biomarkers including the linkage-specific sialylation have been determined, some of which have potential in the prediction of recurrence in PTC, and others of which can help to explore and monitor the response to initial surgical resection therapy. The findings enhanced the comprehension of PTC.

Siglecs as Therapeutic Targets in Cancer

Hypersialylation is a common post-translational modification of protein and lipids found on cancer cell surfaces, which participate in cell-cell interactions and in the regulation of immune responses. Sialic acids are a family of nine-carbon α-keto acids found at the outermost ends of glycans attached to cell surfaces. Given their locations on cell surfaces, tumor cells aberrantly overexpress sialic acids, which are recognized by Siglec receptors found on immune cells to mediate broad immunomodulatory signaling. Enhanced sialylation exposed on cancer cell surfaces is exemplified as "self-associated molecular pattern" (SAMP), which tricks Siglec receptors found on leukocytes to greatly down-regulate immune responsiveness, leading to tumor growth. In this review, we focused on all 15 human Siglecs (including Siglec XII), many of which still remain understudied. We also highlighted strategies that disrupt the course of Siglec-sialic acid interactions, such as antibody-based therapies and sialic acid mimetics leading to tumor cell depletion. Herein, we introduced the central roles of Siglecs in mediating pro-tumor immunity and discussed strategies that target these receptors, which could benefit improved cancer immunotherapy.

Sialic acid conjugate-modified liposomes enable tumor homing of epirubicin via neutrophil/monocyte infiltration for tumor therapy

Neutrophils and monocytes (N/Ms) are potential candidates for the delivery of therapeutic agents to the tumor microenvironment (TME) because of their tumor-accumulating nature. L-selectin and Siglec-1, receptors for sialic acid (SA), are highly expressed in circulating neutrophils and monocytes, respectively, in tumor-bearing mice, and N/Ms are recruited to tumors in response to inflammatory cytokines secreted by the TME, promoting tumor growth and invasion. Therefore, we constructed a drug delivery nano-platform using N/Ms as vehicles. SA-stearic acid conjugate was synthesized and utilized to modify epirubicin-loaded liposomes (EPI-SL) for enhanced endocytosis of liposomes by circulating N/Ms. Cellular uptake studies showed that SA modification improved the accumulation of EPI in N/Ms and did not alter the inherent chemotaxis of N/Ms. In tumor-bearing mice, EPI-SL significantly improved the tumor-targeting efficiency and therapeutic efficacy of EPI compared to other preparations and even eradicated tumors because of the tumor-accumulating and inhibitory effects of N/Ms containing EPI-SL. Our research showed, for the first time, that as an N/M-based drug delivery platform, EPI-SL remedied the limited tumor targeting in the conventional EPR effect-based treatment strategy, contributing to the exploitation of a new drug delivery platform for cancer treatment. STATEMENT OF SIGNIFICANCE: Tumor-associated neutrophils (TANs) and macrophages (TAMs) are closely associated with tumor growth and invasion, and therefore the development of therapeutic strategies targeting TANs and TAMs is crucial for tumor treatment. Given that most TANs and TAMs are derived from peripheral blood neutrophils and monocytes (N/Ms), respectively, we synthesized sialic acid-stearic acid conjugates that specifically bind N/Ms for the surface modification of liposomal epirubicin (EPI-SL). The N/Ms loaded with EPI-SL maintained their inherent chemotaxis toward the tumor. Additionally, EPI-SL significantly improved the survival of tumor-bearing mice and even eradicated tumors. These findings suggested that EPI-SL has substantial potential for clinical application by compensating for the previous low efficacy of ex vivo transformed cell infusion and improving the tumor-targeting efficiency.

Dual targeting single arrow: Neutrophil-targeted sialic acid-modified nanoplatform for treating comorbid tumors and rheumatoid arthritis

Clinically, rheumatoid arthritis (RA) is frequently accompanied by multi-system diseases. Among them, the incidence of comorbid tumors in RA is relatively high, resulting in a gradual increase in mortality; this poses a considerable challenge to clinical treatment. To date, no effective treatment plan for simultaneous tumor and RA therapy is available. Accordingly, we reported a sialic acid-modified doxorubicin hydrochloride liposome (DOX-SAL) that targets peripheral blood neutrophils (PBNs), which play an important role in tumors and RA. Furthermore, the prepared liposome induced PBN apoptosis by binding to L-selectin, which is highly expressed on the surface of PBNs activated by inflammation. This liposome, in turn, reduced the accumulation of inflammatory neutrophils at the disease site. In the first successfully established mouse model of RA comorbidity, induced by employing S180 sarcoma cells and collagen, DOX-SAL effectively inhibited tumor growth while simultaneously alleviating systemic RA symptoms without side effects. Additionally, the animals demonstrated adequate growth during the 48 days of treatment. This treatment strategy encompasses the best of both worlds, breaking the deadlock that tumors and RA cannot be effectively treated in parallel, highlighting a new concept and reference for the clinical treatment of comorbid tumors and RA.

Tackling TAMs for Cancer Immunotherapy: It's Nano Time

The tumor microenvironment (TME) is a highly complex environment that surrounds tumors. Interactions between cancer cells/non-cancerous cells and cells/non-cell components in the TME support tumor initiation, development, and metastasis. Of the cell types in the TME, tumor-associated macrophages (TAMs) have gained attention owing to their crucial roles in supporting tumors and conferring therapy resistance. Recent developments in nanotechnology raise opportunities for the application of nano targeted drug-delivery systems (Nano-TDDS) in cancer therapy. We focus our discussion on current knowledge of TAMs, and describe recent examples of Nano-TDDS-based TAM modulation, highlighting strategies to overcome in vivo delivery barriers associated with the TME and their potential for clinical translation.

Sialic acid-conjugate modified doxorubicin nanoplatform for treating neutrophil-related inflammation

Neutrophils, the most abundant leukocytes in human peripheral blood, are important effector cells that mediate the inflammatory response. During neutrophil dysfunction, excessive activation and uncontrolled infiltration are the core processes in the progression of inflammation-related diseases, including severe coronavirus disease-19 (COVID-19), sepsis, etc. Herein, we used sialic acid-modified liposomal doxorubicin (DOX-SAL) to selectively target inflammatory neutrophils in the peripheral blood and deliver DOX intracellularly, inducing neutrophil apoptosis, blocking neutrophil migration, and inhibiting the inflammatory response. Strong selectivity resulted from the specific affinity between SA and L-selectin, which is highly expressed on inflammatory neutrophil membranes. In inflammation models of acute lung inflammation/injury (ALI), sepsis, and rheumatoid arthritis (RA), DOX-SAL suppressed the inflammatory response, increased the survival of mice, and delayed disease progression, respectively. Moreover, DOX-SAL restored immune homeostasis in the body, without side effects. We have presented a targeted nanocarrier drug delivery system that can block the recruitment of inflammatory neutrophils, enabling specific inhibition of the core disease process and the potential to treat multiple diseases with a single drug. This represents a revolutionary treatment strategy for inflammatory diseases caused by inappropriate neutrophil activation.

Sequential administration of sialic acid-modified liposomes as carriers for epirubicin and zoledronate elicit stronger antitumor effects with reduced toxicity

Combined administration of drugs can improve efficacy and reduce toxicity; therefore, this combination approach has become a routine method in cancer therapy. The main combination regimens are sequential, mixed (also termed "cocktail"), and co-loaded; however, other combinations, such as administration of synergistic drugs and the use of formulations with different mechanisms of action, may exert better therapeutic effects. Tumor-associated macrophages (TAMs) play functional roles throughout tumor progression and exhibit characteristic phenotypic plasticity. Sialic acid (SA)-modified epirubicin liposomes (S-E-L) and SA-modified zoledronate liposomes (S-Z-L) administered separately kill TAMs, reverse their phenotype, and achieve antitumor effects. In this study, we examined the effects of a two-treatment combination for drug delivery, using sequential, mixed, and co-loaded drug delivery. We found that therapeutic effects differed between administration methods: mixed administration of S-E-L and S-Z-L, co-loaded administration of SA-modified liposomes (S-ZE-C), and sequential administration of S-E-L injected 24 h after S-Z-L did not inhibit tumor growth; however, sequential administration of S-Z-L injected 24 h after S-E-L resulted in no tumor growth, no toxicity to noncancerous tissue, and no death of mice, and exhibited 25% tumor shedding. Thus, our results thus encourage the further development of combined therapies for nanomedicines based on the mechanisms investigated here.

Function of Macrophages in Disease: Current Understanding on Molecular Mechanisms

Tissue-resident macrophages (TRMs) are heterogeneous populations originating either from monocytes or embryonic progenitors, and distribute in lymphoid and non-lymphoid tissues. TRMs play diverse roles in many physiological processes, including metabolic function, clearance of cellular debris, and tissue remodeling and defense. Macrophages can be polarized to different functional phenotypes depending on their origin and tissue microenvironment. Specific macrophage subpopulations are associated with disease progression. In studies of fate-mapping and single-cell RNA sequencing methodologies, several critical molecules have been identified to induce the change of macrophage function. These molecules are potential markers for diagnosis and selective targets for novel macrophage-mediated treatment. In this review, we discuss some of the recent findings regarding less-known molecules and new functions of well-known molecules. Understanding the mechanisms of these molecules in macrophages has the potential to yield new macrophage-mediated treatments or diagnostic approaches to disease.

Siglec and anti-Siglec therapies

Siglecs (sialic acid-binding immunoglobulin-like lectins) are a family of receptors that bind sialic acids in specific linkages on glycoproteins and glycolipids. Siglecs play roles in immune signalling and exhibit cell-type specific expression and endocytic properties. Recent studies suggest that Siglecs are likely to function as immune checkpoints that regulate responses in cancers and inflammatory diseases. In this review, we discuss strategies to target the Siglec-sialic acid axis in human diseases, particularly cancer, and the possibility of exploiting them for therapeutic intervention.

Sialic Acid Conjugate-Modified Liposomal Dexamethasone Palmitate Targeting Neutrophils for Rheumatoid Arthritis Therapy: Influence of Particle Size

Many anti-inflammatory therapies targeting neutrophils have been developed so far. A sialic acid (SA)-modified liposomal (SAL) formulation, based on the high expression of L-selectin in peripheral blood neutrophils (PBNs) and SA as its targeting ligand, has proved to be an effective neutrophil-mediated drug delivery system targeting rheumatoid arthritis (RA). The objective of this study was to investigate the influence of particle size of drug-carrying SALs transported and delivered by neutrophils on their anti-RA effect. Dexamethasone palmitate-loaded SALs (DP-SALs) of different particle sizes (300.2 ± 5.5 nm, 150.3 ± 4.3 nm, and 75.0 ± 3.9 nm) were prepared with DP as a model drug. Our study indicated that DP-SALs could efficiently target PBNs, with larger liposomes leading to higher drug accumulation in cells. However, a high intake of large DP-SALs by PBNs inhibited their migration ability and capacity to release the payload at the target site. In contrast, small DP-SALs (75.0 ± 3.9 nm) could maintain the drug delivery potential of PBNs, leading to their efficient accumulation at the inflammatory site, where PBNs would be excessively activated to form neutrophil extracellular traps along with efficient payload release (small DP-SALs) and finally to induce excellent anti-RA effect.