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In different types of cancer treatments, cancer-specific T cells are required for effective anticancer immunity, which has a central role in cancer immunotherapy. However, due to the multiple inhibitions of CD8+ T cells by tumor-related immune cells, CD8+ T-cell mediated antitumor immunotherapy has not achieved breakthrough progress in the treatment of solid tumors. Receptors for sialic acid (SA) are highly expressed in tumor-associated immune cells, so SA-modified nanoparticles are a drug delivery nanoplatform using tumor-associated immune cells as vehicles. To relieve the multiple inhibitions of CD8+ T cells by tumor-associated immune cells, we prepared SA-modified doxorubicin liposomes (SL-DOX, Scheme 1A). In our study, free SA decreased the toxicity of SL-DOX to tumor-associated immune cells. Compared with common liposomes, SL-DOX could inhibit tumor growth more effectively. It is worth noting that SL-DOX could not only kill tumor-related neutrophils and monocytes to relieve the multiple inhibitions of CD8+ T cells but also induce immunogenic death of tumor cells to promote the infiltration and differentiation of CD8+ T cells (Scheme 1B). Therefore, SL-DOX has potential value for the clinical therapeutic effect of CD8+ T cells mediating anti-tumor immunotherapy. [ABSTRACT FROM AUTHOR]

In preclinical studies of young mice, nanoparticles showed excellent anti-tumor therapeutic effects by harnessing Peripheral Blood Monocytes (PBMs) and evading the immune system. However, the changes of age will inevitably affect PBMs and the immune system, and there is a serious lack of relevant research. Sialic acid (SA)-octadecylamine (ODA) was synthesized, and SA- or polyethylene glycol (PEG)-modified epirubicin (EPI) liposomes (EPI-SL and EPI-PL, respectively) were prepared to explore differences in antitumor treatment using 8-month-old and 8-week-old Kunming mice. Based on presented data, 8-month-old mice had more PBMs in peripheral blood than 8-week-old mice, and age differences resulted in different anti-tumor treatment effects following EPI-SL and EPI-PL treatment. Following EPI-PL administration, the tumor volume was significantly smaller in 8-week-old mice than in 8-month-old mice (* p < 0.05). Eight-month-old mice treated with EPI-SL (8M-SL) presented no damage to healthy tissue, with a 100% survival rate, and 50% mice in 8M-SL showed 'shedding' of tumor tissues from the growth site. Accordingly, 8-month-old mice treated with EPI-SL achieved the best therapeutic effect at different ages and with different liposomes. EPI-SL could improve the antitumor effect of 8-week-old and 8-month-old mice. [ABSTRACT FROM AUTHOR]

mRNA vaccines are attractive prospects for the development of DC-targeted vaccines; however, no clinical success has been realized because, currently, it is difficult to simultaneously achieve DC targeting and efficient endosomal/lysosomal escape. Herein, we developed a sialic acid (SA)-modified mRNA vaccine that simultaneously achieved both. The SA modification promoted DCs uptake of lipid nanoparticles (LNPs) by 2 times, >90% of SA-modified LNPs rapidly escaped from early endosomes (EEs), avoided entering lysosomes, achieved mRNA simultaneously translated in ribosomes distributed in the cytoplasm and endoplasmic reticulum (ER), significantly improved the transfection efficiency of mRNA LNPs in DCs. Additionally, we applied cleavable PEG-lipids in mRNA vaccines for the first time and found this conducive to cellular uptake and DC targeting. In summary, SA-modified mRNA vaccines targeted DCs efficiently, and showed significantly higher EEs/lysosomal escape efficiency (90% vs 50%), superior tumor treatment effect, and lower side effects than commercially formulated mRNA vaccines. The SA-modified mRNA vaccine prepared by microfluidic mixture synchronously realizes DCs targeted and efficient EEs and lysosome escape, activates the immune system to eliminate tumors. [Display omitted] • Simultaneously achieving DC targeting and efficient endosomal/lysosomal escape. • First to apply sialic acid- lipid derivative and cleavable PEG-lipid on mRNA LNPs. • Constructed a new computational model to evaluate the transfection efficiency of mRNA delivery vectors. • SA modification significantly improved the antitumor efficacy of mRNA vaccine, and has fewer side effects. [ABSTRACT FROM AUTHOR]

Sialic acid derivatives (SA-derivatives) provide a nanomedicine platform for tumor-targeted delivery and treatment, and allow modulation of immunosuppressive tumor microenvironments with excellent therapeutic effects. Further, the multi-reactive groups of sialic acid (SA) contribute to the diversity of SA derivatives, which inevitably has implications for drug delivery systems and tumor therapy. However, relevant research remains lacking at present. Therefore, this study aimed to explore the effects of SA derivatives on SA-mediated drug delivery systems. Four SA-derivatives with different linking bonds (ester and amide bonds), different linking groups (hydroxyl and carboxyl), and different linking objects (cholesterol, octadecanoic acid, and octadecylamine) were synthesized and the respective SA derivative-modified doxorubicin liposomes were prepared. In-depth research was conducted using both cells and animals. We found that an SA-cholesterol conjugate (SA-CH; linking bond, amide bond; linking group, carboxyl; linking object, cholesterol) could improve liposome stability, reduce liposome adsorption to plasma proteins, and enhance the targeting of liposomes for killing tumor-associated macrophages (TAMs). Reduced TAMs in the immunosuppressive tumor microenvironment lead to enhanced tumor infiltration of CD8+ T cells. The results of this experiment provide clarity for research and development on SA-derivatives and a theoretical basis for clinical trials of SA-derivative-modified nanoparticles. [Display omitted] • Sialic acid-derivatives modified liposomes modulated immunosuppressive tumor microenvironment. • Sialic acid-derivatives linking bonds, linking groups, and linking objects influenced sialic acid mediated drug delivery systems. • Sialic acid-cholesterol conjugate could improve the stability of liposomes. • Sialic acid-cholesterol conjugate enhanced the targeting and killing of liposomes to tumor-associated macrophages. • The carboxyl group of sialic acid was not the key to affecting the anti-tumor therapeutic effect of sialic acid modified liposomes. [ABSTRACT FROM AUTHOR]

[Display omitted] 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. [ABSTRACT FROM AUTHOR]

Immune checkpoint inhibitors (ICIs), like monoclonal antibodies of PD-1, CTLA-4, and their ligands, are effective only in some populations of patients with cancer, because the immunosuppressive state of the tumor microenvironment (TME) in some patients cannot be effectively reversed after ICI therapy. Sialic acid (SA) receptors in the Siglec family are highly expressed on the surface of tumor-associated macrophages (TAMs) and most have immunosuppressive effects. Therefore, targeting TAMs (the siglec axis) to reverse tumor immunosuppression may provide a new direction for the development of novel tumor immunotherapies. We designed a Zoledronic acid (ZA)-loaded liposome modified by a SA–octadecylamine conjugate (ZA-SL) to act as a novel nanomedicine delivery platform. This platform can efficiently deliver ZA to TAMs through the combination of SA and Siglec-1 and exerts specific cytotoxicity or phenotypic remodeling of M2-like TAMs depending on the drug concentration in TAMs. In vivo experiments showed that ZA-SL had good TAM targeting ability, and after treatment, the S180 tumors of mice were significantly inhibited, and the proportion of M1-like TAMs was significantly higher than that of M2-like TAMs with no significant adverse reactions in mice. Therefore, SA-modified ZA-loaded liposomes may provide a promising strategy for cancer immunotherapy. [ABSTRACT FROM AUTHOR]

Schematic diagram showing the binding of SA-ODA and GM1 co-modified liposome to Siglec-1 receptor on the surface of TAMs. GM1, monosialotetrahexosylganglioside; SA-ODA, sialic acid-octadecylamine; TAMs, tumor-associated macrophage. [Display omitted] 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. [ABSTRACT FROM AUTHOR]