From structural design to delivery: mRNA therapeutics for cancer immunotherapy

An overview of lipid constituents in lipid nanoparticle mRNA delivery systems

mRNA therapeutics have shown great potential for a broad spectrum of disease treatment. However, the challenges of mRNA's inherent instability and difficulty in cellular entry have hindered its progress in the biomedical field. To address the cellular barriers and deliver mRNA to cells of interest, various delivery systems are designed. Among these, lipid nanoparticles (LNPs) stand out as the most extensively used mRNA delivery systems, particularly following the clinical approvals of corona virus disease 2019 (COVID-19) mRNA vaccines. LNPs are comprised of ionizable cationic lipids, phospholipids, cholesterol, and polyethylene glycol derived lipids (PEG-lipids). In this review, we primarily summarize the recent advancements of the LNP mRNA delivery technology, focusing on the structures of four lipid constituents and their biomedical applications. We delve into structure-activity relationships of the lipids, while also exploring the future prospects and challenges in developing more efficacious mRNA delivery systems. This article is categorized under: Therapeutic Approaches and Drug Discovery > Emerging Technologies Biology-Inspired Nanomaterials > Lipid-Based Structures Nanotechnology Approaches to Biology > Nanoscale Systems in Biology.

Triple-transformable dynamic surroundings for programmed transportation of bio-vulnerable mRNA payloads towards systemic treatment of intractable solid tumors

The surface physiochemical properties of nanomedicine play a crucial role in modulating biointerfacial reactions in sequential biological compartments, accordingly accomplishing the desired programmed delivery scenario to intracellular targets. PEGylation, which involves modifying the surface with a layer of poly(ethylene glycol), has been validated as an effective strategy for minimizing adverse biointerfacial interactions. However, it has also been observed to impede cellular uptake and intracellular trafficking activities. To address this dilemma, we propose a dynamic surface chemistry approach that actively prevents non-specific reactions in systemic circulation, while readily facilitating cellular uptake by converting into a highly cytomembrane-adhesive state. Moreover, the surface becomes more adhesive to endolysosomal membranes, enabling translocation into the cytosol. In this study, PEGylated mRNA delivery nanoparticulates were tethered with charge-reversible polymers to create dynamic surroundings through click chemistry. Importantly, the dynamic surroundings exhibited negative charges under physiological conditions (pH 7.4). This property prevented degradation by anionic nucleases and structural disassembly induced by endogenous charged biological species. Consequently, the nanoparticles exhibited appreciable stealth function, effectively managing the first pass effect, leading to prolonged blood retention and improved bioavailabilities at targeted cells. Furthermore, the dynamic surroundings shifted towards relatively positive charges in the tumor microenvironment (pH 6.8). As a result, the nanoparticles were more likely to be taken up by tumors due to their electrostatic affinities towards polyanionic cytomembranes. Eventually, the internalized mRNA nanomedicine transformed responsive to the surrounding microenvironment into highly positive charges within acidic endolysosomes (pH 5.0), exerting explosive disruptive potencies on the endolysosomal structures, thus facilitating translocation of mRNA from the digestive endolysosomes into the targeted cytosol. Notably, the dynamic surroundings also reduced the immunogenicity of naked mRNA due to their stealthy properties and rapid endolysosomal translocation functions. In summary, our proposed unique triple-transformable dynamic surface chemistry provided an intriguing delivery scenario that overcomes sequential biological barriers, contributing to efficient expression of the encapsulated mRNA at targeted tumors.

Exploring tumor organoids for cancer treatment

As a life-threatening chronic disease, cancer is characterized by tumor heterogeneity. This heterogeneity is associated with factors that lead to treatment failure and poor prognosis, including drug resistance, relapse, and metastasis. Therefore, precision medicine urgently needs personalized tumor models that accurately reflect the tumor heterogeneity. Currently, tumor organoid technologies are used to generate in vitro 3D tissues, which have been shown to precisely recapitulate structure, tumor microenvironment, expression profiles, functions, molecular signatures, and genomic alterations in primary tumors. Tumor organoid models are important for identifying potential therapeutic targets, characterizing the effects of anticancer drugs, and exploring novel diagnostic and therapeutic options. In this review, we describe how tumor organoids can be cultured and summarize how researchers can use them as an excellent tool for exploring cancer therapies. In addition, we discuss tumor organoids that have been applied in cancer therapy research and highlight the potential of tumor organoids to guide preclinical research.

MazF-rolling circle amplification combined MALDI-TOF MS for site-specific detection of N6-methyladenosine RNA

N6-methyladenosine (m6A) is one of the most abundant chemical modifications in RNA and has vital significance in cellular processes and tumor development. However, the accurate analysis of site-specific m6A modification remains a challenge. In this work, a MazF endoribonuclease activated rolling circle amplification (MazF-RCA) combined MALDI-TOF MS assay is developed for the detection of site-specific m6A-RNA. MazF endoribonuclease can specifically cleave the ACA motif, leaving methylated (m6A)CA motif intact. The intact methylated RNA can then be amplified through rolling circle amplification, and the generated reporter oligonucleotides are detected by MALDI-TOF MS. The assay exhibits good quantification ability, presenting a wide linear range (100 fM to 10 nM) with the limit-of-detection lower than 100 fM. Additionally, the assay can accurately detect methylated RNA in the presence of large amount of non-methylated RNA with a relative abundance of methylated RNA down to 0.5%. The developed assay was further applied to detect m6A-RNA spiked in MCF-7 cell RNA extracts, with the recovery rates in the range of 90.64-106.93%. The present assay provides a novel platform for the analysis of site-specific m6A-RNA at high specificity and sensitivity, which can promote the study of RNA methylation in clinical and biomedical research.