Lipid Nanoparticles for mRNA Delivery to Enhance Cancer Immunotherapy

Purpose: mRNA is a promising cancer immunotherapy platform for vaccines, cytokines, costimulatory receptors, and therapeutic antibodies, but it is unstable, immunogenic, and poorly delivered in vivo. Safer and more efficient delivery systems are needed to improve mRNA stability, cellular uptake, endosomal escape, and tumor-site accumulation.

Hypothesis: If mRNA is encapsulated in optimized lipid nanoparticles—using appropriate cationic/ionizable lipids, helper lipids, cholesterol, and PEG-lipids, with optional targeting moieties—then it can be protected from degradation, delivered to tumor or immune cells, translated into immunomodulatory proteins, and enhance antitumor immunity with reduced systemic toxicity.

Aims: Summarize common cancer immunotherapy approaches and mRNA delivery strategies. - Describe typical lipid nanoparticles for mRNA delivery: liposomes, nanodiscs, lipid–polymer hybrid nanoparticles, and micelles. - Highlight clinical advantages, challenges, and future developments of LNP-mRNA technology for cancer immunotherapy.

Delivery system: Platform: lipid nanoparticles (LNPs), including liposomes, nanodiscs, lipid–polymer hybrid nanoparticles, and micelles. - Key lipid components: cationic lipids (e.g., DOTAP, DOTMA, DDAB); ionizable lipids; helper lipids (e.g., DOPE, DOPC, DSPC); cholesterol and cholesterol analogues; PEG-lipids. - Payload: mRNA encoding tumor antigens, cytokines, costimulatory receptors, therapeutic antibodies, erythropoietin (EPO), and other immunomodulatory proteins. - Targeting/functionalization: antibodies, ligands, PEG modification, passive targeting, and active targeting. - Representative systems: PL1 lipid nanoparticles, siPD-L1@PM/DOX@LPs, HDL nanodiscs, lipid–polymer hybrid nanoparticles, PLA-based RALA micelles.

Approach: Review and synthesis of preclinical and clinical literature. In vitro models include MCF-7 cells; in vivo models include B16F10 melanoma, fetal mouse delivery, and various tumor models. Clinical examples include mRNA-1273 and BNT162b2 COVID-19 vaccines. As a review, it reports no primary experimental groups, n values, doses, or controls.

Key methods: No primary methods. The review discusses data generated by cited studies using flow cytometry, tumor volume and weight measurements, H&E staining, IFN-γ ELISA, ELISPOT, GFP/EPO expression assays, and immune response profiling.

Key results: PL1 LNPs delivering CD137 or OX40 mRNA to tumor-infiltrating T cells, combined with anti-OX40 antibody, showed more significant antitumor activity than anti-OX40 antibody alone in multiple tumor models. - siPD-L1@PM/DOX@LPs showed excellent serum stability, delivered siRNA into MCF-7 cells, reduced PD-L1 expression, and enhanced immunotherapy. - HDL nanodisc vaccines combined with PD-1 and CTLA-4 blockade eradicated established B16F10 melanoma tumors in approximately 60% of treated animals. - Lipid–polymer hybrid nanoparticles delivered mRNA in utero to fetal liver, lungs, and intestine; EPO mRNA delivery increased EPO protein in fetal liver. - PLA-based micelles coupled with RALA peptides protected mRNA from serum nucleases, reduced cationic peptide toxicity, and facilitated dendritic cell transfection. - mRNA-LNP COVID-19 vaccines (mRNA-1273 and BNT162b2) demonstrated the clinical potential of LNP-mRNA delivery.

Interpretation: The authors conclude that lipid nanoparticles are excellent nanodrug carriers for mRNA delivery in cancer immunotherapy. They highlight advantages including targeting, biocompatibility, prolonged drug half-life, and suitability for combination therapy, and predict that next-generation LNPs will further advance tumor immunotherapy.

Limitations: Review article; no primary experimental data, effect sizes, n values, doses, or controls. - mRNA instability and high immunogenicity remain barriers to clinical translation. - Targeted delivery and endosomal escape are still major challenges. - Cationic lipids can be neutralized by anionic serum proteins, reducing delivery efficiency. - PEG-related immune concerns and manufacturing complexity can hinder clinical application. - Many examples remain preclinical or animal-model-based; further optimization of lipid type, binding bonds, and drug/antibody binding rates is needed.