Transdermal PTEN mRNA Delivery via HA-LNPs for Melanoma Therapy

Study Background and Research Question

Melanoma remains among the most aggressive forms of skin cancer, characterized by high metastatic potential and frequent resistance to immunotherapies. One critical mechanism underlying immune evasion and therapy failure in melanoma is the loss of phosphatase and tensin homolog (PTEN) expression, which disrupts the PI3K/AKT pathway and impairs T cell-mediated tumor clearance. While immune checkpoint inhibitors (ICIs) such as anti-PD-1 and anti-CTLA-4 have improved patient outcomes, a substantial proportion of melanoma cases remain refractory due to PTEN deficiency and subsequent immune escape. This has prompted the search for targeted strategies to restore PTEN function and re-sensitize tumors to immune attack.

Key Innovation from the Reference Study

The study by Kim et al. (Journal of Controlled Release 390 (2026) 114518) introduces a novel formulation of hyaluronate-conjugated lipid nanoparticles (HA-LNPs) engineered for the non-invasive, transdermal delivery of PTEN mRNA. The core innovation lies in the use of a hyaluronate-dimyristoyl glycerol (HA-DMG) amphiphilic lipid, which incorporates directly into the LNP bilayer during assembly. This approach replaces conventional PEG-lipid stabilizers—known for their immunogenicity and risk of anaphylaxis—with HA-DMG, which serves dual roles as a stabilizing agent and CD44-targeting ligand. The resulting HA-LNPs are designed to efficiently encapsulate large mRNA payloads, penetrate the skin barrier, and selectively target CD44-expressing tumor cells and antigen-presenting cells in the skin microenvironment.

Methods and Experimental Design Insights

To investigate the therapeutic potential of HA-LNPs for melanoma immunotherapy, the researchers synthesized HA-DMG and formulated it with established LNP components to encapsulate in vitro-transcribed, chemically modified PTEN mRNA. The mRNA utilized modifications to enhance stability and translation while minimizing immune activation, an increasingly standard practice in advanced mRNA delivery research. Key methodological steps included:

• Optimization of HA-DMG content for stable LNP formation and surface display of HA moieties.
• Assessment of particle size, uniformity, and mRNA encapsulation efficiency.
• In vitro evaluation of CD44-mediated uptake in melanoma cell lines and primary skin cells.
• Restoration of PTEN expression and downstream signaling in PTEN-deficient melanoma cultures.
• In vivo application of PTEN mRNA@HA-LNPs via topical administration to melanoma-bearing mice, with analysis of skin/tumor penetration, tumor growth inhibition, and immune cell activation.

A notable aspect of the design is the direct self-assembly of HA-LNPs, eliminating the need for post-formulation surface coatings and reducing batch-to-batch variability.

Core Findings and Why They Matter

The HA-LNP platform demonstrated several key advantages over conventional PEG-LNPs and alternative delivery systems:

• Efficient transdermal penetration: Topically applied HA-LNPs achieved deep skin and tumor infiltration, attributed to HA-mediated hydration, CD44 targeting, and favorable nanoparticle size.
• Targeted delivery and cellular uptake: The CD44-targeting capability led to selective uptake by melanoma cells and skin-resident antigen-presenting cells, maximizing local mRNA delivery while minimizing off-target effects.
• Restoration of PTEN expression: Delivered mRNA induced robust PTEN protein synthesis in tumor cells, restoring negative regulation of the PI3K/AKT pathway and suppressing oncogenic signaling.
• Immunogenic cell death and immune activation: PTEN restoration promoted immunogenic cell death, enhanced tumor infiltration by cytotoxic T cells, and increased markers of immune activation.
• Significant tumor growth inhibition: In murine melanoma models, repeated topical treatment with PTEN mRNA@HA-LNPs led to marked tumor regression and no observable systemic toxicity.

These findings collectively support the feasibility of non-invasive, mRNA-based approaches to restore tumor suppressor activity and overcome resistance to immunotherapy in melanoma. The use of HA-LNPs as both a stabilizer and targeting moiety offers a clinically translatable alternative to PEG-LNP platforms, particularly in the context of cutaneous applications where local delivery and immune modulation are paramount (reference study).

Comparison with Existing Internal Articles

The strategies and insights from this reference study align with key themes in translational mRNA delivery research, as outlined in recent internal articles. For example, "EZ Cap™ Cy5 EGFP mRNA (5-moUTP): Dual-Fluorescent, Cap1-M..." and "Applied Workflows with EZ Cap™ Cy5 EGFP mRNA (5-moUTP)" describe how dual-fluorescent, chemically modified mRNAs enable real-time tracking of both mRNA delivery and translation efficiency in vitro and in vivo. These resources emphasize the importance of Cap 1 structures, 5-methoxyuridine incorporation, and Cy5 labeling for quantitative mRNA delivery and translation efficiency assays, echoing the reference study's focus on enhanced mRNA stability, immune evasion, and functional protein readout. Both approaches highlight the central challenge of achieving effective, immune-evasive, and quantitatively traceable mRNA delivery, whether for tumor suppressor restoration or broader gene regulation and function studies.

Limitations and Transferability

While the HA-LNP approach shows considerable promise in preclinical melanoma models, several limitations should be acknowledged. First, the study's findings are limited to murine models, and the scalability, immunogenicity, and pharmacokinetics of HA-LNPs in human skin remain to be fully characterized. The specificity of CD44-targeting may vary across tumor types and patient populations, potentially affecting delivery efficiency. Additionally, although chemically modified mRNA reduces innate immune activation, there remains a need for systematic assessment of long-term safety, off-target effects, and repeated dosing regimens. The platform's applicability to other forms of cancer or non-cutaneous applications will require further validation. However, the modularity of HA-LNPs and the generalizability of mRNA delivery principles suggest broad potential for adaptation to other targets and tissues.

Protocol Parameters

• HA-LNP self-assembly: Optimize HA-DMG content for stable bilayer integration during nanoparticle formation; avoid post-formulation HA coating to reduce variability.
• mRNA payload: Use chemically modified mRNA (e.g., 5-methoxyuridine, Cap 1 structure) to enhance stability and minimize immune activation; verify encapsulation efficiency before application.
• Topical administration: Apply HA-LNPs to shaved skin overlying the tumor; ensure even distribution and gentle massage to promote penetration.
• In vitro validation: Confirm CD44-mediated uptake and functional protein restoration in relevant cell lines prior to in vivo studies.
• Dosing regimen: For murine models, repeat topical application every 2–3 days; monitor tumor growth, immune infiltration, and potential toxicity throughout the study.

Research Support Resources

To facilitate advanced mRNA delivery and translation efficiency assays, researchers can incorporate EZ Cap™ Cy5 EGFP mRNA (5-moUTP) (SKU R1011) into their workflows. This dual-fluorescence, Cy5-labeled mRNA reagent—optimized with Cap 1 structure and 5-methoxyuridine—enables simultaneous quantification of mRNA uptake and functional protein expression, supporting optimization and validation of nanoparticle delivery systems in both in vitro and in vivo settings. The reagent's features, including suppression of RNA-mediated innate immune activation and robust readout of gene regulation, align with the methodological advances described in the reference study. For practical guidance on integrating such reporters into comparative nanoparticle validation or gene regulation and function studies, consult the internal article here.