Surface-engineered milk-derived extracellular vesicles enable oral miRNA therapy against immunosuppressive pancreatic...

Pancreatic ductal adenocarcinoma (PDAC) shows limited responsiveness to conventional therapies due to an immunosuppressive tumor microenvironment (TME) characterized by programmed death-ligand 1 (PD-L1)-mediated immune escape and oncogenic microRNA-21 (miR-21) signaling. Despite the potential of miRNA therapeutics, their clinical translation is hindered by the lack of stable, non-invasive delivery systems capable of bypassing complex biological barriers. Here, we develop a scalable biogenic delivery platform based on surface-engineered milk-derived extracellular vesicles (MEVs) for systemic transport of anti-miR-21 (α21) after oral administration. MEVs were isolated using a reproducible purification workflow and functionalized with a PD-L1-binding peptide (PBP) to facilitate tumor-associated uptake while preserving vesicle integrity and colloidal stability. The engineered vesicles (α21@MEV_PBP) remained stable under simulated gastrointestinal conditions, underwent efficient transepithelial transport, and exhibited selective accumulation in PD-L1^high pancreatic tumors in vivo, demonstrating a gut-to-tumor delivery pathway. Following cellular internalization, α21 delivery restored tumor-suppressive signaling and induced endoplasmic reticulum stress-associated immunogenic cell death (ICD). Concurrently, modulation of tumor-associated macrophages toward a pro-inflammatory phenotype enhanced CD8⁺ T cell activation and antitumor immune responses, leading to significant tumor growth inhibition without detectable systemic toxicity. These findings establish α21@MEV_PBP as an orally deliverable nanoplatform that bridges biogenic material engineering with targeted immune modulation. Together, the results demonstrate that surface engineering of naturally derived vesicles enables controlled systemic RNA transport via an oral administration route and provides a generalizable strategy for non-invasive delivery of nucleic acid therapeutics to solid tumors.