A Strand-Displacement Enabled DNA Nanomachine for Targeted St6Gal1 Silencing and Immune Reprogramming in Melanoma

Dynamic nanomachines capable of selectively engaging tumor-infiltrating immune cells and modulating their intrinsic functions represent a critical unmet need in cancer immunotherapy. Here, we develop an intelligent DNA nanomachine that selectively targets dendritic cells (DCs) within the tumor microenvironment and modulates their immunological function through regulation of prosaposin glycosylation. The nanomachine is constructed on a tetrahedral DNA nanostructure (TDN) and integrates an acid-responsive strand displacement cascade. Selective activation of this cascade in the acidic tumor microenvironment exposes a DC-SIGN-binding aptamer, thereby enabling preferential engagement with tumor-infiltrating DCs. In parallel, the nanomachine initiates RNA interference to silence St6Gal1, leading to suppression of aberrant prosaposin hyperglycosylation in melanoma-associated DCs. This spatiotemporally controlled modulation minimizes off-target interference with immune cells in normal tissues, restores the functional competence of intratumoral DCs, consequently enhances intratumoral T-cell infiltration, and markedly suppresses melanoma growth in mice. Collectively, this work establishes a programmable, strand-displacement-driven DNA nanomachine that integrates tumor microenvironment-triggered DC targeting with glycosylation-directed functional modulation, offering a generalizable strategy for precise remodeling of the tumor immune microenvironment.