Abstract: Provided are methods and compositions for the heterologous expression of a payload (e.g., DNA, RNA, protein) of interest in a target cell (e.g., cancer cell). In some cases payload delivery results in expression (e.g., by a cancer cell in vivo) of a secreted immune signal such as a cytokine, a plasma membrane-tethered affinity marker (thus resulting in an induced immune response), or a cytotoxic protein such as an apoptosis inducer (e.g., by a cancer cell in vivo). Payloads are delivered with a delivery vehicle and in some cases the delivery vehicle is a nanoparticle. In some cases a subject nanoparticle includes a targeting ligand for targeted delivery to a specific cell type/tissue type (e.g., a cancerous tissue/cell). In some embodiments, payload delivery is “personalized” in the sense that the delivery vehicle and/or payload can be designed based on patient-specific information.