Single-Stranded RNA Origami Remodels Macrophage to Promote the Synergistic Antitumor Effect with 5‑Fluorouracil in Pancreatic Cancer

The advancement of cancer immunotherapy has focused on developing therapies that not only target tumor progression but also enhance immune responses, which could potentially shift the balance within the tumor microenvironment (TME) to promote a more immune-competent environment and improve the effectiveness of antitumor immunotherapies. This study evaluates the internalization of single-stranded RNA origami (ssRNAOG) in coculture models mimicking the TME in vitro and the antitumor efficacy of the combination of ssRNAOG with 5-fluorouracil (5-FU) in pancreatic ductal adenocarcinoma (PDAC) models. The internalization of ssRNAOG triggers the TLR3 signaling pathway, leading to robust innate immune activation. Notably, ssRNAOG induces the overexpression of MHC class I protein on macrophages, which recruits NK cells into the TME. The combination of ssRNAOG and 5-FU significantly suppressed tumor cell colony formation in vitro, demonstrating a synergistic antiproliferative effect. Transcriptomic and proteomic analyses revealed a significant upregulation of inflammatory cytokines and the activation of NF-κB and STAT1, which are indicative of M1-like polarization in macrophages. In vivo administration of both ssRNAOG and 5-FU revealed a marked reduction in tumor burden and an extension of survival in mice bearing xenograft PDAC tumors. Immunohistochemistry revealed a shift in macrophage polarization toward the M1-like phenotype, which is associated with enhanced proinflammatory responses and reduced tumor proliferation. These findings indicate that ssRNAOG, as a potent modulator of the TME that can sensitize resistant tumors to chemotherapy, presents a novel immunotherapeutic strategy for PDAC.