Engineering Linear Cap-independent mRNA Vaccines with Intrinsic Adjuvanticity for Potent Cancer Immunotherapy

mRNA cancer vaccines have shown promising efficacy in early-phase clinical trials, but existing platforms struggle to boost antitumor efficacy without added cost or complexity. Here, we present a streamlined linear cap-independent RNA (LciRNA) cancer vaccine platform that achieves stable expression in vivo without 5’ capping or ribonucleotide modification, and innately stimulates immune responses to enhance antitumor immunity. By fusing a UPA protective sequence, composed of a viral exoribonuclease-resistant RNA (xrRNA) and a poly(A) binding protein (PABP) motif, with an optimized Enterovirus A internal ribosome entry site, LciRNA resists 5’ exonuclease decay and drives superior in vivo expression. Mechanistically, UPA sequence not only impedes exonuclease-mediated decay but also recruits RNA-binding proteins to stabilize LciRNA. Moreover, LciRNA robustly activates dendritic cell pattern-recognition receptor pathways, promotes dendritic cell maturation, and upregulates proinflammatory signals. In murine melanoma and HPV-associated tumor models, it elicits strong systemic and intra-tumoral T cell responses and superior tumor control, demonstrating how immune stimulation-translation synergy underpins its efficacy. This work establishes a next-generation cost-effective mRNA cancer vaccine platform with simplified production and enhanced efficacy, highlighting immuno-translation coupling as a paradigm for future mRNA cancer vaccines.