Enhancing antitumor immunity through chemotherapeutic-derived lipid nanoparticle-induced immunogenic cell death and CD40L/Flt3L mRNA-mediated dendritic cell activation.

Dendritic cells (DCs) are essential for inducing effective antitumor T cell responses. However, the immunosuppressive tumor microenvironment (TME) hinders DC recruitment and maturation, facilitating tumor progression and spread. This study investigates the synergistic potential of immunogenic cell death (ICD), triggered by chemotherapeutic-derived lipid nanoparticles (LNPs), in combination with Flt3L and CD40L mRNA delivery to enhance DC mobilization and activation, reprogram the TME, and ultimately promote robust antitumor T cell responses. The optimized LNP formulation, GEM5Q7, efficiently delivered mRNA and induced ICD in melanoma cells. Intratumoral administration of GEM5Q7, encapsulating Flt3L and CD40L mRNAs, elevated pro-inflammatory cytokine and chemokine secretion, driving the infiltration and activation of cross-presenting DCs, which are critical for priming T cells. In a subcutaneous melanoma model, this approach led to significant tumor suppression and a 40 % complete response rate. This strategy holds promise for enhancing cancer immunotherapies by reprogramming the TME and inducing durable antitumor T cell immunity.