Engineered Lipid Nanoparticles with Promoted Endosomal Escape and R283S-Mediated Stimulator of Interferon Genes (STING) Activation for Pancreatic Cancer Immunotherapy

Background/Objectives: Lipid nanoparticles (LNPs) have emerged as crucial vehicles for messenger RNA (mRNA) applications in antitumor therapy. Combining LNPs with stimulator of interferon genes (STING) activation holds promise for treating “cold” tumors such as pancreatic cancer. However, two major challenges remain: inefficient mRNA escape from endosomes and STING pathway suppression in immunosuppressive tumor microenvironments. Methods: To improve endosomal escape, we developed a novel pH-responsive PEGylated lipid (Ben-mPEG2000) for mRNA-LNP preparation while using commercial Man-mPEG2000 for dendritic cell (DC)-targeted delivery of LNPs; to alleviate suppression of the STING pathway in the tumor microenvironment and activate immune responses, STING-R283S mRNA was encapsulated into LNPs, ultimately resulting in DC-targeted/pH-responsive LNPs loaded with STING-R283S mRNA for pancreatic cancer immunotherapy research. Results: After pH-responsive cleavage, Ben-mPEG2000 not only enhanced the positive charge of LNPs through the exposed protonated amino groups but also eliminated the PEG-induced steric hindrance effect. The combination of these two effects promoted membrane fusion between LNPs and the endosome, thereby enhancing mRNA translation. As a payload, STING-R283S could further amplify STING signaling in DCs without cytotoxicity to counteract immunosuppression in pancreatic cancer. Conclusions: This engineered LNP platform enhanced mRNA expression and STING activation in DCs, improving immunotherapy outcomes in pancreatic cancer.