Targeted Delivery of C/EBPα-saRNA by RNA Aptamers Shows Anti-tumor Effects in a Mouse Model of Advanced PDAC

Pancreatic ductal adenocarcinoma (PDAC) is one of the most aggressive malignancies; it preferentially metastasizes to the liver and is the main cause of death from this disease. In previous studies, small activating RNA against CCAAT/enhancerbinding protein-alpha (C/EBP alpha-saRNA) demonstrated efficacy of PDAC in a local subcutaneous tumor model. In this study, we focused on the efficacy of C/EBP alpha-saRNA in advanced stage PDAC. For targeted delivery, we selected a new anti-transferrin receptor aptamer (TR14), which demonstrated a high binding affinity to target proteins. The TR14 aptamer was internalized with clathrin-mediated endocytosis, distributed in early endosome, late endosome, and lysosome subcellularly. To investigate its anti-tumor effects to advanced PDAC, we conjugated C/EBP alpha-saRNA to TR14. Treatment of pancreatic cancer cells with the conjugates upregulated expression of C/EBP alpha and its downstream target p21, and inhibited cell proliferation. For in vivo assays, we established an advanced PDAC mouse model by engrafting luciferase reporter-PANC-1 cells directly into the livers of non-obese diabetic/severe combined immunodeficiency (NOD/SCID) mice. After treatment of aptamer-C/EBP alpha conjugates, we observed significant reduction of tumor growth in this advanced PDAC mouse model. Combinational treatment of the conjugates with gemcitabine also demonstrated enhanced anti-tumor effects in advanced PDAC. This suggests that aptamer-C/EBP alpha conjugates could be used as an adjuvant, along with other conventional anti-cancer drugs in advanced PDAC. In conclusion, targeted delivery of C/EBP alpha-saRNAs by aptamers might have potential therapeutic effects in advanced PDAC.