Targeted Delivery of Circular Single‐Stranded DNA Encoding IL‐12 for the Treatment of Triple‐Negative Breast Cancer

Abstract Interleukin‐12 (IL‐12) is a critical cytokine with notable anticancer properties, including enhancing T‐cell‐mediated cancer cell killing, and curbing tumor angiogenesis. To date, many approaches are evaluated to achieve in situ overexpression of IL‐12, minimizing leakage and the ensuing toxicity. Here, it is focused on circular single‐stranded DNA (Css DNA), a type of DNA characterized by its unique structure, which could be expressed in mammals. It is discovered that Css DNA can induce sustained luciferase expression for half a year by intramuscular injection and showed effective antitumor results by intratumoral injection. Motivated by these findings, a folate‐modified LNP system is now developed for the delivery of Css DNA expressing IL‐12 for the therapy of 4T1 triple‐negative breast cancer (TNBC). This delivery system effectively activates anti‐cancer immune responses, slows tumor growth, significantly prolongs survival in animal models, and prevents tumor recurrence. After 6 months of long‐term observation, the elevated level of IL‐12 is still detectable in the lymph nodes and serum of the cured mice. This study highlights the long‐term sustained expression capacity of Css DNA and its ability to inhibit recurrence, and the potential of tumor‐targeted LNPs for Css DNA‐based cancer therapy, providing a new insight into gene overexpression strategy.