Synthetic RIG-I-Agonist RNA Induces Death of Hepatocellular Carcinoma Cells

Retinoic acid-inducible gene I (RIG-I) is a critical sensor of viral RNA and is activated in response to binding to RNA containing exposed 5'-triphosphate (5'ppp) and poly-uridine to trigger innate immune activation and response including induction of type I and III interferons (IFNs). RIG-I signaling plays a key role in not only restricting RNA virus infection but also suppressing tumor progression via oncolytic signaling. We evaluated the actions of a specific RIG-I agonist RNA (RAR) as a potential therapeutic against model tumor cell lines representing hepatocellular carcinoma (HCC). RAR constitutes a synthetic-modified RNA motif derived from the hepatitis C virus genome that is specifically recognized by RIG-I and induces innate immune activation when delivered to cells. We found that RAR directs RIG-I-dependent signaling to drive HCC cell death. Analysis of knockout cell lines lacking RIG-I, mitochondrial activator of virus signaling, or IRF3 confirmed that RAR-induced cell death signaling propagates through the RIG-I-like receptor (RLR) pathway to mediate caspase activation and HCC cell death. RAR-induced cell death is potentiated by type I IFN. Thus, RAR actions trigger HCC cell death through RIG-I linkage of RLR, caspase, and IFN signaling programs. RAR offers a potent application in antitumor therapeutic strategies leveraging innate immunity against liver cancer.