Summary Hepatocellular carcinoma (HCC), the fifth most common cancer and the second most common cause of cancer-related deaths worldwide, has no effective treatment for advanced disease. The present proposal focuses on two interacting proteins, AEG-1 and SND1, which function as bona fide oncogenes for HCC. AEG-1 and SND1 cooperate to increase RNA-induced silencing complex (RISC) activity where AEG-1 functions as a scaffold protein and SND1 functions as a nuclease. However, there is a gap of knowledge in our understanding of the mechanism(s) driving AEG-1 and SND1 cooperative oncogenic functions. In primary hepatocytes, AEG- 1 is predominantly localized in the nucleus, while in HCC cells AEG-1 is primarily localized in the endoplasmic reticulum (ER) membrane. Preliminary results indicate ER-anchoring is required for AEG-1 oncogenic function. ER-anchored AEG-1 binds specifically to secretory and membrane protein-encoding mRNAs to facilitate their translation. Analysis of SND1 RNA-interactome also identifies membrane protein-encoding mRNAs. Co- localization studies show that both AEG-1 and SND1 are located on ER membrane in HCC cells. Both AEG-1 and SND1 activate NF-κB. ER-anchored AEG-1 functions as a platform for upstream signaling molecules of NF-κB pathway and thus plays an essential role in NF-κB activation. The mechanism by which SND1 activates NF-κB is not known. We hypothesize that in transformed hepatocytes, AEG-1 translocates from the nucleus and anchors into the ER membrane where it recruits SND1 and both cooperate to promote HCC by modulating post-transcriptional regulation of mRNAs in RISC, translational regulation of membrane proteins and activation of NF-κB, AEG-1 and SND1 require each other for optimum functioning and might not exert oncogenic activity alone, and combinatorial inhibition of AEG-1 and SND1 might be an effective therapeutic strategy for HCC. Experiments are designed to interrogate these hypotheses using novel mouse models and targeted nanoplexes delivering siRNA for AEG-1 and SND1. This proposal will contribute to our long-term objectives of identifying key players regulating HCC pathogenesis and translating this knowledge into development of novel and effective targeted therapies. The immediate objective of the proposal is in-depth understanding of the molecular mechanisms by which AEG-1 and SND1 promote HCC and evaluate a combinatorial strategy of inhibiting AEG-1 and SND1 in a mouse model as a potential therapeutic. Thus the proposal has both mechanistic and therapeutic significance and innovation. Successful completion of the proposed studies will establish new targets for developing therapeutics and provide pre-clinical evidence for a targeted protocol.