SNORA49 negatively regulates self-renewal of liver cancer stem cells and hepatocarcinogenesis via suppressing SOX9 transcription

Cancer stem cells (CSCs) play a critical role in tumor initiation, progression, and recurrence. How liver CSCs initiate their self-renewal remains elusive. Here we identify a conserved small nucleolar RNA (snoRNA), SNORA49, which is lowly expressed in liver CSCs, as a negative regulator of CSC self-renewal. SNORA49 knockout enhances the self-renewal capacity of liver CSCs and accelerates hepatocellular carcinoma (HCC) tumorigenesis, whereas overexpression of SNORA49 suppresses tumor formation. Mechanistically, in non-CSCs, SNORA49 is specifically localized in the nucleoplasm to associate with HNRNPU, blocking its interaction with ZC3H18, resulting in inhibition of SOX9 transcription. In liver CSCs, lowly expressed SNORA49 releases HNRNPU to engage with ZC3H18 and enrich on the promoter of SOX9, leading to its transcription. Of note, lipid nanoparticle (LNP)-mediated delivery of SNORA49 RNAs and antisense oligonucleotides (ASOs) targeting SOX9 exerts potent synergistic anti-tumor effect on HCC tumors. Our findings define SNORA49 as a tumor suppressor in liver CSCs, and restoring SNORA49 levels and silencing SOX9 with LNP-delivered system may provide therapeutic strategy for clinical intervention to HCC patients.