Enhanced mitophagy driven by ADAR1-GLI1 editing supports the self-renewal of cancer stem cells in HCC

Abstract

Background and Aims: Deregulation of adenosine-to-inosine editing by adenosine deaminase acting on RNA 1 (ADAR1) leads to tumor-specific transcriptome diversity with prognostic values for HCC. However, ADAR1 editase-dependent mechanisms governing liver cancer stem cell (LCSC) generation and maintenance have remained elusive. Approach and Results: RNA-seq profiling identified ADAR1-responsive recoding editing events in HCC and showed editing frequency of GLI1, rather than transcript abundance was clinically relevant. Functional differences in LCSC self-renewal and tumor aggressiveness between wild-type (GLI1wt) and edited GLI1 (GLI1edit) were elucidated. We showed that overediting of GLI1 induced an arginine-to-glycine (R701G) substitution, augmenting tumor-initiating potential and exhibiting a more aggressive phenotype. GLI1R701G harbored weak affinity to SUFU, which in turn, promoted its cytoplasmic-to-nuclear translocation to support LCSC self-renewal by increased pluripotency gene expression. Moreover, editing predisposed to stabilize GLI1 by abrogating β-TrCP-GLI1 interaction. Integrative analysis of single-cell transcriptome further revealed hyperactivated mitophagy in ADAR1-enriched LCSCs. GLI1 editing promoted a metabolic switch to oxidative phosphorylation to control stress and stem-like state through PINK1-Parkin-mediated mitophagy in HCC, thereby conferring exclusive metastatic and sorafenib-resistant capacities. Conclusions: Our findings demonstrate a novel role of ADAR1 as an active regulator for LCSCs properties through editing GLI1 in the highly heterogeneous HCC.