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

Abstract

<p><strong>Background and aims: </strong>Deregulation of adenosine-to-inosine (A-to-I) editing by adenosine deaminase acting on RNA 1 (ADAR1) leads to tumor-specific transcriptome diversity with prognostic values for hepatocellular carcinoma (HCC). However, ADAR1 editase-dependent mechanisms governing liver cancer stem cell (LCSC) generation and maintenance have remained elusive.</p><p><strong>Approach and results: </strong>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 (GLI1 wt ) and edited GLI1 (GLI1 R701G ) 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. GLI1 R701G 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 predisposes to stabilized 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 (OXPHOS) to control stress and stem-like state via PINK1-Parkin-mediated mitophagy in HCC, thereby conferring exclusive metastatic and sorafenib-resistant capacities.</p><p><strong>Conclusions: </strong>Our findings demonstrate a novel role of ADAR1 as an active regulator for LCSCs properties via editing GLI1 in the highly heterogeneous HCC.</p>