ADAR and neoplasm: Unbalanced A-to-I editing by ADAR1 was identified to be a tumor promoter in various tissues.26 In particular, the abnormal expression of ADAR1 promoted HCC development.18, 27 By analyzing the TCGA database (http://cancergenome.nih.gov/), we confirmed that ADAR1 was elevated in HCC tumor tissues compared with adjacent normal tissues (Figure 3a).