There has been much focus on DNA mutations in tumorigenesis and tumor progression, but now a new study highlights a role for post-transcriptional changes in RNA in cancer. The authors show increased RNA editing of antizyme inhibitor 1 (AZIN1) in tumor tissues from patients with hepatocellular carcinoma and characterize a mechanism through which the expression of edited AZIN1 protein leads to increased cell proliferation (pages 209–216).