Most studied are ADAR, quaking (QKI), FUS, HNRNPL and DHX9, which regulate some but not all circRNAs.10, 16, 17, 18, 19 Interestingly, QKI has recently been shown to be a novel tumor suppressor in lung cancer and to be associated with prognosis,20, 21 and DHX9 has been suggested as a potential therapeutic target in several malignancies.22 A summary of circRNA biogenesis mechanisms is provided in Figure 1. This evidence concerns the gene DHX9 and lung cancer.