ZNF566 and hepatocellular carcinoma: According to the circBase annotation (http://www.circbase.org/), hsa-circ-0109500 (also named hsa-circ-0141434) was the most upregulated circRNA in HCC tissues; hsa-circ-0109500 is spliced from the ZNF566 gene and forms a sense-overlapping circular transcript of 603 nt in length (chr19:36940300-36940903), termed circZNF566, Sanger sequencing confirmed the head-to-tail splicing (Fig. 1b).