TCF21 and hepatocellular carcinoma: Mechanistic analysis revealed that circMEMO1 can promote the demethylation process of the TCF21 promoter, which is very frequently hypermethylated in HCC tissues, and then promote the transcriptional activation and expression of TCF21 by acting as a sponge for miR-106b-5p, which targets TET family genes and increases the 5hmC level.