CTH and hepatocellular carcinoma: To determine whether promoter DNA hypermethylation results in CTH gene silencing in FOXC-overexpressing HCC cells, the methylation status of CpG island in the CTH promoter was analyzed by bisulfite genome sequencing (BGS) analysis, which covered 13 CpG sites from − 206 to − 20 of the CTH promoter (Fig. 2a).