APCDD1 and hepatocellular carcinoma: Then the transcriptomic and clinical data of patients in the TCGA database were analyzed, and six DNA hypermethylation-regulated genes (PDE7B, RORA, OBSCN, APCDD1, SLC22A1, and PNPLA7) with different degrees of underexpression were found to be significantly underexpressed in HCC.