In the current study, likewise, decreased endogenous TET1 expression was verified in the SMMC 7721 cells, and so TET1-CD was transiently transfected into the SMMC 7721 cells to activate endogenous TET1 gene, in which its promoter CpG islands is likely hypermethylated [25], to treat endogenous TET1 deficiency, suppress proliferation, migration and invasion of the HCC cells, and promote its apoptosis. This evidence concerns the gene TET1 and hepatocellular carcinoma.