Tet1 was firstly found in acute myeloid leukemia (AML)3, the further study in ESCs showed Tet1 as a specific DNA demethylase for active DNA demethylation, could act as oxidant and turn the fifth position of cytosine (5mC) to 5-Hydroxymethylcytosine (5hmC) and the subsequent derivatives 5-formylcytosine (5fC) and 5-carboxylcytosine (5caC)4. Here, TET1 is linked to acute myeloid leukemia.