TET1 is an MLL partner in cases of acute myeloid (AML) and lymphoid (ALL) leukemias, while loss of function of TET2 is strongly associated with myelodysplastic syndromes, myeloproliferative neoplasms, and myeloid leukemias (Ko et al., 2010). Here, TET1 is linked to acute myeloid leukemia.