TET1 and TET2 are involved in tumorigenesis; TET1 is a fusion partner of the mixed lineage leukemia protein in acute myeloid leukemia and acute lymphoblastic leukemia, and loss-of-function mutations in the TET2 gene are frequently observed in acute myeloid leukemia (AML), as well as a variety of myelodysplastic syndromes and myeloproliferative disorders [12]. The gene discussed is TET1; the disease is acute lymphoblastic leukemia.