Both TET1 and TET2 are implicated in cancer: TET1 is an MLL partner in cases of acute myeloid and lymphoid leukemias (124) and has been reported to function as an oncogene in MLL-rearranged leukemias (125) as well as a tumor suppressor in other contexts [reviewed in Ref. The gene discussed is KMT2A; the disease is lymphoid leukemia.