TET1 and acute myeloid leukemia: Subsequently, some AML patients were found to have an MLL-TET1 fusion gene, including the carboxyl terminus of TET1 (containing the 2-OG-Fe2+ oxidase structural domain) and the amino terminus of mixed lineage leukaemia (MLL) (containing the CXXC structural domain) [39], playing an important oncogenic role by activating homeobox gene expression.