TET1 was the first identified member of TET family, acting as a fusion partner of MLL gene in acute myeloid leukemia patients bearing the t(10;11)(q22;q23) translocation, and TET2 and TET3 were subsequently identified based on their significant sequence homology to TET1. 21,22 The biological function of TET family was unclear until two landmark discoveries by Kriaucionis et al. 23 and Tahiliani et al. 7. This evidence concerns the gene TET1 and acute myeloid leukemia.