Disruptor of telomeric silencing 1-like (DOT1L), a histone methyltransferase specific for the lysine 79 residue of histone H3 (H3K79), was recently reported to promote the development of mixed lineage leukemia (MLL)-rearranged leukemia and the proliferation and metastasis of BC [2,16,17,18,19]. Here, DOT1L is linked to breast cancer.