As the only known histone methyltransferase, which targets the histone H3K79, Dot1l adds methyl groups on histone H3K79 and generate mono- (H3K79me), di- (H3K79me2) and tri-methylation (H3K79me3).Up to now, several mechanisms have been summarized to explain the effect of Dot1l on tumor genesis and development. Here, DOT1L is linked to neoplasm.