MicroRNAs mark in the MLL-rearranged leukemia.

MicroRNAs are short noncoding RNAs, known regulators of several signaling pathways cell differentiation and proliferation, development, and apoptosis, which are deregulated in acute leukemia. Mixed lineage leukemia (MLL) gene encodes a protein with histone methyltransferase activity, which is essential for the fine tuning of hematopoietic stem cell development and differentiation through the regulation of HOXA and MEIS1. MLL gene rearrangements characterize both acute myeloid and acute lymphoblastic leukemia associated with poor outcomes. MicroRNAs and MLL rearrangements are in tight association regulating each other expression, affecting cell cycle regulators, and composing complex networks with factors involved in leukemogenesis such as MYC and FLT3. MLL fusion genes are also capable of recruiting DNA methyltransferases at microRNAs promoters controlling their expression through epigenetic changes. Direct drug targeting of MLL has been difficult to achieve, and in this context, microRNA expression modulation represents an attractive approach.