Suppression of the let-7b microRNA pathway by DNA hypermethylation in infant acute lymphoblastic leukemia with MLL gene rearrangements

Leukemia. 2013 Feb;27(2):389-97. doi: 10.1038/leu.2012.242. Epub 2012 Aug 24.


MicroRNAs (miRNAs) regulate cell proliferation and differentiation by controlling the expression of proteins involved in many signaling pathways. Recent studies have shown that dysregulation of miRNA expression is associated with increased tumorigenicity and a poor prognosis in several types of cancers. The miRNA let-7b is one of the severely downregulated miRNAs in mixed-lineage leukemia (MLL)-rearranged acute lymphoblastic leukemia (ALL) patients. In vitro transfection of leukemogenic MLL fusion genes into human embryonic kidney-293 cells suppressed let-7b expression. In leukemic cells with an MLL fusion gene, the regulatory region for let-7b expression was hypermethylated, and its expression was partially recovered after culturing the cells with the demethylating agent 5-azacitidine. These results suggest that loss of let-7b expression may be one of the consequences of oncogenic MLL fusion proteins, and contributes to leukemogenesis possibly through the upregulation of let-7b-regulated target genes with leukemogenic potential in hematopoietic cells. The enforced expression of let-7b in ALL cell lines with an MLL fusion gene inhibited their growth, indicating the possible use of let-7b as a new therapeutic tool for refractory infant ALL with an MLL fusion gene.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antimetabolites, Antineoplastic / pharmacology
  • Azacitidine / pharmacology
  • Base Sequence
  • Cell Proliferation
  • DNA Methylation*
  • Gene Expression Regulation, Leukemic*
  • Gene Rearrangement*
  • Histone-Lysine N-Methyltransferase
  • Humans
  • Infant
  • MicroRNAs / genetics*
  • Molecular Sequence Data
  • Myeloid-Lymphoid Leukemia Protein / genetics*
  • Oncogene Proteins, Fusion / genetics
  • Precursor Cell Lymphoblastic Leukemia-Lymphoma / genetics*
  • Precursor Cell Lymphoblastic Leukemia-Lymphoma / pathology
  • Promoter Regions, Genetic / genetics
  • RNA, Messenger / genetics
  • Real-Time Polymerase Chain Reaction
  • Reverse Transcriptase Polymerase Chain Reaction
  • Tumor Cells, Cultured


  • Antimetabolites, Antineoplastic
  • KMT2A protein, human
  • MicroRNAs
  • Oncogene Proteins, Fusion
  • RNA, Messenger
  • mirnlet7 microRNA, human
  • Myeloid-Lymphoid Leukemia Protein
  • Histone-Lysine N-Methyltransferase
  • Azacitidine