Promoter hypermethylation in MLL-r infant acute lymphoblastic leukemia: biology and therapeutic targeting

Blood. 2010 Jun 10;115(23):4798-809. doi: 10.1182/blood-2009-09-243634. Epub 2010 Mar 9.


Cooperating leukemogenic events in MLL-rearranged (MLL-r) infant acute lymphoblastic leukemia (ALL) are largely unknown. We explored the role of promoter CpG island hypermethylation in the biology and therapeutic targeting of MLL-r infant ALL. The HELP (HpaII tiny fragment enrichment by ligation-mediated polymerase chain reaction [PCR]) assay was used to examine genome-wide methylation of a cohort of MLL-r infant leukemia samples (n = 5), other common childhood ALLs (n = 5), and normals (n = 5). Unsupervised analysis showed tight clustering of samples into their known biologic groups, indicating large differences in methylation patterns. Global hypermethylation was seen in the MLL-r cohort compared with both the normals and the others, with ratios of significantly (P < .001) hypermethylated to hypomethylated CpGs of 1.7 and 2.9, respectively. A subset of 7 differentially hypermethylated genes was assayed by quantitative reverse-transcription (qRT)-PCR, confirming relative silencing in 5 of 7. In cell line treatment assays with the DNA methyltransferase inhibitor (DNMTi) decitabine, MLL-r (but not MLL wild-type cell lines) showed dose- and time-dependent cytotoxicity and re-expression of 4 of the 5 silenced genes. Methylation-specific PCR (MSP) confirmed promoter hypermethylation at baseline, and a relative decrease in methylation after treatment. DNMTi may represent a novel molecularly targeted therapy for MLL-r infant ALL.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Azacitidine / analogs & derivatives*
  • Azacitidine / pharmacology
  • Azacitidine / therapeutic use
  • Cell Line, Tumor
  • Child
  • Child, Preschool
  • Cohort Studies
  • CpG Islands*
  • DNA Methylation / drug effects*
  • DNA Methylation / genetics
  • DNA Modification Methylases / antagonists & inhibitors
  • DNA Modification Methylases / metabolism
  • Decitabine
  • Enzyme Inhibitors / pharmacology*
  • Enzyme Inhibitors / therapeutic use
  • Female
  • Gene Rearrangement / drug effects
  • Gene Rearrangement / genetics
  • Gene Silencing / drug effects
  • Genome-Wide Association Study
  • Histone-Lysine N-Methyltransferase
  • Humans
  • Infant
  • Male
  • Myeloid-Lymphoid Leukemia Protein / biosynthesis*
  • Myeloid-Lymphoid Leukemia Protein / genetics
  • Precursor Cell Lymphoblastic Leukemia-Lymphoma / drug therapy*
  • Precursor Cell Lymphoblastic Leukemia-Lymphoma / enzymology
  • Precursor Cell Lymphoblastic Leukemia-Lymphoma / genetics
  • Promoter Regions, Genetic*


  • Enzyme Inhibitors
  • KMT2A protein, human
  • Myeloid-Lymphoid Leukemia Protein
  • Decitabine
  • DNA Modification Methylases
  • Histone-Lysine N-Methyltransferase
  • Azacitidine