title: Down-regulation of DLX3 expression in MLL-AF4 childhood lymphoblastic leukemias is mediated by promoter region hypermethylation.
abstract: Hypermethylation of CpG islands is the most well defined epigenetic change in neoplasia and plays an important role in the inactivation or silencing of cancer related genes. DLX genes (1-7), with large CpG islands in their 5' region, are implicated in a number of processes among which haematopoiesis. They are characterized by highly dynamic spatio-temporal expression and supposed to be involved in resistance to apoptosis of several tumor cell lines. In acute lymphoblastic leukemia (ALL) hypermethylation is a common phenomenon frequently associated with poor prognosis in specific genetic childhood leukemia subgroups. These data together with the presence of large CpG islands in the up-stream regions of the DLX genes make them attractive candidates for methylation regulated gene expression and leukemia related aberrancies. To validate the role of DLX genes in paediatric B-ALL cells, we studied two cell lines and two groups of patients with paediatric chromosomal rearrangements: MLL-AF4 and TEL-AML1, respectively. Analysis of methylation and gene expression patterns of DLX3 in 64 specimens of B-lineage ALL revealed that DLX3 presents aberrant methylation in paediatric B-ALL patients. In vitro experiments with 5-Aza-2'dC on leukemia cell lines, confirmed by Western blot analysis, indicated that the methylation of DLX3 CpG islands has a functional role and interferes with the DLX3 gene and DLX3 protein expression in B-ALL cells. Importantly, hypermethylation of DLX3 significantly reduces its expression in MLL-AF4 rearranged leukemias while methylation is almost absent in TEL-AML1 positive ALL specimens. These results show that differential DLX3 methylation could be a new epigenetic marker for genotypic B-cell leukemia subgroup with high-risk features.
authors.affiliation: Department of Paediatrics, University of Padova, I-35128 Padova, Italy.
authors.forename: Marta
authors.initials: M
authors.lastname: Campo Dell'Orto
authors.forename: Barbara
authors.initials: B
authors.lastname: Banelli
authors.forename: Emanuela
authors.initials: E
authors.lastname: Giarin
authors.forename: Benedetta
authors.initials: B
authors.lastname: Accordi
authors.forename: Luca
authors.initials: L
authors.lastname: Trentin
authors.forename: Massimo
authors.initials: M
authors.lastname: Romani
authors.forename: Geertruy
authors.initials: G
authors.lastname: te Kronnie
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Basso
mesh_terms: D015153:Blotting, Western; D002051:Burkitt Lymphoma / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D045744:Cell Line, Tumor; D002648:Child; D019175:DNA Methylation; D015536:Down-Regulation; D015972:Gene Expression Regulation, Neoplastic; D018922:HL-60 Cells; D018398:Homeodomain Proteins / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D051788:Myeloid-Lymphoid Leukemia Protein / Q000235:genetics*; D015514:Oncogene Proteins, Fusion / Q000235:genetics*; D011401:Promoter Regions, Genetic / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism; D020298:U937 Cells
chemical_list: C088334:Distal-less homeobox proteins; D018398:Homeodomain Proteins; C113855:MLL-AF4 fusion protein, human; D015514:Oncogene Proteins, Fusion; D014157:Transcription Factors; D051788:Myeloid-Lymphoid Leukemia Protein