title: Epigenetic inactivation of DAPK1, p14ARF, mir-34a and -34b/c in acute promyelocytic leukaemia.
abstract: OBJECTIVE
  TP53 mutation frequently occurs in solid cancers but not haematological cancers including acute promyelocytic leukaemia (APL) characterised by t(15;17). Both DAPK1 and p14(ARF) positively regulate p53 whereas miR-34a and -34b/c are direct transcriptional targets of p53. We studied if DNA methylation might contribute to inactivation of gene/microRNA (miRNA) in the TP53 tumour suppressor network.
  
  
  METHODS
  Promoter methylation of DAPK1, p14(ARF), miR-34a and -34b/c were studied in 10 normal bone marrow samples, NB4 cell line and 60 APL primary samples at diagnosis by methylation-specific PCR (MSP).
  
  
  RESULTS
  DAPK1, p14(ARF), miR-34a and -34b/c were completely unmethylated in normal bone marrow samples. DAPK1, miR-34a and -34b/c were completely methylated in NB4. Treatment of NB4 by 5'-Aza-2'-deoxyctidine resulted in promoter demethylation together with re-expression of DAPK1 and both miRNAs. In primary APL samples, methylation of miR-34b/c was detected in 43% in contrast to absence of methylation of DAPK1, p14(ARF) or miR-34a. Overexpression of miR-34b in NB4 resulted in inhibition of proliferation.
  
  
  CONCLUSIONS
  Methylation of DAPK1, miR-34a and -34b/c is tumour-specific, and associated with gene/miRNAs silencing. miR-34b/c is a tumour suppressor miRNA in APL. Methylation of miR-34b/c may contribute to APL leukaemogenesis.
authors.affiliation: Department of Medicine, Queen Mary Hospital, University of Hong Kong, Hong Kong.
authors.forename: Ho Yin
authors.initials: HY
authors.lastname: Ng
authors.affiliation: Department of Pathology, Queen Mary Hospital, University of Hong Kong, Hong Kong.
authors.forename: Thomas S
authors.initials: TS
authors.lastname: Wan
authors.affiliation: Department of Pathology, Queen Mary Hospital, University of Hong Kong, Hong Kong.
authors.forename: Chi Chiu
authors.initials: CC
authors.lastname: So
authors.affiliation: Department of Medicine, Queen Mary Hospital, University of Hong Kong, Hong Kong.
authors.forename: Chor Sang
authors.initials: CS
authors.lastname: Chim
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D014408:Biomarkers, Tumor / Q000235:genetics* / Q000378:metabolism; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D002648:Child; D019175:DNA Methylation; D064550:Death-Associated Protein Kinases / Q000235:genetics*; D005260:Female; D020868:Gene Silencing; D020022:Genetic Predisposition to Disease; D006801:Humans; D053208:Kaplan-Meier Estimate; D015473:Leukemia, Promyelocytic, Acute / Q000235:genetics* / Q000378:metabolism / Q000401:mortality / Q000473:pathology; D008297:Male; D035683:MicroRNAs / Q000235:genetics* / Q000378:metabolism; D008875:Middle Aged; D010641:Phenotype; D016133:Polymerase Chain Reaction; D011401:Promoter Regions, Genetic; D013997:Time Factors; D014162:Transfection; D025803:Tumor Suppressor Protein p14ARF / Q000235:genetics*; D055815:Young Adult
chemical_list: D014408:Biomarkers, Tumor; C522425:MIRN34 microRNA, human; D035683:MicroRNAs; D025803:Tumor Suppressor Protein p14ARF; C579096:DAPK1 protein, human; D064550:Death-Associated Protein Kinases
keywords: CANCER GENETICS; DNA; HAEMATO-ONCOLOGY