Detection of methylated ABL1 promoter in philadelphia-negative myeloproliferative disorders.
Aberrant methylation of tumor-suppressor gene promoter regions may play a causal role in the pre-neoplastic stage of cancer progression. In chronic myeloid leukemia, changes in the methylation status of the CpG-rich islands at several sites in the proximal ABL1 promoter (Pa) on the Philadelphia (Ph)-chromosome have been observed. It remains unclear if the Pa methylation precedes the translocation event (t9;22) that generates the Ph-chromosome or if Pa methylation is a stochastic event in a progenitor cell which will later acquire other mutations, namely t9;22. The present study was conducted to answer two questions: What is the methylation status of Pa in patients with Ph-negative myeloproliferative disorders (MPD)? Can the study of methylation in patients with Ph-negative MPD shed light on the initial events associated with the translocation? To probe CpG methylation, we used two methodologies; site-methylation-sensitive restriction enzyme assay and methylation-specific PCR analysis following modification of genomic DNA by bisulfite. Results showed that 22 of the 97 patients with Ph-negative MPD expressed BCR-ABL transcripts. Seven of the 97 patients possessed methylated Pa, but only 2 of them expressed BCR-ABL transcripts. In some of the patients, Pa methylation was a dynamic event. In conclusion, aberrant methylation in Ph-negative MPD could be an initial event triggering the occurrence of the t9;22 translocation and its clinical expression. These findings may shed light on the pathogenesis and progression of MPD.
Aviram
Adina
A
Institute of Hematology, Rabin Medical Center, Beilinson Campus and Felsenstein Medical Research Center, Petah Tikva 49100, Israel. adinaav@clalit.org.il
Witenberg
Bruria
B
Shaklai
Mati
M
Blickstein
Dorit
D
D000483:Alleles; D018899:CpG Islands / Q000235:genetics; D004247:DNA / Q000235:genetics / Q000378:metabolism; D019175:DNA Methylation; D005500:Follow-Up Studies; D016044:Fusion Proteins, bcr-abl / Q000235:genetics; D016313:Genes, abl / Q000235:genetics*; D006801:Humans; D009196:Myeloproliferative Disorders / Q000235:genetics* / Q000473:pathology; D010677:Philadelphia Chromosome; D016133:Polymerase Chain Reaction / Q000379:methods; D011401:Promoter Regions, Genetic; D015183:Restriction Mapping / Q000379:methods; D012680:Sensitivity and Specificity
D004247:DNA; D016044:Fusion Proteins, bcr-abl