Detection of methylated ABL1 promoter in philadelphia-negative myeloproliferative disorders

• Published in: Blood cells, molecules, & diseases Vol. 30; no. 1; pp. 100 - 106
• Main Authors: Aviram, Adina, Witenberg, Bruria, Shaklai, Mati, Blickstein, Dorit
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 2003
• Subjects: ABL1 promoter; Alleles; BCR-ABL; CpG Islands - genetics; DNA - genetics; DNA - metabolism; DNA Methylation; Essential thrombocythemia; Follow-Up Studies; Fusion Proteins, bcr-abl - genetics; Genes, abl - genetics; Humans; Idiopathic myelofibrosis; Methylation; Myeloproliferative disorders; Myeloproliferative Disorders - genetics; Myeloproliferative Disorders - pathology; Philadelphia Chromosome; Polycythemia vera; Polymerase Chain Reaction - methods; Promoter Regions, Genetic; Restriction Mapping - methods; Sensitivity and Specificity; Idiopathic myelofibrosis; Essential thrombocythemia; ABL1 promoter; BCR-ABL; Polycythemia vera; Methylation; Myeloproliferative disorders
• ISSN: 1079-9796; 1096-0961
• DOI: 10.1016/S1079-9796(03)00015-9

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.