Progressive De Novo DNA Methylation at the Pa Promotor of the Abl Genein the Bcr-Abl Locus during the Course of Chronic Myelogenous Leukemia.
- Author:
Sung Eun YANG
1
;
Hyun Sook CHI
Author Information
1. Department of Clinical Pathology, University of Ulsan College of Medicine and Asan Medical Center, Seoul, Korea.
- Publication Type:Original Article
- Keywords:
DNA methylation;
Pa promotor;
bcr-abl hybrid gene;
abl gene;
Chronic myelogenous leukemia;
Methylation-sensitive restriction enzymes;
Polymerase chain reaction
- MeSH:
Alleles;
Blast Crisis;
Bone Marrow;
Cell Line;
CpG Islands;
Diagnosis;
Disease Progression;
DNA Methylation*;
DNA*;
Genes, abl;
Humans;
Leukemia, Myelogenous, Chronic, BCR-ABL Positive*;
Lymphocytes;
Methylation;
Philadelphia Chromosome;
Polymerase Chain Reaction;
RNA, Messenger
- From:Korean Journal of Clinical Pathology
1998;18(3):480-486
- CountryRepublic of Korea
- Language:Korean
-
Abstract:
BACKGROUND: In most cases of chronic myelogenous leukemia (CML), one of the two abl promotors (Pa) is nested within the bcr-abl hybrid gene and should be able to transcribe the 6-kb normal abl mRNA from the Philadelphia chromosome. However, 6-kb transcript is present only in CML cell lines containing a normal abl allele. Since the nested Pa in the bcr-abl hybrid gene is contained within a CpG island, de novo methylation of Pa CpG islands may cause silencing of the c-abl gene. In this study, using a polymerase chain reaction (PCR) and methylation-sensitive restriction enzymes, we investigated the methylation status of the nested Pa CpG islands in the bcr-abl hybrid gene at two stages of CML and the usefulness of it as a disease progression marker. METHODS: Genomic DNA was extracted from the preserved bone marrow smear slides of ten CML patients, at chronic phase and blast crisis respectively. K-562 cell line and normal peripheral lymphocytes as a negative control were also used. The extracted genomic DNA was digested with methylation-sensitive restriction enzymes and methylation-insensitive restriction enzymes, respectively, followed by PCR amplification for Pa promotor and electrophoresed for detection of 171 bp PCR products. RESULTS: The patients were transformed from chronic phase to blast crisis during 11-60 months after initial diagnosis. The patients displayed the following three types of methylation patterns. A, no methylation; B, partial methylation; C, complete methylation. All cases of chronic phase showed pattern A, but three cases of blast crisis were pattern B and seven cases, pattern C. CONCLUSIONS: De novo DNA Methylation at the Pa promotor of the abl gene in the bcr-abl hybrid gene is a distinct and common molecular event in blast crisis of CML. Since the process of Pa CpG methylation is of a progressive nature, Pa methylation pattern may be used as a molecular marker for progression of CML to blast crisis.
