title: Hypomethylation status of CpG sites at the promoter region and overexpression of the human MDR1 gene in acute myeloid leukemias.
abstract: Selection of human cells for resistance to vincristine or doxorubicin often induces overexpression of the multidrug resistance 1 gene (MDR1), which encodes the cell surface P-glycoprotein, as a result of gene amplification or transcriptional activation. Moreover, overexpression of the MDR1 gene has been shown to be associated closely with clinical outcome in various hematological malignancies, including acute myeloid leukemia (AML). However, the precise mechanism underlying overexpression of the MDR1 gene during acquisition of drug resistance remains unclear. We recently described an inverse correlation between the methylation status of CpG sites at the promoter region and expression of the MDR1 gene in malignant cell lines. In this study, we expanded this analysis to 42 clinical AML samples. We adapted a quantitative reverse transcription-polymerase chain reaction (RT-PCR) assay for gene expression and a quantitative PCR after digestion by Hpa II for methylation status of the MDR1 gene. We observed a statistically significant inverse correlation between methylation and MDR1 expression in clinical samples. The hypomethylation status of the MDR1 promoter region might be a necessary condition for MDR1 gene overexpression and establishment of P-glycoprotein-mediated multidrug resistance in AML patients.
authors.affiliation: Department of Biochemistry, Kyushu University School of Medicine, Fukuoka, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Nakayama
authors.forename: M
authors.initials: M
authors.lastname: Wada
authors.forename: T
authors.initials: T
authors.lastname: Harada
authors.forename: J
authors.initials: J
authors.lastname: Nagayama
authors.forename: H
authors.initials: H
authors.lastname: Kusaba
authors.forename: K
authors.initials: K
authors.lastname: Ohshima
authors.forename: M
authors.initials: M
authors.lastname: Kozuru
authors.forename: H
authors.initials: H
authors.lastname: Komatsu
authors.forename: R
authors.initials: R
authors.lastname: Ueda
authors.forename: M
authors.initials: M
authors.lastname: Kuwano
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000235:genetics*; D000208:Acute Disease; D000328:Adult; D000368:Aged; D019175:DNA Methylation; D018432:Drug Resistance, Multiple / Q000235:genetics*; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007951:Leukemia, Myeloid / Q000235:genetics*; D008297:Male; D008875:Middle Aged; D011401:Promoter Regions, Genetic / Q000235:genetics*
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1