Relationship between MDR1 gene expression and methylation status of 5′CpG sites at the MDR1 promoter region in AML patients. MDR1 gene expression was determined by quantitative RT-PCR (Fig 2), and the data were from Fig 4. Methylation status was analyzed by quantitative PCR (Fig 6). Criteria for hypomethylation and hypermethylation status were defined as described in Results. Average levels of MDR1 mRNA for each methylation status are indicated.