Patients undergo bone marrow aspiration and blood sample collection periodically for pharmacological and correlative studies. Samples are analyzed for gene expression, methylation of gene promoters, fetal hemoglobin (HgF), DNMT1 protein expression, maximum concentration of plasma decitabine, and global DNA methylation. Samples are analyzed by RT-PCR, Bio-COBRA, matrix-assisted laser desorption ionization time-of-flight mass spectrometry, SDS-PAGE (polyacrylamide gel electrophoresis), immunoblotting, and LC-MS/MS.