Variable hypermethylation of individual p15 alleles is reduced by repeated courses of decitabine.

Analysis of p15 (5′ region, A-D) and p16(exon 2, E) methylation status was determined by sequencing of individual alleles subcloned from bisulfite-treated, PCR-amplified DNA. Normal peripheral blood cells of 2 healthy individuals (A) and bone marrow MNCs from MDS patients 013 (B), 016 (C), and 019 (D,E) were analyzed. Each row represents a single cloned allele. ○, nonmethylated CpG; ●, methylated CpG. Numbering of nucleotides is according to published sequences. Count of methylated CpGs is given for each clone. Bone marrow aspirates for evaluation of hematologic and cytogenetic response were performed between 5 and 8 weeks (median, 6 weeks) after a treatment course. Percent of abnormal metaphases are given on the right. Metaphase cytogenetics were performed as described elsewhere.13 *Cytogenetics were performed on a second aspirate done 47 days later. nm, no metaphases obtained due to lack of dividing cells.