Validation of MeDIP assay using in vitro methylated DNA. DNA samples from the human cell line SilALL were methylated in vitro (+ M.SssI) or not, and subjected to MeDIP assay. Relative enrichment at normally methylated (PCDHGA12 and RPIB9) or unmethylated (ACTB and GAPDH) gene promoters was analyzed by real-time quantitative PCR. Both the PCDHGA12 and RPIB9 gene promoters were previously found to be commonly methylated in T-ALLs and derived cell lines . Results shown represent the mean values of triplicate PCRs; and are representative of three independent experiments.