POU4F1 and leukemia: Amongst the 54 genes analysed 30 (56%) genes demonstrated frequent methylation (≥ 25%) in primary B or T ALL or both subtypes as well as leukemia cell lines, with the exception of FAT1, DUSP4 and POU4F1 that demonstrated lower methylation frequency in leukemia cell lines compared to primary ALL samples (Table 1).