To determine the role of methylation on TES expression in ALL we used microarrays to compare expression in a separate cohort of paediatric precursor B ALL specimens with two control precursor cell populations, normal bone marrow CD34+ progenitor cells (n = 5) and umbilical cord blood CD19+IgM- (pre-B) cells (n = 3). Here, CD34 is linked to acute lymphoblastic leukemia.