Surprisingly, we found that RASSF1–5 were infrequently methylated whilst RASSF6 was methylated in B-ALL (94%; 48/51), T-ALL (41%; 12/29) and 5/5 unclassified childhood leukaemias but not in normal blood or bone marrow control samples (0/8 and 0/1 respectively; figure 1A, B, table 1 and Additional file 1; figure S1–2). Here, RASSF1 is linked to acute lymphoblastic leukemia.