To investigate whether HOXA activation in AML patients coincides with activation of the LMO2 +1 enhancer, we performed chromatin immunoprecipitation (ChIP)-on-chip analysis in AML patients that expressed high levels of LMO2. Acetylation of lysine 9 of histone 3 (H3K9) is a histone mark associated with an open chromatin conformation and is generally observed at promoters and enhancers of active genes. The gene discussed is LMO2; the disease is acute myeloid leukemia.