OPN1SW and acute lymphoblastic leukemia: Next, we performed chromatin immunoprecipitation followed by sequencing (ChIP-seq) to evaluate the genome-wide distribution of H3K27 acetylation (H3K27ac), a histone mark indicative for active promoters and/or putative enhancer regions, in an ETV6/RUNX1-positive (REH) and negative (697) BCP-ALL cell line.