High BRE expression correlated strongly with FAB M5 morphology and MLL-AF9 rearrangements. (A) Gene expression profiling showed that high BRE expression, as represented by the probe set intensity of 212645_x_at, occurred in 14 of 525 AML patients, accounting for 3% of the cohort. Donor CD34⁺ and normal BM cells do not show high BRE expression. (B) High BRE expression correlated with FAB M5. BRE expression is visualized per FAB morphology class. (C) High BRE expression co-occurred with the presence of the MLL-AF9 fusion. BRE expression is represented by the fluorescent intensity of probe set 212645_x_at. Other probe sets representing BRE (205550_s_at and 211566_x_at) showed comparable results (data not shown). The mean per subclass is represented by a horizontal line. Dotted lines represent the mean of all AML samples plus 3 or 4× the SD of BRE expression, used as values for outlier analysis and cutoff for high BRE expression, assigning 14 or 12 samples with high expression, respectively.