CD34 and precursor B-cell acute lymphoblastic leukemia: However, in 86% of precursor B-cell acute lymphocytic leukemia (pre-B-ALL),100% of T-cell acute lymphocytic leukemia (T-ALL) cell lines and primary samples (18 of 21 and 11 of 11 samples respectively) and 42% of acute myeloid leukemia (AML) cell lines and primary samples (8 of 19 samples), miR-27a was expressed at levels ≥2 fold lower than in CD34+ cells (Figure 1A–C).