BMI1 and acute lymphoblastic leukemia: We observed a significantly positive correlation between Bmi-1 expression and Sall4a (Fig. 4a, 2-tailed Spearman’s correlation, r = 0.2707; P = 0.0122); however, there was no statistical correlation between the Sall4b and Bmi-1 expression levels in the ALL samples examined (Fig. 4b, 2-tailed Spearman’s correlation, r = 0.09686; P = 0.3778).