PLK4 and precursor B-cell acute lymphoblastic leukemia: In summary, our patient samples and the database expression data correlated in regard to Plk1 and Plk4, as the expression was higher in B-ALL patients than in both PBMCs and in CD19+ sorted B-cells from healthy donors but differed in regard to Plk2 and Plk3 as an opposite expression pattern was found in our patients compared to the database set.