CHEK1 and precursor B-cell acute lymphoblastic leukemia: Here, in primary leukemic blasts isolated from the bone marrow (BM) or the peripheral blood (PB) of adult B-ALL patients (for patient characteristics see [28]) at diagnosis (n = 39) and relapse (n = 14; not paired samples) we observed that Wee1 and Chek1 transcripts are co-expressed at diagnosis (Pearson r = 0.5770, p = 0.0001) and strongly co-expressed at relapse (Pearson r= 0.8919; p = 0.0001) (Figure 4A).