Fig. 1

Expression of PBK in different GIC cultures. a Expression of PBK gene in NFCs and seven different GIC cultures. Box plot shows significantly increased expression levels of PBK in GIC cultures. Relative expression of PBK was calculated using normal NSCs from the adult human brain as a reference (Relative expression of PBK in NSCs = 1, not shown). Relative expression of PBK was not significantly increased in NFCs (p = 0.057). b Expression of PBK gene in GBM tissue samples from TCGA. PBK was significantly up-regulated in proneural and down-regulated in mesenchymal subtypes of GBM. PBK expression in different subtypes was performed using the classical subtype as a reference. Common for A and B: The bottom and top of each box in box and whisker plots indicate the 25th and 75th percentile (the lower and upper quartiles, respectively), and the band near the middle of the box represents the 50th percentile (the median) (c-h) Immunostaining of cryosections of GIC spheres (T65 and T08) shows expression of PBK (red) and its cellular co-localization with Hoechst (blue). Scale bar = 20 μm. i, j Immunolabeling of a GBM tissue with PBK antibody shows its extensive presence in the GBM tissue compared to the normal cortex brain tissue. Scale bar = 20 μm. k Western blot analysis done on seven GIC cultures shows a clear upregulation of PBK as compared to that in the two normal NSC cultures. ACTB was used as a control. l Kaplan-Meier graph showing patient survival in mesenchymal subtype of GBM (TCGA). The survival times of GBM patients with highest (30 %) and lowest (30 %) expression of PBK were compared (p = 0.0046 according to Gehan-Breslow-Wilcoxon test). Increased expression of PBK correlated negatively with patient survival. Asterisks correspond to p values and indicate level of significance: * = (p ≈ 0.01-0.05), ** = (p ≈ 0.001-0.01) and **** = (p < 0.0001)