(a) Representative images of glioblastoma tissue microarray samples (n = 96) showing the expression of EZH2, BMI1, CD44, and OLIG2. Scale bar, 500 μm. (b) Kaplan-Meier curve of patient survival stratified by EZH2 and BMI1 protein expression level from a glioblastoma tissue microarray. Log-rank p-values were used to determine statistics significance. (c) Cell lysates were prepared from neural progenitor cells (NPC1, NPC2, and NPC3), proneural GSCs 670 (PN11, PN23, PN1919, and PN3691), and mesenchymal GSCs (MES20, MES3565, MES28, MES738). Protein was resolved by SDS-PAGE. Immunoblot for performed for BMI1, H2K119Ub, EZH2, H3K27me3, and markers for mesenchymal (CD44 and YKL40) and proneural (OLIG2 and SOX2) glioblastoma. (d) Immunoprecipitation followed by immunoblot was performed for BMI1 polyubiquitination in PN1919 and MES28 cells in presence or absence of lactacystin treatment for 5 hours (Lacta, 10 μM). Right panel: quantification of BMI1 polyubiquitination by Image J. Data normalized by input loading controls. (e) Rank-ordered list of correlation coefficients (r values) between ubiquitin ligases and BMI1 activation or inhibition signatures in TCGA glioblastoma samples. (f) BMI1 polyubiquitination by RNF144A in PN1919 cells after transduction with shRNA control (shCTRL) or shRNF144A (shRNF144A-1099 and shRNF144A-3112) was examined by immunoprecipitation of BMI1 followed by immunoblotting for BMI1 or ubiquitin in presence or absence of lactacystin treatment for 5 hours (Lacta, 10 μM). Levels of BMI1, RNF144A, and TUBULIN were measured by immunoblot in the input whole cell lysates. (g) Neural progenitor cells (NPC1), proneural GSCs (PN1919 and PN3691), and mesenchymal GSCs (MES20 and MES28) were grown under baseline, low-glucose, hypoxia, or combined conditions. Levels of RNF144A, BMI1, EZH2, CD44, YKL40, OLIG2, and SOX2 proteins were measured by immunoblot. (h) Cell viability of neural progenitor cells (NPC1), proneural GSCs (PN11, PN23, PN1919, and PN3691), and mesenchymal GSCs (MES20, MES28, MES3565, and MES738) were determined under baseline, low-glucose, hypoxia, or combined conditions. Data are presented as mean ± SEM. *, p < 0.05; by Wilcoxon and Mann-Whitney t-test.