Since the Polycomb group gene Bmi1 is involved in the regulation of development and tumorigenesis, the effect of Bmi1 downregulation in GBM cells was screened by analysis of proteins involved in key cellular pathways of the cell cycle, development, metabolism, apoptosis and growth, including Erk, Akt, GSK3β, p16 and p14, Bcl-2, c-Myc, Nestin and Sox2. This evidence concerns the gene GSK3B and glioblastoma.