These GSC are characterized by their ability to self-renewin vitro (neurospheres (NS) formation) and in vivo, their higherexpression of neural stem cell (NSC) markers (i.e., Olig2, Nestin or A2B5) and stem celltranscription factors (SCTF, i.e., Sox2, Nanog, Gli1 or Oct4), their pluripotentaptitude to differentiate into neurons, astrocytes or oligodendrocytes and their hightumorigenic potential in vivo in mice.3,4 In addition, the presence of these GSC mayexplain the high GBM recurrence rate, as they were shown to be extremely tumorigenic andradioresistant.3, 5, 6. This evidence concerns the gene POU5F1 and glioblastoma.