OLIG2 and central nervous system cancer: In glioma, where HIF2α is now considered as a marker of CSC (44), acidic conditions were documented to increase both the expression of a panel of glioma stem cells (GSC)-associated genes, including POU5F1 (OCT4), OLIG2, and NANOG, independently of a restricted O2 availability (34), and the fraction of cells positive for the GSC markers CD133 and CD15 (33).