OLIG2 and oligodendroglioma: Neural stem cells (Nestin+, SOX2+) are considered as possible cell progenitors of glioblastoma, oligodendroglioma, and astrocytoma, while oligodendrocyte progenitor cells (Olig2+, PDGFRα+) give rise glioblastoma and oligodendroglioma, and astrocytes (GFAP+) are possible progenitors of glioblastoma and astrocytoma.