OLIG2 and neoplasm: GSCs are heterogeneous in origin, are found in the inner core of the tumor mass, express several markers (SOX2, NANOG, BMI1, OLIG2, MUSASHI1, and CD133), and are resistant against chemo- and radiotherapy.216,217 These cells interact with the surrounding microenvironment, regulating multiple signaling networks such as VEGF, NF-kB, EGFR, HIF1α, TGFβ, BMP, and NOTCH for promotion of tumor growth, metastasis and angiogenesis.218 In contrast, GASC are nontumorigenic tumor supporting stem cells originated from mesenchymal stem cells mostly found in the perivascular area.