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. Here, HIF1A is linked to neoplasm.