EPAS1 and cancer: For each cell type (parental U87, U87-CSC, or brain tumor isolated CSCs) and conditioned medium type, the migration rate was reduced after HIF-2α silencing, but again the magnitude of the effect was greater for CSCs compared to parental U87s and was statistically significant only when the medium was conditioned by the M2 macrophages, which are associated with the promotion of malignant phenotypes in cancer cells.